Dielectric heater module, aerosol-forming device and aerosol-forming system

Abstract

An aerosol-forming device, comprising: a heating chamber configured to receive an aerosol- forming article having an aerosol-forming substrate; a dielectric heating arrangement including an oscillation circuitry and at least two electrodes forming a load capacitor of the oscillation circuit for removably receiving and dielectrically heating the aerosol-forming substrate that is arranged at least partially inside the heating chamber; and a body encompassing the heating chamber, the body comprising a body wall, the at least two electrodes, and a low permittivity portion, wherein the electrodes and the low permittivity portion are arranged along the body wall, wherein the low permittivity portion is arranged between the at least two electrodes, and wherein the low permittivity portion comprises a low relative permittivity material with a lower relative permittivity than a body material of the body wall and is exposed towards the heating chamber.

Description

[0001] P 17560

[0002] FTR4073 1 / 43

[0003] DIELECTRIC HEATER MODULE, AEROSOL-FORMING DEVICE AND AEROSOL-FORMING SYSTEM

[0004] The present disclosure generally relates to the field of aerosol-forming devices and systems for generating aerosol, also referred to as aerosol-generating devices and aerosol-generating systems. In particular, the present disclosure relates to a dielectric heater module, an electronic aerosol-forming device and an electronic aerosol-forming system configured to generate or form aerosol, for example aerosol inhalable by a user in one or more user inhalations, as well as an aerosol-forming article.

[0005] Aerosol-forming or aerosol-generating devices are typically designed as handheld devices that can be used by a user for consuming or experiencing, for instance in one or more usage sessions, aerosol generated from an aerosol-forming substrate or an aerosol-forming article. Therein, aerosol is typically generated by heating at least a part of the substrate to a certain temperature sufficient to release aerosol from the substate, also referred to as volatilization or vaporization temperature. The aerosol-forming devices the present disclosure pertains to are, in particular, directed to the field of e-vapor devices, e-cigarettes, and vaporizers as well as heated tobacco products (HTP), heat-not-burn (HNB) devices, tobacco and tobacco-substitute products. The aerosol-forming devices of the present disclosure may also pertain to other types of inhalers, dispensers, or atomizers, for example inhalers, dispensers, or atomizers for medical or pharmaceutical applications.

[0006] Typical aerosol-forming systems can be designed as one-part systems or devices including an aerosol-forming device that can be operated by a user to generate aerosol. Alternatively, aerosol-forming systems can be designed as two-part systems or devices comprising an aerosolforming device and a companion device for storing and / or charging the aerosol-forming device. In either design or configuration, the aerosol-forming system or device can be used by a user for consuming or inhaling, for instance in one or more usage sessions, aerosol generated based on heating an aerosol-forming article or substrate couplable to the aerosol-forming system. In the context of the present disclosure, an aerosol-forming device can refer to both a one-part device and a two-part device, unless explicitly specified otherwise.

[0007] The aerosol-forming article, also referred to as aerosol-generating article, can comprise an aerosol-generating or aerosol-forming substrate. Therein, the aerosol-forming substrate may include a liquid material, a solid material, or both liquid and solid material. Exemplary aerosolforming substrates can comprise solid substrate material with one or more ingredients, such as tobacco material, tobacco cast leaves (TCL) material or cannabis-based material. The substrate material can, for example, be assembled, often with other elements or components, to form a substantially stick-shaped aerosol-forming article. However, other designs and configurations, such as rectangular parallelepiped shaped aerosol-forming articles or substrates are possible.P 17560

[0008] FTR4073 2 / 43

[0009] Other exemplary aerosol-forming substrates include a liquid with one or more ingredients that can be vaporized.

[0010] The liquid, solid or a mixed-form of solid and liquid aerosol-forming substrate may contain one or more ingredients, active ingredients or active agents, which may be vaporized during a usage session and inhaled by the user in one or more user inhalations. A user inhalation is synonymously and interchangeably used herein with “puff” of the user. Exemplary ingredients of the aerosol-forming article or substrate include nicotine, nicotine-containing substances, water, aroma, sugar, moisturising agent, botanicals, preservative, flavouring, for example cocoa, liquorice, menthol and lactic acid or other additives or ingredients. Other exemplary ingredients of the aerosol-forming substrate include one or more pharmaceutical agents, one or more drugs, one or more adjuvants or other active agents. Accordingly, the aerosol formed from a corresponding substrate may contain one or more of these ingredients, active ingredients or active agents and / or may be inhalable by the user in one or more user inhalations.

[0011] The aerosol-forming article may be configured in shape and size to be inserted at least partially into the aerosol-forming device or system. In conventional systems or devices, the aerosol-forming article is usually formed as a stick that can be at least partly inserted into a heating volume, heating cavity or heating chamber of the aerosol-forming device for aerosol consumption. Alternatively or additionally, aerosol-forming substrates can comprise one or more liquids and / or solids, which can, for example, be supplied to the aerosol-forming device in the form of a cartridge capsule, container, reservoir, or pod. Corresponding exemplary aerosol-forming articles can comprise any reservoir containing or being fillable with the liquid and / or solid substrate, which can be vaporized during aerosol consumption by the user based on heating the substrate and / or liquid. Usually, such article can be coupled to, attached to or at least partially inserted into the aerosol-forming device. Alternatively, the cartridge or similar may be fixedly mounted to the aerosol-forming device and refilled by inserting liquid and / or solid into the cartridge or similar.

[0012] For generating the aerosol during use or consumption, heat can be supplied by a heating element, heater device, heater arrangement or heat source to heat at least a portion or part of the aerosol-forming substrate, for example by the use of a dielectric heating device using an oscillator and a load capacitor for generating the alternating electric field, the load capacitor configured to removably accommodate the aerosol-forming substrate. At least a part of the heater arrangement can be arranged in the handheld device or a handheld part of the aerosol-forming device. Alternatively or additionally, at least a part of or the entire heater arrangement can be fixedly associated with or arranged within an aerosol-forming article, for example the electrodes of the load capacitor for instance in the form of a stick, a rectangular parallelepiped shaped article, or cartridge, which can be attached to and / or powered by the handheld device or handheld part of the aerosol-forming device.P 17560

[0013] FTR4073 3 / 43

[0014] The present disclosure relates to dielectric or microwave heating achieved through an alternating electrical field using electrical energy supplied via, drawn from or stored in an energy storage or battery of the aerosol-forming device. As used herein, a battery of the aerosol-forming device can generally refer to an energy storage of the aerosol-forming device configured to store electrical energy. Accordingly, the term energy storage can include one or more battery cells, one or more batteries, one or more capacitors, one or more accumulators or other types of energy storage.

[0015] The dielectric heater module and aerosol-forming device the present disclosure pertains to may, for example, refer to a handheld, battery-powered and / or portable device. Specifically, in the context of the present disclosure, the dielectric heater module, aerosol-forming device and / or the aerosol-forming system may be a portable device and / or system. It may be battery powered. Particularly, the dielectric heater module, aerosol-forming device and / or the aerosol-forming system may be pocket-size, hand-held, suitable for one-hand use and / or may weigh less than 300 g, preferably less than 200 g. It may be shaped and / or sized to fit snugly into a user’s hand. It may be carried in jacket and / or trouser pockets. Particularly, the dielectric heater module, aerosol-forming device and / or the aerosol-forming system may be configured to provide aerosol for human inhalation and / or human consumption, particularly inhalation and / or consumption through the mouth. However, the present disclosure is not limited in this respect, but can be implemented in various forms and designs of aerosol-forming devices and systems.

[0016] Dielectric heating in the present invention can involve generating an alternating electric field to generate heat within the aerosol-forming substrate by exploiting its dielectric properties. This method can provide uniform heating and improve the consistency of vapor production and consequently aerosol formation. To sufficiently heat the aerosol-forming substrate for aerosol formation, specifically but not only in case of liquid aerosol-forming substrate such as e-liquids in e-cigarettes, a high heating power density may be required within certain areas of the heating chamber or into a specific heating zone, in which the aerosol-forming substrate is located. However, supplying sufficient power and focusing the alternating electric field towards the substrate may be challenging inside a dielectric heater module or an aerosol-forming device due to the spread of the alternating electric field generated by the electrodes.

[0017] Therefore, it may be desirable to provide for an improved dielectric heater module, aerosolforming device, aerosol-forming system, and aerosol-forming article, which at least partly mitigate or overcome the aforementioned drawbacks of conventional devices, and systems, in particular utilize dielectric heating in a manner that ensures the electromagnetic field is focused to a specific aera of the aerosol-forming substrate, thereby increasing the dielectric heating power density, reducing the required power to generate the field and providing sufficient dielectric heating for aerosol formation.P 17560

[0018] FTR4073 4 / 43

[0019] These advantages may be achieved by the features described herein.

[0020] Aspects of the present disclosure relate to a dielectric heater module, an aerosol-forming device, an aerosol-forming system and an aerosol-forming article. It is noted that any disclosure presented herein with reference to an or one aspect of the present disclosure, equally applies to any other aspect of the present disclosure, unless explicitly stated otherwise. In particular, it is emphasized that any disclosure presented herein with respect to a dielectric heater module, equally applies to an aerosol-forming device and optionally a charger case or companion device, and to an aerosol-forming system comprising the aerosol-forming device and an aerosol-forming article, and vice versa.

[0021] According to an aspect, there is provided a dielectric heater module or an aerosol-forming device, which may be including a dielectric heater module, the dielectric heater module comprising: a heating chamber configured to receive an aerosol-forming article having an aerosolforming substrate; a dielectric heating arrangement including an oscillation circuitry and at least two electrodes forming a load capacitor of the oscillation circuit for removably receiving and dielectrically heating the aerosol-forming substrate that is arranged at least partially inside the heating chamber; and a body encompassing the heating chamber, the body comprising a body wall, the at least two electrodes, and a low permittivity portion, wherein the electrodes and the low permittivity portion are arranged along the body wall, wherein the low permittivity portion is arranged between the at least two electrodes, and wherein the low permittivity portion comprises a low relative permittivity material with a lower relative permittivity than a body material of the body wall, and particularly is exposed towards the heating chamber.

[0022] One key aspect of this structure of the dielectric heater module is to provide for a discontinuity of a first relative permittivity of the low permittivity portion relative to a second relative permittivity of neighbouring elements or areas, e.g. the body wall or other solid elements of the dielectric heater module, such that a concentration of the electric field increases at the boundary of two elements that form the discontinuity. This allows to create an increased intensity of an alternating electric field in the vicinity of the discontinuity, as the electric field on either side of the boundary must be different. If one material has a much higher permittivity than the other, the electric field will be stronger in the material with the lower permittivity, e.g. the low permittivity portion. This is because the material with higher permittivity can store more electric energy, reducing the field strength within it.

[0023] Accordingly, the present invention provides for structure with a low permittivity portion inside a body encompassing a heating chamber dielectrically heating an aerosol-forming substrate therein by a dielectric heating arrangement. It has been found that the low permittivity portion can significantly improve the heating efficiency of the dielectric heating arrangement for dielectric heating the aerosol-forming substrate. Specifically, by virtue of the low permittivity portion, theP 17560

[0024] FTR4073 5 / 43

[0025] alternating electric field generated inside the heating chamber by the electrodes can be focused or concentrated towards the substrate material or generally a dielectric heating zone inside the heating chamber, into which the substrate is to be inserted when inserting the aerosol-forming article into the body. One reason for this is the difference in the relative permittivity with the body and the electrodes, which can cause the electric field lines of the alternating electric field generated inside the heating chamber to concentrate or focus around the low permittivity portions or material, such as a void, for example. The electric field consequently becomes more intense at the discontinuity as described above. The electric field may thereby be better focused towards the dielectric heating zone and the substrate located therein, effectively increasing the heating power at the substrate.

[0026] Particularly, the electrodes and / or the low permittivity portions may be exposed towards or to the heating chamber, particularly an inner volume or interior of the heating chamber. A protective layer or cover may be provided on the electrodes, particularly such that the electrodes are not exposed towards or to the heating chamber, particularly an inner volume or interior of the heating chamber, more specifically such that no bare material, particularly metal, of the electrodes is exposed towards or to the heating chamber, particularly an inner volume or interior of the heating chamber. In other words, the electrodes may be covered by a protective layer such that the electrodes, particularly their material, is not exposed towards the heating chamber or, in other words, its inner volume.

[0027] As used herein, the dielectric heating arrangement refers to a device or configuration configured to heat at least a part of the aerosol-forming substrate or article to generate aerosol through dielectric heating. Dielectric heating, generally, leverages electromagnetic or electric fields to induce rotation of polar molecules that result in the generation of heat of dielectric materials, which can be induced by the alternating electric field. This heating method exploits the ability of polar molecules within the substrate material to align with an alternating electric, magnetic or electromagnetic field. As the field alternates, these molecules continuously realign, causing molecular friction and dielectric loss, which generates heat. This process is highly efficient for materials containing polar molecules, as is the case with aerosol-forming substrates.

[0028] Generally, dielectric heating arrangement can operate according to different operation principles to dielectrically heat the aerosol-forming substrate. According to the present invention, the dielectric heating arrangement is of a type or operation principle that uses a load capacitor with an oscillation circuitry and electrodes between which at least a part of the aerosol-forming substrate can be placed or arranged. The electrodes can be operated by a control circuitry of the dielectric heating arrangement or aerosol-forming device at a high-frequency or radio-frequency alternating current, such that a high-frequency or radiofrequency alternating electric or electromagnetic field can be generated between the electrodes to heat the substrate material byP 17560

[0029] FTR4073 6 / 43

[0030] interaction with the alternating electric or electromagnetic field. A frequency range of the electric or electromagnetic field in the load capacitor may for example range from about 3 kHz to about 300 GHz. This frequency range may also be referred to as radio-frequency (RF) range. A subrange of the RF range with frequencies of 3 MHz to about 30 MHz can be referred to herein as high-frequency (HF) range.

[0031] Other designs or operation principles of dielectric heating arrangements are not according to the present invention. An example of such alternative design, that is not part of the present invention, is a resonant cavity, which may refer to a substantially closed structure or chamber designed to contain and sustain electromagnetic waves. The cavity is typically shaped and configured to support electromagnetic waves confined within the cavity. The aerosol-forming substrate or article may be placed within this resonant cavity and heated by the interaction of the electromagnetic waves with the substrate material.

[0032] The heating chamber may generally be configured in any shape or form. Specifically, the heating chamber may have any shape or form factor that allows to removably receive the aerosolforming article. For example, the heating chamber may be circular, square, or rectangular in cross-section, cylindrical or cuboid in volume, and / or longitudinal in extension. The heating chamber may specifically but not only be formed, enclosed, encompassed, and / or surrounded by the body, specifically by its body wall. The body may not fully encompass or enclose the heating chamber but only partially. Specifically, the body may at least maintain the at least one opening. For example, at least one opening may remain inside the body for removably receiving the aerosol-forming article therein and thereby inside the heating chamber.

[0033] The control circuitry, as used herein, may refer to a control means for controlling operation of the dielectric heating arrangement or dielectric heater module, and optionally one or more other functions of the dielectric heating arrangement or an aerosol-forming device. The control circuitry may include one or more processors, for example a microcontroller unit (MCU), and / or one or more other processors. The control circuitry may generally be configured to execute programmed instructions, for example stored in a data storage or memory of the aerosol-forming device, to manage the heating process of an aerosol-forming substrate or article based on controlling the dielectric heating arrangement, controlling power supply to the dielectric heating arrangement and / or controlling a power source or energy storage of the dielectric heating arrangement. The control circuitry may be implemented partly in software and partly in hardware. At least a part of the control circuitry and / or at least a part of its functionalities may be implemented as Application-Specific Integrated Circuit (ASIC), on a printed circuit board with one or more discrete components, as a microcontroller-based implementation, as Field-Programmable Gate Array (FPGA), or hybrid implementation using a combination thereof.P 17560

[0034] FTR4073 7 / 43

[0035] The dielectric heater module or aerosol-forming device may comprise one or more main air inlets or air inlets, through which a user can draw air into one or more air channels or airflow paths in the device. During user inhalation, the user may draw air from a surrounding or external environment of the aerosol-forming device via the at least one main air inlet into the device. The drawn air may then be conveyed or guided via the one or more air channels, airflow path structures or airflow paths towards the heating chamber. Therein, at least a part of the drawn air can flow past the heating chamber. Alternatively or additionally, at least a part of the drawn air may flow through at least a part of the aerosol-forming article. For example, the aerosol-forming article may comprise an air inlet that can be coupled to one or more air channels of the device, such that air can enter the aerosol-forming article.

[0036] Also, the dielectric heater module, the aerosol-forming device and / or the aerosol-forming article may further comprise an air, vapor and / or aerosol outlet, where for example the drawn air, enriched with aerosol, can leave the aerosol-forming article towards the user’s mouth for inhalation. Such opening or outlet may be coupled to or formed as a mouthpiece, for example. Also, such opening or outlet may coincide, be located adjacent to or within, or be arranged in parallel to an insertion opening, through which the aerosol-forming article can be received inside the aerosol-forming device and the heating chamber. A mouthpiece may be removably attachable to such outlet. Any coupling mechanism for attachment of the mouthpiece to such outlet may be used. For example, coupling mechanisms with a sliding or rotation motion for coupling the mouthpiece to the outlet may be used to enhance user experience.

[0037] The body may generally be understood as a structure that has one or more body walls encompassing, encircling, or surrounding the heating chamber in between, where the electrodes may be arranged at or attached to the body. The electrodes may be facing each other with their faces or sides that can generate the alternating electric field in between them, thereby forming the dielectric heating zone inside the heating chamber for heating the substrate. The insertion opening of the heating chamber may coincide with the insertion opening of the body. Also, the body may extend in length beyond the heating chamber. In other words, the body may have a longer extension in length, specifically along an axis or body axis thereof, than the heating chamber. The body axis may coincide with a longitudinal device axis of the aerosol-forming device. Specifically, there may be an opening channel, connection channel, or opening sleeve that may connect the insertion opening with the heating chamber. Thereby, for example, a stickshaped aerosol-forming article may be received and reliably held within the channel or sleeve, wherein an end of the article comprising the substrate may be arranged inside the heating chamber for dielectric heating. Accordingly, the body may not be limited to the dimensions, specifically not the length, of the heating chamber, but may extend beyond that. Alternatively, the body may be limited in dimensions, specifically in length, to the heating chamber.P 17560

[0038] FTR4073 8 / 43

[0039] The term body wall is herein to be understood generally as a part or portion of the body that forms at least part of that body. Specifically, the body may comprise one or more body walls. At least one of these body walls or a single body wall may also be seen as a housing of the components or parts located inside the body or towards the inner side or surface of the body wall. These components and parts may be the electrodes and low permittivity portion. Accordingly, the electrodes and the low permittivity portion may be located or arranged on an inner side or inner surface of the body wall, which may be housed or protected by an outer side or outer surface of that body wall. The body wall may generally comprise a closed structure. Specifically, the cross section of the body wall perpendicular to the longitudinal body axis may be a closed structure. In this way, the body wall may completely or fully encompass or surround the heating chamber.

[0040] The body and body wall may generally be made from any material or material mix that provides advantageous functions to the body in the context of the dielectric heating application. For example, the material may be relatively rigid or strong to provide sufficient structural support for the electrodes and any other part or components located therein or thereat. For this purpose, the body wall may generally comprise one or more carriers, carrier layers, or support layers, which may be made or comprise a substantially rigid material. Additionally or alternatively a material may be used in the body wall that provides for heat shielding capabilities. Specifically, such material may be provided in a separate layer within the body wall, or it may be provided together with one or more other layers of the body wall, e.g. with the carrier or support layer. For example, a heat shielding layer may be made from or comprise heat resistive and / or heat absorbing materials, thereby reducing the heat transport from inside the heating chamber towards an outside or surrounding thereof, which reduces the risk that a user observes an uncomfortably high temperature when holding the aerosol-forming device. Similarly, electromagnetic shielding or electromagnetic absorption properties may be provided in the body wall by appropriate material choice and / or design or configuration of a corresponding shielding and / or absorption structure inside the body wall. Such body wall may for example comprise conductive and / or magnetic material to provide these shielding and / or absorption capabilities, specifically but not limited to reflection and / or redirection of electromagnetic radiation towards the heating chamber and / or converting the energy from the electromagnetic radiation into heat. Alternatively, the body wall may be made from or comprise any material arranged in any form or shape, such as in layers, that may provide any of the herein mentioned properties such as structural strength or rigidity, heat shielding, electromagnetic shielding, electromagnetic absorption, and others.

[0041] Generally, the electrodes of the dielectric heating arrangement may be fixed or fixedly attached or positioned inside the dielectric heater module and / or the aerosol-forming device such that when the aerosol-forming article is received inside the heating chamber, it is surrounded by the electrodes for dielectrically heating the aerosol-forming substrate. Alternatively, the electrodesP 17560

[0042] FTR4073 9 / 43

[0043] may be provided on or as part of the aerosol-forming article and the dielectric heater module, aerosol-forming device or dielectric heating arrangement may instead comprise fixed or fixedly attached or positioned electrode interconnections, e.g. in the form of electrical contacts, which are configured to interconnect with the electrodes on the aerosol-forming article. In this case, the dielectric heater module, aerosol-forming device or dielectric heating arrangement may still comprise the electrodes as explained herein by virtue of the aerosol-forming article comprising the electrodes being inserted or received inside the aerosol-forming device, specifically the heating chamber. Also in this case, the low permittivity portion may be formed in between the electrodes. However, different from a fixed or permanent arrangement or attachment of electrodes in the aerosol-forming device, the electrodes in this case may be removably located or arranged inside the aerosol-forming device, specifically removable in the sense that they can be removed each time the aerosol-forming substrate inside the aerosol-forming article has been used up or is depleted.

[0044] Generally, the dielectric heater module may be used or included in any device such as but not limited exclusively to aerosol-forming devices, such as e-cigarettes, medical inhalers, atomizers, or dispensers, for example. Such device, specifically the aerosol-forming device, may include further components or parts as discussed herein, specifically but not limited to an energy source, a communication arrangement, data storage, sensors, and similar, as described herein.

[0045] It is noted that the body comprises at least two electrodes, which may also include three, four, five, six or more electrodes. Specifically, there may be pairs of interdigitated electrodes facing each other provided in the body and arranged along the body wall. For example, there may be two, three or more pairs of electrodes arranged along the body wall. A low permittivity portion may be provided in between each two electrodes that are adjacent to one another, in particular directly adjacent to each other, meaning that there is no further electrode in between these. Accordingly, there may also be multiple low permittivity portions arranged along the body wall. Generally, the electrodes may be elongated and / or flat plates, films or other structures, that may have a face or face side. Each pair of interdigitated electrodes may have their electrodes face each other with their faces or face sides. The back or rear sides of the electrodes opposite of the faces or face sides may be arranged on, attached to, or embedded inside of the body wall, for example, specifically a material layer thereof. Due to their slim or thin form factor, the electrodes have edges or edge sides in between the back or rear sides and the face sides, which may be angled substantially perpendicular to the back and face sides. Specifically, the edges or edge sides may be sides of small width, whereas the face and rear sides may comprise a much larger width due to the plate-shaped extension of the electrodes. The relative permittivity portions may in particular but not limited thereto be formed between opposing or each other facing edges or edge sides of the adjacent electrodes.P 17560

[0046] FTR4073 10 / 43

[0047] In an example, the low relative permittivity material may have at least 30%, in particular at least 40% or at least 50%, less relative permittivity than the body material. Thereby, a particularly comparatively low permittivity may be provided inside the low permittivity portion, which can thereby further concentrate or focus the electric field towards the dielectric heating zone where the substrate is to be located, effectively increasing the heating power compared to a configuration with a higher relative permittivity at the low permittivity portion for a scenario where the same power would be supplied to the dielectric heating arrangement.

[0048] In an example, the low permittivity material may have a relative permittivity below 5, in particular below 4, further in particular below 3. Examples of low permittivity materials that may be used are fluorine-doped silicon dioxide, which has a relative permittivity of about 3.5, and porous organosilicate glass, which can have even lower values due to its porous structure. Another example is Polytetrafluorethylene (PTFE), with a relative permittivity of approximately 2.1. Additionally, materials like polypropylene and polyethylene have relative low permittivity in the range of 2.2 to 2.36 and 2.25, respectively, which may be used within the specified range below 5. Accordingly, the low permittivity material may for example be a solid material which fills out the low permittivity portion, e.g. a cavity thereof in between the electrodes.

[0049] In an example, the low permittivity portion may comprise a void inside the body wall, the void filled with the low relative permittivity material. The low relative permittivity material may in particular be a fluid or vacuum. Accordingly, alternatively to a solid material or combined therewith, a fluid material or even a vacuum may be used. For example, the low relative permittivity material may be air, which has an extremely low permittivity of slightly above 1 and thus slightly above vacuum at a permittivity of 1. Other fluids, specifically gases or liquids, could also be used. Thereby, a particularly low relative permittivity may be provided. Specifically in the case of air, since air may be provided inside the heating chamber anyway as described herein, a particularly simple and inexpensive configuration can be provided, which does not rely on potentially costly material of low relative permittivity.

[0050] In an example, the void may be open towards the heating chamber. In other words, the void may be fluidically coupled with the heating chamber or its volume, specifically in case the void is filled by air. In yet other words, the void may not be closed off or separated from the heating chamber or its volume. Thereby, the void may be an open structure or generally the low permittivity portion may be an open structure with at least one surface or side that is open towards the heating chamber or its volume. Alternatively, however, the low permittivity portion or void may be enclosed inside the body wall. For example, there may be a further support layer as further below described herein, or there may be a protective layer, or any other layer or structure, as part of the body wall or not, which may be enclosing or surrounding the low permittivity portion from the heating chamber. In this case, the low permittivity material, such as vacuum, air, or any otherFTR4073

[0051] 11 / 43

[0052] fluid or solid low permittivity material may be enclosed or entrapped inside the low permittivity portion.

[0053] In an example, the body wall may comprise a cylindrical shape or cuboid shape. In other words, the body wall may be formed or shaped as a cylinder or cuboid. In the case of a cuboid shape, it is possible that the electrode pairs are only arranged along the long side surfaces of the cuboid, and not on the short ones. The insertion opening and / or heating chamber of the body wall or formed inside the body wall may have a corresponding shape, i.e. cylindrical or cuboid, thereby enabling to receive either a stick-shaped or a token-shaped aerosol-forming article. Alternatively, any other shape or form may be possible for the body wall or generally the body, such as but not limited to spherical shapes, hexagonal shapes, and similar.

[0054] In an example, the body wall may comprise an opening for inserting the aerosol-forming article such that the substrate is at least partially arranged inside the heating chamber. Specifically, an insertion opening may be extending through the body wall along an axis of extension of the body. The body wall may be surrounding the insertion opening. For example, the body wall may form hollow cylinder. A virtual base of the cylinder may be forming the opening, and a cylinder axis may be defining an insertion direction for the aerosol-forming article. The insertion direction may in particular be given from the opening towards the heating chamber along the cylinder axis, which may be the longitudinal axis of the body. Alternatively, the body wall may form a hollow cuboid. And, one side of the cuboid may be open to form the opening. That side of the cuboid and the virtual base may be located at one of two respective and opposite ends of the body.

[0055] In an example, the body wall may comprise a support layer supporting the at least two electrodes and the low permittivity portion. Generally, this support layer may also be herein referred to as a carrier layer or structural layer that gives support to the at least two electrodes or, in other words, may carry them or structurally hold these, and optionally the low permittivity portion therebetween depending on its configuration. Specifically, the at least two electrodes may be arranged onto a surface of the support layer, attached thereto, adhered thereto, integrated at least partially with the support layer, enclosed at least partially by the support layer, and similar. This envisions the possibility that there is merely a connection interface, specifically a connection plane, which are shared by the electrodes and the support layer. Such connection plane may provide the required support by using an adhesive, for example. Alternatively, the electrodes may be at least partially embedded or otherwise located at least partially within the support layer. For example, the electrodes may be arranged at least partially along their thickness or with some of their thickness inside the support layer. For example, the support layer may be casted around the electrodes partially. The support layer and any other layer mentioned herein may be separate layers from the same or different material, which may be attached to one another or arranged atFTR4073

[0056] 12 / 43

[0057] one another, collectively forming the body wall or at least being part of the body wall. Any layer mentioned herein including the support layer may comprise a constant or substantially constant thickness and / or width along its extension along the body wall or around the heating chamber or body axis or the thickness and / or width may be varying along its extension. For example, a thickness of a protective layer as defined herein may be lower or higher on the electrodes than on another layer to increase a void that is formed in between the electrodes where the protective layer may be arranged on the support layer, or the protective layer may have a constant thickness.

[0058] In an example, the body wall may comprise a protective layer or a further support layer arranged on the at least two electrodes and / or on the low permittivity portion. The protective layer may protect the electrodes from damage, or the further support layer may be adding further structural support or carrying functionality for the electrodes. Specifically, the support layer may be an outer layer of the body wall that is on an outer or back side of the electrodes from the perspective of the body axis. The protective layer or further support layer on the other hand may be an inner layer of the body wall that is on an inner or face side of the electrodes from the perspective of the body axis. Accordingly, the electrodes may be sandwiched between the support layer or outer layer and the protective layer, further support layer or inner layer.

[0059] In an example, the protective layer may have a thickness of less than 0.4 mm, in particular less than 0.3 mm, and further in particular less than 0.2 mm. Accordingly, the protective layer may for example be provided as a disposition or coating of protective material onto the electrodes for the purpose to protect the electrodes from being damaged when coming into contact with the aerosol-forming article or other objects introduced into the heating chamber or for other reasons. On the other hand, a further support layer may be thicker than the protective layer for providing its support or carrying function. Specifically, the protective layer may generally be flexible or rather flexible or elastic whereas the support layer and / or further support layer may be substantially rigid to carry or support the electrodes at a defined or fixed position with respect to one another. Each one of the support layer and the further support layer may consequently comprise a thickness above 0.4 mm, specifically above 1 mm, more specifically above 2 mm or above 3, 4 or 5 mm.

[0060] In an example, the protective layer or further support layer may surround the heating chamber, and the support layer may surround the protective layer or further support layer. Thereby, the inner layer and outer layer structure of the body wall may be provided as explained herein, which can sandwich the electrodes in between the inner and outer layers. Any additional layers may be placed or arranged on the outer layer formed by the support layer as mentioned herein to provide certain capabilities or functions, such as shielding heat, electromagnetic radiation, and similar.

[0061] In an example, the protective layer or the further support layer may be separated by the low permittivity portion. Specifically, the protective layer or the further support layer may be separatedFTR4073

[0062] 13 / 43

[0063] into layer segments or sections that are separated by the low permittivity portion. In this case, it may be that the low permittivity portion does not extend into the space or distance between the adjacent electrodes but is limited to the distance between the respective layer segments or sections, which may specifically be provided on the electrodes, specifically the face sides thereof. Alternatively, the low permittivity portion may also extend into the space or distance between the adjacent electrodes. Accordingly, the low permittivity portion may extend in thickness or radially from the support layer towards an edge or side of the protective layer or further support layer facing the heating chamber, and thus in between the adjacent electrodes and in between the adjacent layer segments or sections of the protective layer or further support layer.

[0064] In an example, the low permittivity portion may be provided in a recess of the protective layer or the further support layer between the electrodes, the recess being open towards the heating chamber. Such recess may be formed inside the protective layer or further support layer or, in other words, without separating the protective layer or further support layer from one another. For example, the protective layer may be arranged on the electrodes and on the support layer, where the electrodes stick out or protrude from a plane or side of the support layer. In this case, when the protective layer is provided with substantially equal thickness, there will be a recess, dent, or groove in between the electrodes, which may consequently be filed with the low permittivity material, specifically with air, and may be open towards the heating chamber.

[0065] In an example, the support layer, the protective layer, and / or the further support layer may comprise any one or more of: Parylene, in particular Parylene N; glass, in particular quartz glass; a ceramic; Polyetherimide, PEI; and a Polyaryletherketone, PAEK, material, in particular Polyether ether ketone, PEEK. All of the layers may comprise the same material or, alternatively, different layers may comprise different material. As ceramic material, a low-dielectric material such as SiO2, diamond-like carbon, DLC, or similar may be used, for example. The ceramic material or generally the material of any one of the layers may comprise a low relative permittivity of 4 or lower, of 3 or lower or of 2.5 or lower. The protective layer may be disposed with any material onto and / or adhered to the faces of the electrodes and / or the support layer by any technique such as but not limited to an atomic layer deposition method, a physical vapor deposition, polymer coating method, or aerosol deposition.

[0066] In an example, the at least two electrodes may be located adjacent to one another and extending substantially in parallel to each other, and wherein the low permittivity portion may be arranged in between the adjacent at least two electrodes. In particular, as extension of the electrodes, a longitudinal extension of the electrodes along the axis of the body or heating chamber or insertion opening is meant. In between this parallel extension, there may be a distance between the electrodes, specifically in between the edges of the electrodes facing each other. The distance between the adjacently located at least two electrodes may in particular be 2P 17560

[0067] FTR4073 14 / 43

[0068] mm or less, in particular 1 mm or less. Thereby, a high proportion of the area on the body wall or the inner surface thereof or of the support layer may be used to provide electrode face area by one or more pairs of electrodes along the body wall or surrounding the heating chamber. In other words, little area or surface remains unused or without electrodes. Still, the distance has been found to be sufficient to provide a high and specifically focused electric field inside the heating chamber at the substrate by virtue of the low permittivity portion inside that small distance.

[0069] In an example, the low permittivity portion may be arranged at long sides of the at least two electrodes, wherein the long sides are transverse to electrode sides of the at least two electrodes facing the heating chamber. In particular, the long sides may be perpendicular to the electrode sides. The electrode sides may in particular be the faces or face sides of the electrodes to which it is also referred to herein. And the long sides may be the edges or edge faces of the electrodes to which it is also referred to herein. Since the electrodes may extend in length along the axis of the body, body wall, or insertion opening, these edges may also be referred to as long sides.

[0070] In an example, the oscillation circuit may comprise a switching unit and a feedback loop connected to the switching unit, the feedback loop comprising two electric contacts interconnected with the electrodes.

[0071] In an example, the dielectric heater module or aerosol-forming device may comprise two to eight pairs of interdigitated electrodes, wherein each one of the electrodes may be arranged along the circumference of the body wall, wherein the body wall comprises four to sixteen low permittivity portions, and wherein each one of the low permittivity portions is arranged between adjacent electrodes of the pairs of electrodes.

[0072] According to another aspect, there is provided an aerosol-forming system, comprising the aerosol-forming device as described herein and an aerosol-forming article comprising an aerosolforming substrate.

[0073] Also, there may be provided an aerosol-forming article, which may advantageously utilize a low permittivity portion in between at least two electrodes of at least one pair of electrodes formed or arranged in between the electrodes for focusing the alternating electric field generated in between the electrodes and reducing the heating power needed to form aerosol from the substrate material.

[0074] Specifically, an aerosol-forming article may be provided, which comprises an aerosolforming substrate, at least two electrodes, and a low permittivity portion, wherein the aerosolforming substrate is arranged in between the at least two electrodes, and wherein the at least two electrodes and the low permittivity portion are arranged along a perimeter of the aerosol-forming article, and wherein the low permittivity material is arranged in between the at least two electrodes on the perimeter of the aerosol-forming article.P 17560

[0075] FTR4073 15 / 43

[0076] In other words, an aerosol-forming article may be provided, which comprises the aerosolforming substrate in between the at least two electrodes, which may be one pair of electrodes. The at least two electrodes may be arranged along a circumference or perimeter of the substrate or the aerosol-forming article. And a low permittivity portion comprising a low permittivity material may be arranged in between the at least two electrodes on the circumference or perimeter of the substrate or the aerosol-forming article.

[0077] Such aerosol-forming article may in particular be useful when the aerosol-forming device does not itself permanently comprise or have arranged therein the electrodes but when the aerosol-forming device itself comprises the electrodes, which could be interconnected with electrical interconnections of the dielectric heating arrangement coupled to the oscillation circuitry. In this case, when the aerosol-forming device is inserted into the heating chamber or generally the body, these electrical interconnections or electrical contacts may be connected to the electrodes on the aerosol-forming device, after which the substrate inside the aerosol-forming article may be dielectrically heated in between the electrodes. Advantageously, the electrodes may be directly located at the substrate or with little distance by one or more walls, e.g. a wall enclosing or containing the substrate. Thereby, the distance between the substrate and the electrodes is kept at a minimum, reducing the required power for dielectrically heating the substrate for aerosol formation.

[0078] Generally, such aerosol-forming article may comprise any form factor as mentioned herein, e.g. a cylindrical or cuboid form factor or shape. Accordingly, the circumference or perimeter may vary in shape depending on the form factor. For example, in case of a cylindrical article, the circumference or perimeter may be circular. However, in case of a cuboid article, the circumference or perimeter may be square or rectangular, with sharp or rounded corners. Accordingly, the circumference or perimeter is generally to be understood herein as the virtual or imaginary line or boundary that can be drawn or provided around the article or substrate. For example, the aerosol-forming article may have a stick shape or token form. And, the aerosolforming article may by itself have an article body, which may be enclosing the substrate inside an article body wall. The body or article body wall may comprise or form the perimeter or circumference along which the electrodes and low permittivity portion may be arranged. Specifically, the electrodes and low permittivity portion may be arranged inside and / or on such article body wall.

[0079] For example, in case of a liquid substrate, the article body wall may be a container or reservoir wall, which can contain or store therein the liquid substrate. Such article body or article body wall may comprise the herein mentioned circumference or perimeter of the article or substrate. In case of a solid substrate, the article body wall may potentially be omitted in case the solid substrate is pressed or otherwise so compact that it may not be needed. Or, in anotherP 17560

[0080] FTR4073 16 / 43

[0081] example, the electrodes located opposite of one another may at least partially form the article body wall and enclose or surround the substrate therebetween. Also, there may be a protective layer, in particular for heat shielding, on the electrodes in between the substrate and the electrodes. Such protective layer may comprise heat resistive material. The body wall may for example form a hollow cylinder or hollow cuboid, inside which the substrate may be arranged.

[0082] The electrodes of a pair of electrodes of the article may be arranged opposite of one another. Specifically, similar to the aerosol-forming device explained herein, there could be pairs of electrodes, each electrode of a pair of electrodes facing the respective other electrode. In between these electrodes, the substrate may be located or arranged. Depending on the form factor of the article, the electrodes could be curved or straight. The substrate may be surrounded by the perimeter or circumference on which the electrodes and the low permittivity portion is arranged.

[0083] The low permittivity portion or its material in the article may generally comprise a lower relative permittivity than the substrate, than the body material of the article body wall (if present), or generally comprise a relatively low relative permittivity, such as of 5 or less, 4 or less, 3 or less, or even lower. Specifically, the low permittivity portion or its low permittivity material inside the article may be a solid material or a fluid material, including the possibility to use any fluid such as air or vacuum. Specifically, the low permittivity portion inside the aerosol-forming article may comprise a void, which is filled with the low relative permittivity material. The void may be formed inside the substrate and / or the article body wall, for example. Also, the void may be open towards a surrounding of the aerosol-forming article and / or article body wall.

[0084] The invention is defined in the claims. However, below there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0085] Example 1: A dielectric heater module or an aerosol-forming device, which may comprise a dielectric heater module, comprising:

[0086] a heating chamber configured to receive an aerosol-forming article having an aerosolforming substrate;

[0087] a dielectric heating arrangement including an oscillation circuitry and at least two electrodes forming a load capacitor of the oscillation circuit for removably receiving and dielectrically heating the aerosol-forming substrate that is arranged at least partially inside the heating chamber; and

[0088] a body encompassing the heating chamber, the body comprising a body wall, the at least two electrodes, and a low permittivity portion, wherein the electrodes and the low permittivity portion are arranged along the body wall,

[0089] wherein the low permittivity portion is arranged between the at least two electrodes, andFTR4073

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[0091] wherein the low permittivity portion comprises a low relative permittivity material with a lower relative permittivity than a body material of the body wall.

[0092] Example 2: The dielectric heater module of example 1, wherein the low relative permittivity material has at least 30% less relative permittivity than the body material.

[0093] Example 3: The dielectric heater module of example 1 or 2, wherein the low permittivity material has a relative permittivity below 5, in particular below 4, further in particular below 3.

[0094] Example 4: The dielectric heater module of any one of the previous examples, wherein the low permittivity portion comprises a void inside the body wall, the void filled with the low relative permittivity material, and the low relative permittivity material being a fluid or vacuum.

[0095] Example 5: The dielectric heater module of example 4, wherein the low relative permittivity material is air.

[0096] Example 6: The dielectric heater module of claim 4 or 5, wherein the void is open towards the heating chamber.

[0097] Example 7: The dielectric heater module of any one of the previous examples, wherein the body wall comprises a cylindrical shape or cuboid shape.

[0098] Example 8: The dielectric heater module of any one of the previous examples, wherein the body wall comprises an opening for inserting the aerosol-forming article such that the substrate is at least partially arranged inside the heating chamber.

[0099] Example 9: The dielectric heater module of example 8, wherein the body wall forms a hollow cylinder, a virtual base of the cylinder forming the opening, a cylinder axis defining an insertion direction for the aerosol-forming article.

[0100] Example 10: The dielectric heater module of example 8, where the body wall forms a hollow cuboid, one side of the cuboid being open to form the opening.

[0101] Example 11 : The dielectric heater module of any one of the previous examples, wherein the body wall comprises a support layer supporting the at least two electrodes and the low permittivity portion.

[0102] Example 12: The dielectric heater module of example 11, wherein the body wall comprises a protective layer or a further support layer arranged on the at least two electrodes and / or on the low permittivity portion.

[0103] Example 13: The dielectric heater module of example 12, wherein the protective layer has a thickness of less than 0.4 mm, in particular less than 0.3 mm, and further in particular less than 0.2 mm.

[0104] Example 14: The dielectric heater module of example 12 or 13, wherein the protective layer or further support layer surrounds the heating chamber, and the support layer surrounds the protective layer or further support layer.FTR4073

[0105] 18 / 43

[0106] Example 15: The dielectric heater module of any one of examples 12 to 14, wherein the protective layer or the further support layer is separated by the low permittivity portion.

[0107] Example 16: The dielectric heater module of any one of examples 12 to 14, wherein the low permittivity portion is provided in a recess of the protective layer or the further support layer between the electrodes, the recess being open towards the heating chamber.

[0108] Example 17: The dielectric heater module of any one of examples 11 to 16, wherein the support layer, the protective layer, and / or the further support layer comprises one or more of:

[0109] Parylene, in particular Parylene N;

[0110] glass, in particular quartz glass;

[0111] a ceramic;

[0112] Polyetherimide, PEI; and

[0113] a Polyaryletherketone, PAEK, material, in particular Polyether ether ketone, PEEK. Example 18: The dielectric heater module of any one of the previous examples, wherein the at least two electrodes are located adjacent to one another and extending substantially in parallel to each other, and wherein the low permittivity portion is arranged in between the adjacent at least two electrodes.

[0114] Example 19: The dielectric heater module of example 18, wherein a distance between the adjacently located at least two electrodes is 2 mm or less, in particular 1 mm or less.

[0115] Example 20: The dielectric heater module of example 18 or 19, wherein the low permittivity portion is arranged at long sides of the at least two electrodes, wherein the long sides are transverse to electrode sides of the at least two electrodes facing the heating chamber.

[0116] Example 21 : The dielectric heater module of any one of the previous examples, wherein the oscillation circuit comprises a switching unit and a feedback loop connected to the switching unit, the feedback loop comprising two electric contacts interconnected with the electrodes.

[0117] Example 22: The dielectric heater module of any one of the previous examples, wherein the dielectric heater module or aerosol-forming device comprises two to eight pairs of interdigitated electrodes, wherein each one of the electrodes is arranged along the circumference of the body wall, wherein the body wall comprises four to sixteen low permittivity portions, and wherein each one of the low permittivity portions is arranged between adjacent electrodes of the pairs of electrodes.

[0118] It is noted that examples 2 to 22 equally apply to the alternative of the aerosol-forming device of example 1.

[0119] Example 23A: An aerosol-forming device, comprising the dielectric heater module of any one of the previous examples, and optionally a dielectric heating arrangement coupled thereto.P 17560

[0120] FTR4073 19 / 43

[0121] Example 23B: An aerosol-forming system, comprising the dielectric heater module or aerosol-forming device of any one of the previous examples and an aerosol-forming article comprising an aerosol-forming substrate.

[0122] Example 24: An aerosol-forming article comprising an aerosol-forming substrate, at least two electrodes, and a low permittivity portion, wherein the aerosol-forming substrate is arranged in between the at least two electrodes, and wherein the at least two electrodes and the low permittivity portion are arranged along a perimeter of the aerosol-forming article, and wherein the low permittivity material is arranged in between the at least two electrodes on the perimeter of the aerosol-forming article.

[0123] Example 25: The aerosol-forming article of example 24, wherein the two electrodes and the low permittivity portion are arranged at or inside an article body wall of an article body of the aerosol-forming article.

[0124] Example 26: The aerosol-forming article of example 24 or 25, wherein the article body wall comprises a cylindrical shape or cuboid shape.

[0125] Example 27: The aerosol-forming article of any one of examples 24 to 26, wherein the low permittivity material has a relative permittivity below 5, in particular below 4, further in particular below 3.

[0126] Example 28: The aerosol-forming article of any one of examples 24 to 27, wherein the low permittivity material has a relative permittivity lower than the aerosol-forming substrate or the article body wall.

[0127] Example 29: The aerosol-forming article of any one of examples 24 to 28, wherein the low permittivity portion comprises a void, in particular inside the substrate and / or the article body wall, the void filled with the low relative permittivity material, and the low relative permittivity material being a fluid or vacuum.

[0128] Example 30: The aerosol-forming article of any one of examples 24 to 29, wherein the low relative permittivity material is air.

[0129] Example 31: The aerosol-forming article of any one of examples 24 to 30, wherein the void is open towards a surrounding of the aerosol-forming article or a surrounding of the article body wall.

[0130] Examples will now be further described with reference to the figures in which:

[0131] Figure 1 schematically shows an exemplary aerosol-forming system;

[0132] Figure 2A schematically shows a cross-sectional view of an exemplary aerosol-forming system along a longitudinal axis;

[0133] Figure 2B schematically shows a cross-sectional view of an exemplary aerosol-forming system along a transverse axis;

[0134] Figure 3 schematically illustrates an oscillator circuitry for an aerosol-forming system;P 17560

[0135] FTR4073 20 / 43

[0136] Figure 4 schematically illustrates a resonant circuit for an aerosol-forming system;

[0137] Figure 5 schematically shows a perspective view of an example of a body for an aerosolforming device or dielectric heater module;

[0138] Figure 6 schematically shows a cross sectional view through the body of Figure 5;

[0139] Figure 7A schematically shows a cross sectional view through an example of a body that is alternative to the one of Figure 6;

[0140] Figure 7B schematically shows a cross sectional view through an example of a body that has a different form factor than the one of Fig. 7A;

[0141] Figures 8 to 13 show schematic illustrations of sections of different examples of bodies for aerosol-forming devices, each portion comprising a respective oscillator circuitry and electrodes coupled thereto arranged on and / or in the body; and

[0142] Figures 14 and 15 show schematic illustrations of different examples of aerosol-forming articles comprising electrodes.

[0143] The figures are schematic only and not to scale.

[0144] Figure 1 shows an exemplary and schematic aerosol-forming system 500 for forming or, in other words, generating aerosol, for example for consumption or inhalation by a user in one or more usage sessions. The system 500 comprises an aerosol-forming device 100 and optionally a companion device 300 for storing the aerosol-forming device 100. The companion device 300 may be a charging device or charger case for charging the aerosol-forming device 100 and / or an energy storage 190 or power supply 190 thereof.

[0145] The aerosol-forming device 100 may comprise an insertion opening 101 for at least partially or completely inserting an aerosol-forming article 200. The aerosol-forming article 200 may include or be shaped as a stick, cartridge, container, capsule, pod, token, or any other storage or container comprising aerosol-forming substrate 210 of any shape or form, including liquid and / or solid substrate 210. Specifically, the aerosol-forming substrate 210 may comprise tobacco-based or non-tobacco based materials having an aerosol forming material therein and optionally one or more active agents or ingredients, such as nicotine, pharmaceutical, botanicals, flavorants, liquid substrates with one or more active agents or ingredients, or a combination thereof.

[0146] Optionally, the aerosol-forming device 100 may comprise a mouthpiece (not shown), through which a user may inhale aerosol provided by the aerosol-forming device 100 for consumption during a usage session. The aerosol may be provided from the liquid aerosolforming substrate 210 provided inside or contained within the aerosol-forming device 100.

[0147] The exemplary aerosol-forming device 100 of Fig. 1 further includes a dielectric heater module 110 configured to dielectrically heat the liquid aerosol-forming substrate 210. In the example of Fig. 1, the dielectric heater module 110 may comprise a body 170 at least partially formed around or at least partially surrounding or encompassing a heating chamber 120. TheP 17560

[0148] FTR4073 21 / 43

[0149] body 170 may comprise an insertion opening 101. The body 170 may comprise electromagnetic shielding capabilities to shield the surrounding of the aerosol-forming device 100 from electromagnetic radiation.

[0150] The dielectric heater module 110 further comprises at least two electrode interconnections 132, 134, which may for example be in the form of contacts, as shown in Fig. 1. Specifically, the dielectric heater module 110 may comprise one, two, three or more pairs of electrode interconnections 132, 134. These electrode interconnections 132, 134 are configured to electrically interconnect at least two electrodes 114, 116 as shown in Fig. 1. These electrodes 114, 116 are connected to a load capacitor 112 in Fig. 1, which is part of a dielectric heating arrangement of the dielectric heater module 110 and may be included in the aerosol-forming device 100. The dielectric heating arrangement and thereby the dielectric heater module 110 comprising it further comprises an oscillation circuit 130. In the variant shown, electrodes 114 and 116 of the dielectric heating arrangement are exposed to the inner volume of the heating chamber 120. Similarly, low permittivity portions 172 as further described herein that are located in between the electrodes 114, 116 are exposed to the inner volume of the heating chamber 120, thereby creating an intensified electric field strength of the electrodes 114, 116 at a heating zone 122 inside the heating chamber 120.

[0151] The first electrode 114 and the second electrode 116 are arranged opposite to each other and are spaced-apart from each other by a distance, in the example with the aerosol-forming article 200 in a direction orthogonal or transverse to an insertion direction or axis 103 for inserting the aerosol-forming article 200. The insertion direction or axis 103 may define or be parallel to a longitudinal direction or axis of the aerosol-forming device 100 and / or body 170. The two opposing and spaced-apart electrodes 114, 116 form or define a heating chamber 120 configured to at least partly receive the aerosol-forming article 200 or liquid aerosol-forming substrate 210 therebetween. As seen in Fig. 1 , the electrodes 114, 116 may be generally formed or provided at the body 170 or near or adjacent thereto. Specifically, the electrodes 114, 116 may be provided on an inner side, inner surface or wall of the body 170 surrounding or forming the heating chamber 118, specifically together with the electrodes 114, 116, which enable the dielectric heating of the aerosol-forming substrate 210 inside the heating chamber 120.

[0152] The heating chamber 120 and at least part of the aerosol-forming article 200 may be sized such that the aerosol-forming substrate 210 is in contact or in close proximity to both the first electrode 114 and the second electrode 116 of the load capacitor 112 when received within the heating chamber 120. Moreover, the load capacitor 112 with the first electrode 114 and the second electrode 116 can form part of a feedback loop 133 (see Figure 2) of an oscillator circuitry 130, also referred to herein as oscillation circuit 130, via the electrode interconnections 132, 134. It should be noted that the load capacitor 112 can comprise more than one electrode pair, inP 17560

[0153] FTR4073 22 / 43

[0154] particular, the load capacitor 112 can comprise two, three, four, or even more pairs of interdigitated electrodes 114, 116.

[0155] In other examples, the first electrode 114 and the second electrode 116 may form part of the aerosol-forming article 200 comprising the aerosol-forming substrate 210. In such embodiments, the heating chamber 120 or a corresponding cavity between the first and second electrode interconnections 132, 134 can be sized such that, when the aerosol-forming article 200 is placed or located within the heating chamber 120, an electrical connection is established between the first electrode 114 and the first electrode interconnection 132, and the second electrode 116 and the second electrode interconnection 134.

[0156] The aerosol-forming device 100 further comprises a power supply 190, power source 190 or energy source 190, and a control circuitry 140 electrically, communicatively and / or operatively coupled to the dielectric heater module 110, specifically the oscillator circuit 130. In this embodiment, the power supply 190 can be a rechargeable lithium-ion battery, for example with one or more lithium-ion battery cells. Hence, the aerosol-forming device 100 can be portable, battery-powered and handheld.

[0157] The control circuitry 140 can be configured to control the energy source 190 and / or the dielectric heater module 110. In particular, the control circuitry 140 can be configured to control a supply of electrical power from the energy source 190 to the dielectric heater module 110, thereby controlling the heating, a heating operation, activation and / or deactivation of the dielectric heater module 110. The control circuitry 140 can include one or more controllers, microcontrollers, or processors 142 for data processing.

[0158] The energy source 190 may be charged based on connecting terminals of the device 100 with a main power supply, e.g., a USB charger. Alternatively, the energy storage 190 may be charged based on mechanically coupling the aerosol-forming device 100 with the companion device 300. In Figure 1, both the aerosol-forming device 100 and the companion device 300 comprise an energy storage 190, 310. In an example, energy storage 190 of the aerosol-forming device 100 may be charged based on coupling the device 100 to the companion device 300, for example based on at least partly inserting the device 100 into a compartment or recess of the companion device 300. Upon mechanically coupling the device 100, 300, an electrical connection between terminals or electrical connections of the aerosol-forming device 100 and the companion device 300 can be established to charge the energy storage 190 of the aerosol-forming device 100 via the energy storage 310 of the companion device 300. The energy storage 310 of the companion device 300 can, for example, be re-charged via connection to a main power supply, e.g., a USB charger. Alternatively, or additionally, one or both the energy storage 190 of the aerosol-forming device 100 and the energy storage 310 of the companion device 300 may beP 17560

[0159] FTR4073 23 / 43

[0160] removable and / or replaceable. In other words, energy storages 190, 310 may be replaceable energy storages or batteries.

[0161] The aerosol-forming device 100 may further comprise a communications arrangement 150 or interface 150 for communicatively coupling the aerosol-forming device 100 with the companion device 300 or other devices, such as a smart phone or server, for example, via an Internet connection, a wireless LAN connection, a WiFi connection, a Bluetooth connection, a mobile phone network, a mobile data connection for example but not limited to a 3G / 4G / 5G connection, an edge connection, an LTE connection, a BUS connection, a wireless connection, a wired connection, an optical data connection such as but not limited to IrDa, a radio connection, a near field connection, and / or an loT connection.

[0162] The aerosol-forming device 100 may further comprise a data storage 152 or memory for storing information, program code or data. Data storage 152 may also store collected values of sensors and / or one or more mathematical functions or formulas, software and / or computer instructions that can be executed by the control circuitry 140, particularly by the controller 142 and / or processor 142.

[0163] One or more sensors 154 may be arranged on, at or in the aerosol-forming device 100 to collect data. One or more of the sensors 154 may for example be a motion sensor, an accelerometer, a gyroscope, an image sensor, a pyrometer, a presence sensor, a touch sensor, a temperature sensor, a strain sensor, a pressure sensor, a flow sensor, or any other suitable sensor.

[0164] The aerosol-forming device 100 may further comprise one or more user interface components 156 or user interfaces 156, for example comprising an input and / or output element, for example in the form of a pushbutton, a capacitive button, a touch display, one or more LEDs, an acoustic interface or the like. The one or more interface components 156 may be used or function as a power button to activate or deactivate the dielectric heater module 110 thereby to activate or deactivate the aerosol-forming device 100. Upon activation of the aerosol-forming device 100 or the dielectric heater module 110 or its dielectric heating arrangement heat may be applied to at least a part of the aerosol-forming article 200 or aerosol-forming substrate 210, such that aerosol can be generated for consumption or inhalation by the user, for example in a usage session. The one or more user interface components 156 can be arranged on an outer surface of the device 100 or can be integrated in a housing of the device 100.

[0165] In use, power or electrical energy can be provided from the energy storage 190 to the dielectric heater module 110, for example when a user activates the device 100. For example, the device 100 can be activated by one or more of a sensor signal of at least one sensor 154 of the aerosol-forming device, insertion of an aerosol-forming article 200 at least partly into the aerosol-forming device 100, coupling of an aerosol-forming article 200 to the aerosol-formingP 17560

[0166] FTR4073 24 / 43

[0167] device 100, mechanical decoupling of the aerosol-forming device 100 from the companion device 300, and a control signal from the one or more user interfaces 156 triggered by the user of the aerosol-forming device 100. As noted above, sensor 154 can include one or more of a motion sensor, an accelerometer, a gyroscope, an image sensor, a pyrometer, a presence sensor, and a touch sensor, such that the device 100 can be activated for example by moving it, by touching it or by the mere presence of the user in the vicinity of the device 100.

[0168] When a user initiates a user inhalation or puff, air at ambient temperature can be drawn from an external environment of the device 100 via an air inlet, air channel or airflow path 162 towards the dielectric heater module 110. The air drawn by the user has a lower temperature than the dielectric heater module 110 and liquid aerosol-forming substrate 210 that may be pre-heated to the pre-heating temperature. Hence, the drawn air departs a cooling effect onto the dielectric heater module 110 and aerosol-forming substrate 210, which leads to a decrease in temperature and hence to an increase in relative permittivity of the aerosol-forming substate 210. As a consequence, the capacitance of the load capacitor 112 increases, and an oscillation frequency of the oscillator circuitry 130 decreases due to the increasing capacitance, and hence increasing LC constant of the oscillator circuitry 130. Since also resistive losses will increase with increasing relative permittivity, the power consumption of the dielectric heater module 110 will increase. One or more of these effects, respectively one or more of these changes in the capacitance of the load capacitor 112, the oscillation frequency of the oscillator circuitry 130 and the power consumption can be determined or monitored by the control circuitry 140 in order to detect an onset, a start and / or occurrence of the user inhalation.

[0169] Upon detecting the user inhalation, control circuitry 140 can increase the power provided to the dielectric heater module 110 and power it at a second power level, where the dielectric heater module 110 and / or substrate 210 can be heated to the volatilization or vaporization temperature to generate inhalable aerosol. Therein, upon detection of the user inhalation, the temperature of the dielectric heater module 110 and / or substrate 210 may be increased at a rate of about 100°C within 0.2 seconds, within 0.1 seconds or even higher rate. Accordingly, the power to the dielectric heater module 110 can be immediately increased upon detecting a user inhalation to allow for aerosol generation and inhalation by the user. Hence, energy can be efficiently used during user inhalation and saved at other times. Also, depletion of the substrate 210 can be avoided at times when the user does not inhale.

[0170] The opposite effect can be used by the control circuitry 140 to detect an end or termination of the user inhalation. Specifically, as soon as the user stops inhaling, the airflow stops and the dielectric heater module 110 and substrate 210 will heat further up. This increase in temperature can decrease the relative permittivity of the substrate 210, and hence decrease the capacitance of the load capacitor 112, increase the oscillation frequency of the oscillator circuitry 130, andP 17560

[0171] FTR4073 25 / 43

[0172] decrease the power consumption of the dielectric heater module 110. One or more of these changes can be determined or detected by the control circuitry 140, thereby detecting termination of the user inhalation.

[0173] Upon detecting termination of the user inhalation, the control circuitry 140 may cut the power supply to the dielectric heater module 110, and the next or subsequent user inhalation can be determined or detected, as the dielectric heater module 110 and substrate 210 may still have an elevated temperature above room or ambient temperature. Optionally, however, the control circuitry 140 may power the dielectric heater module 110 at the first power level in response to detecting termination of the user inhalation, to ensure that the dielectric heater module 110 and substrate 210 have at least the pre-heating temperature, in order to allow for cooling by air drawn by the user in the subsequent user inhalation, which can then be detected again by the control circuitry 140 as further change in one or more operational parameters and / or the power consumption.

[0174] Accordingly, a reliable, efficient and robust mechanism for detecting puffs or user inhalations can be implemented or provided, in particular without requiring dedicated hardware, such as a dedicated puff sensor for detecting when a puff occurs. This can also save space in the device 100 for other components or parts, or can allow to increase a size of the energy storage 190, for example.

[0175] Optionally, the control circuitry 140 may be configured to detect or determine depletion or a depletion level of the aerosol-forming article 200. With increasing depletion, the relative permittivity of the substrate 210 should decrease, and hence the capacitance of the load capacitor 112 should decrease, the oscillation frequency of the oscillator circuitry 130 should increase, and the power consumption of the dielectric heater module 110 should decrease. One or more of these changes can be determined or detected by the control circuitry 140, thereby enabling determination of the depletion or depletion level of the article 200.

[0176] Figures 2A and 2B each show a cross-sectional view of an aerosol-forming system 500. Therein, Fig. 2A shows a cross-section along a longitudinal axis or plane of the aerosol-forming device 100, and Fig. 2B shows a cross-section along the transverse axis or plane 20 shown in Figure 2A.

[0177] Unless stated otherwise, the aerosol-forming system 500 of Figs. 2A and 2B comprises the same features, functions and elements as the aerosol-forming device 100 and system 500 described with reference to Figure 1. The exemplary system 500 of Figures 2A and 2B may exemplary be designed for vaporizing liquid substrate material 210 but is not limited thereto and may in particular also be configured to vaporize and form aerosol from solid substrate material 210.P 17560

[0178] FTR4073 26 / 43

[0179] The aerosol-forming article 200 of the device 100 in Figs. 2A and 2B may be exemplary formed as cartridge 200, container 200 or pod 200, that can be inserted along a longitudinal axis 103 of the device 100 into a body 170 of the device 100. Alternatively, the aerosol-forming article 200 could for example be formed as a stick- or token-shaped article with a solid substrate material 210. Any reference herein to a cartridge 200 as shown exemplary in Figs. 2A and 2B equally applies to or may be replaced by any other form or type of article 200.

[0180] The cartridge 200 of this example includes a reservoir 205 that is at least partly filled with liquid substrate 210, which in the case of an e-cigarette as aerosol-forming device 100 may also be referred to as an e-liquid 210. In particular, a bottom part 212 or end 212 of the cartridge 200 may be inserted into a heating chamber 120 of the device 100. At an opposite end 214 of the aerosol-forming article 200, an aerosol outlet 215 can be formed, via which the user can draw air and inhalable aerosol.

[0181] The heating chamber 120 is defined by two semi-circular, half cylindrical, or arc-like shaped electrodes 114, 116 of a dielectric heater module 110 of the device 100. Also, more than two electrodes 114, 116 or electrode pairs may be utilized. For example, a plurality of two, three or more electrode pairs of interdigitated electrodes may be arranged around at least a part of a circumference or perimeter of the article 200 and inside or as part of the body 170. And two or three electrodes 114, 116 of each pair of interdigitated electrodes may be connected with one another by any conductive structure, such as a conductive ring. Specifically, there may be two conductive rings arranged at or on the body 170, each conductive ring connecting another electrode in two or three pairs of interdigitated electrodes.

[0182] Specifically, there may be an upper conductive ring 118 at an upper portion or upper end portion of the body 170, as may for example be seen in Fig. 5, and there may be a lower conductive ring at a lower portion or lower end portion of the body 170, which may be opposite of the upper conductive ring 118 or upper portion. In particular, any one or both upper conductive structures or rings may be arranged at or on an inner surface or side of a body wall 171 of the body 170, which may be formed by the body wall 171.

[0183] The at least two electrodes 114, 116 are part of a load capacitor 112 of the dielectric heating arrangement of the dielectric heater module 110 configured to dielectrically heat the liquid substrate material 210. The length of the electrodes 114, 116, measured parallel to an insertion direction of the article 200 or longitudinal axis 103 of the device 100, defines a dielectric heating zone 222, in which substrate material can be dielectrically heated and vaporized.

[0184] In order to vaporize the substrate 210 in a controlled manner, in the present example of a cartridge 200 as article 200, the cartridge 200 comprises a wicking element 220 or liquid transfer element 220, which includes a porous material that can be soaked with the substrate 210, for example via capillary forces, diffusion, or osmotic forces. The wicking or liquid transfer elementP 17560

[0185] FTR4073 27IA3

[0186] 220 can be configured to draw the liquid substrate 210 from the reservoir 205 to at least a part of the dielectric heater module 110, in particular towards the electrodes 114, 116. Common materials used for the wicking element ca include organic cotton, silica, or ceramic.

[0187] In the example shown in Figs. 2A and 2B, the cartridge 200 includes two liquid transfer elements 220 arranged opposite to each other. Specifically, the two electrodes 114, 116 are spaced apart from each other along the circumferential direction of the device 100 or cartridge 200, such that two gaps 115, 117 are formed in circumferential direction of the device 100 or cartridge 200. In each gap 115, 117, one of the liquid transfer elements 220 is arranged, as can best be seen in FIG. 2B. Also, each of the gaps 115, 117 forms or defines a load capacitor 112, which functions similar or analogue to the load capacitor 112 of Fig. 1.

[0188] As also mentioned above, the electrodes 114, 116 can be part of the cartridge 200 and contacted to respective electrical contacts of the device 100. Alternatively, the electrodes 114, 116 can be part of the device 100.

[0189] To ensure a homogenous supply of substrate 210 from the reservoir 205 to the liquid transfer elements 220, the cartridge 200 comprises a feeding structure 230, which can for example, be a hollow cylindrical structure in the centre of the cartridge 200 at the bottom end 212, which is placed inside the heating chamber 120 or heating zone 222. There can also be individual liquid feeding structures for each liquid transfer element 220.

[0190] A surface 240 of each of the liquid transfer elements 220 that faces the feeding structure 230 acts as liquid ingress area or surface (LIS), via which liquid substrate 210 is drawn by the liquid transfer elements 220. As the liquid transfer elements 220 are arranged in the gaps 115, 117 formed between the electrodes 114, 116 in circumferential direction, an electrical field strength between the electrodes 114, 116 can be very high at or near the liquid transfer elements 220, such that the substrate 210 can be vaporized within the liquid transfer elements 220. Vaporized substrate material can then exit or leave the liquid transfer elements 220 via so-called vapor egress areas or surfaces (VES) 242 of the wicking elements 220, which are arranged opposite to the liquid ingress surfaces 240 in radial direction of the device 100 or cartridge 200.

[0191] As can best be seen in Figure 2B, the liquid transfer elements 220 can be dome-like shaped, have a trapezoidal cross-section, or be curved towards the inside of the cartridge 200, such that the respective vapor egress surface 242 is larger than the liquid ingress surface 240 of each liquid transfer element 220.

[0192] Between the cartridge 200 and the body 170 of the aerosol-forming device 100, an air channel 160 or airflow path 160 is formed. The airflow path 160 can have multiple sections that may be fluidly coupled or connected. In particular, an air inlet 161 can be formed as a gap between the cartridge 200 and the body 170, for example at or close to the end 214 of the cartridge 200 where the aerosol outlet 215 is formed. The gap or air inlet 161 may span the entire or only a partP 17560

[0193] FTR4073 28 / 43

[0194] of the circumference of the device 100. Accordingly, the gap or air inlet 161 can be ring-like or annular formed.

[0195] The air inlet 161 connects to lateral sections 162 of the airflow path 160, which lateral sections 162 extend in longitudinal direction of the device 100 between the electrodes 114, 116 and the liquid transfer elements 220 on two opposite sides of the heating chamber 120 along each of the vapor egress surfaces 242 towards the end 212 of the cartridge 200. The lateral sections 162 can also be formed as tubular or cylindrical sections that surround at least a part of the heating chamber 120 and dielectric heater module 110 along its circumference.

[0196] Moreover, these lateral sections 162 may represent or include gaps or voids between the adjacent electrodes 114, 116, which can be filled by air coming from the air inlet 161. Since air has a very low relative permittivity of slightly above 1, the void or gap between the electrodes 114, 116 allows for concentration of the alternating electric field lines around that void and orientation towards the dielectric heating zone 220. Specifically, this void or gap may be herein referred to also as a low permittivity portion or the low permittivity portion may comprise the air-filled void or gap. In any case, the low permittivity portion allows for a focus electric field of high heating power inside the dielectric heating zone 220.

[0197] Near or close to the bottom part or end 212 of the cartridge 200, the airflow path 160, respectively, the lateral sections 162 thereof are connected via inlets or openings 164 at the bottom of the heating chamber 120 to an interior volume 260 or interior channel 260 of the cartridge 200 that is fluidly coupled to the aerosol outlet 215, such that air can be drawn via the openings 164 towards the air outlet 215 of the cartridge 200 through the interior volume 260. The interior channel or volume 260 of the cartridge 200 may also serve as aerosolization chamber, as indicated by the circular arrow in Figure 2A. It should be noted that various designs and configurations of the airflow path 160 are possible. For example, on two opposing sides of the vapor egress surface 242 of each liquid transfer element 220, a lateral airflow channel may be formed.

[0198] Similar to the functionality of the device 100 of Figure 1, upon activation of the device 100 of Figures 2A and 2B, the control circuitry 140 may power the dielectric heater module 110 to a first power level to heat up the at least a part of the dielectric heater module 110 and / or substrate 210 in the heating zone 222 to a pre-heating temperature above ambient temperature and below a volatilization or vaporization temperature sufficient to release aerosol from the substrate 210. When heated to the pre-heating temperature, the device 100 or control circuitry 140 can monitor or determine one or more operational parameters of the dielectric heater module 110 and / or the power consumption of the dielectric heater module 110, in order to determine when a user inhalation takes place, respectively, to detect a user inhalation.P 17560

[0199] FTR4073 29 / 43

[0200] When a user initiates a user inhalation or puff, air at ambient temperature can be drawn from an external environment of the device 100 via the air inlets 161 of the airflow path into the lateral sections 162. The lateral sections 162 of the airflow path 160 pass by the vapor egress surfaces 242 of the liquid transfer elements 220 and pass by the electrodes 114, 116, as shown by the arrows in Figure 2A, such that the drawn air cools the dielectric heater module 110 and / or substrate 210 in the heating zone 222. This leads to a decrease in temperature and hence to an increase in relative permittivity of the substate 210. As a consequence, the capacitance of load capacitors 112 defined or formed by the gaps 115, 117 arranged between the electrodes 114, 117 in circumferential direction increases, and an oscillation frequency of the oscillator circuitry 130 decreases due to the increasing capacitances, and hence increasing LC constant of the oscillator circuitry 130. In addition, the power consumption of the dielectric heater module 110 increases. One or more of these effects, respectively one or more of these changes in the capacitance of the load capacitors 112, the oscillation frequency of the oscillator circuitry 130 and the power consumption can be determined or monitored by the control circuitry 140 in order to detect the onset, start and / or occurrence of the user inhalation.

[0201] Upon detecting the user inhalation, control circuitry 140 can increase the power provided to the dielectric heater module 110 and power it at the second power level, where the dielectric heater module 110 and / or substrate 210 can be heated to the volatilization or vaporization temperature to generate inhalable aerosol. Air drawn through the inlets 161 and lateral sections 162 of the airflow path 160 flows past the vapor egress surfaces 242 of the liquid transfer elements 220, where vapor is released into the airflow. The airflow, enriched with vapor, then flows towards the central interior volume or interior channel 260 of the cartridge 200 via the openings 164, where aerosol can be formed, for example in an aerosolization chamber. The air, enriched with aerosol, can then be drawn into the user’s mouth via the aerosol outlet 215 of the cartridge 200.

[0202] As described with reference to Figure 1 , as soon as the user stops inhaling, the temperature of the dielectric heater module 110 and substrate 210 increases, which leads to a decrease in the relative permittivity of the substrate 210. As a consequence, the capacitances of the load capacitors 112 decrease, the oscillation frequency of the oscillator circuitry 130 increases, and the power consumption of the dielectric heater module 110 decreases. One or more of these changes can be determined or detected by the control circuitry 140, thereby detecting termination of the user inhalation.

[0203] Upon detecting termination of the user inhalation, the control circuitry 140 may cut the power supply to the dielectric heater module 110, and the next or subsequent user inhalation can be determined or detected, as the dielectric heater module 110 and substrate 210 may still have a temperature well above room or ambient temperature. Optionally, however, the control circuitry 140 may power the dielectric heater module 110 at the first power level to ensure that the dielectricP 17560

[0204] FTR4073 30 / 43

[0205] heater module 110 and substrate 210 have at least the pre-heating temperature, in order to allow for cooling by air drawn by the user in the subsequent user inhalation, which can then be detected again by the control circuitry 140.

[0206] Figure 3 is a schematic illustration of an oscillator circuitry 130 for use in the aerosol-forming system 100 of Fig. 1, respectively in a dielectric heater module 110 or dielectric heating arrangement thereof. Oscillator circuitry 130 comprises a switching unit 131 or switching device 131 interconnected with a resonator feedback loop 133 or feedback loop 133 to provide for a selfoscillating signal to the switching device 131. The switching device 131 comprises a single transistor, such as a bipolar junction transistor (BJT) or a field effect transistor (FET). The oscillator circuitry 130 can further comprise a choke 135 that acts on an input to the feedback loop 133 to provide for a stimulation signal, for example a stimulation voltage.

[0207] The oscillator circuitry 130 also comprise a biasing unit 136 acting on the feedback loop 133 for providing a variable or controllable biasing signal, for example a biasing voltage for setting the operating conditions. In the variant shown, the feedback signal can be described as a voltage. The output voltage UOUT of the switching device 131 is coupled to the feedback loop 133 providing a feedback switching signal in the form of a voltage U|Nto the switching device 131. The configuration of the feedback loop 133 is such that the output signal, e.g. the voltage UOUT of the switching device 131 can undergo a phase change and arrives inverted at the input U|Nof the switching device 131 for resonant oscillation. In other configurations, a current could be used as the feedback signal with a switching device 131 comprising a BJT.

[0208] Feedback loop 133 is configured to provide a 180° phase shift from the output UOUT to input U|Nof switching device 131 for oscillation, and in addition, a transistor can be configured for inverting operation.

[0209] As shown in Figure 4, feedback loop 133 includes a resonant circuit 137 comprising the load capacitor 112 providing fora first 90 degrees phase shift or quarter wave shift to the feedback signal. Feedback loop 133 further includes a capacitive element 138 providing for a second 90 degrees phase shift or quarter wave shift to the feedback signal, such that the feedback signal reaching the input of the switching device 131 is inverted and phase-shifted by 180 degrees. Switching device 131 is itself configured for inverted switching operation to provide a 180 degree phase shift between the input U|Nand the output UOUT of the switching device 131.

[0210] Resonant circuit 137 comprises the first and second electrodes 114, 116 of the dielectric heater module 110 or its dielectric heating arrangement, together forming the load capacitor 112. When an aerosol-forming substrate 210 is arranged between the first and second electrodes 114, 116, it forms part of the load capacitor 112. Importantly, the load capacitor 112 is formed in the feedback loop 133, and not at a separate output or part of a separate circuitry that is connected to the switching device 131. This enables a high-frequency oscillating voltage to be created acrossP 17560

[0211] FTR4073 31 / 43

[0212] the electrodes 114, 116 of load capacitor 112, which is needed for sufficient and efficient dielectric heating of the aerosol-forming substrate 210, without having an additional output or circuit to the already resonating feedback loop 133, which would create unnecessary losses and circuit complexity. The resonant circuit 137 may comprise a series resonator circuit or a parallel resonator circuit.

[0213] The feedback loop 133 is configured to be self-oscillating and will oscillate at or close to a given resonance or oscillation frequency determined by the values of the passive components of the feedback loop 133. Since oscillator circuitry 130 is operatively coupled to the control circuitry 140, the control circuitry 140 can determine the oscillation frequency of the oscillator circuitry 130. This enables the control circuitry 140 to determine a change in the oscillation frequency which can be caused by the cooling effect of air drawn by the user in a user inhalation, thereby detecting the user inhalation. Hence, the dielectric heater module 110 can act as puff sensor allowing to detect the user inhalation without requiring a dedicated or separate sensor.

[0214] Further, the switching device 131 can be coupled to one of the electrodes 114, 116 via a transistor 139, which can be configured for inverting operation, for example as an inverting common source Field Effect Transistor (FET), Metal Oxide Field Effect Transistor (MOSFET), or a common emitter Bipolar Junction Transistor (BJT).

[0215] The control circuitry 140 can, for example, be configured to determine the switching frequency of the switching device 131 and / or the switching frequency at a gate terminal of the transistor 139 in order to determine the change in the oscillation frequency of the oscillator circuitry 130, which is indicative of a change in the relative permittivity of the aerosol-forming substrate 210 in the load capacitor 112 caused by the change in temperature, as described in detail herein. Alternatively, or additionally, the control circuitry 140 can determine a frequency of the alternating electric field in the load capacitor 112 in order to determine the change in the oscillation frequency of the oscillator circuity 130 that is caused by the change in the relative permittivity of the aerosol-forming substrate 210 in the load capacitor 112. Hence, the heater module 110 can act as puff sensor allowing to detect the user inhalation without requiring a further sensor.

[0216] The circuits 130, 140 illustrated herein in detail, specifically with reference to Figs. 3 and 4, are mere examples and not intended as a limitation. Specifically, other circuits, specifically other oscillation circuits, can be used, such as forced oscillation circuits, oscillation circuits with or without changing oscillation frequency, and generally any oscillation circuits that can be used to provide an oscillator, amplifier, or optional impedance matching for feeding voltage to the electrodes of the load capacitor.

[0217] Figure 5 shows a perspective view on the body 170 of a dielectric heater module 110 of the aerosol-forming device 100, which encompasses the heating chamber 120 in between theP 17560

[0218] FTR4073 32 / 43

[0219] electrodes 114, 116 arranged on the body wall 171 of the body 170, the body wall 171 serving as a structural base for holding the electrodes 114, 116. Exemplary, the body 170 or body wall 171 is shown herein in a cylindrical shape. Specifically, the body wall 171 forms a hollow cylinder, wherein a virtual base of the cylinder forms the insertion opening 101 for insertion of the aerosolforming article 200. The axis 103, in this case cylinder axis, defines the insertion direction for the aerosol-forming article 200.

[0220] Alternatively, the body 170 or body wall 171 may comprise a cuboid shape suitable for receiving an aerosol-forming article 200 in the form of a cuboid or rectangular parallelepiped article rather than a stick or rod as is the case with the body 170 of Fig. 5. Specifically, the body wall 171 may alternatively form a hollow cuboid and one side of the cuboid may be open to form the insertion opening 101.

[0221] Figure 6 shows an exemplary cross-section of the body 170 of Fig. 5. In this example, there are three pairs of electrodes 114, 116 arranged on the body wall 171 and adjacent to one another. Specifically, in this example there are three pairs of electrodes 114, 116 that are arranged in a concentrical arrangement, which may be extending substantially in parallel to the axis 103. Electrodes 114, 116 of opposite polarity may be neighbouring each other. The pairs of electrodes 114, 116 may be interdigitated. Specifically, the electrodes 114, 116 may be arranged to surround or encompass the heating chamber 120. Further specifically, the adjacent electrodes 114, 116 may be extending in length or with their long sides along or in the direction of axis 103. Transverse or perpendicular to their extension in length, they may be separated from one another by a distance. The distance may be the same or different between all adjacent or directly adjacent electrodes 114, 116. Specifically, the distance between two adjacent or directly adjacent electrodes 114, 116 may be 2 mm or less, or 1 mm or less, for example.

[0222] The distances or gaps between the adjacent electrodes 114, 116 are filled or occupied by low permittivity portions 172 arranged along the body wall 171, specifically along a perimeter thereof or around it. Accordingly, the low permittivity portions 172 are arranged or located in between the adjacent electrodes 114, 116, specifically in between long edges or edge sides thereof extending in length along the axis 103. The long edges may be extending between the body wall 171 and a face of the electrodes 114, 116, the faces of respective pairs of electrodes 114, 116 facing each other.

[0223] Each one of the low permittivity portions 172 may comprise a low relative permittivity material with a lower relative permittivity than a body material of the body wall 171. Specifically, the relative permittivity of the low permittivity portions 172 may be less, specifically at least 30% less or at least 50% less or at least 70% less than a relative permittivity of the body material of the body wall 171. For example, the low permittivity material used inside the low permittivity portion 172 may have a relative permittivity of 5 or less, specifically of 4 or less, of 3 or less, or ofP 17560

[0224] FTR4073 33 / 43

[0225] 2.5 or less. Additionally or alternatively, the low permittivity portions 172 may be gaps, hollow portions, or channels. As gaps or channels, they may be used, serve or designed as air channels for air flow, e.g. from or connected fluidically to the air inlet 161.

[0226] A protective layer 173 may be disposed on the faces of the electrodes 114, 116 for protection of the electrodes 114, 116. Generally, the protective layer 173 may be seen as a layer or part separate from the body wall 171 or as part thereof, meaning that the protective layer 173 is attributed to the body wall 171.

[0227] For example, the protective layer 173 may comprise or be made from glass, in particular quartz glass. Additionally or alternatively, the protective layer 173 may comprise or be made from a ceramic material, specifically a low-dielectric material such as SiO2, diamond-like carbon, DLC, or similar. The ceramic material or generally the material of the protective layer 173 may comprise a low relative permittivity of 4 or lower, of 3 or lower or of 2.5 or lower. Additionally or alternatively, the protective layer 173 may comprise or be made from a Parylene, in particular Parylene N, Polyetherimide (PEI), and / or a Polyaryletherketone (PAEK), material, in particular Polyether ether ketone (PEEK). The protective layer 173 may be disposed onto and / or adhered to the faces of the electrodes 114, 116 by any technique such as but not limited to an atomic layer deposition method, a physical vapor deposition (PVD), chemical vapor deposition (CVD), polymer coating method, or aerosol deposition.

[0228] For example, the protective layer 173 may be a continuous layer extending around the entire axis or along the entire inner circumference of the body wall 171 or a support layer 175 thereof. That is, as further shown in Figures 8 to 13, the body wall 171 may further comprise or be made from a support layer 175, which may be made from the same or different material as the protective layer 173 but generally be thicker in size. Behind the support layer 175 there may be further structure or portions of the body wall 171, for example for containing the oscillation circuitry 130 as exemplary indicated in Figures 8 to 13.

[0229] In any case, the protective layer 173 may enclose the low permittivity portions 172 in between the protective layer 173, the electrodes 114, 116 and the body wall 171 or support layer 175. Alternatively, the protective layer 173 may be multiple layers or in the form of layer segments or sections, which are individually arranged on the faces of the electrodes 114, 116 only but not extend over the permittivity portions 172. In this case or when no protective layer 173 is present, the low permittivity portion 172 may extend freely into or towards the space of the heating chamber 120, meaning that there could be no intermediate element. For example, when the permittivity portions are voids filled with low relative permittivity material such as a fluid, e.g. air, or vacuum, these may be open towards the heating chamber 120. Alternatively, these low permittivity portions may be enclosed by the protective layer 173 or any other inner layer or structure, such as the further or inner body wall 174 seen in Figure 7A.P 17560

[0230] FTR4073 34 / 43

[0231] Figure 7A shows an exemplary cross-section of another variant of a body 170 for the aerosol-forming device 100 than Fig. 6, which in addition to the body wall 171 on the outer side or periphery of the body 170 comprises a further support layer 174 on an inner side or periphery of body 170. Such further support layer 174 may be formed as part of the body wall 171 or separate therefrom. Specifically, the body wall 171 may be comprising an outer support layer 171 relatively further out or away of the heating chamber 120 than the further support layer 174, which may be referred to as an inner support layer 174. Thereby, the electrodes 114, 116 may be supported not only by the outer body wall or support layer 171 as structure or carrier but also by the inner body wall or support layer 174 as additional structure or carrier. Specifically, a type of double-walled cylinder or cuboid body wall 171 may thereby be provided, with the electrodes 114, 116 and low permittivity portions 172 sandwiched in between the walls or layers 171, 174. Also in this example, the optional protective layer 173 may be provided on some or each one of the electrodes 114, 116.

[0232] Generally, it is noted that the body 170 may further comprise any one or more additional walls and / or layers despite not being shown in the Figures. Such walls and layers may serve any purpose that may be relevant within the present context, e.g. structural support, heat insulation, heat reflection, electromagnetic shielding, casing, functional layer with one ore more active or passive components, or similar. For example, there may be explicit heat chamber walls or layers behind the electrodes 114, 116, which may for example be surrounding or arranged to an outer surface of the body wall 171. Such heat chamber walls or layers may provide heat reflection and insulation capabilities. For example, such heat chamber walls or layers may comprise or be made from heat resistive, heat reflective, or heat absorbing materials, thereby reducing the heat transport from inside the heating chamber 120 towards an outside thereof, thereby reducing the risk that a user observes an uncomfortable high temperature when holding the aerosol-forming device. Alternatively, or additionally, an electromagnetic shielding and / or electromagnetic absorption walls or layers may be provided around the body wall 171 or as part thereof. Such walls or layers may for example comprise conductive and / or magnetic material to provide shielding and / or absorption capabilities, specifically but not limited to reflection and / or redirection of electromagnetic radiation towards the heating chamber 120 and / or converting the energy from the electromagnetic radiation into heat. Alternatively, the body wall 171 may be made from or comprise any material as described herein that may provide any of the herein mentioned properties such as structural strength or stiffening, heat shielding, electromagnetic shielding and / or absorption, and similar.

[0233] Figure 7B shows an alternative form factor of body 170 as compared to the cylindrical shape shown in Fig. 7A. In Fig. 7B, the body 170 comprises a body wall 171 that comprises a cuboid shape. Exemplary, there are shown four pairs of electrodes 114, 116 arranged along the innerP 17560

[0234] FTR4073 35 / 43

[0235] surface of the cuboid-shaped body 170. However, there could be more or less. Also, exemplary, the pairs of electrodes 114, 116 are shown to be arranged along long side surfaces of the body wall 171 only, and not on short side surfaces shorter than the long side surfaces located opposite of one another. The side surfaces are the surfaces showing or oriented towards the heating chamber 120. By providing the electrodes 114, 116 on the long side surfaces, the distance between the electrodes 114, 116 is short and allows to generate a strong electric field. Generally, the electrodes 114, 116 may be arranged in parallel or perpendicular to an insertion direction of the article 200 or heating chamber 120, in which it is received. The heating chamber 120 formed inside the body wall 171 has a corresponding cuboid shaped, thereby enabling to receive a tokenshaped aerosol-forming article 200. Adjacent electrodes 114, 116 on the same side surfaces are separated from one another by the low permittivity portions 172. Exemplary, no layers 173, 174, 175 are shown in Fig. 7B as compared to Figs. 6 and 7A. However, any one or more of the layers 173, 174, 175 described with regard to Figs. 6 and 7A may be also applied in the embodiment of Fig. 7B.

[0236] Figure 8 shows a section of a heating chamber 120 in one exemplary configuration of the body 170. Specifically, in this example, the body 170 is shaped as a hollow cuboid with substantially straight or straight body wall 171 and / or support layer 175. Specifically, in this example, a support layer 175 is provided as part of the body wall 171 or body 170. The support layer 175 in this example supports the electrodes 114, 116 thereon or thereat and the low permittivity portion 172 formed inside the protective layer 173 arranged on the electrodes 114, 116, specifically formed in between separate protective layer segments.

[0237] Generally, the support layer 175 may be formed in addition to the body wall 171 or as part thereof. For example, the support layer 175 may be arranged at or adhered or attached to the body wall 171, specifically to an inner side thereof. Alternatively, the support layer 175 may partially or fully form the body wall 171 such that it comprises or is made from the support layer 175. Similarly, further support layer 174 may be arranged on the at least two electrodes 114, 116 and / or on the low permittivity portions 172, specifically as part of or on the body wall 171 as shown exemplary in Fig. 7A. This further support layer 174 may be in addition or as alternative to the protective layer 173.

[0238] For example, the support layer 175 and / or any further support layer 174 may comprise or be made from glass, in particular quartz glass. Additionally or alternatively, they may comprise or be made from a ceramic material, specifically a low-dielectric material such as SiO2, diamondlike carbon, DLC, or similar. The ceramic material or generally the material of the support layer 175 and / or further support layer may comprise a low relative permittivity of 4 or lower, of 3 or lower or of 2.5 or lower. Additionally or alternatively, the support layer 175 and / or further supportP 17560

[0239] FTR4073 36 / 43

[0240] layer may comprise or be made from a Polyetherimide, PEI, and / or a Polyaryletherketone, PAEK, material, in particular Polyether ether ketone, PEEK.

[0241] In Figure 8, the oscillation circuitry 130 is shown with two inductors L1, L2 in connection to the pair of electrodes 114, 116 of an electrode pair. In this example, the oscillation circuitry 130 with inductors L1, L2 is located inside the body 170 and optionally inside the body wall 171 but outside of the support layer 175. Two inductors L1, L2 are only exemplary, for example to illustrate a split-coil type LC feedback loop, but is also possible that only one or more inductors are present.

[0242] Figure 9 shows essentially the same configuration of body 170 with electrodes 114, 116 but in a cylindrical shape of the body 170. Accordingly, the support layer 175, the electrodes 114, 116, and the protective layer 173 have a curved or cylindrical form factor.

[0243] Figures 10 and 11 show another example of a body 170 with a hollow cuboid form factor (Figure 10) and a hollow cylindrical form factor (Figure 11) with therein embedded electrodes 114, 116 forming a heating chamber 120. Different from Figures 8 and 9, in Figures 10 and 11 the low permittivity portion 172 is formed between the protective layers 173 and between the adjacent electrodes 114, 116, specifically edges thereof. The edges in between which the permittivity portion 172 is formed are facing each other.

[0244] Figures 12 and 13 show another example of a body 170 with a hollow cuboid or rectangular parallelepiped form factor (Figure 12) and a hollow cylindrical form factor (Figure 13) with therein embedded electrodes 114, 116 forming a heating chamber 120. Different from Figures 8 to 11, the protective layer 173 is formed on the electrodes 114, 116 and on the support layer 175. The thickness of the protective layer 173 in this case is smaller than the thickness of the electrodes 114, 116. Optionally, the thickness of the protective layer 173 may be constant or uniform along its length or circumference. Thereby, a recess is formed in between the adjacent electrodes 114, 116, which serves as the low permittivity portion 172 in form of a void filled with air and particularly low relative permittivity, including when compared to the support layer 175. The protective layer 173 can be chosen to be very thin to avoid absorbing too much dielectric heating energy, for example less than 200 .m, more preferably less than 100 .m, even more preferably less than 50 .m.

[0245] Figure 14 shows a cross-section of an exemplary aerosol-forming article 200 comprising an aerosol-forming substrate 210. For example, the aerosol-forming substrate 210 may be in liquid form and / or in solid form. In case of a liquid substrate 210, a reservoir or reservoir wall 211 as an article body wall 211 may be provided, which is surrounding or encompassing the liquid substrate 210. Similarly for a solid substrate 210, there may be an article body wall 211 surrounding the solid substrate 210. On that article body wall 211, or alternatively directly on a solid aerosolforming substrate 210, electrodes 114, 116 may be placed opposite of one another. TheP 17560

[0246] FTR4073 37 / 43

[0247] electrodes 114, 116 may extend in parallel to each other along the length of the article 200 and facing each other.

[0248] Due to the cylindrical shape of the aerosol-forming article 200 in Figure 14, which may be a stick-shaped article 200, the electrodes 114, 116 are curved in shape so as to conform to the overall shape. In this example, a low permittivity portion 172 is formed in between the electrodes 114, 116 by virtue of the distance between the edges of the electrodes 114, 116. Additionally, the low permittivity portion 172 extends into the substrate 210 in this example by a void inside the substrate 210, which may for example be filled with air or vacuum. In case of a solid substrate 210, the void may be for example formed by the solid form of the substrate 210. In the case of a liquid substrate 210, the void may for example be formed by the reservoir wall 211.

[0249] As may be seen from Fig. 14, the electrodes 114, 116 and the low permittivity portion 172 are all formed on a perimeter or circumference of the substrate 210 or the article 200. Specifically, in the present case where the substrate 210 is enclosed by article body wall 211, the article body wall 211 may be comprising or forming this perimeter or circumference, at which the electrodes 114, 116 and the low permittivity portion 172 may be arranged or located. In the example of Fig.

[0250] 14 specifically, the electrodes 114, 116 are located outwardly of the article body wall 211, and thereby they are shielded from the heated substrate by the article body wall 211. Alternatively, however, the article body wall 211 may be encompassing or including the electrodes 114, 116, for example. Specifically, the article body wall 211 may comprise one or more layers, such as one or more supporting layers and / or a protective layer similarly to or different from the layers explained with respect to the body 170 of the aerosol-forming device 100. For example, there may be a protective layer, specifically with heat resistive material, between the substrate 210 and the electrodes 114, 116. Additionally or alternatively, there may be one support or carrier layer in addition to or as alternative to the protective layer, to which the electrodes 114, 116 may be attached or where they may be arranged to or at least partially embedded. Similarly, there may be a further support or carrier layer opposite of that one support or carrier layer, such that the electrodes 114, 116 are sandwiched in between support or carrier layers, or in between a support or carrier layer and a protective layer. Accordingly, the electrodes 114, 116 may be integrated into the article body wall 211.

[0251] As previously explained herein, the electrodes 114, 116 may be interconnected with the electrical interconnections 132, 134 as shown in the device of Figure 1, in which case the electrodes 114, 116 of the aerosol-forming device 100 may be omitted. By virtue of the electrodes 114, 116 being in close proximity to the substrate 210 and having the low permittivity portion 172 in between the edges of the adjacent electrodes 114, 116, the dielectric heating zone may be subjected to a high and concentrated heating power for aerosol formation.P 17560

[0252] FTR4073 38 / 43

[0253] Figure 15 shows a cross-section of an alternative aerosol-forming article 200 comprising an aerosol-forming substrate 210. In this example, the aerosol-forming article 200 has a cuboid shape, e.g. in the form of a token article 200. Also, exemplary, the aerosol-forming article 200 in this example comprises two pairs of electrodes 114, 116. A low permittivity portion is formed between the edges of the respectively adjacent electrodes 114, 116 and inside the substrate 210 similar to the example of Figure 14. For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 10% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

[0254] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0255] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

P 17560FTR4073 39 / 43CLAIMS1. A dielectric heater module, comprising:a heating chamber configured to receive an aerosol-forming article having an aerosolforming substrate;a dielectric heating arrangement including an oscillation circuitry and at least two electrodes forming a load capacitor of the oscillation circuit for removably receiving and dielectrically heating the aerosol-forming substrate that is arranged at least partially inside the heating chamber; anda body encompassing the heating chamber, the body comprising a body wall, the at least two electrodes, and a low permittivity portion, wherein the electrodes and the low permittivity portion are arranged along the body wall,wherein the low permittivity portion is arranged between the at least two electrodes, and wherein the low permittivity portion comprises a low relative permittivity material with a lower relative permittivity than a body material of the body wall and is exposed towards the heating chamber.

2. The dielectric heater module of claim 1 , wherein the electrodes are covered by a protective layer such that the electrodes are not exposed towards the heating chamber.

3. The dielectric heater module of claim 1 or 2, wherein the low relative permittivity material has at least 30% less relative permittivity than the body material.

4. The dielectric heater module of any one of the previous claims, wherein the low permittivity material has a relative permittivity below 5, in particular below 4, further in particular below 3.

5. The dielectric heater module of any one of the previous claims, wherein the low permittivity portion comprises a void inside the body wall, the void filled with the low relative permittivity material, and the low relative permittivity material being a fluid, in particular air, or vacuum.

6. The dielectric heater module of any one of the previous claims, wherein the body wall comprises an opening for inserting the aerosol-forming article such that the substrate is at least partially arranged inside the heating chamber.

7. The dielectric heater module of claim 6, wherein:P 17560FTR4073 40 / 43the body wall forms a hollow cylinder, a virtual base of the cylinder forming the opening, a cylinder axis defining an insertion direction for the aerosol-forming article; orbody wall forms a hollow cuboid, one side of the cuboid being open to form the opening.

8. The dielectric heater module of any one of the previous claims, wherein the body wall comprises a support layer supporting the at least two electrodes and the low permittivity portion, and wherein the body wall comprises a protective layer or a further support layer arranged on the at least two electrodes and / or on the low permittivity portion.

9. The dielectric heater module of claim 8, wherein the protective layer has a thickness of less than 0.4 mm, in particular less than 0.3 mm, and further in particular less than 0.2 mm.

10. The dielectric heater module of claim 8 or 9, wherein the protective layer or further support layer surrounds the heating chamber, and the support layer surrounds the protective layer or further support layer.

11. The dielectric heater module of any one of claims 8 to 10, wherein:the protective layer or the further support layer is separated by the low permittivity portion; orthe low permittivity portion is provided in a recess of the protective layer or the further support layer between the at least two electrodes, the recess being open towards the heating chamber.

12. The dielectric heater module of any one of claims 8 to 11, wherein the support layer, the protective layer, and / or the further support layer comprises one or more of:Parylene, in particular Parylene N;glass, in particular quartz glass;a ceramic;Polyetherimide, PEI; anda Polyaryletherketone, PAEK, material, in particular Polyether ether ketone, PEEK.

13. The dielectric heater module of any one of the previous claims, wherein the at least two electrodes are located adjacent to one another and extending substantially in parallel to each other, and wherein the low permittivity portion is arranged in between the adjacent at least two electrodes, wherein a distance between the adjacently located at least two electrodes is 2 mm or less, in particular 1 mm or less.P 17560FTR4073 41 / 4314. The dielectric heater module of any one of the previous claims, wherein the oscillation circuit comprises a switching unit and a feedback loop connected to the switching unit, the feedback loop comprising two electric contacts interconnected with the electrodes.

15. The dielectric heater module of any one of the previous claims, wherein the dielectric heater module comprises two to eight pairs of interdigitated electrodes, wherein each one of the electrodes is arranged along the circumference of the body wall, wherein the body wall comprises four to sixteen low permittivity portions, and wherein each one of the low permittivity portions is arranged between adjacent electrodes of the pairs of electrodes.

16. An aerosol-forming system, comprising the dielectric heater module of any one of the previous claims and an aerosol-forming article comprising an aerosol-forming substrate.

17. An aerosol-forming article comprising an aerosol-forming substrate, at least two electrodes, and a low permittivity portion, wherein the aerosol-forming substrate is arranged in between the at least two electrodes, and wherein the at least two electrodes and the low permittivity portion are arranged along a perimeter of the aerosol-forming article, and wherein the low permittivity material is arranged in between the at least two electrodes on the perimeter of the aerosol-forming article.

18. The aerosol-forming article of claim 17, wherein the two electrodes and the low permittivity portion are arranged at or inside an article body wall of an article body of the aerosol-forming article.

19. The aerosol-forming device of claim 17 or 18, wherein the article body wall comprises a cylindrical shape or cuboid shape.

20. The aerosol-forming article of any one of claims 17 to 19, wherein the low permittivity material has a relative permittivity below 5, in particular below 4, further in particular below 3.

21. The aerosol-forming article of any one of claims 17 to 20, wherein the low permittivity material has a relative permittivity lower than the aerosol-forming substrate or the article body wall.

22. The aerosol-forming article of any one of claims 17 to 21, wherein the low permittivity portion comprises a void, in particular inside the substrate and / or the article body wall, the voidP 17560FTR4073 42 / 43filled with the low relative permittivity material, and the low relative permittivity material being a fluid or vacuum.

23. The aerosol-forming article of any one of claims 17 to 22, wherein the low relative permittivity material is air.

24. The aerosol-forming article of any one of claims 17 to 23, wherein the void is open towards a surrounding of the aerosol-forming article or a surrounding of the article body wall.

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