Aerosol-generating system having heater assembly, and cartridge for aerosol-generating system having fluid permeable heater assembly

Abstract

To provide an aerosol-generating system that comprises a heater assembly that is suitable for vaporizing a liquid.SOLUTION: An aerosol-generating system includes a liquid storage portion which includes a rigid housing holding a liquid aerosol-forming substrate, the housing having an opening, and a fluid permeable heater assembly including a plurality of electrically conductive filaments, where the fluid permeable heater assembly is fixed to the housing and extends across the opening of the housing. Providing the heater assembly that extends across the opening of the liquid storage portion allows a robust construction that is relatively simple to manufacture. This configuration allows a large contact area between the heater assembly and the liquid aerosol-forming substrate. The heater assembly may be substantially flat, allowing simple manufacture.SELECTED DRAWING: Figure 5b

Description

[Technical field]

[0001] The present invention relates to an aerosol generating system that includes a heater assembly suitable for vaporizing a liquid, in particular to a handheld aerosol generating system, such as an electrically operated smoking system. [Background technology]

[0002] One type of aerosol generating system is an electrically operated smoking system. Handheld electrically operated smoking systems are well known, with a device portion including a battery and control electronics, a cartridge portion including a supply of aerosol-forming substrate, and an electrically operated vaporizer. A cartridge with both a supply of aerosol-forming substrate and a vaporizer is sometimes called a "cartomizer". The vaporizer generally includes a heater wire coil wound around an elongated wick immersed in a liquid aerosol-forming substrate. The cartridge portion generally includes not only a supply of aerosol-forming substrate and an electrically operated vaporizer, but also a mouthpiece through which the user draws the aerosol into the mouth during use.

[0003] However, this arrangement has the disadvantage that the cartridges are relatively expensive to manufacture because the wick and coil assembly is difficult to manufacture. Also, the electrical contact between the coil of heater wire and the electrical contact through which the current is supplied from the device portion must be delicately handled during manufacture. Furthermore, these cartridges include a mouthpiece portion to protect the delicate wick and coil assembly during shipping. However, the inclusion of a complete and sturdy mouthpiece in each cartridge means that each cartridge has high material costs.

[0004] It is desirable to provide a heater assembly suitable for aerosol generating systems, such as handheld, electrically operated smoking systems, that is inexpensive to manufacture and robust. It is further desirable to provide a heater assembly that is more efficient than prior heater assemblies for aerosol generating systems. Summary of the Invention

[0005] In a first aspect, an aerosol generating system is provided, the aerosol generating system comprising: a liquid reservoir having a housing for holding a liquid aerosol-forming substrate, the housing having an opening; A fluid permeable heater assembly including a plurality of electrically conductive filaments, the fluid permeable heater assembly being secured to the housing and extending across an opening in the housing.

[0006] Providing the heater assembly extending across the opening of the liquid storage portion allows for a relatively simple and robust structure to manufacture. This arrangement allows for a large contact area between the heater assembly and the liquid aerosol-forming substrate. The housing may be a rigid housing. As used herein, "rigid housing" means a free-standing housing. The rigid housing of the liquid storage portion preferably provides mechanical support for the heater assembly. The heater assembly may be substantially planar, allowing for simple manufacture. As used herein, "substantially planar" means initially formed in a single plane and not wound or adapted to a curved or other non-planar shape. Geometrically, the term "substantially planar" conductive filament array is used to mean a conductive filament array that is in the form of a substantially two-dimensional topological manifold. Thus, a substantially planar conductive filament array extends two-dimensionally along a surface that is substantially greater than the third dimension. In particular, the dimension of the substantially planar filament array in two dimensions within its surface is at least five times greater than the third dimension perpendicular to the surface. An example of a substantially planar filament array is a structure between two substantially imaginary parallel surfaces, where the distance between the two imaginary surfaces is less than the extent of the extension of the surfaces. In some embodiments, the substantially planar filament array is planar. In other embodiments, the substantially planar filament array is curved along one or more dimensions, for example forming a dome or bridge shape.

[0007] The term "filament" is used throughout this specification to mean an electrical path disposed between two electrical contacts. The filament may optionally branch into several paths or filaments, or may merge from several electrical paths into one path. The filament may be round, square, flat, or have any other cross-sectional configuration. The filament may be arranged in a straight or curved manner.

[0008] The term "filament array" is used throughout this specification to mean an array of one or, preferably, a plurality of filaments. The filament array may, for example, be a series of filaments arranged parallel to one another. Preferably, the filaments may form a mesh. The mesh may be woven or non-woven.

[0009] The planar heater assembly allows for easy handling during manufacturing and provides a sturdy construction.

[0010] The system may advantageously include a device and a cartridge removably coupled to the device, where the liquid reservoir and heater assembly are provided within the cartridge, and where the device includes a power source. The cartridge may be manufactured in a reliable and reproducible manner at low cost. As used herein, the cartridge being "removably coupled" to the device means that the cartridge and device can be coupled and separated from one another without significant damage to either the device or the cartridge.

[0011] The system may be an electrically operated smoking system.

[0012] The conductive filaments may lie in a single plane, which allows for easier handling during manufacturing and provides a robust construction.

[0013] The conductive filaments may define gaps between the filaments, the gaps may have a width of 10 μm to 100 μm. The filaments preferably induce capillary action within the gaps such that liquid to be vaporized in use is drawn into the gaps increasing the contact area between the heater assembly and the liquid.

[0014] The conductive filaments may form a mesh with a size of 160-600 mesh US (±10%) (i.e. 160-600 filaments per inch (±10%)). The gap width is preferably 75 μm-25 μm. The open area ratio of the mesh, which is the ratio of the gap area to the total area of ​​the mesh, is preferably 25%-56%. The mesh may be formed using different types of weaves or lattice structures. Alternatively, the conductive filaments consist of a series of filaments aligned parallel to one another.

[0015] A mesh, array or fiber of conductive filaments may also be characterized by its ability to retain liquid, as is well known in the art.

[0016] The diameter of the conductive filaments may be between 10 μm and 100 μm, preferably between 8 μm and 50 μm, more preferably between 8 μm and 39 μm. The filaments may have a round or flat cross section.

[0017] The area of ​​the mesh, array or fibre of conductive filaments can be as small as 25 mm 2 Preferably, the conductive filament mesh, array or fiber is less than 10% by 50% of the area of ​​the heater assembly. More preferably, the conductive filament mesh or array covers an area of ​​15% by 25% of the area of ​​the heater assembly. Preferably, the conductive filament mesh, array or fiber covers an area of ​​10% and 50%, or 25% by 25% of the area of ​​the heater assembly. 2 The following dimensions reduce the total amount of power required to heat the mesh, array or fiber of conductive filaments while ensuring sufficient contact of the mesh, array or fiber of conductive filaments with one or more capillary materials supplied with the liquid to be evaporated.

[0018] The heater filaments may be formed by etching a sheet material (such as a foil). This may be particularly advantageous when the heater assembly comprises a series of parallel filaments. If the heater assembly comprises a mesh or woven fabric of filaments, the filaments may be formed individually and woven together. Alternatively, the heater filaments may be stamped from a conductive foil, such as stainless steel.

[0019] The filaments of the heater assembly may be formed from any material having suitable electrical properties. Suitable materials include, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics (e.g., molybdenum disilicide, etc.), carbon, graphite, metals, alloys, and composites made of ceramic and metallic materials. Such composites may include doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable alloys include stainless steel, constantan, nickel-, cobalt-, chromium-, aluminum-titanium-zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, and iron-containing alloys, and nickel, iron, cobalt, stainless steel-based superalloys, Timetal®, iron-aluminum-based alloys, and iron-manganese-aluminum-based alloys. Timetal® is a registered trademark of Titanium Metals Corporation. The filaments may be coated with one or more insulators. Preferred materials for the conductive filaments are 304, 316, 304L, 316L stainless steel, and graphite. Additionally, the conductive filament array may include combinations of the above-mentioned materials. Combinations of materials may be used to improve the control of the resistance of the substantially planar filament array. For example, an inherently high resistivity material may be combined with an inherently low resistivity material. This may be useful when one of the materials is more advantageous from another perspective, such as price, machinability, or other physical and chemical parameters. Advantageously, the substantially planar filament array with increased resistivity reduces wasteful losses. Advantageously, the high resistivity heater allows for more efficient use of battery energy. Battery energy is proportionally divided between energy lost in the printed circuit board and contacts and energy provided to the conductive filament array.Thus, the energy available for the conductive filament array within the heater increases as the conductive filament array becomes more resistive.

[0020] In an exemplary embodiment, the substantially flat filament array may be comprised of two types of metal wires formed into a wire mesh. In such an embodiment, the high resistivity wires are preferably oriented in the direction of current flow, such as nickel-chromium alloy wires. Thus, in this embodiment, the low resistivity wires are arranged substantially perpendicular to the high electrical resistance wires. For example, the low resistivity may be stainless steel wires. Advantageously, the relatively inexpensive low resistivity wires form a support for the high electrical resistance wires. Furthermore, the high electrical resistance wires are generally less malleable than stainless steel wires and therefore cannot be easily manufactured into thin wires. Thus, in such an advantageous embodiment of the invention, a relatively thick wire with high electrical resistance is combined with a thin stainless steel wire with low electrical resistance, with the additional benefit of the thinner stainless steel wire improving the wetting of the substantially flat filament array by increasing capillary forces.

[0021] Alternatively, the conductive filament array may be formed of woven carbon yarn. Woven carbon yarn has the advantage that it is generally more cost effective than highly resistive metal heaters. In addition, woven carbon yarn is generally more flexible than metal mesh. Another advantage is that contact between the woven carbon yarn and a conveying medium such as a highly emissive material is well preserved during construction of the fluid permeable heater assembly.

[0022] Reliable contact between the fluid permeable heater assembly and the transport medium (e.g., capillary transport medium, fiber or porous ceramic material wick, etc.) promotes consistent wetting of the fluid permeable heater assembly, which advantageously reduces the risk of overheating the conductive filament array and inadvertent thermal decomposition of the liquid.

[0023] The heater assembly may comprise an electrically insulated substrate on which the filaments are supported. The electrically insulated substrate may comprise any suitable material, but is preferably a material that can withstand high temperatures (greater than 300 degrees Celsius) and rapid temperature changes. One example of a suitable material is a polyimide film, such as Kapton®. The electrically insulated substrate may have openings formed therein, with the conductive filaments extending across the openings. The heater assembly may comprise electrical contacts connected to the conductive filaments. For example, the electrical contacts may be glued, welded or mechanically clamped to the conductive filament array. Alternatively, the conductive filament array may be printed onto the electrically insulated substrate, for example using a metallic ink. In such an arrangement, the electrically insulated substrate is preferably a porous material, such that the conductive filament array is applied directly to the surface of the porous material. In such an embodiment, the porosity of the substrate preferably serves as an "opening" in the electrically insulated substrate through which liquid may be drawn toward the conductive filament array.

[0024] The electrical resistance of the mesh, array or fiber of conductive filaments of the heater element is preferably between 0.3 ohms and 4 ohms. More preferably, the electrical resistance of the mesh, array or fiber of conductive filaments is between 0.5 ohms and 3 ohms, and more preferably about 1 ohm. The electrical resistance of the mesh, array or fiber of conductive filaments is preferably at least one order of magnitude greater than the electrical resistance of the contacts, and more preferably at least two orders of magnitude greater. This ensures that the heat generated by passing a current from the heater element is localized to the mesh or array of conductive filaments. When the system is powered by a battery, it is advantageous for the heater element to have a low overall resistance. A low resistance, high current system allows high power to be delivered to the heater element. This allows the heater element to heat the conductive filaments quickly to the desired temperature.

[0025] The first and second conductive contact portions may be secured directly to the conductive filament. The contact portions may be disposed between the conductive filament and an electrically insulating substrate. For example, the contact portions may be formed from copper foil plated onto an insulating substrate. The contact portions may also be more easily bonded to the filament than to the insulating substrate.

[0026] Alternatively, the first and second conductive contact portions may be integral with the conductive filament. For example, the heater element may be formed by etching a conductive sheet to provide a plurality of filaments between the two contact portions.

[0027] The heater assembly may comprise at least one filament made from a first material and at least one filament made from a second material different from the first material. This may be beneficial for electrical or mechanical reasons. For example, one or more of the filaments may be formed from a material that has a resistance that varies significantly with temperature, such as an iron-aluminium alloy. This allows a measurement of the resistance of the filament to be used to determine temperature or temperature changes. This may be used in a puff detection system to control the heater temperature to keep the heater within a desired temperature range. Sudden changes in temperature may also be used as a means of detecting changes in air flow through the heater assembly due to smoking by a user of the system.

[0028] The liquid storage housing advantageously includes a capillary material, which is a material that actively transports liquid from one end of the material to the other, the capillary material being advantageously oriented within the housing to transport the liquid to the heater assembly.

[0029] The capillary material may have a fibrous or spongy structure. The capillary material preferably comprises a bundle of capillaries. For example, the capillary material may comprise a number of fibers or threads, or other fine tubes. The fibers or threads may be generally aligned to transport the liquid to the heater. Alternatively, the capillary material may comprise a spongy or foam-like material. The structure of the capillary material forms a number of small holes or tubes through which the liquid can travel by capillary action. The capillary material may comprise any suitable material or combination of materials. Examples of suitable materials include spongy or foam materials, ceramic or graphite-based materials in the form of fibers or sintered powders, foamed metal or plastic materials, fibrous materials made of spun or extruded fibers (such as cellulose acetate, polyester, or bonded polyolefin, polyethylene, terylene or polypropylene fibers, nylon fibers or ceramics). The capillary material may have any suitable capillary and porosity to be used with different liquid physical properties. A liquid has physical properties, including but not limited to viscosity, surface tension, density, thermal conductivity, boiling point and vapor pressure, that enable it to move through a capillary device by capillary action.

[0030] The capillary material may be in contact with the conductive filaments. The capillary material may extend into the gaps between the filaments. The heater assembly may draw the liquid aerosol-forming substrate into the gaps by capillary action. The capillary material may be in contact with the conductive filaments over substantially the entire length of the opening. In one embodiment, the capillary material in contact with the conductive filament array may be a filamentary wick. The filamentary wick preferably has a first portion and a second portion, where the first portion is aligned substantially perpendicular to the conductive filament array and extends into the liquid storage portion of the cartridge. The second portion of the filamentary wick is preferably aligned substantially parallel to the conductive filament array. The filaments of the filamentary wick are preferably continuous from the first portion of the filamentary wick to the second portion of the filamentary wick. This allows for rapid transport of liquid towards the conductive filament array through the first portion of the filamentary wick and simultaneously rapid distribution throughout the conductive filament array through the second portion of the filamentary wick. This advantageously allows for continuous wetting of the entire conductive filament array. Continuous wetting helps to avoid overheating and prevents inadvertent decomposition of the liquid due to overheating.

[0031] The conductive filament array preferably includes at least some filaments that are metallic or coated with a film that is sensitive to the presence of a liquid such as water. This allows detection of wetting of the conductive filament array, for example by connecting the sensitive wire to a circuit that monitors the electrical resistance of the wire and prevents the heater from operating or reduces the current if a dry interface is detected. This advantageously increases the safety of the aerosol generation system. In one embodiment, the filaments used for wetting detection are stainless steel wires coated with an indium nitride (InN) or aluminum oxide (Al2O3) film. In use, a liquid such as water depletes electrons from the surface of such a film, preserving the high electrical resistance of the film until the moment the film surface dries. The resistance then drops rapidly. The drop in resistance is detected by a connected electronic circuit.

[0032] Advantageously, the heater assembly and the capillary material may be sized to have approximately the same area. As used herein, "approximately" means that the heater assembly may be 0-15% larger than the capillary material. The shape of the heater assembly may also be similar to the shape of the capillary material such that the assembly and material substantially overlap. When the size and shape of the assembly and material are substantially the same, manufacturing may be simplified and the reliability of the manufacturing process is improved. As discussed below, the capillary material may include two or more capillary materials, including one or more layers of capillary material in direct contact with the mesh, array or fibers of conductive filaments of the heater assembly to facilitate aerosol generation. The capillary material may include materials described herein.

[0033] At least one capillary material may have a sufficient volume to ensure that a minimum amount of liquid is present within the capillary material to prevent "dry heating", which occurs when insufficient liquid is provided to the capillary material in contact with the mesh, array or fiber of conductive filaments. A minimum volume of the capillary material may be provided to allow a user to take 20-40 puffs. The average volume of liquid volatilized during a 1-4 second puff is typically 1-4 mg. Thus, at least one capillary material having a volume to hold 20-160 mg of liquid including a liquid-forming substrate may prevent dry heating.

[0034] The housing may include two or more different capillary materials, where a first capillary material in contact with the heater element has a higher pyrolysis temperature and a second capillary material in contact with the first capillary material but not the heater element has a lower pyrolysis temperature. The first capillary material effectively acts as a spacer separating the heater element from the second capillary material so that the second capillary material is not exposed to temperatures above its pyrolysis temperature. As used herein, "pyrolysis temperature" means the temperature at which a material begins to decompose and lose mass by generating gaseous by-products. The second capillary material may advantageously occupy a larger volume than the first capillary material, but may also hold more aerosol-forming substrate than the first capillary material. The second capillary material may have better wick performance than the first capillary material. The second capillary material may be less expensive than the first capillary material. The second capillary material may be polypropylene.

[0035] The first capillary material may separate the heater assembly from the second capillary material by a distance of at least 1.5 mm, but preferably between 1.5 mm and 2 mm to provide a sufficient temperature drop across the first capillary material.

[0036] The liquid reservoir may be located on a first side of the conductive filament and the airflow channel may be located in the liquid reservoir from an opposite side of the conductive filament such that the airflow passing through the conductive filament is mixed into the vaporized liquid aerosol-forming substrate.

[0037] In addition to the electric heater assembly located adjacent to or in contact with the liquid delivery medium, the aerosol generating system may include at least one further electric heater assembly in operative association with the liquid storage portion. The further electric heater assembly in operative association with the liquid storage portion may increase the depletion of liquid from the liquid storage portion. This is particularly advantageous when the liquid storage portion includes a high retention medium for storing the liquid. It is advantageous to use a high retention medium to store the liquid in the liquid storage portion. For example, the use of a high retention medium reduces the risk of leakage. In the event of a defect or crack in the cartridge housing, the leaked liquid may lead to unintended contact with live components or biological tissue. However, since the liquid is attached to the surface of the high retention medium by wettability forces, in the event of a mechanical crack in the cartridge housing, a significant loss of liquid is unlikely to occur compared to a tank filled with free liquid. However, since the high retention medium essentially retains at least some portion of the liquid, this portion is not used for aerosolization. Advantageously, providing additional heating assemblies increases the depletion rate of the liquid reservoir, i.e., the ratio of liquid removed from the liquid reservoir to the amount of liquid that cannot be removed from the liquid reservoir.

[0038] The further electric heater assembly is preferably located near an area of ​​high retention medium that is less likely to be depleted by the main electric heater assembly, e.g., the most area of ​​high retention medium that is furthest from the first electric heater assembly. The further electric heater assembly is preferably located on the bottom wall of the housing, i.e., the wall opposite the electric heater assembly. Alternatively or additionally, the further electric heater assembly is located on a side wall of the housing.

[0039] The further electric heater assembly is preferably controlled to be activated only when required, for example when a reduction in liquid flow is detected, for example the further electric heater assembly may be activated when a reduction in wetting of the first electric heater assembly is detected.

[0040] Alternatively or additionally, the housing has an internal non-cylindrical, e.g. conical, shape such that a wider portion of the internal non-cylindrical faces towards the electric heater assembly and a smaller portion of the internal extends in the opposite direction. This increases the relevance of gravity acting on the liquid to drive it towards the electric heater assembly, especially when the aerosol generation system is in a substantially horizontal orientation. A horizontal orientation is one in which the electric heater assembly is at substantially the same vertical level as the liquid storage portion. This horizontal orientation is typical during use of the aerosol generation system.

[0041] Alternatively or additionally, the cartridge including the electric heater assembly and the housing is positioned within the aerosol generation system such that the electric heater assembly is positioned across the opening of the housing on the side of the liquid storage portion away from the mouthpiece of the aerosol generation system. This may be useful for the flow path of the aerosol within the aerosol generation system. For example, in a vertically oriented aerosol generation system, the mouthpiece is at the top and the housing is positioned upside down, i.e., the liquid is positioned above the electric heater assembly. In such an embodiment, the capillary force driving the liquid towards the electric heater assembly is assisted by gravity instead of having to overcome gravity.

[0042] The housing preferably includes two elements, where the first element is the cap and the second element is the tank, and the cap closes the tank. According to the invention, the cap preferably includes or is in intimate contact with the heater assembly. The tank preferably includes the liquid and, if present, the first capillary material or both the first and second capillary materials. The cap material is preferably made of a material having a high pyrolysis temperature, for example polyetheretherketone (PEEK) or Kapton®. The cap is preferably large enough to separate the tank from the heater assembly by a distance of at least 1.5 mm, and preferably between 1.5 mm and 2 mm to provide a sufficient temperature drop across the cap. Advantageously, in such an embodiment, the tank material can be made of a more cost-effective material having a lower pyrolysis temperature, for example polyethylene or polypropylene.

[0043] The air inlet is, for example, located in the main housing of the system. Ambient air is directed into the system, passing through a heating element at the distal end of the cartridge and entraining an aerosol due to heating of the aerosol-forming substrate within the cartridge. The air-containing aerosol can then be guided along the cartridge between the cartridge housing and the main housing to the downstream end of the system, where it mixes with ambient air from a further flow path (either before or after reaching the downstream end).

[0044] The inlet opening of the second channel, located in the region of the distal end of the cartridge housing, may also be provided in an alternative system in which the heating element is located at the proximal end of the cartridge. The second flow path passes through the cartridge as well as outside it. The ambient air then enters the semi-open wall of the cartridge, passes through it and exits it by passing through the heating element located at the proximal end of the cartridge. Thereby, the ambient air may pass through one or more channels located within the aerosol-forming substrate, or within the solid aerosol-forming substrate, such that the ambient air passes through a channel next to the substrate, rather than through the substrate itself.

[0045] At least one semi-open inlet is provided in a wall of the cartridge housing, preferably the wall opposite the heating element, preferably the bottom wall, to allow ambient air to enter the cartridge. The semi-open inlet allows air to enter the cartridge but does not allow air or liquid to leave the cartridge through the semi-open inlet. The semi-open inlet may for example be a semi-permeable membrane that is permeable to air in only one direction but does not allow air and liquid to leak in the opposite direction. The semi-open inlet may for example be a one-way valve. The semi-open inlet preferably only allows air to pass through the inlet if certain conditions are met, such as for example minimal dentation of the cartridge and the volume of air passing through the valve or membrane.

[0046] Such one-way valves can be, for example, commercially available valves, such as, for example, LMS Mediflow One-Way, LMS SureFlow One-Way or LMS Check Valves (crossing membranes) used in medical devices. Suitable membranes for use in cartridges where airflow passes through the cartridge include, for example, vented membranes used in medical devices (e.g., Qosina Ref. 11066, vented cap with hydrophobic filter) or valves used in baby bottles. Such valves and membranes can be of any material suitable for use in electrically heated smoking systems. Materials suitable for medical devices and FDA approved materials can be used, such as, for example, Graphene, which has very high mechanical resistance and thermal stability over a wide temperature range. The valves are preferably made of a soft elastic material, so that one or more valves can be incorporated into the wall of the container housing to prevent liquid leakage.

[0047] Passing ambient air through the substrate assists in aerosolization of the aerosol-forming substrate. During smoking, the cartridge may be indented, which activates the semi-open inlet. Ambient air then passes through the cartridge, preferably a high retention or high release material (HRM) or liquid, and across the heating element, thereby initiating and maintaining aerosolization of the liquid when the heating element heats the liquid sufficiently. Additionally, the indentation created during smoking may restrict the supply of liquid to the heating element in a carrier material, such as a capillary material. Ambient airflow through the cartridge may equalize the pressure difference within the cartridge, thereby assisting unhindered capillary action toward the heating element.

[0048] A semi-open inlet may additionally or alternatively be provided in one or more side walls of the cartridge housing. The semi-open inlet in the side wall provides a lateral airflow into the cartridge towards the open top end of the cartridge housing where the heating element is located. The lateral airflow preferably passes through the aerosol-forming substrate.

[0049] The system may further include an electrical circuit connected to the heater assembly and to the power source, the electrical circuit configured to monitor an electrical resistance of the heater assembly or of one or more filaments of the heater assembly and to control a power supply to the heater assembly dependent on the electrical resistance of the heater assembly or of the one or more filaments.

[0050] The electrical circuitry may comprise a microprocessor, which may be a programmable microprocessor. The electrical circuitry may comprise further electronic components. The electrical circuitry may be configured to regulate the power supply to the heater assembly. Power may be supplied to the heater assembly continuously after activation of the system, or intermittently, such as with each inhalation. Power may be supplied to the heater assembly in the form of current pulses.

[0051] The system advantageously includes a power source, typically a battery, within the body of the housing. Alternatively, the power source may be another form of charge storage device, such as a capacitor. The power source may require recharging and may have a capacity that allows for storage of sufficient energy for one or more smoking experiences. For example, the power source may have a capacity sufficient to allow for continuous generation of aerosol for about six minutes, or a multiple of six minutes. In another example, the power source may have a capacity sufficient to allow for a predetermined number of puffs, or discontinuous activation of the heater assembly.

[0052] The aerosol generating system preferably includes a housing. The housing is preferably elongated. The housing may include any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics or composites containing one or more of these materials, or thermoplastics suitable for food or pharmaceutical applications, such as, for example, polypropylene, polyetheretherketone (PEEK) and polyethylene. The material is preferably lightweight and not brittle.

[0053] The aerosol generating system is preferably portable. The aerosol generating system may have a size comparable to a conventional cigar or cigarette. The overall length of the smoking system may be from about 30 mm to about 150 mm. The outer diameter of the smoking system may be from about 5 mm to about 30 mm.

[0054] An aerosol-forming substrate is a substrate capable of releasing a volatile compound capable of forming an aerosol. The volatile compound can be released by heating the aerosol-forming substrate.

[0055] The aerosol-forming substrate may comprise a plant-derived material. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise a tobacco-containing material comprising volatile tobacco flavour compounds which are released from the aerosol-forming substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco-containing material. The aerosol-forming substrate may comprise a homogenised plant-derived material. The aerosol-forming substrate may comprise a homogenised tobacco material. The aerosol-forming substrate may comprise at least one aerosol-forming agent. The aerosol-forming substrate may comprise other additives and ingredients (such as flavourants).

[0056] In a second aspect, there is provided a cartridge for use in an electrically operated aerosol generation system, comprising: a liquid reservoir having a housing for holding a liquid aerosol-forming substrate, the housing having an opening; a fluid permeable heater assembly including a plurality of electrically conductive filaments, the fluid permeable heater assembly extending across an opening in the housing of the liquid storage portion.

[0057] Cartridges of this construction are robust, reliable and can be manufactured at low cost. The heater assembly can be substantially planar and does not require any winding of heater wire around the capillary wick.

[0058] The conductive filaments may lie in a single plane, which allows for easier handling during manufacturing and provides a robust construction.

[0059] The conductive filaments may define gaps between the filaments, the gaps may have a width of 10 μm to 100 μm. The filaments preferably induce capillary action within the gaps such that liquid to be vaporized in use is drawn into the gaps increasing the contact area between the heater assembly and the liquid.

[0060] The conductive filaments may form a mesh with a size of 160-600 mesh US (±10%) (i.e., 160-600 filaments per inch (±10%)). The gap width is preferably 75 μm-25 μm. The mesh open area ratio, which is the ratio of the gap area to the total mesh area, is preferably 25-56%. The mesh may be formed using different types of weaves or lattice structures. Alternatively, the conductive filaments consist of a series of filaments aligned parallel to one another.

[0061] The conductive filaments may have a diameter of 10 μm to 100 μm, preferably 8 μm to 50 μm, and more preferably 8 μm to 39 μm. The filaments may have a round or flat cross-section. The heater filaments may be formed by etching a sheet material (such as a foil). This may be particularly advantageous when the heater assembly comprises a series of parallel filaments. Where the heater assembly comprises a mesh or woven fabric of filaments, the filaments may be formed individually and woven together.

[0062] The area of ​​the mesh, array or fibre of conductive filaments can be as small as 25 mm 2Preferably, the conductive filament mesh, array or fiber is less than 10% by 50% of the area of ​​the heater assembly, allowing for incorporation into a handheld system. The conductive filament mesh, array or fiber may be rectangular, for example, with dimensions of 5 mm by 2 mm. Preferably, the conductive filament mesh or array covers an area of ​​10% to 50% of the area of ​​the heater assembly. More preferably, the conductive filament mesh or array covers an area of ​​15% to 25% of the area of ​​the heater assembly.

[0063] The conductive filaments may comprise any suitable conductive material. Preferred materials for the conductive filaments are 304, 316, 304L, 316L stainless steel, and graphite.

[0064] The electrical resistance of the mesh, array or fiber of conductive filaments of the heater element is preferably 0.3 to 4 ohms, more preferably 0.5 to 3 ohms, and more preferably about 1 ohm. The electrical resistance of the mesh, array or fiber of conductive filaments is preferably at least one order of magnitude greater than the electrical resistance of the contact area, and more preferably at least two orders of magnitude greater.

[0065] The liquid storage housing may include a capillary material as described in relation to the first embodiment. The capillary material may be oriented within the housing to carry the liquid to the heater assembly. The capillary material may be in contact with the heater assembly. The capillary material may extend into the gaps between the filaments.

[0066] As described in relation to the first embodiment, the housing may comprise two or more different capillary materials, where a first capillary material in contact with the heater element has a higher pyrolysis temperature and a second capillary material in contact with the first capillary material but not with the heater element has a lower pyrolysis temperature. The first capillary material may separate the heater assembly from the second capillary material by a distance of at least 1.5 mm, with 1.5-2 mm being preferred to provide a sufficient temperature drop across the first capillary material.

[0067] As described in relation to the first embodiment, the heater assembly may include at least one filament made from a first material and at least one filament made from a second material different from the first material.

[0068] The heater assembly may comprise an electrically insulated substrate on which the filament is supported, the filament extending across an opening formed in the substrate. The electrically insulated substrate may comprise any suitable material, but is preferably a material capable of withstanding high temperatures (greater than 300° C.) and rapid temperature changes. One example of a suitable material is a polyimide film such as Kapton®.

[0069] The heater assembly may include conductive contacts in contact with the plurality of filaments. The conductive contacts may be provided between a housing of the liquid storage portion and an electrically insulated substrate. The conductive contacts may be provided between the filaments and the electrically insulated substrate. An opening may be formed in the insulating layer, and the cartridge may include two conductive contacts located on opposite sides of the opening.

[0070] Advantageously, the conductive contacts are accessible from the exterior of the cartridge. The heater assembly may extend in a lateral plane and the conductive contacts may extend laterally beyond the housing of the liquid reservoir. The cartridge may then be configured to be inserted into an aerosol generating device in a direction perpendicular to the lateral plane, such that the conductive contacts make contact with electrical contacts of the device.

[0071] The liquid reservoir housing may be substantially cylindrical, where the opening is at one end in a circle. The liquid reservoir housing may have a substantially circular cross-section.

[0072] The heater assembly is advantageously covered with a removable cover or seal prior to use, which may protect the substrate from deterioration during storage and shipping.

[0073] In one preferred embodiment, the cartridge does not include a power source.

[0074] In a third aspect, there is provided a method of making a cartridge for use in an electrically operated aerosol generation system, comprising: Providing a liquid reservoir comprising a housing having an opening; filling the liquid reservoir with a liquid aerosol-forming substrate; and securing a fluid-permeable heater assembly including a plurality of conductive filaments to the liquid storage portion, the fluid-permeable heater assembly extending across an opening in a housing of the liquid storage portion.

[0075] The step of filling the liquid reservoir may be performed before or after the step of securing the heater assembly to the liquid reservoir.

[0076] The step of fastening may include, for example, heat sealing, gluing or welding the heater assembly to the liquid reservoir. The liquid reservoir may include a capillary material.

[0077] Features described in relation to one aspect may be applied to the other aspects of the invention, in particular features described in relation to the first aspect may be applied to the second and third aspects as well.

[0078] As used herein, "electrically conductive" means a resistivity of 1×10 -4 As used herein, "insulating" means made of a material with a resistivity of 1×10 4 Ω m or higher. As used herein, "fluid permeable" in relation to the heater assembly means that the aerosol-forming substrate (in gas phase, but potentially in liquid phase) can easily pass through the heater assembly.

[0079] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: [Brief description of the drawings]

[0080] [Figure 1a] FIG. 1a is a schematic diagram of a system incorporating a cartridge according to an embodiment of the present invention. [Figure 1b] FIG. 1b is a schematic diagram of a system incorporating a cartridge according to an embodiment of the present invention. [Figure 1c] FIG. 1c is a schematic diagram of a system incorporating a cartridge according to an embodiment of the present invention. [Figure 1d] FIG. 1d is a schematic diagram of a system incorporating a cartridge according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of a clasp mechanism for the mouthpiece portion of the system of FIG. [Diagram 3] FIG. 3 is an exploded view of the cartridge of FIGS. 1a-1d. [Figure 4] FIG. 4 is an exploded view of an alternative cartridge for use in the system shown in FIGS. 1a-1d. [Figure 5a] FIG. 5a is a perspective view of the underside of the cartridge of FIG. [Figure 5b] FIG. 5b is a perspective view of the top of the cartridge of FIG. 2 with the cover removed. [Figure 6] FIG. 6 is a detailed view of the heater assembly used in the cartridge shown in FIG. [Figure 7] FIG. 7 is a detailed view of an alternative heater assembly that may be used in the cartridge shown in FIG. [Figure 8] FIG. 8 is a detailed view of a further alternative heater assembly that may be used in the cartridge shown in FIG. [Figure 9] FIG. 9 is a detailed view of yet a further alternative heater assembly that may be used in the cartridge shown in FIG. [Figure 10] FIG. 10 is a detailed view of an alternative mechanism for making electrical contact between the device and the heater assembly. [Figure 11a]FIG. 11a illustrates several cartridge housing shapes that may be used to ensure proper alignment of the cartridge within the device. [Figure 11b] FIG. 11b illustrates several cartridge housing shapes that may be used to ensure proper alignment of the cartridge within the device. [Figure 12a] FIG. 12a is a detailed view of the heater filaments, showing the meniscus of the liquid aerosol-forming substrate between the filaments. [Figure 12b] FIG. 12b is a detailed view of the heater filaments, showing the meniscus of the liquid aerosol-forming substrate between the capillary material extending between the filaments. [Figure 13a] FIG. 13a illustrates an alternative manufacturing method for a heater assembly according to the present invention. [Figure 13b] FIG. 13b illustrates an alternative manufacturing method for a heater assembly according to the present invention. [Figure 13c] FIG. 13c illustrates an alternative manufacturing method for a heater assembly according to the present invention. [Figure 14] FIG. 14 illustrates an alternative design of the liquid reservoir incorporating a heater assembly. [Figure 15a] FIG. 15a illustrates a further alternative embodiment of a liquid storage portion into which a heater assembly is incorporated. [Figure 15b] FIG. 15b illustrates a further alternative embodiment of a liquid storage portion into which a heater assembly is incorporated. [Figure 16] FIG. 16 illustrates an alternative embodiment of airflow and cartridge orientation with an aerosol generating device. [Figure 17] FIG. 17 shows a cross section of a cartridge system with high retention material and air passages within the HRM. [Figure 18] FIG. 18 shows a cross section of an alternative cartridge system having high retention material and air passages within the cartridge. [Figure 19]FIG. 19 shows an exploded view of the cartridge system of FIG. [Figure 20] FIG. 20 shows a cross section of a cartridge system with liquid and air passages through the liquid. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0081] Figures la-ld are schematic diagrams of an aerosol generation system including a cartridge according to an embodiment of the present invention. Figure la is a schematic diagram of an aerosol generation device 10 and a separate cartridge 20, which together form the aerosol generation system. In this example, the aerosol generation system is an electrically operated smoking system.

[0082] The cartridge 20 contains an aerosol-forming substrate and is configured to be received in a cavity 18 in the device. The cartridge 20 should be replaceable by a user when the aerosol-forming substrate provided in the cartridge is depleted. Figure 1a shows the cartridge 20 immediately prior to insertion into the device, with arrow 1 in Figure 1a indicating the direction of insertion of the cartridge.

[0083] The aerosol generating device 10 is portable and has a size comparable to a conventional cigar or cigarette. The device 10 includes a body 11 and a mouthpiece portion 12. The body 11 includes a battery 14 (such as a lithium iron phosphate battery), control electronics 16, and a cavity 18. The mouthpiece portion 12 is connected to the body 11 by a hinged connection 21 and is movable between an open position shown in FIG. 1 and a closed position shown in FIG. 1d. The mouthpiece portion 12 is placed in the open position to allow insertion and removal of a cartridge 20, and is placed in the closed position when the system is used to generate aerosol, as described below. The mouthpiece portion includes a number of air inlets 13 and outlets 15. In use, a user draws or inhales the outlets to draw air from the air inlets 13, through the mouthpiece portion, to the outlets 15, and then into the user's mouth or lungs. An internal baffle 17 is provided to force air flow through the cartridges through the mouthpiece portion 12, as described below.

[0084] The cavity 18 has a circular cross-section and is sized to receive the housing 24 of the cartridge 20. An electrical connector 19 is provided on the side of the cavity 18 for providing electrical connection between the control electronics 16 and the battery 14 and corresponding electrical contacts on the cartridge 20.

[0085] Figure 1b shows the system of Figure 1a with the cartridge inserted into cavity 18 and cover 26 removed. In this position, the electrical connector bears against electrical contacts on the cartridge, as described below.

[0086] FIG. 1c shows the system of FIG. 1b with the cover 26 completely removed and the mouthpiece portion 12 moved to the closed position.

[0087] FIG. 1d shows the system of FIG. 1c with the mouthpiece portion 12 in a closed position. The mouthpiece portion 12 is held in the closed position by a clasp feature as shown diagrammatically in FIG. 2. FIG. 2 illustrates a body 11 and a mouthpiece portion 12 connected by a hinged connection 21. The mouthpiece portion 12 includes inwardly extending teeth 8. When the mouthpiece portion is in the closed position, the teeth 8 engage with a clasp 6 on the body of the device. The clasp 6 is biased by a bias spring 5 into engagement with the teeth 8. A button 4 is secured to the clasp 6. The button 4 can be pressed by a user against the action of the bias spring 5 to release the teeth 8 from the clasp 6, allowing the mouthpiece portion to move to the open position. It will be apparent to one of ordinary skill in the art that other suitable mechanisms for holding the mouthpiece in the closed position may be used, such as a snap-on or magnetic closure.

[0088] The mouthpiece portion 12 in the closed position keeps the cartridge in electrical contact with the electrical connector 19 so that a good electrical connection is maintained in use regardless of the orientation of the system. The mouthpiece portion 12 may include an annular resilient element that engages a surface of the cartridge and is compressed between the rigid mouthpiece housing element and the cartridge when the mouthpiece portion 12 is in the closed position. This maintains a good electrical connection regardless of manufacturing tolerances.

[0089] Of course, other mechanisms for maintaining a good electrical connection between the cartridge and the device may alternatively or additionally be employed. For example, the housing 24 of the cartridge 20 may be provided with threads or grooves (not shown) that engage with corresponding grooves or threads (not shown) formed in the walls of the cavity 18. The threaded engagement between the cartridge and the device may be used to ensure proper rotational alignment as well as to retain the cartridge in the cavity and ensure a good electrical connection. The threaded connection may extend less than a half turn of the cartridge, or may extend several turns. Alternatively or additionally, the electrical connector 19 may be biased to make contact with contacts on the cartridge, as described with reference to FIG. 8.

[0090] 3 is an exploded view of cartridge 20. Cartridge 20 includes a generally cylindrical housing 24 having a size and shape selected to be received within cavity 18. The housing includes a capillary material 22 immersed in a liquid aerosol-forming substrate. In this example, the aerosol-forming substrate includes 39 percent by weight glycerin, 39 percent by weight propylene glycol, 20 percent by weight water and flavorings, and 2 percent by weight nicotine. The capillary material is a material that actively transports liquid from one end to the other and may be manufactured from any suitable material. In this example, the capillary material is formed from polyester.

[0091] The housing has an open end in which a heater assembly 30 is secured. The heater assembly 30 includes a base 34 having an opening 35 formed therein, a pair of electrical contacts 32 secured to the base and separated from one another by gaps 33, and a plurality of conductive heater filaments 36 secured across the opening to the electrical contacts on opposite sides of the opening 35.

[0092] The heater assembly 30 is covered by a removable cover 26. The cover comprises a liquid impermeable plastic sheet that is adhered to the heater assembly but is easily removable. Tabs are provided on the sides of the cover to allow a user to grasp the cover when removing it. It will be apparent to one of ordinary skill in the art that although adhesion is described as a method of securing the impermeable plastic sheet to the heater assembly, other methods familiar to those skilled in the art may also be used, including heat sealing or ultrasonic welding, so long as the cover can be easily removed by the consumer.

[0093] FIG. 4 is an exploded view of an alternative exemplary cartridge. The cartridge of FIG. 4 is the same size and shape as the cartridge of FIG. 3, and has the same housing and heater assembly. However, the capillary material in the cartridge of FIG. 4 is different from that of FIG. 3. The cartridge of FIG. 4 has two separate capillary materials 27, 28. A disk of the first capillary material 27 is provided for contacting the heater elements 36, 32 during use. A larger body of the second capillary material 28 is provided on the opposite side of the first capillary material 27 to the heater assembly. Both the first capillary material and the second capillary material hold a liquid aerosol-forming substrate. The first capillary material 27, which contacts the heater element, has a higher pyrolysis temperature (at least 160° C. or higher, such as about 250° C.) than the second capillary material 28. The first capillary material 27 effectively acts as a spacer separating the heater elements 36, 32 from the second capillary material 28 so that the second capillary material is not exposed to temperatures above its thermal decomposition temperature. A thermal gradient across the first capillary material is such that the second capillary material is exposed to temperatures below its thermal decomposition temperature. The second capillary material 28 can be selected to have good wicking properties to the first capillary material 27, can hold more liquid per unit volume than the first capillary material, and can be less expensive than the first capillary material. In this example, the first capillary material is a heat resistant element such as glass fiber or an element containing glass fiber, and the second capillary material is a polymer such as a suitable capillary material. Exemplary suitable capillary materials include the capillary materials discussed herein, and in alternative embodiments can include high density polyethylene (HDPE), or polyethylene terephthalate (PET).

[0094] FIG. 5a is a perspective view of the underside of the cartridge of FIG. 3. It can be seen from FIG. 5a that the heater assembly extends in a lateral plane and laterally beyond the housing 24 such that the heater assembly forms a lip around the top of the housing 24. The exposed portions of the electrical contacts 32 face the insertion direction of the cartridge such that when the cartridge is fully inserted into the cavity 18, the exposed portions of the contacts 32 contact the electrical connector 19. Tabs provided on the sides of the cover 26 for a user to grip the cover when peeling are clearly shown. FIG. 5a also illustrates a locating feature 25 formed in the base of the cartridge to ensure proper orientation of the cartridge in the cavity of the device. The locating feature 25 is part of the injection molded housing 24 and is configured to be received in a corresponding slot (not shown) in the base of the cavity 18. When the locating feature 25 is received in the slot in the cavity, the contacts 32 are aligned with the connector 19.

[0095] Figure 5b is a perspective view of the top of the cartridge of Figure 3 with the cover removed. The heater filament 36 is exposed through an opening 35 in the substrate 34 to allow vaporized aerosol-forming substrate to escape into the airflow passing through the heater assembly.

[0096] The housing 24 is formed from a thermoplastic material such as polypropylene. In this example, the heater assembly 30 is glued to the housing 24. However, there are several possible ways to assemble and fill the cartridge.

[0097] The cartridge housing may be formed by injection molding. The capillary material 22, 27, 28 may be formed by cutting appropriate lengths of capillary material from a long rod of capillary fiber. The heater assembly may be assembled using the process described in connection with Figures 11a, 11b and 11c. In one embodiment, the cartridge is assembled by first inserting one or more of the capillary materials 22, 27, 28 into the housing 24. A volume of liquid aerosol-forming substrate is then introduced into the housing 24, soaking the capillary material. The heater assembly 30 is then pressed into the open end of the housing and secured to the housing 24 by gluing, welding, heat sealing, ultrasonic welding, or other methods that will become apparent to those skilled in the art herein. During any sealing operation, the temperature of the housing is preferably kept below 160°C to prevent undesired volatilization of the aerosol-forming substrate. The capillary material may be cut to a length that extends out of the open end of the housing 24 until it is compressed by the heater assembly. This facilitates transport of the aerosol-forming substrate into the gap of the heater element in use.

[0098] In another embodiment, instead of pressing the heater assembly 30 into the housing 24 and then sealing it, the open end of the heater assembly and housing may first be rapidly heated and then the heater assembly 30 may be pressed together to bond it to the housing 24.

[0099] It is also possible to assemble the heater assembly 30 to the housing 24 prior to filling the housing with the aerosol-forming substrate, and introduce the aerosol-forming substrate into the housing 24. In that case, the heater assembly may be secured to the cartridge using any of the methods described. The heater assembly or housing is then pierced using a hollow needle, and the aerosol-forming substrate is injected into the capillary material 22, 27, 28. Any openings made by the hollow needle are then sealed using a heat seal or sealing tape.

[0100] FIG. 6 illustrates a first heater assembly 30 according to the present disclosure. The heater assembly comprises a mesh formed from 304L stainless steel with a mesh size of about 400 mesh US (about 400 filaments per inch). The filaments have a diameter of about 16 μm. The mesh is formed of copper foil with a thickness of about 30 μm, connected to electrical contacts 32 separated from each other by gaps 33. The electrical contacts 32 are provided on a polyimide substrate 34 with a thickness of about 120 μm. The filaments forming the mesh define gaps between the filaments. In this example, the gaps have a width of about 37 μm, although larger or smaller gaps may be used. Using a mesh of these approximate dimensions, a meniscus of the aerosol-forming substrate is formed within the gaps, and the mesh of the heater assembly draws the aerosol-forming substrate by capillary action. The open area of ​​the mesh, i.e., the ratio of the area of ​​the gaps to the total area of ​​the mesh, is advantageously between 25 and 56%. The total resistance of the heater assembly is about 1 ohm. The mesh provides most of this resistance, as most of the heat is generated by the mesh, which in this example has an electrical resistance over 100 times higher than the electrical contacts 32.

[0101] The substrate 34 is electrically insulating and is formed from a polyimide sheet having a thickness of about 120 μm in this example. The substrate is circular and has a diameter of 8 mm. The mesh is rectangular and has side lengths of 5 mm and 2 mm. These dimensions allow for the production of a complete system having a size and shape similar to a conventional cigarette or cigar. Another example of dimensions that has proven effective is a circular substrate with a diameter of 5 mm and a rectangular mesh of 1 mm by 4 mm.

[0102] Figure 7 illustrates an alternative exemplary heater assembly according to the present disclosure. The heater assembly of Figure 7 is the same as that shown in Figure 6, except that the mesh 36 is replaced by an array of parallel conductive filaments 37. The array of filaments 37 is formed from 304L stainless steel and has a diameter of about 16 μm. The substrate 34 and copper contacts 32 are as described with reference to Figure 6.

[0103] Figure 8 illustrates another alternative heater assembly according to the present disclosure. The heater assembly of Figure 8 is the same as that shown in Figure 7, except that in the assembly of Figure 8, the filament 37 is bonded directly to the substrate 34 and then the contacts 32 are bonded onto the filament. The contacts 32 are separated from each other by insulating gaps 33 as before and are formed from copper foil about 30 μm thick. The same arrangement of substrate filaments and contacts can also be used for a mesh type heater, as shown in Figure 6. Having the contacts as the outermost layer can be beneficial in providing reliable electrical contact with a power source.

[0104] FIG. 9 illustrates an alternative heater assembly according to the present disclosure. The heater assembly of FIG. 9 includes a plurality of heater filaments 38 formed integrally with electrical contacts 39. Both the filaments and electrical contacts are formed from stainless steel foil that is etched to define the filaments 38. The contacts 39 are separated by gaps 33 except when joined by the filaments 38. The stainless steel foil is provided on a polyimide substrate 34. Again, the filaments 38 provide the majority of this resistance, such that the majority of the heat is generated by the filaments. In this example, the filaments 38 have an electrical resistance that is over 100 times higher than the electrical contacts 39.

[0105] In the cartridge shown in Figures 3, 4 and 5, the contacts 32 and filaments 36, 38 are located between the substrate layer 34 and the housing 24. However, the heater assembly can also be mounted inversely to the cartridge housing, with the polyimide substrate directly adjacent the housing 24. Figure 10 illustrates this type of arrangement. Figure 10 shows a heater assembly including a stainless steel mesh 56 secured to copper foil contacts 52. The copper contacts 52 are secured to a polyimide substrate 54. An opening 55 is formed in the polyimide substrate 54. The polyimide substrate is welded to the cartridge housing 24. The capillary material 22, soaked in the aerosol-forming substrate, fills the housing and extends through the opening to contact the mesh 55. The cartridge is received in the body 11 of the device and is shown held between the electrical connector 59 and the mouthpiece portion 12. In this embodiment, the electrical connector 59 is adapted to pierce the polyimide substrate 54, as shown, for making electrical connection with the contacts 52. The electrical connector is made with sharpened ends and is forced into contact with the heater assembly by spring 57. The polyimide substrate may be pre-scored to ensure good electrical contact or may even provide openings so that drilling holes in the substrate is not required. Spring 57 also ensures that good electrical contact between contacts 52 and connector 59 is maintained regardless of the orientation of the system relative to gravity.

[0106] One means of ensuring the correct orientation of the cartridge 20 in the cavity 18 of the device has already been described with reference to Figures 5a and 5b. The locating portion 25 can be formed as part of the molded cartridge housing 24 to ensure the correct orientation. However, it will become apparent that other ways of ensuring the correct orientation of the cartridge are possible. There are almost infinite possibilities for the shape of the cartridge, especially if the housing is injection molded. Once the desired internal volume of the cartridge has been selected, the cartridge shape can be adapted to suit any cavity. Figure 11a shows a bottom view of one possible cartridge housing 70, oriented in two possible orientations. The cartridge housing 70 includes two symmetrically arranged grooves 72. The grooves extend partially or entirely on the upper side of the housing 70. Corresponding ribs (not shown) can be formed in the walls of the cavity of the device so that the cartridge can be received in the cavity in only two possible orientations. In the embodiment of Figure 11a, it is also conceivable to have only a single rib in the cavity, such that one of the grooves 72 is not filled by a rib and can be used as an air flow channel in the device. Of course, it is possible to restrict the cartridge to a single orientation within the cavity by providing only a single groove in the housing. This is illustrated in Figure 11b, which shows a cartridge housing 74 with a single groove 76.

[0107] Although the described embodiment has a cartridge with a housing having a substantially circular cross section, it is of course possible to form the cartridge housing with other shapes, such as a rectangular or triangular cross section, that will ensure the desired orientation within a correspondingly shaped recess and ensure electrical connection between the device and the cartridge.

[0108] The capillary material 22 is advantageously oriented within the housing 24 to carry the liquid to the heater assembly 30. When the cartridge is assembled, the heater filaments 36, 37, 38 can be in contact with the capillary material 22 so that the aerosol-forming substrate can be directly carried to the mesh heater. FIG. 12a is a detailed view of the filaments 36 of the heater assembly, showing the meniscus 40 of the liquid aerosol-forming substrate between the heater filaments 36. It can be seen that the aerosol-forming substrate contacts most of the surface of each filament, such that most of the heat generated by the heater assembly goes directly into the aerosol-forming substrate. In contrast, in a conventional wick and coil heater assembly, only a small portion of the heater wire contacts the aerosol-forming substrate. FIG. 12b is a detailed view similar to FIG. 12a, showing an example of the capillary material 27 extending into the gap between the filaments 36. The capillary material 27 is the first capillary material shown in FIG. 4. It has been found that by providing a capillary material comprising fine thread fibres extending into the interstices between the filaments 36, transport of liquid to the filaments can be ensured.

[0109] In use, the heater assembly operates by resistive heating. Electric current is passed through the filaments 36, 37, 38 under the control of the control electronics 16, heating the filaments to within the desired temperature range. The mesh or array of filaments has a significantly higher electrical resistance than the electrical contacts 32 and electrical connectors 19 so that high temperatures are localized to the filaments. The system may be configured to generate heat by supplying electrical current to the heater assembly in response to a user's puff, or may be configured to generate heat continuously while the device is in an "on" state. Different materials for the filaments may be appropriate for different systems. For example, in a continuous heating system, a graphite filament is appropriate because it has a relatively low specific heat capacity and is compatible with low current heating. In a system operated by puffing, where heat is generated in short bursts using high current pulses, a stainless steel filament with a high specific heat capacity may be more appropriate.

[0110] In a puff-activated system, the device may include a puff sensor configured to detect when a user draws in air through the mouthpiece portion. The puff sensor (not shown) is connected to the control electronics 16, which is configured to supply current to the heater assembly 30 only when it is determined that the user is smoking on the device. Any suitable airflow sensor may be used as the puff sensor, such as a microphone.

[0111] In a contemplated embodiment, changes in the resistivity of one or more of the filaments 36, 38, or the heater element as a whole, may be used to detect changes in the temperature of the heater element. This may be used to adjust the power supplied to the heater element so that it remains within a desired temperature range. Rapid temperature changes may also be used as a means of detecting changes in airflow through the heater element due to smoking by a user of the system. The one or more filaments may be dedicated temperature sensors and may be formed from materials with suitable temperature coefficients of resistance for this purpose, such as iron aluminum alloys, nickel chromium, platinum, tungsten or alloy wires.

[0112] The flow of air through the mouthpiece portion when the system is in use is shown in Figure 1d. The mouthpiece portion includes an internal baffle 17 which is integrally molded with the outer wall of the mouthpiece portion and which causes air to flow over a heater assembly 30 in the cartridge where the aerosol-forming substrate is vaporized as it is drawn from the inlet 13 to the outlet 15. As the air passes over the heater assembly, the vaporized substrate is entrained in the airflow and cooled to form an aerosol before exiting the outlet 15. Thus, in use, the aerosol-forming substrate passes through the heater assembly by passing through the gaps between the filaments 36, 37, 38 as it is vaporized.

[0113] There are numerous possibilities for heater assembly fabrication and materials. Figure 13a is a schematic diagram of a first method of fabricating a heater assembly. A roll of polyimide film 80 is provided with an array of openings 82 therein. The openings 82 can be formed by stamping. Strips of copper foil 84 are plated onto the polyimide film 80 between the openings. A ribbon of stainless steel mesh 86 is then clad onto the polyimide film 80 over the copper foil 84 and over the openings 82 in a direction perpendicular to the copper foil strips. Individual heater assemblies 30 can then be cut or stamped around each opening 82. Each heater assembly 30 includes a section of copper foil that forms an electrical contact on the opposite side of the opening, and a strip of stainless steel mesh spans the entire opening from one section of copper to the other, as shown in Figure 6.

[0114] Figure 13b illustrates another possible manufacturing process. In the process of Figure 13b, a polyimide film 80 of the type used in the process of Figure 13a is clad with stainless steel foil 90. The polyimide film 80 has an array of openings 82 formed therein which are covered by the stainless steel foil 90. The foil 90 is then etched to define the filaments 38 across the openings 82 and to isolate the contact portions on opposite sides of the openings. Individual heater assemblies 92 can then be cut or stamped around each opening 82. This provides a heater assembly of the type shown in Figure 9.

[0115] FIG. 13c illustrates a further alternative process. In the process of FIG. 13c, a graphite-based fiber 100 is first prepared. The graphite-based fiber 100 is suitable for use as a heater filament and includes a band of electrically resistive fibers adjacent to a band of relatively non-conductive fibers. These bands of fibers are woven together with a band of relatively conductive fibers that run at right angles to the resistive, non-conductive fibers. The fiber 100 is then bonded to a layer of polyimide film 80 having an array of apertures 82 of the type described with reference to FIGS. 13a and 13b. Individual heater assemblies 102 can then be cut or stamped around each aperture. Each heater assembly 102 includes a portion of the conductive fiber band opposite the aperture and an electrically resistive fiber band across the aperture.

[0116] The cartridge design shown in Figures 5a and 5b has several advantages. However, alternative cartridge designs using the same type of heater assembly are possible. Figure 14 illustrates an alternative cartridge design suitable for different patterns of airflow through the system. In the embodiment shown in Figure 14, the cartridge 108 is configured to be inserted into the device in the direction indicated by arrow 110. The cartridge 108 includes a housing 112 shaped like a half cylinder and open on one side. A heater assembly 114 is provided across the open side and is glued or welded to the housing 112. The heater assembly 114 includes an electrically insulating substrate 116, such as polyimide, with an opening formed therein. A heater element including a stainless steel mesh 118 and a pair of contact strips 120 is bonded to the electrically insulating substrate 116 and spans the opening. The contact strips 120 are bent around the housing 112 to form contact pads on the curved surface of the housing. The electrical contact pads are configured to contact corresponding contacts (not shown) in the aerosol generating device. The housing 112 is filled with a capillary material (not shown in FIG. 14) that is immersed in an aerosol-forming substrate, as described with reference to the embodiment shown in FIGS. 1a-1d.

[0117] The cartridge shown in Figure 14 is configured for airflow through heater assembly 114 in the direction opposite to that of arrow 110. Air is drawn into the system through an air inlet provided in the body of the device, through heater assembly 114, into the mouthpiece portion of the device (or cartridge) and into the user's mouth. Air drawn into the system may be directed in a parallel direction along mesh 118, for example, by appropriately positioning the air inlet.

[0118] Alternative embodiments of the cartridge 108 are illustrated in Figures 15a and 15b. Figure 15a further includes contact strips 120 extending along its length through the gaps with the mesh 118. Figure 15b further includes contacts 120 that are approximately L-shaped. Both cartridge designs illustrated in Figures 15a and 15b can be used to provide a larger contact area to further ensure easy contact with the contacts 19 if necessary. The strips 120 illustrated in Figure 15a can also be configured to slide within the contacts 19 configured with a rail configuration (not shown) to receive the strips 120 to further position the cartridge. Such a rail type configuration can advantageously provide for periodic cleaning of the contacts 19, as insertion and removal of the cartridge will have a cleaning effect due to the friction of the contacts sliding in and out of the rails.

[0119] Fig. 16 illustrates yet another embodiment of an aerosol generation system with a fluid-permeable electric heater assembly. Fig. 16 illustrates a system in which a heater assembly 30 is provided at the end of the cartridge 20 opposite the mouthpiece portion 12. Airflow enters the air inlet 1601 and passes by the assembly through the air outlet 1603 along a flow path 1605. Electrical contacts may be located at any convenient location. Such a configuration is advantageous as it allows for shorter electrical connections within the system.

[0120] One of ordinary skill in the art could devise other cartridge designs incorporating heater assemblies according to the present disclosure. For example, the cartridge may include a mouthpiece portion, may include multiple heater assemblies, and may have any desired shape. Moreover, the heater assemblies according to the present disclosure may be used in other types of systems previously described, including humidifiers, air fresheners, and other aerosol generating systems.

[0121] The above exemplary embodiments are illustrative and not limiting. In light of the exemplary embodiments discussed above, other embodiments consistent with the above exemplary embodiments will now be apparent to those of ordinary skill in the art.

[0122] In Fig. 17, a cross section of the cartridge system is shown, where the flow path includes airflow in a direction through the cartridge. A fluid permeable heater, e.g., mesh heater 30, includes an electrically conductive heater filament 36 that spans an opening in a housing 400. To seal the top of the housing 400, a sealing layer 48, e.g., a polymer layer, is provided between the top rim of the housing 400 and the heater 30. Additionally, a sealing disk 47, e.g., a polymer disk, is provided on the top side of the heater 30. The sealing disk 47 can be used to control the airflow through the heater, and in particular to provide a restriction of the airflow. A sealing disk can also be placed on the bottom side of the heater 30.

[0123] The cartridge housing 400 contains a liquid containing capillary material, such as a high retention or high release material (HRM) 41, which acts as a liquid reservoir and directs the liquid to the heater 30 for evaporation at the heater. A capillary disk 44 of another capillary material, such as a fabric disk, is disposed between the HRM 41 and the heater 30. The material of the capillary disk 44 may be more heat resistant than the HRM 41 due to its proximity to the heater 30. The capillary disk is kept wetted by the aerosol forming liquid of the HRM to ensure a supply of liquid for evaporation when the heater is activated.

[0124] The housing 400 is provided with an air permeable bottom 45. The air permeable bottom is provided with an air flow inlet 450. The air flow inlet 450 allows air to flow into the housing through the bottom 45 and only in this direction. No air or liquid can exit the housing through the air permeable bottom 45. The air permeable bottom 45 may, for example, comprise a semi-permeable membrane as the air flow inlet 450 or may be a bottom cover that includes one or more one-way valves as described below.

[0125] When the heater is depressed on the side, as occurs during smoking, air can pass into the cartridge through airflow inlet 450. Airflow 200 passes through HRM 41 and through heater 30. Airflow 200 containing the aerosol then flows to the downstream end of the aerosol generating device, preferably into a channel located centrally in the mouthpiece.

[0126] The side walls of the housing 400 may also be provided with lateral air permeable portions 46 to provide rear airflow into the housing. The lateral air permeable portions 46 may be designed as airflow inlets 450 in the air permeable bottom 45.

[0127] In Figure 18, the layout and function of the cartridge system is essentially the same as that shown in Figure 10. However, the HRM 41 is provided with a central opening 412. Air entering the airflow inlet 450 in the bottom 45 of the housing passes through the central opening 412. Airflow passes through the side of the HRM within the cartridge. Optional lateral air permeable portions 46 in the side walls of the housing 400 may provide lateral airflow through the HRM 41.

[0128] In Figure 19, an exploded view of the cartridge system shown in Figure 11 is shown. A ring-like tubular HRM 41 is provided within a housing 400. The bottom 45 of the housing is a disk including a one-way valve 49 located in the center of the disk and aligned with a central opening 412 within the HRM 41. Such a one-way valve may be a commercially available valve, such as those used in medical devices or baby bottles, for example.

[0129] Figure 20 is a cross-section of another embodiment of the cartridge system. The same reference numbers are used for the same or similar elements. In this embodiment, a housing 400 is filled with an aerosol-forming liquid 411. The housing may be made of metal, a plastic material (e.g. a polymeric material) or glass. The valve 49 may be attached directly to the bottom 45 of the housing. The bottom 45 may be provided with a recess for airtight assembly with the valve. The valve is preferably made of a flexible material so that an airtight assembly with the bottom material may be achieved.

[0130] In the above cartridge systems illustrated in Figures 17-20, the cartridge housing 400 may be a separate cartridge container, for example in addition to the cartridge housing illustrated in Figure 1. In particular, the liquid containing cartridge 411 is a pre-manufactured product and may be inserted into a cartridge housing provided in the aerosol generation system to receive the pre-manufactured cartridge.

[0131] 1. An aerosol generating system comprising: a liquid reservoir having a housing for holding a liquid aerosol-forming substrate, the housing having an opening; a fluid permeable heater assembly including a substantially planar array of electrically conductive filaments, said fluid permeable heater assembly secured to said housing and extending across said opening in said housing; The area of ​​the conductive filament array is 25 mm 2 An aerosol generating system. 2. The aerosol generation system described in 1, wherein the heater assembly is substantially planar. 3. The aerosol generating system of 2, further comprising a capillary medium, the capillary medium being substantially the same size and shape as the heater assembly, the capillary medium being provided in contact with the heater assembly, and the liquid aerosol-forming substrate being drawn through the capillary medium to the conductive filament. 4. An aerosol generation system described in any of 1 to 3, wherein the system includes a main unit and a cartridge removably coupled to the main unit, the liquid storage portion and the heater assembly are provided within the cartridge, and the main unit includes a power source. 5. An aerosol generating system described in any one of 1 to 4, wherein the multiple filaments form a mesh. 6. An aerosol generating system described in any one of 1 to 4, wherein the plurality of filaments are arranged parallel to each other. 7. The aerosol generation system described in 3, wherein the capillary material extends into the gaps between the filaments. 8. The aerosol generation system described in 7 or 8, wherein the capillary material comprises a first capillary material and a second capillary material, the first capillary material is in contact with the heater assembly, the second capillary material is in contact with the first capillary material and is spaced apart by the heater assembly and the first capillary material, and the first capillary material has a higher thermal decomposition temperature than the second capillary material. 9. The aerosol generation system described in 8, wherein the second capillary material holds 20 to 160 mg of the liquid. 10. The aerosol generating system described in 9, wherein the thermal decomposition temperature of the first capillary material is at least 160°C, and preferably at least 250°C. 11. An aerosol generation system described in any one of 1 to 10, wherein the heater assembly includes at least one filament made of a first material and at least one filament made of a second material different from the first material. 12. An aerosol generation system as described in 1 to 11, further comprising an electrical circuit connected to the heater assembly and a power source, the electrical circuit configured to monitor the electrical resistance of the heater assembly or one or more filaments of the heater assembly, and to control the power supply from the power source to the heater assembly in response to the electrical resistance of the heater assembly or one or more filaments. 13. An aerosol generating system described in any one of 1 to 12, wherein the heater assembly includes an electrically insulating substrate on which the filament is supported. 14. An aerosol generation system described in any one of 1 to 13, wherein the heater assembly includes conductive contacts in contact with a plurality of the filaments. 15. An aerosol generating system described in any one of 1 to 14, wherein the system is an electrically operated smoking system. 16. A cartridge for use in an electrically operated aerosol generating system, comprising: a liquid reservoir having a sturdy housing for holding a liquid aerosol-forming substrate, said housing having an opening; A fluid permeable heater assembly including a plurality of electrically conductive filaments, the fluid permeable heater assembly being secured to the housing and extending across an opening in the housing. 17. The cartridge of claim 16, wherein the heater assembly is substantially planar. 18. A cartridge as described in any of 16 or 17, wherein the plurality of filaments form a mesh. 19. A cartridge according to any one of 16 or 17, wherein the plurality of filaments are arranged parallel to one another. 20. A cartridge described in any one of 16 to 19, wherein the housing of the liquid storage portion comprises a capillary material. 21. The cartridge of claim 20, wherein the capillary material extends into the gaps between the filaments. 22. The cartridge of claim 20 or 21, wherein the capillary material comprises a first capillary material and a second capillary material, the first capillary material in contact with the heater assembly, the second capillary material in contact with the first capillary material and spaced apart by the heater assembly and the first capillary material, and the first capillary material has a higher thermal decomposition temperature than the second capillary material. 23. A cartridge according to any of 16 to 22, wherein the heater assembly includes at least one filament made of a first material and at least one filament made of a second material different from the first material. 24. A cartridge as described in any of 16-23, wherein the heater assembly includes an electrically insulated substrate on which a filament is supported, the filament extending across an opening formed in the substrate. 25. A cartridge described in any one of 16 to 24, wherein the heater assembly has conductive contacts in contact with multiple of the filaments. 26. The cartridge of claim 25, wherein the heater assembly extends in a lateral plane and the conductive contacts extend laterally beyond the housing of the liquid storage portion. 27. A method of manufacturing a cartridge for use in an electrically operated aerosol generating system, comprising: Providing a liquid reservoir comprising a housing having an opening; filling the liquid reservoir with a liquid aerosol-forming substrate; and securing a fluid-permeable heater assembly including a plurality of conductive filaments to the liquid storage portion, the fluid-permeable heater assembly extending across an opening in a housing of the liquid storage portion. 31. A cartridge for use in an electrically operated aerosol generating system, comprising: a liquid reservoir (20) having a sturdy housing (24) for holding a liquid aerosol-forming substrate, said housing having an opening; and a fluid-permeable heater assembly (30) including a plurality of conductive filaments, the conductive filaments having a diameter between 10 μm and 100 μm, the fluid-permeable heater assembly being secured to a housing and extending across an opening in the housing. 32. The cartridge of claim 31, wherein the heater assembly (30) is substantially planar. 33. The cartridge according to 31 or 32, wherein the plurality of filaments form a mesh (36). 34. A cartridge according to any one of 31 to 33, wherein the plurality of filaments are arranged parallel to one another. 35. The cartridge of claim 31 or 32, wherein the housing of the liquid storage portion comprises a capillary material (22, 27). 36. The cartridge of claim 35, further comprising a capillary medium, said capillary medium being substantially the same size and shape as said heater assembly, said capillary material (22, 27) being provided in contact with said heater assembly, and said liquid aerosol-forming substrate being drawn through said capillary medium to said conductive filament. 37. A cartridge as described in 35 or 36, wherein the capillary material (22, 27) extends into the gaps between the filaments. 38. The cartridge of claim 35, 36 or 37, wherein the capillary material comprises a first capillary material (27) and a second capillary material (28), the first capillary material in contact with the heater assembly, the second capillary material in contact with the first capillary material and spaced apart by the heater assembly and the first capillary material, and the first capillary material has a higher thermal decomposition temperature than the second capillary material. 39. The cartridge of claim 38, wherein the second capillary material holds between 20 and 160 mg of the liquid. 40. The thermal decomposition temperature of the first capillary material is at least 160°C. R 39. The cartridge according to claim 39. 41. A cartridge as described in any of 31-40, wherein the heater assembly includes at least one filament made of a first material and at least one filament made of a second material different from the first material. 42. A cartridge according to any of 31 to 41, wherein the heater assembly (30) includes an electrically insulating substrate (34) on which a filament is supported. 43. A cartridge according to any one of 31 to 42, wherein the heater assembly has conductive contacts (32) in contact with the multiple filaments. 44. The cartridge of claim 43, wherein the heater assembly extends in a lateral plane and the conductive contacts (32) extend laterally beyond the housing of the liquid reservoir. 45. An aerosol generating system comprising a main unit (10) and a cartridge (20) as described in any one of 31 to 44, wherein the cartridge is removably coupled to the main unit, and the main unit comprises a power source (14). 46. ​​The aerosol generation system described in 45, further comprising an electrical circuit (16) connected to the heater assembly and a power source, the electrical circuit configured to monitor the electrical resistance of the heater assembly or one or more filaments of the heater assembly and to control the supply of power from the power source to the heater assembly in response to the electrical resistance of the heater assembly or one or more filaments. 47. A method of manufacturing a cartridge for use in an electrically operated aerosol generating system, comprising: Providing a liquid reservoir comprising a housing having an opening; filling the liquid reservoir with a liquid aerosol-forming substrate; fixing a fluid-permeable heater assembly to the liquid storage portion, the fluid-permeable heater assembly including a plurality of conductive filaments, the conductive filaments having a diameter between 10 μm and 100 μm, the fluid-permeable heater assembly extending across an opening in a housing of the liquid storage portion; The manufacturing method comprising the steps of:

Claims

1. 1. A cartridge for use in an electrically operated aerosol generation system, comprising: a liquid reservoir comprising a housing for holding a liquid aerosol-forming substrate, the housing having an opening; a fluid permeable heater assembly including at least one filament, said fluid permeable heater assembly secured to said housing and extending across said opening in said housing; Including, the cartridge.

2. The area of ​​the at least one filament is 25 mm 2 2. The cartridge of claim 1, wherein:

3. The cartridge of claim 1 or 2, wherein the fluid permeable heater assembly is substantially planar.

4. A cartridge according to any one of claims 1 to 3, further comprising a mouthpiece portion.

5. The cartridge of any one of claims 1 to 4, wherein the housing of the liquid storage portion comprises a capillary material configured to convey a liquid aerosol-forming substrate to the heater assembly.

6. 6. The cartridge of claim 5, wherein the capillary material comprises a first capillary material and a second capillary material, the first capillary material in contact with the heater assembly, the second capillary material in contact with the first capillary material and spaced from the heater assembly by the first capillary material, and the first capillary material has a higher thermal decomposition temperature than the second capillary material.

7. The cartridge of claim 6, wherein the second capillary material holds between 20 and 160 mg of the liquid.

8. 8. The cartridge of claim 7, wherein the pyrolysis temperature of the first capillary material is at least 160°C.

9. The cartridge of any one of claims 1 to 8, wherein the heater assembly comprises an electrically insulating substrate on which the at least one filament is supported.

10. The cartridge of claim 9 , wherein the at least one filament extends across an opening formed in the electrically insulating substrate.

11. 11. The cartridge of any one of claims 1 to 10, wherein the heater assembly includes at least one filament made from a first material and at least one filament made from a second material different from the first material.

12. The cartridge of any one of claims 1 to 11, wherein the heater assembly has an electrically conductive contact in contact with the at least one filament.

13. The cartridge of claim 12 , wherein the conductive contact is integral with the at least one filament.

14. 14. A cartridge according to claim 12 or 13, wherein the heater assembly extends in a lateral plane and the conductive contacts extend laterally beyond the housing of the liquid reservoir.

15. 15. The cartridge of any one of claims 1 to 14, wherein the liquid storage portion is located on a first side of the at least one filament and an airflow channel is located in the liquid storage portion from an opposite side of the at least one filament such that, in use, air flow passing through the at least one filament is entrained in vaporized liquid aerosol-forming substrate.

16. The cartridge of any one of claims 1 to 15, wherein the housing comprises a cap and a reservoir, the cap closing the reservoir and the cap in close contact with the heater assembly.

17. 17. An aerosol generation system comprising a main unit and a cartridge according to any one of claims 1 to 16, said cartridge being removably coupled to said main unit, said main unit comprising a power source.

18. 18. The aerosol generation system of claim 17, further comprising an electrical circuit connected to the heater assembly and a power source, the electrical circuit configured to monitor the electrical resistance of the heater assembly or one or more filaments of the heater assembly and control the supply of power from the power source to the heater assembly in response to the electrical resistance of the heater assembly or one or more filaments.

19. 19. An aerosol generating system as described in claim 17 or 18, wherein the system is an electrically operated smoking system.

20. 1. A method of manufacturing a cartridge for use in an electrically operated aerosol generation system, comprising: providing a liquid reservoir comprising a housing having an opening; filling said liquid reservoir with a liquid aerosol-forming substrate; securing a fluid permeable heater assembly including at least one filament to the liquid storage portion, the fluid permeable heater assembly extending across the opening in the housing of the liquid storage portion; A method comprising:

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