The present invention relates to a heater assembly for an aerosol-generating system. In particular, but not exclusively, the present invention relates to a heater assembly for an aerosol-generating system having a transport body for transporting a liquid aerosol-forming substrate from a storage unit to a fluid permeable heating element, wherein, upon heating, components of the liquid aerosol-forming substrate are vaporised to form an inhalable aerosol. The present invention further relates to a method of manufacturing the heater assembly. Aspects of the invention relate to heater assemblies for an aerosol-generating system, and to cartridges for an aerosol-generating system.

Handheld electrically operated aerosol-generating devices and systems are known that consist of a device portion comprising a battery and control electronics, a portion for containing or receiving a liquid aerosol-forming substrate and an electrically operated heater for heating the aerosol-forming substrate to generate an aerosol. The heater of such handheld electrically operated aerosol-generated devices frequently comprises a coil of wire which is wound around an elongate wick which transfers liquid aerosol-forming substrate from the liquid storage portion to the heater. An electric current can be passed through the coil of wire to heat the heater and thereby generate an aerosol from the aerosol-forming substrate. A mouthpiece portion is also included on which a user may puff to draw aerosol into their mouth.

In addition to the wick, the liquid storage portion may comprise an absorbent material for holding the liquid aerosol-forming substrate. Therefore, manufacturing a heater assembly for known aerosol-generating devices and providing a means of transporting liquid aerosolforming substrate to the heating wire can involve the assembly of at least three components. This creates complexity for the assembly line and the number of manufacturing steps involved.

The present disclosure relates to a heater assembly for an aerosol-generating system. The heater assembly may comprise a fluid permeable heating element for heating a liquid aerosol-forming substrate to form an aerosol. The heater assembly may comprise a transport body. The transport body may extend along a longitudinal axis of the heater assembly from a first end surface to a second end surface. The second end surface of the transport body may be coupled with a fluid permeable surface of the fluid permeable heating element. The transport body may be adapted to convey liquid aerosol-forming substrate to the fluid permeable surface of the fluid permeable heating element. The transport body may be formed of a porous sintered ceramic material. The porous sintered ceramic material may comprise a plurality of pores. The plurality of pores may be configured to transport the liquid aerosol- forming substrate through the transport body from the first end surface to the second end surface by capillary action.

According to the present invention there is provided a heater assembly for an aerosolgenerating system. The heater assembly comprises a fluid permeable heating element for heating a liquid aerosol-forming substrate to form an aerosol; and a transport body extending along a longitudinal axis of the heater assembly from a first end surface to a second end surface, wherein a fluid permeable surface of the fluid permeable heating element is coupled with the second end surface of the transport body. The transport body is adapted to convey liquid aerosol-forming substrate to the fluid permeable surface of the fluid permeable heating element. Further, the transport body is formed of a porous sintered ceramic material. The porous sintered ceramic material comprises a plurality of pores configured to transport the liquid aerosol-forming substrate through the transport body from the first end surface to the second end surface by capillary action.

As used herein, the term “aerosol-forming substrate” refers to a substrate capable of releasing volatile compounds that can form an aerosol. Volatile compounds may be released by heating the aerosol-forming substrate.

As used herein, the term “capillary action” is intended to refer to a process of a liquid flowing in a narrow space, generally of the form of a tube, without the assistance, or in some circumstances even in opposition to, any external forces like gravity. The process is driven by intermolecular forces between the liquid and the surrounding solid surfaces.

As used herein, the term “fluid permeable” with respect to the heater means that the heater allows a fluid, for example, a gas or a liquid, to pass through it. For example, it allows liquid aerosol-forming substrate to pass into the pores in the heater to be vaporised and it allows vaporised aerosol-forming substrate formed at the heater to leave the pores in the heater.

As used herein, the term “porous” means formed from a material that has a plurality of openings and that is permeable to the liquid aerosol-forming substrate and allows the liquid aerosol-forming substrate to migrate through it by means of the openings. As used herein, the term “pores” refers to these openings. As used herein, the term “porous member” refers to a component of the heater assembly that has one such plurality of openings. As will be discussed in more detail, below, the porous member of the heater assembly in accordance with the present invention is able to convey the liquid aerosol-forming substrate to the heater by capillary action.

The porous sintered ceramic material may be engineered such that its capacity derives inherently from its architecture. As described briefly above, a heater assembly in accordance with the present invention comprises a transport body being adapted to convey liquid aerosol-forming substrate from end to end through the transport body. The transport body may be provided in the form of a porous sintered ceramic material that comprises a plurality of pores configured to transport the liquid aerosol-forming substrate through the transport body between two opposite end surfaces of the transport body by capillary action. It has advantageously been observed that the characteristics of the porous sintered ceramic material may be greatly enhanced by controlling the size and amount of pores. More advantageously, the provision of a transport body being formed of a porous sintered ceramic material, in particular of a porous sintered ceramic material comprising a plurality of pores of a controlled average size, allows to significantly improve the capillary action extended by the transport body over the liquid aerosol-forming substrate. This means that heater assemblies in accordance with the present invention have been found to display reduced lateral flow and provide for a more efficient and consistent delivery of liquid aerosol-forming substrate from the storage unit to the fluid permeable heating element.

In certain embodiments, the porous sintered ceramic material may have at least 50 percent of the pores with an average diameter of less than or equal to 65 micrometres. Preferably, at least 50 percent of the pores with an average diameter of less than or equal to 55 micrometres. More preferably, at least 50 percent of the pores with an average diameter of less than or equal to 50 micrometres. Even more preferably, at least 50 percent of the pores with an average diameter of less than or equal to 40 micrometres.

In preferred embodiments, the porous sintered ceramic material may have at least 50 percent of the pores with an average diameter of less than or equal to 30 micrometres. Preferably, at least 55 percent of the pores in the porous sintered ceramic material have an average diameter of less than or equal to 30 micrometres. More preferably, at least 60 percent of the pores in the porous sintered ceramic material have an average diameter of less than or equal to 30 micrometres. Even more preferably, at least 65 percent of the pores in the porous sintered ceramic material have an average diameter of less than or equal to 30 micrometres. In particularly preferred embodiments, at least 70 percent of the pores or at least 75 percent of the pores or at least 80 percent of the pores in the porous sintered ceramic material have an average diameter of less than or equal to 30 micrometres.

Particularly, it has been surprisingly found that, by controlling the size of the pores such that a significant fraction of the pores in the transport body have an average diameter below the threshold of 30 micrometres, the capillary action exerted by the transport body over the liquid aerosol-forming substrate is further enhanced as well as the lateral flow is further lowered. In some embodiments, at least 50 percent of the pores in the porous sintered ceramic material have an average diameter of at least 15 micrometres. Preferably, at least 50 percent of the pores in the porous sintered ceramic material have an average diameter of at least 20 micrometres.

In certain embodiments of the present invention, the porous sintered ceramic material may be a sintered freeze-casting ceramic material. Freeze-casting may model the porous structure of the porous sintered ceramic material by the solidification of a solvent. The pores of the porous structure may represent a replica of the solvent crystals, as their formation and growth may yield specific dimensions of pores and porosity degree. As will be discussed in greater detail below, it has also been found that adjusting the grain size of the powder to be sintered or the sintering temperature and duration may not be enough to enable a fine control of the diameter of the channels available to convey the liquid aerosol-forming substrate through the transport body. On the other hand, it has been surprisingly found that combining suitable ceramic powder particles with a non-water soluble solvent, such as camphene, and subjecting the resulting slurry to freeze-casting followed by sintering allows for a much more accurate control over the size of the pores within the sintered freeze-cast ceramic material. Under these circumstances, transport bodies are obtained that display desirable retention and transport properties and, in particular, highly desirable levels of capillary action that ensure a reliable and consistent delivery of liquid aerosol-forming substrate to the fluid permeable heating element.

In some embodiments, the porous freeze-casting sintered ceramic material may be formed from a slurry containing liquid camphene and at least one of aluminium oxide powder and aluminium silicate powder.

As used herein, the term “slurry” is intended to mean a mixture of solids suspended in a liquid. The slurry may be made by ball-milling the aluminium oxide powder or aluminium silicate powder in liquid camphene. As used herein, the term “ball-milling” is intended to indicate a type of grinder that works on the principle of impact and attrition as the blending and size reduction of a feed is achieved by impact of some balls, which rotate in a shell and cascade down on to the feed.

The aluminium oxide powder and the aluminium silicate powder may be dried in order to eliminate any water traces before the ball-milling process. The dried aluminium oxide powder or the dried aluminium silicate powder may be mixed in the liquid camphene, for example inside a ZrO? drum, and ZrO? milling balls may be used in the drum. Alternatively but not exclusively, the drum may be lined with an abrasion-resistant material such as manganese steel or rubber lining and the balls may be made of chrome steel, stainless steel, ceramic, or rubber. The ball-milling process may be carried out for four hours to six hours at about 50 - 85 Celsius degrees. The amount of aluminium powder to be used to make the slurry may differ basing on the level of porosity to be achieved, and it may vary between 5 and 60 percent of the total weight of the slurry. The amount of aluminium oxide powder may vary between 45 and 50 percent of the total weight of the slurry. The amount of aluminium silicate powder may vary between 35 and 45 percent of the total weight of the slurry.

Silicon moulds may be used to cast the slurry and they may be pre-cooled before the slurry, being warmer than the pre-cooled silicon moulds, is poured therein. Preferably, the silicon moulds are pre-cooled at about 20 to about 25 Celsius degrees. Because the mould in which the slurry is poured represents a cold surface for the slurry, the solvent crystals are solicited to grow vertically, along the direction of the imposed thermal gradient. Different thermal gradients may be imposed and the isotropic or anisotropic cooling of the slurry may induce homogeneous or directional solidification. The silicon moulds may induce a segregation phenomenon wherein the aluminium powder particles in suspension in the slurry are rejected by the moving solidification front, concentrated and entrapped in-between the crystals of the solvent formed during to the solidification process. The temperature of the solidification process may depend on the solvent. The temperature of the solidification process may be between 35 and 50 Celsius degrees, when camphene is used as solvent. In certain embodiments, the plurality of pores of the porous sintered ceramic material may comprise pores having a dendrite structure extending along a direction of crystals formed upon freezing the liquid camphene.

As used herein, the term “dendrite structure” is intended to refer to a tree-like structure of crystals growing as the molten material solidifies, which represents the shape produced by faster growth along energetically favourable crystallographic directions.

In the case of camphene being used as a solvent, the solidification of liquid camphene may lead to the formation of clearly defined dendrite crystals. Dendrites of the solidified solvent grow into the liquid, pushing the aluminium particles into the interdendritic spaces. This morphology of the crystals may lead to the formation of a dendritic porous structure.

The shape of the silicon moulds may dictate the shape of the transport body. The shape of the silicon moulds may be substantially cylindrical. The diameter of the silicon mould may be of 3 millimetres, 4 millimetres, 5 millimetres, 6 millimetres, 7 millimetres, 8 millimetres, 9 millimetres, 10 millimetres, 11 millimetres, 12 millimetres, 13 millimetres, 14 millimetres, 15 millimetres. The thickness of the silicon mould may be of 1 millimetre, 2 millimetres, 3 millimetres, 4 millimetres, 5 millimetres, 6 millimetres, 7 millimetres, 8 millimetres, 9 millimetres, 10 millimetres. In some embodiments, the transport body may be substantially cylindrical and may have a diameter of at least 5 millimetres. In other embodiments, the transport body may be substantially cylindrical and may have a diameter of less than or equal to 11 millimetres. In some embodiments, the transport body may be substantially cylindrical and may have a length of at least 2 millimetres. In other embodiments, the transport body may be substantially cylindrical and may have a length of less than or equal to 9 millimetres.

Advantageously, a greater control of the resulting structure of the porous sintered ceramic material allows the material to be better adapted for its intended use. The morphology of the porosity may be varied based on the amount of aluminium powders and camphene used to form the slurry. The morphology of the porosity may determine different level of chemical resistance and thermal resistance of the porous sintered ceramic material.

Advantageously, increasing the thermal resistance of the porous sintered ceramic material may reduce the thermal degradation of the porous sintered ceramic material, when exposed to certain temperature conditions.

As used herein, the term “thermal resistance” is intended to mean the ability of a substance to resist a heat flow and avoid undergoing thermal degradation.

In certain embodiments, the porous sintered ceramic material may have a thermal resistance up to 200 Celsius degrees.

The liquid aerosol-forming substrate is a liquid substrate, named also as e-liquid, capable of releasing volatile compounds that can form an aerosol. The volatile compounds may be released by heating the aerosol forming substrate.

The liquid aerosol-forming substrate may comprise plant-based material. The liquid aerosol-forming substrate may comprise tobacco. The liquid aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds, which are released from the aerosol-forming substrate upon heating. The liquid aerosol-forming substrate may alternatively comprise a non-tobacco-containing material. The liquid aerosolforming substrate may comprise homogenised plant-based material. The liquid aerosolforming substrate may comprise homogenised tobacco material. The liquid aerosol-forming substrate may comprise at least one aerosol-former. An aerosol-former is any suitable known compound or mixture of compounds that, in use, facilitates formation of a dense and stable aerosol and that is substantially resistant to thermal degradation at the operating temperature of the system. Suitable aerosol-formers are well known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, 1 ,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol formers are polyhydric alcohols or mixtures thereof, such as triethylene glycol, 1 ,3-butanediol and, most preferred, glycerine. The liquid aerosol-forming substrate may comprise other additives and ingredients, such as flavourants. Advantageously, increasing the chemical resistance of the porous sintered ceramic material may reduce the chemical degradation of the porous sintered ceramic material, exposed to the aerosol-forming substrate, particularly when comprising benzoic acid. As used herein, the term “chemical resistance” is intended to mean the ability of a substance to endure itself from chemical attack and avoid undergoing a chemical process and a chemical transformation or chemical degradation.

According to the present invention, the chemical resistance may be assessed indirectly by measuring a variation in the weight of the porous sintered ceramic material following exposure for a predetermined period of time to a given liquid aerosol-forming substrate.

Particularly, such chemical resistance may be assessed in terms of percentage weight loss.

In certain embodiments, the porous sintered ceramic material may in particular have a chemical resistance to the liquid aerosol forming substrate. Thus, the chemical resistance may be assessed indirectly by measuring the percentage weight loss following three cycles of exposure to benzoic acid, each cycle having a duration of 30 minutes. The behaviour of a porous sintered ceramic material in accordance with the invention may thus also be compared with the behaviour of a wicking material prepared in line with the state of the art (for example, a non-sintered wicking material) and exposed to benzoic acid under the same conditions and for the same duration.

Preferably, the porous sintered ceramic material according to the present invention undergoes a percentage weight loss of less than 5 percent when exposed at least three times for at least 30 minutes to a liquid aerosol-forming substrate containing benzoic acid. More preferably, the porous sintered ceramic material according to the present invention undergoes a percentage weight loss of less than 3.5 percent when exposed at least three times for at least 30 minutes to a liquid aerosol-forming substrate containing benzoic acid. Even more preferably, the porous sintered ceramic material according to the present invention undergoes a percentage weight loss of less than 2 percent when exposed at least three times for at least 30 minutes to a liquid aerosol-forming substrate containing benzoic acid. In some preferred embodiments, the porous sintered ceramic material according to the present invention undergoes a percentage weight loss of less than 1 percent when exposed at least three times for at least 30 minutes to a liquid aerosol-forming substrate containing benzoic acid. In some particularly preferred embodiments, the porous sintered ceramic material according to the present invention undergoes a percentage weight loss of less than 0.9 percent when exposed at least three times for at least 30 minutes to a liquid aerosol-forming substrate containing benzoic acid. The chemical resistance of the porous sintered ceramic material may be further increased using electroplating technologies for obtaining micron metal coatings. As used herein, the term “electroplating” refers to a process that produces a metal coating on a solid substrate through the reduction of cations of that metal by means of direct electric current. The electroplating technology may allow to regulate the thickness of the nickel (Ni) coating layer. The electroplating technology may also improve the mechanical resistance of the porous sintered ceramic material.

In such embodiments, the transport body according to the present invention comprises a layer of nickel (Ni) coating the porous sintered ceramic material.

According to the present invention, the fluid permeable heater may be deposited on the porous sintered ceramic material of the transport body, such that the fluid permeable heater may be in direct contact with the outer surface of the porous sintered ceramic material of the transport body. The fluid permeable heater may be deposited over substantially all of an outer surface of the porous sintered ceramic material. The fluid permeable heater may be deposited over substantially all of a porous first end of the porous sintered ceramic material.

Alternatively, the fluid permeable heater may comprise an array of electrically conductive filaments extending along the length of the heater, a plurality of apertures being defined by interstices between the electrically conductive filaments. In such embodiments, the size of the plurality of apertures may be varied by increasing or decreasing the size of the interstices between adjacent filaments. This may be achieved by varying the width of the electrically conductive filaments, or by varying the interval between adjacent filaments, or by varying both the width of the electrically conductive filaments and the interval between adjacent filaments.

As used herein, the term “filament” refers to an electrical path arranged between two electrical contacts. In preferred embodiments, the filaments have a substantially flat crosssection. As used herein, “substantially flat” preferably means formed in a single plane and for example not wrapped around or other conformed to fit a curved or other non-planar shape. A substantially flat heater can be easily handled during manufacture and provides for a robust construction. A filament may be arranged in a straight or curved manner.

According to another aspect of the present invention, there is provided a cartridge for use in an aerosol-generating system, the cartridge comprising a liquid storage portion for holding a liquid aerosol-forming substrate; and any of the heater assembly embodiments described above. In more detail, the cartridge may comprise a liquid storage portion for holding a liquid aerosol-forming substrate, the liquid storage portion being configured to be arranged in an aerosol-generating system such that a first end of a transport body including a first end surface of a heater assembly in line with the foregoing description is able to extend into the liquid storage portion for contact with the liquid aerosol-forming substrate therein.

The fluid permeable heater may be deposited on to a porous first end of the transport body and a second end of the porous sintered ceramic material of the transport body extends into the liquid storage portion for contact with the liquid aerosol-forming substrate therein.

The liquid storage portion may include a housing for holding the liquid aerosol-forming substrate. The housing may have an opening for allowing vaporised aerosol-forming substrate to escape, wherein the porous sintered ceramic material is arranged such that the fluid permeable heater extends across the opening. The opening may be of any appropriate shape. For example the opening may have a circular, square or rectangular shape. The area of the opening may be small, preferably less than or equal to about 25 square millimetres.

In some embodiments, the fluid permeable heater is arranged in such a way that the physical contact area with the liquid storage portion is reduced compared with a case in which the heater is in contact around the whole of the periphery of the liquid storage portion. The fluid permeable heater preferably does not directly contact the perimeter of the liquid storage portion. This may be achieved by providing a spacing between the outer edge of the fluid permeable heater and the periphery of the opening, which spacing can be dimensioned such that thermal contact is significantly reduced. The spacing between the heater and the opening periphery may be between 25 microns and 40 microns. In this way thermal contact to the liquid storage portion is reduced and less heat is transferred to the liquid storage portion, thus increasing efficiency of heating and therefore aerosol generation.

In alternative embodiments, the heater assembly may be provided as an integral part of an aerosol-generating system, rather than forming part of a cartridge for use in the aerosolgenerating system.

According to another aspect of the present invention, there is provided an aerosolgenerating system comprising: an aerosol-generating device; and a cartridge as described above, wherein the cartridge is removably coupled to the aerosol-generating device and the aerosol-generating device includes a power supply for the heater assembly.

As used herein, the cartridge being “removably coupled” to the device means that the cartridge and device can be coupled and uncoupled from one another without damaging either the device or the cartridge.

The cartridge can be exchanged after consumption. As the cartridge holds the aerosol forming substrate and the fluid permeable heater, the heater is also exchanged regularly such that the consistent vaporization conditions are maintained even after longer use of the main unit. The aerosol-generating system may further comprise electrical circuitry connected to the fluid permeable heater and to an electrical power supply, the electric circuitry being configured to monitor an electrical resistance of the fluid permeable heater and to control the supply of power from the electrical power supply to the heater based on the monitored electrical resistance. By monitoring the temperature of the heater, the system can prevent over- or under-heating of the heater and ensure that consistent vaporization conditions are provided.

The electric circuitry may comprise a microprocessor, which may be a programmable microprocessor, a microcontroller, or an application specific integrated chip (ASIC) or other electronic circuitry capable of providing control. The electric circuitry may comprise further electronic components. The electric circuitry may be configured to regulate a supply of power to the heater. Power may be supplied to the fluid permeable heater continuously following activation of the system or may be supplied intermittently, such as on a puff by puff basis. The power may be supplied to the heater in the form of pulses of electrical current.

The power supply may be a battery, such as a lithium iron phosphate battery, within the device. As an alternative, the power supply may be another form of charge storage device such as a capacitor. The power supply may require recharging and may have a capacity that allows for the storage of enough energy for one or more smoking experiences. For example, the power supply may have sufficient capacity to allow for the continuous generation of aerosol for a period of around six minutes, corresponding to the typical time taken to smoke a conventional cigarette, or for a period that is a multiple of six minutes. In another example, the power supply may have sufficient capacity to allow for a predetermined number of puffs or discrete activations of the heater.

The liquid storage portion may be positioned on a first side of the fluid permeable heater and an airflow channel positioned on an opposite side of the heater to the storage portion, such that air flow past the heater entrains vaporised aerosol-forming substrate.

The system may be a handheld aerosol-generating system. The aerosol-generating system may have a size comparable to a conventional cigar or cigarette. The smoking system may have a total length between approximately 30 millimetres and approximately 150 millimetres. The smoking system may have an external diameter between approximately 5 millimetres and approximately 30 millimetres.

According to another aspect of the present invention, there is provided a method of manufacturing a heater assembly for an aerosol-generating system, the method comprising: preparing a slurry comprising liquid camphene and at least one of aluminium oxide powder and aluminium silicate powder; freeze casting the slurry; sintering the freeze cast slurry to obtain a transport body comprising porous sintered ceramic material, wherein sintering the freeze cast slurry may comprise heating the freeze cast slurry for at least 6 hours at a temperature of at least 1200 Celsius degrees.

Freeze casting the slurries may comprise placing them on ice blocks at about minus 20 to minus 27 Celsius degree for about 5 minutes. After solidification of the slurries, a solid body may be yielded. The freeze cast samples may then be demoulded and may undergo sublimation in order to remove the frozen camphene from the solid bodies. Pores may be created in the locations previously occupied by the solvent crystals. The sublimation process may last for about 2 to 4 hours at a temperature of about 30 to 50 Celsius degrees. After the evaporation of the solvent, the solid bodies may be sintered and the macroporosity may be consolidated. Sintering conditions may differ basing on the aluminium powders used to produce the slurries. A sintering regime of about 4 hours at about 1500 to 1600 Celsius degree, and of about 2 hours at about 1550 to 1650 Celsius degree may be used if aluminium oxide is used. A sintering regime of about 4 hours at about 1500 to 1600 Celsius degree, and of about 2 hours at about 1200 to 1300 Celsius degree may be used if aluminium silicate is used.

In certain embodiments of the present invention, the slurry may comprise aluminium oxide powder in an amount of 50 percent of the total weight of the slurry and liquid camphene; the slurry may be prepared at milling regime of 75 Celsius degrees for four hours; the slurry may be freeze-casted for 5 minutes at a temperature of minus 10 Celsius degrees to obtain a solid body characterised by a diameter of 9.74 millimetre and a thickness of 6.28 millimetre. Such solid body may be sintered for 4 hours at a temperature of 1600 Celsius degrees to yield a solid body with a final diameter of 8.38 millimetre and a thickness of 5.09 millimetre and a size of pores of equal or less than 30 micrometre.

In other embodiments of the present invention, the slurry may comprise aluminium oxide powder in an amount of 40 percent of the total weight of the slurry and liquid camphene; the slurry may be prepared at milling regime of 70 Celsius degrees for four hours; the slurry may be freeze-casted for 5 minutes at a temperature of minus 15 Celsius degrees to obtain a solid body characterised by a diameter of 9.60 millimetre and a thickness of 7.15 millimetre. Such solid body may be sintered for 2 hours at a temperature of 1600 Celsius degrees to yield a solid body with a final diameter of 8.47 millimetre and a thickness of 5.89 millimetre and a size of pores of equal or less than 30 micrometre.

In certain other embodiments of the present invention, the slurry may comprise aluminium oxide powder in an amount of 35 percent of the total weight of the slurry and liquid camphene; the slurry may be prepared at milling regime of 70 Celsius degrees for six hours; the slurry may be freeze-casted for 15 minutes at a temperature of minus 25 Celsius degrees to obtain a solid body characterised by a diameter of 9.22 millimetre and a thickness of 6.11 millimetre. Such solid body may be sintered for 4 hours at a temperature of 1600 Celsius degrees to yield a solid body with a final diameter of 7.47 millimetre and a thickness of 4.55 millimetre and a size of pores of equal or less than 30 micrometre.

In other embodiments of the present invention, the slurry may comprise aluminium silicate powder in an amount of 40 percent of the total weight of the slurry and liquid camphene; the slurry may be prepared at milling regime of 70 Celsius degrees for six hours; the slurry may be freeze-casted for 15 minutes at a temperature of minus 6 Celsius degrees to obtain a solid body characterised by a diameter of 9.90 millimetre and a thickness of 7.16 millimetre. Such solid body may be sintered for 4 hours at a temperature of 1250 Celsius degrees to yield a solid body with a final diameter of 8.22 millimetre and a thickness of 5.75 millimetre and a size of pores of equal or less than 30 micrometre.

In still other embodiments of the present invention, the slurry may comprise aluminium oxide powder in an amount of 35 percent of the total weight of the slurry and liquid camphene; the slurry may be prepared at milling regime of 70 Celsius degrees for six hours; the slurry may be freeze-casted for 15 minutes at a temperature of minus19 Celsius degrees to obtain a solid body characterised by a diameter of about 9.03 millimetre and a thickness of 6.45 millimetre. Such solid body may be sintered for 4 hours at a temperature of 1250 Celsius degrees to yield a solid body with a final diameter of 7.62 millimetre and a thickness of 5.49 millimetre and a size of pores of equal or less than 30 micrometre.

The method may further comprise electroplating the transport body comprising porous sintered ceramic material with nickel ions, wherein electroplating the transport body comprising porous sintered ceramic material may comprise forming a nickel layer on the porous sintered ceramic material having a thickness from 10 micrometres to 20 micrometres.

Features described in relation to one or more aspects may equally be applied to other aspects of the invention. In particular, features described in relation to the heater assembly of any of the aspects may be equally applied to the cartridge of other aspects, and vice versa, and features described in relation to the heater assembly or the cartridge of any of the aspects may equally apply to the aerosol-generating system of other aspects or the method of manufacturing.

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

Example Ex1 : A heater assembly for an aerosol-generating system, the heater assembly comprising: a fluid permeable heating element for heating a liquid aerosol-forming substrate to form an aerosol; and a transport body extending along a longitudinal axis of the heater assembly from a first end surface to a second end surface. Example Ex2: A heater assembly according to Ex1 , wherein the fluid permeable surface of the fluid permeable heating element is coupled with the second end surface of the transport body.

Example Ex3: A heater assembly according to Ex2 or Ex1 , wherein the transport body is adapted to convey liquid aerosol-forming substrate to the fluid permeable surface of the fluid permeable heating element.

Example Ex4: A heater assembly according to any preceding example, wherein the transport body is formed of a porous sintered ceramic material.

Example Ex5: A heater assembly according to Ex4, wherein the porous sintered ceramic material comprises a plurality of pores configured to transport the liquid aerosolforming substrate through the transport body from the first end surface to the second end surface by capillary action.

Example Ex6: A heater assembly according to any of Ex4 or Ex5, wherein at least 50 percent of the pores of the porous sintered ceramic material have an average diameter of less than or equal to 30 micrometres.

Example Ex7: A heater assembly according to any of Ex4 or Ex5, wherein at least 75 percent of the pores of the porous sintered ceramic material have an average diameter of less than or equal to 30 micrometres.

Example Ex8: A heater assembly according to any of Ex4 to Ex7, wherein the porous sintered ceramic material is a sintered freeze-cast ceramic material.

Example Ex9: A heater assembly according to Ex8, wherein the sintered freeze-cast material is formed from a slurry.

Example Ex10: A heater assembly according to Ex8 or Ex9, wherein the slurry contains a liquid solvent and a solid powder.

Example Ex11 : A heater assembly according to any of Ex8 to Ex10, wherein the slurry contains liquid camphene and at least one of aluminium oxide powder and aluminium silicate powder.

Example Ex12: A heater assembly according to any of Ex8 to Ex11 , wherein the plurality of pores comprises pores having a structure, such as the structure replicates the growth of crystals formed upon freezing of the liquid solvent.

Example Ex13: A heater assembly according to any of Ex8 to Ex12, wherein the plurality of pores comprises pores having a dendrite structure extending along a direction of growth of crystals formed upon freezing the liquid camphene.

Example Ex14: A heater assembly according to any preceding example, wherein the transport body is substantially cylindrical. Example Ex15: A heater assembly according to Ex14, wherein the transport body has a diameter of at least 5 millimetres.

Example Ex16: A heater assembly according to Ex14, wherein the transport body has a diameter of less than or equal to 11 millimetres.

Example Ex17: A heater assembly according to Ex14, wherein the transport body has a diameter of less than or equal to 2 millimetres.

Example Ex18: A heater assembly according to Ex14, wherein the transport body has a diameter of less than or equal to 9 millimetres.

Example Ex19: A heater assembly according to any of Ex4 to Ex18, wherein the porous sintered ceramic material has a thermal resistance up to 200 °C.

Example Ex20: A heater assembly according to any preceding example, wherein the transport body comprises a layer of nickel coating the porous sintered ceramic material.

Example Ex21 : A heater assembly according to any of Ex4 to Ex20, wherein the porous sintered ceramic material has a chemical resistance to the liquid aerosol forming substrate.

Example Ex22: A cartridge for use in an aerosol-generating system, the cartridge comprising a liquid storage portion for holding a liquid aerosol-forming substrate; and a heater assembly according to any preceding example.

Example Ex23: A cartridge according to Ex22 comprising a heater assembly according to any of Ex1 to Ex21 , wherein a first end of the transport body including the first end surface extends into the liquid storage portion for contact with the liquid aerosol-forming substrate therein.

Example Ex24: An aerosol-generating system comprising an aerosol-generating device and a cartridge according to Ex22 or Ex23, wherein the cartridge is removably coupled to the aerosol-generating device and the aerosol-generating device includes a power supply for the heater assembly.

Example Ex25: A method of manufacturing a heater assembly for an aerosolgenerating system according to any one of Ex1 to Ex21 , the method comprising: preparing a slurry comprising liquid camphene and at least one of aluminium oxide powder and aluminium silicate powder; freeze casting the slurry; sintering the freeze cast slurry to obtain a transport body comprising porous sintered ceramic material.

Example Ex26: A method of manufacturing according to Ex25, wherein sintering the freeze cast slurry comprises heating the freeze cast slurry for at least 6 hours at a temperature of at least 1200 Celsius degrees. Example Ex27: A method of manufacturing according to Ex25, wherein sintering the freeze cast slurry comprises heating the freeze cast slurry for at least 6 hours at a temperature of less than or equal to 1700 Celsius degrees.

Example Ex28: A method of manufacturing according to any one of Ex25 to Ex27, wherein such method further comprises electroplating the transport body comprising porous sintered ceramic material with nickel ions.

Example Ex29: A method of manufacturing according to Ex28, wherein electroplating the transport body comprising porous sintered ceramic material comprises forming a nickel layer on the porous sintered ceramic material having a thickness from 10 micrometres to 20 micrometres.

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

Figure 1 is a schematic illustration of an aerosol-generating system comprising a cartridge and an aerosol-generating device.

Figure 2 is a schematic illustration of another embodiment of an aerosol-generating system comprising a cartridge and an aerosol-generating device.

Figure 1 is a schematic illustration of an aerosol-generating system. The aerosolgenerating system comprises two main components, a cartridge 1 and a main body part or aerosol-generating device 2.

The cartridge 1 comprises a housing containing the heater assembly 3 and a liquid reservoir 4 that contains an aerosol-forming substrate 5.

The heater assembly 3 comprises a fluid permeable heating element 6 and a transport body 7. The transport body 7 is generally of a circular cylindrical shape. The transport body contains a porous sintered ceramic material that is soaked in the liquid aerosol-forming substrate 5. The porous sintered ceramic material is a sintered freeze-casting ceramic material, which porous structure and porosity degree are obtained by solidification of liquid camphene used as solvent.

The pores of the porous structure in accordance with the foregoing description represent a replica of the sublimed camphene crystals. The porous sintered ceramic material actively conveys liquid from one end to another by capillary action. It would be appreciated that the pores and the porous structure are not visible in the Figures since the size of the pores is below the resolution of the Figures.

The aerosol-generating device 2 is portable and has a size comparable to a conventional cigar or cigarette. The device 2 comprises a main body and a mouthpiece 8. The main body contains a power source in the form of a battery (not shown), which may be a rechargeable battery, and electrical connectors (not shown). Electrical connectors provide electrical connection between the control electronics (not shown) and the battery and electrical contacts on the cartridge. The mouthpiece 8 comprises a plurality of air inlets 9 and an outlet 10. In use, a user sucks or puffs on the outlet 10 to draw air from the air inlets 9 and thereafter into the mouth or lungs of the user.

A connection end of the cartridge 1 is removable and it is connected to a corresponding connection end of the aerosol-generating device 2. The connection end of the cartridge 1 and the connection end of the aerosol-generating device 2 have electrical contacts or connections (not shown) which are arranged to cooperate to provide an electrical connection between the cartridge 1 and the aerosol-generating device 2.

An air flow passage extends through the cartridge 1 from an air inlet 9 formed in a side of the housing of the aerosol-generating device 2 past the fluid permeable heating element 6 of the heater assembly 3 and from the heater assembly to a mouthpiece opening 11 .

The components of the cartridge 1 are arranged so that the transport body 7 is between the fluid permeable heating element 6 and the mouthpiece opening 11 .

The aerosol-generating system is configured so that a user can puff or draw on the mouthpiece 8 of the cartridge to draw aerosol from a mixing and homogenizing chamber 12 for aerosol particle release into their mouth through the mouthpiece opening 11. The control circuitry (not shown) controls the supply of electrical power from the battery (not shown) to the cartridge 1 when the system is activated. This in turn controls the amount and properties of the vapour produced by the heater assembly 3. The control circuitry may include an airflow sensor (not shown) and the control circuitry may supply electrical power to the heater assembly 3 when user puffs are detected by the airflow sensor. This type of control arrangement is well established in aerosol-generating systems such as inhalers and e- cigarettes. When a user puffs on the mouthpiece opening 11 , the heater assembly 3is activated and generates a vapour that is entrained in the air flow passing through the mixing and homogenizing chamber 12. The vapour cools within the airflow to form an aerosol 13, which is then drawn into the user’s mouth through the mouthpiece opening 11 .

In operation, the mouthpiece opening 11 is typically the highest point of the system. The construction of the cartridge 18, and in particular the arrangement of the heater assembly 3, is advantageous because it exploits gravity to ensure that the liquid aerosol-forming substrate is delivered to the heater assembly 3 even if the liquid storage compartment is becoming empty, but prevents an oversupply of liquid to the heater assembly which might lead to leakage of liquid into the air flow passage.

Figure 2 is a schematic illustration of an embodiment of an aerosol-generating system comprising a cartridge and an aerosol-generating device. In comparison to the embodiment of Figure 1 , the cartridge in the embodiment of Figure 2 is an inverted cartridge. The inverted cartridge contains a fluid permeable heating element and a transport body, and a reservoir containing an aerosol-forming substrate. As in the embodiment illustrated in Figure 1 , the transport body contains a porous sintered ceramic material. In this inverted configuration of the cartridge, the porous sintered ceramic material of the transport body is always in contact with the aerosol-forming substrate. The aerosol-generating device features a hole 14 provided at the bottom of the aerosol-generating device comprising an air inlet.

For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 5% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.