Aerosol-generating substrate

Abstract

A porous aerosol-generating substrate for an aerosol-generating article, the porous aerosol-generating substrate including: a particulate agent; at least 10 percent by weight of an aerosol former, on a dry weight basis; and at least 1 percent by weight of a binder, on a dry weight basis. The aerosol-generating substrate is formed as a one-piece unit having a length, a width and a thickness. Each of the length, the width and the thickness is at least 1 millimetre. At least one of the length, the width and the thickness is at least 3 millimetres. The particulate agent may include a particulate plant material. The aerosol-generating substrate may include an active agent and / or a flavourant and the particulate agent may include a particulate cellulose strengthening agent.

Description

[0001] AEROSOL-GENERATING SUBSTRATE

[0002] The present invention relates to an aerosol-generating substrate. More particularly, the present invention relates to a porous aerosol-generating substrate. The present invention also relates to an aerosol-generating article comprising the porous aerosol-generating substrate. The present invention also relates to an aerosol-generating system comprising an aerosol-generating device, for example an aerosol-generating device comprising a heating element, for example a dielectric or microwave heating element, and an aerosol-generating article comprising the porous aerosol-generating substrate. The present invention also relates to a method of manufacturing the porous aerosol-generating substrate.

[0003] A typical aerosol-generating system comprises an aerosol-generating device and an aerosol-generating article comprising an aerosol-generating substrate. In use, the aerosolgenerating device is arranged to heat a heating element that is positioned near, or in contact with, the aerosol-generating substrate which causes the aerosol-generating substrate to heat up and release volatile compounds. These volatile compounds are then entrained in air that is drawn through the aerosol-generating article. As the volatile compounds cool, they condense to form an aerosol that can be inhaled by a consumer.

[0004] A typical aerosol-generating article may appear similar and have similar dimensions to a conventional cigarette. For example, such an aerosol-generating article may be substantially cylindrical and comprise an aerosol-generating substrate in addition to other components such as mouthpiece filter element and a cooling element, which are arranged in the form of a rod and wrapped in a cigarette paper.

[0005] However, a significant portion of the aerosol-generating substrate in these cylindrical aerosol-generating articles may not be sufficiently heated to form an aerosol during use. This is undesirable since the insufficiently heated portion of the aerosol-generating substrate contributes to the cost of manufacture and transport of the aerosol-generating article but does not contribute to the aerosol delivered to the consumer. Moreover, the components of these cylindrical aerosolgenerating articles normally need to have the same or very similar outer diameters so that they can be brought together, accurately positioned in axial alignment and wrapped in a cigarette paper. This can lead to increased cost and complexity of manufacture.

[0006] Substantially planar aerosol-generating articles having a thickness that is less than 50 percent of both a length and a width of the aerosol-generating article have been designed. Advantageously, a smaller thickness provides a small temperature gradient or difference across the thickness of the aerosol-generating substrate during heating. Advantageously, this may allow heating of a greater proportion of the aerosol-generating substrate to a temperature at which an aerosol is released whilst minimising the risk of burning the hottest portion of the aerosol- generating substrate closest to the heater. Advantageously, this may also reduce a time required to heat the aerosol-generating substrate sufficiently to release an aerosol.

[0007] It is an objective of the present disclosure to provide an aerosol-generating substrate that further increases the proportion of the aerosol-generating substrate that is heated to a temperature at which an aerosol is released. It is also an objective of the present disclosure to provide an aerosol-generating article that can be manufactured relatively efficiently and cost effectively.

[0008] According to an aspect of the present invention, there is provided a porous aerosolgenerating substrate for an aerosol-generating article.

[0009] According to an aspect of the present invention, there is provided an aerosol-generating article comprising the porous aerosol-generating substrate as defined below.

[0010] According to an aspect of the present invention, there is provided an aerosol-generating system comprising an aerosol-generating device, for example an aerosol-generating device comprising a heating element, e.g. a dielectric heating element or a microwave heating element, and the aerosol-generating article as defined below.

[0011] According to an aspect of the present invention, there is provided a method of manufacturing a porous aerosol-generating substrate as defined below.

[0012] As used herein, the term “aerosol-generating substrate” refers to a substrate capable of releasing upon heating volatile compounds, which can form an aerosol.

[0013] As used herein, the term “aerosol-generating article” refers to an aerosol-generating article for producing an aerosol comprising an aerosol-generating substrate that is intended to be heated rather than combusted in order to release volatile compounds that can form an aerosol.

[0014] As used herein, the term “aerosol-generating device” refers to a device comprising a heating element that interacts with the aerosol-generating substrate of the aerosol-generating article to generate an aerosol.

[0015] As used herein, “density” or “substrate density” refers to the mass of aerosol-generating substrate material in the volume of the formed aerosol-generating substrate, i.e. the average bulk density of the substrate unit that is cast or otherwise formed for inclusion in an aerosol-generating article.

[0016] The present invention provides a novel and improved aerosol-generating substrate for an aerosol-generating article. The porous aerosol-generating substrate comprises a binder that is mixed with an aerosol former, water and other active ingredients, such as nicotine, tobacco, botanical, etc., which may be used in their shred, leaves or any solid state. Preferably, the tobacco and / or the botanical may be particulate. The mixture is dried using any suitable method, including, but not limited to, for example heating or lyophilisation, and formed into a desirable shape or form. The porous aerosol-generating substrate can advantageously be formed stably into a desired shape and can be used directly in an aerosol-generating article. The aerosol-generating article may be used with, for example inserted into, an aerosol-generating device including a heating element. The aerosol-generating device may be configured to heat the aerosolgenerating substrate within the aerosol-generating article. The aerosol-generating device may be configured to heat the aerosol-generating substrate within the aerosol-generating article by any suitable means. The resulting porous aerosol-generating substrate may be heated, for example, using different heating methods, such as conductive heating, convective heating, induction heating, dielectric or microwave heating, or any combination thereof.

[0017] The ability to form the porous aerosol-generating substrate into any desired shape enables it to be used in a wide variety of different types of aerosol-generating article, since the size and shape of the porous aerosol-generating substrate can be readily adapted to suit the space into which it is incorporated. The porous aerosol-generating substrate therefore offers improved flexibility and versatility. The porous aerosol-generating substrate finds particular application in planar or flat aerosol-generating articles, which offer more efficient heating and generation of aerosol due to the flat structure of the aerosol-generating substrate.

[0018] The provision of an aerosol-generating substrate in the form of porous three-dimensional shapes also advantageously provides a substrate with a high surface area to volume ratio, which optimises the release of aerosol from the substrate upon heating.

[0019] The porous aerosol-generating substrate has, surprisingly, been found to generate comparable amounts of active agents, e.g. nicotine, from a lower mass of substrate, as compared to known aerosol-generating substrates.

[0020] The porous aerosol-generating substrate may be particularly suitable for heating using dielectric heating, also sometimes referred to as electronic heating, radio frequency (RF) heating, high-frequency (HF) heating, or microwave heating. This is a heating method where a dielectric material is subjected to high-frequency electric field or microwave electromagnetic radiation to thereby heat the dielectric material. This heating is caused by molecular dipole rotation of the dielectric material (for example an aerosol-generating substrate that has dielectric properties), caused by the alternating polarization of the dielectric material stimulated by the alternating electric field. This dipole rotation causes the molecules to push, pull, and collide with other molecules, distributing the energy to adjacent molecules of the dielectric material, and thereby causing heating of the material.

[0021] By reducing the average bulk density of the aerosol-generating substrate, there may be a greater surface area available for aerosolisation and a lower resistance-to-draw through the aerosol-generating substrate. In turn, this reduces condensation. Accordingly, because the delivery of aerosol is improved, a lower mass of aerosol-generating substrate is needed. This is particularly synergistic with dielectric heating because there is less need for conduction throughout the aerosol-generating substrate (microwave heating directly heats the whole aerosolgenerating substrate). This is also synergistic with flat or planar consumables for aerosolgenerating articles because the substrate can be positioned closer to the hearing element of the aerosol-generating device, and so there is less need for conduction though the aerosolgenerating substrate.

[0022] The porous aerosol-generating substrate may comprise a particulate plant material and an aerosol former. The porous aerosol-generating substrate may have an aerosol-former content of at least 10 percent by weight, on a dry weight basis. The porous aerosol-generating substrate may comprise a binder. The porous aerosol-generating substrate may have a binder content of at least 1 percent by weight, on a dry weight basis. The porous aerosol-generating substrate may be formed as a one-piece unit having a length, a width and a thickness. Each of the length, the width and the thickness may be at least 1 millimetre. At least one of the length, the width and the thickness may be at least 3 millimetres.

[0023] According to an aspect of the present invention, there is provided a porous aerosolgenerating substrate for an aerosol-generating article, the porous aerosol-generating substrate comprising a particulate plant material and an aerosol former, wherein the aerosol-generating substrate has an aerosol former content of at least 10 percent by weight, on a dry weight basis. The porous aerosol-generating substrate may comprise a binder. The porous aerosol-generating substrate may have a binder content of at least 1 percent by weight, on a dry weight basis. The porous aerosol-generating substrate may be formed as a one-piece unit having a length, a width and a thickness. Each of the length, the width and the thickness may be at least 1 millimetre. At least one of the length, the width and the thickness may be at least 3 millimetres.

[0024] According to an aspect of the present invention, there is provided a porous aerosolgenerating substrate for an aerosol-generating article, the porous aerosol-generating substrate comprising: a particulate plant material; an aerosol former; and a binder; wherein the porous aerosol-generating substrate has an aerosol former content of at least 10 percent by weight, on a dry weight basis and a binder content of at least 1 percent by weight, on a dry weight basis. The porous aerosol-generating substrate may be formed as a one-piece unit having a length, a width and a thickness. Each of the length, the width and the thickness may be at least 1 millimetre. At least one of the length, the width and the thickness may be at least 3 millimetres.

[0025] According to an aspect of the present invention, there is provided a porous aerosolgenerating substrate for an aerosol-generating article, the porous aerosol-generating substrate comprising: a particulate plant material; an aerosol former; and a binder; wherein the aerosolgenerating substrate has an aerosol former content of at least 10 percent by weight, on a dry weight basis, and a binder content of at least 1 percent by weight on a dry weight basis. The porous aerosol-generating substrate is formed as a one-piece unit having a length, a width and a thickness. Each of the length, the width and the thickness is at least 1 millimetre. At least one of the length, the width and the thickness is at least 3 millimetres.

[0026] According to an aspect of the invention, there is provided a method of manufacturing a porous aerosol-generating substrate, as defined above.

[0027] The method may comprise mixing the binder and the aerosol former to form a first slurry; mixing water into the first slurry; adding the particulate plant material; mixing the first slurry and the particulate plant material to form a final slurry; and drying the final slurry.

[0028] The step of forming the porous aerosol-generating substrate may include pouring the final slurry into a mould before drying the final slurry, i.e. casting the porous aerosol-generating substrate. Alternatively, the porous aerosol-generating substrate may be dried and subsequently cut to the required dimensions.

[0029] The drying step may be carried out using any suitable means, including but not limited to heating and lyophilisation (freeze-drying).

[0030] The particulate plant material may comprise tobacco. With reference to the present invention, the term “tobacco” describes any plant member of the genus Nicotiana. The tobacco may comprise tobacco material selected from one or more of: Bright tobacco, dark tobacco, aromatic tobacco and filler tobacco.

[0031] The porous aerosol-generating substrate may have a particulate plant material content of at least 20 percent by weight, for example at least 25 percent by weight, for example at least 30 percent by weight, for example at least 40 percent by weight, for example at least 45 percent by weight, on a dry weight basis.

[0032] The particulate plant material content of the porous aerosol-generating substrate may be less than or equal to 65 percent by weight, for example less than or equal to 60 percent by weight, for example less than or equal to 55 percent by weight, on a dry weight basis.

[0033] The particulate plant material content of the porous aerosol-generating substrate may be between 20 percent by weight and 65 percent by weight, on a dry weight basis, for example between 20 percent by weight and 60 percent by weight, on a dry weight basis, for example between 20 percent by weight and 55 percent by weight, on a dry weight basis.

[0034] The particulate plant material content of the porous aerosol-generating substrate may be between 25 percent by weight and 65 percent by weight, on a dry weight basis, for example between 25 percent by weight and 60 percent by weight, on a dry weight basis, for example between 25 percent by weight and 55 percent by weight, on a dry weight basis.

[0035] The particulate plant material content of the porous aerosol-generating substrate may be between 30 percent by weight and 65 percent by weight, on a dry weight basis, for example between 30 percent by weight and 60 percent by weight, on a dry weight basis, for example between 30 percent by weight and 55 percent by weight, on a dry weight basis.

[0036] The particulate plant material content of the porous aerosol-generating substrate may be between 35 percent by weight and 65 percent by weight, on a dry weight basis, for example between 35 percent by weight and 60 percent by weight, on a dry weight basis, for example between 35 percent by weight and 55 percent by weight, on a dry weight basis.

[0037] The particulate plant material content of the porous aerosol-generating substrate may be between 40 percent by weight and 65 percent by weight, on a dry weight basis, for example between 40 percent by weight and 60 percent by weight, on a dry weight basis, for example between 40 percent by weight and 55 percent by weight, on a dry weight basis.

[0038] The particulate plant material content of the porous aerosol-generating substrate may be between 45 percent by weight and 65 percent by weight, on a dry weight basis, for example between 45 percent by weight and 60 percent by weight, on a dry weight basis, for example between 45 percent by weight and 55 percent by weight, on a dry weight basis.

[0039] The particulate plant material content of the porous aerosol-generating substrate may be between 46 percent by weight and 50 percent by weight, on a dry weight basis, for example between 47 percent by weight and 49 percent by weight, on a dry weight basis.

[0040] Additionally, or alternatively, the particulate plant material may comprise a non-tobacco plant material. The particulate plant material may, for example, comprise tobacco or non-tobacco plant material or a mixture of tobacco and non-tobacco plant material. For example, a proportion of non-tobacco plant material may be added to tobacco material to provide a particular flavour profile. A proportion of tobacco may, for example, be replaced with a non-tobacco plant material.

[0041] The tobacco content may be 100 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis. In other words, the tobacco content of the porous aerosol-generating substrate may be between 20 percent by weight and 60 percent by weight, on a dry weight basis.

[0042] The non-tobacco plant material content may be 100 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis. In other words, the non-tobacco plant content of the porous aerosol-generating substrate may be between 20 percent by weight and 60 percent by weight, on a dry weight basis.

[0043] Alternatively, the tobacco content may be at least 75 percent, for example at least 80 percent, for example at least 85 percent, for example at least 90 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis.

[0044] The tobacco content may be less than or equal to 99 percent, for example less than or equal to 98 percent, for example less than or equal to 95 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis. The tobacco material content may be between 75 percent and 99 percent, for example between 75 percent and 98 percent, for example between 75 percent and 95 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis.

[0045] The tobacco material content may be between 80 percent and 99 percent, for example between 80 percent and 98 percent, for example between 80 percent and 95 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis.

[0046] The tobacco material content may be between 85 percent and 99 percent, for example between 85 percent and 98 percent, for example between 85 percent and 95 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis.

[0047] The tobacco material content may be between 90 percent and 99 percent, for example between 90 percent and 98 percent, for example between 90 percent and 95 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis.

[0048] The non-tobacco plant material content may be at least 1 percent, for example at least 2 percent, for example at least 5 percent, for example at least 10 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis.

[0049] The non-tobacco plant material content may be less than or equal to 25 percent, for example less than or equal to 20 percent, for example less than or equal to 15 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis.

[0050] The non-tobacco plant material content may be between 1 percent and 25 percent, for example between 1 percent and 20 percent, for example between 1 percent and 15 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis.

[0051] The non-tobacco plant material content may be between 2 percent and 25 percent, for example between 2 percent and 20 percent, for example between 2 percent and 15 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis.

[0052] The non-tobacco plant material content may be between 5 percent and 25 percent, for example between 5 percent and 20 percent, for example between 5 percent and 15 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis. The non-tobacco plant material content may be between 10 percent and 25 percent, for example between 10 percent and 20 percent, for example between 10 percent and 15 percent of the particulate plant material content of the porous aerosol-generating substrate, on a dry weight basis.

[0053] The non-tobacco plant material may comprise one or more of: tea (such as black tea), rosehip seeds, apple fibres, lemon balm stems, coffee, star anise, rooibos, lavender, clove, peppermint, chamomile, rosemary, eucalyptus, ginger, dill seed, thyme, oregano and cumin.

[0054] Additionally, or alternatively, the non-tobacco plant material may comprise a cannabinoid compound. The cannabinoid compound may be a naturally derived cannabinoid compound. The cannabinoid compound may be a synthetically derived cannabinoid compound. The cannabinoid compound may comprise one or more of tetrahydrocannabinol (THC), tetrahydrocannabinolic acid (THCA), cannabidiol (CBD), cannabidiolic acid (CBDA), cannabinol (CBN), cannabigerol (CBG), cannabigerol monomethyl ether (CBGM), cannabivarin (CBV), cannabidivarin (CBDV), tetrahydrocannabivarin (THCV), cannabichromene (CBC), cannabicyclol (CBL), cannabichromevarin (CBCV), cannabigerovarin (CBGV), cannabielsoin (CBE), cannabicitran (CBT) and combinations thereof.

[0055] By adjusting the amount of particulate plant material in the porous aerosol-generating substrate it may be advantageously possible to adjust the average bulk density of the porous aerosol-generating substrate. Furthermore, by adjusting the amount of particulate plant material in the porous aerosol-generating substrate, as well as the relative proportion of the particulate plant material to the aerosol former, it may be possible to tune the delivery of certain compounds, such as flavour compounds, into the aerosol generated from the porous aerosol-generating substrate upon heating.

[0056] Particulate plant material may be particularly advantageous for providing a homogeneous porous aerosol-generating substrate.

[0057] The plant particles may include a combination of tobacco particles and non-tobacco particles. Alternatively, the plant particles may be substantially free from tobacco material such that the porous aerosol-generating substrate is tobacco free.

[0058] The plant particles may have an average particle size of at least 25 microns. Preferably, the plant particles have an average particle size of at least 30 microns. More preferably, the plant particles have an average particle size of at least 35 microns. Even more preferably, the plant particles have an average particle size of at least 40 microns.

[0059] Use of plant particles having an average particle size of 25 microns or more may help control how easily the tobacco particles may be dispersed and kept in suspension within the aerosol former, which helps in providing an homogenous distribution of plant particles throughout the porous aerosol-generating substrate. The plant particles may have an average size of less than or equal to 250 microns. Preferably, the plant particles have an average size of less than or equal to 200 microns. More preferably, the plant particles have an average size of less than or equal to 180 microns. Even more preferably, the plant particles have an average size of less than or equal to 160 microns. Most preferably, the plant particles have an average size of less than or equal to 140 microns.

[0060] The plant particles may have an average size of from 30 microns to 200 microns, preferably from 35 microns to 200 microns, more preferably from 40 microns to 200 microns. In other embodiments, the plant particles have an average size of from 30 microns to 180 microns, preferably from 35 microns to 180 microns, more preferably from 40 microns to 180 microns. In further embodiments, the plant particles have an average size of from 30 microns to 160 microns, preferably from 35 microns to 160 microns, more preferably from 40 microns to 160 microns. In yet other embodiments, the plant particles have an average size of from 30 microns to 140 microns, preferably from 35 microns to 140 microns, more preferably from 40 microns to 140 microns.

[0061] Advantageously, using plant particles having an average size within the ranges described above has a beneficial impact on flowability and malleability of the porous aerosol-generating substrate, and may also enable some desirable control over porosity of the formed aerosolgenerating substrate, which helps in release of the aerosol species during use.

[0062] The plant particles may have a D90 value of less than or equal to 300 microns. This expression means that 90 percent of plant particles in the porous aerosol-generating substrate have a size of less than or equal to 300 microns. For a population of particles, the D90 value may be determined by analysing the particle size distribution. In more detail, looking at a particle size distribution curve, the D90 value can be determined by identifying the point on the curve below which 90 percent of the particles fall.

[0063] Preferably, the plant particles have a D90 value of less than or equal to 275 microns. More preferably, the plant particles have a D90 value of less than or equal to 250 microns. Even more preferably, the plant particles have a D90 value of less than or equal to 200 microns.

[0064] The plant particles may have a D90 value of at least 35 microns. Preferably, the plant particles have a D90 value of at least 40 microns. More preferably, the plant particles have a D90 value of at least 45 microns. Even more preferably, the plant particles have a D90 value of at least 50 microns.

[0065] The particle size distribution may be determined by laser diffraction. For example, the particle size distribution may be determined by laser diffraction using a Malvern Mastersizer 3000 laser diffraction particle size analyser in accordance with the manufacturer’s instructions.

[0066] Using plant particles having a D90 value falling within the ranges described above has the benefit that a regular particle distribution is achieved in the porous aerosol-generating substrate. This may facilitate controlling the porosity of the aerosol-generating substrate, which helps in release of the aerosol during use. Additionally, this helps ensure that a consistent aerosol can be generated from the porous aerosol-generating substrate upon heating.

[0067] Where the porous aerosol-generating substrate comprises plant particles from two or more different plants, the plant particles from each plant may have a different average size and particle size distribution to the plant particles from the other plant or plants. For example, where the porous aerosol-generating substrate comprises tobacco particles and non-tobacco particles, the D90 value of the non-tobacco particles may be higher than the D90 value of the tobacco particles.

[0068] Preferably, the porous aerosol-generating substrate comprises tobacco particles having a D90 value of between 35 microns and 100 microns, or between 40 microns and 80 microns, or between 50 microns and 70 microns.

[0069] Alternatively or additionally, the porous aerosol-generating substrate preferably comprises non-tobacco particles having a D90 value of between 50 microns and 250 microns, or between 75 microns and 200 microns, or between 100 microns and 200 microns, or between 100 microns and 150 microns.

[0070] By adjusting the amount of aerosol former in the porous aerosol-generating substrate it may be advantageously possible to tune the delivery of certain compounds, such as flavour compounds and / or nicotine, into the aerosol generated from the porous aerosol-generating substrate upon heating.

[0071] By adjusting the amount of aerosol former in the porous aerosol-generating substrate it may also be possible to produce a visually pleasant aerosol.

[0072] The aerosol former content of the porous aerosol-generating substrate may be at least 20 percent by weight, for example at least 30 percent by weight, for example at least 35 percent by weight, for example at least 40 percent by weight, for example at least 45 percent by weight, on a dry weight basis.

[0073] The aerosol former content of the porous aerosol-generating substrate may be less than or equal to 60 percent by weight, for example less than or equal to 50 percent by weight, on a dry weight basis.

[0074] The aerosol former content of the porous aerosol-generating substrate may be between 10 percent by weight and 60 percent by weight, on a dry weight basis, for example between 10 percent by weight and 50 percent by weight, on a dry weight basis.

[0075] The aerosol former content of the porous aerosol-generating substrate may be between 20 percent by weight and 60 percent by weight, on a dry weight basis, for example between 20 percent by weight and 50 percent by weight, on a dry weight basis. The aerosol former content of the porous aerosol-generating substrate may be between 30 percent by weight and 60 percent by weight, on a dry weight basis, for example between 30 percent by weight and 50 percent by weight, on a dry weight basis.

[0076] The aerosol former content of the porous aerosol-generating substrate may be between 35 percent by weight and 60 percent by weight, on a dry weight basis, for example between 35 percent by weight and 50 percent by weight, on a dry weight basis.

[0077] The aerosol former content of the porous aerosol-generating substrate may be between 40 percent by weight and 60 percent by weight, on a dry weight basis, for example between 40 percent by weight and 50 percent by weight, on a dry weight basis.

[0078] The aerosol former content of the porous aerosol-generating substrate may be between

[0079] 45 percent by weight and 60 percent by weight, on a dry weight basis, for example between 45 percent by weight and 50 percent by weight, on a dry weight basis.

[0080] The aerosol former content of the porous aerosol-generating substrate may be between

[0081] 46 percent by weight and 49 percent by weight, on a dry weight basis, for example between 47 percent by weight and 48 percent by weight, on a dry weight basis.

[0082] Suitable aerosol formers for use in the manufacture of porous aerosol-generating substrates according to the present invention include, but are not limited to, glycerin, propylene glycol, and mixtures thereof.

[0083] In examples of the invention, the aerosol former may be glycerin and the glycerin content of the porous aerosol-generating substrate may be at least 20 percent by weight, for example at least 30 percent by weight, for example at least 35 percent by weight, for example at least 40 percent by weight, for example at least 45 percent by weight, on a dry weight basis.

[0084] The glycerin content of the porous aerosol-generating substrate may be less than or equal to 60 percent by weight, for example less than or equal to 50 percent by weight, on a dry weight basis.

[0085] The glycerin content of the porous aerosol-generating substrate may be between 20 percent by weight and 60 percent by weight, on a dry weight basis, for example between 20 percent by weight and 50 percent by weight, on a dry weight basis.

[0086] The glycerin content of the porous aerosol-generating substrate may be between 30 percent by weight and 60 percent by weight, on a dry weight basis, for example between 30 percent by weight and 50 percent by weight, on a dry weight basis.

[0087] The glycerin content of the porous aerosol-generating substrate may be between 35 percent by weight and 60 percent by weight, on a dry weight basis, for example between 35 percent by weight and 50 percent by weight, on a dry weight basis. The glycerin content of the porous aerosol-generating substrate may be between 40 percent by weight and 60 percent by weight, on a dry weight basis, for example between 40 percent by weight and 50 percent by weight, on a dry weight basis.

[0088] The glycerin content of the porous aerosol-generating substrate may be between 45 percent by weight and 60 percent by weight, on a dry weight basis, for example between 45 percent by weight and 50 percent by weight, on a dry weight basis.

[0089] The glycerin content of the porous aerosol-generating substrate may be between 46 percent by weight and 49 percent by weight, on a dry weight basis, for example between 47 percent by weight and 48 percent by weight, on a dry weight basis.

[0090] The porous aerosol-generating substrate of the present invention further comprises a binder, which acts to improve the binding of the particulate plant material in the porous aerosolgenerating substrate and optimise the structural integrity of the porous aerosol-generating substrate.

[0091] The binder may comprise a cellulose binder. The cellulose binder may comprise one or more of hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), ethylcellulose (EC), hydroxyethyl methyl cellulose (HEMC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC) and hydroxypropyl cellulose (HPC).

[0092] The porous aerosol-generating substrate may have a cellulose binder content of at least 1 percent by weight, for example at least 2 percent by weight, for example at least 3 percent by weight, on a dry weight basis.

[0093] The cellulose binder content of the porous aerosol-generating substrate may be less than or equal to 10 percent by weight, on a dry weight basis.

[0094] The cellulose binder content of the aerosol-generating substrate may be between 1 percent by weight and 10 percent by weight, on a dry weight basis, for example between 2 percent by weight and 10 percent by weight, on a dry weight basis, for example between 3 percent by weight and 10 percent by weight, on a dry weight basis.

[0095] The binder may comprise a non-cellulose binder. The non-cellulose binder may comprise one or more of agar, guar gum, xanthan gum, Arabic gum, locust bean gum, pectin, carrageenan, starch and alginate.

[0096] The porous aerosol-generating substrate may have a non-cellulose binder content of at least 0.2 percent by weight, for example at least 0.4 percent by weight, for example at least 0.6 percent by weight, for example at least 0.8 percent by weight, on a dry weight basis.

[0097] The non-cellulose binder content of the porous aerosol-generating substrate may be less than or equal to 2 percent by weight, for example less than or equal to 1 .8 percent by weight, for example less than or equal to 1.6 percent by weight, for example less than or equal to 1.4 percent by weight, on a dry weight basis. The non-cellulose binder content of the porous aerosol-generating substrate may be between 0.2 percent by weight and 2 percent by weight, on a dry weight basis, for example between 0.2 percent by weight and 1 .8 percent by weight, on a dry weight basis, for example between 0.2 percent by weight and 1 .6 percent by weight, on a dry weight basis, for example between 0.2 percent by weight and 1.4 percent by weight, on a dry weight basis.

[0098] The non-cellulose binder content of the porous aerosol-generating substrate may be between 0.4 percent by weight and 2 percent by weight, on a dry weight basis, for example between 0.4 percent by weight and 1 .8 percent by weight, on a dry weight basis, for example between 0.4 percent by weight and 1 .6 percent by weight, on a dry weight basis, for example between 0.4 percent by weight and 1.4 percent by weight, on a dry weight basis.

[0099] The non-cellulose binder content of the porous aerosol-generating substrate may be between 0.6 percent by weight and 2 percent by weight, on a dry weight basis, for example between 0.6 percent by weight and 1 .8 percent by weight, on a dry weight basis, for example between 0.6 percent by weight and 1 .6 percent by weight, on a dry weight basis, for example between 0.6 percent by weight and 1 .4 percent by weight, on a dry weight basis.

[0100] The non-cellulose binder content of the porous aerosol-generating substrate may be between 0.8 percent by weight and 2 percent by weight, on a dry weight basis, for example between 0.8 percent by weight and 1 .8 percent by weight, on a dry weight basis, for example between 0.8 percent by weight and 1 .6 percent by weight, on a dry weight basis, for example between 0.8 percent by weight and 1.4 percent by weight on a dry weight basis.

[0101] The binder may comprise a cellulose binder and a non-cellulose binder. The binder may comprise one or more of HPMC, MC, EC, HEMC, HEC, CMC and HPC, and one or more of agar, guar gum, xanthan gum, Arabic gum, locust bean gum, pectin, carrageenan, starch and alginate. The binder may, for example, comprise HPMC and agar.

[0102] The porous aerosol-generating substrate may comprise a cellulose based strengthening agent, for example a particulate cellulose based strengthening agent.

[0103] The particulate cellulose based strengthening agent may comprise microcrystalline cellulose. Advantageously, the present inventors have found that microcrystalline cellulose may be a cellulose based strengthening agent that is particularly effective at increasing the tensile strength of an aerosol-generating substrate.

[0104] The particulate cellulose based strengthening agent may comprise cellulose powder. Advantageously, the present inventors have found that cellulose powder may be a cellulose based strengthening agent that is particularly effective at increasing the tensile strength of an aerosol-generating substrate.

[0105] The porous aerosol-generating substrate may also include a fibrous cellulose based strengthening agent. Advantageously, the present inventors have found that a fibrous cellulose based strengthening agent is effective at increasing the tensile strength of an aerosol-generating substrate.

[0106] The fibrous cellulose based strengthening agent may comprise an exogenous source of fibres. In other words, the fibrous cellulose based strengthening agent may be provided in addition to any tobacco material that may be provided. Suitable exogenous fibres for inclusion in the fibrous cellulose based strengthening agent may include fibres formed from non-tobacco material, including but not limited to: cellulose fibres, soft-wood fibres, hard-wood fibres, jute fibres and combinations thereof.

[0107] The porous aerosol-generating substrate may have a particulate cellulose based strengthening agent content of at least 0.5 percent by weight, for example at least 1 percent by weight, for example at least 5 percent by weight, for example at least 10 percent by weight, on a dry weight basis.

[0108] The particulate cellulose based strengthening agent content of the porous aerosolgenerating substrate may be less than or equal to 50 percent by weight, for example less than or equal to 40 percent by weight, for example less than or equal to 30 percent by weight, for example less than or equal to 20 percent by weight, on a dry weight basis.

[0109] The particulate cellulose based strengthening agent content of the porous aerosolgenerating substrate may be between 0.5 percent by weight and 50 percent by weight, on a dry weight basis, for example between 0.5 percent by weight and 40 percent by weight, on a dry weight basis, for example between 0.5 percent by weight and 30 percent by weight, on a dry weight basis, for example between 0.5 percent by weight and 20 percent by weight, on a dry weight basis.

[0110] The particulate cellulose based strengthening agent content of the porous aerosolgenerating substrate may be between 1 percent by weight and 50 percent by weight, on a dry weight basis, for example between 1 percent by weight and 40 percent by weight, on a dry weight basis, for example between 1 percent by weight and 30 percent by weight, on a dry weight basis, for example between 1 percent by weight and 20 percent by weight, on a dry weight basis.

[0111] The particulate cellulose based strengthening agent content of the porous aerosolgenerating substrate may be between 5 percent by weight and 50 percent by weight, on a dry weight basis, for example between 5 percent by weight and 40 percent by weight, on a dry weight basis, for example between 5 percent by weight and 30 percent by weight, on a dry weight basis, for example between 5 percent by weight and 20 percent by weight, on a dry weight basis.

[0112] The particulate cellulose based strengthening agent content of the porous aerosolgenerating substrate may be between 10 percent by weight and 50 percent by weight, on a dry weight basis, for example between 10 percent by weight and 40 percent by weight, on a dry weight basis, for example between 10 percent by weight and 30 percent by weight, on a dry weight basis, for example between 10 percent by weight and 20 percent by weight, on a dry weight basis.

[0113] The porous aerosol-generating substrate according to the present invention may further comprise one or more active agents. For example, the porous aerosol-generating substrate may comprise exogenous nicotine. The term “exogenous” refers to nicotine that is added to the porous aerosol-generating substrate as a distinct component from any nicotine that is intrinsically present in the particulate plant material, for example, where the particulate plant material comprises tobacco. Exogenous nicotine may be included in the porous aerosol-generating substrate where the particulate plant material is solely or largely non-tobacco plant material. The term “nicotine” encompasses nicotine, a nicotine base or a nicotine salt. In embodiments in which the porous aerosol-generating substrate comprises a nicotine base or a nicotine salt, the amounts of nicotine recited herein are the amount of free base nicotine or amount of protonated nicotine, respectively.

[0114] The porous aerosol-generating substrate may comprise a natural nicotine or a synthetic nicotine.

[0115] The porous aerosol-generating substrate may comprise less than or equal to 2 percent nicotine by weight, on a dry weight basis, for example less than or equal to 1.5 percent nicotine by weight, on a dry weight basis.

[0116] The porous aerosol-generating substrate may comprise at least 0.5 percent nicotine by weight on a dry weight basis, for example at least 1 percent nicotine by weight, on a dry weight basis.

[0117] The porous aerosol-generating substrate may comprise between 0.5 percent and 2 percent nicotine by weight, on a dry weight basis, for example between 0.5 percent and 1.5 percent nicotine by weight, on a dry weight basis.

[0118] The porous aerosol-generating substrate may comprise between 1 percent and 2 percent nicotine by weight, on a dry weight basis, for example between 1 percent and 1 .5 percent nicotine by weight, on a dry weight basis.

[0119] In examples, the porous aerosol-generating substrate may comprise approximately 1.5 percent nicotine by weight, on a dry weight basis.

[0120] The porous aerosol-generating substrate may further comprise one or more carboxylic acids. Advantageously, where the active agent comprises nicotine, including one or more carboxylic acids in the porous aerosol-generating substrate may create a nicotine salt. The carboxylic acid may comprise one or more of lactic acid, levulinic acid, benzoic acid, fumaric acid or acetic acid. Preferably, the carboxylic acid is at least one of fumaric acid, lactic acid or levulinic acid. The porous aerosol-generating substrate may have a carboxylic acid content of at least 0.5 percent by weight, preferably at least 1 percent by weight, more preferably at least 2 percent by weight, on a dry weight basis.

[0121] The porous aerosol-generating substrate may have a carboxylic acid content of less than or equal to 10 percent by weight, preferably less than or equal to 8 percent by weight, more preferably less than or equal to 8 percent by weight, on a dry weight basis.

[0122] For example, the porous aerosol-generating substrate may comprise between about 0.5 percent by weight and about 10 percent by weight of the acid, or between about 1 percent by weight and about 8 percent by weight of the acid, or between about 2 percent by weight and about 6 percent by weight of the acid, on a dry weight basis.

[0123] Additionally, or alternatively, the active agent may comprise a cannabinoid compound. The cannabinoid compound may be a naturally derived cannabinoid compound. The cannabinoid compound may be a synthetically derived cannabinoid compound. The cannabinoid compound may comprise one or more of tetrahydrocannabinol (THC), tetrahydrocannabinolic acid (THCA), cannabidiol (CBD), cannabidiolic acid (CBDA), cannabinol (CBN), cannabigerol (CBG), cannabigerol monomethyl ether (CBGM), cannabivarin (CBV), cannabidivarin (CBDV), tetrahydrocannabivarin (THCV), cannabichromene (CBC), cannabicyclol (CBL), cannabichromevarin (CBCV), cannabigerovarin (CBGV), cannabielsoin (CBE), cannabicitran (CBT) and combinations thereof.

[0124] The ability to form the porous aerosol-generating substrate into any desired shape enables it to be used in a wide variety of different types of aerosol-generating article, since the size and shape of the porous aerosol-generating substrate can be readily adapted to suit the space into which it is incorporated. The porous aerosol-generating substrate therefore offers improved flexibility and versatility.

[0125] The porous aerosol-generating substrate may have a quadrilaterally-faced hexahedron shape. The porous aerosol-generating substrate may, for example, have a cuboid shape. The porous aerosol-generating substrate may, for example, have a rectangular cuboid shape. The porous aerosol-generating substrate may, for example, have a parallelepiped shape.

[0126] The porous aerosol-generating substrate may have a cylindrical shape or an elliptical cylinder shape, for example the porous aerosol-generating substrate may be in the form of a rod.

[0127] As used herein, the term “rod” is used to denote a generally cylindrical element of substantially circular, oval or elliptical cross-section.

[0128] The porous aerosol-generating substrate may have a spherical shape.

[0129] The porous aerosol-generating substrate, for example the formed one-piece substrate, may be cuboidal. The porous aerosol-generating substrate, for example the formed cuboidal substrate, may have a length extending in an x-direction. The porous aerosol-generating substrate, for example the formed cuboidal substrate, may have a width extending in a y-direction. The substrate, for example the formed cuboidal substrate, may have a thickness extending in a z-direction.

[0130] The volume of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may therefore be calculated by multiplying the length by the width and by the thickness. In other words, the volume of the formed cuboidal substrate may be calculated by multiplying the length extending in the x-direction by the width extending in the y-direction and by the thickness extending in the z-direction.

[0131] The formed cuboidal substrate may be at least 1 millimetre in each of the x-direction, the y-direction and the z-direction. The formed cuboidal substrate may be at least 3 millimetres in one, two or all of the x-direction, the y-direction and the z-direction.

[0132] The length of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be less than or equal to 30 millimetres, for example less than or equal to 28 millimetres.

[0133] The length of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be at least 3 millimetres, for example at least 10 millimetres, for example at least 15 millimetres, for example at least 16 millimetres.

[0134] The length of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 3 millimetres and 30 millimetres, for example between 3 millimetres and 28 millimetres.

[0135] The length of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 10 millimetres and 30 millimetres, for example between 10 millimetres and 28 millimetres.

[0136] The length of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 15 millimetres and 30 millimetres, for example between 15 millimetres and 28 millimetres.

[0137] The length of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 16 millimetres and 30 millimetres, for example between 16 millimetres and 28 millimetres.

[0138] The width of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be less than or equal to 15 millimetres, for example less than or equal to 12 millimetres, for example less than or equal to 10 millimetres.

[0139] The width of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be at least 1 millimetre, for example at least 4 millimetres, for example at least 5 millimetres. The width of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 1 millimetre and 15 millimetres, for example between 1 millimetre and 12 millimetres, for example between 1 millimetre and 10 millimetres.

[0140] The width of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 4 millimetres and 15 millimetres, for example between 4 millimetres and 12 millimetres, for example between 4 millimetres and 10 millimetres.

[0141] The width of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 5 millimetres and 15 millimetres, for example between 5 millimetres and 12 millimetres, for example between 5 millimetres and 10 millimetres.

[0142] The thickness of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be less than or equal to 5 millimetres, for example less than or equal to 4 millimetres, for example less than or equal to 3 millimetres.

[0143] The thickness of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be at least 1 millimetre, for example at least 1.5 millimetres, for example at least 2 millimetres.

[0144] The thickness of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 1 millimetre and 5 millimetres, for example between 1 millimetre and 4 millimetres, for example between 1 millimetre and 3 millimetres.

[0145] The thickness of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 1.5 millimetres and 5 millimetres, for example between 1.5 millimetres and 4 millimetres, for example between 1.5 millimetres and 3 millimetres.

[0146] The thickness of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 2 millimetres and 5 millimetres, for example between 2 millimetres and 4 millimetres, for example between 2 millimetres and 3 millimetres.

[0147] The volume of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be less than or equal to 2250 cubic millimetres, for example less than or equal to 1344 cubic millimetres, for example less than or equal to 480 cubic millimetres.

[0148] The volume of the porous aerosol-generating substrate, for example the formed cuboidal substrate may be at least 3 cubic millimetres, for example at least 60 cubic millimetres, for example at lest 150 cubic millimetres.

[0149] The volume of the porous aerosol-generating substrate, for example the formed cuboidal substrate may be between 3 cubic millimetres and 2250 cubic millimetres, for example between 3 cubic millimetres and 1344 cubic millimetres, for example between 3 cubic millimetres and 480 cubic millimetres.

[0150] The volume of the porous aerosol-generating substrate, for example the formed cuboidal substrate may be between 60 cubic millimetres and 2250 cubic millimetres, for example between 60 cubic millimetres and 1344 cubic millimetres, for example between 60 cubic millimetres and 480 cubic millimetres.

[0151] The volume of the porous aerosol-generating substrate, for example the formed cuboidal substrate may be between 150 cubic millimetres and 2250 cubic millimetres, for example between 150 cubic millimetres and 1344 cubic millimetres, for example between 150 cubic millimetres and 480 cubic millimetres.

[0152] Alternatively, the porous aerosol-generating substrate, for example the formed substrate, may be cylindrical. The substrate, for example the formed cylindrical substrate, may have a length extending in an x-direction. The substrate, for example the formed cuboidal substrate, may have a diameter extending in a y-direction.

[0153] The volume of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may therefore be calculated by multiplying the length of the substrate by half the diameter squared and by Pi. In other words, the volume of the substrate may be calculated by multiplying the length extending in the x-direction by the square of half the diameter extending in the y-direction and by Pi.

[0154] The formed cylindrical substrate may be at least 1 millimetre in each of the x-direction and the y-direction. The formed substrate may be at least 3 millimetres in one or both of the x-direction and the y-direction.

[0155] The length of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be less than or equal to 115 millimetres, for example less than or equal to 107 millimetres, for example less than or equal to 68 millimetres.

[0156] The length of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be at least 4 millimetres, for example at least 34 millimetres, for example at least 48 millimetres.

[0157] The length of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be between 4 millimetres and 115 millimetres, for example between 4 millimetres and 107 millimetres, for example between 4 millimetres and 68 millimetres.

[0158] The length of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be between 34 millimetres and 115 millimetres, for example between 34 millimetres and 107 millimetres, for example between 34 millimetres and 68 millimetres.

[0159] The length of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be between 48 millimetres and 115 millimetres, for example between 48 millimetres and 107 millimetres, for example between 48 millimetres and 68 millimetres.

[0160] The diameter of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be less than or equal to 5 millimetres, for example less than or equal to 4 millimetres, for example less than or equal to 3 millimetres. The diameter of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be at least 1 millimetre, for example at least 1.5 millimetres, for example at least 2 millimetres.

[0161] The diameter of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be between 1 millimetre and 5 millimetres, for example between 1 millimetre and 4 millimetres, for example between 1 millimetre and 3 millimetres.

[0162] The diameter of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be between 1.5 millimetres and 5 millimetres, for example between 1.5 millimetres and 4 millimetres, for example between 1.5 millimetres and 3 millimetres.

[0163] The diameter of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be between 2 millimetres and 5 millimetres, for example between 2 millimetres and 4 millimetres, for example between 2 millimetres and 3 millimetres.

[0164] The volume of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be less than or equal to 2250 cubic millimetres, for example less than or equal to 1344 cubic millimetres, for example less than or equal to 480 cubic millimetres.

[0165] The volume of the porous aerosol-generating substrate, for example the formed cylindrical substrate may be at least 3 cubic millimetres, for example at least 60 cubic millimetres, for example at lest 150 cubic millimetres.

[0166] The volume of the porous aerosol-generating substrate, for example the formed cylindrical substrate may be between 3 cubic millimetres and 2250 cubic millimetres, for example between 3 cubic millimetres and 1344 cubic millimetres, for example between 3 cubic millimetres and 480 cubic millimetres.

[0167] The volume of the porous aerosol-generating substrate, for example the formed cylindrical substrate may be between 60 cubic millimetres and 2250 cubic millimetres, for example between 60 cubic millimetres and 1344 cubic millimetres, for example between 60 cubic millimetres and 480 cubic millimetres.

[0168] The volume of the porous aerosol-generating substrate, for example the formed cylindrical substrate may be between 150 cubic millimetres and 2250 cubic millimetres, for example between 150 cubic millimetres and 1344 cubic millimetres, for example between 150 cubic millimetres and 480 cubic millimetres.

[0169] The mass of the porous aerosol-generating substrate (the substrate mass) in the formed porous substrate, for example the formed cuboidal substrate or the formed cylindrical substrate may be at least 2 milligrams, for example at least 30 milligrams, for example at least 60 milligrams.

[0170] The substrate mass may be less than or equal to 563 milligrams, for example less than or equal to 470 milligrams, for example less than or equal to 178 milligrams. The substrate mass may be between 2 milligrams and 563 milligrams, for example between 30 milligrams and 563 milligrams, for example between 60 milligrams and 563 milligrams.

[0171] The substrate mass may be between 2 milligrams and 470 milligrams, for example between 30 milligrams and 470 milligrams, for example between 60 milligrams and 470 milligrams.

[0172] The substrate mass may be between 2 milligrams and 178 milligrams, for example between 30 milligrams and 178 milligrams, for example between 60 milligrams and 178 milligrams.

[0173] The average bulk density of the aerosol-generating substrate material within the formed porous aerosol-generating substrate unit (the substrate density), for example the formed cuboidal substrate or the formed cylindrical substrate is determined by dividing the mass of aerosolgenerating substrate in the formed porous aerosol-generating substrate unit, for example the formed cuboidal substrate or the formed cylindrical substrate, by the volume of the formed porous aerosol-generating substrate unit.

[0174] The substrate density may be at least 0.25 milligrams per cubic millimetre, for example at least 0.35 milligrams per cubic millimetre, for example at least 0.37 milligrams per cubic millimetre.

[0175] The substrate density may be less than or equal to 0.55 milligrams per cubic millimetre, for example less than or equal to 0.5 milligrams per cubic millimetre, for example less than or equal to 0.4 milligrams per cubic millimetre.

[0176] The substrate density may be between 0.25 milligrams per cubic millimetre and 0.55 milligrams per cubic millimetre, for example between 0.25 milligrams per cubic millimetre and 0.5 milligrams per cubic millimetre, for example between 0.25 milligrams per cubic millimetre and 0.4 milligrams per cubic millimetre.

[0177] The substrate density may be between 0.35 milligrams per cubic millimetre and 0.55 milligrams per cubic millimetre, for example between 0.35 milligrams per cubic millimetre and 0.5 milligrams per cubic millimetre, for example between 0.35 milligrams per cubic millimetre and 0.4 milligrams per cubic millimetre.

[0178] The substrate density may be between 0.37 milligrams per cubic millimetre and 0.55 milligrams per cubic millimetre, for example between 0.37 milligrams per cubic millimetre and 0.5 milligrams per cubic millimetre, for example between 0.37 milligrams per cubic millimetre and 0.4 milligrams per cubic millimetre.

[0179] The provision of a porous aerosol-generating substrate having a relatively low average bulk density may allow the aerosol-generating substrate to increase in temperature relatively quickly at the start of a user experience. This may help to ensure that all of the necessary volatile components within the aerosol-generating substrate are aerosolised simultaneously. This may advantageously prevent the less volatile components, such as aerosol former, from being delivered to the user after the more volatile components, such as nicotine. This may therefore lead to a more consistent user experience.

[0180] With flat consumables, for example including porous aerosol-generating substrate that is cuboidal, the gradient of temperature through the formed substrate unit is lower than in round consumables, for example including aerosol-generating substrate that is cylindrical, since the whole porous aerosol-generating substrate is closer to the heating element. By reducing the average bulk density of the porous aerosol-generating substrate, the conduction of heat through the aerosol-generating substrate may be reduced, thereby increasing the gradient of temperature through the aerosol-generating substrate. The temperature gradient may be useful to ensure that the aerosol is delivered throughout the experience.

[0181] With dielectric heating, the whole aerosol-generating substrate can be heated by microwaves and so there is a low temperature gradient whether or not the aerosol-generating substrate is close to the heater.

[0182] Porosity is a measure of the volume of voids within a substrate, and is expressed as a percentage of the total volume of the aerosol-generating substrate. Computer tomography (CT) scanning, for example X-ray CT scanning, may be used to determine the porosity of the aerosolgenerating substrate. Images of a sample which include solid and void parts may be obtained. Image processing software may then be used to calculate the extent of the voids in the internal structure of the aerosol-generating substrate. An example of such a method is described in Prokop and Pina: “Porosity Measurement Method by X-Ray Computer Topography”; Key Engineering Materials; March 2009.

[0183] The aerosol-generating substrate may have a porosity of at least 60 percent, for example at least 70 percent.

[0184] The porosity of the aerosol-generating substrate may be less than or equal to 98 percent, for example less than or equal to 97 percent.

[0185] The porosity of the aerosol-generating substrate may be between 60 percent and 98 percent, for example between 60 percent and 97 percent, for example between 70 percent and 98 percent, for example between 70 percent and 97 percent.

[0186] The present invention further provides a method for the production of a porous aerosolgenerating substrate according to the invention. The method according to the present invention comprises the steps of: mixing the binder and the aerosol former to disperse the binder in the aerosol former, thereby forming a first slurry; mixing water into the first slurry; adding the particulate plant material and mixing to form a final slurry, and drying the final slurry.

[0187] The particulate plant material may comprise tobacco or non-tobacco material, or a combination thereof, as described above. The first slurry is preferably a slurry of the binder in water or the aerosol former, or a combination thereof. The binder slurry may include a cellulose binder, as defined above, for example hydroxypropyl methylcellulose (HPMC), and / or a non-cellulose binder, as defined above, for example agar. The aerosol former may include glycerin, or any other suitable aerosol former, as defined above.

[0188] The mixing and the combining of the different slurries may be done by employing one or more of: a spiral mixer, a pulper, a high shear mixer with dispersion discs, a liquid mixer with Rushton impeller, an anchor stirrer and dispersion discs and a helicoidal agitator. These mixing tools are particularly suited in order to mix the binder, the water and the aerosol former for the first slurry. These mixing tools also may be suited in order to produce the final slurry.

[0189] The step of forming the porous aerosol-generating substrate may include pouring the final slurry into a mould before drying the final slurry, i.e. casting the aerosol-generating substrate. Alternatively, the aerosol-generating substrate may be dried and subsequently cut to the required dimensions.

[0190] The drying step may be carried out using any suitable means, including but not limited to heating and lyophilisation (freeze drying).

[0191] The structure of the aerosol-generating substrate can be controlled by controlling the freezing temperature and / or the rate of freezing during the lyophilisation process.

[0192] Freezing the final slurry slowly leads to larger, coarser, ice crystals which are, in turn, easier to dry because the porous structure of the solid generated is more open and connected. Conversely, freezing the final slurry quickly leads to fine ice crystals and smaller pores in the solid, which takes longer to dry because of more convoluted vapour pathways.

[0193] The critical freeze-drying temperature is the maximum temperature at which a substance can be freeze-dried. This is usually the eutectic temperature, or the collapse temperature, whichever is lower. If the temperature of the substrate material is allowed to rise above its eutectic temperature some liquid will form, and will boil during evacuation. This negatively impacts the structure of the substrate, as well as yield of the product. If the substrate material is allowed to rise above its collapse temperature during the drying process, it will structurally collapse because of its low viscosity.

[0194] The freeze drying temperature may be, in examples of the invention, between minus 10 degrees Celsius and minus 40 degrees Celsius, for example the freezing temperature may be between minus 10 degrees Celsius and minus 20 degrees Celsius.

[0195] The method of manufacturing or producing the porous aerosol-generating substrate of the present invention advantageously enables the production of porous aerosol-generating substrate in one-piece foamed or porous aerosol-generating substrate elements or units. This beneficially reduces the amount of substrate material lost or wasted both during the manufacture of aerosol- generating article and when an aerosol-generating article is placed in an aerosol-generating device and thus the cost effectiveness of the manufacture of aerosol-generating articles including aerosol-generating substrate.

[0196] The time taken to manufacture aerosol-generating articles including the porous aerosolgenerating substrate of the present invention is also reduced, and thus the efficiency of the manufacturing process is improved.

[0197] The porous aerosol-generating substrate may comprise an active agent and / or a flavourant, a particulate cellulose based strengthening agent and an aerosol former.

[0198] The porous aerosol-generating substrate may have an aerosol-former content of at least 10 percent by weight, on a dry weight basis. The aerosol-generating substrate may comprise a binder. The porous aerosol-generating substrate may have a binder content of at least 1 percent by weight, on a dry weight basis. The porous aerosol-generating substrate may be formed as a one-piece unit having a length, a width and a thickness. Each of the length, the width and the thickness may be at least 1 millimetre. At least one of the length, the width and the thickness may be at least 3 millimetres.

[0199] According to an aspect of the present invention, there is provided a porous aerosolgenerating substrate for an aerosol-generating article, the porous aerosol-generating substrate comprising an active agent and / or a flavourant, a particulate cellulose based strengthening agent and an aerosol former, wherein the porous aerosol-generating substrate has an aerosol former content of at least 10 percent by weight. The aerosol-generating substrate may comprise a binder. The porous aerosol-generating substrate may have a binder content of at least 1 percent by weight, on a dry weight basis. The porous aerosol-generating substrate may be formed as a one-piece unit having a length, a width and a thickness. Each of the length, the width and the thickness may be at least 1 millimetre. At least one of the length, the width and the thickness may be at least 3 millimetres.

[0200] According to an aspect of the present invention, there is provided a porous aerosolgenerating substrate for an aerosol-generating article, the porous aerosol-generating substrate comprising: an active agent and / or a flavourant; a particulate cellulose based strengthening agent; an aerosol former; and a binder; wherein the aerosol-generating substrate has an aerosol former content of at least 10 percent by weight, on a dry weight basis and a binder content of at least 1 percent by weight, on a dry weight basis. The porous aerosol-generating substrate may be formed as a one-piece unit having a length, a width and a thickness. Each of the length, the width and the thickness may be at least 1 millimetre. At least one of the length, the width and the thickness may be at least 3 millimetres.

[0201] According to an aspect of the present invention, there is provided a porous aerosolgenerating substrate for an aerosol-generating article, the porous aerosol-generating substrate comprising: an active agent and / or a flavourant; a particulate cellulose based strengthening agent; an aerosol former; and a binder; wherein the aerosol-generating substrate has an aerosol former content of at least 10 percent by weight, on a dry weight basis and a binder content of at least 1 percent by weight on a dry weight basis. The porous aerosol-generating substrate is formed as a one-piece unit having a length, a width and a thickness. Each of the length, the width and the thickness is at least 1 millimetre. At least one of the length, the width and the thickness is at least 3 millimetres..

[0202] The porous aerosol-generating substrate may contain substantially no tobacco material. The porous aerosol-generating substrate may, for example, comprise no tobacco material. In other words, the porous aerosol-generating substrate may be tobacco-free.

[0203] According to an aspect of the invention, there is provided a method of manufacturing a porous aerosol-generating substrate, as defined above.

[0204] The method may comprise mixing the binder and the aerosol former to form a first slurry; mixing water into the first slurry; adding the active agent and / or the flavourant, and the particulate cellulose based strengthening agent to the first slurry; mixing to form a final slurry; and drying the final slurry.

[0205] The step of forming the porous aerosol-generating substrate may include pouring the final slurry into a mould before drying the final slurry, i.e. casting the porous aerosol-generating substrate. Alternatively, the porous aerosol-generating substrate may be dried and subsequently cut to the required dimensions.

[0206] The drying step may be carried out using any suitable means, including but not limited to heating and lyophilisation (freeze-drying).

[0207] The active agent of the porous aerosol-generating substrate may comprise nicotine, for example exogenous nicotine. The term “exogenous” refers to nicotine that is added to the aerosol-generating substrate as a distinct component from any nicotine that is intrinsically present in the particulate plant material, for example, where the particulate plant material comprises tobacco. Exogenous nicotine may be included in the porous aerosol-generating substrate where the particulate plant material is solely or largely non-tobacco plant material. The term “nicotine” encompasses nicotine, a nicotine base or a nicotine salt. In embodiments in which the porous aerosol-generating substrate comprises a nicotine base or a nicotine salt, the amounts of nicotine recited herein are the amount of free base nicotine or amount of protonated nicotine, respectively.

[0208] The porous aerosol-generating substrate may comprise a natural nicotine or a synthetic nicotine.

[0209] The porous aerosol-generating substrate may comprise less than or equal to 2 percent nicotine by weight, on a dry weight basis, for example less than or equal to 1.5 percent nicotine by weight, on a dry weight basis. The aerosol-generating substrate may comprise at least 0.5 percent nicotine, for example at least 1 percent nicotine by weight, on a dry weight basis.

[0210] The aerosol-generating substrate may comprise between 0.5 percent and 2 percent nicotine by weight, on a dry weight basis, for example between 0.5 percent and 1.5 percent nicotine by weight, on a dry weight basis.

[0211] The aerosol-generating substrate may comprise between 1 percent and 2 percent nicotine by weight, on a dry weight basis, for example between 1 percent and 1.5 percent nicotine by weight, on a dry weight basis.

[0212] In examples, the aerosol-generating substrate may comprise approximately 1.5 percent nicotine by weight, on a dry weight basis.

[0213] The active agent and / or the flavourant of the porous aerosol-generating substrate may comprise a particulate plant material, for example a non-tobacco plant material.

[0214] The non-tobacco plant material may comprise one or more of: tea (such as black tea), rosehip seeds, apple fibres, lemon balm stems, coffee, star anise, rooibos, lavender, clove, peppermint, chamomile, rosemary, eucalyptus, ginger, dill seed, thyme, oregano and cumin.

[0215] Additionally, or alternatively, the active agent of the aerosol-generating substrate, for example the non-tobacco plant material, may comprise one or more cannabinoid compounds. The one or more cannabinoid compounds may be selected from the group consisting of: tetrahydrocannabinol (THC), tetrahydrocannabinolic acid (THCA), cannabidiol (CBD), cannabidiolic acid (CBDA), cannabinol (CBN), cannabigerol (CBG), cannabigerol monomethyl ether (CBGM), cannabivarin (CBV), cannabidivarin (CBDV), tetrahydrocannabivarin (THCV), cannabichromene (CBC), cannabicyclol (CBL), cannabichromevarin (CBCV), cannabigerovarin (CBGV), cannabielsoin (CBE), cannabicitran (CBT) and combinations thereof.

[0216] The flavourant of the aerosol-generating substrate may comprise one or more of: one or more essential oils such as eugenol, peppermint oil and spearmint oil; one or both of menthol and eugenol; one or both of anethole and linalool.

[0217] Particulate plant material may be particularly advantageous for providing a homogeneous aerosol-generating substrate.

[0218] The plant particles may be substantially free from tobacco material such that the aerosolgenerating substrate is tobacco free.

[0219] The plant particles may have an average particle size of at least 25 microns. Preferably, the plant particles have an average particle size of at least 30 microns. More preferably, the plant particles have an average particle size of at least 35 microns. Even more preferably, the plant particles have an average particle size of at least 40 microns.

[0220] Use of plant particles having an average particle size of 25 microns or more may help control how easily the particles may be dispersed and kept in suspension within the aerosol former, which helps in providing an homogenous distribution of plant particles throughout the porous aerosol-generating substrate.

[0221] The plant particles may have an average size of less than or equal to 250 microns. Preferably, the plant particles have an average size of less than or equal to 200 microns. More preferably, the plant particles have an average size of less than or equal to 180 microns. Even more preferably, the plant particles have an average size of less than or equal to 160 microns. Most preferably, the plant particles have an average size of less than or equal to 140 microns.

[0222] The plant particles may have an average size of from 30 microns to 200 microns, preferably from 35 microns to 200 microns, more preferably from 40 microns to 200 microns. In other embodiments, the plant particles have an average size of from 30 microns to 180 microns, preferably from 35 microns to 180 microns, more preferably from 40 microns to 180 microns. In further embodiments, the plant particles have an average size of from 30 microns to 160 microns, preferably from 35 microns to 160 microns, more preferably from 40 microns to 160 microns. In yet other embodiments, the plant particles have an average size of from 30 microns to 140 microns, preferably from 35 microns to 140 microns, more preferably from 40 microns to 140 microns.

[0223] Advantageously, using plant particles having an average size within the ranges described above has a beneficial impact on flowability and malleability of the aerosol-generating substrate, and may also enable some desirable control over porosity of the formed aerosol-generating substrate, which helps in release of the aerosol species during use.

[0224] The plant particles may have a D90 value of less than or equal to 300 microns. This expression means that 90 percent of plant particles in the porous aerosol-generating substrate have a size of less than or equal to 300 microns. For a population of particles, the D90 value may be determined by analysing the particle size distribution. In more detail, looking at a particle size distribution curve, the D90 value can be determined by identifying the point on the curve below which 90 percent of the particles fall.

[0225] Preferably, the plant particles have a D90 value of less than or equal to 275 microns. More preferably, the plant particles have a D90 value of less than or equal to 250 microns. Even more preferably, the plant particles have a D90 value of less than or equal to 200 microns.

[0226] The plant particles may have a D90 value of at least 35 microns. Preferably, the plant particles have a D90 value of at least 40 microns. More preferably, the plant particles have a D90 value of at least 45 microns. Even more preferably, the plant particles have a D90 value of at least 50 microns.

[0227] The particle size distribution may be determined by laser diffraction. For example, the particle size distribution may be determined by laser diffraction using a Malvern Mastersizer 3000 laser diffraction particle size analyser in accordance with the manufacturer’s instructions. Using plant particles having a D90 value falling within the ranges described above has the benefit that a regular particle distribution is achieved in the porous aerosol-generating substrate. This may facilitate controlling the porosity of the aerosol-generating substrate, which helps in release of the aerosol during use. Additionally, this helps ensure that a consistent aerosol can be generated from the porous aerosol-generating substrate upon heating.

[0228] Where the porous aerosol-generating substrate comprises plant particles from two or more different plants, the plant particles from each plant may have a different average size and particle size distribution to the plant particles from the other plant or plants.

[0229] Alternatively or additionally, the aerosol-generating substrate preferably comprises nontobacco particles having a D90 value of between 50 microns and 250 microns, or between 75 microns and 200 microns, or between 100 microns and 200 microns, or between 100 microns and 150 microns.

[0230] The cellulose based strengthening agent may comprise a particulate cellulose based strengthening agent.

[0231] The particulate cellulose based strengthening agent may comprise microcrystalline cellulose. Advantageously, the present inventors have found that microcrystalline cellulose may be a cellulose based strengthening agent that is particularly effective at increasing the tensile strength of an aerosol-generating substrate.

[0232] The particulate cellulose based strengthening agent may comprise cellulose powder. Advantageously, the present inventors have found that cellulose powder may be a cellulose based strengthening agent that is particularly effective at increasing the tensile strength of an aerosol-generating substrate.

[0233] The porous aerosol-generating substrate may also include a fibrous cellulose based strengthening agent. The fibrous cellulose based strengthening agent may comprise an exogenous source of fibres. In other words, the fibrous cellulose based strengthening agent may be provided in addition to any tobacco material that may be provided. Suitable exogenous fibres for inclusion in the fibrous cellulose based strengthening agent may include fibres formed from non-tobacco material, including but not limited to: cellulose fibres, soft-wood fibres, hard-wood fibres, jute fibres and combinations thereof.

[0234] Advantageously, the present inventors have found that a fibrous cellulose based strengthening agent is particularly effective at increasing the tensile strength of an aerosolgenerating substrate.

[0235] The particulate cellulose based strengthening agent content of the porous aerosolgenerating substrate may be at least 0.5 percent by weight, for example at least 1 percent by weight, for example at least 5 percent by weight, for example at least 10 percent by weight, on a dry weight basis. The particulate cellulose based strengthening agent content of the porous aerosolgenerating substrate may be less than or equal to 50 percent by weight, for example less than or equal to 40 percent by weight, for example less than or equal to 30 percent by weight, for example less than or equal to 20 percent by weight, on a dry weight basis.

[0236] The particulate cellulose based strengthening agent content of the porous aerosolgenerating substrate may be between 0.5 percent by weight and 50 percent by weight, on a dry weight basis, for example between 0.5 percent by weight and 40 percent by weight, on a dry weight basis, for example between 0.5 percent by weight and 30 percent by weight, on a dry weight basis, for example between 0.5 percent by weight and 20 percent by weight, on a dry weight basis.

[0237] The particulate cellulose based strengthening agent content of the porous aerosolgenerating substrate may be between 1 percent by weight and 50 percent by weight, on a dry weight basis, for example between 1 percent by weight and 40 percent by weight, on a dry weight basis, for example between 1 percent by weight and 30 percent by weight, on a dry weight basis, for example between 1 percent by weight and 20 percent by weight, on a dry weight basis.

[0238] The particulate cellulose based strengthening agent content of the porous aerosolgenerating substrate may be between 5 percent by weight and 50 percent by weight, on a dry weight basis, for example between 5 percent by weight and 40 percent by weight, on a dry weight basis, for example between 5 percent by weight and 30 percent by weight, on a dry weight basis, for example between 5 percent by weight and 20 percent by weight, on a dry weight basis.

[0239] The particulate cellulose based strengthening agent content of the porous aerosolgenerating substrate may be between 10 percent by weight and 50 percent by weight, on a dry weight basis, for example between 10 percent by weight and 40 percent by weight, on a dry weight basis, for example between 10 percent by weight and 30 percent by weight, on a dry weight basis, for example between 10 percent by weight and 20 percent by weight, on a dry weight basis.

[0240] By adjusting the amount of aerosol former in the porous aerosol-generating substrate it may be advantageously possible to tune the delivery of certain compounds, such as flavour compounds (or flavourants) and / or nicotine, into the aerosol-generated from the porous aerosolgenerating substrate upon heating.

[0241] By adjusting the amount of aerosol former in the porous aerosol-generating substrate it may also be possible to produce a visually pleasant aerosol.

[0242] The aerosol former content of the porous aerosol-generating substrate may be at least 20 percent by weight, for example at least 30 percent by weight, for example at least 35 percent by weight, for example at least 40 percent by weight, for example at least 45 percent by weight, on a dry weight basis. The aerosol former content of the porous aerosol-generating substrate may be less than or equal to 60 percent by weight, for example less than or equal to 50 percent by weight, on a dry weight basis.

[0243] The aerosol former content of the porous aerosol-generating substrate may be between 10 percent by weight and 60 percent by weight, on a dry weight basis, for example between 10 percent by weight and 50 percent by weight, on a dry weight basis.

[0244] The aerosol former content of the porous aerosol-generating substrate may be between 20 percent by weight and 60 percent by weight, on a dry weight basis, for example between 20 percent by weight and 50 percent by weight, on a dry weight basis.

[0245] The aerosol former content of the porous aerosol-generating substrate may be between 30 percent by weight and 60 percent by weight, on a dry weight basis, for example between 30 percent by weight and 50 percent by weight, on a dry weight basis.

[0246] The aerosol former content of the porous aerosol-generating substrate may be between 35 percent by weight and 60 percent by weight, on a dry weight basis, for example between 35 percent by weight and 50 percent by weight, on a dry weight basis.

[0247] The aerosol former content of the porous aerosol-generating substrate may be between 40 percent by weight and 60 percent by weight, on a dry weight basis, for example between 40 percent by weight and 50 percent by weight, on a dry weight basis.

[0248] The aerosol former content of the porous aerosol-generating substrate may be between

[0249] 45 percent by weight and 60 percent by weight, on a dry weight basis, for example between 45 percent by weight and 50 percent by weight, on a dry weight basis.

[0250] The aerosol former content of the porous aerosol-generating substrate may be between

[0251] 46 percent by weight and 49 percent by weight, on a dry weight basis, for example between 47 percent by weight and 48 percent by weight, on a dry weight basis.

[0252] Suitable aerosol formers for use in the manufacture of porous aerosol-generating substrates according to the present invention include, but are not limited to, glycerin, propylene glycol, and mixtures thereof.

[0253] In examples of the invention, the aerosol former may be glycerin and the glycerin content of the porous aerosol-generating substrate may be at least 10 percent by weight, for example at least 20 percent by weight, for example at least 30 percent by weight, for example at least 35 percent by weight, for example at least 40 percent by weight, for example at least 45 percent by weight, on a dry weight basis.

[0254] The glycerin content of the porous aerosol-generating substrate may be less than or equal to 60 percent by weight, for example less than or equal to 50 percent by weight, on a dry weight basis. The glycerin content of the porous aerosol-generating substrate may be between 10 percent by weight and 60 percent by weight, on a dry weight basis, for example between 10 percent by weight and 50 percent by weight, on a dry weight basis.

[0255] The glycerin content of the porous aerosol-generating substrate may be between 20 percent by weight and 60 percent by weight, on a dry weight basis, for example between 20 percent by weight and 50 percent by weight, on a dry weight basis.

[0256] The glycerin content of the porous aerosol-generating substrate may be between 30 percent by weight and 60 percent by weight, on a dry weight basis, for example between 30 percent by weight and 50 percent by weight, on a dry weight basis.

[0257] The glycerin content of the porous aerosol-generating substrate may be between 35 percent by weight and 60 percent by weight, on a dry weight basis, for example between 35 percent by weight and 50 percent by weight, on a dry weight basis.

[0258] The glycerin content of the porous aerosol-generating substrate may be between 40 percent by weight and 60 percent by weight, on a dry weight basis, for example between 40 percent by weight and 50 percent by weight, on a dry weight basis.

[0259] The glycerin content of the porous aerosol-generating substrate may be between 45 percent by weight and 60 percent by weight, on a dry weight basis, for example between 45 percent by weight and 50 percent by weight, on a dry weight basis.

[0260] The glycerin content of the porous aerosol-generating substrate may be between 46 percent by weight and 49 percent by weight, on a dry weight basis, for example between 47 percent by weight and 48 percent by weight, on a dry weight basis.

[0261] The binder of the porous aerosol-generating substrate may comprise a cellulose binder. The cellulose binder may comprise one or more of hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), ethylcellulose (EC), hydroxyethyl methyl cellulose (HEMC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC) and hydroxypropyl cellulose (HPC).

[0262] The porous aerosol-generating substrate may have a cellulose binder content of at least

[0263] 1 percent by weight, for example at least 2 percent by weight, for example at least 3 percent by weight, on a dry weight basis.

[0264] The cellulose binder content may be less than or equal to 10 percent by weight, on a dry weight basis.

[0265] The cellulose binder content may be between 1 percent by weight and 10 percent by weight, on a dry weight basis.

[0266] The cellulose binder content may be between 2 percent by weight and 10 percent by weight, on a dry weight basis.

[0267] The cellulose binder content may be between 3 percent by weight and 10 percent by weight, on a dry weight basis. The binder of the porous aerosol-generating substrate may comprise a non-cellulose binder. The non-cellulose binder may comprise one or more of agar, guar gum, xanthan gum, Arabic gum, locust bean gum, pectin, carrageenan, starch and alginate.

[0268] The porous aerosol-generating substrate may have a non-cellulose binder content of at least 0.2 percent by weight, for example at least 0.4 percent by weight, for example at least 0.6 percent by weight, for example at least 0.8 percent by weight, on a dry weight basis.

[0269] The non-cellulose binder content of the porous aerosol-generating substrate may be less than or equal to 2 percent by weight, for example less than or equal to 1.8 percent by weight, for example less than or equal to 1.6 percent by weight, for example less than or equal to 1.4 percent by weight, on a dry weight basis.

[0270] The non-cellulose binder content may be between 0.2 percent by weight and 2 percent by weight, on a dry weight basis. The non-cellulose binder content may be between 0.2 percent by weight and 1 .8 percent by weight, on a dry weight basis. The non-cellulose binder content may be between 0.2 percent by weight and 1 .6 percent by weight, on a dry weight basis. The non- cellulose binder content may be between 0.2 percent by weight and 1.4 percent by weight, on a dry weight basis.

[0271] The non-cellulose binder content may be between 0.4 percent by weight and 2 percent by weight, on a dry weight basis. The non-cellulose binder content may be between 0.4 percent by weight and 1 .8 percent by weight, on a dry weight basis. The non-cellulose binder content may be between 0.4 percent by weight and 1 .6 percent by weight, on a dry weight basis. The non- cellulose binder content may be between 0.4 percent by weight and 1.4 percent by weight, on a dry weight basis.

[0272] The non-cellulose binder content may be between 0.6 percent by weight and 2 percent by weight, on a dry weight basis. The non-cellulose binder content may be between 0.6 percent by weight and 1 .8 percent by weight, on a dry weight basis. The non-cellulose binder content may be between 0.6 percent by weight and 1 .6 percent by weight, on a dry weight basis. The non- cellulose binder content may be between 0.6 percent by weight and 1.4 percent by weight, on a dry weight basis.

[0273] The non-cellulose binder content may be between 0.8 percent by weight and 2 percent by weight, on a dry weight basis. The non-cellulose binder content may be between 0.8 percent by weight and 1 .8 percent by weight, on a dry weight basis. The non-cellulose binder content may be between 0.8 percent by weight and 1 .6 percent by weight. The non-cellulose binder content may be between 0.8 percent by weight and 1.4 percent by weight, on a dry weight basis.

[0274] The binder may comprise a cellulose binder and a non-cellulose binder. The binder may comprise one or more of HPMC, MC, EC, HEMC, HEC, CMC and HPC, and one or more of agar, guar gum, xanthan gum, Arabic gum, locust bean gum, pectin, carrageenan, starch and alginate. The binder may, for example, comprise HPMC and agar.

[0275] The porous aerosol-generating substrate may further comprise one or more carboxylic acids. Advantageously, where the active agent comprises nicotine, including one or more carboxylic acids in the aerosol-generating substrate may create a nicotine salt. The carboxylic acid may comprise one or more of lactic acid, levulinic acid, benzoic acid, fumaric acid or acetic acid. Preferably, the carboxylic acid is at least one of fumaric acid, lactic acid or levulinic acid.

[0276] The porous aerosol-generating substrate may have a carboxylic acid content of at least 0.5 percent by weight, preferably at least 1 percent by weight, more preferably at least 2 percent by weight, on a dry weight basis.

[0277] The porous aerosol-generating substrate may have a carboxylic acid content of less than or equal to 10 percent by weight, preferably less than or equal to 8 percent by weight, more preferably less than or equal to 8 percent by weight, on a dry weight basis.

[0278] For example, the porous aerosol-generating substrate may comprise between about 0.5 percent by weight and about 10 percent by weight of the acid, or between about 1 percent by weight and about 8 percent by weight of the acid, or between about 2 percent by weight and about 6 percent by weight of the acid, on a dry weight basis.

[0279] The ability to form the porous aerosol-generating substrate into any desired shape enables it to be used in a wide variety of different types of aerosol-generating article, since the size and shape of the porous aerosol-generating substrate can be readily adapted to suit the space into which it is incorporated. The porous aerosol-generating substrate therefore offers improved flexibility and versatility.

[0280] The porous aerosol-generating substrate may have a quadrilaterally-faced hexahedron shape. The porous aerosol-generating substrate may, for example, have a cuboid shape. The porous aerosol-generating substrate may, for example, have a rectangular cuboid shape. The porous aerosol-generating substrate may, for example, have a parallelepiped shape.

[0281] The porous aerosol-generating substrate may have a cylindrical shape or an elliptical cylinder shape, for example the porous aerosol-generating substrate may be in the form of a rod.

[0282] As used herein, the term “rod” is used to denote a generally cylindrical element of substantially circular, oval or elliptical cross-section.

[0283] The porous aerosol-generating substrate may have a spherical shape.

[0284] The porous aerosol-generating substrate, for example the formed porous aerosolgenerating substrate, may be cuboidal. The porous aerosol-generating substrate, for example the formed porous aerosol-generating cuboidal substrate, may have a length extending in an x- direction. The porous aerosol-generating substrate, for example the formed cuboidal substrate, may have a width extending in a y-direction. The substrate, for example the formed cuboidal substrate, may have a thickness extending in a z-direction.

[0285] The volume of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may therefore be calculated by multiplying the length by the width and by the thickness. In other words, the volume of the formed cuboidal substrate may be calculated by multiplying the length extending in the x-direction by the width extending in the y-direction and by the thickness extending in the z-direction.

[0286] The formed porous cuboidal substrate may be at least 1 millimetre in each of the x- direction, the y-direction and the z-direction. The formed cuboidal substrate may be at least 3 millimetres in one, two or all of the x-direction, the y-direction and the z-direction.

[0287] The length of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be less than or equal to 30 millimetres, for example less than or equal to 28 millimetres.

[0288] The length of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be at least 3 millimetres, for example at least 10 millimetres, for example at least 15 millimetres, for example at least 16 millimetres.

[0289] The length of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 3 millimetres and 30 millimetres, for example between 3 millimetres and 28 millimetres.

[0290] The length of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 10 millimetres and 30 millimetres, for example between 10 millimetres and 28 millimetres.

[0291] The length of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 15 millimetres and 30 millimetres, for example between 15 millimetres and 28 millimetres.

[0292] The length of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 16 millimetres and 30 millimetres, for example between 16 millimetres and 28 millimetres.

[0293] The width of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be less than or equal to 15 millimetres, for example less than or equal to 12 millimetres, for example less than or equal to 10 millimetres.

[0294] The width of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be at least 1 millimetre, for example at least 4 millimetres, for example at least 5 millimetres. The width of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 1 millimetre and 15 millimetres, for example between 1 millimetre and 12 millimetres, for example between 1 millimetre and 10 millimetres.

[0295] The width of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 4 millimetres and 15 millimetres, for example between 4 millimetres and 12 millimetres, for example between 4 millimetres and 10 millimetres.

[0296] The width of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 5 millimetres and 15 millimetres, for example between 5 millimetres and 12 millimetres, for example between 5 millimetres and 10 millimetres.

[0297] The thickness of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be less than or equal to 5 millimetres, for example less than or equal to 4 millimetres, for example less than or equal to 3 millimetres.

[0298] The thickness of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be at least 1 millimetre, for example at least 1.5 millimetres, for example at least 2 millimetres.

[0299] The thickness of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 1 millimetre and 5 millimetres, for example between 1 millimetre and 4 millimetres, for example between 1 millimetre and 3 millimetres.

[0300] The thickness of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 1.5 millimetres and 5 millimetres, for example between 1.5 millimetres and 4 millimetres, for example between 1.5 millimetres and 3 millimetres.

[0301] The thickness of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be between 2 millimetres and 5 millimetres, for example between 2 millimetres and 4 millimetres, for example between 2 millimetres and 3 millimetres.

[0302] The volume of the porous aerosol-generating substrate, for example the formed cuboidal substrate, may be less than or equal to 2250 cubic millimetres, for example less than or equal to 1344 cubic millimetres, for example less than or equal to 480 cubic millimetres.

[0303] The volume of the porous aerosol-generating substrate, for example the formed cuboidal substrate may be at least 3 cubic millimetres, for example at least 60 cubic millimetres, for example at lest 150 cubic millimetres.

[0304] The volume of the porous aerosol-generating substrate, for example the formed cuboidal substrate may be between 3 cubic millimetres and 2250 cubic millimetres, for example between 3 cubic millimetres and 1344 cubic millimetres, for example between 3 cubic millimetres and 480 cubic millimetres.

[0305] The volume of the porous aerosol-generating substrate, for example the formed cuboidal substrate may be between 60 cubic millimetres and 2250 cubic millimetres, for example between 60 cubic millimetres and 1344 cubic millimetres, for example between 60 cubic millimetres and 480 cubic millimetres.

[0306] The volume of the porous aerosol-generating substrate, for example the formed cuboidal substrate may be between 150 cubic millimetres and 2250 cubic millimetres, for example between 150 cubic millimetres and 1344 cubic millimetres, for example between 150 cubic millimetres and 480 cubic millimetres.

[0307] Alternatively, the porous aerosol-generating substrate, for example the formed substrate, may be cylindrical. The porous aerosol-generating substrate, for example the formed cylindrical substrate, may have a length extending in an x-direction. The substrate, for example the formed cuboidal substrate, may have a diameter extending in a y-direction.

[0308] The volume of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may therefore be calculated by multiplying the length of the substrate by half the diameter squared and by Pi. In other words, the volume of the substrate may be calculated by multiplying the length extending in the x-direction by the square of half the diameter extending in the y-direction and by Pi.

[0309] The formed cylindrical substrate may be at least 1 millimetre in each of the x-direction and the y-direction. The formed substrate may be at least 3 millimetres in one or both of the x-direction and the y-direction.

[0310] The length of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be less than or equal to 115 millimetres, for example less than or equal to 107 millimetres, for example less than or equal to 68 millimetres.

[0311] The length of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be at least 4 millimetres, for example at least 34 millimetres, for example at least 48 millimetres.

[0312] The length of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be between 4 millimetres and 115 millimetres, for example between 4 millimetres and 107 millimetres, for example between 4 millimetres and 68 millimetres.

[0313] The length of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be between 34 millimetres and 115 millimetres, for example between 34 millimetres and 107 millimetres, for example between 34 millimetres and 68 millimetres.

[0314] The length of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be between 48 millimetres and 115 millimetres, for example between 48 millimetres and 107 millimetres, for example between 48 millimetres and 68 millimetres.

[0315] The diameter of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be less than or equal to 5 millimetres, for example less than or equal to 4 millimetres, for example less than or equal to 3 millimetres. The diameter of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be at least 1 millimetre, for example at least 1.5 millimetres, for example at least 2 millimetres.

[0316] The diameter of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be between 1 millimetre and 5 millimetres, for example between 1 millimetre and 4 millimetres, for example between 1 millimetre and 3 millimetres.

[0317] The diameter of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be between 1.5 millimetres and 5 millimetres, for example between 1.5 millimetres and 4 millimetres, for example between 1.5 millimetres and 3 millimetres.

[0318] The diameter of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be between 2 millimetres and 5 millimetres, for example between 2 millimetres and 4 millimetres, for example between 2 millimetres and 3 millimetres.

[0319] The volume of the porous aerosol-generating substrate, for example the formed cylindrical substrate, may be less than or equal to 2250 cubic millimetres, for example less than or equal to 1344 cubic millimetres, for example less than or equal to 480 cubic millimetres.

[0320] The volume of the porous aerosol-generating substrate, for example the formed cylindrical substrate may be at least 3 cubic millimetres, for example at least 60 cubic millimetres, for example at lest 150 cubic millimetres.

[0321] The volume of the porous aerosol-generating substrate, for example the formed cylindrical substrate may be between 3 cubic millimetres and 2250 cubic millimetres, for example between 3 cubic millimetres and 1344 cubic millimetres, for example between 3 cubic millimetres and 480 cubic millimetres.

[0322] The volume of the porous aerosol-generating substrate, for example the formed cylindrical substrate may be between 60 cubic millimetres and 2250 cubic millimetres, for example between 60 cubic millimetres and 1344 cubic millimetres, for example between 60 cubic millimetres and 480 cubic millimetres.

[0323] The volume of the porous aerosol-generating substrate, for example the formed cylindrical substrate may be between 150 cubic millimetres and 2250 cubic millimetres, for example between 150 cubic millimetres and 1344 cubic millimetres, for example between 150 cubic millimetres and 480 cubic millimetres.

[0324] The mass of the porous aerosol-generating substrate (the substrate mass) in the formed substrate, for example the formed cuboidal substrate or the formed cylindrical substrate may be at least 2 milligrams, for example at least 30 milligrams, for example at least 60 milligrams.

[0325] The substrate mass may be less than or equal to 563 milligrams, for example less than or equal to 470 milligrams, for example less than or equal to 178 milligrams. The substrate mass may be between 2 milligrams and 563 milligrams, for example between 30 milligrams and 563 milligrams, for example between 60 milligrams and 563 milligrams.

[0326] The substrate mass may be between 2 milligrams and 470 milligrams, for example between 30 milligrams and 470 milligrams, for example between 60 milligrams and 470 milligrams.

[0327] The substrate mass may be between 2 milligrams and 178 milligrams, for example between 30 milligrams and 178 milligrams, for example between 60 milligrams and 178 milligrams.

[0328] The average bulk density of the aerosol-generating substrate material within the formed porous aerosol-generating substrate unit (the substrate density), for example the formed cuboidal substrate or the formed cylindrical substrate is determined by dividing the mass of substrate in the formed substrate unit, for example the formed cuboidal substrate or the formed cylindrical substrate, by the volume of the formed porous aerosol-generating substrate unit.

[0329] The substrate density may be at least 0.25 milligrams per cubic millimetre, for example at least 0.35 milligrams per cubic millimetre, for example at least 0.37 milligrams per cubic millimetre.

[0330] The substrate density may be less than or equal to 0.55 milligrams per cubic millimetre, for example less than or equal to 0.5 milligrams per cubic millimetre, for example less than or equal to 0.4 milligrams per cubic millimetre.

[0331] The substrate density may be between 0.25 milligrams per cubic millimetre and 0.55 milligrams per cubic millimetre, for example between 0.25 milligrams per cubic millimetre and 0.5 milligrams per cubic millimetre, for example between 0.25 milligrams per cubic millimetre and 0.4 milligrams per cubic millimetre.

[0332] The substrate density may be between 0.35 milligrams per cubic millimetre and 0.55 milligrams per cubic millimetre, for example between 0.35 milligrams per cubic millimetre and 0.5 milligrams per cubic millimetre, for example between 0.35 milligrams per cubic millimetre and 0.4 milligrams per cubic millimetre.

[0333] The substrate density may be between 0.37 milligrams per cubic millimetre and 0.55 milligrams per cubic millimetre, for example between 0.37 milligrams per cubic millimetre and 0.5 milligrams per cubic millimetre, for example between 0.37 milligrams per cubic millimetre and 0.4 milligrams per cubic millimetre.

[0334] The provision of a porous aerosol-generating substrate having a relatively low average bulk density may allow the porous aerosol-generating substrate to increase in temperature relatively quickly at the start of a user experience. This may help to ensure that all of the necessary volatile components within the aerosol-generating substrate are aerosolised simultaneously. This may advantageously prevent the less volatile components, such as aerosol former, from being delivered to the user after the more volatile components, such as nicotine. This may therefore lead to a more consistent user experience.

[0335] With flat consumables, for example including porous aerosol-generating substrate that is cuboidal, the gradient of temperature through the formed substrate unit is lower than in round consumables, for example including aerosol-generating substrate that is cylindrical, since the whole aerosol-generating substrate is closer to the heating element. By reducing the bulk density of the aerosol-generating substrate, the conduction of heat through the aerosol-generating substrate may be reduced, thereby increasing the gradient of temperature through the aerosolgenerating substrate. The temperature gradient may be useful to ensure that the aerosol is delivered throughout the experience.

[0336] With dielectric heating, the whole aerosol-generating substrate can be heated by microwaves and so there is a low temperature gradient whether or not the aerosol-generating substrate is close to the heater.

[0337] As described above, porosity is a measure of the volume of voids within a substrate, and is expressed as a percentage of the total volume of the substrate. Computer tomography (CT) scanning, for example X-ray CT scanning, may be used to determine the porosity of the aerosolgenerating substrate. Images of a sample which include solid and void parts may be obtained. Image processing software may then be used to calculate the extent of the voids in the internal structure of the aerosol-generating substrate. An example of such a method is described in Prokop and Pina: “Porosity Measurement Method by X-Ray Computer Topography”; Key Engineering Materials; March 2009.

[0338] The aerosol-generating substrate may have a porosity of at least 60 percent, for example at least 70 percent.

[0339] The porosity of the aerosol-generating substrate may be less than or equal to 98 percent, for example less than or equal to 97 percent.

[0340] The porosity of the aerosol-generating substrate may be between 60 percent and 98 percent, for example between 60 percent and 97 percent, for example between 70 percent and 98 percent, for example between 70 percent and 97 percent.

[0341] The present invention further provides a method for the production of a porous aerosolgenerating substrate, as defined above. The method according to the present invention comprises the steps of: mixing the binder and the aerosol former to disperse the binder in the aerosol former, thereby forming a first slurry; mixing water into the first slurry; adding the active agent and / or the flavourant, and the particulate cellulose based strengthening agent to the first slurry and water; mixing the active agent and / or the flavourant, the particulate cellulose based strengthening agent, the first slurry and water to form a final slurry; and drying the final slurry. The active material may be any one, or a combination of the active materials defined above.

[0342] The flavourant may be any one, or a combination of the flavourants defined above.

[0343] The first slurry is preferably a slurry of the binder in water or the aerosol former, or a combination thereof. The binder slurry may include a cellulose binder, as defined above, for example hydroxypropyl methylcellulose (HPMC), and / or a non-cellulose binder, as defined above, for example agar. The aerosol former may include glycerin, or any other suitable aerosol former, as defined above.

[0344] The mixing and the combining of the different slurries may be done by employing one or more of: a spiral mixer, a pulper, a high shear mixer with dispersion discs, a liquid mixer with Rushton impeller, an anchor stirrer and dispersion discs and a helicoidal agitator. These mixing tools are particularly suited in order to mix the binder, the water and the aerosol former for the first slurry. These mixing tools also may be suited in order to produce the final slurry.

[0345] The step of forming the porous aerosol-generating substrate may include pouring the final slurry into a mould before drying the final slurry, i.e. casting the aerosol-generating substrate. Alternatively, the aerosol-generating substrate may be dried and subsequently cut to the required dimensions.

[0346] The drying step may be carried out using any suitable means, including but not limited to heating and lyophilisation (freeze drying).

[0347] The structure of the aerosol-generating substrate can be controlled by controlling the freezing temperature and / or the rate of freezing during the lyophilisation process.

[0348] Freezing the final slurry slowly leads to larger, coarser, ice crystals which are, in turn, easier to dry because the porous structure of the solid generated is more open and connected. Conversely, freezing the final slurry quickly leads to fine ice crystals and smaller pores in the solid, which takes longer to dry because of more convoluted vapour pathways.

[0349] The critical freeze-drying temperature is the maximum temperature at which a substance can be freeze-dried. This is usually the eutectic temperature, or the collapse temperature, whichever is lower. If the temperature of the substrate material is allowed to rise above its eutectic temperature some liquid will form, and will boil during evacuation. This negatively impacts the structure of the substrate, as well as yield of the product. If the substrate material is allowed to rise above its collapse temperature during the drying process, it will structurally collapse because of its low viscosity.

[0350] The freeze drying temperature may be, in examples of the invention, between minus 10 degrees Celsius and minus 40 degrees Celsius, for example the freezing temperature may be between minus 10 degrees Celsius and minus 20 degrees Celsius. The method of manufacturing or producing the porous aerosol-generating substrate of the present invention advantageously enables the production of aerosol-generating substrate in one- piece foamed or porous elements or aerosol-generating substrate units. This beneficially reduces the amount of substrate material lost or wasted both during the manufacture of aerosol-generating article and when an aerosol-generating article is placed in an aerosol-generating device and thus the cost effectiveness of the manufacture of aerosol-generating articles including aerosolgenerating substrate.

[0351] The time taken to manufacture aerosol-generating articles including the aerosolgenerating substrate of the present invention is also reduced, and thus the efficiency of the manufacturing process is improved.

[0352] Porous aerosol-generating substrates according to the present invention may be used in a wide variety of different aerosol-generating articles. The present invention provides an aerosolgenerating article comprising a porous aerosol-generating substrate according to the present invention, as described above.

[0353] The porous aerosol-generating substrate may be combined with one or more elements upstream or downstream of the porous aerosol-generating substrate.

[0354] As used herein, “upstream” and “downstream” describe the relative positions of elements or portions of elements of the aerosol-generating article in relation to the direction in which the aerosol is transported through the aerosol-generating article during use.

[0355] Preferably, the aerosol-generating article according to the invention is substantially flat, or substantially planar. This means that the article has a relatively large base area relative to the volume of the article. As described above, the porous aerosol-generating substrate of the present invention has been found to be particularly suitable for use in flat aerosol-generating articles since it can be readily adapted to fill a space within an article having a flat shape with relatively large opposed surfaces. This form optimises heating of the porous aerosol-generating substrate and the generation of aerosol.

[0356] In certain preferred embodiments of the present invention, the aerosol-generating article comprises a first planar external surface and a second planar external surface. The aerosolgenerating article comprises a cavity. The aerosol-generating article comprises a frame positioned between the first planar external surface and the second planar external surface. The frame at least partially defines the cavity. The aerosol-generating article comprises one or more aerosol-generating substrates. The aerosol-generating article comprises an air inlet and an air outlet. The aerosol-generating article comprises an airflow passage extending between the air inlet and the air outlet through the cavity.

[0357] The cavity may have a length extending in an x-direction. The cavity may have a width extending in a y-direction. The cavity may have a thickness extending in a z-direction. The length of the cavity may be less than or equal to 30 millimetres, for example less than or equal to 28 millimetres, for example less than or equal to 16 millimetres.

[0358] The length of the cavity may be at least 3 millimetres, for example at least 10 millimetres, for example at least 15 millimetres.

[0359] The length of the cavity may be between 3 millimetres and 30 millimetres, for example between 3 millimetres and 28 millimetres, for example between 3 millimetres and 16 millimetres.

[0360] The length of the cavity may be between 10 millimetres and 30 millimetres, for example between 10 millimetres and 28 millimetres, for example between 10 millimetres and 16 millimetres.

[0361] The length of the cavity may be between 15 millimetres and 30 millimetres, for example between 15 millimetres and 28 millimetres, for example between 15 millimetres and 16 millimetres.

[0362] The width of the cavity may be less than or equal to 15 millimetres, for example less than or equal to 12 millimetres, for example less than or equal to 10 millimetres.

[0363] The width of the cavity may be at least 1 millimetre, for example at least 4 millimetres, for example at least 5 millimetres.

[0364] The width of the cavity may be between 1 millimetre and 15 millimetres, for example between 4 millimetres and 12 millimetres, for example between 1 millimetre and 10 millimetres.

[0365] The width of the cavity may be between 4 millimetres and 15 millimetres, for example between 4 millimetres and 12 millimetres, for example between 4 millimetres and 10 millimetres.

[0366] The width of the cavity may be between 5 millimetres and 15 millimetres, for example between 5 millimetres and 12 millimetres, for example between 5 millimetres and 10 millimetres.

[0367] The thickness of the cavity may be less than or equal to 10 millimetres, for example less than or equal to 5 millimetres, for example less than or equal to 4 millimetres.

[0368] The thickness of the cavity may be at least 0.1 millimetre, for example at least 0.5 millimetres, for example at least 1 millimetre, for example at least 1.5 millimetres, for example at least 2 millimetres.

[0369] The thickness of the cavity may be between 0.1 millimetres and 10 millimetres, for example between 0.1 millimetres and 5 millimetres, for example between 0.1 millimetres and 4 millimetres, for example between 0.1 millimetres and 3 millimetres.

[0370] The thickness of the cavity may be between 0.5 millimetres and 10 millimetres, for example between 0.5 millimetres and 5 millimetres, for example between 0.5 millimetres and 4 millimetres, for example between 0.5 millimetres and 3 millimetres.

[0371] The thickness of the cavity may be between 1 millimetre and 10 millimetres, for example between 1 millimetre and 5 millimetres, for example between 1 millimetre and 4 millimetres, for example between 1 millimetre and 3 millimetres. The thickness of the cavity may be between 1.5 millimetres and 10 millimetres, for example between 1.5 millimetres and 5 millimetres, for example between 1.5 millimetres and 4 millimetres, for example between 1.5 millimetres and 3 millimetres.

[0372] The thickness of the cavity may be between 2 millimetres and 10 millimetres, for example between 2 millimetres and 5 millimetres, for example between 2 millimetres and 4 millimetres, for example between 2 millimetres and 3 millimetres.

[0373] The volume of the cavity may be less than or equal to 4500 cubic millimetres, for example less than or equal to 1680 cubic millimetres, for example less than or equal to 320 cubic millimetres.

[0374] The volume of the cavity may be at least 0.3 cubic millimetres, for example at least 20 cubic millimetres, for example at least 110 cubic millimetres.

[0375] The volume of the cavity may be between 0.3 cubic millimetres and 4500 cubic millimetres, for example between 0.3 cubic millimetres and 1680 cubic millimetres, for example between 0.3 cubic millimetres and 320 cubic millimetres.

[0376] The volume of the cavity may be between 20 cubic millimetres and 4500 cubic millimetres, for example between 20 cubic millimetres and 1680 cubic millimetres, for example between 20 cubic millimetres and 320 cubic millimetres.

[0377] The volume of the cavity may be between 110 cubic millimetres and 4500 cubic millimetres, for example between 110 cubic millimetres and 1680 cubic millimetres, for example between 110 cubic millimetres and 320 cubic millimetres.

[0378] In one example of the present invention, for example the cavity has a length of 16 millimetres, a width of 10 millimetres, a thickness of 3 millimetres and, therefore, a volume of 480 cubic millimetres. The formed aerosol-generating substrate is positioned between the first planar external surface and the second planar external surface, typically within the cavity. For a formed substrate having a mass of 180 milligrams, the density of aerosol-generating substrate within the aerosol-generating article (i.e. the bulk density) is 0.375 grams per cubic centimetre.

[0379] In another example of the present invention, the cavity has a length of 26 millimetres, a width of 6 millimetres, a thickness of 2.7 millimetres and, therefore, a volume of 421 cubic millimetres. The formed aerosol-generating substrate is positioned between the first planar external surface and the second planar external surface, typically within the cavity. For a formed substrate having a mass of 158 milligrams, the density of aerosol-generating substrate within the aerosol-generating article (i.e. the bulk density) is 0.375 grams per cubic centimetre

[0380] In alternative preferred embodiments of the present invention, the aerosol-generating article may have a cylindrical shape. The aerosol-generating article may have a right-angled cylinder shape. The aerosol-generating article may have an elliptical cylinder shape. As used herein, the term “longitudinal” refers to the direction corresponding to the main longitudinal axis of the aerosol-generating article, which extends between upstream and downstream ends of the aerosol-generating article.

[0381] The aerosol-generating article comprises two ends: a proximal end through which aerosol exits the aerosol-generating article and is delivered to a user and a distal end. In use, a user may draw on the proximal end in order to inhale aerosol generated by the aerosol-generating article.

[0382] The proximal end may also be referred to as the mouth end or the downstream end and is downstream of the distal end. The distal end may also be referred to as the upstream end and is upstream of the proximal end.

[0383] During use, air is drawn through the aerosol-generating article in the longitudinal direction. The term “transverse” refers to the direction that is perpendicular to the longitudinal axis. Any reference to the “cross-section” of the aerosol-generating article or a component of the aerosolgenerating article refers to the transverse cross-section unless stated otherwise.

[0384] The term “length” denotes the dimension of a component of the aerosol-generating article in the longitudinal direction. For example, it may be used to denote the dimension of the rod or of the elongate tubular elements in the longitudinal direction.

[0385] The aerosol-generating article may comprise a rod of aerosol-generating substrate, as defined above.

[0386] The aerosol-generating article may also comprise a downstream segment between the rod of aerosol-generating substrate and the downstream end of the aerosol-generating article. The downstream segment may comprise one or more downstream elements. The one or more downstream elements may comprise one or more of: a mouthpiece element, an aerosol-cooling element, a hollow tubular segment, and a support element.

[0387] The aerosol-generating article may also comprise an upstream segment between the rod of aerosol-generating substrate and the upstream end of the aerosol-generating article. The upstream segment may comprise one or more upstream elements, for example an upstream plug.

[0388] The length of the aerosol-generating article may be less than or equal to 120 millimetres, for example less than or equal to 110 millimetres, for example less than or equal to 70 millimetres.

[0389] The length of the aerosol-generating article may be at least 5 millimetres, for example at least 30 millimetres, for example at least 40 millimetres.

[0390] The length of the aerosol-generating article may be between 5 millimetres and 120 millimetres, for example between 5 millimetres and 110 millimetres, for example between 5 millimetres and 70 millimetres.

[0391] The length of the aerosol-generating article may be between 30 millimetres and 120 millimetres, for example between 30 millimetres and 110 millimetres, for example between 30 millimetres and 70 millimetres. The length of the aerosol-generating article may be between 40 millimetres and 120 millimetres, for example between 40 millimetres and 110 millimetres, for example between 40 millimetres and 70 millimetres.

[0392] The diameter of the aerosol-generating article may be less than or equal to 12 millimetres, for example less than or equal to 10 millimetres, for example less than or equal to 8 millimetres.

[0393] The diameter of the aerosol-generating article may be at least 2 millimetres, for example at least 4 millimetres, for example at least 6 millimetres.

[0394] The diameter of the aerosol-generating article may be between 2 millimetres and 12 millimetres, for example between 2 millimetres and 10 millimetres, for example between 2 millimetres and 8 millimetres.

[0395] The diameter of the aerosol-generating article may be between 4 millimetres and 12 millimetres, for example between 4 millimetres and 10 millimetres, for example between 4 millimetres and 8 millimetres.

[0396] The diameter of the aerosol-generating article may be between 6 millimetres and 12 millimetres, for example between 6 millimetres and 10 millimetres, for example between 6 millimetres and 8 millimetres.

[0397] In an example, the length of the aerosol-generating article may be 45 millimetres and the diameter of the aerosol-generating article may be 7.5 millimetres.

[0398] The length of the rod of aerosol-generating substrate may be less than or equal to 115 millimetres, for example less than or equal to 107 millimetres, for example less than or equal to 68 millimetres.

[0399] The length of the rod of aerosol-generating substrate may be at least 4 millimetres, for example at least 34 millimetres, for example at least 48 millimetres.

[0400] The length of the rod of aerosol-generating substrate may be between 4 millimetres and 115 millimetres, for example between 4 millimetres and 107 millimetres, for example between 4 millimetres and 68 millimetres.

[0401] The length of the rod of aerosol-generating substrate may be between 34 millimetres and 115 millimetres, for example between 34 millimetres and 107 millimetres, for example between 34 millimetres and 68 millimetres.

[0402] The length of the rod of aerosol-generating substrate may be between 48 millimetres and 115 millimetres, for example between 48 millimetres and 107 millimetres, for example between 48 millimetres and 68 millimetres.

[0403] The diameter of the rod of aerosol-generating substrate may be less than or equal to 5 millimetres, for example less than or equal to 4 millimetres, for example less than or equal to 3 millimetres. The diameter of the rod of aerosol-generating substrate may be at least 1 millimetre, for example at least 1.5 millimetres, for example at least 2 millimetres.

[0404] The diameter of the rod of aerosol-generating substrate may be between 1 millimetre and 5 millimetres, for example between 1 millimetre and 4 millimetres, for example between 1 millimetre and 3 millimetres.

[0405] The diameter of the rod of aerosol-generating substrate may be between 1.5 millimetres and 5 millimetres, for example between 1.5 millimetres and 4 millimetres, for example between 1.5 millimetres and 3 millimetres.

[0406] The diameter of the rod of aerosol-generating substrate may be between 2 millimetres and 5 millimetres, for example between 2 millimetres and 4 millimetres, for example between 2 millimetres and 3 millimetres.

[0407] In an example, the length of the rod of aerosol-generating substrate may be 12 millimetres and the diameter of the rod of aerosol-generating substrate may be 7 millimetres.

[0408] In alternative preferred embodiments of the present invention, the aerosol-generating article comprises a container, the container comprising a first wall and a second wall together defining a substrate compartment, wherein the aerosol-generating substrate is provided in the substrate compartment.

[0409] The first wall may comprise a different material to the second wall. This provision may advantageously allow the first and second wall to have different properties tailored for different functions. For example, the first and second walls may be configured to have different porosities, different thermal conductivities, or different stiffnesses.

[0410] The first wall may comprise a flexible material, such as a flexible cellulosic material. The second wall may have a higher stiffness than the first wall.

[0411] At least a portion of the first or second wall may be porous.

[0412] The container as defined above may be in the form of a pouch.

[0413] In alternative embodiments of the invention, the aerosol-generating article is configured for use with a dielectrically heated aerosol-generating device, as defined below. The aerosolgenerating article comprises a first electrode and a second electrode, the first electrode and the second electrode being spaced apart to form a substrate cavity. The aerosol-generating substrate is disposed in the substrate cavity between the first electrode and the second electrode.

[0414] As defined below, the present invention provides an aerosol-generating device comprising an aerosol-generating article including an aerosol-generating substrate according to the present invention, as described above, and a heating element.

[0415] The aerosol-generating substrate of the present invention may be advantageously heated using different heating methods, such as conductive heating, convective heating, induction heating, dielectric or microwave heating, or any combination thereof. In an embodiment of the invention, the aerosol-generating device comprises a cavity dimensioned to receive at least a portion of an aerosol-generating article. The aerosol-generating device comprises a heater or heating means, a power source for supplying power to the heater or heating means, and a controller to control a supply of power to the heater or heating means. The aerosol-generating device is configured to heat at the aerosol-generating substrate within the aerosol-generating article to form an aerosol, for example an inhalable aerosol.

[0416] The cavity of the aerosol-generating device may comprise an opening into which an end, such as a longitudinal end, of the aerosol-generating article can be inserted. The cavity of the aerosol-generating device may have any suitable cross-sectional shape. For example, the cavity of the aerosol-generating device may have a rectangular transverse cross-section, for example a rectangular cross-section having opposing top and bottom sides that are greater in length than left and right sides.

[0417] Preferably, at least one internal surface of the cavity of the aerosol-generating device is a heating surface configured to heat the aerosol-generating article. The heating surface may comprise a heater, for example a resistance heater, or an infra-red heater, or a susceptor configured to be heated by engagement with an inductor. The heating surface may comprise an inductor, for example the surface may comprise a coil arranged to generate a fluctuating electromagnetic field within a space of the cavity of the aerosol-generating device. The heating surface may be a surface that is permeable to a fluctuating electromagnetic field, such that an inductor arranged outside the cavity can project a fluctuating electromagnetic field through the heating surface to engage with a susceptor arranged within the cavity of the aerosol-generating device.

[0418] In an embodiment of the invention, the aerosol-generating article may comprise one or more susceptor materials. In aerosol-generating articles comprising a frame, the frame may comprise one or more susceptor materials. The one more susceptor materials may be in thermal contact with the aerosol-generating substrate. The one more susceptor materials may be in thermal contact with the airflow passage. The one more susceptor materials may be in thermal contact with the cavity. The one or more susceptor materials may be positioned in or on an inner surface of the frame. The one or more susceptor materials may be incorporated within the material of the frame. For example, the one or more susceptor material may be incorporated within a peripheral wall of the frame. Advantageously, the presence of one or more susceptor materials may allow the aerosol-generating article, and thus the aerosol-generating substrate, to be heated by engagement with a fluctuating electromagnetic field formed by an inductor.

[0419] The one or more susceptor materials may be one or more particles, strips, threads, or wires of susceptor material. The one or more susceptor materials may be one or more sheets or layers of susceptor material. The one of more sheets or layers of susceptor material may be in the form of a mesh of susceptor material.

[0420] The susceptor material, in whatever form, may comprise one or more materials selected from the list consisting of: aluminium, iron and iron alloys, nickel and nickel alloys, cobalt alloys, stainless steel alloys, copper alloys, carbon, expanded carbon, and graphite.

[0421] In an embodiment of the invention, the aerosol-generating device includes a planar heater that is configured to heat a planar layer of an aerosol-generating article. The larger surface area of the planar heater enables good contact between the heater and the planar layer of the aerosolgenerating article, and thus provides optimum heating of aerosol-generating substrate within the aerosol-generating article.

[0422] In embodiments of the invention, the aerosol-generating device is configured to heat the aerosol-generating substrate of the aerosol-generating article by dielectric or microwave heating.

[0423] In one embodiment, the aerosol-generating device may comprise a first electrode, a second electrode and a controller that is configured to connect to the first electrode and the second electrode. The first electrode and the second electrode may form a capacitor with a portion of aerosol-generating substrate within the aerosol-generating article of the aerosolgenerating device. The controller may be configured to supply an alternating voltage to the first electrode and the second electrode for dielectrically heating the aerosol-generating substrate.

[0424] Such an aerosol-generating device is configured to give rise to dielectric heating of the aerosol-generating substrate due to the alternating electromagnetic filed between the first electrode and the second electrode on supply of the alternating voltage to the first electrode and the second electrode. Dielectric heating can be uniform within a volume of aerosol-generating substrate, without the creation of hot spots. In particular, dielectric heating reduces the likelihood of combustion of substrate in contact with the first electrode and the second electrode compared to a conventional heater that transfers heat to the substrate via conduction.

[0425] In another embodiment, the aerosol-generating device comprises: a substrate cavity configured to receive an aerosol-generating substrate; and an electromagnetic field generator configured to generate a radio frequency (RF) electromagnetic field in the substrate cavity, the electromagnetic field generator comprising a solid state RF transistor.

[0426] The aerosol-generating device can give rise to dielectric heating of the aerosol-generating substrate. Dielectric heating can be uniform within a volume of aerosol-generating substrate, without the creation of hot spots. The heating also requires no contact between a heating element and the aerosol-generating substrate. This means that there is no need to clean a heating element that has a build-up of aerosol residue on it. The device allows for considerable design flexibility in terms of the shape, volume and composition of the aerosol-generating substrate and correspondingly the shape and volume of the substrate cavity. The use of a solid state RF transducer allows the aerosol-generating device to be made compact. The production of a aerosol-generating device that can fit easily into one hand of a user is possible. The conventional means for producing RF frequency radiation for heating, such as in domestic microwave ovens, is a magnetron. Magnetrons are bulky and require very high voltages to operate, making them unsuitable for a handheld device. Furthermore, magnetrons have a relatively unstable frequency output and have a relatively short service life. A RF transistor can provide for consistent operation over many more usage cycles and requires much lower operating voltages.

[0427] Advantageously, the solid state RF transistor is configured to generate and amplify the RF electromagnetic field. Using a single transistor to provide both the generating and amplification of the RF electromagnetic field allows for a compact device to be made.

[0428] As used herein, radio frequency (RF) means a frequency between 3Hz and 3 THz, and includes microwaves.

[0429] The invention is defined in the claims. However, below there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0430] EX1. A porous aerosol-generating substrate for an aerosol-generating article, the porous aerosol-generating substrate comprising: a particulate plant material; at least 10 percent by weight of aerosol former, on a dry weight basis; and at least 1 percent by weight of binder, on a dry weight basis; wherein the porous aerosol-generating substrate is formed as a one-piece unit having a length, a width and a thickness, wherein each of the length, the width and the thickness is at least 1 millimetre, and wherein one of the length, the width and thickness is at least 3 millimetres.

[0431] EX2. The porous aerosol-generating substrate of example EX1 , wherein the particulate plant material comprises a non-tobacco plant material.

[0432] EX3. The porous aerosol-generating substrate of example EX2, wherein the nontobacco plant material comprises one or more of: tea (such as black tea), rosehip seeds, apple fibres, lemon balm stems, coffee, star anise, rooibos, lavender, clove, peppermint, chamomile, rosemary, eucalyptus, ginger, dill seed, thyme, oregano and cumin.

[0433] EX4. The porous aerosol-generating substrate of any one of examples EX1 , EX2 or EX3, wherein the non-tobacco plant material comprises a cannabinoid compound.

[0434] EX5. The porous aerosol-generating substrate of example EX4, wherein the cannabinoid compound is a naturally derived cannabinoid compound. EX6. The porous aerosol-generating substrate of example EX4, wherein the cannabinoid compound is a synthetically derived cannabinoid compound.

[0435] EX7. The porous aerosol-generating substrate of any one of examples EX4, EX5 or EX6, wherein the cannabinoid compound comprises one or more of tetrahydrocannabinol (THC), tetrahydrocannabinolic acid (THCA), cannabidiol (CBD), cannabidiolic acid (CBDA), cannabinol (CBN), cannabigerol (CBG), cannabigerol monomethyl ether (CBGM), cannabivarin (CBV), cannabidivarin (CBDV), tetrahydrocannabivarin (THCV), cannabichromene (CBC), cannabicyclol (CBL), cannabichromevarin (CBCV), cannabigerovarin (CBGV), cannabielsoin (CBE), cannabicitran (CBT).

[0436] EX8. The porous aerosol-generating substrate of any one of examples EX1 to EX7, wherein the particulate plant material comprises tobacco.

[0437] EX9. The porous aerosol-generating substrate of example EX8, wherein the tobacco comprises tobacco material from one or more of: Bright tobacco, dark tobacco, aromatic tobacco and filler tobacco.

[0438] EX10. The porous aerosol-generating substrate of any one of examples EX1 to EX9, wherein the aerosol former content is at least 20 percent by weight, on a dry weight basis.

[0439] EX11. The porous aerosol-generating substrate of any one of examples EX1 to EX10, wherein the aerosol former content is at least 30 percent by weight, on a dry weight basis.

[0440] EX12. The porous aerosol-generating substrate of any one of examples EX1 to EX11, wherein the aerosol former content is at least 35 percent by weight, on a dry weight basis.

[0441] EX13. The porous aerosol-generating substrate of any one of examples EX1 to EX12, wherein the aerosol former content is at least 40 percent by weight, on a dry weight basis.

[0442] EX14. The porous aerosol-generating substrate of any one of examples EX1 to EX13, wherein the aerosol former content is at least 45 percent by weight, on a dry weight basis.

[0443] EX15. The porous aerosol-generating substrate of any one of examples EX1 to EX14, wherein the aerosol former content is less than or equal to 60 percent by weight, on a dry weight basis.

[0444] EX16. The porous aerosol-generating substrate of any one of examples EX1 to EX15, wherein the aerosol former content is less than or equal to 50 percent by weight, on a dry weight basis.

[0445] EX17. The porous aerosol-generating substrate of any one of examples EX1 to EX16, wherein the aerosol former comprises glycerin or propylene glycol, or a mixture of glycerin and propylene glycol.

[0446] EX18. The porous aerosol-generating substrate of any one of examples EX1 to EX17, wherein the aerosol-generating substrate has a bulk density of less than or equal to 0.55 grams per cubic centimetre. EX19. The porous aerosol-generating substrate of example EX18, wherein the substrate bulk density is less than or equal to 0.53 grams per cubic centimetre.

[0447] EX20. The porous aerosol-generating substrate of example EX18 or example EX19, wherein the substrate bulk density is less than or equal to 0.50 grams per cubic centimetre.

[0448] EX21. The porous aerosol-generating substrate of example EX18, example EX19 or example EX20, wherein the substrate bulk density is less than or equal to 0.45 grams per cubic centimetre, for example wherein the substrate bulk density is less than or equal to 0.43 grams per cubic centimetre.

[0449] EX22. The porous aerosol-generating substrate of any one of examples EX18 to EX21 , wherein the substrate bulk density is less than or equal to 0.40 grams per cubic centimetre.

[0450] EX23. The porous aerosol-generating substrate of any one of examples EX18 to EX23, wherein the substrate bulk density is less than or equal to 0.37 grams per cubic centimetre.

[0451] EX24. The porous aerosol-generating substrate of any one of examples EX18 to EX24, wherein the substrate bulk density is at least 0.25 grams per cubic centimetre, for example wherein the substrate bulk density is at least 0.30 grams per cubic centimetre.

[0452] EX25. The porous aerosol-generating substrate of any one of examples EX18 to EX26, wherein the substrate bulk density is at least 0.35 grams per cubic centimetre.

[0453] EX26. The porous aerosol-generating substrate of any one of examples EX1 to EX25, wherein the aerosol-generating substrate has a porosity of at least 60 percent.

[0454] EX27. The porous aerosol-generating substrate of any one of examples EX1 to EX26, wherein the aerosol-generating substrate has a plant material content of at least 20 percent by weight, on a dry weight basis.

[0455] EX28. The porous aerosol-generating substrate of example EX27, wherein the plant material content is at least 25 percent by weight, on a dry weight basis.

[0456] EX29. The porous aerosol-generating substrate of example EX27 or example EX28, wherein the plant material content is at least 30 percent by weight, on a dry weight basis.

[0457] EX30. The porous aerosol-generating substrate of example EX27, example EX28 or example EX29, wherein the plant material content is at least 40 percent by weight, on a dry weight basis.

[0458] EX31 . The porous aerosol-generating substrate of any one of examples EX27 to EX30, wherein the plant material content is at least 45 percent by weight, on a dry weight basis.

[0459] EX32. The porous aerosol-generating substrate of any one of examples EX27 to EX31 , wherein the plant material content is less than or equal to 65 percent by weight, on a dry weight basis. EX33. The porous aerosol-generating substrate of any one of examples EX27 to EX32, wherein the plant material content is less than or equal to 60 percent by weight, on a dry weight basis.

[0460] EX34. The porous aerosol-generating substrate of any one of examples EX27 to EX33, wherein the plant material content is less than or equal to 55 percent by weight, on a dry weight basis.

[0461] EX35. The porous aerosol-generating substrate of any one of examples EX1 to EX34, wherein the aerosol-generating substrate comprises nicotine.

[0462] EX36. The porous aerosol-generating substrate of example EX35, wherein the nicotine comprises nicotine, a nicotine base or a nicotine salt.

[0463] EX37. The porous aerosol-generating substrate of example EX35 or example EX36, wherein the nicotine comprises a natural nicotine or a synthetic nicotine.

[0464] EX38. The porous aerosol-generating substrate of any one of examples EX1 to EX37, wherein the binder comprises a cellulose binder.

[0465] EX39. The porous aerosol-generating substrate of example EX38, wherein the binder comprises one or more of hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), ethylcellulose (EC), hydroxyethyl methyl cellulose (HEMC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC) and hydroxypropyl cellulose (HPC).

[0466] EX40. The porous aerosol-generating substrate of example EX38 or example EX39, wherein the aerosol-generating substrate has a cellulose binder content of at least 1 percent by weight, on a dry weight basis.

[0467] EX41. The porous aerosol-generating substrate of example EX40, wherein the cellulose binder content is at least 2 percent by weight, on a dry weight basis.

[0468] EX42. The porous aerosol-generating substrate of example EX40 or example EX41 , wherein the cellulose binder content is at least 3 percent by weight, on a dry weight basis.

[0469] EX43. The porous aerosol-generating substrate of example EX40, example EX41 or example EX42, wherein the cellulose binder content is less than or equal to 10 percent by weight, on a dry weight basis.

[0470] EX44. The porous aerosol-generating substrate of any one of examples EX1 to EX43, wherein the binder comprises a non-cellulose binder.

[0471] EX45. The porous aerosol-generating substrate of example EX44, wherein the noncellulose binder comprises one or more of agar, guar gum, xanthan gum, Arabic gum, locust bean gum, pectin, carrageenan, starch and alginate.

[0472] EX46. The porous aerosol-generating substrate of example EX44 or example EX45, wherein the aerosol-generating substrate has a non-cellulose binder content of at least 0.2 percent by weight, on a dry weight basis. EX47. The porous aerosol-generating substrate of example EX46, wherein the noncellulose binder content is at least 0.4 percent by weight, on a dry weight basis.

[0473] EX48. The porous aerosol-generating substrate of example EX46 or example EX47, wherein the non-cellulose binder content is at least 0.6 percent by weight, on a dry weight basis.

[0474] EX49. The porous aerosol-generating substrate of example EX46, example EX47 or example EX48, wherein the non-cellulose binder content is at least 0.8 percent by weight, on a dry weight basis.

[0475] EX50. The porous aerosol-generating substrate of any one of examples EX46 to EX49, wherein the non-cellulose binder content is less than or equal to 2 percent by weight, on a dry weight basis.

[0476] EX51. The porous aerosol-generating substrate of any one of examples EX46 to EX50, wherein the non-cellulose binder content is less than or equal to 1.8 percent by weight, on a dry weight basis.

[0477] EX52. The porous aerosol-generating substrate of any one of examples EX46 to EX51, wherein the non-cellulose binder content is less than or equal to 1.6 percent by weight, on a dry weight basis.

[0478] EX53. The porous aerosol-generating substrate of any one of examples EX46 to EX52, wherein the non-cellulose binder content is less than or equal to 1.4 percent by weight, on a dry weight basis.

[0479] EX54. The porous aerosol-generating substrate of any one of examples EX1 to EX53, comprising a cellulose based strengthening agent.

[0480] EX55. The porous aerosol-generating substrate of example EX54, wherein the cellulose based strengthening agent comprises a fibrous material.

[0481] EX56. The porous aerosol-generating substrate of example EX55, wherein the fibrous material comprises a tobacco fibrous material.

[0482] EX57. The porous aerosol-generating substrate of example EX55, wherein the fibrous material comprises a non-tobacco fibrous material.

[0483] EX58. The porous aerosol-generating substrate of example EX57, wherein the nontobacco fibrous material comprises one or more of cellulose fibres, soft-wood fibres, hard-wood fibres, jute fibres and combinations thereof.

[0484] EX59. The porous aerosol-generating substrate of any one of examples EX54 to EX58, wherein the cellulose based strengthening agent comprises microcrystalline cellulose.

[0485] EX60. The porous aerosol-generating substrate of any one of examples EX54 to EX59, wherein the cellulose based strengthening agent comprises cellulose powder. EX61 . The porous aerosol-generating substrate of any one of examples EX54 to EX60, wherein the aerosol-generating substrate has a cellulose based strengthening agent content of at least 0.5 percent by weight, on a dry weight basis.

[0486] EX62. The porous aerosol-generating substrate of example EX61 , wherein the cellulose based strengthening agent content is at least 1 percent by weight, on a dry weight basis.

[0487] EX63. The porous aerosol-generating substrate of example EX61 or example EX62, wherein the cellulose based strengthening agent content is at least 5 percent by weight, on a dry weight basis.

[0488] EX64. The porous aerosol-generating substrate of example EX61 , example EX62 or example EX63, wherein the cellulose based strengthening agent content is at least 10 percent by weight, on a dry weight basis.

[0489] EX65. The porous aerosol-generating substrate of any one of examples EX61 to EX64, wherein the cellulose based strengthening agent content is less than or equal to 50 percent by weight, on a dry weight basis.

[0490] EX66. The porous aerosol-generating substrate of any one of examples EX61 to EX65, wherein the cellulose based strengthening agent content is less than or equal to 40 percent by weight, on a dry weight basis.

[0491] EX67. The porous aerosol-generating substrate of any one of examples EX61 to EX66, wherein the cellulose based strengthening agent content is less than or equal to 30 percent by weight, on a dry weight basis.

[0492] EX68. The porous aerosol-generating substrate of any one of examples EX61 to EX67, wherein the cellulose based strengthening agent is less than or equal to 20 percent by weight, on a dry weight basis.

[0493] EX69. The porous aerosol-generating substrate of any one of examples EX1 to EX68, having a porosity of at least 60 percent.

[0494] EX70. The porous aerosol-generating substrate of example EX69, wherein the porosity is at least 70 percent.

[0495] EX71. The porous aerosol-generating substrate of example EX69 or example EX70, wherein the porosity is less than or equal to 98 percent.

[0496] EX72. The porous aerosol-generating substrate of example EX69, example EX70 or example EX71 , wherein the porosity is less than or equal to 97 percent.

[0497] EX73. The porous aerosol-generating substrate of any one of examples EX1 to EX72, wherein the substrate has a mass of at least 50 milligrams.

[0498] EX74. The porous aerosol-generating substrate of example EX73, wherein the substrate mass is at least 75 milligrams. EX75. The porous aerosol-generating substrate of example EX73 or example EX74, wherein the substrate mass is at least 100 milligrams.

[0499] EX76. The porous aerosol-generating substrate of example EX73, example EX74 or example EX75, wherein the substrate mass is at least 150 milligrams.

[0500] EX77. The porous aerosol-generating substrate of any one of examples EX73 to EX76, wherein the substrate mass is less than or equal to 250 milligrams.

[0501] EX78. The porous aerosol-generating substrate of any one of examples EX73 to EX77, wherein the substrate mass is less than or equal to 200 milligrams.

[0502] EX79. The porous aerosol-generating substrate of any one of examples EX73 to EX78, wherein the substrate mass is less than or equal to 190 milligrams.

[0503] EX80. The porous aerosol-generating substrate of any one of examples EX1 to EX79, wherein the aerosol-generating substrate has a quadrilaterally-faced hexahedron shape.

[0504] EX81 . The porous aerosol-generating substrate of example EX80, wherein the aerosolgenerating substrate has a cuboid shape.

[0505] EX82. The porous aerosol-generating substrate of example EX80 or example EX81 , wherein the aerosol-generating substrate has a rectangular cuboid shape.

[0506] EX83. The porous aerosol-generating substrate of example EX80, example EX81 or example EX82, wherein the aerosol-generating substrate has a parallelepiped shape.

[0507] EX84. The porous aerosol-generating substrate of any one of examples EX1 to EX79, wherein the aerosol-generating substrate has a cylindrical shape.

[0508] EX85. The porous aerosol-generating substrate of any one of examples EX1 to EX79, wherein the aerosol-generating substrate has an elliptical cylinder shape.

[0509] EX86. The porous aerosol-generating substrate of any one of examples EX1 to EX79, wherein the aerosol-generating substrate has a spherical shape.

[0510] EX87. An aerosol-generating article comprising the porous aerosol-generating substrate of any one of examples EX1 to EX86.

[0511] EX88. An aerosol-generating device comprising a heating element and the aerosolgenerating article of example EX87.

[0512] EX89. A method of manufacturing the porous aerosol-generating substrate of any one of examples EX1 to EX86, the method comprising: mixing the binder and the aerosol former; adding water to the mixture comprising the binder and the aerosol former to form a slurry; adding the plant material to the slurry; and drying the slurry comprising the plant material to form a solid porous aerosol-generating substrate.

[0513] EX90. The method of example EX89, wherein the step of drying the slurry to form the solid porous aerosol-generating substrate comprises lyophilising or freeze-drying the slurry. EX91. The method of example EX89 or example EX90, comprising cutting the solid porous aerosol-generating substrate to the required dimensions.

[0514] EX92. The method of example EX90 or example EX91 , comprising drying the slurry in a mould to form the solid porous aerosol-generating substrate in the required dimensions.

[0515] EX93. A porous aerosol-generating substrate for an aerosol-generating article, the porous aerosol-generating substrate comprising: an active agent and / or a flavourant; a particulate cellulose based strengthening agent; an aerosol former; and a binder; wherein the aerosol-generating substrate has an aerosol former content of at least 10 percent by weight, on a dry weight basis, and a binder content of at least 1 percent, on a dry weight basis; wherein the porous aerosol-generating substrate is formed as a one-piece unit having a length, a width and a thickness; wherein each of the length, the width and the thickness is at least 1 millimetre and at least one of the length, the width and the thickness is at least 3 millimetres.

[0516] EX94. The porous aerosol-generating substrate of example EX93, wherein the aerosol former content is at least 20 percent by weight, on a dry weight basis.

[0517] EX95. The porous aerosol-generating substrate of example EX93 or example EX94, wherein the aerosol former content is at least 30 percent by weight, on a dry weight basis.

[0518] EX96. The porous aerosol-generating substrate of example EX93, example EX94 or example EX95, wherein the aerosol former content is at least 35 percent by weight, on a dry weight basis.

[0519] EX97. The porous aerosol-generating substrate of any one of examples EX93 to EX96, wherein the aerosol former content is at least 40 percent by weight, on a dry weight basis.

[0520] EX98. The porous aerosol-generating substrate of any one of examples EX93 to EX97, wherein the aerosol former content is at least 45 percent by weight, on a dry weight basis.

[0521] EX99. The porous aerosol-generating substrate of any one of examples EX93 to EX98, wherein the aerosol former content is less than or equal to 60 percent by weight, on a dry weight basis.

[0522] EX100. The porous aerosol-generating substrate of any one of examples EX93 to EX99, wherein the aerosol former content is less than or equal to 50 percent by weight, on a dry weight basis.

[0523] EX101. The porous aerosol-generating substrate of any one of examples EX93 to EX100, wherein the aerosol former comprises glycerin or propylene glycol, or a mixture of glycerin and propylene glycol.

[0524] EX102. The porous aerosol-generating substrate of any one of examples EX93 to EX101 , wherein the aerosol-generating substrate has a bulk density of less than or equal to 0.55 grams per cubic centimetre. EX103. The porous aerosol-generating substrate of example EX102, wherein the substrate bulk density is less than or equal to 0.53 grams per cubic centimetre.

[0525] EX104. The porous aerosol-generating substrate of example EX102 or example EX103, wherein the substrate bulk density is less than or equal to 0.50 grams per cubic centimetre.

[0526] EX105. The porous aerosol-generating substrate of example EX102, example EX103 or example EX104, wherein the substrate bulk density is less than or equal to 0.45 grams per cubic centimetre, for example wherein the substrate bulk density is less than or equal to 0.43 grams per cubic centimetre.

[0527] EX106. The porous aerosol-generating substrate of any one of examples EX102 to

[0528] EX105, wherein the substrate bulk density is less than or equal to 0.40 grams per cubic centimetre.

[0529] EX107. The porous aerosol-generating substrate of any one of examples EX102 to EX106, wherein the substrate bulk density is less than or equal to 0.37 grams per cubic centimetre.

[0530] EX108. The porous aerosol-generating substrate of any one of examples EX102 to

[0531] EX107, wherein the substrate bulk density is at least 0.25 grams per cubic centimetre, for example wherein the substrate bulk density is at least 0.30 grams per cubic centimetre.

[0532] EX109. The porous aerosol-generating substrate of any one of examples EX102 to

[0533] EX108, wherein the substrate bulk density is at least 0.35 grams per cubic centimetre.

[0534] EX110. The porous aerosol-generating substrate of any one of examples EX93 to EX109, wherein the aerosol-generating substrate has a porosity of at least 60 percent.

[0535] EX111. The porous aerosol-generating substrate of any one of example EX93 to EX110, wherein the active agent comprises nicotine.

[0536] EX112. The porous aerosol-generating substrate of example EX111 , wherein the nicotine comprises nicotine, a nicotine base or a nicotine salt.

[0537] EX113. The porous aerosol-generating substrate of example EX111 or EX112, wherein the nicotine comprises a natural nicotine or a synthetic nicotine.

[0538] EX114. The porous aerosol-generating substrate of any one of examples EX93 to EX113, wherein the active agent comprises one or more cannabinoid compounds selected from the group consisting of: tetrahydrocannabinol (THC), tetrahydrocannabinolic acid (THCA), cannabidiol (CBD), cannabidiolic acid (CBDA), cannabinol (CBN), cannabigerol (CBG), cannabigerol monomethyl ether (CBGM), cannabivarin (CBV), cannabidivarin (CBDV), tetrahydrocannabivarin (THCV), cannabichromene (CBC), cannabicyclol (CBL), cannabichromevarin (CBCV), cannabigerovarin (CBGV), cannabielsoin (CBE), cannabicitran (CBT) and combinations thereof.

[0539] EX115. The porous aerosol-generating substrate of any one of examples EX93 to EX114, wherein the flavourant comprises one or more of: one or more essential oils such as eugenol, peppermint oil and spearmint oil; one or both of menthol and eugenol; one or both of anethole and linalool.

[0540] EX116. The porous aerosol-generating substrate of any one of examples EX93 to EX115, wherein the particulate cellulose based strengthening agent comprises a fibrous material.

[0541] EX117. The porous aerosol-generating substrate of example EX116, wherein the fibrous material comprises a non-tobacco fibrous material.

[0542] EX118. The porous aerosol-generating substrate of example EX117, wherein the nontobacco fibrous material comprises one or more of cellulose fibres, soft-wood fibres, hard-wood fibres, jute fibres and combinations thereof.

[0543] EX119. The porous aerosol-generating substrate of any one of examples EX93 to EX118, wherein the particulate cellulose based strengthening agent comprises microcrystalline cellulose.

[0544] EX120. The porous aerosol-generating substrate of any one of examples EX93 to EX119, wherein the particulate cellulose based strengthening agent comprises cellulose powder.

[0545] EX121. The porous aerosol-generating substrate of any one of examples EX93 to EX120, wherein the aerosol-generating substrate has a particulate cellulose based strengthening agent content of at least 0.5 percent by weight, on a dry weight basis.

[0546] EX122. The porous aerosol-generating substrate of example EX121 , wherein the particulate cellulose based strengthening agent content is at least 1 percent by weight, on a dry weight basis.

[0547] EX123. The porous aerosol-generating substrate of example EX121 or EX122, wherein the particulate cellulose based strengthening agent content is at least 5 percent by weight, on a dry weight basis.

[0548] EX124. The porous aerosol-generating substrate of example EX121 , example EX122 or example EX123, wherein the particulate cellulose based strengthening agent content is at least 10 percent by weight, on a dry weight basis.

[0549] EX125. The porous aerosol-generating substrate of any one of examples EX121 to EX124, wherein the particulate cellulose based strengthening agent content is less than or equal to 50 percent by weight, on a dry weight basis.

[0550] EX126. The porous aerosol-generating substrate of any one of examples EX121 to EX125, wherein the particulate cellulose based strengthening agent content is less than or equal to 40 percent by weight, on a dry weight basis.

[0551] EX127. The porous aerosol-generating substrate of any one of examples EX121 to EX126, wherein the particulate cellulose based strengthening agent content is less than or equal to 30 percent by weight, on a dry weight basis. EX128. The porous aerosol-generating substrate of any one of examples EX121 to 127, wherein the particulate cellulose based strengthening agent is less than or equal to 20 percent by weight, on a dry weight basis.

[0552] EX129. The porous aerosol-generating substrate of any one of examples EX93 to EX128, wherein the binder comprises a cellulose binder.

[0553] EX130. The porous aerosol-generating substrate of example EX129, wherein the binder comprises one or more of hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), ethylcellulose (EC), hydroxyethyl methyl cellulose (HEMC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC) and hydroxypropyl cellulose (HPC).

[0554] EX131. The porous aerosol-generating substrate of example EX129 or example EX130, wherein the aerosol-generating substrate has a cellulose binder content of at least 1 percent by weight, on a dry weight basis.

[0555] EX132. The porous aerosol-generating substrate of example EX131 , wherein the cellulose binder content is at least 2 percent by weight, on a dry weight basis.

[0556] EX133. The porous aerosol-generating substrate of example EX131 or example EX132, wherein the cellulose binder content is at least 3 percent by weight, on a dry weight basis.

[0557] EX134. The porous aerosol-generating substrate of example EX131 , example EX132 or example EX133, wherein the cellulose binder content is less than or equal to 10 percent by weight, on a dry weight basis.

[0558] EX135. The porous aerosol-generating substrate of any one of examples EX93 to EX134, wherein the binder comprises a non-cellulose binder.

[0559] EX136. The porous aerosol-generating substrate of example EX135, wherein the noncellulose binder comprises one or more of agar, guar gum, xanthan gum, Arabic gum, locust bean gum, pectin, carrageenan, starch and alginate.

[0560] EX137. The porous aerosol-generating substrate of example EX135 or example EX136, wherein the aerosol-generating substrate has a non-cellulose binder content of at least 0.2 percent by weight, on a dry weight basis.

[0561] EX138. The porous aerosol-generating substrate of example EX137, wherein the non- cellulose binder content is at least 0.4 percent by weight, on a dry weight basis.

[0562] EX139. The porous aerosol-generating substrate of example EX137 or example EX138, wherein the non-cellulose binder content is at least 0.6 percent by weight, on a dry weight basis.

[0563] EX140. The porous aerosol-generating substrate of example EX137, example EX138 or example EX139, wherein the non-cellulose binder content is at least 0.8 percent by weight, on a dry weight basis. EX141. The porous aerosol-generating substrate of any one of examples EX137 to EX140, wherein the non-cellulose binder content is less than or equal to 2 percent by weight, on a dry weight basis.

[0564] EX142. The porous aerosol-generating substrate of any one of examples EX137 to EX141 , wherein the non-cellulose binder content is less than or equal to 1.8 percent by weight, on a dry weight basis.

[0565] EX143. The porous aerosol-generating substrate of any one of examples EX137 to EX142, wherein the non-cellulose binder content is less than or equal to 1.6 percent by weight, on a dry weight basis.

[0566] EX144. The porous aerosol-generating substrate of any one of examples EX137 to EX143, wherein the non-cellulose binder content is less than or equal to 1.4 percent by weight, on a dry weight basis.

[0567] EX145. The porous aerosol-generating substrate of any one of examples EX93 to EX144, having a porosity of at least 60 percent.

[0568] EX146. The porous aerosol-generating substrate of example EX145, wherein the porosity is at least 70 percent.

[0569] EX147. The porous aerosol-generating substrate of example EX145 or example EX146, wherein the porosity is less than or equal to 98 percent.

[0570] EX148. The porous aerosol-generating substrate of example EX145, example EX146 or example EX147, wherein the porosity is less than or equal to 97 percent.

[0571] EX149. The porous aerosol-generating substrate of any one of examples EX93 to EX148, wherein the substrate has a mass of at least 50 milligrams.

[0572] EX150. The porous aerosol-generating substrate of example EX149, wherein the substrate mass is at least 75 milligrams.

[0573] EX151. The porous aerosol-generating substrate of example EX149 or example EX150, wherein the substrate mass is at least 100 milligrams.

[0574] EX152. The porous aerosol-generating substrate of example EX149, example EX150 or example EX151 , wherein the substrate mass is at least 150 milligrams.

[0575] EX153. The porous aerosol-generating substrate of any one of examples EX149 to EX152, wherein the substrate mass is less than or equal to 250 milligrams.

[0576] EX154. The porous aerosol-generating substrate of any one of examples EX149 to EX153, wherein the substrate mass is less than or equal to 200 milligrams.

[0577] EX155. The porous aerosol-generating substrate of any one of examples EX149 to EX154, wherein the substrate mass is less than or equal to 190 milligrams.

[0578] EX156. The porous aerosol-generating substrate of any one of examples EX93 to EX155, wherein the porous aerosol-generating substrate has a quadrilaterally-faced hexahedron shape. EX157. The porous aerosol-generating substrate of example EX156, wherein the porous aerosol-generating substrate has a cuboid shape.

[0579] EX158. The porous aerosol-generating substrate of example EX156 or example EX157, wherein the porous aerosol-generating substrate has a rectangular cuboid shape.

[0580] EX159. The porous aerosol-generating substrate of example EX156, example EX157 or example EX158, wherein the porous aerosol-generating substrate has a parallelepiped shape.

[0581] EX160. The porous aerosol-generating substrate of any one of examples EX93 to EX155, wherein the porous aerosol-generating substrate has a cylindrical shape.

[0582] EX161. The porous aerosol-generating substrate of any one of examples EX93 to EX155, wherein the porous aerosol-generating substrate has an elliptical cylinder shape.

[0583] EX162. The porous aerosol-generating substrate of any one of examples EX93 to EX155, wherein the porous aerosol-generating substrate has a spherical shape.

[0584] EX163. An aerosol-generating article comprising the porous aerosol-generating substrate of any one of examples EX93 to EX163.

[0585] EX164. An aerosol-generating device comprising a heating element and the aerosolgenerating article of example EX163.

[0586] EX165. A method of manufacturing the porous aerosol-generating substrate of any one of examples EX93 to EX162, the method comprising: mixing the binder and the aerosol former; adding water to the mixture comprising the binder and the aerosol former to form a slurry; adding the active agent and / or the flavourant, and the particulate cellulose based strengthening agent to the slurry; and drying the slurry comprising the active agent and / or the flavourant, and the cellulose based strengthening agent to form a solid porous aerosol-generating substrate.

[0587] EX166. The method of example EX165, wherein the step of drying the slurry to form the solid porous aerosol-generating substrate comprises lyophilising or freeze-drying the slurry.

[0588] EX167. The method of example EX165 or example EX166, comprising cutting the solid porous aerosol-generating substrate to the required dimensions.

[0589] EX168. The method of example EX165 or example EX166, comprising drying the slurry in a mould to form the solid porous aerosol-generating substrate in the required dimensions.

[0590] Examples will now be further described with reference to the figures in which:

[0591] Figure 1 shows a perspective view of an aerosol-generating article according to a first embodiment of the invention;

[0592] Figure 2 shows an exploded perspective view of the aerosol-generating article of Figure 1 ;

[0593] Figure 3 shows a transverse cross-sectional view of the aerosol-generating article of Figure 1 ; Figure 4 shows a view of an aerosol-generating article according to a second embodiment of the invention; and

[0594] Figure 5 shows an aerosol-generating substrate for the aerosol-generating article of Figure 4.

[0595] With reference to Figure 1 , there is shown an aerosol-generating article 10 comprising a first planar external layer 24 forming a first planar external surface 21 , a second planar external layer 25 forming a second planar external surface 22, and a frame 50 positioned between the first planar external layer 24 and the second planar external layer 25. The first planar external layer 24 and the second planar external layer 25 may be formed from a non-aerosol generating material, such as paper or card. Alternatively, either of the first planar external layer 24 and the second planar external layer 25 may comprise an aerosol-generating substrate comprising an aerosol-generating material, for example tobacco.

[0596] The aerosol-generating article 10 has a length extending in the x-direction, a width extending in the y-direction and a thickness extending in the z-direction. The aerosol-generating article 10 has a length of 30 millimetres, a width of 10 millimetres, and a thickness of 3.1 millimetres.

[0597] The first planar external surface 21 and the second planar external surface 22 extend in the x-direction and the y-direction. That is, the first planar external surface 21 and the second planar external surface 22 extend in the x / y plane. The first planar external surface 21 is positioned parallel to the second planar external surface 22 and the first planar external surface

[0598] 21 is spaced from the second planar external surface 22 in the z-direction or transverse direction. The distance between the first planar external surface 21 and the second planar external surface

[0599] 22 in the z-direction or transverse direction corresponds to the thickness of the aerosol-generating article 10.

[0600] The aerosol-generating article 10 is a substantially flat aerosol-generating article or substantially planar aerosol-generating article. In particular, the thickness of the aerosolgenerating article 10 is less than 50 percent of both the length and the width of the aerosolgenerating article. The aerosol-generating article 10 has a generally rectangular cuboid shape and a laminated structure formed by the first planar external layer 24, the frame 50 and the second planar external layer 25. The first planar external layer 24, the frame 50 and the second planar external layer 25 are bonded together with an adhesive, in particular guar gum.

[0601] Figure 2 shows an exploded view of the aerosol-generating article 10 of Figure 1.

[0602] The frame 50 has a length of 30 millimetres, a width of 10 millimetres, and a thickness of 2.7 millimetres. The frame 50 is made from cardboard and defines a frame aperture extending through the thickness of the frame 50. The frame aperture at least partially forms a cavity 30. The cavity 30 has length of 26 millimetres, a width of 6 millimetres, and a thickness of 2.7 millimetres. Therefore, the cavity 30 has a volume of about 421 .2 cubic millimetres. The cavity 30 is filled with an aerosol-generating substrate 40. The aerosol-generating substrate 40 fills the entire volume of the cavity 30 and airflow through the cavity 30 is provided by interstices between adjacent pores within the aerosol-generating substrate 40. The aerosol-generating substrate 40 will be described in more detail below.

[0603] The first planar external layer 24 and the second planar external layer 25 have a thickness of 200 micrometres and are in physical contact with the frame 50. The first planar external layer 24 and the second planar external layer 25 are bonded to the frame with an adhesive 15. The first planar external layer 24 overlies an end of the cavity 30 and forms a first cavity end wall 31. The second planar external layer 25 overlies an opposite end of the cavity 30 and forms a second cavity end wall 32. That is, the frame 50, the first planar external layer 24 and the second planar external layer 25 collectively define the cavity 30.

[0604] The frame 50 comprises a peripheral wall 51 that circumscribes the cavity 30. The peripheral wall 51 has a radial thickness of about 2 millimetres.

[0605] An air inlet (not visible) and an air outlet 12 are defined by, and extend through, the peripheral wall 51 of the frame 50. The air inlet is positioned opposite the air outlet 12, on the opposite wall of the frame 50. The air inlet and the air outlet 12 each have a rectangular crosssection, a width of 2 millimetres, and a thickness of 0.9 millimetres. An airflow passage extends between the air inlet and the air outlet 12 through the cavity 30.

[0606] The porous aerosol-generating substrate 40 is substantially cuboidal in shape with a length of 26 millimetres, a width of 6 mm and a thickness of 2.7 millimetres. In other words, the aerosol-generating substrate 40 occupies the volume of the cavity 30. The total weight of the aerosol-generating substrate 40 in the cavity is approximately 158 milligrams and thus the bulk density of the aerosol-generating substrate 40 in the cavity 30 is approximately 0.38 milligrams per cubic millimetre. . The aerosol-generating substrate comprises particulate plant material, aerosol former and a binder. Example of suitable compositions of the aerosol-generating substrate 40 are provided below.

[0607] Referring now to Figure 4, the aerosol-generating article 100 has a cylindrical body, which has a downstream or proximal end 112 and an upstream or distal end 114. The aerosolgenerating article 100 is configured to be inserted into a tubular cavity of an electronic aerosolgenerating device (not shown) in which it is electrically heated.

[0608] The downstream end 112 is intended to stay outside of the aerosol-generating device and includes a mouthpiece element 116, which is to be put between the lips of a user and may include a filter.

[0609] The upstream end 114 is intended to be put inside the aerosol-generating device and includes a substrate portion or cavity 118, which comprises a rod of an aerosol-generating substrate 140 according to the present invention, and an upstream element, in the form of a front plug 120. The front plug 120 protects the rod of porous aerosol-generating substrate 140 within the substrate portion or cavity 118 from outside conditions.

[0610] The aerosol-generating article 100 may include other plugs 122, e.g. one or more plugs which provide a cooling function, intermediate the downstream end 112 and the upstream end 114.

[0611] The front plug 120 prevents by-products of the aerosol-generating article 100 from entering the aerosol-generating device. Such by-products include liquid slurry, made from a combination of water (from air humidity) and the heated aerosol-generating material, and particles of the aerosol-generating material which may become dry and brittle after the heating cycle.

[0612] The aerosol-generating article 100 has a length extending along the longitudinal axis of the aerosol-generating article 100 in the x-direction and a diameter extending in the y- and z- directions. The aerosol-generating article 100 has a length of 45 millimetres and a diameter of 7.5 millimetres.

[0613] Figure 5 shows a rod of porous aerosol-generating substrate 140 for the aerosolgenerating article 100 of Figure 4.

[0614] The substrate portion or cavity 118 of the aerosol-generating article 100 and has a length of 12 millimetres and a diameter of 7 millimetres. In other words, the substrate portion or cavity 118 has length of 12 millimetres and a diameter of 7 millimetres. Therefore, the substrate portion or cavity 118 has a volume of about 462 cubic millimetres. The rod of aerosol-generating substrate 140 fills the entire volume of the substrate portion or cavity 118 and airflow through the substrate portion or cavity 118 is provided by interstices between adjacent pores within the aerosolgenerating substrate 140. The aerosol-generating substrate 140 will be described in more detail below.

[0615] Referring again to Figure 4, an air inlet (not visible) is provided at the downstream or proximal end 112 and an air outlet (not visible) is provided at the upstream or distal end 114 of the aerosol-generating article 100. An airflow passage extends between the air inlet and the air outlet through the substrate portion or cavity 118.

[0616] The rod of aerosol-generating substrate 140 is generally cylindrical and has a length extending along the longitudinal axis of the rod of aerosol-generating substrate 140 in the x- direction and a diameter extending in the y- and z-directions. In other words, the aerosolgenerating substrate 140 occupies the volume of the substrate portion or cavity 118. The total weight of the rod of aerosol-generating substrate 140 in the substrate portion or cavity 118 is approximately 173 milligrams and thus the bulk density of the rod of aerosol-generating substrate 140 in the substrate portion or cavity 118 is approximately 0.38 milligrams per cubic millimetre. . The aerosol-generating substrate comprises plant material, aerosol former and a binder.

[0617] Examples of suitable compositions of the aerosol-generating substrate 140 are provided below.

[0618] Example 1

[0619] A suitable composition for forming an aerosol-generating substrate 40, 140 according to the invention is set out in Table 1 below:

[0620] All amounts are shown as percentages by weight, on a dry weight basis, based on the total weight of the aerosol-generating substrate 40, 140.

[0621] In order to make the porous aerosol-generating substrate 40, 140, HPMC is dispersed in glycerin. Agar is added and dispersed in the HPMC and glycerin slurry. Water is mixed into the slurry. Tobacco particles are added to the slurry, which is stirred and dried, for example by lyophilisation.

[0622] In this way, a one-piece aerosol-generating substrate unit may be produced. The aerosolgenerating substrate unit may be formed by drying the slurry in a mould (i.e. casting) or by forming a piece of aerosol-generating substrate material and cutting it to the desired size and shape. The aerosol-generating unit is thus formed as a one-piece porous structure.

[0623] When incorporated into an aerosol-generating article 10, 100 and heated by resistive or induction heating, an aerosol is generated containing a comparable amount of nicotine as obtained from known aerosol-generating substrates in either cylindrical or planar aerosolgenerating articles, despite the mass of aerosol former in the porous aerosol-generating substrate 40, 140 of the present invention being less than the weight of aerosol former in known aerosolgenerating substrates.

[0624] Further advantageously, the porous aerosol-generating substrate of the present invention generates less carbon monoxide than is generated from known aerosol-generating substrates.

[0625] Example 2

[0626] A suitable composition for forming an aerosol-generating substrate 40, 140 according to the invention is set out in Table 2 below:

[0627] All amounts are shown as percentages by weight, on a dry weight basis, based on the total weight of the aerosol-generating substrate 40, 140.

[0628] In order to make the porous aerosol-generating substrate 40, 140, HPMC is dispersed in glycerin. Agar is added and dispersed in the HPMC and glycerin slurry. Water is mixed into the slurry. The particulate plant material (black tea particles), nicotine and lactic acid are added to the slurry, which is stirred and dried, for example by lyophilisation.

[0629] In this way, a one-piece aerosol-generating substrate unit may be produced. The aerosolgenerating substrate unit may be formed by drying the slurry in a mould (i.e. casting) or by forming a piece of aerosol-generating substrate material and cutting it to the desired size and shape. The aerosol-generating unit is thus formed as a one-piece porous structure.

[0630] When incorporated into an aerosol-generating article 10, 100 and heated by resistive or induction heating, an aerosol is generated containing a comparable amount of nicotine as obtained from known aerosol-generating substrates in either cylindrical or planar aerosolgenerating articles, despite the mass of aerosol former in the porous aerosol-generating substrate 40, 140 in the present invention being less than the weight of aerosol former in known aerosolgenerating substrates.

[0631] Further advantageously, the porous aerosol-generating substrate of the present invention generates less carbon monoxide than is generated from known aerosol-generating substrates.

[0632] Example 3

[0633] A further composition for forming an aerosol-generating substrate 40, 140 according to the invention is set out in Table 3 below:

[0634] All amounts are shown as percentages by weight, on a dry weight basis, based on the total weight of the aerosol-generating substrate 40, 140. In order to make the porous aerosol-generating substrate 40, 140, HPMC is dispersed in glycerin. Agar is added and dispersed in the HPMC and glycerin slurry. Water is mixed into the slurry. The tobacco and clove particles (i.e. a mixture of tobacco particles and non-tobacco particulate plant material) are added to the slurry, which is stirred and dried, for example by lyophilisation.

[0635] In this way, a one-piece porous aerosol-generating substrate unit may be produced. The porous aerosol-generating substrate unit may be formed by drying the slurry in a mould (i.e. casting) or by forming a piece of aerosol-generating substrate material and cutting it to the desired size and shape. The aerosol-generating unit is thus formed as a one-piece porous structure.

[0636] When incorporated into an aerosol-generating article 10, 100 and heated by resistive or induction heating, an aerosol is generated containing a comparable amount of nicotine as obtained from known aerosol-generating substrates in either cylindrical or planar aerosolgenerating articles, despite the mass of aerosol former in the porous aerosol-generating substrate 40, 140 in the present invention being less than the weight of aerosol former in known aerosolgenerating substrates.

[0637] Further advantageously, the porous aerosol-generating substrate of the present invention generates less carbon monoxide than is generated from known aerosol-generating substrates.

[0638] Example 4

[0639] An alternative composition for forming an aerosol-generating substrate 40, 140 according to the invention is set out in Table 4 below:

[0640] All amounts are shown as percentages by weight, on a dry weight basis, based on the total weight of the aerosol-generating substrate 40, 140.

[0641] In order to make the porous aerosol-generating substrate 40, 140, HPMC is dispersed in glycerin. Agar is added and dispersed in the HPMC and glycerin slurry. Water is mixed into the slurry. The cellulose-based strengthening agent, nicotine and acid are added to the slurry, which is stirred and dried, for example by lyophilisation.

[0642] In this way, a one-piece aerosol-generating substrate unit may be produced. The aerosolgenerating substrate unit may be formed by drying the slurry in a mould (i.e. casting) or by forming a piece of aerosol-generating substrate material and cutting it to the desired size and shape. The aerosol-generating unit is thus formed as a one-piece porous structure.

[0643] When incorporated into an aerosol-generating article 10, 100 and heated by resistive or induction heating, an aerosol is generated containing a comparable amount of nicotine as obtained from known aerosol-generating substrates in either cylindrical or planar aerosolgenerating articles, despite the mass of aerosol former in the aerosol-generating substrate 40, 140 in the present invention being less than the weight of aerosol former in known aerosolgenerating substrates.

[0644] Further advantageously, the porous aerosol-generating substrate of the present invention generates less carbon monoxide than is generated from known aerosol-generating substrates.

[0645] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 10 of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

CLAIMS1. A porous aerosol-generating substrate for an aerosol-generating article, the porous aerosol-generating substrate comprising: a particulate plant material; at least 10 percent by weight of an aerosol former, on a dry weight basis; and at least 1 percent by weight of a binder, on a dry weight basis; wherein the porous aerosol-generating substrate is formed as a one-piece unit having a length, a width and a thickness; wherein each of the length, the width and the thickness is at least 1 millimetre; and wherein at least one of the length, the width and the thickness is at least 3 millimetres.

2. The porous aerosol-generating substrate of claim 1, wherein the particulate plant material comprises tobacco.

3. The porous aerosol-generating substrate of claim 1 or claim 2, wherein the particulate plant material comprises a non-tobacco particulate plant material, for example wherein the nontobacco particulate plant material comprises one or more of: tea (such as black tea), rosehip seeds, apple fibres, lemon balm stems, coffee, star anise, rooibos, lavender, clove, peppermint, chamomile, rosemary, eucalyptus, ginger, dill seed, thyme, oregano and cumin.

4. A porous aerosol-generating substrate for an aerosol-generating article, the porous aerosol-generating substrate comprising: an active agent and / or a flavourant; a particulate cellulose based strengthening agent; at least 10 percent by weight of an aerosol former, on a dry weight basis; and at least 1 percent by weight of a binder, on a dry weight basis; wherein the porous aerosol-generating substrate is formed as a one-piece unit having a length, a width and a thickness; wherein each of the length, the width and the thickness is at least 1 millimetre; and wherein at least one of the length, the width and the thickness is at least 3 millimetres.

5. The porous aerosol-generating substrate of claim 4, wherein the active agent comprises nicotine.

6. The porous aerosol-generating substrate of claim 4 or claim 5, wherein the particulate cellulose based strengthening agent comprises a microcrystalline cellulose (MCC), cellulose powder or a mixture of microcrystalline cellulose and cellulose powder.

7. The porous aerosol-generating substrate of any one of claims 1 to 6, wherein the aerosol former content is at least 20 percent by weight, on a dry weight basis.

8. The porous aerosol-generating substrate of any one of claims 1 to 7, wherein the aerosol former content is at least 30 percent by weight, on a dry weight basis.

9. The porous aerosol-generating substrate of any one of claims 1 to 8, wherein the aerosol former comprises glycerin or propylene glycol, or a mixture of glycerin and propylene glycol.

10. The porous aerosol-generating substrate of any one of claims 1 to 9, wherein the aerosolgenerating substrate has an average bulk density that is less than or equal to 0.55 grams per cubic centimetre.

11. The porous aerosol-generating substrate of any one of claims 1 to 10, wherein the binder comprises one or more of hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), ethylcellulose (EC), hydroxyethyl methyl cellulose (HEMC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC) and hydroxypropyl cellulose (HPC).

12. The porous aerosol-generating substrate of any one of claims 1 to 11, wherein the binder comprises one or more of agar, guar gum, xanthan gum, Arabic gum, locust bean gum, pectin, carrageenan, starch and alginate.

13. The porous aerosol-generating substrate of any one of claims 1 to 12, having a porosity of at least 60 percent.

14. A method of manufacturing the porous aerosol-generating substrate of any one of claims 1 to 3 or claims 7 to 13, when dependent on any one of claims 1 to 3, the method comprising: mixing the binder and the aerosol former; adding water to the mixture comprising the binder and the aerosol former to form a slurry; adding the particulate plant material to the slurry; and drying the slurry comprising the particulate plant material to form a one-piece unit of porous aerosol-generating substrate.

15. A method of manufacturing the porous aerosol-generating substrate of any one of claims 4 to 6 or claims 7 to 13, when dependent on any one of claims 4 to 6, the method comprising: mixing the binder and the aerosol former; adding water to the mixture comprising the binder and the aerosol former to form a slurry; adding the active agent and / or the flavourant, and the particulate cellulose based strengthening agent to the slurry; and drying the slurry comprising the active agent and / or the flavourant, and the particulate cellulose based strengthening agent to form a one-piece unit of porous aerosol-generating substrate.

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