WO2023073098A1

WO2023073098A1 - Pod including temperature-switchable material for an aerosol-generating device, and aerosol-generating device comprising the same

Info

Publication number: WO2023073098A1
Application number: PCT/EP2022/080073
Authority: WO
Inventors: Jaakko MCEVOY; Christoph Lungenschmied
Original assignee: Jt International S.A.
Priority date: 2021-10-29
Filing date: 2022-10-27
Publication date: 2023-05-04
Also published as: EP4422435A1

Abstract

The present invention relates to a pod including a temperature- switchable material for an aerosol -generating device in which leakage of an aerosol -generating liquid material (e-liquid) during transit and storage is prevented. This is achieved by a pod comprising a porous wick and a reservoir including a discharge opening for an aerosol- generating liquid material, wherein ( i ) the porous wick is coated with a temperature-switchable material on a surface of the porous wick sealing the discharge opening o f the reservoir so that the temperature-switchable material is arranged between the discharge opening of the reservoir and the porous wick; or ( ii ) the porous wick is coated with a temperature- switchable material on a surface of the porous wick opposite of the surface of the porous wick sealing the discharge opening so that the porous wick is arranged between the temperature-switchable material and the reservoir; or ( ill ) the porous wick is made of the temperature- switchable material and is arranged so that a surface of the porous wick seals the discharge opening of the reservoir, wherein the temperature-switchable material is an amphiphilic material being impermeable for an aerosol-generating liquid material below a transition temperature of between 25 ° C and 300 ° C and becoming permeable for an aero sol -generating liquid material when being exposed to a temperature above said transition temperature. Furthermore, the present invention also relates to an an aerosol-generating device comprising the pod.

Description

POD INCLUDING TEMPERATURE -SWITCHABLE MATERIAL FOR AN AEROSOLGENERATING DEVICE , AND AEROSOL-GENERATING DEVICE COMPRISING THE SAME

Technical field

The present invention relates to a pod including a temperature-switchable material for an aerosol-generating device , in particular an electronic cigarette , vapori zer or e-vapor pod system, and an aerosol-generating device comprising said pod .

Technical background

Aerosol-generating devices , such as electronic cigarettes or "e-cigarettes" as they are also known, have gained in popularity over the past ten years as an alternative to traditional smoking articles , like cigarettes , cigars , and cigarillos . Developments in the design and configuration of such aerosol generating devices or vapori zer devices are ongoing to improve their performance and their reliability, as well as their ease of production and their production costs .

Conventional aerosol generating devices usually include an atomi zer such as a heater, a power supply ( e . g . an electrical power source ) and a pod comprising a wick and a liquid reservoir that contains flavoured e-liquid . The e-liquid can be volati zed using the heater and trans ferred to a user of the aerosol generating device in an airflow, which is preferably guided through a mouthpiece of the device .

In order to provide a convenient way for a user to load the e-liquid into the aerosol generating device and to avoid the need for the user to handle the e-liquid directly, thereby reducing the likelihood of spillage and waste , pods are conventionally provided . The flow of e-liquid through the wicking material in e- cigarettes must be suf ficient to avoid dry puf fs . However , permeation of the e-liquid through the wicking material o f the pod will contribute to undesired leakage of the e-liquid as it does not evaporate when the e-cigarette is not in use , in particular during storage and transit .

WO 2015/ 070405 Al relates to an atomi zer for an electronic cigarette comprising an oil-storage mechanism and an atomi zing component . A cigarette oil flowing channel is used for supplying cigarette oil stored within the oil-storage mechanism to the atomi zing component . A hot-melt sealing structure is used for sealing the cigarette oil flowing channel before using the atomi zer for the first time . When using the electronic cigarette for the first time and powering on the atomi zing component for the first time , the hot-melt sealing structure is heated and melted to open the cigarette oil flowing channel , thus allowing the cigarette oil to be supplied to the atomi zing component . However, according to WO 2015/ 070405 Al , leakage can only be prevented before the electronic cigarette is used for the first time . Once the hot-melt sealing structure is melted, it cannot reseal the cigarette oil flowing channel and leakage can occur during long periods of not using the electronic cigarette .

WO 2020/ 070109 Al concerns a liquid supply system such as a cartridge (pod) for use with aerosol-generating devices , which includes a liquid substrate in a retention material , a liquid flow channel extending from the liquid retention material and a barrier layer disposed in the liquid flow channel . The barrier layer that i s included in the cartridge prevents premature trans fer of the liquid substrate into the airflow passage . The barrier has a degradation temperature between 60 ° C and 130 ° C at which it degrades and allows trans fer of the liquid substrate into the liquid flow channel . However, according to WO 2020/ 070109 Al , leakage can only be prevented before the aerosol-generating device is used for the first time . Once the barrier layer is degraded, it cannot reseal the liquid flow channel and leakage can occur during long periods of n( )t using the aerosol-generating device .

Summary of the Invention

In view of the above , it is an obj ect of the invention to provide a pod for an aerosol-generating device , which can prevent leakage of an aerosol-generating liquid material ( e- liquid) during transit and storage before the aerosolgenerating device is used for the first time and also afterwards , during long periods of not using the aerosolgenerating device .

This aim is achieved by a pod for an aerosol-generating device as defined in claim 1 and an aerosol-generating device as defined in claim 14 . Preferable embodiments of the invention are defined in the dependent claims , the following description and the accompanying drawings .

A core idea of the present invention lies in a pod for an aerosol-generating device , which allows for the flow of the e-liquid to be selectively switched on so that the e-liquid can be supplied to the heating element when the pod is in use . This is achieved by including a temperature-switchable material in the pod, which coats or forms a porous wick and is arranged so that a discharge opening of a reservoir including the e-liquid is sealed . Below its transition temperature and before being heated, the temperature- switchable material is impermeable for the e-liquid, thus preventing leakage of the e-liquid during storage or transit in non-use periods . When in use , the temperature-switchable material is heated up to its transition temperature at which it becomes permeable for the e-liquid, which can then be supplied to the heating element and vapori zed . During subsequent long periods of storage or transportation below the transition temperature of the temperature-switchable material , the temperature-switchable material again becomes impermeable to the e-liquid, thus preventing leakage .

Brief Description of the Drawings

Figure 1 is a schematic illustration of an aerosol-generating device in accordance with one embodiment according to option ( i ) of the present invention .

Figure 2 is a schematic illustration of a pod for an aerosolgenerating device in accordance with another embodiment according to option ( i ) of the present invention .

Figure 3 is a schematic illustration of a pod for an aerosolgenerating device in accordance with another embodiment according to option ( i ) of the present invention .

Figure 4 is a schematic illustration of a section of a pod for an aerosol-generating device in accordance with another embodiment according to option ( i ) of the present invention during a non-use period .

Figure 5 is a schematic illustration of the section of the pod for an aerosol-generating device shown in Figure 4 during use .

Figure 6 illustrates a temperature-switchable material comprising a vapor channel structure .

Figure 7 is a schematic illustration of a section of a pod for an aerosol-generating device in accordance with one embodiment according to option ( ii ) of the present invention during a non-use period . Figure 8 is a schematic illustration of a section of a pod for an aerosol-generating device in accordance with another embodiment according to option ( ii ) of the present invention during a non-use period .

Figure 9 is a schematic illustration of a section of a pod for an aerosol-generating device in accordance with one embodiment according to option ( iii ) of the present invention during a non-use period .

Figure 10 is a schematic illustration of the section of the pod for an aerosol-generating device shown in Figure 9 during use .

Detailed Description

The term "aerosol-generating liquid material" is interchangeably used with the term "e-liquid" and refers to the liquid material from which the aerosol is created in an aerosol-generating device using for example a vapori zer, an atomi zer, a nebuli zer or a heating element .

The term "aerosol-generating device" refers to a device that can generate an aerosol for inhalation, such as an electronic cigarette , a vapori zing device , a nebuli zing device , an e- vapor pod system or an inhalation device .

The term "temperature-switchable material" refers to an amphiphilic material having a transition temperature of between 25 ° C and 300 ° C, preferably between 50 ° C and 100 ° C, which is superhydrophobic and impermeable for an aerosol-generating liquid material below the transition temperature and which becomes superhydrophilic and permeable for an aerosol-generating liquid material when being exposed to a temperature above said transition temperature . Thi s instantaneous liquid permeation switching ( temperature- induced wettability change ) is valuable in e-vapor pod systems where the porous media is desired to be in an OFF state when in storage/ transit but needs to rapidly switch to an operational ON state when in use, i.e. heated. This helps reducing leakage risks during storage and transport.

The term "superhydrophobic" refers to materials exhibiting a large water contact angle of at least 150° and the term "superhydrophilic" refers to materials exhibiting a small water contact angle of less than about 10°.

The term "porous wick" refers to a wicking material having a porosity of 30% to 60% and preferably 40% to 50%, wherein the porosity is a fraction of the volume of voids over the total volume of the wicking material. The porosity can be measured by microscope image analysis. Optionally, the porous wick comprises a vapor channel structure.

The term "sol-gel foam" refers to a silicon alkoxide material having a porous microstructure obtained from a sol-gel process as described in Shirtcliffe et al. "Porous materials show superhydrophobic to superhydrophilic switching", Chemical Communications, 2005, 3135-3137.

The present invention relates to a pod (1) for an aerosolgenerating device (10) , which comprises a porous wick (2) and a reservoir (3) . The reservoir (3) includes a discharge opening (4) , through which an aerosol-generating liquid material (e-liquid) can be discharged when using the aerosolgenerating device (10) .

According to option (i) of the invention, the porous wick (2) is coated with a temperature-switchable material (6) on that surface of the porous wick (2) that seals the discharge opening (4) of the reservoir (3) . In option (i) , the temperature-switchable material (6) is arranged between the discharge opening (4) of the reservoir (3) and the porous wick (2) and forms a superhydrophobic barrier preventing the e-liquid to permeate into the porous wick (2) when the pod (1) is not used, i.e. during storage and transportation, thus avoiding leakage. When in use, the properties of the temperature-switchable material (6) are switched so that it becomes superhydrophilic and the e-liquid can permeate into the porous wick (2) and be subsequently vaporized.

According to option (ii) of the invention, the porous wick (2) is coated with a temperature-switchable material (6) on that surface of the porous wick (2) that is arranged opposite to the surface of the porous wick sealing the discharge opening (4) of the reservoir (3) . In option (ii) , the discharge opening (4) is directly sealed by the porous wick (2) , which is thus arranged between the temperature- switchable material (6) and the reservoir (3) . The porous wick (2) is however coated on its remaining surface, that does not seal the discharge opening (4) of the reservoir with the temperature-switchable material (6) so that the e-liquid can permeate into the porous wick (2) during periods of not using the pod (1) , but cannot leak out of the pod (1) due to the hydrophobic barrier layer provided by the temperature- switchable material (6) coating on the porous wick (2) . During use, the properties of the temperature-switchable material (6) are switched to superhydrophilic so that layer becomes permeable for the e-liquid which can subsequently be vaporized.

According to option (iii) of the invention, the porous wick (2) is made of the temperature-switchable material (6) and is arranged so that a surface of the porous wick (2) seals the discharge opening (4) of the reservoir (3) . During periods of not using the pod (1) , the porous wick (2) forms a superhydrophobic barrier and remains impermeable to the e- liquid, thus preventing leakage. When in use, the porous wick (2) that is fully made of the temperature-switchable material (6) is switched to become superhydrophilic and the e-liquid can permeate into the wick and be subsequently vaporized. The temperature-switchable material ( 6 ) used in the present invention is an amphiphilic material , which is impermeable for an aerosol-generating liquid material below a transition temperature of between 25 ° C and 300 ° C and which becomes permeable for an aerosol-generating liquid material when being exposed to a temperature above said transition temperature . The present invention makes uses of a switching mechanism based on temperature . That is , when heating the temperature-switchable material ( 6 ) up to its transition temperature its wettability characteristics change . In particular, when heating the temperature-switchable material ( 6 ) up to its transition temperature for the first time , its superhydrophobic properties are switched instantaneously to become superhydrophilic . These superhydrophilic properties of the temperature-switchable material ( 6 ) are switched back to become superhydrophobic and impermeable for the e-liquid when the pod ( 1 ) is not in use , such as during storage or transit at a temperature below the transition temperature .

The transition temperature of the temperature-switchable material ( 6 ) is between 25 ° C and 300 ° C, preferably between 50 ° C and 100 ° C, as such a transition temperature allows the switching to be triggered by the heating of the e-liquid for evaporation .

The temperature-switchable material ( 6 ) is a porous material with pores having a pore diameter preferably in the range of between 5 pm and 50 pm, more preferably between 10 pm and 40 pm and even more preferably between 15 pm and 30 pm . While the above-described switching, i . e . the transition from superhydrophobic and impermeable for the e-liquid to superhydrophilic and permeable for the e-liquid, can also be obtained in non-porous films , the switching in non-porous films is a more gradual transition . In contrast thereto , porous materials enable a (near ) -instantaneous switching . This fast switching ability of porous materials has been ascribed to the fact that a liquid can either enter the pores or not and no transition state is possible. Therefore, when applying a porous film with temperature-switchable wettability characteristics onto a porous wick structure, switchable liquid flow into and/or out of the wick is advantageously enabled by a rapid superhydrophobic to superhydrophilic switching. The temperature-switchable material (6) can therefore reduce leakage of e-liquid until it is heated above its transition temperature. It is especially advantageous to employ porous materials showing temperature-induced wettability switching as the transition is fast and distinct. The temperature-switchable material (6) can be entirely made of one material or can be a composite material of different materials.

The temperature-switchable material (6) is preferably a porous material made from silicon alkoxide. The silicon alkoxide may contain at least one of phenyltriethoxysilane (PhTEOS) , methyltriethoxysilane (MTEOS) and tetraethylorthosilicate (TEOS) . By varying the ratio of PhTEOS, MTEOS and/or TEOS, the transition temperature of the temperature- switchable material (6) can be tuned. Specifically, when increasing the PhTEOS fraction in the temperature-switchable material (6) , the temperature at which the wettability switch occurs is increased. On the other hand, when increasing the TEOS fraction in the temperature-switchable material (6) , the transition temperature is decreased. Equally, when using MTEOS instead of PhTEOS in the temperature-switchable material (6) , the transition temperature is lowered, because the methyl group contained in MTEOS is less bulky than the phenyl group contained in PhTEOS. The ratio of PhTEOS or MTEOS and TEOS ( [PhTEOS or MTEOS ]/ [ TEOS ] ) in the temperature- switchable material (6) is preferably between 1:3 to 2:1. For example, when the temperature-switchable material (6) is made of PhTEOS and TEOS in a ratio of ( [ PhTEOS ]/ [ TEOS ] ) of 1:2, a transition temperature of about 275°C (±10°C) has been reported (Shirtcliffe et al., "Porous materials show superhydrophobic to superhydrophilic switching" , Chemical

Communications , 2005 , 3135-3137 ) .

The porous material made from silicon alkoxide is preferably a sol-gel foam, which can be prepared by the sol-gel preparation method described in Shirtcli f fe et al . "Porous materials show superhydrophobic to superhydrophilic switching" , Chemical Communications , 2005 , 3135-3137 .

When the temperature-switchable material ( 6 ) is a silicon alkoxide sol-gel foam, the switch in liquid permeation occurs due to the change from hydrophobic to hydrophilic with virtually no transition period . Without wishing to be bound by any theory, it is believed that a change in morphology of the inner pore surface occurs upon exposure of porous silicon alkoxide materials to higher temperatures as explained in the following . The hydrophobic to hydrophilic switch may occur due to the crosslinked silica backbone of the sol-gel foam causing redistribution of the organic groups contained in the sol-gel foam ( i . e . a methyl group or a phenyl group ) from the surface of the pores of the sol-gel foam into the bulk of the material when being heated to the respective transition temperature . Below the transition temperature , the organic groups cover the inside of the pores of the sol-gel foam, which causes the material to be hydrophobic at first . Higher temperatures may cause cleavage of the Si-O-Si-bonds thus forming Si-OH groups , which can subsequently lead to a rearrangement of the organic groups contained in the sol-gel structure , whereby the inside of the pores is rendered more polar and therefore hydrophilic . The wettability switch may therefore be explained by a migration of these organic groups away from the pore surfaces and into the bulk of the silicon alkoxide sol-gel material .

In the pod ( 1 ) according to option ( i ) of the present invention, the porous wick ( 2 ) may have a vapor channel structure ( 7 ) forming vapor channels ( 7a ) on a surface of the porous wick (2) that is arranged opposite to the surface sealing the discharge opening (4) as shown in Figure 3. This vapor channel structure (7) allows for airflow control and vaporization rate control because it increases the evaporation surface of the porous wick (2) . The direction of the vapor channels (7a) is not particularly limited. Preferably, the channels run parallel to the airflow. For example, as shown in Figure 3, the direction of the vapor channels (7a) is parallel to the direction of the air which is guided along a bottom surface (2b) of the porous wick (2) .

In the pod (1) according to option (ii) and option (iii) of the invention, the temperature-switchable material (6) may comprise a vapor channel structure (7) forming vapor channels (7a) in a surface of the porous wick (2) that is arranged opposite to the surface of the porous wick (2) sealing the discharge opening (4) . This vapor channel structure (7) allows for airflow control and vaporization rate control of the wick structure but does not interrupt the barrier function of the temperature-switchable material (6) when the pod (1) is not in use. Larger vapor channels increase the speed of the airflow and create a greater surface, which leads to an increase of the vaporization rate. That is, even when comprising such a vapor channel structure (7) , the temperature-switchable material (6) is arranged to cover the porous wick (2) sealing the discharge opening (4) of the reservoir (3) so as to prevent the e-liquid from leaking out. The direction of the vapor channels (7a) is not particularly limited. Preferably, the channels run parallel to the airflow .

The vapor channel structure (7) can have a geometrical structure selected from the group consisting of pin fins, rectangular channels, circular channels, re-entrant cavities and flow mixer structures. In addition to the vapor channel structure (7) , the pod (1) of option (ii)or option (iii) may comprise a heat transfer material layer (8) arranged adjacent to the vapor channel structure (7) for enhancing the heat supply to the temperature-switchable material (6) and reducing the time of the temperature-induced wettability change. Moreover, the pod (1) can further comprise a metal mesh (9) having a temperature-switchable coating, wherein the metal mesh (9) is arranged between the vapor channel structure (7) of the temperature-switchable material (6) and the heat transfer material layer (8) . Thus, the metal mesh (9) is provided in direct contact with the heat transfer material layer (8) . As a result, the time from when the heater is switched on to the temperature-induced wettability change is further reduced.

The metal mesh (9) can be made of Al, Cu, NiCr or stainless steel and is preferably made of stainless steel. The temperature-switchable coating of the metal mesh (9) can be made of the same material as described above for the temperature-switchable material (6) . The coated metal mesh (9) therefore has the same temperature switchable properties as described above for the temperature-switchable material (6) , i.e. from being superhydrophobic below the transition temperature of the coating material to becoming superhydrophilic above said transition temperature. Such a coated metal mesh structure (9) can be prepared as described in Yang et al. "Functional silica film on stainless steel mesh with tunable wettability", Surface & Coatings Technology, 2011, 205, 5387-5393.

The thickness of the temperature-switchable material (6) in a pod (1) according to option (i) and option (ii) of the invention, wherein the temperature-switchable material (6) is provided as a coating layer of the porous wick (2) , is preferably between 0.0001 mm and 1 mm, more preferably between 0.0005 mm and 0.25 mm, and even more preferably between 0.001 mm and 0.1 mm. The thickness of the temperature-switchable material (6) in a pod (1) according to option (iii) of the invention, wherein the porous wick (2) is made of the temperature-switchable material (6) , is preferably between 0.1 mm and 10 mm, more preferably between 0.25 mm and 7.5 mm, and even more preferably between 1 mm and 5 mm.

In the pod (1) according to option (ii) of the invention, the temperature-switchable material (6) can be sandwiched between two or more porous wicks (2) or can be located on that surface of the porous wick (2) that does not seal the discharge opening (4) of the reservoir (3) .

The porous wick (2) used in the pod (1) of option (i) and option (ii) of the invention can be made entirely from one material or can be a composite material of different porous wicks. The porous wick (2) can for example be made of ceramic, silica or cotton, wherein a ceramic wick is preferable from the viewpoint of providing excellent mechanical properties, particularly in terms of rigidity. Ceramic wicks are, for example, not influenced by compression like cotton wicks. Furthermore, ceramic is a stable, inert and cheap material, which is mass producible.

The pod (1) of the present invention can further comprise an airflow channel (5) . Air can enter the pod through an inlet (5a) of the airflow channel (5) , is guided through the porous wick (2) and/or along a surface of the porous wick (2) and exits the pod (1) through an outlet of the airflow channel (5) . The design and position of the airflow channel (5) is not particularly limited. It may, for instance, be centered in the pod and have a tubular shape, wherein the porous wick (2) , usually having a rod shape, is centered in the air flow channel (5) , thereby forming two separate open areas (12) between two opposite sidewall surfaces (2a) of the porous wick (2) and the wall of the air flow channel (5) , respectively. In this design, air may flow from the airflow inlet (5a) through the porous wick (2) and/or along a sidewall surface (2a) of the porous wick (2) facing the wall of the tubular airflow channel (5) to the airflow outlet (5b) , i.e. from the bottom to the top as shown in e.g. Figures 1 and 2. Alternatively, the airflow channel (5) may be designed such that air is guided through the porous wick (2) as shown in Figures 4, 5, 9 and 10, or along a bottom surface (2b) of the porous wick (2) as shown in Figure 3, or along a bottom surface (6a) of the temperature-switchable material (6) as shown in Figures 7 and 8. The air flows from the airflow inlet (5a) through the porous wick (2) , or along the bottom surface (2b) of the porous wick (2) , or along a bottom surface (6a) of the temperature-switchable material (6) to the airflow outlet (5b) .

When the pod (1) of the present invention is in use, the vaporized e-liquid is mixed with the air that is guided through the porous wick (2) or along a surface of the porous wick (2) and is simultaneously discharged with the air through the outlet (5b) of the airflow channel (5) . When the airflow channel (5) is configured so that air is guided along a surface of the porous wick (2) , a heat transfer material layer (8) can be arranged adjacent to the surface of the porous wick (2) along which the air is guided to enhance heat supply to the porous wick (2) and reduce the time of commissioning .

The aerosol-generating device (10) of the present invention comprises the pod (1) according to the invention and a heater unit (11) . When the aerosol-generating device (10) is used, the heater unit (11) distributes heat to the porous wick (2) and the temperature-switchable material (6) of the pod (1) , thus initiating the temperature-induced wettability change of the temperature-switchable material (6) . The heater unit (11) can be provided separately from the pod (1) in a heater-in- device configuration or can be provided integrally with the pod ( 1 ) .

Embodiments of the invention will now be explained in detail, by way of non-limiting example only, with reference to the accompanying figures.

Where technical features in the drawings, detailed description or any claim are followed by reference signs, the reference signs have been included for the sole purpose of increasing the intelligibility of the drawings, detailed description, and claims. Accordingly, neither the reference signs nor their absence have any limiting effect on the scope of any claim elements. The same reference signs listed in different figures refer to identical, corresponding or functionally similar elements.

Figure 1 shows an aerosol-generating device (10) according to one embodiment in accordance with option (i) of the invention. The aerosol-generating device (10) comprises a pod

(I) and a heater unit (11) . The pod (1) contains a porous wick (2) , which is preferably made of ceramic, a temperature- switchable material (6) and a reservoir (3) for an aerosolgenerating liquid material. The heater unit (11) can contain an energy source such as a battery, a heater, which is connected by electrical contacts to the battery, and a controller, which controls the energy supply to the heater and serves to switch the heater on and off and control the temperature of the heater. In the embodiment shown in Figure 1, the pod (1) further comprises an airflow channel (5) including an airflow inlet (5a) and an airflow outlet (5b) . In this embodiment, the temperature-switchable material (6) seals the discharge opening (4) of the reservoir (3) and thus prevents the e-liquid from leaking out during storage or transportation of the pod (1) . When in use, the heater unit

(II) distributes heat to the porous wick (2) and the temperature-switchable material (6) of the pod (1) . When the temperature-switchable material (6) is thus heated up to its transition temperature, it becomes permeable to the e-liquid that can then permeate into the porous wick (2) and be subsequently vaporized. During use, air entering the airflow channel (5) is guided through the porous wick (2) and/or along a surface of the porous wick (2) , is supplied with the vaporized e-liquid to form an e-vapor and exits the airflow channel (5) through the airflow outlet (5b) , from where the e-vapor can be inhaled.

Figure 2 shows a pod (1) according to another embodiment in accordance with option (i) of the invention. The pod (1) includes an e-liquid reservoir (3) and a porous wick (2) having a rod shape that is coated with a temperature- switchable material layer (6) on the surface sealing the discharge opening (4) of the reservoir (3) . In the embodiment shown in Figure 2, the porous wick (2) is preferably made of ceramic and the temperature-switchable material coating (6) is preferably made of a silicon alkoxide sol-gel foam. In this embodiment, the pod (1) further includes an airflow channel (5) and a heater track (13) that distributes heat to the porous wick (2) and the temperature-switchable material (6) during use so that the temperature switchable material layer (6) becomes permeable for the e-liquid that can then permeate into the ceramic wick (2) and be vaporized. The airflow channel (5) contains a chimney part having a tubular shape, in which the porous wick (2) is centered allowing for the formation of two separate open areas (12) between two opposite sidewall surfaces (2a) of the porous wick (2) and the wall of the tubular air flow channel (5) (shown in Figure 2, Top view) . When in use, air can enter the airflow inlet (5a) at ambient pressure, be guided through the porous wick (2) and/or along the two opposite sidewall surfaces (2a) of the porous wick (2) where it is supplied with the vaporized e-liquid to form an e-vapor, and exit the airflow outlet (5b) as e-vapor. Figure 3 shows a pod (1) according to another embodiment in accordance with option (i) of the invention. The pod (1) includes an e-liquid reservoir (3) and a porous wick (2) that is coated with a temperature-switchable layer (6) on the surface sealing a discharge opening (4) of the reservoir (3) . In this embodiment, the pod (1) includes an airflow channel (5) including an airflow inlet (5a) and an airflow outlet (5b) , whereby the air is guided along a bottom surface (2b) of the porous wick (2) . When in use, air can enter the airflow inlet (5a) at ambient pressure, be guided along the bottom surface (2b) of the porous wick (2) where it is supplied with the vaporized e-liquid to form an e-vapor, and exit the airflow outlet (5b) as e-vapor. In this embodiment, the porous wick (2) has a vapor channel structure (7) for achieving a preferable airflow and vaporization rate. The pod (1) further comprises a heat transfer material layer (8) arranged adjacent to the bottom surface (2b) of the porous wick (2) along which the air is guided. The heat transfer material layer (8) is in contact with a planar heating element (14) . Such a configuration enhances heat supply to the porous wick (2) and thereby reduces the time of commissioning .

Figure 4 shows a pod (1) according to another embodiment in accordance with option (i) of the invention during a non-use period. The surface of the porous wick (2) that seals the discharge opening (4) of the e-liquid reservoir (3) is coated with the temperature-switchable material (6) . When no heat is applied and the temperature-switchable material (6) is kept below its transition temperature, its superhydrophobic properties render the temperature-switchable material (6) impermeable to the e-liquid and the porous wick (2) stays dry. Thus, when the pod (1) is not in use, the temperature- switchable material (6) forms a barrier layer so that the e- liquid cannot permeate into the porous wick (2) and leakage is prevented. In this embodiment, air flows through the porous wick as indicated by the arrow showing the air flow. When the pod (1) according to the embodiment as previously described with regard to Figure 4 is used and heat is supplied as shown in Figure 5, the properties of the temperature-switchable material (6) switch to become superhydrophilic and the e-liquid can permeate through the temperature-switchable material layer (6) into the porous wick (2) for saturating the porous wick (2) and for being subsequently vaporized.

Figure 6 shows a temperature-switchable material (6) , which comprises a vapor channel structure (7) including vapor channels (7a) for controlling the airflow and the vaporization rate. The temperature-switchable material (6) can be formed of a silicon alkoxide sol-gel foam thus forming a porous wicking material. In the embodiment shown in Figure 6, the vapor channels (7a) of the vapor channel structure (7) have a rectangular shape.

Figure 7 shows a pod (1) according to one embodiment in accordance with option (ii) of the invention during a non-use period. The porous wick (2) is coated with the temperature- switchable material (6) on that surface that is arranged opposite to the surface of the porous wick (2) sealing the discharge opening (4) of the reservoir (3) . When not in use, the temperature-switchable material layer (6) forms an impermeable barrier for the e-liquid, which thus cannot leak out of the porous wick (2) that is saturated with the e- liquid. As shown in the embodiment of Figure 7, the temperature-switchable material layer (6) can be a thin coating of the silicon alkoxide porous sol-gel wick including a rectangular vapor channel structure (7) of Figure 6 for achieving a preferable airflow and vaporization rate. Furthermore, as shown in this embodiment, a heat transfer material layer (8) can be arranged adjacent to the vapor channel structure (7) of the heat-transfer material layer (6) for enhancing the heat transfer to the temperature-switchable material (6) and reducing the time of the temperature-induced wettability change of the temperature-switchable material (6) when using the pod (1) .

As shown in Figure 8, the pod (1) of Figure 7 can further comprise a metal mesh (9) having a temperature-switchable coating, which is arranged between the vapor channel structure (7) of the temperature-switchable material layer (6) and the heat transfer material layer (8) . The metal mesh (9) directly contacts the heat transfer material layer (8) so that the time from when the heater is switched on to the temperature-induced wettability change of the temperature- switchable material is further reduced. For this reason, it is also preferable that the metal mesh (9) is coated with a silicone alkoxide sol-gel.

Figure 9 shows a pod (1) according to one embodiment in accordance with option (iii) of the invention during a nonuse period. The porous wick (2) is fully made of the temperature switchable material (6) which forms the whole wicking material and seals the discharge opening (4) of the e-liquid reservoir (3) . When the pod (1) is not in use and stored at a temperature below the transition temperature, the temperature-switchable wick (6) is impermeable to the e- liquid and leakage is prevented. In this embodiment, air flows through the temperature-switchable wick (6) as indicated by the arrow showing the air flow.

When applying heat to the temperature-switchable wick (6) during use of the pod (1) of option (iii) as described with regard to Figure 9 and thus heating the temperature- switchable wick (6) up to or above its transition temperature as shown in Figure 10, the temperature-switchable wick (6) becomes permeable to the e-liquid, which can enter the porous wick structure and be subsequently vaporized.

Although detailed embodiments have been described, these only serve to provide a better understanding of the invention defined by the independent claims and are not to be seen as limiting .

It will also be appreciated that the terms "comprise", "comprising", "include", "including", "contain", "containing", "have", "having", and any variations thereof as used herein, are intended to be understood in an inclusive (i.e. non-exclusive ) sense, such that the product and device described herein is not limited to those features recited but may include other elements or features not expressly listed or inherent to such product or device. Furthermore, the terms "a" and "an" used herein are intended to be understood as meaning one or more unless explicitly stated otherwise.

REFERENCE LIST

1 Pod

2 Porous wick

2a Sidewall surface

2b Bottom surface

3 Reservoir

4 Discharge opening

5 Airflow channel

5a Inlet of airflow channel

5b Outlet of airflow channel

6 Temperature-switchable material

6a Bottom surface

7 Vapor channel structure

7a Vapor channel

8 Heat transfer material layer

9 Metal mesh

10 Aerosol-generating device

11 Heater unit

12 Open area

13 Heater track

14 Planar heating element

Claims

1. A pod (1) for an aerosol-generating device (10) comprising a porous wick (2) ; and a reservoir (3) including a discharge opening (4) for an aerosol-generating liquid material, wherein

(i) the porous wick (2) is coated with a temperature- switchable material (6) on a surface of the porous wick (2) sealing the discharge opening (4) of the reservoir (3) so that the temperature-switchable material (6) is arranged between the discharge opening (4) of the reservoir (3) and the porous wick ( 2 ) ; or

(ii) the porous wick (2) is coated with a temperature- switchable material (6) on a surface of the porous wick (2) opposite of the surface of the porous wick (2) sealing the discharge opening (4) so that the porous wick (2) is arranged between the temperature- switchable material (6) and the reservoir (3) ; or

(iii) the porous wick (2) is made of the temperature- switchable material (6) and is arranged so that a surface of the porous wick (2) seals the discharge opening (4) of the reservoir (3) , wherein the temperature-switchable material (6) is an amphiphilic material being impermeable for an aerosolgenerating liquid material below a transition temperature of between 25 °C and 300 °C and becoming permeable for an aerosol-generating liquid material when being exposed to a temperature above said transition temperature.

2. The pod (1) for an aerosol-generating device (10) according to claim 1, wherein the transition temperature is between 50 °C and 100 °C.

3. The pod (1) for an aerosol-generating device (10) according to claim 1 or 2, wherein the temperature-switchable material (6) is a porous material made from silicon alkoxide.

4. The pod (1) for an aerosol-generating device (10) according to claim 3, wherein the silicon alkoxide contains at least one of phenyltriethoxysilane (PhTEOS) , methyltriethoxysilane (MTEOS) and tetraethyl-orthosilicate (TEOS) .

5. The pod (1) for an aerosol-generating device (10) according to claim 4, wherein the silicon alkoxide contains phenyltriethoxysilane (PhTEOS) or methyltriethoxysilane (MTEOS) and tetraethyl-orthosilicate (TEOS) in a ratio of 1:3 to 2:1.

6. The pod (1) for an aerosol-generating device (10) according to any one of claims 3 to 5, wherein the porous material made from silicon alkoxide is a sol-gel foam.

7. The pod (1) for an aerosol-generating device (10) according to option (ii) or option (iii) of any one of claims 1 to 6, wherein the temperature-switchable material (6) comprises a vapor channel structure (7) forming channels in a surface of the porous wick (2) opposite of the surface sealing the discharge opening (4) .

8. The pod (1) for an aerosol-generating device (10) according to claim 7, wherein the vapor channel structure (7) has a geometrical structure selected from the group consisting of pin fins, rectangular channels, circular channels, re-entrant cavities and flow mixer structures.

9. The pod (1) for an aerosol-generating device (10) according to claim 7 or 8, wherein the pod (1) further comprises a heat transfer material layer (8) arranged adjacent to the vapor channel structure (7) comprised in the temperature-switchable material (6) .

10. The pod (1) for an aerosol-generating device (10) according to claim 9, further comprising a metal mesh (9) with a temperature-switchable coating, the metal mesh (9) being arranged between the vapor channel structure (7) of the temperature-switchable material (6) and the heat transfer material layer (8) and the metal mesh (9) being in direct contact with the heat transfer material layer (8) .

11. The pod (1) for an aerosol-generating device (10) according to any one of claims 1 to 10, wherein the thickness of the temperature-switchable material (6) is between 0.001 mm and 10 mm in a pod (1) according to option (i) or option (ii) and wherein the thickness of the temperature-switchable material (6) is between 0.01 mm and 10 mm in a pod (1) according to option (iii) .

12. The pod (1) for an aerosol-generating device (10) according to option (i) or (ii) of any one of claims 1 to 11, wherein the porous wick (2) is made of ceramic, silica or cotton .

13. The pod (1) for an aerosol-generating device (10) according to any one of claims 1 to 12, further comprising an airflow channel (5) configured to allow air entering the pod

(1) through an inlet (5a) , being guided through a porous wick

(2) and/or along a surface of the porous wick (2) , and exiting the pod (1) though an outlet (5b) .

14. An aerosol-generating device (10) comprising the pod (1) as defined in any one of claims 1 to 13 and a heater unit (11) configured to distribute heat to the porous wick (2) and the temperature-switchable material (6) of the pod (1) .