Heater module for aerosol-generating device with localised dielectric heating

Abstract

A heater module (1) for an aerosol-generating device (100) configured to dielectrically heat an aerosol-generating article (10). The heater module (1) comprises a chamber (2) configured to receive at least a portion of an aerosol-generating article (10) to be heated. The heater module (1) comprises a chamber housing (3), the chamber (2) being disposed in the chamber housing (3). The chamber housing (3) comprises a first region (21) having a first material property, and a second region (22) having a second material property. The first material property and the second material property are such that an electric field in the chamber (2) and chamber housing (3) is greater in the chamber (2) at the second region (22) of the chamber housing (3) compared to the electric field in the chamber (2) at the first region (21) of the chamber housing (3).

Description

[0001] HEATER MODULE FOR AEROSOL-GENERATING DEVICE WITH LOCALISED DIELECTRIC HEATING

[0002] The present disclosure relates to a heater module for an aerosol-generating device, and particularly to a heater module for an aerosol-generating device configured to dielectrically heat an aerosol-generating article. The disclosure also relates to an aerosol-generating device configured to dielectrically heat an aerosol-generating article, and an aerosol-generating system configured to dielectrically heat an aerosol-generating article.

[0003] Known electrically operated aerosol-generating systems typically heat an aerosol-forming substrate by one or more of: conduction of heat from a heating element to an aerosol-forming substrate, radiation from a heating element to an aerosol-forming substrate, or drawing heated air through an aerosol-forming substrate. Most commonly, heating is achieved by passing an electrical current through an electrically resistive heating element, giving rise to Joule heating of the heating element. Inductive heating systems have also been proposed, in which heating occurs as a result of eddy currents induced in a susceptor heating element.

[0004] These heating mechanisms tend to give rise to localised heating of the aerosol-forming substrate. For example, the portion of the aerosol-forming substrate closest to the heating element may be heated more quickly or to a higher temperature than portions of the aerosol-forming substrate more remote from the heating element.

[0005] Systems that dielectrically heat an aerosol-forming substrate have also been proposed. Dielectric heating, which is also often referred to as microwave heating, radio-frequency heating, or electric heating, generally refers to heating that arises as a result of dipole rotation of a to-be-heated material or substance that is subjected to an alternating electric field, and particularly a high-frequency alternating electric field. When an alternating electric field is applied to materials or substances containing polar molecules (i.e. molecules having an electrical dipole moment), the polar molecules align themselves in the electric field and rotate when the electric field alternates to maintain alignment with the electric field. This rotation (dipole rotation) results in heating of the material or substance in the alternating electric field.

[0006] Systems that dielectrically heat an aerosol-forming substrate advantageously can be configured to provide uniform heating of the aerosol-forming substrate. However, there is the potential for the aerosol-forming substrate to become prematurely depleted when using a RF electric field to uniformly heat the substrate. Moreover, there is also the potential that it is difficult to selectively heat different areas of the substrate, to perform sectional or partial heating of the substrate.

[0007] It would be desirable to provide an improved aerosol-generating system that dielectrically heats an aerosol-forming substrate. It would be desirable to provide a system that dielectrically heats an aerosol-forming substrate with greater effectiveness, while still being realisable in a compact or handheld system. It would be desirable to provide a system that dielectrically heats an aerosol-forming substrate which is able to initiate generation of aerosol from the aerosol-forming substrate in a reduced time. It would be desirable to provide a system that dielectrically heats an aerosol-forming substrate at different areas or volumes at a given time, without the need of complex control and heating arrangements.

[0008] According to the present disclosure, there is provided a heater module for an aerosol-generating device. The aerosol-generating device may be configured to dielectrically heat an aerosol-generating article. The heater module may comprise a chamber. The chamber may be configured to receive at least a portion of an aerosol-generating article to be heated. The heater module may comprise a chamber housing. The chamber may be disposed in the chamber housing. The chamber housing may comprise a first region. The first region may have a first material property. The chamber housing may comprise a second region. The second region may have a second material property. The first material property and the second material property may be such that an alternating electric field created in the chamber and chamber housing is greater in the chamber at the second region of the chamber housing compared to the alternating electric field in the chamber at the first region of the chamber housing. The first material property and the second material property may be such that an intensity of an alternating electric field created in the chamber and chamber housing is greater in the chamber at the second region of the chamber housing compared to the intensity of the alternating electric field in the chamber at the first region of the chamber housing.

[0009] The inventors have recognised that surrounding a chamber for receiving an aerosol-generating article with a dielectric chamber housing, having uniform properties, such as relative permittivity and electrical conductivity, can result in a substantially uniform electric field being generated in the chamber. The inventors have also recognised that generating a uniform electric field in the chamber may not be appropriate or useful for all aerosol-generating devices that heat an aerosol-generating article using dielectric heating. In other words, the inventors have recognised that it can be beneficial to generate localised electric field enhancement in one or more regions of the chamber.

[0010] Advantageously, the inventors have found that providing a chamber housing with regions having different material properties, such as relative permeabilities and electrical conductivities, can result in an electric field generated in the article cavity that is concentrated in selected regions of the chamber. Concentrating the electric field in selected regions of the chamber can result in localised heating of an aerosol-generating article in the chamber. In this way, the structure of the chamber housing may be designed to shape the electric field in the article cavity, which may be used to heat different sections of an aerosol-generating article received in the chamber to different temperatures.

[0011] The first material property and the second material property may be such that an electric field created in the chamber and chamber housing is greater in the chamber at and around the second region of the chamber housing compared to the electric field in the chamber at and around the first region of the chamber housing, for example, the amplitude or intensity of the alternating electric field at and around the second region will be greater than the amplitude or intensity of the alternating electric field at and around the first region of the chamber housing. In other words, the electric field in the chamber is greater at regions of the chamber near or adjacent to the second region of the chamber housing compared to the electric field at regions of the chamber near or adjacent to the first region of the chamber housing. Where the first region of the chamber housing substantially circumscribes a portion of the chamber, and the second region of the chamber housing substantially circumscribes a portion of the chamber, the electric field in the portion of the chamber circumscribed by the second region of the chamber housing is greater than the electric field in the portion of the chamber circumscribed by the first region of the chamber housing.

[0012] As used herein, a “greater” or “lower” electric field refers to the amplitude, strength or intensity of the alternating electric field. Where an alternating electric field is created in the chamber, the strength of the alternating electric field in the chamber determines the heating of the aerosol-forming substrate received in the chamber. Accordingly, an aerosol-forming substrate received in the chamber is heated more rapidly in regions of the chamber in which an alternating electric field is greater compared to other regions of the chamber.

[0013] According to the present disclosure, there is provided a heater module for an aerosol-generating device. The aerosol-generating device may be configured to dielectrically heat an aerosol-generating article. The heater module may comprise a chamber. The chamber may be configured to receive at least a portion of an aerosol-generating article to be heated. The heater module may comprise a chamber housing. The chamber may be disposed in the chamber housing. The chamber housing may comprise a first region. The chamber housing may comprise a second region.

[0014] According to the present disclosure, there is provided a heater module for an aerosol-generating device configured to dielectrically heat an aerosol-generating article. The heater module comprises a chamber configured to receive at least a portion of an aerosol-generating article to be heated. The heater module comprises a chamber housing. The chamber is disposed in the chamber housing. The chamber housing comprises a first region, and a second region.

[0015] In some preferred embodiments, the first region is a dielectric region having a first relative permittivity, and the second region is a dielectric region having a second relative permittivity. The second relative permittivity is less than the first relative permittivity.

[0016] Advantageously, providing the chamber housing with one or more regions having a lower relative permittivity compared to one or more other regions can concentrate the electric field in the article cavity in selected regions of the chamber, resulting in localised heating of an aerosol-generating article in the chamber.

[0017] In some preferred embodiments, the first region is a dielectric region, and the second region is a region comprising an electrically conductive material. The first region has a first electrical conductivity. The second region has a second electrical conductivity. The second electrical conductivity is greater than the first electrical conductivity. Advantageously, providing the chamber housing with one or more regions comprising an electrically conductive material, and one or more dielectric regions, can concentrate the electric field generated in the article cavity in selected regions of the chamber, resulting in localised heating of an aerosol-generating article in the chamber.

[0018] As used herein, the term “relative permittivity”, Er, which may also be referred to as the “dielectric constant”, is used to mean the ratio of the electric permittivity of a material or substance or region to the electric permittivity of a vacuum, Eo. AS used herein, the term “relative permittivity” refers to the real part of the complex, frequency-dependent relative permittivity, measured at a temperature of 20 degrees Celsius, in an alternating electric field with a frequency of 1 Kilohertz.

[0019] As used herein, the term “electrically conductive material” denotes a material having a resistivity of 1x1 O'2Ohm-metres, Qm, or less, at a temperature of 20 degrees Celsius. Preferably, an electrically conductive material has a resistivity of 1.5x1 O'06Ohm-meters, or less, at a temperature of 20 degrees Celsius, and preferably at least 5x1 O'7Ohm-metres, or less, at a temperature of 20 degrees Celsius.

[0020] As used herein, the term “electrically insulative material” denotes a material having a resistivity of 1x104Ohm-metres, or more, at a temperature of 20 degrees Celsius.

[0021] As used herein, the terms “dielectric region” and “dielectric material”, refer to an electrically insulative region or an electrically insulative material that becomes polarized under the influence of an external electric field.

[0022] Preferably, the heater module comprises a coupler. The coupler may be configured to couple an alternating electric field generator to the chamber for creating an alternating electric field in the chamber.

[0023] Preferably, the heater module comprises a module housing. The module housing may substantially circumscribe the chamber housing. Preferably, the module housing comprises an electrically conductive material. Preferably, the module housing forms a faraday cage around the chamber housing and the chamber. The module housing may comprise an opening to enable an aerosol-generating article to be received in the chamber. The module housing may comprise an opening to enable at least a portion of a coupler to be received in the chamber.

[0024] In some preferred embodiments, the heater module comprises a cavity resonator. The chamber and the chamber housing may be positioned in or arranged in a cavity resonator. The module housing may form the cavity resonator. The module housing, the chamber housing, and the chamber may form the cavity resonator. The module housing, the chamber housing, the chamber, and the coupler may form the cavity resonator. The module housing, the chamber housing, the chamber, the coupler, and an aerosol-generating article received in the chamber may form the cavity resonator. In other words, the system comprising the module housing, the chamber housing, the chamber, and the coupler may be a resonant system having one or more resonant frequencies. In other words, the system comprising the module housing, the chamber housing, the chamber, the coupler, and at least a portion of an aerosol- generating article received in the chamber may be a resonant system having one or more resonant frequencies.

[0025] Advantageously, arranging the chamber housing in a cavity resonator may enable the electric field created in the chamber to be created at a lower frequency for a given size of cavity resonator, compared to a cavity resonator of the same size without the chamber housing. This is because the chamber housing comprises the first region, which is a dielectric region. Typically, the first region has a relative permittivity that is greater than that of air. Providing a first region of the chamber housing that has a relative permittivity that is greater than that of air may result in the resonant cavity having a reduced resonant frequency compared to a resonant cavity of the same size, where the chamber housing is removed and replaced with air.

[0026] For the same reason, positioning the chamber housing in the cavity resonator may enable the size of the cavity resonator to be reduced for an electric field created in the cavity resonator at a given frequency, compared to a resonant cavity without the chamber housing.

[0027] Advantageously, reducing the frequency of the electric field that is required to be created in the chamber without increasing the size of the cavity resonator may enable the heater module to be used in a handheld, battery powered, aerosol-generating device, which is required to be as small and lightweight as possible. Similarly, reducing the size of the cavity resonator without increasing the frequency of the electric field that is required to be created in the chamber may enable the heater module to be used in a handheld, battery powered, aerosol-generating device, which is required to be as small and lightweight as possible.

[0028] The chamber may have any suitable shape and dimensions to receive an aerosol-generating article.

[0029] The chamber may have a length, in a longitudinal direction. The length of the chamber may be the greatest dimension of the chamber. The length may be any suitable length. For example, the chamber housing may have a length in a range of between 5 and 50 millimetres. The chamber may be elongate, having a length that is greater than the other dimensions of the chamber.

[0030] The chamber may have a width, in a transverse direction, perpendicular to the longitudinal direction. The chamber housing may have a width in a range of between 1 millimetre and 10 millimetres, more preferably between 2 millimetres and 5 millimetres.

[0031] The chamber may have a central longitudinal axis. The central longitudinal axis may extend in the longitudinal direction. The chamber may have a radial direction, extending from the central longitudinal axis in a direction perpendicular to the central longitudinal axis. Where a feature extends “radially outwards” from the chamber, the feature may extend in the radial direction away from the central longitudinal axis.

[0032] A ratio between the length and the width of the chamber housing may lie in a range of 2 to 20, preferably between 4 to 10. The chamber may have a transverse cross-sectional shape, perpendicular to the longitudinal direction, which may be one of: circular, elliptical, stadium shaped, polygonal, rectangular, trapezoidal, pentagonal, or hexagonal.

[0033] In some preferred embodiments, the chamber is substantially cylindrical, particularly circularly cylindrical. In some preferred embodiments, the chamber is substantially cuboidal, particularly rectangularly cuboidal.

[0034] The chamber may be open at one end. The chamber may be open at one end to enable an aerosol-generating article to be inserted into the chamber. The chamber may be open at two ends. The chamber may be open at opposing ends.

[0035] An aerosol-generating article may have a complimentary shape and dimensions, such that at least a portion of the aerosol-generating article may be received in the chamber of the aerosolgenerating device, as described in more detail below.

[0036] The heater module comprises a chamber housing. The chamber is disposed in the chamber housing. In some embodiments, the chamber housing defines the chamber. In some embodiments, at least a surface of the chamber housing defines a surface of the chamber.

[0037] The chamber housing may have any suitable shape and dimensions.

[0038] The chamber housing may have a length, in a longitudinal direction. The length of the chamber housing may be the greatest dimension of the chamber housing. The length may be any suitable length. The chamber housing may be elongate, having a length that is greater than the other dimensions of the chamber housing.

[0039] The chamber housing may have a width, in a transverse direction, perpendicular to the longitudinal direction.

[0040] The chamber housing may have a transverse cross-sectional shape, perpendicular to the longitudinal direction. The transverse cross-sectional shape of the chamber housing may be one of: circular, elliptical, stadium shaped, polygonal, rectangular, trapezoidal, pentagonal, or hexagonal.

[0041] In some preferred embodiments, the chamber housing is substantially cylindrical, particularly circularly cylindrical. In some preferred embodiments, the chamber housing is substantially cuboidal, particularly rectangularly cuboidal.

[0042] The chamber may be disposed in the chamber housing in any suitable location. Preferably, the chamber is disposed centrally in the chamber housing. The chamber may extend through the chamber housing. The chamber may extend through the chamber housing from one end to the other. The chamber housing may substantially circumscribe the chamber. The chamber housing may be substantially annular. The chamber housing may be substantially annular, having an inner passage defining the chamber.

[0043] The chamber housing comprises a first region and a second region. The first region has a first material property. The second region has a second material property. The first material property and the second material property are such that an electric field in the chamber and chamber housing is greater at the second region of the chamber housing. The first material property and the second material property are such that an electric field in the chamber and chamber housing may be greater around the second region of the chamber housing.

[0044] In some preferred embodiments, the first material property is uniform throughout the first region. However, it is envisaged that in some embodiments, the first material property may not be uniform throughout the first region.

[0045] In some preferred embodiments, the second material property is uniform throughout the second region. However, it is envisaged that in some embodiments, the second material property may not be uniform throughout the second region.

[0046] The first material property may be relative permittivity. The relative permittivity of the first region may be greater than 1 . The first region may be a dielectric region. The relative permittivity of the first region may be any suitable value. For example, the relative permittivity of the first region may be at least 5, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, or at least 40. In some embodiments, the relative permittivity of the first region is between 5 and 100. In some embodiments, the relative permittivity of the first region is between 40 and 50.

[0047] The first material property may be electrical conductivity. The first region may be an electrically insulative region. The first region may be a dielectric region. The first region may have an electrical conductivity of 1x1 O'4Siemens per metre (S / m), or less, at a temperature of 20 degrees Celsius. The first material property may be electrical resistivity. The first region may have an electrical resistivity of 1x104Ohm-metres (Qm), or more, at a temperature of 20 degrees Celsius.

[0048] The first region may comprise a first material. The first material may have the first material property. The first region may comprise a solid body of the first material. The first material may be any suitable material. The first material may be an electrically insulative material. The first material may be a dielectric material. The relative permittivity of the first material may be any suitable value. The first material may have a relative permittivity greater than 1. The relative permittivity of the first material may be at least 5, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, or at least 40. In some embodiments, the relative permittivity of the first material is between 5 and 100. In some embodiments, the relative permittivity of the first material is between 40 and 50.

[0049] The first material may be a ceramic material. For example, the first material may comprise or consist of at least one of: alumina, MgNb20e, ZnNb20e, MgTa2Oe, ZnTa2Oe, ZrSnTiO4 , Zn, Mg, Ta-based Perovskite, Barium oxide (BaO ) doped with one or more of Zn, Mg, Ta, Nb, Nd, La, Ti, Co, tungsten bronze, barium samarium titanium oxide (Ba6-3xSm8+2xTii8Os4), and glass; the table below details values of relative permittivity Erfor these exemplary filling materials:

[0050] In some embodiments, the first material may be a polymeric material.

[0051] Preferably, the first region comprises a material that is able to tolerate high temperatures, such as temperatures in the range 150 degrees Celsius to 350 degrees Celsius, or in the range from 250 degrees Celsius to 350 degrees Celsius, and rapid temperature changes.

[0052] The first region may have any suitable shape or size.

[0053] The first region may have a length, in a longitudinal direction. The length may be any suitable length. The first region may be elongate, having a length that is greater than the other dimensions of the first region.

[0054] The first region may have a width, in a transverse direction, perpendicular to the longitudinal direction.

[0055] The first region may have a transverse cross-sectional shape, perpendicular to the longitudinal direction. The transverse cross-sectional shape of the first region may be one of: circular, elliptical, stadium shaped, polygonal, rectangular, trapezoidal, pentagonal, or hexagonal.

[0056] In some preferred embodiments, the first region is substantially cylindrical. In some embodiments, the first region is a circular cylinder. In some preferred embodiments, the first region is substantially cuboidal. In some embodiments, the first region is a rectangular cuboid.

[0057] The first region may substantially circumscribe a portion of the chamber. The first region may be substantially annular. The first region may be substantially annular, having an inner passage defining a portion of the chamber. The first region may form an annular disc circumscribing a portion of the chamber. The first region may substantially circumscribe a portion of the chamber and extend radially outwards from the chamber. The first region may form a volume or a body that circumscribes the chamber and extends radially outwards from the chamber.

[0058] In some preferred embodiments, a boundary of the first region is at a boundary of the chamber. In some preferred embodiments, a boundary of the first region defines a boundary, or a portion of a boundary, of the chamber. In some embodiments, a surface of the first region may define a surface, or a portion of a surface, of the chamber. In some embodiments, the first region intersects the chamber.

[0059] The first region may extend from the module housing to a boundary of the chamber. The first region may extend from the module housing. The first region may extend from a boundary of the chamber. Where the first region comprises a first material, the first material may extend from the module housing to a boundary of the chamber. The first material may extend from a boundary of the second region. The first material may extend from the module housing to a boundary of the chamber. In some embodiments, the first material may extend from a boundary of the chamber part of the way to the module housing. In some embodiments, the first material may extend from the module housing part of the way to the boundary of the chamber. The first region may extend radially outwards from the chamber to the module housing. The first region may extend radially outwards from the chamber and not extend to the module housing.

[0060] The second material property may be relative permittivity. The relative permittivity of the second region may be greater than 1. The second region may be a dielectric region. The relative permittivity of the second region may be any suitable value. For example, the relative permittivity of the second region may be 35 or less, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, 5 or less, or about 1 .

[0061] The second material property may be electrical conductivity. The second region may be an electrically conductive region. The second region may have an electrical conductivity of 1x102Siemens per metre (S / m), or more, at a temperature of 20 degrees Celsius. The second material property may be electrical resistivity. The second region may have an electrical resistivity of electrical resistivity of 1x1 O'2Ohm-metres, Qm, or less, at a temperature of 20 degrees Celsius.

[0062] The second region may comprise a second material. The second material may have the second material property. The second region may comprise a solid body of the second material. The second material may be any suitable material.

[0063] In some embodiments, the second material is an electrically insulative material. The second material may be a dielectric material. The relative permittivity of the second material may be any suitable value. The second material may have a relative permittivity greater than 1. The relative permittivity of the second material may be 35 or less, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, 5 or less, or about 1 . The second material may be a ceramic material. The second material may be a polymeric material, such as polyether ketone (PEEK), Polyetherimide (PEI), polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyphthalamide (PPA), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polyimide (PI), PEEK-PFN Copolymers, and Eccostock variants like LoK, Flex-Lok, HIK500F. Preferably, the third material is able to tolerate high temperatures, such as temperatures in the range 150 degrees Celsius to 350 degrees Celsius, or in the range from 250 degrees Celsius to 350 degrees Celsius, and rapid temperature changes.

[0064] In some embodiments, the second region comprises a gas, such as air or any other suitable gas. The second region may comprise a space or volume comprising a gas, such as air. The second region may comprise a space or volume filled with a gas, such as air. A second region comprising a space or volume filled with a gas, such as air, is an electrically insulative region. A second region comprising a space or volume filled with a gas, such as air, is a dielectric second region. In some embodiments, the second material is an electrically conductive material. The third material may be any suitable electrically conductive material. For example, the third material may be a metal, such as copper, aluminium, stainless steel, silver, or gold.

[0065] The second region may have any suitable shape or size.

[0066] The second region may have a length, in a longitudinal direction. The length may be any suitable length. The second region may be elongate, having a length that is greater than the other dimensions of the second region.

[0067] The second region may have a width, in a transverse direction, perpendicular to the longitudinal direction.

[0068] The second region may have a transverse cross-sectional shape, perpendicular to the longitudinal direction. The transverse cross-sectional shape of the second region may be one of: circular, elliptical, stadium shaped, polygonal, rectangular, trapezoidal, pentagonal, or hexagonal.

[0069] In some preferred embodiments, the second region is substantially cylindrical. In some embodiments, the second region is a circular cylinder. In some preferred embodiments, the second region is substantially cuboidal. In some embodiments, the second region is a rectangular cuboid.

[0070] The second region may substantially circumscribe a portion of the chamber. The second region may be substantially annular. The second region may be substantially annular, having an inner passage defining a portion of the chamber. The second region may form an annular disc circumscribing a portion of the chamber. The second region may substantially circumscribe a portion of the chamber and extend radially outwards from the chamber. The second region may form a volume or a body that circumscribes the chamber and extends radially outwards from the chamber. The second region may extend radially outwards from the chamber into the first region.

[0071] In some embodiments, the first region is a dielectric region and the second region is a dielectric region. In some embodiments, the first region comprises a first material, wherein the first material is a dielectric material, and the second region comprises a second material, wherein the second material is a dielectric material.

[0072] In some preferred embodiments, a boundary of the second region is at a boundary of the chamber. In some preferred embodiments, a boundary of the second region defines a boundary, or a portion of a boundary, of the chamber. In some embodiments, a surface of the second region may define a surface, or a portion of a surface, of the chamber. In some embodiments, the second region intersects the chamber.

[0073] The second region may extend from the module housing to a boundary of the chamber. The second region may extend from the module housing. The second region may extend from a boundary of the chamber. Where the second region comprises a second material, the second material may extend from the module housing to a boundary of the chamber. The second material may extend from a boundary of the chamber. The second material may extend from the module housing. In some embodiments, the second material may extend from a boundary of the chamber part of the way to the module housing. In some embodiments, the second material may extend from the module housing part of the way to the boundary of the chamber. The second region may extend radially outwards from the chamber to the module housing. The second region may extend radially outwards from the chamber and not extend to the module housing. In particular, where the second material comprises an electrically conductive material, the second material may extend from the module housing. The second material may be in contact with the module housing. The second material may be electrically connected to the module housing.

[0074] Where the first material property is a first relative permittivity, and the second material property is a second relative permittivity, the second relative permittivity is less than the first relative permittivity. The second relative permittivity may be less than the first relative permittivity by any suitable amount. For example, the second relative permittivity may be less than the first relative material by at least 5, or by at least 6, or by at least 7, or by at least 8, or by at least 9, or by at least 10.

[0075] Advantageously, the greater the difference between the second relative permittivity and the first relative permittivity, the greater the effect of the localised intensification of the electric field in the chamber at or around the second region compared to the other regions of the chamber, and the greater the localised heating of an aerosol-forming substrate in the chamber at or around the second region compared to the other regions of the chamber.

[0076] Where the first material property is relative permittivity and the second material property is electrical conductivity, the first region may be a dielectric region and the second region may be an electrically conductive region. Where the first material property is relative permittivity and the second material property is electrical conductivity, the first region may comprise a dielectric material and the second region may comprise an electrically conductive material.

[0077] Where the first material property is relative permittivity and the second material property is electrical conductivity, the first region may be a dielectric region and the second region may be an electrically conductive region. Where the first material property is relative permittivity and the second material property is electrical conductivity, the first region may comprise a dielectric material and the second region may comprise an electrically conductive material.

[0078] Where the first material property is a first electrical conductivity, and the second material property is a second electrical conductivity, the first electrical conductivity may be less than the second electrical conductivity. The first region may be an electrically insulative region, and the second region may be an electrically conductive region. The first region may comprise an electrically insulative material, and the second region may comprise an electrically conductive material.

[0079] In some embodiments, the chamber housing comprises more than one first region. The chamber housing may comprise a plurality of first regions. The chamber housing may comprise any suitable number of first regions. For example, the chamber housing may comprise 1 , 2, 3, 4, or 5 first regions.

[0080] Where the chamber housing comprises more than one first region, each first region has the same first material property. Where the first region comprises a first material, and the chamber housing comprises more than one first region, each first region comprises the same first material.

[0081] In some embodiments, the chamber housing comprises more than one second region. The chamber housing may comprise a plurality of second regions. The chamber housing may comprise any suitable number of second regions. For example, the chamber housing may comprise 1 , 2, 3, 4, or 5 second regions.

[0082] Where the chamber housing comprises more than one second region, each second region has the same second material property. Where the second region comprises a second material, and the chamber housing comprises more than one second region, each second region comprises the same second material.

[0083] Where the chamber housing comprises two first regions, the two first regions may be separated by the second region.

[0084] Where the chamber housing comprises more than two first regions, neighbouring first regions may be separated by one or more other regions. In some embodiments, the chamber housing comprises a plurality of first regions and a plurality of second regions, and neighbouring first regions may be separated by one of the plurality of second regions.

[0085] Where the chamber housing comprises two second regions, the two second regions may be separated by the first region.

[0086] Where the chamber housing comprises more than two second regions, neighbouring second regions may be separated by one or more other regions. In some embodiments, the chamber housing comprises a plurality of second regions and a plurality of first regions, and neighbouring second regions may be separated by one of the plurality of first regions.

[0087] In some embodiments, the position of the first region is fixed in the chamber housing. In some embodiments, the position of the second region is fixed in the chamber housing. In some embodiments, where the first region comprises a first material, and where the second region comprises a second material, the second material is embedded in the first material. In some embodiments, where the first region comprises a first material, and where the second region comprises a space or volume filled with a gas, such as air, the second region may comprise a notch or cut-out in the first material.

[0088] In some embodiments, the position of the first region is not fixed in the chamber housing. In some embodiments, the position of the second region is not fixed in the chamber housing.

[0089] Advantageously, enabling the first region of the chamber housing to move relative to other regions of the chamber housing may enable a user to vary the location of localised alternating electric field enhancement in the chamber. In other words, enabling the first region of the chamber housing to move relative to other regions of the chamber housing may enable a user to vary the location of localised aerosol-forming substrate heating enhancement in the chamber. This may enable a user to vary the aerosol generation experience during use of the aerosol-generating system. This may also enable a user to optimise the configuration of the heater module for use with different aerosolgenerating articles.

[0090] Where the position of the first region is not fixed in the chamber housing, the first region may be configured to be moved in any suitable direction. Preferably, the first region may be configured to move in a longitudinal direction of the chamber housing. In other words, the first region may be configured to move along the length of the chamber housing. The first region may be configured to move by translation. The first region may be configured to move by rotation.

[0091] The first region may be configured to move from a first position to a second position. The first region may be configured to move from the first position to the second position in any suitable manner. The first region may be configured to slide from the first position to the second position. The first region may be configured to rotate from the first position to the second position.

[0092] Where the position of the first region is not fixed in the chamber housing, typically the second region comprises a space or volume filled with a gas, such as air. Accordingly, the first region may be able to move into the second region. When the first region moves into the second region, two second regions may be formed, one either side of the first region, wherein both of the two second regions comprise a space or volume filled with a gas, such as air. When the first regions is moved completely into the original location of the second region, a solitary second region may be formed again, in the original location of the first region. The chamber housing may comprise a plurality of first regions and a plurality of second regions, and one or more of the plurality of first regions may be configured to move into one or more of the plurality of second regions.

[0093] The heater module may comprise an actuator. The actuator may be configured to move the position of the first region of the chamber housing relative to other regions of the chamber housing.

[0094] The actuator may be any suitable actuator. For example, the actuator may be a button, a slider, or a screw thread. The actuator may include a passive actuator, an active actuator, or a combination of both.

[0095] The actuator may be configured to move the first region from a first position to a second position by sliding the actuator. The actuator may be configured to move the first region from a first position to a second position by sliding the actuator in a longitudinal direction of the chamber housing. The actuator may be configured to move the first region from a first position to a second position by pressing the actuator. The actuator may be configured to move the first region from a first position to a second position by pressing the actuator in a direction substantially perpendicular to the longitudinal direction of the chamber housing. The actuator may be configured to move the first region from a first position to a second position by rotating the actuator. The actuator may be configured to move the first region from a first position to a second position by rotating the actuator about the longitudinal axis of the chamber housing.

[0096] In some embodiments, the chamber housing comprises one or more additional regions, such as a third region. The one or more additional regions may comprise additional material properties that are different from the material properties of the first region and the second region. For example, the chamber housing may comprise a third region comprising a third material property. The third material property may be different from the first material property and the second material property. The first material property, the second material property, and the third material property may be such that an electric field in the chamber and chamber housing is greater at and around the second region of the chamber housing compared to the electric field in the chamber and chamber housing at and around the first region of the chamber housing, and the electric field is greater at and around the third region of the chamber housing compared to the electric field in the chamber and chamber housing at and around the first region of the chamber housing.

[0097] Advantageously, forming the chamber housing from a plurality of regions having different material properties may enable greater variation, and more precise variations, in the local intensity of an alternating electric field created in the chamber and chamber housing to be achieved.

[0098] The third material property may be relative permittivity. The relative permittivity of the third region may be greater than 1. The third region may be a dielectric region. The relative permittivity of the third region may be any suitable value. For example, the relative permittivity of the third region may be 35 or less, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, 5 or less, or about 1 .

[0099] The third material property may be electrical conductivity. The third region may be an electrically conductive region. The third region may have an electrical conductivity of 1x102Siemens per metre (S / m), or more, at a temperature of 20 degrees Celsius. The third material property may be electrical resistivity. The third region may have an electrical resistivity of electrical resistivity of 1x10-2Ohm-metres, Qm, or less, at a temperature of 20 degrees Celsius.

[0100] The third region may comprise a third material having the third material property. The third region may comprise a solid body of the third material. The third material may be any suitable material.

[0101] In some embodiments, the third material is an electrically insulative material. The third material may be a dielectric material. The relative permittivity of the third material may be any suitable value. The third material may have a relative permittivity greater than 1. The relative permittivity of the third material may be 35 or less, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, 5 or less, or about 1 . The third material may be a ceramic material. The third material may be a polymeric material, such as polyether ketone (PEEK), Polyetherimide (PEI), polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyphthalamide (PPA), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polyimide (PI), PEEK-PFN Copolymers, and Eccostock™ variants like LoK, Flex-Lok, HIK500F. Preferably, the third material is able to tolerate high temperatures, such as temperatures in the range 150 degrees Celsius to 350 degrees Celsius, or in the range from 250 degrees Celsius to 350 degrees Celsius, and rapid temperature changes.

[0102] In some embodiments, the third region comprises a gas, such as air or any other suitable gas. The third region may comprise a space or volume comprising a gas, such as air. The third region may comprise a space or volume filled with a gas, such as air. A third region comprising a space or volume filled with a gas, such as air, is an electrically insulative region. A third region comprising a space or volume filled with a gas, such as air, is a dielectric third region.

[0103] In some embodiments, the third material is an electrically conductive material. The third material may be any suitable electrically conductive material. For example, the third material may be a metal, such as copper, aluminium, stainless steel, silver, or gold.

[0104] The third region may have any suitable shape or size.

[0105] The third region may have a length, in a longitudinal direction. The length may be any suitable length. The third region may be elongate, having a length that is greater than the other dimensions of the third region.

[0106] The third region may have a width, in a transverse direction, perpendicular to the longitudinal direction.

[0107] The third region may have a transverse cross-sectional shape, perpendicular to the longitudinal direction. The transverse cross-sectional shape of the third region may be one of: circular, elliptical, stadium shaped, polygonal, rectangular, trapezoidal, pentagonal, or hexagonal.

[0108] In some preferred embodiments, the third region is substantially cylindrical. In some embodiments, the third region is a circular cylinder. In some preferred embodiments, the third region is substantially cuboidal. In some embodiments, the third region is a rectangular cuboid.

[0109] The third region may substantially circumscribe a portion of the chamber. The third region may be substantially annular. The third region may be substantially annular, having an inner passage defining a portion of the chamber.

[0110] In some embodiments, the first region is a dielectric region and the third region is a dielectric region. In some embodiments, the first region comprises a first material, wherein the first material is a dielectric material, and the third region comprises a third material, wherein the third material is a dielectric material.

[0111] In some preferred embodiments, a boundary of the third region is at a boundary of the chamber. In some preferred embodiments, a boundary of the third region defines a boundary, or a portion of a boundary, of the chamber. In some embodiments, a surface of the third region may define a surface, or a portion of a surface, of the chamber. In some embodiments, the third region intersects the chamber.

[0112] The third region may extend from the module housing to a boundary of the chamber. The third region may extend from the module housing. The third region may extend from a boundary of the chamber. Where the third region comprises a third material, the third material may extend from the module housing to a boundary of the chamber. The third material may extend from a boundary of the chamber. The third material may extend from the module housing. In some embodiments, the third material may extend from a boundary of the chamber part of the way to the module housing. In some embodiments, the third material may extend from the module housing part of the way to the boundary of the chamber. In particular, where the third material comprises an electrically conductive material, the third material may extend from the module housing. The third material may be in contact with the module housing. The third material may be electrically connected to the module housing.

[0113] Where the first material property is a first relative permittivity, and the third material property is a third relative permittivity, the third relative permittivity is less than the first relative permittivity. The third relative permittivity may be less than the first relative permittivity by any suitable amount. For example, the third relative permittivity may be less than the first relative material by at least 5, or by at least 6, or by at least 7, or by at least 8, or by at least 9, or by at least 10.

[0114] Where the first material property is relative permittivity and the third material property is electrical conductivity, the first region may be a dielectric region and the third region may be an electrically conductive region. Where the first material property is relative permittivity and the third material property is electrical conductivity, the first region may comprise a dielectric material and the third region may comprise an electrically conductive material.

[0115] Where the first material property is relative permittivity and the third material property is electrical conductivity, the first region may be a dielectric region and the third region may be an electrically conductive region. Where the first material property is relative permittivity and the third material property is electrical conductivity, the first region may comprise a dielectric material and the third region may comprise an electrically conductive material.

[0116] Where the first material property is a first electrical conductivity, and the third material property is a third electrical conductivity, the first electrical conductivity may be less than the third electrical conductivity. The first region may be an electrically insulative region, and the third region may be an electrically conductive region. The first region may comprise an electrically insulative material, and the third region may comprise an electrically conductive material.

[0117] The third material property may be different from the second material property. The third material property may be different from the second material property such that am electric field in the chamber and chamber housing is different at and around the third region of the chamber housing compared to the electric field in the chamber and chamber housing at and around the second region of the chamber housing.

[0118] The heater module may be coupled to an alternating electric field generator. The heater module may be coupled to an alternating electric field generator for creating an alternating electric field in the chamber. Preferably, the heater module comprises at least one coupler. The at least one coupler may be configured to couple an alternating electric field generator to the chamber for creating an alternating electric field in the chamber.

[0119] The at least one coupler may be configured to introduce an alternating electric field into the chamber housing and the chamber. Where the heater module comprises a module housing, and wherein the module housing, chamber housing, and chamber form a cavity resonator, the at least one coupler may be configured to introduce an alternating electric field into the cavity resonator.

[0120] The at least one coupler may be coupled to an alternating electric field generator and positioned in or adjacent to the resonant cavity so as to introduce an alternating electric field generated by the alternating electric field generator into the chamber. By way of example and without limitation, the at least one coupler may include at least one of: a capacitive pin coupler; an inductive loop coupler; a wave guide; a microstrip; and a stripline.

[0121] Where the heater module comprise a cavity resonator, the positioning of the at least one coupler in the heater module may influence which resonant mode of the cavity resonator is excite when the alternating electric field is introduced into the cavity resonator. The type and position of coupler employed will influence the electric and magnetic field lines created in the resonant cavity by the electromagnetic waves introduced into the cavity by the respective coupler.

[0122] Preferably, the heater module comprises a module housing. The module housing may substantially circumscribe the chamber housing.

[0123] Particularly preferably, the module housing is configured to be substantially opaque to the alternating electric field created within the module. Accordingly, the module housing may act as a faraday cage around the module housing. The module housing may define the boundary of the cavity resonator.

[0124] The module housing may comprise any suitable material. The module housing may comprise a material that is opaque to RF electromagnetic radiation. The module housing may comprise a material that is not transparent to RF electromagnetic radiation. The module housing may comprise an electrically conductive material. For example, the module housing may comprise a metal, such a copper, aluminium, stainless steel, silver or gold. The module housing may comprise a sheet or a mesh.

[0125] An interior-facing surface of the module housing may have a polished surface. A polished interiorfacing surface of the module housing may improve reflection of the alternating electric field within the chamber housing and chamber. Advantageously, such reflection may improve efficiency of heating of an aerosol-forming substrate positioned within the cavity.

[0126] Materials for the module housing are preferably chosen to reflect RF electromagnetic radiation internally within the interior of the chamber housing and the chamber, thereby helping to strengthen the coupling of the alternating electric field created in the module with an aerosol-forming substrate received in the chamber. Where the module housing is configured to be substantially opaque to RF electromagnetic radiation, the module housing may further comprise one or more holes, slots, or portions which are otherwise substantially transparent to RF electromagnetic radiation, to allow for the introduction of the alternating electric field in the chamber housing and the chamber. For example, where one or more couplers are used to introduce the alternating electric field into the chamber housing and chamber, each coupler may be positioned in or through holes, slots or RF transparent portions of the module housing.

[0127] According to the disclosure, there is also provided an aerosol-generating device comprising the heater module as described above.

[0128] The aerosol-generating device may comprise an alternating electric field generator. The alternating electric field generator may be coupled to the heater module. The alternating electric field generator may be configured to create an alternating electric field in the heater module.

[0129] The alternating electric field generator may be coupled to the heater module by at least one coupler. The alternating electric field generator may be coupled to the heater module by at least one coupler of the heater module. The alternating electric field generator may be coupled to the heater module by a plurality of couplers. The alternating electric field generator may be any suitable generator. In some embodiments, the alternating electric field generator may be a voltage-controlled oscillator (VCO). In some embodiments, the alternating electric field generator may be a synthesizer.

[0130] The alternating electric field generator may comprise one or more solid state RF components. Preferably, the alternating electric field generator comprises a solid state RF transistor. The solid state RF transistor may be part of a VCO. The solid state RF transistor may be part of a synthesizer.

[0131] The use of a solid state RF transistor, and other solid state RF components, may allow the aerosolgenerating device to be compact, thereby assisting in the device being handheld or portable. The conventional means for producing RF frequency radiation for heating, such as in domestic microwave ovens, is a magnetron. Magnetrons are bulky and require high voltages to operate. Furthermore, magnetrons have a relatively unstable frequency output and have a relatively short service life. A RF transistor can provide for consistent operation over many more usage cycles and requires much lower operating voltages.

[0132] Advantageously, one or more solid state RF transistors may be configured to generate and amplify the alternating electric field. Using a single transistor to provide both the generating and amplification of the alternating electric field allows for the aerosol-generating device to be compact. The solid state RF transistor may be, for example, a LDMOS transistor, a GaAs FET, a SiC MESFET or a GaN HFET.

[0133] Although it is preferable that the alternating electric field generator comprises a solid state RF transistor, it is envisaged that in some embodiments the alternating electric field generator may comprise a magnetron or other suitable signal source capable of generating an alternating electric field.

[0134] The alternating electric field created in the chamber may have any suitable frequency for dielectrically heating an aerosol-forming substrate in an aerosol-generating article received in the chamber. The alternating electric field may be a radio frequency, RF, electric field. As used herein, radio frequency, RF, means a frequency between 50 MHz and 300 Gigahertz. Accordingly, as used herein, RF frequencies include microwave frequencies and ultra-high frequencies, UHF. The alternating electric field may have a frequency of between 50 MHz and 300 Gigahertz, optionally a frequency of between 200 Megahertz and 50 Gigahertz, optionally a frequency of between 300 Megahertz and 30 Gigahertz, optionally a frequency of between 500 Megahertz and 20 Gigahertz, or a frequency of about 2.45 GHz.

[0135] Where the aerosol-generating device comprises an alternating electric field generator, the alternating electric field generator may be configured to generate an alternating electric field having any suitable frequency for dielectrically heating an aerosol-forming substrate in an aerosol-generating article received in the chamber. The alternating electric field may be a radio frequency, RF, electric field. As used herein, radio frequency, RF, means a frequency between 50 MHz and 300 Gigahertz. Accordingly, as used herein, RF frequencies include microwave frequencies and ultra-high frequencies, UHF. The alternating electric field may have a frequency of between 50 MHz and 300 Gigahertz, optionally a frequency of between 200 Megahertz and 50 Gigahertz, optionally a frequency of between 300 Megahertz and 30 Gigahertz, optionally a frequency of between 500 Megahertz and 20 Gigahertz, or a frequency of about 2.45 GHz.

[0136] The aerosol-generating device may comprise control electronics. The control electronics may comprise a microprocessor, which may be a programmable microprocessor, a microcontroller, or an application specific integrated chip (ASIC) or other electronic circuitry capable of providing control. The control electronics may comprise further electronic components. For example, the control electronics may comprise any of: sensors, switches, and display elements. The control electronics may advantageously comprise DC / AC inverter, which may comprise a Class-D, or Class-E, or Class-F power amplifier, or any other suitable amplifier.

[0137] The control electronics may be configured to control a supply of power to the heater module. The control electronics may be configured to regulate a supply of power to the heater module. Power may be supplied to the heater module continuously following activation of the aerosol-generating device or may be supplied intermittently, such as on a puff by puff basis.

[0138] In some embodiments, the control electronics are coupled to the alternating electric field generator. Preferably, the control electronics comprise the alternating electric field generator.

[0139] The control electronics may comprise a memory. The memory may contain instructions readable by a processor or other component parts of the control electronics, wherein the instructions are used to control operation of the aerosol-generating device. The instructions may be used to control operation of the alternating electric field generator.

[0140] In some preferred embodiments, the aerosol-generating device further comprises a power supply. The power supply may be a DC power supply. The power supply may comprise at least one of a battery and a capacitor. In one embodiment, the power supply is a DC power supply having a DC supply voltage in the range of about 2.5 Volts to about 4.5 Volts and a DC supply current in the range of about 0.1 Amp to about 10 Amps (corresponding to a DC power supply in the range of about 0.5 Watts to about 45 Watts).

[0141] The control electronics may be configured to control the aerosol-generating device. The control electronics may be configured to control the aerosol-generating device by controlling the supply of power from the power supply to the heater module.

[0142] The control electronics may comprise a power sensing system configured to detect a power consumption value drawn from the power supply. The power consumption value may be indicative of a supply current, in particular a DC supply current, drawn from the power supply. The power sensing system may comprise a shunt to derive the supply current. The control electronics may be configured to control the frequency of the electric field created in the chamber. The control electronics may comprise a power sensor. The control electronics may comprise a power amplifier.

[0143] Where the heater module comprises a cavity resonator, the control electronics may be configured to control the alternating electric field generator to selectively excite different predetermined electric modes of the cavity resonator. Selective excitation of different predetermined electromagnetic modes of the resonant cavity may allow for generating a radiation field within the resonant cavity which can be changed in intensity, shape and / or position over time, thereby resulting in a corresponding change in the heating regime resulting from the radiation field for an aerosol-forming substrate received in the cavity.

[0144] For example, different ones or combinations of the predetermined electromagnetic modes may be excited at different points over a usage session of the aerosol-generating device. These different points may be associated with corresponding points in a target temperature profile for the usage session. The target temperature profile may be for an aerosol-forming substrate received in the resonant cavity when exposed to the radiation field generated within the cavity.

[0145] The predetermined electromagnetic modes may comprise a first electromagnetic mode and a second electromagnetic mode.

[0146] Preferably, the control electronics are configured to control the alternating electric field generator to switch between generating the RF electromagnetic wave at a first predetermined frequency and generating the RF electromagnetic wave at a second predetermined frequency. The first predetermined frequency is different from the second predetermined frequency. The first and second predetermined frequencies may be associated with excitation of respective first and second ones of the predetermined electromagnetic modes. The first predetermined frequency may be a first resonant frequency associated with the first predetermined electromagnetic mode. The second predetermined frequency may be a second resonant frequency associated with the second predetermined electromagnetic mode.

[0147] The first and second electromagnetic modes may have a common resonant frequency. The alternating electric field generator is preferably configured to generate the alternating electric field at the common resonant frequency. A condition in which the first and second electromagnetic modes have a common resonant frequency is referred to as a condition of “mode degeneracy”. Having the first and second electromagnetic modes possessing the same resonant frequency avoids the need to change the frequency output of the alternating electric field generator in order to activate different ones of the first and second electromagnetic modes. Another advantage of the first and second electromagnetic modes sharing a common resonant frequency is that it may allow for the simultaneous excitation of the first and second electromagnetic modes using an RF electromagnetic wave generated by the alternating electric field generator at that common resonant frequency. For example, the aerosol-generating device may comprise a first coupler disposed at a first location within the cavity resonator and a second coupler disposed at a second location within the cavity resonator, the first coupler configured to excite the first electromagnetic mode and the second coupler configured to excite the second electromagnetic mode when each supplied with the RF electromagnetic wave at the common resonant frequency. By way of example, simultaneous excitation of the first and second electromagnetic modes may be associated with an enhanced or boost level heating mode for the aerosol-generating device.

[0148] Advantageously, providing the heater module with a cavity resonator including a chamber housing having a plurality of different regions, having different material properties, and configuring the control electronics to control the alternating electric field generator to selectively excite different predetermined electric modes of the cavity resonator may provide improved adaptability of the aerosolgenerating device, and improved customisability of the aerosol generating experience provided by the aerosol-generating device. Such a combination of features shapes the alternating electric field created in the heater module both through the physical structure of the heater module and through the configuration of the control electronics and alternating electric field generator. As such the shape of the alternating electric field created in the heater module may be optimised and changed throughout an aerosol generating experience to precisely control aerosol generation. For example, it may be desirable to rapidly heat a distal end of an aerosol-generating article during a pre-heating phase when the aerosol-generating device is first turned on, in order to generate aerosol quickly and reduce the time to first puff on the aerosol-generating device for a user, and subsequently to reduce the temperature of the distal end of the aerosol-generating article compared to other regions of the aerosol-generating article in an aerosol generation phase, after the pre-heating phase, once the aerosol-forming substrate at the distal end is depleted. This may be achieved by changing the mode excited in the cavity resonator between the pre-heating phase and the subsequent aerosol generation phase.

[0149] According to the disclosure, there is also provided an aerosol-generating system comprising: an aerosol-generating device comprising the heater module as described above. The aerosol-generating system may further comprise an aerosol-generating article comprising an aerosol-forming substrate.

[0150] The aerosol-generating article comprises an aerosol-forming substrate.

[0151] The aerosol-forming substrate may form one of a plurality of component parts of an aerosolgenerating article, with the aerosol-generating article being removably receivable in the chamber of the heater module. In some embodiments, the aerosol-forming substrate alone may form the aerosolgenerating article.

[0152] The aerosol-forming substrate may take any suitable form. Preferably, the aerosol-forming substrate is a solid aerosol-forming substrate. However, the aerosol-forming substrate may comprise both solid and liquid components. Alternatively, the aerosol-forming substrate may be a liquid aerosolforming substrate. The aerosol-forming substrate may comprise a solid. The aerosol-forming substrate may comprise a liquid. The aerosol-forming substrate may comprise a gel.

[0153] Where the aerosol-forming substrate comprises a liquid or a gel, the liquid may be located inside a container, or cartridge, or porous body, that can be at least partially received in the chamber of the heater module. The aerosol-forming substrate may comprise any combination of two or more of a solid, a liquid and a gel.

[0154] Preferably, the aerosol-forming substrate comprises polar molecules which are susceptible to dipole interaction for dielectric heating, such as under the action of the alternating electric field in the chamber of the heater module. By way of example, the aerosol-forming substrate may include water, with water being particularly susceptible to dielectric heating. The aerosol-forming substrate may be provided in solid form, but having been soaked in water or another liquid containing polar molecules. In this manner, the alternating electric field acts to excite the polar molecules of the water or other liquid, thereby generating heat, with the heat then being imparted to the material of the aerosol-forming substrate.

[0155] Preferably, the aerosol-forming substrate comprises nicotine, a nicotine derivative or a nicotine analogue. The aerosol-forming substrate may comprise one or more nicotine salts. The one or more nicotine salts may be selected from the list consisting of nicotine citrate, nicotine lactate, nicotine pyruvate, nicotine bitartrate, nicotine pectates, nicotine aginates, and nicotine salicylate.

[0156] More preferably, the aerosol-forming substrate comprises tobacco. Alternatively or in addition, the aerosol-forming substrate may comprise a non-tobacco material or tobacco-substitute material containing aerosol-forming material.

[0157] If the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosol-forming substrate may comprise, for example, one or more of: powder, granules, pellets, shreds, strands, strips, or sheets containing one or more of: herb leaf, tobacco leaf, tobacco ribs, expanded tobacco and homogenised tobacco.

[0158] Optionally, the solid aerosol-forming substrate may contain tobacco or non-tobacco volatile flavour compounds, which are released upon heating of the solid aerosol-forming substrate. The solid aerosol-forming substrate may also contain one or more capsules that, for example, include additional tobacco volatile flavour compounds or non-tobacco volatile flavour compounds and such capsules may melt during heating of the solid aerosol-forming substrate. In a preferred embodiment, the aerosol-forming substrate comprises homogenised tobacco material. As used herein, the term “homogenised tobacco material” refers to a material formed by agglomerating particulate tobacco.

[0159] Preferably, the aerosol-forming substrate comprises a gathered sheet of homogenised tobacco material. As used herein, the term “sheet” refers to a laminar element having a width and length substantially greater than the thickness thereof. As used herein, the term “gathered” is used to describe a sheet that is convoluted, folded, or otherwise compressed or constricted substantially transversely to the longitudinal axis of the aerosol-generating article.

[0160] The aerosol-forming substrate may comprise one or more botanicals, and / or one or more pharmaceutical agents.

[0161] In cases where the aerosol-forming substrate comprises a liquid or a gel, in some embodiments, the aerosol-generating article may comprise an absorbent carrier. The aerosol-forming substrate may be coated on or impregnated into the absorbent carrier. For example, the nicotine compound and the aerosol-former may be combined with water as a liquid formulation. The liquid formulation may, in some embodiments, further comprise a flavourant. Such a liquid formulation may then be absorbed by the absorbent carrier or coated onto the surface of the absorbent carrier. The absorbent carrier may be a sheet or tablet of cellulosic-based material onto which the nicotine compound and the aerosol former may be coated or absorbed. The absorbent carrier may be a metallic, polymer or vegetal foam having liquid retaining and capillary properties and onto which the liquid or gel aerosol-forming substrate is coated or absorbed.

[0162] The aerosol-forming substrate may comprise an aerosol former. As used herein, an “aerosol former” refers to any suitable known compound or mixture of compounds that, in use, facilitates formation of a dense and stable aerosol and that is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article. Suitable aerosol-formers are well known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, 1 ,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol formers are polyhydric alcohols or mixtures thereof, such as triethylene glycol, 1 ,3-butanediol and glycerine.

[0163] The aerosol-forming substrate may comprise a single aerosol former. Alternatively, the aerosolforming substrate may comprise a combination of two or more aerosol formers.

[0164] It is to be appreciated that the features of the above examples of the disclosure are complementary with one another, except where stated otherwise, and so features of different examples may be readily implemented in the oscillation circuits of other examples. Further optional examples of the disclosure are set out below. 1 . A heater module for an aerosol-generating device configured to dielectrically heat an aerosolgenerating article, the heater module comprising: a chamber configured to receive at least a portion of an aerosol-generating article to be heated; and a chamber housing, the chamber being disposed within a chamber housing, wherein the chamber housing comprises: a first region having a first material property; and a second region having a second material property, wherein the first material property and the second material property are such that an electric field created in the chamber and chamber housing is greater in the chamber at the second region of the chamber housing compared to the electric field in the chamber at the first region of the chamber housing.

[0165] 2. A heater module according to example 1 , wherein the first material property is relative permittivity, and the first region is a dielectric region having a first relative permittivity, and wherein the second material property is relative permittivity, and the second region is a dielectric region having a second relative permittivity, the second relative permittivity being less than the first relative permittivity.

[0166] 3. A heater module for an aerosol-generating device configured to dielectrically heat an aerosolgenerating article, the heater module comprising: a chamber housing defining a chamber configured to receive at least a portion of an aerosolgenerating article to be heated, wherein the chamber housing comprises: a first region, the first region being a dielectric region having a first relative permittivity; and a second region, the second region being a dielectric region having a second relative permittivity, wherein the second relative permittivity is less than the first relative permittivity.

[0167] 4. A heater module according to example 2 or example 3, wherein the first relative permittivity is greater than 1 , and optionally wherein the first relative permittivity is at least 10, or at least 15, or at least 20, or at least 25, or at least 30, or between 10 and 110, or between 20 and 100, or between 20 and 90, or between 20 and 80, or between 20 and 70 or between 30 and 40, or around 34.

[0168] 5. A heater module according to any one of examples 2 to 4, wherein the first dielectric region comprises a first dielectric material having the first relative permittivity, and optionally wherein the first dielectric material comprises at least one of: a ceramic material; a polymeric material; alumina, MgNb2C>6, ZnNb2C>6, MgTa2Oe, ZnTa2Oe, and glass.

[0169] 6. A heater module according to any one of examples 2 to 5, wherein the first relative permittivity is greater than the second relative permittivity by at least 5, or by at least 10. 7. A heater module according to any one of examples 2 to 6, wherein the second dielectric region comprises a space or volume comprising a gas, such as air, and optionally wherein the space or volume is filled with the gas.

[0170] 8. A heater module according to any one of examples 2 to 6, wherein the second region comprises a second dielectric material, and optionally wherein the second dielectric material is a ceramic material or a polymeric material, such as polyether ketone (PEEK).

[0171] 9. A heater module according to example 1 , wherein the first material property is electrical conductivity, and the first region is a dielectric region having a first electrical conductivity; and wherein the second material property is electrical conductivity, and the second region is an electrically conductive region having an electrical conductivity greater than the electrical conductivity of the first region.

[0172] 10. A heater module for an aerosol-generating device configured to dielectrically heat an aerosolgenerating article, the heater module comprising: a chamber housing defining a chamber configured to receive at least a portion of the aerosolgenerating article to be heated, wherein the chamber housing comprises: a first region, the first region being a dielectric region having a first relative permittivity; and a second region, the second region being an electrically conductive region having an electrical conductivity greater than the electrical conductivity of the first region.

[0173] 11. A heater module according to example 9 or example 10, wherein the first region has an electrical conductivity of 1x1 O'4Siemens per metre (S / m), or less, at a temperature of 20 degrees Celsius.

[0174] 12. A heater module according to any one of examples 9 to 11 , wherein the first dielectric region comprises a first dielectric material having the first relative permittivity, and optionally wherein the first dielectric material comprises at least one of: a ceramic material; a polymeric material; alumina, MgNb2C>6, ZnNb2C>6, MgTa2Oe, ZnTa2Oe, and glass.

[0175] 13. A heater module according to any one of examples 9 to 12, wherein the second region has an electrical conductivity of 1x102Siemens per metre (S / m), or more, at a temperature of 20 degrees Celsius.

[0176] 14. A heater module according to any one of examples 9 to 13, wherein the second region comprises an electrically conductive material, and optionally wherein the electrically conductive material is a metal, such as copper, stainless steel, aluminium, silver, or gold.

[0177] 15. A heater module according to any one of examples 1 to 14, wherein the chamber housing comprises a plurality of first regions.

[0178] 16. A heater module according to any one of examples 1 to 15, wherein the chamber housing comprises a plurality of second regions. 17. A heater module according to any one of examples 1 to 16, wherein the position of the first region is not fixed in the chamber housing, and optionally wherein the first region is configured to move from a first position to a second position.

[0179] 18. A heater module according to example 17, wherein the module further comprises an actuator configured to move the position of the first region of the chamber housing.

[0180] 19. A heater module according to any one of examples 1 to 18, wherein a boundary of the second region is at a boundary of the chamber, and optionally wherein a surface of the second region defines a portion of a surface of the chamber.

[0181] 20. A heater module according to any one of examples 1 to 19, wherein the first region circumscribes the chamber, and optionally the first region forms an annular disc circumscribing a portion of the chamber.

[0182] 21 . A heater module according to any one of examples 1 to 20, wherein the second region circumscribes the chamber, and optionally the second region forms an annular disc circumscribing a portion of the chamber.

[0183] 22. A heater module according to any one of examples 1 to 21 , wherein the chamber housing comprises a third region comprising a third material property, and optionally wherein the first material property, the second material property, and the third material property are such that an electric field in the chamber and chamber housing is greater at and around the second region of the chamber housing compared to the electric field in the chamber and chamber housing at and around the first region of the chamber housing, and the electric field is greater at and around the third region of the chamber housing compared to the electric field in the chamber and chamber housing at and around the first region of the chamber housing.

[0184] 23. A heater module according to any one of examples 1 to 22, wherein the heater module comprises a coupler configured to couple an alternating electric field generator to the chamber for causing an alternating electric field in the chamber.

[0185] 24. A heater module according to any one of examples 1 to 23, wherein the heater module comprises a module housing, wherein the module housing substantially circumscribes the chamber housing, and wherein the module housing comprises an electrically conductive material.

[0186] 25. An aerosol-generating device configured to dielectrically heat an aerosol-generating article, the aerosol-generating device comprising a heater module according to any one of examples 1 to 24.

[0187] 26. An aerosol-generating device according to example 25, wherein the aerosol-generating device comprises an alternating electric field generator coupled to the heater module and configured to create an alternating electric field in the heater module.

[0188] 27. An aerosol-generating device according to example 26, wherein the heater module comprises a cavity resonator, the chamber and chamber housing being disposed in the cavity resonator, and wherein the aerosol-generating device comprises control electronics configured to control the alternating electric field generator to selectively excite different predetermined electric modes of the cavity resonator.

[0189] 28. An aerosol-generating system comprising an aerosol-generating device according to any one of examples 25 to 27, and an aerosol-generating article comprising an aerosol-forming substrate.

[0190] 29. An aerosol-generating system according to example 28, wherein the second region of the chamber housing of the heater module of the aerosol-generating device circumscribes a portion of the aerosol-forming substrate when the aerosol-generating article is received in the chamber of the heater module.

[0191] The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

[0192] Figure 1 is a schematic illustration of a known heater module for an aerosol-generating device configured to dielectrically heat an aerosol-generating article;

[0193] Figure 2 is a schematic illustration of an exemplary aerosol-generating article for use in an aerosolgenerating device configured to dielectrically heat an aerosol-generating article, such as the aerosolgenerating device of Figure 1 ;

[0194] Figure 3 is a schematic illustration of a known aerosol-generating system comprising the aerosolgenerating device of Figure 1 and the aerosol-generating article of Figure 2, with the aerosol-generating article received in the chamber of the heater module;

[0195] Figure 4 is a schematic illustration of a heater module according to an example of the present disclosure, wherein the heater module is for an aerosol-generating device configured to dielectrically heat an aerosol-generating article;

[0196] Figure 5 is a schematic illustration of the heater module of Figure 4 in use with the aerosolgenerating article of Figure 2;

[0197] Figure 6 is a schematic illustration of an aerosol-generating system according to an embodiment of the disclosure, the aerosol-generating system comprising an aerosol-generating device including the heater module of Figure 4, and the aerosol-generating article of Figure 2;

[0198] Figure 7 is a schematic illustration of a heater module according to an example of the present disclosure, wherein the heater module is for an aerosol-generating device configured to dielectrically heat an aerosol-generating article, wherein the heater module comprises a movable first region in a first position, and wherein the heater module is in use with the aerosol-generating article of Figure 2;

[0199] Figure 8 is a schematic illustration of the heater module of Figure 7, with the movable first region moved into a second position;

[0200] Figure 9 is a schematic illustration of a heater module according to an example of the present disclosure, wherein the heater module is for an aerosol-generating device configured to dielectrically heat an aerosol-generating article, wherein the heater module comprises a movable first region in a first position, and wherein the heater module is in use with the aerosol-generating article of Figure 2; Figure 10 is a schematic illustration of the heater module of Figure 9, with the movable first region moved into an intermediate position;

[0201] Figure 11 is a schematic illustration of the heater module of Figure 9, with the movable first region moved into a second position;

[0202] Figure 12 is a schematic illustration of a heater module according to an example of the present disclosure, wherein the heater module is for an aerosol-generating device configured to dielectrically heat an aerosol-generating article;

[0203] Figure 13 is a schematic illustration of the heater module of Figure 12 in use with the aerosolgenerating article of Figure 2;

[0204] Figure 14 is a schematic illustration of a heater module according to a further example of the present disclosure, wherein the heater module is for an aerosol-generating device configured to dielectrically heat an aerosol-generating article, and wherein the heater module is in use with the aerosolgenerating article of Figure 2;

[0205] Figure 15 is a schematic illustration of a heater module according to a further example of the present disclosure, wherein the heater module is for an aerosol-generating device configured to dielectrically heat an aerosol-generating article, and wherein the heater module is in use with the aerosolgenerating article of Figure 2;

[0206] Figure 16 is a schematic illustration of a heater module according to a further example of the present disclosure, wherein the heater module is for an aerosol-generating device configured to dielectrically heat an aerosol-generating article, and wherein the heater module is in use with the aerosolgenerating article of Figure 2;

[0207] Figure 17 is a schematic illustration of a heater module according to a further example of the present disclosure, wherein the heater module is for an aerosol-generating device configured to dielectrically heat an aerosol-generating article, and wherein the heater module is in use with the aerosolgenerating article of Figure 2;

[0208] Figure 18 is a schematic illustration of a heater module according to a further example of the present disclosure, wherein the heater module is for an aerosol-generating device configured to dielectrically heat an aerosol-generating article, and wherein the heater module is in use with the aerosolgenerating article of Figure 2;

[0209] Figure 19 is a schematic illustration of a heater module according to a further example of the present disclosure, wherein the heater module is for an aerosol-generating device configured to dielectrically heat an aerosol-generating article, and wherein the heater module is in use with the aerosolgenerating article of Figure 2.

[0210] Figure 1 shows a heater module 1 for a known aerosol-generating device. The heater module 1 is configured for dielectric heating of an aerosol-generating article. The heater module 1 comprises a chamber 2 that is configured to receive an aerosol-generating article. The chamber 2 is substantially circularly cylindrical, and configured to receive an aerosolgenerating article in the form of a circularly cylindrical rod, such as a rod having similar dimensions to that of a conventional cigarette.

[0211] The heater module 1 further comprises a chamber housing 3. The chamber 2 is disposed in the chamber housing 3. The chamber housing 3 comprises an annular body of a dielectric ceramic material. In this embodiment, the dielectric ceramic material is alumina. The chamber 2 is defined by the body of ceramic material, and forms a central, inner passage through the body.

[0212] The chamber housing is substantially surrounded by a module housing 4. The module housing 4 is formed by metal. In this example, the module housing is in the form of a copper mesh. In this example, the module housing 4 acts as a faraday cage around the chamber housing 3 and the chamber 2.

[0213] An opening 5 is provided at one end of the module housing 4 to enable an aerosol-generating article to be inserted into an open end of the chamber 2.

[0214] A coupler s is provided at the opposite end of the module 1 to the opening 5, and a pin 7 of the coupler 6 extends into the chamber 2. The coupler 6 is configured to couple an alternating electric field generator to the heater module 1 to create an alternating electric field in the chamber 2.

[0215] The heater module 1 forms a cavity resonator. Accordingly, when an aerosol-forming substrate comprising polar molecules is received in the chamber2 of the heater module 1 , and an alternating electric field is created in the resonator via the coupler 6, the aerosol-forming substrate may be dielectrically heated to generate an aerosol.

[0216] Figure 2 shows an aerosol-generating article 10 for use with the heater module 1 of Figure 1 . The aerosol-generating article comprises an aerosol-forming substrate 11 , in the form of a tobacco plug, a hollow acetate tube 12, a mouthpiece filter element 13, a front filter element 14, and an outer wrapper 15. The front filter element 14, aerosol-forming substrate 11 , hollow acetate tube 12, and mouthpiece filter element 13 are arranged end-to-end, in the form of a rod, and secured together by the outer wrapper 15 being tightly wrapped around the elements. In this embodiment, the aerosol-generating article resembles the form of a conventional cigarette, being a substantially circular cylinder. It will be appreciated that in other embodiments the form of the aerosol-generating article, and the form of the aerosol-forming substrate, may be different.

[0217] Figure 3 shows the aerosol-generating article 10 of Figure 2 received in the chamber 2 of the heater module 1 of Figure 1. When the aerosol-generating article 10 is received in the chamber 2 of the heater module 1 , the aerosol-forming substrate 11 is entirely received in the chamber 2, and a portion of the mouthpiece filter element 13 extends out of the chamber 2 through the opening 5 in the module housing 4, such that a user may access the mouthpiece filter element 13 to draw on the aerosol-generating article 10 to inhale generated aerosol during use. It will be appreciated that the chamber 2 of the heater module 1 and the aerosol-generating article 10 may take any suitable form. The form of the chamber 2 of the heater module 1 and the aerosolgenerating article 10 are complimentary, such that the aerosol-forming substrate 11 in the aerosolgenerating article 10 is able to be received in the chamber 2 of the heater module 1.

[0218] Figure 4 shows a heater module 1 according to an embodiment of the disclosure. The heater module 1 is similar to the heater module 1 shown in Figure 1 , and like reference numerals will be used to describe like features.

[0219] The heater module 1 of Figure 4 comprises a chamber 2 that is configured to receive an aerosolgenerating article. In this example, the chamber 2 is substantially circularly cylindrical, and configured to receive an aerosol-generating article in the form of a circularly cylindrical rod, such as a rod having similar dimensions to that of a conventional cigarette. It will be appreciated that in other examples the chamber 2 may have any other suitable shape and size to receive aerosol-generating articles having different shapes and sizes.

[0220] The heater module 1 further comprises a chamber housing 3. The chamber 2 is disposed in the chamber housing 3.

[0221] The chamber housing 3 of the heater module 1 of Figure 4 comprises two regions, a first region 21 , and a second region 22. The first region 21 comprises an annular body of a dielectric ceramic material. In this embodiment, the dielectric ceramic material is alumina having a relative permittivity of about 10. The second region 22 comprises a space filled with air. Accordingly, the second region 22 is a dielectric region, with a relative permittivity of about 1. The first region 21 has a greater relative permittivity than the second region 22. The first region 21 and the second region 22 are arranged end-to-end. The chamber 2 is bounded by the first region 21 and the second region 22, and forms a central, inner passage through the first region 21 and the second region 22.

[0222] The chamber housing 3 is substantially surrounded by a module housing 4. The module housing 4 is formed by a copper mesh. In this example, the module housing 4 acts as a faraday cage around the chamber housing 3 and the chamber 2.

[0223] An opening 5 is provided at one end of the module housing 4 to enable an aerosol-generating article to be inserted into an open end of the chamber 2.

[0224] A coupler 6 is provided at the opposite end of the module 1 to the opening 5, and a pin 7 of the coupler 6 extends into the chamber 2. The coupler 6 is configured to couple an alternating electric field generator to the heater module 1 to create an alternating electric field in the chamber 2.

[0225] The heater module 1 forms a cavity resonator. Accordingly, when an aerosol-forming substrate comprising polar molecules is received in the chamber 2 of the heater module 1 , and an alternating electric field is created in the resonator via the coupler 6, the aerosol-forming substrate may be dielectrically heated to generate an aerosol. In this embodiment, the first region 21 extends from the end of the module housing 4 having the opening 5 in a longitudinal direction of the module 1 , towards the end of the module housing 4 having the couplers, and terminates about halfway along the length of the pin 7 of the couplers. The second region 22 extends from the end of the module housing 4 having the coupler 6 in a longitudinal direction of the module 1 , towards the end having the opening 5, and terminates at the end of the second region 21 , about half way along the length of the pin 7 of the coupler s. In this arrangement, since the relative permittivity of the second region 22 is lower than the relative permittivity of the first region 21 , an alternating electric field created in the cavity resonator is greater in the portion of the chamber 2 that is circumscribed by the second region 22, at the end having the coupler 6, than in the portion of the chamber 2 that is circumscribed by the first region 21 .

[0226] Such a configuration of the chamber housing 3 establishes a gradient in an alternating electric field created in the chamber 2, such that the alternating electric field decreases through the chamber 2 from the end having the coupler 6 to the end with the opening 5.

[0227] Figure 5 shows the aerosol-generating article 10 of Figure 2 received in the chamber 2 of the heater module 1 of Figure 4. When the aerosol-generating article 10 is received in the chamber 2 of the heater module 1 , the aerosol-forming substrate 11 is entirely received in the chamber 2, and a portion of the mouthpiece filter element 13 extends out of the chamber 2 through the opening 5 in the module housing 4, such that a user may access the mouthpiece filter element 13 to draw on the aerosol-generating article 10 to inhale generated aerosol during use.

[0228] Figure 6 shows an aerosol-generating system 101 comprising an aerosol-generating device 100 having the heater module 1 of Figure 5 and the aerosol-generating article 10 of Figure 2 received in the chamber 2 of the heater module 1 .

[0229] The aerosol-generating device 100 comprises a power supply 8, in the form of a rechargeable lithium-ion battery, and control electronics 9 comprising a microprocessor and an alternating electric field generator. The alternating electric field generator is coupled to the heater module 1 via the coupler 6, and is configured to create an alternating electric field in the cavity resonator, via the coupler 6. The control electronics 9 are configured to control the alternating electric field generator. The power supply 8 is configured to supply power to the alternating electric field generator for generating an alternating electric field in the cavity resonator.

[0230] In use, when a user inserts the aerosol-generating article 10 into the chamber 2 of the heater module 1 , and powers on the aerosol-generating device 100, the alternating electric field generator is supplied power from the power supply 8, and creates an alternating electric field in the cavity resonator, via the coupler 6. The aerosol-forming substrate 11 in the aerosol-generating article 10 is heated by dielectric heating, and emits a vapour. When a user draws on the mouthpiece filter element 13 of the aerosol-generating article 10, air is drawn into the aerosol-generating article 10 through the front filter element 14, and entrains vapour emitted from the heated aerosol-forming substrate 11 . The vapour cools and forms an aerosol as it is drawn through the aerosol-generating article 10 to the mouthpiece filter 13, where it is inhaled by the user.

[0231] Figures 7 and 8 show a heater module 1 according to a further embodiment of the disclosure. The heater module 1 is similar to the heater module 1 shown in Figures 4, 5, and 6, and like reference numerals will be used to describe like features. The heater module 1 of Figures 7 and 8 is shown in use, with the aerosol-generating article 10 of Figure 2 received in the chamber 2.

[0232] The heater module 1 of Figure 7 is identical to the heater module 1 of Figures 4, 5, and 6, except that the first region 21 and second region 22 of the chamber housing 3 are configured in an alternative configuration. In the embodiment of Figures 7 and 8, a portion of the first region 21 is movable from a first position to a second position.

[0233] The first region 21 comprises two annular bodies of a dielectric ceramic material. In this embodiment, the dielectric ceramic material is alumina having a relative permittivity of about 10. The second region 22 comprises a space filled with air. Accordingly, the second region 22 is a dielectric region, with a relative permittivity of about 1. The first region 21 has a greater relative permittivity than the second region 22.

[0234] The chamber 2 is bounded by the first region 21 and the second region 22, and forms a central, inner passage through the first region 21 and the second region 22.

[0235] In an initial configuration, with the movable portion of the first region 21 in the first position as shown in Figure 7, the chamber housing 3 comprises a single first region 21 and a single second region 22. The first region 21 and the second region 22 are arranged end-to-end. In this embodiment, the first region 21 extends from the end of the module housing 4 having the coupler 6 towards the end of the module housing 4 having the coupler 6, and terminates at the end of the aerosol-forming substrate 11 of the aerosol-generating article 10, when the aerosol-generating article 10 is received in the chamber 2. The second region 22 extends from the end of the module housing 4 having the opening 5 towards the end having the coupler 6, and terminates at the first region 21 .

[0236] The heater module 1 further comprises an actuator 30, in the form of a tapered button or wedge. The actuator 30 is configured to move the movable portion of the first region 21 between the first position and the second position. When the actuator 30 is pressed in a radial direction, perpendicular to the longitudinal direction of the heater module 1 , the tapered end of the actuator 30 pushes the movable portion of the first region 21 in a longitudinal direction, towards the end of the module housing 4 having the opening 5, and into the second position, as shown in Figure 8.

[0237] In a final configuration, with the movable portion of the first region 21 in the second position as shown in Figure 8, the chamber housing 3 comprises two first regions 21 , separated by a single second region 22.

[0238] The movable portion of the first region 21 may be moved back from the second position to the first position by pulling the actuator 30 out of the pressed position. Advantageously, providing a movable portion of the first region enables the shape of the alternating electric field to be altered. This may be used to optimise the heater module for use with different aerosol-generating articles, or may be used to alterthe heating profile of the heater module during use, to heat different parts of the aerosol-generating article at different rates, at different times in an aerosol-generating experience. For example, the initial configuration may be a configuration used for the majority of an aerosol-generating experience for a user, and the final configuration may be intended to be employed by a user for a brief period of time in which an increase rate of aerosol generation is required towards the end of an aerosol-generating experience.

[0239] Figures 9, 10, and 11 show a heater module according to a further embodiment of the disclosure. The heater module 1 is similar to the heater module 1 shown in Figures 7 and 8, and like reference numerals will be used to describe like features. The heater module 1 of Figures 9, 10, and 11 is shown in use, with the aerosol-generating article 10 of Figure 2 received in the chamber 2.

[0240] The heater module 1 of Figures 9, 10, and 11 is identical to the heater module 1 of Figures 7 and 8, except that the first region 21 and second region 22 of the chamber housing 3 are configured in a different configuration. In the embodiment of Figures 9, 10, and 11 , a portion of the first region 21 is movable from a first position to a second position in a different manner.

[0241] In this embodiment, the second region 22 is larger, such that the movable portion of the first region 21 has further to travel to move between the first position and the second position. Also in this embodiment, the actuator 30 is a slider. The slider 30 is movable in a longitudinal direction of the heater module 1 to move the movable portion of the first region 21 in the longitudinal direction of the heater module 1. The slider 30 enables the movable portion of the first region 21 to be moved continuously between the first position and the second position, stopping at an intermediate position, in between the first position and the second position, if desired.

[0242] An initial configuration, with the movable portion of the first region 21 in the first position is shown in Figure 9. An intermediate configuration, with the movable portion of the first region 21 in an intermediate position is shown in Figure 10. In the intermediate configuration, the chamber housing 3 comprises two first regions 21 and two second regions 22, with the movable portion of the first region 21 being a first region 21 arranged between the two second regions 22. A final configuration, with the movable portion of the first region 21 in the second position, is shown in Figure 11.

[0243] Advantageously, providing a movable portion that is continuously movable between a first position and a second position, and which is positionable in an intermediate position, between the first position and the second position, may enable a user further control over the aerosol generating experience.

[0244] It will be appreciated that other types of actuator and ways of moving a movable portion of a first region between a first position and a second position may also be employed. For example, the movable portion of the first region 21 may be provided with a screw thread, and an inner surface of the module housing 4 may be provided with a complimentary screw thread, such that rotational movement of the movable portion of the first region 21 about a longitudinal axis of the heater module may be used to move the movable portion of the first region 21 in a longitudinal direction of the heater module, between the first position and the second position. In such embodiments, the actuator 30 may be configured for rotational movement about the longitudinal axis of the heater module 1 to move the movable portion of the first region 21 between the first position and the second position.

[0245] Figures 12 and 13 show a heater module according to a further embodiment of the disclosure. The heater module 1 is similar to the heater module 1 shown in Figures 4, 5 and 6, and like reference numerals will be used to describe like features.

[0246] The heater module 1 of Figures 12 and 13 is identical to the heater module 1 of Figures 4, 5, and 6, except that the first region 21 and second region 22 of the chamber housing 3 are configured in a different configuration.

[0247] In the embodiment of Figures 12 and 13, the chamber housing 3 comprises two first regions 21 , and a single second region 22 arranged between the two first regions 21. The two first regions 21 comprise annular bodies of alumina, a dielectric ceramic material having a relative permittivity of about 10. The second region 22 comprises an annular body of polyether ketone (PEEK), a dielectric polymer having a relative permittivity of about 3. The two first regions 21 have a greater relative permittivity than the second region 22. The chamber 2 is defined by the first region 21 and the second region 22, and forms a central, inner passage through the first region 21 and the second region 22.

[0248] The heater module 1 is shown in use in Figure 13, with the aerosol-generating article 10 of Figure 2 received in the chamber 2. As shown in Figure 13, the second region 22 is positioned at a distal end of the aerosol-forming substrate 11 of the aerosol-generating article 10, when the aerosol-generating article

[0249] 10 is received in the chamber 2, such that the second region 22 circumscribes a distal end of the aerosolforming substrate 11 .

[0250] In this configuration, the heater module 1 is configured such that an alternating electric field created in the cavity resonator is greater in the chamber 2 at a distal end of the aerosol-forming substrate

[0251] 11 compared to at other regions of the chamber 2. Advantageously, this may result in rapid heating of the aerosol-forming substrate 11 at the distal end of the aerosol-forming substrate 11 , which may reduce the time required to heat the aerosol-forming substrate 11 before a first puff may be taken on the aerosolgenerating article 10 by a user compared to systems without a chamber housing configured in this way.

[0252] Figures 14 to 19 show various further possible configurations of heater modules according to the disclosure. The size, shape, number, and material properties of the regions of the chamber housing of the heater module may be varied to shape the alternating electric field created within the chamber to control the dielectric heating of an aerosol-forming substrate received in the chamber.

[0253] The heater modules 1 of Figures 14 to 19 are similar to the heater module 1 shown in Figures 4, 5 and 6, and like reference numerals will be used to describe like features. Figure 14 shows a heater module 1 comprising a chamber housing 3 having four first regions 21 , and three second regions 22, each second region 22 being arranged between two first regions 21 . In this embodiment, the first regions 21 comprise annular bodies of alumina, and the second regions 22 comprise spaces filled with air.

[0254] Figure 15 shows a heater module 1 comprising a chamber housing 3 having four first regions 21 , a second region 22 and two third regions 23. Each of the second region 22 and the third regions 23 is arranged between two first regions 21 . In this embodiment, the first regions 21 comprise annular bodies of alumina, the second region 22 comprises a space filled with air, and the third regions 23 comprise annular bodies of PEEK, an electrically insulating, dielectric material.

[0255] Figure 16 shows a heater module 1 comprising a chamber housing 3 having four first regions 21 and three second regions 22, each second region 22 being arranged between two first regions 21 . In this embodiment, the first regions 21 comprise annular bodies of alumina, and the second regions 22 comprise annular bodies 25 of copper, an electrically conductive material. The annular bodies 25 of copper are in contact with the electrically conductive module housing 4 but only extend radially part of the way to the chamber 2. Accordingly, an air gap is also provided in the second regions 22, between the boundary of the chamber 2 and the electrically conductive material 25. Providing an electrically conductive material in a region of the chamber housing may also increase the electric field at or around the electrically conductive material.

[0256] Figure 17 shows a heater module 1 comprising a chamber housing 3 having four first regions 21 and three second regions 22, each second region 22 being arranged between two first regions 21 . In this embodiment, the first regions 21 comprise annular bodies of alumina, and the second regions 22 comprise annular bodies 25 of copper, an electrically conductive material. In this embodiment, the annular bodies 25 of copper are in contact with the electrically conductive module housing 4 and extend radially inwards to the boundary of the chamber 2.

[0257] Figure 18 shows a heater module 1 comprising a chamber housing 3 having four first regions 21 , a second region 22 and two third regions 23. Each of the second region 22 and the third regions 23 is arranged between two first regions 21 . In this embodiment, the first regions 21 comprise annular bodies of alumina, the second region 22 comprises an annular body of copper extending from the module housing 4 to the boundary of the chamber 2, and the third regions 23 comprise spaces filled with air.

[0258] Figure 19 shows a heater module 1 comprising a chamber housing 3 having four first regions 21 , a second region 22, a third region 23, and a further region 24. Each of the second region 22, the third region 23, and the further region is arranged between two first regions 21. In this embodiment, the first regions 21 comprise annular bodies of alumina, the second region 22 comprises an annular body of copper extending between the module housing 4 and the boundary of the chamber 2, the third region 23 comprises an annular body of copper extending from the module housing 4 part of the way to the boundary of the chamber 2, and the third region comprises an annular body of PEEK. It will be appreciated that other configurations for the heater module are envisaged in this disclosure.

Claims

CLAIMS1 . A heater module for an aerosol-generating device configured to dielectrically heat an aerosolgenerating article, the heater module comprising: a chamber configured to receive at least a portion of an aerosol-generating article to be heated; and a chamber housing, the chamber being disposed within a chamber housing, wherein the chamber housing comprises: a first region having a first material property; and a second region having a second material property, wherein the second region comprises a volume or a body that circumscribes a portion of the chamber and extends radially outwards from the chamber, and wherein the first material property and the second material property are such that an electric field created in the chamber and chamber housing is greater in the chamber at the second region of the chamber housing compared to the electric field in the chamber at the first region of the chamber housing.

2. A heater module according to claim 1 , wherein the first material property is relative permittivity, and the first region is a dielectric region having a first relative permittivity, and wherein the second material property is relative permittivity, and the second region is a dielectric region having a second relative permittivity, the second relative permittivity being less than the first relative permittivity.

3. A heater module according to claim 2, wherein the first dielectric region comprises a first dielectric material, and optionally wherein the first dielectric material is a ceramic or a polymeric material.

4. A heater module according to claim 2 or claim 3, wherein the second dielectric region comprises at least one of: air; a vacuum; and a second dielectric material, and optionally wherein the second dielectric material is a ceramic material or a polymeric material.

5. A heater module according to any one of claims 2 to 4, wherein the first relative permittivity is greater than the second relative permittivity by at least 5, or by at least 10.

6. A heater module according to claim 1 , wherein the first material property is electrical conductivity, and the first region is a dielectric region having a first electrical conductivity; and wherein the second material property is electrical conductivity, and the second region is an electricallyconductive region having an electrical conductivity greater than the electrical conductivity of the first region.

7. A heater module according to claim 6, wherein the second region comprises an electrically conductive material, and optionally wherein the electrically conductive material is a metal.

8. A heater module according to any one of claims 2 to 7, wherein the first region is a dielectric region having a first relative permittivity and a first electrical conductivity, and wherein the second region has a second relative permittivity and a second electrical conductivity.

9. A heater module according to any one of claims 1 to 8, wherein the heater module comprises a coupler configured to couple an alternating electric field generator to the chamber for causing an alternating electric field in the chamber.

10. A heater module according to any one of claims 1 to 9, wherein a boundary of the second region is at a boundary of the chamber, and optionally wherein a surface of the second region defines a portion of a surface of the chamber.

11. A heater module according to any one of claims 1 to 10, wherein the first region circumscribes the chamber, and optionally forms an annular disc circumscribing a portion of the chamber.

12. A heater module according to any one of claims 1 to 11 , wherein the volume or body of the second region that circumscribes the chamber extends radially outwards from the chamber into the first region, and optionally wherein the second region forms an annular disc circumscribing a portion of the chamber.

13. A heater module according to any one of claims 1 to 12, wherein the heater module comprises a module housing, wherein the module housing substantially circumscribes the chamber housing, and wherein the module housing comprises an electrically conductive material.

14. A heater module according to claim 13, wherein the second region extends radially outwards from the chamber to the module housing.

15. A heater module according to claim 13, wherein the second region extends radially outwards from the chamber and does not extend to the module housing.

16. An aerosol-generating device configured to dielectrically heat an aerosol-generating article, the aerosol-generating device comprising a heater module according to any one of claims 1 to 15.

17. An aerosol-generating system comprising an aerosol-generating device according to claim 16, and an aerosol-generating article comprising an aerosol-forming substrate.

18. An aerosol-generating system according to claim 17, wherein the second region of the heater module of the aerosol-generating device circumscribes a portion of the aerosol-forming substrate when the aerosol-generating article is received in the chamber.

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