Technical Field

The present invention relates to an aerosol-generating article, methods of preparing said articles, and an aerosol-generating assembly. In particular, the present invention relates to a method of preparing aerosol-generating articles which includes treating tobacco with a pulsed electric field.

Background

Articles such as cigarettes, cigars and the like bum tobacco during use to create tobacco smoke. Attempts have been made to provide alternatives to these types of articles, which burn tobacco, by creating products that release compounds without burning.

Examples of such products are so-called heat-not-bum products, also known as tobacco heating products or tobacco heating devices, which release compounds by heating, but not burning, the material. The material may be for example tobacco or other non tobacco products or a combination, such as a blended mix, which may or may not contain nicotine.

Other examples of such products include e-cigarette / heat-not-burn hybrid devices, also known as electronic tobacco hybrid devices. These hybrid devices contain a liquid which is vaporised by heating to produce an inhalable vapour or aerosol. The liquid may contain flavourings and/or aerosol-generating substances, such as glycerol and in some instances, nicotine. The vapour or aerosol passes through material in the device and entrains one or more constituents of a substrate material to produce the inhaled medium. The substrate material may be, for example, tobacco, other non-tobacco products or a combination, such as a blended mix, which may or may not contain nicotine. In both tobacco heating products and hybrid devices there is a difficulty in heating the substrate at a relatively low temperature to provide an aerosol which has desirable organoleptic properties to the consumer. Summary

According to a first aspect of the present invention, there is provided a method of making an aerosol-generating article containing an aerosol-generating component, wherein the aerosol-generating article produces an inhalable aerosol upon heating but not burning the aerosol-generating article. The method comprises: providing a tobacco composition; applying a pulsed electric field to the tobacco composition to thereby provide a treated tobacco composition; combining the treated tobacco composition with aerosol-generating agent to provide an aerosol-generating component comprising greater than or equal to about 8% aerosol-generating agent by weight of the aerosol-generating component; and forming the aerosol-generating article to include the aerosol-generating component; wherein the pulsed electric field applied to the tobacco composition has a field strength of greater than or equal to about lOOV/cm and a pulse frequency of greater than or equal to about 20Hz.

In some embodiments, the tobacco composition has a moisture content of from about 10 to 30wt%. In some embodiments, the treated tobacco composition has a moisture content of from about 10 to 30wt%.

In some embodiments, the pulsed electric field has a pulse width of from about 10 ns to 5 x 10 ⁸ ns. In some embodiments, the pulsed electric field has a field strength of less than about 5 kV/cm. In some embodiments, the applying of the pulsed electric field is carried out for a duration of from about 10 to 600 minutes. In some embodiments, the tobacco composition comprises leaf tobacco, tobacco strips, tobacco stems, ground tobacco or a combination thereof.

In some embodiments, combining the treated tobacco composition with the aerosol- generating agent to provide the aerosol-generating component comprises mixing the aerosol-generating agent with the treated tobacco composition.

In other embodiments, combining the treated tobacco composition with the aerosol generating agent to provide an aerosol-generating component and forming the aerosol- generating article comprises providing the aerosol-generating agent in a first chamber of a housing, and providing the treated tobacco composition in a second chamber of the housing, the first chamber being in fluid communication with the second chamber.

According to a second aspect of the invention there is provided an aerosol-generating article for use in an aerosol-generating assembly, the aerosol-generating article containing an aerosol-generating component, the aerosol-generating component comprising: a treated tobacco composition, wherein the treated tobacco composition comprises tobacco to which a pulsed electric field has been applied, the pulsed electric field having a field strength of greater than or equal to about lOOV/cm and a pulse frequency of greater than or equal to about 20Hz; and aerosol-generating agent, wherein the aerosol-generating agent is present in the aerosol-generating article in an amount of greater than or equal to about 8% by weight of the aerosol-generating article.

In some embodiments, the treated tobacco composition and the aerosol-generating agent are provided as a mixture wherein the treated tobacco composition and the aerosol-generating agent are distributed evenly throughout the mixture. In some embodiments, the aerosol-generating article comprises a first chamber containing the treated tobacco composition and a second chamber containing the aerosol-generating agent. The first chamber may be configured to be downstream of the second chamber in use in the aerosol-generating assembly. In these embodiments, the aerosol-generating agent may be a liquid. In some embodiments the aerosol-generating article has a nicotine content of from about 0.5 to 2% by weight.

According to a further aspect of the present invention there is provided an aerosol generating assembly comprising: a treated tobacco composition; aerosol-generating agent; and a heat source disposed to heat, but not burn, the treated tobacco composition and/or the aerosol-generating agent, wherein the treated tobacco composition comprises tobacco to which a pulsed electric field has been applied, the pulsed electric field having a field strength of greater than or equal to about lOOV/cm and a pulse frequency of greater than or equal to about 20Hz.

In some embodiments, the heat source comprises an electrically resistive heating element, an infrared heating element, a photonic source, an inductive heating element, or a combination thereof.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 shows an embodiment of an aerosol-generating article as described herein. Figure 2 shows a further embodiment of an aerosol-generating article as described herein, the article containing an aerosol cooling element. Detailed Description

In one aspect, the present invention relates to a method of preparing an aerosol generating article.

The inventors have found that tobacco compositions used in combustible products are not optimal for use in tobacco heating products or hybrid devices because the tobacco flavourings released on combustion do not become entrained in the volatilised liquid at the device operating temperature. Surprisingly, it has been found that by carrying out the present method, there is provided an aerosol-generating article which releases more tobacco flavourings and the like at the lower operating temperatures of aerosol generating assemblies.

The method first comprises providing a tobacco to which an electric field is to be applied. Suitably, in the context of them method described herein, this tobacco may be referred to as a tobacco composition.

The tobacco composition may be provided in any suitable form. For example, the tobacco composition may comprise or consist of leaf tobacco (single grades or blends, cut rag or whole leaf, including Virginia (flue-cured) and/or Burley and/or Oriental) tobacco stem, tobacco rib, ground tobacco, and combinations thereof. In preferred examples, the tobacco composition comprises or consists of leaf tobacco; in particular, whole leaf tobacco. The tobacco composition may comprise uncured tobacco, or cured tobacco.

In some embodiments, the tobacco composition has a moisture content of less than about 30wt%, 15wt%, or 20wt%. In some embodiments, the tobacco composition has a moisture content of from about 5 to 40wt%, for example from about 10 to 30wt%, 10 to 20wt%, or 13 to 17wt%. In some embodiments, the tobacco composition has a moisture content of at least about 5wt%, 10wt%, or 13wt%. Preferably, the tobacco composition is not provided in a liquid medium such as a slurry. That is, the tobacco is preferably provided in dry form. Surprisingly it has been found that pulsed electric field treatment can be effectively carried out on dry tobacco. Treating dry tobacco rather than tobacco in a liquid medium such as slurried tobacco may simplify the downstream processing required.

The method further comprises applying a pulsed electric field to the tobacco composition. Pulsed electric field (PEF) treatment comprises applying short pulses of high voltage through a composition which is placed between two electrodes. Application of the pulsed electric field to the tobacco composition provides a treated tobacco.

Surprisingly it has been found that applying PEF treatment to a tobacco composition modifies the tobacco so that it releases flavour components at a lower temperature compared with untreated tobacco. That is, this method improves the organoleptic properties of the tobacco for it to be used in an aerosol-generating article which is heated, but not burned, to provide an inhalable aerosol.

Without wishing to be bound by theory, applying a pulsed electric field to the tobacco composition may induce cell membrane permeabilization through a phenomenon called “electroporation”. However, for the avoidance of doubt, the present method is not a method of extracting components from a tobacco composition; flavouring components are not removed from the tobacco by applying a pulsed electric field. Rather, the pulsed electric field modifies the tobacco so that more of its components may be released from an aerosol-generating article at a lower temperature compared with untreated tobacco.

In preferred embodiments, no components are removed from the treated tobacco before it is included in an aerosol-generating article.

The pulsed electric field can be defined by a variety of parameters, such as field strength, pule frequency, pulse duration, and pulse shape. The parameters of the pulsed electric field are selected to that the organoleptic properties of the tobacco are improved, but the tobacco is not disintegrated. The parameters of the pulsed electric field defined herein refer to the parameter as experienced by the tobacco composition in the pulsed electric field (i.e. the properties of the electric field “at” the tobacco composition). The pulsed electric field applied to the tobacco composition has a field strength of greater than or equal to about 100 V/cm (0.1 kV/cm). In some embodiments, the field strength is greater than or equal to about 500 V/cm (0.5 kV/cm), or 1 kV/cm. In some embodiments, the field strength is less than about 300 kV/cm, 30 kV/cm, 10 kV/cm or 5 kV/cm. In some embodiments, the field strength is from about 0.5 kV/cm to 10 kV/cm, or from about 1 kV/cm to 5 kV/cm.

Surprisingly, it has been found that it is possible to use relatively low field strength to improve the organoleptic properties of the tobacco. Using a pulsed electric field with low field strength may advantageously mean that the treated tobacco is not substantially damaged by the process (e.g. no disintegration).

The pulsed electric field applied to the tobacco composition has a pulse frequency of greater than or equal to about 20 Hz. In some embodiments, the frequency is greater than or equal to about 100 Hz, 250 Hz or 400 Hz. In some embodiments, the frequency is less than about 1,000 Hz, 750 Hz or 600 Hz. In some embodiments, the frequency is from about 250 Hz to 750 Hz, or 400 Hz to 600 Hz.

The pulsed electric field applied to the tobacco composition may have any suitable pulse width. “Pulse width” refers to the duration of each pulse. In some embodiments, the pulse width is greater than or equal to about 10 ns, 50 ns, 100 ns, 1 ps (1 x 10 ³ ns) or 1 ms (1 x 10 ⁶ ns). In some embodiments, the pulse width is less than about 500 ms (5 x 10 ⁸ ns), 1 ms (1 x 10 ⁶ ns), 1 ps (1 x 10 ³ ns), 300 ns, 200 ns, or 150 ns. In some embodiments, the pulse width is from about 10 to 300 ns, or 50 to 200 ns, or around 100 ns. The pulses of the pulsed electric field may have a “pulse shape”, referring to the profile of the energy supplied during a pulse. For example, a “rounded” pulse shape means that the energy supplied in a pulse rises and falls relatively slowly. In contrast, a “square” pulse shape has a fast turn-on and turn-off time. In preferred embodiments the pulses of the pulsed electric field have a square pulse shape.

The pulsed electric field may be applied to the tobacco composition for any duration suitable for improving the organoleptic properties of the tobacco. For example, the pulsed electric field may be applied to the tobacco composition for a duration of greater than or equal to about 10 minutes, 15 minutes, 30 minutes, 45 minutes, 60 minutes, 120 minutes, 180 minutes, or 240 minutes. In some examples, the pulsed electric field may be applied to the tobacco composition for a duration of less than about 600 minutes, 300 minutes, 180 minutes, 120 minutes, 60 minutes or 30 minutes. In some examples, the pulsed electric field may be applied to the tobacco composition for a duration of from about 10 to 600 minutes, or 30 to 300 minutes, or 60 to 180 minutes.

The pulsed electric field treatment may be carried out at any suitable temperature. For example, the pulsed electric field may be carried out a temperature of from about 0 °C to 60 °C, or from 10 °C to 50 °C, or 15 °C to 40 °C. In preferred embodiments, the pulsed electric field treatment is carried out at room temperature. In particular, the entire method may be carried out at room temperature. Thus, the present disclosure provides for the first time a method of improving the organoleptic properties of a tobacco at relatively low temperature. In some embodiments, the treated tobacco composition has a moisture content of less than about 30wt%, 15wt%, or 20wt%. In some embodiments, the treated tobacco composition has a moisture content of from about 5 to 40wt%, for example from about 10 to 30wt%, 10 to 20wt%, or 13 to 17wt%. In some embodiments, the treated tobacco composition has a moisture content of at least about 5wt%, 10wt%, or 13wt%. The method further comprises combining the treated tobacco with aerosol-generating agent to provide an aerosol-generating component. As used herein, an “aerosol generating agent” is an agent that promotes the generation of an aerosol on heating. An aerosol-generating agent may promote the generation of an aerosol by promoting an initial vaporisation and/or the condensation of a gas to an inhalable solid and/or liquid aerosol.

As used herein, the term “aerosol-generating component” simply refers to all of the materials provided in an aerosol-generating article which contribute to the aerosol when the aerosol-generating article is heated. Thus, the aerosol-generating component comprises the treated tobacco composition and the aerosol-generating agent. The term does not necessarily indicate that each of the constituents of the aerosol-generating component is located in the same part of the aerosol-generating article. As discussed hereinbelow, the aerosol-generating component may comprise constituents which are provided in an intimate mixture in the same portion of the aerosol-generating article, or alternatively may comprise constituents which are provided in separate chambers of the aerosol-generating article, and so on.

In general, suitable aerosol-generating agents include, but are not limited to: a polyol such as sorbitol, glycerol, and glycols like propylene glycol or triethylene glycol; a non polyol such as monohydric alcohols, high boiling point hydrocarbons, acids such as lactic acid, glycerol derivatives, esters such as diacetin, triacetin, triethylene glycol diacetate, triethyl citrate or myristates including ethyl myristate and isopropyl myristate and aliphatic carboxylic acid esters such as methyl stearate, dimethyl dodecanedioate and dimethyl tetradecanedioate. In some cases, the aerosol generating agent comprises one or more of glycerol, propylene glycol, triacetin and isopropyl myristate, suitably glycerol and/or propylene glycol.

For embodiments wherein the aerosol-generating article is to be used in a hybrid device, the weight ratio of aerosol generating agent to tobacco (dry weight) may be from about 10:1 to about 1:10, suitably from about 5:1 to about 1:5, suitably from about 2:1 to about 1:3, suitably from 3:2 to about 1:2, suitably about 1:1.

For embodiments wherein the aerosol-generating article is to be used in a tobacco heating product, the treated tobacco composition may be combined with aerosol generating agent to provide an aerosol-generating component comprising from about 5 to 30% aerosol-generating agent by weight of the aerosol-generating component (dry weight), preferably from about 10 to 20%. The method according to the invention may additionally comprise an initial step of adding water to the tobacco. The amount of water added may be from about 2% to about 20% based on the dry weight of tobacco, suitably from about 2%, 5% or 8% to about 12%, 15%, 18% or 20%. This pre-treatment with water may increase the transfer of polar tobacco components (such as flavours) from the tobacco to the aerosol inhaled by a user.

The aerosol-generating agent content of the present aerosol-generating articles may be such that they are particularly suitable for use in aerosol-generating apparatuses which heat, but do not burn the aerosol-generating article, and said articles might not be suitable for use in convention combustible smoking articles.

The method comprises combining the treated tobacco composition with the aerosol generating agent. In one embodiment, combining the treated tobacco with the aerosol generating agent comprises mixing the aerosol-generating agent with the treated tobacco. The aerosol-generating component provided by this embodiment may be particularly suitable for use in a tobacco heating product. The aerosol-generating component provided by this embodiment may conveniently be referred to as “smokable material”. The aerosol-generating agent may be solid or liquid when mixed with the treated tobacco composition. Where the aerosol-generating agent is solid, combining the treated tobacco composition with the aerosol-generating agent may comprise mixing the treated tobacco composition and aerosol-generating agent to provide an intimate mixture. Where the aerosol-generating agent is liquid, combining the treated tobacco composition with the aerosol-generating agent may comprise mixing the treated tobacco composition and aerosol-generating agent to provide a mixture wherein the treated tobacco composition is evenly distributed throughout the aerosol-generating agent or, put another way, the aerosol-generating agent is evenly distributed across the treated tobacco composition. In this embodiment which is particularly suitable for use in a tobacco heating product, the aerosol-generating component may have any suitable moisture content. For example, the aerosol-generating component may have a moisture content of less than about 20wt%, 18wt% or 15wt%. The aerosol-generating component may have a moisture content of from about 1 to 20wt%, for example about 3 to 18wt% or 5 to 15wt%. The aerosol-generating component may have a moisture content of at least about lwt%, 3wt% or 5wt%.

The method also comprises forming the aerosol-generating article to include the aerosol-generating component. In this embodiment which is particularly suitable for use in a tobacco heating product, the method may comprise processing the aerosol generating component to have a product shape. For example, the method may further comprise processing the mixture to provide a cylindrical rod of aerosol-generating component, and/or providing the aerosol-generating component in a paper wrapper with an optional filter to provide the aerosol-generating article.

The step of combining the treated tobacco composition with the aerosol-generating agent to provide an aerosol-generating component, and the step of forming the aerosol generating article to include the aerosol-generating component, may be carried out simultaneously. For example in another embodiment, the combining and forming steps comprise providing the aerosol-generating agent in a first chamber of a housing and providing the treated tobacco in a second chamber of the housing, wherein the first and second chambers are in fluid communication. The aerosol-generating article provided by this embodiment may be suitable for use in an electronic tobacco hybrid device.

According to another aspect of the present invention, there is provided an aerosol- generating article obtainable from the method disclosed hereinabove.

According to a further aspect of the present invention, there is provided an aerosol generating article for use in an aerosol-generating assembly, wherein the aerosol generating article contains an aerosol-generating component, and the aerosol- generating component comprises a treated tobacco composition and aerosol-generating agent.

The treated tobacco composition comprises tobacco to which a pulsed electric field has been applied. For example, the treated tobacco composition may correspond to the treated tobacco composition provided by the step of applying a pulsed electric field to a tobacco composition as described hereinabove. The treated tobacco composition of the present aerosol-generating article has been treated with a pulsed electric field having a field strength of greater than or equal to lOOV/cm and a pulse frequency of greater than or equal to 20Hz. In some embodiments, the pulsed electric field has any of the characteristics described hereinabove.

The aerosol-generating agent is present in the aerosol-generating component in an amount of greater than or equal to 8% by weight of the aerosol-generating component. The aerosol-generating agent may correspond to any of the aerosol-generating agents described hereinabove.

The aerosol-generating article of the present invention preferably contains nicotine. In some embodiments, the aerosol-generating article has a nicotine content of from 0.5 to 2% by weight. In some examples, the aerosol-generating aerosol has a nicotine content of at least about 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, or 1.8%. In some examples, the aerosol-generating aerosol has a nicotine content less than about 2%, 1.9%, 1.8%, 1.7%, 1.6%, 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.8%, or 0.6%.

In one embodiment, the aerosol-generating article contains the treated tobacco and aerosol-generating agent as mixture. The treated tobacco composition and aerosol generating agent may be distributed evenly throughout the mixture. The aerosol generating article may have a product shape, such as a cylindrical rod. The aerosol generating articles of this embodiment may be particularly suitable for use with tobacco heating products; further properties of these aerosol-generating articles are discussed in detail with reference to tobacco heating products below.

In another embodiment, the aerosol-generating article comprises a first chamber containing the treated tobacco composition and a second chamber containing the aerosol-generating agent. The chambers are configured to be in fluid communication, so that heated aerosol-generating agent may pass through the chamber containing the treated tobacco composition. In some embodiments, the first chamber is configured to be downstream of the second chamber in use in the aerosol-generating assembly, so that the heated aerosol-generating agent passes through the chamber containing the treated tobacco composition as it progresses towards the mouth end of the aerosol generating assembly. In some embodiments, the aerosol-generating article contains the aerosol-generating agent as a liquid. In general, this means that at room temperature the aerosol-generating agent is in liquid form.

According to another aspect of the present invention, there is provided an aerosol generating assembly. The aerosol-generating assembly comprises a treated tobacco composition and an aerosol-generating agent, both as described hereinabove.

The aerosol-generating assembly further comprises a heat source disposed to heat, but not bum, the tobacco component and/or the aerosol-generating agent, In some embodiments, the heat source of the aerosol-generating assembly wherein the heat source comprises an electrically resistive heating element, an infrared heating element, a photonic source, an inductive heating element, or a combination thereof. The heat source may be arranged to heat the tobacco, or to heat the aerosol-generating agent, or to heat both.

Particular embodiments of the aerosol-generating assembly are described below.

In one embodiment, the aerosol-generating assembly is configured to generate aerosol by heating, but not burning, the tobacco composition. Such apparatus is sometimes described as a “heat-not-bum” apparatus or a “tobacco heating product” or “tobacco heating device” or similar. The apparatus is typically generally elongate, having an open end, sometimes referred to as the mouth end. The smokable material comprises both the treated tobacco and the aerosol-generating agent as a mixture, and may be in the form of or provided as part of a cartridge or cassette or rod which can be inserted into the apparatus. A filter arrangement may be provided at the mouth end of the article to filter and/or cool volatilised material as the material is drawn by the user. A heater for heating and volatilising the smokable material may be provided as a “permanent” part of the apparatus or may be provided as part of the aerosol-generating assembly or consumable which is discarded and replaced after use. In use, particularly in the present principal applications, the smokable material is not burnt or combusted.

Referring now to Figure 1, there is shown schematically an example of an aerosol generating article 100 for use with an apparatus for heating smokable material. The aerosol-generating article 100 has a mouthpiece 101 and a cylindrical rod of smokable material 102. The smokable material 102 comprises the treated tobacco and aerosol generating agent described hereinabove.

The mouthpiece 101 may be formed of for example paper, for example in the form of a spirally wound paper tube, cellulose acetate, cardboard, crimped paper, such as crimped heat resistant paper or crimped parchment paper, and polymeric materials, such as low-density polyethylene (LDPE), or some other suitable material. The mouthpiece 101 may comprise a tube. The tube may be a hollow tube. Such a hollow tube may provide a filtering function to filter volatilised smokable material. As shown, the mouthpiece 101 may be elongate, in order to be spaced from the very hot part(s) of the main apparatus that heats the smokable material.

In an embodiment not shown, the mouthpiece may contain a filter element. The filter element may be a filter plug, and may be made, for example, from cellulose acetate. The filter element, if present, may be located at the downstream end of the mouthpiece.

Referring now to Figure 2, the mouthpiece assembly 201 may include a cooling element 204. The element 204 may be a monolithic rod having first and second ends and comprising plural through holes extending between the first and second ends. As shown in Figure 2, on the other side of the cooling element 204 may be a second hollow tube 206 which spaces the cooling element 204 from the very hot part(s) of the main apparatus that heats the smokable material and thus protects the cooling element 204 from high temperatures, as well as helping to improve aerosol production as it can help to prevent condensation. The second tube 206 may again be formed of for example paper, for example in the form of a spirally wound paper tube, cellulose acetate, cardboard, crimped paper, such as crimped heat resistant paper or crimped parchment paper, and polymeric materials, such as low-density polyethylene (FDPE), or some other suitable material. The mouth end tube 205 and the second tube 206 provide support for the cooling element 204. The mouth end tube 205 may have a filtering function and may sometimes be referred to as a tube filter.

The cooling element 204 in this example is located generally centrally of the mouthpiece assembly 201, but in other examples may be located more or less towards one end or the other of the mouthpiece assembly 201. In the example of Figure 2, the mouth end tube 205, the cooling element 204 and the second tube 206 are held together by a tipping paper 203 which is wrapped tightly round the mouth end tube 205, the cooling element 204 and the second tube 206 to bind them together. In this sense, the mouthpiece assembly 201 is “pre-assembled”.

In one specific example, the first, mouth end tube 205 may be 11 mm long, the cooling element 204 may be 19 mm long, and the second tube 206 may be 11 mm long, and the outside diameter of the mouthpiece assembly 201 as a whole may be 5.4 mm. Excluding the tipping paper 203, the outside diameter of the cooling element 204, the mouth end tube 205 and the second tube 206 may for example be in the range 5.13 mm to 5.25 mm, with 5.25 mm being one preferred option. Other dimensions may be used, depending on for example the particular application, the typical temperature of the incoming aerosol or vapour, the nature (material) of the aerosol or vapour and smokable material, etc.

As also shown in Figure 2, the mouthpiece assembly 201 may then be joined to the smokable material 202 by a further tipping paper 207, which is wrapped round the mouthpiece assembly 201 and at least the adjacent end of the smokable material 202. In other examples, the mouthpiece assembly 201 is not pre-assembled and instead the aerosol-generating article 200 is formed by wrapping a tipping paper 207 around the cooling element 204, the mouth end tube 205, the second tube 206 and the smokable material 202 effectively in one operation, with no separate tipping paper being provided for the components of the mouthpiece parts.

As shown in Figure 2, the mouthpiece assembly 201 may include a cooling element. The cooling element has through holes, which may extend substantially parallel to the central longitudinal axis of the rod.

The through holes may be arranged generally radially of the element when viewed in lateral cross-section. That is, in an example, the element has internal walls which define the through holes and which have two main configurations, namely radial walls and central walls. The radial walls extend along radii of the cross-section of the element and the central walls are centred on the centre of the cross-section of the element. The central walls in one example are circular, though other regular or irregular cross- sectional shapes may be used. Likewise, the cross-section of the element in one example is circular, though other regular or irregular cross-sectional shapes may be used.

In an embodiment, the majority of the through holes have a hexagonal or generally hexagonal cross-sectional shape. In this embodiment, the element has what might be termed a “honeycomb” structure when viewed from one end. The element may be substantially incompressible. It may be formed of a ceramic material, or of a polymer, for example a thermoplastic polymer, which may be an extrudable plastics material.

In an embodiment, the porosity of the element is in the range 60% to 75%. The porosity in this sense may be a measure of the percentage of the lateral cross-sectional area of the element occupied by the through holes. In an embodiment, the porosity of the element is around 69% to 70%.

In one embodiment, the aerosol-generating assembly is configured to generate aerosol by heating a liquid to produce an inhalable vapour or aerosol. Such apparatus is referred to as e-cigarette / heat-not-bum hybrid devices, also known as electronic tobacco hybrid devices.

In accordance with some embodiments described herein, the apparatus comprises: a first chamber for holding a liquid; a heater for volatilising liquid held in the first chamber; a second chamber containing the treated tobacco composition described herein; and an outlet; the arrangement being such that in use an inhalable medium passes out of the outlet, the medium comprising one or more constituents of the tobacco composition and volatilised liquid in the form of at least one of a vapour and an aerosol. In some cases, the apparatus comprises means for heating the tobacco composition to volatilise components of the tobacco and form a first aerosol and/or vapour. The liquid may be volatilised to form a second vapour and/or aerosol, which may be combined with the first vapour and/or aerosol to form the inhalable medium. In some cases, one heater may heat both the liquid and the tobacco composition. In some cases, the tobacco composition may additionally comprise an aerosol generating agent as described hereinabove. Alternatively, or additionally, aerosol-generating agent as described hereinabove may be provided in the liquid.

In other cases, there is provided apparatus for generating an inhalable medium, the apparatus comprising: a first chamber for holding a liquid; a heater for volatilising liquid held in the first chamber; a second chamber containing the treated tobacco composition described herein; and an outlet; the arrangement being such that in use liquid volatilised by the heater passes, in the form of at least one of a vapour and an aerosol, through the tobacco composition to thereby entrain one or more constituents from the tobacco composition to produce the inhalable medium which passes out of the outlet.

These hybrid devices provide an inhalable medium which has, for example, a flavour or flavours that are derived from the tobacco composition contained in the apparatus in use. In a particular application, the vapour or aerosol passing over the tobacco composition is hot and so heats the material to evaporate or volatilise one or more constituents from the tobacco composition, allowing the constituents to be taken up into the inhalable medium. In an embodiment, the heater for volatilising liquid contained in the first chamber is arranged to vaporise the liquid. In an embodiment, the apparatus comprises a cooler or cooling zone downstream of the heater and upstream of the chamber, the cooler or cooling zone being arranged to cool vaporised liquid to form an aerosol of liquid droplets which in use passes through the tobacco composition in the chamber. The cooler may be arranged in effect to act as a heat exchanger, allowing for recovery of heat from the vapour. The recovered heat can be used for example to pre-heat the tobacco composition and/or to assist in heating the liquid.

In another embodiment, the heater for heating liquid contained in the first chamber is arranged to heat the liquid to form an aerosol.

In an embodiment, the apparatus comprises a second heater for heating the tobacco composition in the chamber. This enables the tobacco composition to be heated by the heater, which encourages release of compounds from the tobacco composition, and optionally allows a lower temperature to be used for the heated liquid.

In an embodiment, the apparatus is battery-operated.

In an embodiment, the or each heater is an electrically resistive heater. In an embodiment, the first chamber for holding liquid is removable. The first chamber may be in the form of a pot or the like (which in some embodiments may be annular for example), and/or an absorbent wadding or the like. The whole first chamber containing the liquid may in effect be a disposable item which is replaced as a whole after use. As an alternative, the arrangement may be such that the user removes the first chamber from the apparatus, replaces used liquid or tops up liquid in the first chamber, and then places the first chamber back in the apparatus. In some cases, the first chamber may be non-removable from the apparatus. In such an embodiment, the user may just replace used liquid or top up liquid in the first chamber after use as necessary.

In some cases, the first chamber for holding liquid and the second chamber for containing the treated tobacco composition are an integral unit.

In some cases, the first chamber holds liquid, the liquid containing nicotine.

In some cases, the first chamber holds liquid, the liquid containing one or more flavourings.

In some cases, the first chamber holds liquid, the liquid containing one or more aerosol generating agents. In this context, an “aerosol generating agent” is an agent that promotes the generation of an aerosol. An aerosol generating agent may promote the generation of an aerosol by promoting an initial vaporisation and/or the condensation of a gas to an inhalable solid and/or liquid aerosol. In some embodiments, an aerosol generating agent may improve the delivery of flavour from the aerosol generating material.

In general, any suitable aerosol generating agent or agents may be included in the aerosol generating material of the invention. Suitable aerosol generating agents include those described hereinabove.

In some cases, the second chamber is removable from the apparatus. The second chamber may be, for example, in the form of a cartridge or the like which contains the tobacco composition before use. The whole second chamber containing the tobacco composition may in effect be a disposable item which is replaced as a whole after use. As an alternative, the arrangement may be such that the user removes the second chamber from the apparatus, replaces used material in the second chamber, and then places the second chamber back in the apparatus.

In accordance with some embodiments described herein, there is provided a cartridge for use in a device for heating tobacco material, the cartridge containing the tobacco composition described herein. Suitably, the cartridge may be adapted for use in the apparatus for generating an inhalable medium described herein, suitably a non combustible smoking article, the cartridge comprising the chamber containing the tobacco composition.

In some cases, the cartridge further comprises the first chamber for holding a liquid, and liquid.

The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.