Cartridge having increased heating efficiency for use with an aerosol-generating system

Abstract

A cartridge (10) for an aerosol-generating device, the cartridge comprising: a housing (12) defining a chamber (18) containing an aerosol-generating substrate (16); a heating element (14) for heating the aerosol-generating substrate, at least a portion of the heating element extending into the chamber; wherein at least a portion of the housing has a multi-layer structure comprising an inner wall (24a), an outer wall (24b) and a thermal insulating layer (26) arranged between the inner and outer walls.

Description

[0001] P / 91290.W001

[0002] -1-

[0003] CARTRIDGE HAVING INCREASED HEATING EFFICIENCY FOR USE WITH AN AEROSOL-GENERATING SYSTEM

[0004] The present disclosure relates to a cartridge for use with an aerosol-generating device. In particular, but not exclusively, the present disclosure relates to a cartridge having increased heating efficiency for use with an aerosol-generating device, and which is configured to generate an aerosol and deliver the aerosol into the mouth of a user. The present disclosure also relates to an aerosol-generating system comprising the cartridge and an aerosolgenerating device.

[0005] Aerosol-generating articles in which an aerosol-generating substrate, such as a tobacco-containing substrate, is heated rather than combusted, are known in the art. Such articles typically generate an aerosol by the transfer of heat from a heat source to a physically separate aerosol-generating substrate or material, which is arranged in thermal contact with the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and are entrained in air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol.

[0006] Electrically heated aerosol-generating devices for use with the aerosol-generating articles described above are also known. Such devices typically include a power source for supplying electrical power to one or more electrical heating elements for heating the aerosolgenerating substrate of the aerosol-generating article. The one or more electrical heating elements can either be part of the aerosol-generating device or part of the aerosol-generating article. Where the heating element is part of the aerosol-generating article, the heating element typically has electrical contacts which are arranged to connect to corresponding electrical contacts arranged in the aerosol-generating device. Electrical power is supplied to the heating element via the electrical contacts.

[0007] A problem that can be encountered with heating elements having electrical contacts is the contact resistance at the point the electrical contacts connect to the electrical contacts of the aerosol-generating device. This may result in ohmic losses at the interface between the heating element and the aerosol-generating device. The ohmic losses result in increased energy consumption by the heating element and therefore reduces heating efficiency as this energy is effectively wasted. It can also result in unwanted heating of the electrical contacts and early degradation of the heating element or cartridge. This can be a particular problem in heating elements because they are typically made from higher resistance materials such as stainless steel or a nichrome alloy.

[0008] Another problem that can be encountered with conventional aerosol-generating articles is heat losses through the walls of the container holding the aerosol-generating substrate. This can result in heat transfer to the exterior surface of the container and an increased temperature profile on the exterior surface of the container, which can make the aerosol-generating article uncomfortable, or even unsafe, to handle. Furthermore, the loss of heat from the container means less heat is available to heat the aerosol-generating substrate, which can result in less aerosol, or an aerosol of reduced quality, being produced. This adversely affects the performance of the aerosol-generating article and can detract from the consumer experience.

[0009] It would be desirable to provide a cartridge for an aerosol-generating device that is more energy efficient. It would be desirable to provide a cartridge for an aerosol-generating device that reduces the energy consumed by the heating element in heating the aerosolgenerating substrate. It would be desirable to provide a cartridge for an aerosol-generating device that reduces energy losses from the cartridge.

[0010] According to an example of the present disclosure, there is provided a cartridge for an aerosol-generating device. The cartridge may comprise a housing. The housing may define a chamber containing an aerosol-generating substrate. The cartridge may comprise a heating element for heating the aerosol-generating substrate. At least a portion of the heating element may extend into the chamber. At least a portion of the housing may have a multi-layer structure. The multi-layer structure may comprise an inner wall. The multi-layer structure may comprise an outer wall. The multi-layer structure may comprise an insulating layer. The insulating layer may be arranged between the inner and outer walls.

[0011] According to an example of the present disclosure, there is provided a cartridge for an aerosol-generating device. The cartridge comprises: a housing defining a chamber containing an aerosol-generating substrate; and a heating element for heating the aerosol-generating substrate. At least a portion of the heating element extends into the chamber. At least a portion of the housing has a multi-layer structure comprising an inner wall, an outer wall and an insulating layer arranged between the inner and outer walls.

[0012] As used herein, the term “cartridge” relates to a component that interacts with an aerosol-generating device to generate an aerosol.

[0013] As used herein, the term “aerosol-generating device” relates to a device that interacts with a cartridge to generate an aerosol.

[0014] As used herein, the terms “inner” and “outer” refer to positions relative to the interior of the chamber. With respect to the walls of the multi-layer structure of the housing, this means that the inner wall is arranged closer to the interior of the chamber than the outer wall. In embodiments in which the multi-layer structure of the housing circumscribes a longitudinal axis of the cartridge, the terms “inner” and “outer” may refer to positions relative to the longitudinal axis. This means that the inner wall is arranged closer to the longitudinal axis of the cartridge than the outer wall.

[0015] Advantageously, the multi-layer structure provides the housing of the cartridge with a double-walled construction, that is, an inner wall and an outer wall. This allows for a gap between the inner and outer walls which accommodates an insulating layer. The insulating layer may help to reduce thermal energy losses from the cartridge compared to a cartridge housing having only a single wall. Furthermore, the double-walled construction and insulating layer may help to reduce heat transfer to the outer surface of the cartridge, thereby reducing the temperature of the outer surface of the cartridge during heating and reducing the likelihood of hotspots forming on the outer surface of the cartridge. This may make the cartridge more comfortable and safe to handle when the cartridge is separated from the device shortly after heating, for example, if the cartridge needs replacing. Furthermore, the double-walled construction and insulating layer may help to reduce thermal energy losses from the cartridge and improves heat retention within the chamber containing the aerosol-generating substrate. This may help to improve the energy efficiency of the cartridge and the aerosol-generating device used to supply power to the cartridge. This may also help generate a more consistent and better quality aerosol, thereby improving the consumer experience.

[0016] The multi-layer structure may have an overall thickness of less than or equal to 7 millimetres, preferably less than or equal to 5 millimetres, and more preferably less than or equal to 4 millimetres.

[0017] The multi-layer structure may have an overall thickness of greater than or equal to 1 millimetre.

[0018] For example, the multi-layer structure may have an overall thickness in the range 1 millimetre to 7 millimetres, preferably in the range 1 millimetre to 5 millimetres, and more preferably in the range 1 millimetre to 4 millimetres.

[0019] The thickness of the insulating layer may be less than or equal to 5 millimetres, preferably less than or equal to 3 millimetres, and more preferably less than or equal to 2 millimetres.

[0020] The thickness of the insulating layer may be greater than or equal to 0.5 millimetres and preferably greater than or equal to 1 millimetre.

[0021] The thickness of the insulating layer may be between 0.5 millimetres and 5 millimetres, preferably between 1 millimetre and 3 millimetres, and more preferably between 1 millimetre and 2 millimetres.

[0022] The multi-layer structure may have an average thermal conductivity across its thickness of less than 5 W / m.K, preferably less than 4 W / m.K, and more preferably less than 3 W / m.K. The insulating layer may comprise an insulating material having a thermal conductivity of less than 0.1 W / m.K, preferably less than 0.08 W / m.K and more preferably less than 0.05 W / m.K.

[0023] The insulating layer may be made from any suitable insulating material. The insulating layer may comprise an insulating material selected from one or more of air, a vacuum, encapsulated air beads or channels and an aerogel. The insulating layer may have any suitable form or shape. For example, the insulating layer may comprise channels or be corrugated.

[0024] The inner wall may be made from any suitable material. The inner wall may comprise a metal, metal alloy or ceramic. The inner wall may comprise an iron-based alloy such as stainless steel or an iron aluminide. The inner wall may comprise a nickel-based alloy such as nichrome. The inner wall may comprise a ceramic such as alumina. The inner wall may comprise a metal with a ceramic coating.

[0025] The outer wall may be made from any suitable material. The outer wall may comprise a metal, metal alloy or ceramic. The outer wall may comprise an iron-based alloy such as stainless steel or an iron aluminide. The outer wall may comprise a nickel-based alloy such as nichrome. The outer wall may comprise a ceramic such as alumina. The outer wall may comprise a metal with a ceramic coating.

[0026] The inner wall may comprise a material having a thermal conductivity of less than 20 W / m.K. The outer wall may comprise a material having a thermal conductivity of less than 20 W / m.K.

[0027] The inner wall and outer wall may be sealed together at their longitudinally opposing ends. The inner wall and outer wall may be joined together at their longitudinally opposing ends by an end wall. The end wall may form a seal, sealing the space between the inner and outer walls.

[0028] The housing may comprise a first housing end section arranged at a proximal end of the cartridge. The housing may comprise a second housing end section arranged at a distal end of the cartridge. The housing may comprise a side wall circumscribing the chamber and extending between the proximal and distal ends of the cartridge. The side wall may comprise the multi-layer structure.

[0029] The first housing end section may comprise a proximal end plug. The proximal end plug may be inserted into an opening defined by the inner surface of the side wall at the proximal end of the cartridge. The second housing end section may comprise a distal end plug. The distal end plug may be inserted into an opening defined by the inner end surface of the side wall at the distal end of the cartridge.

[0030] As used herein, the terms “proximal” and “distal” are used to describe the positions of components, or portions of components, of cartridges, aerosol-generating devices and aerosol-generating systems relative to a consumer. Cartridges, aerosol-generating devices and aerosol-generating systems may comprise a proximal end, which, in normal use, is closer to the consumer than the distal end. Cartridges, aerosol-generating devices and aerosolgenerating systems may comprise a distal end opposite the proximal end.

[0031] The proximal end plug may define the proximal end of the cartridge.

[0032] The distal end plug may define the distal end of the cartridge.

[0033] The side wall may extend from the proximal end of the cartridge to the distal end of the cartridge. The proximal end plug, the distal end plug and the side wall may define the chamber.

[0034] The distal end plug may comprise one or more electrical contacts arranged at an external surface of the cartridge. The one or more electrical contacts may be connected to the heating element. The one or more electrical contacts may be configured to connect to corresponding electrical contacts arranged in an aerosol-generating device.

[0035] The cartridge may comprise one or more air inlets. Preferably, the one or more air inlets are in the distal end plug. The one or more air inlets may be a single air inlet. The one or more air inlets may be a plurality of air inlets.

[0036] The cartridge may comprise one or more aerosol outlets. Preferably, the one or more aerosol outlets are in the proximal end plug. The one or more aerosol outlets may be a single aerosol outlet. The one or more aerosol outlets may be a plurality of aerosol outlets.

[0037] The chamber may extend between the one or more air inlets and the one or more aerosol outlets.

[0038] The heating element may be mounted on the second housing end section at a distal end of the housing.

[0039] The heating element may be an internal heating element. The internal heating element may be embedded in or at least partially surrounded by the aerosol-generating substrate. The internal heating element may be a pin or a blade.

[0040] The heating element may be a planar heating element. The heating element may comprise one or more heating surfaces for heating the aerosol-generating substrate to form an aerosol. The one or more heating surfaces may be planar heating surfaces. The heating element may be substantially or entirely planar. The heating element may be oriented so that a plane of the heating element extends across the width of the cartridge.

[0041] The heating element may have a serpentine shape. The heating element may comprise a plurality of segments. The heating element may comprise a plurality of segments extending parallel to the longitudinal axis of the cartridge. The heating element may be a self- supporting track which extends through the chamber. The heating element may an external heating element. The external heating element may at least partially surround the aerosol-generating substrate.

[0042] The heating element may be a resistive heating element. The heating element may comprise an electrically resistive material.

[0043] The heating element may be formed from an iron-based alloy. The heating element may be formed from a nickel alloy. The heating element may be formed from a ceramic. The heating element may be formed from stainless steel. The heating element may be formed from SS316L stainless steel iron aluminides. The heating element may be formed from nichrome. The heating element may be formed from a ceramic coated metal.

[0044] The heating element may have a length of greater than or equal to 13 millimetres, greater than or equal to 14 millimetres, greater than or equal to 15 millimetres, or greater than or equal to 16 millimetres.

[0045] The heating element may have a length of less than or equal to 20 millimetres, less than or equal to 19 millimetres, less than or equal to 18 millimetres, or less than or equal to 17 millimetres.

[0046] For example, the heating element may have a length of between 13 millimetres and 20 millimetres, between 14 millimetres and 19 millimetres, between 15 millimetres and 18 millimetres, or between 16 millimetres and 17 millimetres.

[0047] The heating element may comprise a susceptor element.

[0048] As used herein, the term “susceptor” denotes a material that is capable of being heated when penetrated by a varying magnetic field.

[0049] The susceptor element may be embedded in or at least partially surrounded by the aerosol-generating substrate.

[0050] The susceptor element may be formed from any material that can be inductively heated to a temperature sufficient to generate an aerosol from the aerosol-generating substrate. For example, the susceptor element may comprise a metal or carbon. The susceptor element may comprise or consist of a ferromagnetic material, for example a ferromagnetic alloy, ferritic iron, or a ferromagnetic steel or stainless steel. A suitable material may be, or comprise, aluminium. The susceptor element may be formed from 400 series stainless steels, for example grade 410, or grade 420, or grade 430 stainless steel.

[0051] Where a susceptor element is provided, the cartridge or an aerosol-generating device may comprise an inductor coil arranged to inductively heat the susceptor element. The inductor coil may at least partly circumscribe the susceptor element.

[0052] The heating element may comprise a dielectric heating element. In particular, the dielectric heating element may comprise a dielectric material. The dielectric heating element may be configured to use radio-frequency (RF) electric waves that cause a dipole interaction with the dielectric material to heat the aerosol-generating substrate.

[0053] The heating element may comprise an infrared heating element. The infrared heating element may be configured to heat the aerosol-generating substrate using infrared electromagnetic radiation.

[0054] The heating element may comprise first and second end portions. The first and second end portions may comprise electrical contacts arranged to connect the heating element to a power source. The electrical contacts may comprise an electrically conductive material having an electrical conductivity greater than 30 x 106Siemens per metre.

[0055] Advantageously, an electrical contact comprising an electrically conductive material helps to reduce the contact resistance at the point that the heating element is connected to another component, which helps to improve the efficiency of the cartridge as discussed below in more detail with respect to the next example of the disclosure. By using a heating element having electrical contacts comprising an electrically conductive material in combination with a housing having a multi-layer structure, the advantages of both these arrangements can be achieved and a cartridge in which the energy efficiency is further enhanced can be realised.

[0056] According to an example of the present disclosure, there is provided a cartridge for an aerosol-generating device. The cartridge may comprise a housing defining a chamber containing an aerosol-generating substrate. The cartridge may comprise a heating element for heating the aerosol-generating substrate. At least a portion of the heating element may extend into the chamber. The heating element may comprise first and second end portions. The first and second end portions may comprise electrical contacts arranged to connect the heating element to a power source. The electrical contacts may comprise an electrically conductive material. The electrically conductive material may have an electrical conductivity greater than 30 x 106Siemens per metre.

[0057] According to an example of the present disclosure, there is provided a cartridge for an aerosol-generating device. The cartridge comprises: a housing defining a chamber containing an aerosol-generating substrate; and a heating element for heating the aerosol-generating substrate, at least a portion of the heating element extending into the chamber. The heating element comprises first and second end portions, the first and second end portions comprising electrical contacts arranged to connect the heating element to a power source. The electrical contacts comprise an electrically conductive material having an electrical conductivity greater than 30 x 106Siemens per metre.

[0058] Advantageous, an electrical contact comprising an electrically conductive material helps to reduces contact resistance at the point the heating element is connected to another component. This helps to reduce ohmic losses when heating the heating element. Furthermore, by reducing ohmic losses, more energy is directed into the heating element rather than dissipating as wasted heat at the electrical contacts, which improves energy efficiency and component longevity. This efficiency enhancement results in more effective heating of the aerosol-generating substrate, potentially leading to a faster heating response, improved energy usage, and better consistency in reaching target temperatures within the chamber of the cartridge. The improved performance of the heating element may also enhance the consistency of aerosol production and contribute to a more consistent draw experience by ensuring uniform aerosol quality.

[0059] The electrical contacts may comprise a coating of the electrically conductive material. The inventors have found that a coating of the electrically conductive material is an effective way of improving the electrical characteristics of the electrical contacts of the heating element. An advantage providing the electrically conductive material as a coating is that it is compatible with existing heating element designs and can be applied without substantial modification to the overall structure of the heating element. This enables easy integration with existing production methods. Techniques such as electroplating make it possible to add the reflective coating without altering the cartridge’s dimensions or significantly impacting production costs.

[0060] The coating of the electrically conductive material may have a thickness in the range 1 micrometre to 50 micrometres. This range has been found to provide effective levels of conductivity, durability, and material efficiency for the electrical contacts. An advantage of coatings having a thickness of approximately 1 micrometre is that electroplating can be used to deposit such a layer.

[0061] The electrically conductive material may have a thermal conductivity of greater than or equal to 100 W / m.K, preferably greater than or equal to 200 W / m.K, more preferably greater than or equal to 300 W / m.K, and yet more preferably greater than 350 W / m.K.

[0062] The electrically conductive material may have a thermal conductivity of less than or equal to 450 W / m.K.

[0063] For example, the electrically conductive material may have a thermal conductivity in the range between 100 and 450 W / m.K, preferably in the range between 200 and 450 W / m.K, more preferably in the range between 300 and 450 W / m.K, and yet more preferably in the range between 350 and 450 W / m.K.

[0064] Advantageously, these values of thermal conductivity have been found to facilitate heat dissipation at the electrical contacts and reduce the formation of hot spots, which helps to improve the longevity of the heating element. Furthermore, high thermal conductivity aids in reducing ohmic losses because resistance generally increases with increasing temperature. This therefore allows for increased energy transfer to the heating element, which optimises the heating efficiency of the cartridge. Inclusion of the conductive material allows for efficient energy transfer with reduced resistive losses, ensuring that more energy reaches the heating element rather than dissipating as heat at the electrical contacts. Consequently, this results in stable operating temperatures, ensuring consistent aerosol production and enhancing the overall performance of the cartridge.

[0065] The electrical contacts may comprise contact pads. The contact pads may have a width that is greater than a width of the heating element. Advantageously, an increased width helps to increase the contact area available for connecting the heating element to the another component, which helps to improve the electrical connection.

[0066] The contact pads may have a U-shaped cross-section. Advantageously, this shape allows the contact pads to resiliently deform such that the contact pads can be electrically connected under the application of a force, which also helps to improve the electrical connection.

[0067] The cartridge may have a length between a proximal end of the cartridge and a distal end of the cartridge. The length of the cartridge may be determined in a direction parallel to the longitudinal axis of the cartridge. The length of the cartridge may be greater than or equal to 10 millimetres, preferably greater than or equal to 12 millimetres, or most preferably greater than or equal to 14 millimetres.

[0068] The length of the cartridge may be less than or equal to 40 millimetres, preferably less than or equal to 30 millimetres, or most preferably less than or equal to 20 millimetres.

[0069] For example, the cartridge may have a length of between 10 millimetres and 40 millimetres, preferably between 10 millimetres and 30 millimetres, or most preferably between 14 millimetres and 20 millimetres.

[0070] The cartridge may have a width in a first direction perpendicular to the longitudinal axis of the cartridge. The width of the cartridge may be greater than or equal to 5 millimetres, preferably greater than or equal to 6 millimetres, or most preferably greater than or equal to 7 millimetres.

[0071] The width of the cartridge may be less than or equal to 20 millimetres, preferably less than or equal to 15 millimetres, or most preferably less than or equal to 12 millimetres.

[0072] For example, the cartridge may have a width of between 5 millimetres and 20 millimetres, preferably between 5 millimetres and 15 millimetres, or most preferably between 7 millimetres and 12 millimetres.

[0073] The cartridge may have a thickness in a second direction perpendicular to the longitudinal axis of the cartridge and to the first direction. The thickness of the cartridge may be greater than or equal to 2 millimetres, preferably greater than or equal to 3 millimetres, or most preferably greater than or equal to 4 millimetres.

[0074] The thickness of the cartridge may be less than or equal to 15 millimetres, preferably less than or equal to 10 millimetres, or most preferably less than or equal to 8 millimetres. For example, the cartridge may have a thickness of between 2 millimetres and 15 millimetres, preferably between 3 millimetres and 10 millimetres, or most preferably between 4 millimetres and 8 millimetres.

[0075] The side wall of the housing may have a thickness of greater than or equal to 1 millimetre, preferably greater than or equal to 2 millimetres, or most preferably greater than or equal to 3 millimetres.

[0076] The side wall of the housing may have a thickness of less than or equal to 7 millimetres, preferably less than or equal to 5 millimetres, or most preferably less than or equal to 4 millimetres.

[0077] For example, the side wall of the housing may have a thickness of between 1 millimetre and 7 millimetres, preferably between 1 millimetre and 5 millimetres, or most preferably between 1 millimetre and 4 millimetres.

[0078] The proximal end plug may have a dimension along a longitudinal axis of the cartridge of greater than or equal to 2 millimetres, preferably greater than or equal to 3 millimetres, or most preferably greater than or equal to 4 millimetres.

[0079] The proximal end plug may have a dimension along a longitudinal axis of the cartridge of less than or equal to 15 millimetres, preferably less than or equal to 10 millimetres, or most preferably less than or equal to 8 millimetres.

[0080] For example, the proximal end plug may have a dimension along a longitudinal axis of the cartridge of between 2 millimetres and 15 millimetres, preferably between 3 millimetres and 10 millimetres, or most preferably between 4 millimetres and 8 millimetres.

[0081] The distal end plug may have a dimension along a longitudinal axis of the cartridge of greater than or equal to 2 millimetres, preferably greater than or equal to 3 millimetres, or most preferably greater than or equal to 4 millimetres.

[0082] The distal end plug may have a dimension along a longitudinal axis of the cartridge of less than or equal to 10 millimetres, preferably less than or equal to 8 millimetres, or most preferably less than or equal to 6 millimetres.

[0083] For example, the distal end plug may have a dimension along a longitudinal axis of the cartridge of between 2 millimetres and 10 millimetres, preferably between 3 millimetres and 8 millimetres, or most preferably between 4 millimetres and 6 millimetres.

[0084] The dimension of the proximal end plug along a longitudinal axis of the cartridge is preferably greater than the corresponding dimension of the distal end plug along a longitudinal axis of the cartridge.

[0085] The chamber of the cartridge of the present disclosure contains an aerosol-generating substrate. As used herein, the term “aerosol-generating substrate” relates to a substrate capable of releasing volatile compounds that can form an aerosol. Such volatile compounds can be released by heating the aerosol-generating substrate.

[0086] Preferably, the aerosol-generating substrate is a solid aerosol-generating substrate.

[0087] As used herein, the term “solid” refers to an aerosol-generating substrate that is not a liquid or a gas and which does not flow such that it retains its shape and form at room temperature. In the context of the present invention, the term “solid” encompasses gel materials and compositions.

[0088] The aerosol-generating substrate may be in the form of one or more sheets of a solid aerosol-generating substrate. Preferably, the one or more sheets of solid aerosol-generating substrate comprise at least one aerosol former and at least one of nicotine and tobacco.

[0089] As used herein, the term “sheet” describes a laminar element having a width and length substantially greater than the thickness thereof.

[0090] The one or more sheets of solid aerosol-generating substrate may be provided on a suitable carrier element. For example, the one or more sheets of solid aerosol-generating substrate may be deposited onto at least one surface a sheet of an inert carrier material, such as paper or cardboard. This may provide improved rigidity to the one or more sheets of solid aerosol-generating substrate, which may facilitate the process of filling the cartridge with the one or more sheets during production.

[0091] The one or more sheets of solid aerosol-generating substrate may be in the form of one or more gathered sheets. As used herein, the term “gathered” denotes that a sheet is convoluted, folded, or otherwise compressed or constricted substantially transversely to a defined axis.

[0092] Alternatively or in addition, the one or more sheets of solid aerosol-generating substrate may be in the form of one or more crimped sheets, preferably, one or more gathered crimped sheets. As used herein, the term “crimped” denotes a sheet having a plurality of substantially parallel ridges or corrugations.

[0093] The one or more sheets of solid aerosol-generating substrate may comprise one or more sheets of homogenised plant material, preferably homogenised tobacco material. The aerosol former content of the homogenised tobacco material is preferably within the ranges defined above for aerosol-generating substrate having a relatively low aerosol former content.

[0094] Alternatively or in addition, the one or more sheets of solid aerosol-generating substrate may comprise one or more sheets comprising an aerosol-generating film, comprising a cellulosic based film forming agent, nicotine and the aerosol former. The aerosolgenerating film may further comprise a cellulose based strengthening agent. The aerosolgenerating film may further comprise water, preferably 30 percent by weight of less of water.

[0095] As used herein, the term “film” is used to describe a solid laminar element having a thickness that is less than the width or length thereof. The film may be self-supporting. The aerosol former content of the aerosol-generating film is within the ranges defined above for aerosol-generating substrates having a relatively high aerosol former content.

[0096] In the context of the present invention the term “cellulose based film-forming agent” is used to describe a cellulosic polymer capable, by itself or in the presence of an auxiliary thickening agent, of forming a continuous film. Preferably, the cellulose based film-forming agent is selected from the group consisting of hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), ethylcellulose (EC), hydroxyethyl methyl cellulose (HEMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), and combinations thereof. In particularly preferred embodiments, the cellulose based film-forming agent is HPMC.

[0097] Suitable aerosol-generating films for use as the aerosol-generating substrate are described in WC-A-2020 / 207733 and WO-A-2022 / 074157.

[0098] Alternatively or in addition, the one or more sheets of solid aerosol-generating substrate may comprise one or more sheets comprising a gel composition that includes nicotine, at least one gelling agent and the aerosol former. The gel composition is preferably tobacco free.

[0099] Suitable gel compositions for use as the aerosol-generating substrate are described in WO-A-2021 / 170642.

[0100] In other embodiments, the aerosol-generating substrate may be in the form of a shredded aerosol-generating substrate. Preferably, the shredded aerosol-generating substrate comprises at least one aerosol former and at least one of tobacco and nicotine.

[0101] As used herein, the term “shredded” describes an aerosol-generating substrate that is in the form of a plurality of shreds or strips. In general, the shredded aerosol-generating substrate is formed by the cutting or shredding of a larger portion of the aerosol-generating substrate, such as a sheet, leaf or other piece of plant material. The individual strips or strands are typically elongate in form, with a length that is greater than the width and thickness.

[0102] The shredded aerosol-generating substrate may be in the form of shredded tobacco material, such as cut filler. Alternatively, the shredded aerosol-generating substrate may be in the form of a shredded sheet of homogenised plant material, such as a homogenised tobacco material. Alternatively, the shredded aerosol-generating substrate may be in the form of a shredded non-tobacco material, as described in more detail below.

[0103] As used herein, the term “cut filler” is used to describe to a blend of shredded plant material, such as tobacco plant material, including, in particular, one or more of leaf lamina, processed stems and ribs, homogenised plant material.

[0104] According to another example of the present disclosure, there is provided an aerosolgenerating system. The aerosol-generating system may comprise any of the cartridges described above. The aerosol-generating system may comprise an aerosol-generating device. The aerosol-generating device may comprise a power source. The aerosolgenerating device may comprise control circuitry for controlling the supply of power from the power source to the heater.

[0105] According to another example of the present disclosure, there is provided an aerosolgenerating system comprising any of the cartridges described above and an aerosolgenerating device. The aerosol-generating device comprises: a power source; and control circuitry for controlling the supply of power from the power source to the heater.

[0106] The power source may be configured to provide power to the heater element to heat the aerosol-generating substrate to generate an aerosol. The power source may be a DC power source. The power source may a battery. The power source may be rechargeable. The power source may have a capacity that allows for the storage of enough energy for one or more user operations, for example one or more aerosol-generating experiences.

[0107] The aerosol-generating device may further comprise a device cavity configured to receive at least a part of the cartridge. The device cavity may have a closed end and an open end. The cartridge may be insertable into the device cavity via the open end. The device cavity may have substantially the same cross-sectional shape as the cartridge.

[0108] The device cavity of the aerosol-generating device may be at least partially defined by a device housing.

[0109] The device housing may comprise one or more of a metal, a plastic, a composite and a metal alloy. Preferably, the device housing comprises one or more of polycarbonate (PC), acrylonitrile butadiene styrene (ABS), liquid crystalline polymer (LCP), copolyester, polyetheretherketone (PEEK), cyclic olefin copolymer (COC), aluminium, an aluminium alloy, magnesium and carbon fibre reinforced polymer.

[0110] Where a susceptor element is provided either as part of the cartridge, the aerosolgenerating device may comprise the inductor coil arranged to inductively heat the susceptor element. Where the aerosol-generating device comprises a device cavity, the inductor coil may at least partly circumscribe the device cavity. The inductor coil may be arranged to coaxially circumscribe the device cavity.

[0111] The control circuity may comprise a controller. The controller may be configured to control the supply of power from the power supply to the heater element. The controller may be electrically connected to the power supply. The controller may be configured to control the power output from the power supply to control whether the heater element is on or off. The controller may be configured to control the power output from the power supply to control the temperature of the heater element.

[0112] The aerosol-generating device may further comprise a mouthpiece. During use, a user may draw on the mouthpiece to receive aerosol generated in the cartridge. The mouthpiece may be configured to move between an open position and a closed position. When the mouthpiece is in the open position, the cartridge may be inserted into or removed from the device cavity. When the mouthpiece is in the closed position, the cartridge may be secured within the aerosol-generating device.

[0113] The mouthpiece may comprise one or more of a metal, plastic and a plant based material. Preferably, the mouthpiece comprises one or more of polycarbonate (PC), acrylonitrile butadiene styrene (ABS), liquid crystalline polymer (LCP), copolyester, polyetheretherketone (PEEK), cyclic olefin copolymer (COC), aluminium, stainless steel, wood and bamboo.

[0114] The aerosol-generating device may comprise a device air inlet. The aerosol-generating device may comprise a device aerosol outlet.

[0115] The device air inlet may be disposed at a distal end of the aerosol-generating device.

[0116] The mouthpiece may comprise the device aerosol outlet. The device aerosol outlet may be disposed at a proximal end of the aerosol-generating device.

[0117] The cartridge and the aerosol-generating device may be configured such that the one or more electrical contacts of the cartridge electrically connect to corresponding electrical contacts of the aerosol-generating device.

[0118] The aerosol-generating system may be configured such that, during use, air passes into the device air inlet, through the device cavity into the one or more air inlets of the cartridge, through the aerosol-generating substrate in the substrate compartment. The aerosolgenerating system may be configured such that, during use, aerosol generated in the substrate compartment is entrained in the air flow and passes to the one or more air outlets of the cartridge, and subsequently to the device aerosol outlet.

[0119] Features described in relation to one of the above examples may equally be applied to other examples of the present disclosure.

[0120] 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.

[0121] Example Ex1 : A cartridge for an aerosol-generating device, the cartridge comprising a housing defining a chamber containing an aerosol-generating substrate.

[0122] Example Ex2: A cartridge according to Example Ex1 , further comprising a heating element for heating the aerosol-generating substrate.

[0123] Example Ex3: A cartridge according to Example Ex2, wherein at least a portion of the heating element extending into the chamber.

[0124] Example Ex4: A cartridge according to any of Examples Ex1 to Ex3, wherein at least a portion of the housing has a multi-layer structure comprising an insulating layer.

[0125] Example Ex5: A cartridge according to Example Ex2, wherein the multi-layer structure further comprises an inner wall and an outer wall, the insulating layer being arranged between the inner and outer walls.

[0126] Example Ex6: A cartridge according to Example Ex4 or Ex5, wherein the multi-layer structure has an overall thickness in the range 1 millimetre to 7 millimetres, preferably in the range 1 millimetre to 5 millimetres, and more preferably in the range 1 millimetre to 4 millimetres.

[0127] Example Ex7: A cartridge according to any of Examples Ex4 to Ex6, wherein a thickness of the insulating layer is between 0.5 millimetres and 5 millimetres, preferably between 1 millimetre and 3 millimetres, and more preferably between 1 millimetre and 2 millimetres.

[0128] Example Ex8: A cartridge according to any of Examples Ex4 to Ex7, wherein the multilayer structure has an average thermal conductivity across its thickness of less than 5 W / m.K, preferably less than 4 W / m.K, and more preferably less than 3 W / m.K.

[0129] Example Ex9: A cartridge according to any of Examples Ex4 to Ex8, wherein the insulating layer comprises an insulating material having a thermal conductivity of less than 0.1 W / m.K, preferably less than 0.08 W / m.K and more preferably less than 0.05 W / m.K.

[0130] Example Ex10: A cartridge according to any of Examples Ex4 to Ex9, wherein the insulating layer comprises an insulating material selected from one or more of air, a vacuum, encapsulated air beads and an aerogel.

[0131] Example Ex11 : A cartridge according to any of Examples Ex5 to Ex10, wherein the inner and outer walls comprise a metal, metal alloy or ceramic having a thermal conductivity of less than 20 W / m.K.

[0132] Example Ex12: A cartridge according to any of Examples Ex5 to Ex11 , wherein the inner wall and outer wall are sealed together at their longitudinally opposing ends.

[0133] Example Ex13: A cartridge according to any of Examples Ex4 to Ex12, wherein the housing comprises: a first housing end section arranged at a proximal end of the cartridge; a second housing end section arranged at a distal end of the cartridge; and a side wall circumscribing the chamber and extending between the proximal and distal ends of the cartridge; wherein the side wall comprises the multi-layer structure.

[0134] Example Ex14: A cartridge according to Example Ex13, wherein the heating element is mounted on the second housing end section at a distal end of the housing.

[0135] Example Ex15: A cartridge according to Example Ex1 or Ex2, wherein the heating element comprises first and second end portions, the first and second end portions comprising electrical contacts arranged to connect the heating element to a power source. Example Ex16: A cartridge according to Example Ex15, wherein the electrical contacts comprise an electrically conductive material having an electrical conductivity greater than 30 x 106Siemens per metre.

[0136] Example Ex17: A cartridge according to Example Ex15 or Ex16, wherein the electrical contacts comprise a coating of the electrically conductive material.

[0137] Example Ex18: A cartridge according to Example Ex17, wherein the coating of the electrically conductive material has a thickness in the range 1 micrometre to 50 micrometres.

[0138] Example Ex19: A cartridge according to any of Examples Ex16 to Ex18, wherein the electrically conductive material has a thermal conductivity in the range 200 to 450 W / m.K, preferably in the range between 300 and 450 W / m.K, and more preferably in the range between 350 and 450 W / m.K.

[0139] Example Ex20: A cartridge according to any of Examples Ex15 to Ex19, wherein the electrical contacts comprise contact pads, the contact pads having a width that is greater than a width of the heating element.

[0140] Example Ex21 : A cartridge according to Example Ex20, wherein the contact pads have a U-shaped cross-section.

[0141] Example Ex22: A cartridge according to any of Examples Ex13 to Ex 21 , wherein the second housing end section comprises one or more electrical contacts arranged at an external surface of the cartridge.

[0142] Example Ex23: A cartridge according to any preceding example, wherein the cartridge comprises one or more air inlets.

[0143] Example Ex24: A cartridge according to any preceding example, wherein the cartridge comprises one or more aerosol outlets.

[0144] Example Ex25: A cartridge according to any preceding example, wherein the aerosolgenerating substrate is a solid aerosol-generating substrate.

[0145] Example Ex26: A cartridge according to any preceding example, wherein the heater element is a resistive heater element.

[0146] Example Ex27: A cartridge according to any preceding example, wherein the housing has a length of between 10 millimetres and 40 millimetres, preferably between 10 millimetres and 30 millimetres, or most preferably between 14 millimetres and 20 millimetres.

[0147] Example Ex28: A cartridge according to any preceding example, wherein the housing has a width of between 5 millimetres and 20 millimetres, preferably between 5 millimetres and 15 millimetres, or most preferably between 7 millimetres and 12 millimetres.

[0148] Example Ex29: A cartridge according to any preceding example, wherein the housing has a thickness of between 2 millimetres and 15 millimetres, preferably between 3 millimetres and 10 millimetres, or most preferably between 4 millimetres and 8 millimetres. Example Ex30: An aerosol-generating system comprising a cartridge according to any of the preceding claims and an aerosol-generating device, the aerosol-generating device comprising: a power source; and control circuitry for controlling the supply of power from the power source to the heater.

[0149] Examples will now be further described with reference to the figures in which:

[0150] Figure 1 is a schematic perspective view of a cartridge according to an example of the present disclosure.

[0151] Figure 2 is a schematic cross-sectional view of the cartridge of Figure 1.

[0152] Figures 3A and 3B are enlarged views of the area enclosed by the dashed circle labelled B in Figure 2 showing examples of multi-layer structures for cartridges according to the present disclosure that use different insulating layers.

[0153] Figure 4 is a perspective view of a heating element for a cartridge according to another example of the present disclosure.

[0154] Figure 5 is a schematic cross-sectional view of an aerosol-generating system according to an example of the present disclosure comprising a cartridge and an aerosolgenerating device.

[0155] It will be appreciated that at least some of the figures in the present application are schematic and have been simplified for the purposes of clarity. Consequently, some features may have been omitted and the features are not necessarily drawn to scale.

[0156] Referring to Figures 1 and 2, there is shown a schematic perspective view and a schematic cross-sectional view respectively of a cartridge 10 for use with an aerosolgenerating device (not shown). The cartridge 10 comprises a housing 12, a heater element 14 and an aerosol-generating substrate 16. The housing 12 defines a chamber 18 containing the aerosol-generating substrate 16.

[0157] The cartridge 10 comprises a proximal end 20 and a distal end 22. The housing 12 comprises a side wall 24 circumscribing the chamber 18. The side wall 24 extends parallel to a longitudinal axis A-A of the cartridge 10 between the proximal 20 and distal 22 ends of the cartridge 10. The side wall 24 comprises a double-wall or multi-layer structure comprising an inner wall 24a, an outer wall 24b and an insulating layer 26 arranged between the inner 24a and outer 24b walls. The inner wall 24a is arranged closer to the interior of the chamber 18 than the outer wall 24b. In otherwords, the inner wall 24a is arranged closer to the longitudinal axis A-A of the cartridge 10 than the outer wall 24b. The inner wall 24a and outer wall 24b of the side wall 24 are sealed together at the proximal 20 and distal 22 ends of the cartridge 10 by end walls 24c such that there is an airtight space between the inner 24a and outer 24b walls.

[0158] In the example cartridge 10 of Figures 1 and 2, the multi-layer structure of the side wall 24 has an overall thickness t of approximately 2.5 millimetres. In other words, the distance from an outer surface of the outer wall 24b to an inner surface of the inner wall 24a in a direction perpendicular to the longitudinal axis A-A is approximately 2.5 millimetres. However, it will be appreciated that the multi-layer structure of the sidewall 24 can have other thicknesses, with the thickness preferably being in the range of 1 to 4 millimetres. The side wall 24 is made from a low thermal conductivity metal such as stainless steel. The multi-layer structure of the side wall 24 has an average thermal conductivity across its overall thickness t of less than 5 W / m.K.

[0159] The thickness d of the insulating layer 26 in the cartridge 10 of Figures 1 and 2 is approximately 1.5 millimetres. In other words, the distance of the space between in inner surface of the outer wall 24b and an outer surface of the inner wall 24a in a direction perpendicular to the longitudinal axis A-A is approximately 1.5 millimetres. However, it will be appreciated that the insulating layer 26 can have other thicknesses, with the thickness preferably being in the range of 1 to 2 millimetres. The insulating layer can be made from a range of different insulating materials, as discussed below with respect to Figures 3A and 3B.

[0160] The housing 12 further comprises a first housing end section arranged at the proximal end 20 of the cartridge 10 and a second housing end section arranged at the distal end 22 of the cartridge 10. In this example, the first housing end section comprises a proximal end plug 28 that is inserted into an opening 32 defined by the inner surface of the side wall 24 at the proximal end 20 of the cartridge 10. Furthermore, the second housing end section comprises a distal end plug 30 that is inserted into an opening 34 defined by the inner end surface of the side wall 24 at the distal end 22 of the cartridge. However, it will be appreciated that the first 28 and second 30 housing end sections may have a different construction to that shown in Figure 2, for example, at least one of the first 28 and second 30 housing end sections may be integral to the side wall 24. The side wall 24 and proximal 28 and distal 30 end plugs define the chamber 18.

[0161] The cartridge 10 comprises a plurality of air inlets 36, which extend through the distal end plug 30 in a direction parallel to the longitudinal axis A-A of the cartridge 10. The cartridge 10 further comprises a plurality of aerosol outlets 38, which extend through the proximal end plug 28 in a direction parallel to the longitudinal axis A-A of the cartridge 10. The plurality of air inlets 36 are in fluid communication with the plurality of aerosol outlets 38. An airflow pathway extends between the plurality of air inlets 36 and the plurality of aerosol outlets 38 through the chamber 18 and through the aerosol-generating substrate 16. Figure 2 shows the cartridge 10 having four air inlets 36 and four aerosol outlets 38. However, it will be appreciated that the cartridge 10 can have any suitable number of air inlets and aerosol outlets and that the dimensions, shape and number of the air inlets and aerosol outlets can be adapted depending on the characteristics desired of the cartridge 10, for example, the amount of aerosol to be produced or the desired resistance to draw (RTD).

[0162] The heating element 14 is configured to heat the aerosol-generating substrate 16 to generate an aerosol. The heating element 14 is a resistive heating element, which is configured to generate heat upon application of a voltage across the heating element 14. In the example cartridge 10 of Figure 2, the aerosol-generating substrate 16 is a solid, tobaccobased aerosol-generating substrate and the heating element 14 is embedded in the aerosolgenerating substrate 16. The heating element 14 is mounted on the distal end plug 30 and extends into the chamber 18. The heating element 14 has a serpentine shape comprising a plurality of segments 14a that extend parallel to the longitudinal axis A-A of the cartridge 10. The heating element 14 is a self-supporting track and is substantially or entirely planar, with the plane of the heating element 14 extending across the width of the cartridge 10.

[0163] The end portions of the heating element 14 comprise electrical contacts 40 which are arranged to connect the heating element 14 to a power source. The electrical contacts 40 are electrically connected to electrically conductive vias 42 which pass through the thickness of the distal end plug 30 and form corresponding electrical contacts at the distal end of the cartridge 10 by which an electrical connection can be made from an aerosol-generating device to the heating element 14.

[0164] Figures 3A and 3B are enlarged views of the area enclosed by the dashed circle labelled B in Figure 2 showing examples of multi-layer structures for the cartridge 10 of Figures 1 and 2 that use different insulating layers. Figure 3A shows part of the housing 12 of the cartridge 10. In particular, it shows the lower part of the side wall 24 of the housing 12 of the cartridge 10. The side wall 24 comprises a double-wall or multi-layer structure comprising an inner wall 24a, an outer wall 24b and an insulating layer 26a arranged between the inner 24a and outer 24b walls. The inner wall 24a and outer wall 24b of the side wall 24 are sealed together at the proximal end (not shown) and distal end 22 of the cartridge 10 by end wall 24c, which creates an airtight space between the inner 24a and outer 24b walls. Although Figure 3A only shows the lower part of the side wall 24, it will be appreciated that the side wall 24 has a similar construction in its upper part and in its upper and lower parts on the other side of the cartridge, as shown in Figure 2.

[0165] In the example of Figure 3A, the insulating layer 26a comprises an intermediate vacuum layer between the inner 24a and outer 24b walls. During manufacture, the space between the inner 24a and outer 24b walls is evacuated to create the vacuum layer prior to the inner 24a and outer 24b walls being sealed by end walls 24c. This vacuum significantly impedes heat convection and conduction by eliminating air particles from the gap. In accordance with thermodynamic principles, heat energy migrates from regions of higher temperature to those of lower temperature. However, the absence of air in the vacuum layer prevents the conduction of heat generated by the internal components to the outer surface. This configuration effectively reduces the temperature reached by the outer surface of the side wall 24 during heating, thereby providing a cooler and safer exterior for the user, while simultaneously enhancing the operational efficiency of the device. The vacuum serves as an effective thermal barrier, reducing the transfer of heat to the outer surface of the side wall 24. On average a double-walled vacuum layer provides a thermal conductivity value of 2-4 W / m.K.

[0166] As mentioned above, the side wall 24 is preferably made from a low thermal conductivity metal such as stainless steel, for example, SS304 stainless steel. This material has non-porous properties, enhanced durability, corrosion resistance, and low thermal conductivity. These characteristics collectively contribute to the reduction of heat transfer through the outer casing, enhancing the overall thermal performance of the cartridge 10.

[0167] Figure 3B also shows the lower part of the side wall 24 of the housing 12 of the cartridge 10 of Figure 2. In Figure 3B, the side wall 24 has essentially the same construction that of Figure 3A, with the exception that it comprises an insulating layer 26b arranged between the inner 24a and outer 24b walls. In one example, the insulating layer 26b comprises a layer of air beads between the inner 24a and outer 24b walls. Air beads are small, lightweight spheres filled with air, which act as effective thermal insulators by creating a series of barriers to heat transfer. The diameter range for these air beads is between 0.1mm and 0.5mm, which helps to ensure that the space between the inner 24a and outer 24b walls is uniformly and stably filled to maximise insulation, whilst reducing the likelihood of excessive compaction that would reduce their effectiveness.

[0168] Air beads achieve their insulation properties by trapping air within each bead’s spherical structure. This trapped air provides a natural barrier to heat transfer. Air has a thermal conductivity of approximately 0.026 W / m.K, which significantly reduces the rate at which heat travels from the heating element to the outer surface of the side wall 24. As a result, the air bead layer effectively prevents the outer surface temperature of the side wall 24 from becoming too hot, creating a cooler, safer handling experience for the user while also enhancing the device's energy efficiency by maintaining heat closer to the heating element.

[0169] The air beads can be made from materials such as hollow glass microspheres or thermally stable polymer microspheres, such as expanded polystyrene microspheres. Suitable hollow glass microspheres are manufactured by JSC Stikloporas of Druskininkai, Lithuania and suitable expanded polystyrene microspheres are manufactured by Sulzer Ltd of Switzerland. Both these materials offer durability, thermal stability, and resistance to compression. The respective properties of these materials are detailed in Table 1 below. The inventors have found that glass microspheres have particular advantages in high-temperature applications due to their non-combustibility and high resistance to degradation, whereas polymer microspheres can be advantageous due to their lightweight nature and flexibility, although they are limited to moderate-temperature ranges.

[0170] Table 1

[0171] In the example of Figure 3B, the multi-layer structure of the side wall 24 ensures that the air beads are securely held in place, preventing movement, and maintaining consistent insulation within the space between the inner 24a and outer 24b walls. By effectively containing heat within the chamber 18, the insulating layer 26b of air beads reduces the need for additional power to sustain aerosolisation temperatures. This approach provides a compact, effective insulation solution, allowing for high thermal resistance in a limited space while enhancing safety and operational efficiency. It will be appreciated that, instead of beads, the insulating layer 26b may comprise an insulating material having some other form, for example, the insulating material may comprise channels or be corrugated.

[0172] In another example, the insulating layer 26b of Figure 3b may comprise a layer of aerogel granules between the inner 24a and outer 24b walls. Suitable aerogel granules are manufactured by Aerogel UK Ltd of Reading, UK. Aerogel granules are highly porous, ultralight particles known for their thermal insulating properties. The respective properties of this material are detailed in Table 2 below. The ideal diameter range for aerogel granules is between 0.05mm to 0.5mm, which allows them to pack uniformly within the space between the inner 24a and outer 24b walls to provided effective insulation without excessive settling or compression, which could compromise their effectiveness.

[0173] Aerogel granules provide insulation by creating an extensive network of microscopic air-filled pores within each particle. Aerogels exhibit a thermal conductivity of approximately 0.012 W / m.K, which provides a substantial reduction in thermal conductivity compared to air and enhanced resistance to heat transfer. Such an insulating layer reduces conductive and convective heat transfer across the space between the inner 24a and outer 24b walls and therefore significantly reduces the rate at which heat from the heating element reaches the outer surface of the side wall 24. Consequently, the aerogel granule layer effectively lowers the outer surface temperature of the side wall 24 during heating and provides a safer, cooler surface for the consumer while improving the device’s energy efficiency by containing heat within the chamber 18.

[0174] Table 2

[0175] Aerogel materials are commonly silica-based. The inventors have found this to be beneficial for cartridges for aerosol-generating devices due to the thermal stability, nonflammability, and high resistance to degradation at elevated temperatures of this material. Silica aerogels, in particular, are well-suited for this application, as they combine high thermal resistance with durability and low weight, providing effective insulation without adding significant mass to the cartridge.

[0176] In the example of Figure 3B, the multi-layer structure of the side wall 24 ensures the aerogel granules are securely packed within the space between the inner 24a and outer 24b walls and retained by end walls 24c. This ensures the aerogel granules remain fixed in position and maintain consistent insulation over time. By effectively trapping heat within the chamber 18, the aerogel layer 26b reduces the power demand on the heating element to maintain aerosolisation temperatures, which enhances the cartridge’s operational efficiency. This example provides a compact insulation solution as the relatively thin aerogel layer 26b achieves good insulation performance. It will be appreciated that, instead of aerogel granules, the insulating layer 26b may comprise an insulating material such as an aerogel having some other form, for example, the insulating material may comprise channels or be corrugated.

[0177] Figure 4 is a perspective view of another heating element 50 for a cartridge according to example of the present disclosure. The heating element 50 is a resistive heating element, which is configured to generate heat upon application of a voltage across the heating element 50. Similar to heating element 14 in Figure 2, the heating element 50 is configured to be mounted on the distal end plug 30 of the cartridge 10 of Figure 2 and extend into the chamber 18. The heating element 50 has a serpentine shape comprising a plurality of segments 50a that extend parallel to the longitudinal axis A-A of the cartridge 10 in Figure 2. The heating element 50 is a self-supporting track and is substantially or entirely planar, with the plane of the heating element 50 being arranged to extend across the width of the cartridge 10.

[0178] The end portions 50b of the heating element 50 comprise electrical contacts 52, which are arranged to connect the heating element 50 to a power source (not shown). The electrical contacts 52 are arranged to electrically connected to the electrically conductive vias 42 in the cartridge 10 of Figure 2, which pass through the thickness of the distal end plug 30 and form corresponding electrical contacts at the distal end of the cartridge 10 by which an electrical connection can be made from an aerosol-generating device to the heating element 50. In the example of Figure 4, the electrical contacts 52 comprise contact pads having a width that is greater than a width of the heating element 50. An increased width helps to increase the contact area available for connecting the heating element 50 to the conductive vias 42, which helps to improve the electrical connection. The contact pads have a U-shaped cross-section which allows them to resiliently deform such that the contact pads can be connected to the conductive vias under the application of a force which also helps to improve the electrical connection.

[0179] The electrical contacts 52 comprise an electrically conductive material having an electrical conductivity greater than 30 x 106Siemens per metre. In particular, the electrical contacts 52 have a coating of the electrical conductive material applied over their surfaces. The inventors have found that the electrically conductive coating applied to electrical contacts 52 helps to reduce ohmic losses, which, as mentioned above, is a particular issue when contact points and heating elements are made from high-resistance materials such as stainless steel or nichrome alloys. The electrically conductive coating can be made from any suitable material having the required electrical conductivity, for example, silver, copper, or another highly conductive metal or alloy, such as those listed in Table 3 below, which also includes stainless steel 304 for comparison. The electrically conductive material was selected by the inventors based on its low electrical resistance, durability, and thermal stability under operating conditions. Silver and copper emerged as the most suitable materials for the application, although the choice of material will depend on the specific characteristics required and may vary for different cartridges. The application of silver or copper to a heating element made from stainless steel 304 resulted in an increase in electrical conductivity of 60.73 x 106and 57.33 x 106Siemens per metre respectively.

[0180] Table 3

[0181] The inventors have also found that a material with high thermal conductivity, that is, a thermal conductivity between 200 and 450 W / m.K, is also advantageous as it facilitates heat dissipation at the electrical contacts 52. This reduces the formation of hot spots and helps to improve the longevity of the heating element. Furthermore, high thermal conductivity aids in reducing ohmic losses because resistance generally increases with increasing temperature. This therefore allows for increased energy transfer to the heating element, which optimises the heating efficiency of the cartridge. Inclusion of the conductive layer allows for efficient energy transfer with reduced resistive losses, ensuring that more energy reaches the heating element rather than dissipating as heat at the electrical contacts. Consequently, this results in stable operating temperatures, ensuring consistent aerosol production and enhancing the overall performance of the cartridge.

[0182] The conductive coating is applied during manufacturing and forms a thin but robust layer on the surface of each electrical contact 52. A manufacturing processes such as electroplating could be utilised for the applying the coating. The thickness of a conductive coating applied by electroplating ranges from 5 to 50 micrometres (pm). The thickness of the conductive coating is directly proportional to the levels of conductivity, durability, and material efficiency of the electrical contacts 52.

[0183] Figure 5 is a schematic cross-sectional view of an aerosol-generating system 200 comprising the cartridge 10 of Figure 1 and an aerosol-generating device 100. The aerosolgenerating device 100 comprises a device cavity 110 and a mouthpiece 112. The device cavity 110 is defined by a device housing 150. The cartridge 10 is configured to be received in the device cavity 110 of the aerosol-generating device 100.

[0184] The mouthpiece 112 is disposed at a proximal end of the aerosol-generating device 100 and is configured to move between an open position and a closed position. When the mouthpiece 112 is in the open position, the cartridge 10 can be inserted into or removed from the device cavity 110. When the mouthpiece 112 is in the closed position, the cartridge 10 is secured within the aerosol-generating device 100. In Figure 5, the mouthpiece 112 is shown in the closed position.

[0185] The aerosol-generating device 100 comprises a device air inlet 108, a device aerosol outlet 109, a power supply 130, and a controller 140. The device air inlet 108 is disposed at a distal end of the aerosol-generating device 100 and the device aerosol outlet 109 is arranged in the mouthpiece 112. The device air inlet 108 is in fluid communication with the plurality of air inlets (not shown) of the cartridge 10 and the device aerosol outlet 109 is in fluid communication with the plurality of aerosol outlets (not shown) of the cartridge 10. Therefore, an airflow pathway extends between the device air inlet 108 and device aerosol outlet 109, which pathway passes through the cartridge 10 to entrain generated aerosol.

[0186] The cartridge 10 and the aerosol-generating device 100 are configured such that the electrical contacts (not shown) of the cartridge 10 electrically connect to corresponding electrical contacts of the aerosol-generating device 100. The electrical contacts of the aerosolgenerating device 100 are electrically connected to the power supply 130, such that power can be supplied from the power supply 130 to the heating element (not shown) of the cartridge 10. In this example, the power supply 130 is in the form of a battery, for example, a rechargeable lithium ion battery.

[0187] The controller 140 is electrically connected to the power supply 130. The controller 140 is configured to control the supply of power from the power supply 130 to the heating element of the cartridge 10. In particular, the controller 140 controls whether the heating element is on or off and the temperature of the heating element.

[0188] In use, a consumer inserts a cartridge 10 into the device cavity 110 of the aerosolgenerating device 100 and activates the device. This causes the heating element of the cartridge 10 to start heating the aerosol-generating substrate contained within the cartridge 10. When the heating element and aerosol-generating substrate are at the aerosolization temperature of the aerosol-generating substrate, the consumer can take a puff on the aerosolgenerating system 200. This draws air in through the device air inlet 108, through the device cavity 110 and into the plurality of air inlets 110 of the cartridge 10. The air passes through the aerosol-generating substrate surrounding the heating element in the cartridge 10, which entrains aerosol in the moving airflow. The aerosol laden airflow passes out of the cartridge 10 via the plurality of aerosol outlets of the cartridge 10, and is delivered to the device aerosol outlet 109 in the mouthpiece 112, where it passes into the mouth of the consumer.

[0189] 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 ± 5 percent (5%) 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 cartridge for an aerosol-generating device, the cartridge comprising: a housing defining a chamber containing an aerosol-generating substrate; a heating element for heating the aerosol-generating substrate, at least a portion of the heating element extending into the chamber; wherein at least a portion of the housing has a multi-layer structure comprising an inner wall, an outer wall and a thermal insulating layer arranged between the inner and outer walls.

2. A cartridge according to claim 1 , wherein the multi-layer structure has an overall thickness in the range 1 millimetre to 7 millimetres.

3. A cartridge according to claim 1 or 2, wherein a thickness of the thermal insulating layer is between 0.5 millimetres and 5 millimetres.

4. A cartridge according to any of claims 1 to 3, wherein the multi-layer structure has an average thermal conductivity across its thickness of less than 5 W / m.K.

5. A cartridge according to any preceding claim, wherein the thermal insulating layer comprises an insulating material having a thermal conductivity of less than 0.1 W / m.K.

6. A cartridge according to any preceding claim, wherein the thermal insulating layer comprises an insulating material selected from one or more of air, a vacuum, encapsulated air beads or channels and an aerogel.

7. A cartridge according to any preceding claim, wherein the inner and outer walls comprise a metal, metal alloy or ceramic having a thermal conductivity of less than 20 W / m.K.

8. A cartridge according to any preceding claim, wherein the inner wall and outer wall are sealed together at their longitudinally opposing ends.

9. A cartridge according to any preceding claim, wherein the housing comprises: a first housing end section arranged at a proximal end of the cartridge; a second housing end section arranged at a distal end of the cartridge; and a side wall circumscribing the chamber and extending between the proximal and distal ends of the cartridge;wherein the side wall comprises the multi-layer structure.

10. A cartridge according to claim 9, wherein the heating element is mounted on the second housing end section at a distal end of the housing.

11. A cartridge according to any preceding claim, wherein the heating element comprises first and second end portions, the first and second end portions comprising electrical contacts arranged to connect the heating element to a power source; and wherein the electrical contacts comprise an electrically conductive material having an electrical conductivity greater than 30 x 106Siemens per metre.

12. A cartridge for an aerosol-generating device, the cartridge comprising: a housing defining a chamber containing an aerosol-generating substrate; and a heating element for heating the aerosol-generating substrate, at least a portion of the heating element extending into the chamber; wherein the heating element comprises first and second end portions, the first and second end portions comprising electrical contacts arranged to connect the heating element to a power source; wherein the electrical contacts comprise an electrically conductive material having an electrical conductivity greater than 30 x 106Siemens per metre.

13. A cartridge according to claim 11 or 12, wherein the electrical contacts comprise a coating of the electrically conductive material.

14. A cartridge according to any of claims 11 to 13, wherein the coating of the electrically conductive material has a thickness in the range 1 micrometre to 50 micrometres.

15. A cartridge according to any of claims 11 to 14, wherein the electrically conductive material has a thermal conductivity in the range 100 to 450 W / m.K.

16. A cartridge according to any of claims 11 to 15, wherein the electrical contacts comprise contact pads, the contact pads having a width that is greater than a width of the heating element.

17. A cartridge according to claim 16, wherein the contact pads have a U-shaped crosssection.

18. An aerosol-generating system comprising a cartridge according to any of the preceding claims and an aerosol-generating device, the aerosol-generating device comprising: a power source; and control circuitry for controlling the supply of power from the power source to the heater.

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