Vaporizer assembly for an aerosol generating system

Abstract

An evaporator assembly for an aerosol generating system. The evaporator assembly includes a capillary element (2) made of porous glass. The capillary element has a first end (4) and a second end (6). The evaporator assembly also includes a heater element (8). The first end of the capillary element is configured to be fluidically connected to a liquid storage portion (10). The heater element is disposed at the second end of the capillary element. The pore size of the capillary element is configured to allow a liquid aerosol-forming matrix from the liquid storage portion to be transferred from the first end of the capillary element to the second end of the capillary element by capillary action. The average pore size of the capillary element varies from large pores at the first end of the capillary element to small pores at the second end of the capillary element, so as to provide a pore size gradient from the first end of the capillary element to the second end of the capillary element.

Description

[0001] This application is a divisional application of the Chinese invention patent application with national application number 201780032690.0, international application number PCT / EP2017 / 064045, application date June 8, 2017, and invention name “Evaporator assembly for aerosol generating system”. Technical Field

[0002] The present invention relates to a vaporizer assembly for an aerosol generating system and an aerosol generating system having the vaporizer assembly. Background Art

[0003] A handheld electrically operated aerosol generating system is known, which consists of a device part and a separate cartridge, wherein the device part includes a battery and control electronics, and the separate cartridge includes a liquid aerosol forming substrate supply and an electrically operated vaporizer or heater element held in a liquid storage part. The liquid storage part may include a capillary material, in which the liquid aerosol forming substrate is absorbed. The capillary material contacts the heater element and ensures that the liquid is transferred to the heater element, thereby allowing steam to be generated. The steam is then cooled to form an aerosol. For example, as known from WO 2015 / 117702 A1, the capillary material may have a fibrous or sponge-like structure. The capillary material may be a porous material that transfers liquid from the liquid storage part to the heater element. The capillary material and the heater element are arranged in the cartridge together with the liquid storage part. The cartridge is arranged as a disposable cartridge, and the cartridge is discarded once the liquid aerosol forming substrate held in the liquid storage part is exhausted. The capillary material and the heater element are therefore discarded together with the cartridge, and each new cartridge requires a new capillary material and a new heater element. Furthermore, during use, undesirable combustion residues may form on the surface of the capillary material.

[0004] It is desirable to provide an evaporator assembly which is easy to clean and reusable, thereby reducing the cost of consumables. Furthermore, it is desirable to provide an evaporator assembly which has increased heat resistance and which avoids or at least reduces the risk of emitting undesirable products when operating at high temperatures. Summary of the invention

[0005] According to a first aspect of the present invention, there is provided an evaporator assembly for an aerosol generating system, comprising a capillary element, the capillary element comprising porous glass. The capillary element has a first end and a second end. The evaporator assembly further comprises a heater element. The first end of the capillary element is configured to be fluidically connected to a liquid storage portion, and the heater element is disposed at the second end of the capillary element. The pore size of the capillary element is configured to allow a liquid aerosol-forming matrix from the liquid storage portion to be transferred from the first end of the capillary element to the second end of the capillary element by capillary action. The average pore size of the capillary element varies from large pores at the first end of the capillary element to small pores at the second end of the capillary element, thereby providing a pore size gradient from the first end of the capillary element to the second end of the capillary element.

[0006] Since the capillary element is made of glass, the heater element can be directly disposed on the capillary element. In this respect, the advantage of the porous glass of the capillary element is that the glass has an increased heat resistance. Therefore, even if the heater element is directly disposed on the capillary element or in the vicinity of the capillary element, the capillary element will not be damaged or destroyed due to the temperature increase of the heating element during the heating process.

[0007] The increased heat resistance of the capillary element also has the effect of reducing the risk of emission of undesirable products during heating of the liquid aerosol-forming substrate by the heater element.

[0008] In addition, since the capillary element is made of porous glass, the capillary element can be easily cleaned. When the user replaces the replaceable liquid storage part, the user can manually clean the capillary element. In addition or in addition, the capillary element can be cleaned during the insertion of the capillary element into the new liquid storage part.

[0009] By providing porous glass in the capillary element, improved cleaning and heat resistance synergistically improve the reusability of the evaporator assembly. Due to the improved heat resistance, unwanted residues on the capillary element during heating and thus undesirable products are avoided or reduced. The heater element can also be arranged directly on the capillary element or in the vicinity of the capillary element. At the same time, unwanted residues on the capillary element can be easily cleaned.

[0010] Furthermore, glass is a very stable material that does not degrade with temperature. Therefore, multiple replaceable liquid storage sections can be used before the capillary element has to be replaced.

[0011] Each time the liquid storage part is replaced, the liquid storage part can be used without providing a new capillary element and a new heater element. The capillary element and the heater element can be used for a plurality of replaceable liquid storage parts. Therefore, the cost of the replaceable liquid storage part is reduced.

[0012] The capillary element may have a cylindrical form or a different form suitable for being inserted into a replaceable liquid storage portion. The capillary element has a first surface at the first end and a second surface at the second end. The heater element is arranged on the second end surface of the capillary element. The first surface and the second surface may have a circular or elliptical shape. In addition, the first surface and the second surface may have a rectangular shape or a polygonal shape. In addition, the first surface and the second surface may be substantially flat or curved. The side surface is arranged at the circumference between the first end and the second end of the capillary element. The diameter of the first surface and the second surface may be between 1 mm and 15 mm, preferably between 2 mm and 10 mm, more preferably between 3 mm and 7 mm, more preferably between 4 mm and 6 mm, most preferably about 5 mm. The surface area of ​​the first surface and the second surface may be less than 60 square millimeters, preferably less than 50 square millimeters, preferably less than 40 square millimeters, and most preferably about 30 square millimeters. The length of the capillary element may be between 1 mm and 7.5 cm, preferably between 5 mm and 3 cm, and more preferably about 1 cm. The liquid capacity of the capillary element is such that it can hold enough liquid aerosol-forming substrate for 30 to 40 puffs, more preferably about 32 puffs. A 3 second puff may include 1 to 4 milligrams of liquid, preferably 3 to 4 milligrams of liquid. The capacity of the capillary element may be between 30 milligrams and 160 milligrams, preferably between 60 milligrams and 150 milligrams, more preferably between 90 milligrams and 140 milligrams, and most preferably about 130 milligrams.

[0013] The capillary element is made of porous glass. The glass has an internal structure that allows liquid to pass from a first end of the capillary element to a second end of the capillary element. In more detail, the porous glass includes pores that allow liquid to pass through the capillary element.

[0014] In this regard, the pores provided in the capillary element enable the action of intermolecular forces between the liquid aerosol-forming substrate and the surrounding glass material of the capillary element. The size and preferably the diameter of the pores are configured such that a combination of surface tension and adhesive forces between the liquid aerosol-forming substrate and the surrounding glass material of the capillary element results in liquid transport through the capillary element.

[0015] The term "porous" should be understood in a broad sense. The pores of the capillary element are interconnected and may have a fibrous structure. The capillary element preferably comprises a bundle of capillaries. For example, the capillary element is manufactured by assembling and compressing glass particles, similar to the manufacture of ceramics. The size of the pores produced in this process depends on the force applied during compression. The pore size may vary along the cylinder. The holes may be roughly aligned to convey the liquid aerosol-forming matrix to the heater element. The structure of the capillary element forms a plurality of pores through which the liquid can be transported by capillary action. The capillary element may have any suitable capillary action and porosity so as to be used with different liquid physical properties. The liquid has the following physical properties, including but not limited to viscosity, surface tension, density, thermal conductivity, boiling point and vapor pressure, which allow the liquid to be transported by capillary action through the capillary element.

[0016] The capillary element may comprise a plurality of materials, wherein one of these materials is porous glass. The capillary element may also be made completely of porous glass. Furthermore, a plurality of capillary elements may be arranged adjacent to one another, wherein one or more of the above-mentioned capillary elements may be combined.

[0017] The capillary element may have such a form that when the capillary element is inserted into the liquid storage part, the liquid present in the liquid storage part cannot flow through the periphery of the capillary element. Therefore, the liquid can only be transmitted from the liquid storage part through the capillary element. When the liquid storage part is connected to the capillary element, a press-fit can be provided between the capillary element and the liquid storage part so that the liquid from the liquid storage part can only flow out of the liquid storage part through the capillary element. The liquid is prevented from flowing through the side surface of the capillary element by the liquid storage part. In more detail, the press-fit between the capillary element and the liquid storage part prevents the liquid from flowing through the side surface of the capillary element.

[0018] Alternatively, the hole that is arranged in the capillary element is arranged between the first end and the second end of the capillary element longitudinally so that liquid can only flow to the second end of the capillary element from the first end of the capillary element through the capillary element. The capillary element may comprise an outer surface that is impermeable to fluid, such as a coating that is impermeable to fluid. The coating that is impermeable to fluid may be applied to the outer surface of the capillary element to prevent leakage. Alternatively, the capillary element may be inserted into a pipe that is impermeable to fluid, such as a glass tube. Liquid can not flow through the capillary element at the side surface of the capillary element, because the hole is not arranged at the side surface of the capillary element.

[0019] As another alternative, the holes in the capillary element, at the side surface of the capillary element, have a size that prevents liquid from leaking out of the side surface of the capillary element. In other words, the diameter or size of the holes arranged at the side surface of the capillary element is so small that liquid cannot flow through these holes at the side surface of the capillary element.

[0020] In each case, liquid may enter the capillary element at a first end of the capillary element and be transported through the capillary element in the direction of a second end of the capillary element.

[0021] The pores disposed in the porous glass vary in average pore size from large pores at the first end of the capillary element to small pores at the second end of the capillary element. In this manner, a pore size gradient is provided from the first end of the capillary element to the second end of the capillary element.

[0022] Smaller holes produce larger capillary forces or effects. Therefore, smaller holes are provided at the second end of the capillary element to ensure that the liquid aerosol from the liquid storage portion forms a substrate that is extracted from the first end of the capillary element toward the second end. The aperture is configured to optimize flow velocity. Smaller holes can also prevent liquid from leaking out from the capillary element. Only steam can flow through the apertures so that aerosol can be formed subsequently. The aperture of the aperture can be between 0.3 and 250 microns or between 0.5 and 100 microns or between 1 and 20 microns or between 2 and 8 microns or be about 4 microns.

[0023] The average pore size of the hole at the first end of the capillary element is greater than the average pore size of the hole at the second end of the capillary element. The average pore size is the average pore size in the capillary element region. In this way, it can be seen that the liquid aerosol forms a substrate that is more effectively transmitted to the heater element. The pore size of the macropore can be between 5 and 500 microns or between 10 and 250 microns or between 15 and 100 microns or between 20 and 50 microns.

[0024] By providing a pore size gradient, preferably a linear gradient, in the capillary element, the effect is achieved that an aerosol-forming substrate in liquid form can be efficiently and relatively extensively transferred from a liquid storage portion at a first end of the capillary element to a second end of the capillary element adjacent to a heater element. The liquid can then be evaporated by the heater element adjacent to the second end of the capillary element.

[0025] The heater element is arranged at the second end of the capillary element so that the liquid transmitted from the first end to the second end by the capillary element can be evaporated by the heater element. The heater element can be directly arranged on the second end of the capillary element so that the heater element directly contacts the second end of the capillary element. Alternatively, the heater element can be arranged near the second end of the capillary element. In the latter case, the heater element is arranged to heat the second end of the capillary element. The heater element can be arranged at the circumference of the capillary element adjacent to the second end of the capillary element.

[0026] By arranging the heater element at the circumference of the capillary element adjacent to the second end of the capillary element, a compact evaporator assembly including the capillary element and the heater element can be provided. Moreover, efficient evaporation of the liquid transferred from the first end of the capillary element to the second end of the capillary element can be provided. By arranging the heater element at the circumference of the capillary element adjacent to the second end of the capillary element, the capillary element can be easily cleaned because the second end surface of the capillary element is not blocked by the heating element.

[0027] In some embodiments, the heater element is a resistive heater. The heater element comprises a conductive material. The conductive material can be heated by a current flowing through the conductive material. The conductive material can be disposed on an electrically insulating substrate of the heater element.

[0028] The heater element may further comprise a glass material, such that the capillary element and the heater element each comprise a glass material.The electrically conductive material of the heater element may be provided in or on the heater element.

[0029] The resistance of the heater element should be arranged so as to provide sufficient heating of the aerosol-forming substrate at the second end surface of the capillary element. In this regard, the resistance of the conductive material of the heater element may be between 2 ohms and 5 ohms, preferably between 3 ohms and 4 ohms, and most preferably about 3.5 ohms.

[0030] In some embodiments, the heater element may be provided as a metal coating or a film or a mesh heater or a coil. When the heater element is provided as a metal coating, the heater element may be provided directly on the second end surface of the capillary element. In more detail, the second end surface of the capillary element may be provided with a conductive coating that may be heated to evaporate the liquid on the second end surface of the capillary element.

[0031] The heater element may also be arranged as a mesh heater comprising a plurality of conductive filaments. This allows a larger area of ​​the heater element to be in contact with the liquid being evaporated. The conductive filaments may be substantially flat.

[0032] The heater element may be arranged as a heating coil made of an electrically conductive wire.The coil may be wound around the capillary element, and it is advantageous if the heater element is arranged at the circumference of the capillary element adjacent the second end of the capillary element.

[0033] A vaporizer assembly for an aerosol generating system is also provided, comprising a capillary element comprising porous glass. The capillary element has a first end and a second end. The vaporizer assembly further comprises a heater element. The first end of the capillary element is configured to be fluidly connected to a liquid storage portion, and the heater element is disposed at the second end of the capillary element. The pore size of the capillary element is configured to allow a liquid aerosol-forming substrate from the liquid storage portion to be transferred from the first end of the capillary element to the second end of the capillary element by capillary action.

[0034] According to a second aspect of the present invention, there is provided an aerosol generating system comprising a main body, the main body comprising a housing, a power source, an electric circuit and a vaporizer assembly as described in detail above.

[0035] The aerosol generating system may include a replaceable or refillable liquid storage portion. The liquid storage portion is detachably connected to the body. When the liquid storage portion is connected to the body, the first end of the capillary element of the vaporizer assembly is inserted into the liquid storage portion so that the capillary element is in fluid communication with the liquid aerosol-forming substrate stored in the liquid storage portion.

[0036] The liquid storage portion may include additional capillary elements. Additional capillary elements may be arranged in the liquid storage portion. In this case, the glass capillary element of the evaporator may be thin to prevent the heater element from burning the additional capillary element arranged in the liquid storage portion. The thickness of the glass capillary element may be at least 1 mm, preferably at least 2 mm, and more preferably at least 3 mm. The glass capillary element of the evaporator assembly may still include pores so that the liquid aerosol-forming substrate does not leak through the capillary element, but steam may flow through the capillary element to form an aerosol. Additional capillary elements may be provided by conventional porous materials with a sponge-like or fibrous structure. The glass capillary element of the evaporator assembly may be reusable, and additional capillary elements may be arranged together with the liquid storage portion. Therefore, the advantageous properties of glass may be utilized, and only thin glass capillary elements are required in the evaporator.

[0037] The power source may be electrically connected to the heater element of the vaporizer assembly so as to be able to heat the heater element. The circuit controls the flow of current from the power source to the heater element. When the aerosol generating device is actuated by a user, the circuit enables current to flow from the power source to the heater element of the vaporizer assembly, thereby evaporating the aerosol-forming substrate from the liquid storage portion and generating an aerosol. A sensor, such as a flow sensor, may be provided to detect that the user is drawing a puff on the system.

[0038] In some embodiments, a sealing foil can be arranged on the opening of the liquid storage part. During or before the capillary element is inserted into the liquid storage part, the sealing foil is preferably removed. The aerosol generating system preferably also includes a sealing film, which is arranged below the sealing foil. When removing the sealing foil and inserting the capillary element into the liquid storage part, the sealing film may break and be compressed between the circumference of the capillary element and the replaceable liquid storage part. The sealing film is arranged to prevent liquid aerosol from forming a substrate that leaks unexpectedly from the liquid storage part. In other words, when the capillary element is inserted into the liquid storage part, the liquid aerosol forms a substrate that can flow through the capillary element but will not flow through the periphery of the capillary element.

[0039] According to a third aspect of the present invention, a method for manufacturing an evaporator component for an aerosol generating system is provided. The method comprises the following steps: providing a capillary element made of porous glass, the capillary element having a first end and a second end, and providing a heater element. The first end of the capillary element is configured to be fluidically connected to a liquid storage portion, wherein the heater element is disposed at the second end of the capillary element. The pore size of the capillary element is configured to allow a liquid aerosol-forming matrix from the liquid storage portion to be transferred from the first end of the capillary element to the second end of the capillary element by capillary action. The average pore size of the capillary element varies from large pores at the first end of the capillary element to small pores at the second end of the capillary element, so as to provide a pore size gradient from the first end of the capillary element to the second end of the capillary element.

[0040] In some embodiments, the capillary element is manufactured by a phase separation process, a sintering process, or a sol-gel process. These processes provide the capillary element with pores that in turn allow the liquid aerosol-forming substrate to be transmitted through the capillary element. In addition, these processes enable the manufacture of capillary elements having pores of different sizes and having a pore size gradient from the first end of the capillary element to the second end of the capillary element.

[0041] Features described in relation to one aspect may be equally applicable to other aspects of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0043] Figure 1 is a cross-sectional view of one embodiment of an evaporator assembly; and

[0044] Figure 2 is a cross-sectional view of one embodiment of an aerosol generating system. DETAILED DESCRIPTION

[0045] Figure 1 An evaporator assembly according to one embodiment of the present invention is shown.

[0046] The evaporator assembly comprises a capillary element 2 made of porous glass, such as Figure 1 The capillary element 2 comprises holes of preferably different sizes. The capillary element 2 has a first end 4 and a second end 6.

[0047] The porous glass of the evaporator assembly is placed adjacent to the heater element 8. Figure 1 The heater element 8 is shown disposed on the circumference of the porous glass adjacent to the second end 6 of the porous glass. The first end 4 of the capillary element 2 faces the liquid storage portion 10.

[0048] At the first end 4 of the capillary element 2, macropores 12 having an average pore size of about 25 micrometers are provided. Figure 1 The macropores 12 enable the liquid aerosol-forming substrate 14 to be transported from the liquid storage portion 10 through the capillary element 2 in the direction of the second end 6 of the capillary element 2. At the second end 6 of the capillary element 2, small pores 16 having an average pore size of about 4 micrometers are provided, thereby preventing liquid from leaking out of the second end 6 while allowing vapor to flow through the second end 6.

[0049] Figure 2 An aerosol generating system according to one embodiment of the invention is shown. Figure 2 The main body 18 is depicted, which includes the capillary element 2 of the evaporator assembly, the heater element 8 and the circuit and power supply ( Figure 2 The main body also includes an air inlet 20 and an air outlet 22. When the user sucks on the mouthpiece 24, ambient air is sucked through the air inlet 20 and reaches the air outlet 22 through the evaporator assembly. The circuit controls the flow of current from the power supply to the heater element 8 for heating the heater element 8. When the user draws on the mouthpiece 24, the flow sensor can detect it due to the negative pressure in the airflow. Then, the circuit controls the flow of current from the power supply through the heater element. Therefore, the liquid aerosol-forming substrate 14 is evaporated by the heater element 8, thereby generating an aerosol, which is then inhaled by the user.

[0050] The liquid storage portion 10 is provided with a sealing foil 26 which is arranged on the liquid storage portion 10. The sealing foil 26 prevents the aerosol-forming substrate 14 from leaking out of the liquid storage portion 10. The sealing foil 26 is removed before the liquid storage portion 10 is connected to the body 18. Under the sealing foil 26, a sealing film 28 is provided which covers the liquid storage portion 10. As described below, when the capillary element 2 is inserted into the liquid storage portion 10, the sealing film 28 is provided to seal the periphery of the capillary element 2.

[0051] When the liquid storage portion 10 is connected to the main body 18, the capillary element 2 of the evaporator assembly is inserted into the liquid storage portion 10. The capillary element 2 is inserted into the liquid storage portion 10 so that the first end 4 of the capillary element 2 is first inserted into the liquid storage portion 10. During the insertion of the capillary element 2 into the liquid storage portion 10, the sealing film 28 is broken and pressed against the inner wall of the liquid storage portion 10. The sealing film 28 can be provided with a predetermined breaking area or a predetermined breaking point or an area with small damage to locate and promote the breaking. Therefore, the liquid aerosol-forming substrate 14 can only flow through the capillary element 2, and the periphery of the capillary element 2 is sealed by the sealing film 28.

[0052] The liquid aerosol-forming substrate 14 may then be transported by capillary action in a direction 30 from the interior of the liquid storage portion 10 through the first end 4 of the capillary element 2 of the vaporizer assembly towards the second end 6 to the heater element 8 of the vaporizer assembly.

[0053] The above exemplary embodiments are illustrative and not limiting. In view of the exemplary embodiments discussed above, other embodiments consistent with the above exemplary embodiments will be apparent to those of ordinary skill in the art.

[0054] Reference numerals

[0055] 2 Capillary element

[0056] 4. The first end of the capillary element, the surface of the first end of the capillary element

[0057] 6. The second end of the capillary element, the second end surface of the capillary element

[0058] 8 Heater element

[0059] 10 Liquid storage section

[0060] 12 Large hole

[0061] 14 Liquid aerosol forming matrix

[0062] 16 Small holes

[0063] 18 Main Body

[0064] 20 Air inlet

[0065] 22 Air outlet

[0066] 24 Cigarette holder

[0067] 26 Sealing foil

[0068] 28 Sealing film

[0069] 30 Direction of transport of liquid aerosol-forming substrate

Claims

1. A vaporizer assembly for an aerosol generating system, comprising: a one-piece capillary element made of porous glass, the capillary element having a first end and a second end; and Heater element, wherein the first end of the capillary element is configured to be fluidly connected to a liquid storage portion, wherein the heater element is disposed at the second end of the capillary element, and wherein the pore size of the capillary element is configured to allow liquid aerosol-forming substrate from the liquid storage portion to be transferred from the first end of the capillary element to the second end of the capillary element by capillary action, and The average pore size of the capillary element varies from large pores at the first end of the capillary element to small pores at the second end of the capillary element, so as to provide a pore size gradient from the first end of the capillary element to the second end of the capillary element.

2. The evaporator assembly of claim 1, wherein the capillary element has a generally cylindrical shape having a first surface at the first end and a second surface at the second end, wherein the heater element is disposed on the second end surface of the capillary element. 3 . The evaporator assembly of claim 1 , wherein the heater element is disposed at a circumference of the capillary element adjacent the second end of the capillary element. The evaporator assembly of claim 1 , wherein the heater element is a resistive heater.

5. The evaporator assembly of claim 1, wherein the heater element is configured as a metal coating, a mesh heater, or a coil.

6. The evaporator assembly of claim 1, wherein the average pore size of the small pores is between 2 and 8 microns, and the average pore size of the large pores is between 5 and 500 microns.

7. An evaporator assembly according to claim 1, wherein the porosity of the pores at the second end of the capillary element is such that it prevents the liquid aerosol-forming substrate from leaking through the second end surface of the capillary element while allowing aerosol to pass through the second end surface of the capillary element.

8. The evaporator assembly of claim 1, wherein the pores have a pore size between 0.3 and 250 microns.

9. The evaporator assembly of claim 1, wherein the macropores have a pore size between 5 and 500 microns.

10. An aerosol generating system comprising: A main body comprising a housing, a power source, a circuit and the evaporator assembly according to claim 1.

11. An aerosol generating system according to claim 10, further comprising a replaceable liquid storage part, which is detachably connected to the main body, wherein when the liquid storage part is connected to the main body, the first end of the capillary element of the evaporator assembly is inserted into the liquid storage part, so that the capillary element is in fluid communication with the liquid aerosol-forming matrix stored in the liquid storage part.

12. An aerosol generating system according to claim 11, further comprising a sealing element disposed between the periphery of the capillary element and the replaceable liquid storage portion to prevent undesired leakage of the liquid aerosol-forming substrate from the liquid storage portion.

13. A method of manufacturing a vaporizer assembly for an aerosol generating system, comprising: providing a one-piece capillary element made of porous glass, the capillary element having a first end and a second end; as well as Provide heater element, wherein the first end of the capillary element is configured to be fluidly connected to a liquid storage portion, wherein the heater element is disposed at the second end of the capillary element, and wherein the pore size of the capillary element is arranged to allow liquid aerosol-forming substrate from the liquid storage portion to be transferred from the first end of the capillary element to the second end of the capillary element by capillary action, and wherein the average pore size of the capillary element varies from large pores at the first end of the capillary element to small pores at the second end of the capillary element such that a pore size gradient is provided from the first end of the capillary element to the second end of the capillary element.

14. The method of claim 13, wherein the capillary element is manufactured by a phase separation process, a sintering process, or a sol-gel process.

15. A vaporizer assembly for an aerosol generating system, comprising: a one-piece capillary element made of porous glass, the capillary element having a first end and a second end; and Heater element, wherein the first end of the capillary element is configured to be fluidly connected to a liquid storage portion, wherein the heater element is disposed at the second end of the capillary element, and wherein the pore size of the capillary element is configured to allow liquid aerosol-forming substrate from the liquid storage portion to be transferred from the first end of the capillary element to the second end of the capillary element by capillary action, and wherein the average pore size of the capillary element varies from large pores at the first end of the capillary element to small pores at the second end of the capillary element so as to provide a pore size gradient from the first end of the capillary element to the second end of the capillary element; wherein the porosity of the pores at the second end of the capillary element is such that they prevent the liquid aerosol-forming substrate from leaking through the second end surface of the capillary element while allowing aerosol to pass through the second end surface of the capillary element.

16. A vaporizer assembly for an aerosol generating system, comprising: a one-piece capillary element made entirely of porous glass, the capillary element having a first end and a second end; and Heater element, wherein the first end of the capillary element is configured to be fluidly connected to a liquid storage portion, wherein the heater element is disposed at the second end of the capillary element, and wherein the pore size of the capillary element is configured to allow liquid aerosol-forming substrate from the liquid storage portion to be transferred from the first end of the capillary element to the second end of the capillary element by capillary action, and wherein the average pore size of the capillary element varies from large pores at the first end of the capillary element to small pores at the second end of the capillary element so as to provide a pore size gradient from the first end of the capillary element to the second end of the capillary element; Wherein, the pore size gradient of the capillary element is a linear pore size gradient.

17. A vaporizer assembly for an aerosol generating system, comprising: a one-piece capillary element made of porous glass, the capillary element having a first end and a second end; and Heater element, wherein the first end of the capillary element is configured to be fluidly connected to a liquid storage portion, wherein the heater element is disposed at the second end of the capillary element, and wherein the pore size of the capillary element is configured to allow liquid aerosol-forming substrate from the liquid storage portion to be transferred from the first end of the capillary element to the second end of the capillary element by capillary action, and wherein the average pore size of the capillary element varies from large pores at the first end of the capillary element to small pores at the second end of the capillary element so as to provide a pore size gradient from the first end of the capillary element to the second end of the capillary element; Wherein, the length of the capillary element is between 1 mm and 7.5 cm.

18. A vaporizer assembly for an aerosol generating system, comprising: a one-piece capillary element made of porous glass, the capillary element having a first end and a second end; and Heater element, wherein the first end of the capillary element is configured to be fluidly connected to a liquid storage portion, wherein the heater element is disposed at the second end of the capillary element, and wherein the pore size of the capillary element is configured to allow liquid aerosol-forming substrate from the liquid storage portion to be transferred from the first end of the capillary element to the second end of the capillary element by capillary action, and wherein the average pore size of the capillary element varies from large pores at the first end of the capillary element to small pores at the second end of the capillary element so as to provide a pore size gradient from the first end of the capillary element to the second end of the capillary element; The capillary element further comprises a side surface between the first end and the second end thereof, wherein the capillary element comprises a fluid-impermeable outer surface such that liquid cannot flow through the capillary element at the side surface of the capillary element.

19. A vaporizer assembly for an aerosol generating system, comprising: a one-piece capillary element made of porous glass, the capillary element having a first end and a second end; and Heater element, wherein the first end of the capillary element is configured to be fluidly connected to a liquid storage portion, wherein the heater element is disposed at the second end of the capillary element, and wherein the pore size of the capillary element is configured to allow liquid aerosol-forming substrate from the liquid storage portion to be transferred from the first end of the capillary element to the second end of the capillary element by capillary action, and wherein the average pore size of the capillary element varies from large pores at the first end of the capillary element to small pores at the second end of the capillary element so as to provide a pore size gradient from the first end of the capillary element to the second end of the capillary element; The capillary element further comprises a side surface between the first end and the second end thereof, wherein at the side surface of the capillary element, the hole in the capillary element has a size preventing liquid from leaking out from the side surface of the capillary element.

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