WO2019138042A1

WO2019138042A1 - An aerosol-generating device, system and heating element having plasmonic properties

Info

Publication number: WO2019138042A1
Application number: PCT/EP2019/050644
Authority: WO
Inventors: Rui Nuno BATISTA; Chiara FASCIANI
Original assignee: Philip Morris Products S.A.
Priority date: 2018-01-12
Filing date: 2019-01-11
Publication date: 2019-07-18

Abstract

An aerosol-generating device (100) comprising: a cavity (140) for receiving at least part of an aerosol-forming substrate (132); and a heating element (120) for heating an aerosol-forming substrate when the aerosol-forming substrate is received within the cavity (140). The heating element (120) comprises a heating surface having a plurality of metallic nanoparticles arranged to receive ambient light from a light source external to the device and generate heat by surface plasmon resonance.

Description

AN AEROSOL-GENERATING DEVICE, SYSTEM AND HEATING ELEMENT HAVING

PLASMONIC PROPERTIES

The present invention relates to an aerosol-generating device for heating an aerosol- forming substrate to generate an aerosol, and a heating element for the aerosol-generating device, having plasmonic properties. The present invention also relates to an aerosol- generating system comprising the aerosol-generating device.

A number of electrically-operated aerosol-generating systems in which an aerosol- generating device having an electric heating element is used to heat an aerosol-forming substrate, such as a tobacco plug, have been proposed in the art. One aim of such aerosol- generating systems is to reduce known harmful smoke constituents of the type produced by the combustion and pyrolytic degradation of tobacco in conventional cigarettes. The aerosol- forming substrate may be provided as part of an aerosol-generating article which is inserted into a chamber or cavity in the aerosol-generating device. In some known systems, to heat the aerosol-forming substrate to a temperature at which it is capable of releasing volatile components that may form an aerosol, a resistive heating element is inserted into or around the aerosol-forming substrate when the article is received in the aerosol-generating device.

Other known electrically operated aerosol-generating systems are configured to heat a liquid aerosol-forming substrate, such as a nicotine-containing liquid. Such systems typically comprise a wick arranged to transport liquid aerosol-forming substrate from a storage portion and a resistive heating element coiled around a portion of the wick.

A number of electrically-operated aerosol-generating systems comprising inductive heating systems have also been proposed.

However, heating systems in known aerosol-generating systems exhibit a number of disadvantages. For example, when using resistive heating elements, it may be difficult to achieve homogenous heating of an aerosol-generating substrate. Accurate temperature control is another disadvantage commonly associated with resistive heaters. The assembly process for resistive heating elements may also lead to resistive losses in the heating element circuit, for example at soldered connections between a resistive heating track and a power supply circuit.

Inductive heating systems also have their own disadvantages. For example, achieving efficient inductive heating of a susceptor element while minimising a power supply to an inductor coil requires positioning of the inductor coil as close to the susceptor element as possible. This may make it difficult to design an inductively heated aerosol-generating system that is efficient as well as practical to manufacture and use. Efficient power consumption may also be a concern for heating systems in known aerosol-generating systems.

Accordingly, it would be desirable to provide an aerosol-generating device comprising a heating arrangement that mitigates or overcomes at least some of these disadvantages with known devices.

According to a first aspect of the present invention there is provided an aerosol- generating device comprising: a cavity for receiving at least part of an aerosol-generating substrate; and a heating element for heating the aerosol-generating substrate when the aerosol-generating substrate is received within the cavity, wherein the heating element comprises a heating surface having a plurality of metallic nanoparticles arranged to receive ambient light from a light source external to the device and generate heat by surface plasmon resonance.

As used herein, the term“surface plasmon resonance” refers to a collective resonant oscillation of free electrons of the metallic nanoparticles and thus polarization of charges at the surface of the metallic nanoparticles. The collective resonant oscillation of the free electrons and thus polarisation of charges is stimulated by light incident on the metallic nanoparticles from a light source. Energy from the oscillating free electrons may be dissipated by several mechanisms, including heat. Therefore, when the metallic nanoparticles are irradiated with a light source, the metallic nanoparticles generate heat by surface plasmon resonance.

As used herein, the term“metallic nanoparticles” refers to metallic particles having a maximum diameter of about 1 micrometre or less. Metallic nanoparticles that generate heat by surface plasmon resonance when excited by incident light may also be known as plasmonic nanoparticles.

Advantageously, the first aspect of the present invention comprises a heating surface having a plurality of metallic nanoparticles arranged to receive ambient light from a light source external to the device and generate heat by surface plasmon resonance. Using surface plasmon resonance to provide heat in an aerosol-generating device has a number of advantages in its own right. For example, the provision of such a feature means that it is not necessary to electrically connect the heating element to a power supply. Advantageously, a heating element that is not electrically connected to a power supply may simplify manufacture of the aerosol-generating device. Advantageously, a heating element that is not electrically connected to a power supply may facilitate servicing of the heating element, replacement of the heating element, or both.

Advantageously, a heating element arranged to generate heat by surface plasmon resonance may provide more homogenous heating of an aerosol-forming substrate when compared to resistive and inductive heating systems. For example, the free electrons of the metallic nanoparticles are excited to the same extent regardless of an angle of incidence of incident light.

Advantageously, a heating element arranged to generate heat by surface plasmon resonance may provide more localised heating when compared to resistive and inductive heating systems. Advantageously, localised heating facilitates heating of discrete portions of an aerosol-forming substrate or a plurality of discrete aerosol-forming substrates. Advantageously, localised heating increases the efficiency of the aerosol-generating device by increasing or maximising the transfer of heat generated by the heating element to an aerosol-forming substrate. Advantageously, localised heating may reduce or eliminate undesired heating of other components of the aerosol-generating device.

The heating element of the first aspect of the present invention is particularly advantageous because the heating element is arranged to generate heat when it receives ambient light. This has a number of advantages. Firstly, the ambient light may be used to fully power the heating element. This may mean that no internal power source is required in the device for the heating element. Alternatively or additionally, the ambient light may be used to provide supplementary power to the heating element. This may help to reduce the rate of consumption of an internal power source within the device, such as the rate of consumption of an internal battery. The ambient light may also help to keep the heating element at or above a certain temperature. That is, the ambient light may help to prevent the heating element from dropping below a certain temperature. This may be particularly advantageous when seeking to pre-heat an aerosol-forming substrate to an elevated temperature prior to operating the device.

The aerosol-generating device may comprise a main body comprising the cavity, and heating element may be permanently attached to the main body of the device and at least partially disposed within the cavity. This may advantageously help to simplify the interaction that a user may need to have with the device in order to use it.

The aerosol-generating device may comprise a main body comprising the cavity, and heating element may be releasably attachable to the main body of the device, such that the heating element is movable between: an attached position, in which the heating element is attached to the main body of the device and at least partially disposed within the cavity; and a detached position, in which the heating element is detached from the main body of the device and disposed external to the cavity. This may advantageously allow for improved cleaning of one or both of the heating element and the cavity. This may advantageously enable the heating element to be easily replaced; for example if it has become damaged, or if a consumer wishes to customise the heating element that they use for their device. Where the heating element is releasably attachable to the main body of the, the aerosol-generating device preferably comprises a mechanism for attaching the heating element to at least a portion of the device which forms the cavity. The mechanism may be formed on one or both of the heating element and the main body of the device.

Where the aerosol-generating device comprises a main body and the heating element is releasably attachable to the main body of the device, the heating element may supplied to the consumer in the attached position or in the detached position.

The heating element may comprise an elongate body having a first end, a second end, and one or more walls extending from the first end to the second end to define a light chamber within the elongate body. The elongate body may have any suitable cross-sectional shape, such as a circular, oval, square, or triangular shaped cross-section. For example, the elongate body of the heating element may consist of a single cylindrical wall extending from the first end to the second end. In this example, the elongate body will have a substantially circular or oval cross-sectional shape. As another example, the elongate body of the heating element may consist of four identical walls extending from the first end to the second end. In this example, the elongate body may have a substantially square or rectangular cross-sectional shape.

Preferably, an inner surface of the one or more walls of the elongate body comprises the heating surface. The heating surface may extend across the entire inner surface of the one or more walls, or the heating surface may only extend across one or more portions of the inner surface of the one or more walls. The outer surface of the one or more walls of the elongate body may be arranged to contact an aerosol-forming substrate when the aerosol- forming substrate is received within the cavity. The elongate body may be arranged such that ambient light is received from the light source external to the device through the first end of the elongate body.

The cavity may have any suitable configuration. The cavity preferably comprises an opening, a base, and one or more longitudinally extending side walls extending from the opening of the cavity to the base of the cavity. The opening, the base, and the one or more longitudinally extending side walls may define the boundary of the cavity. The cavity may define the volume of space within the device for receiving an aerosol-forming substrate.

At least part of the heating element may be positioned within the cavity. At least part of the heating element may extend into the cavity. Therefore, the heating element may further define a portion of the boundary of the cavity. That is, the heating element may at least partially define the cavity so that, when an aerosol-forming substrate is received within the cavity, at least part of the aerosol-forming substrate is received adjacent the heating element. For example, where the heating element comprises an elongate body, the outer surface of the wall of the elongate body may further define a portion of the boundary of the cavity. By way of example, if the cavity has a cylindrical longitudinally extending side wall, and the wall of the heating element is also cylindrical, then a substantially annular-shaped volume of space may be defined in the cavity for receiving an aerosol-forming substrate. It will be appreciated that other shaped volumes of space may be defined in the cavity, by selection of suitable shapes for the one or more walls of the cavity and the wall of the heating element.

The aerosol-generating device may comprise a housing. The housing may comprise a first part defining a main body of the device and a second part which is releasably attachable to the main body of the aerosol-generating device. The opening of the cavity may be defined by an opening in the housing of the aerosol-generating device.

In some embodiments, the opening of the cavity may be provided in the first part of the housing which defines the main body of the device.. In this case, the cavity may extend into the main body of the aerosol-generating device.

In some embodiments the opening of the cavity may be provided in the second part of the housing. In this case, the cavity may extend into the second part of the housing. In such embodiments, the second part of the housing may comprise a casing member, which is configured to extend over the heating element, and attach to the main body of the aerosol- generating device. Such a casing member may advantageously help to protect the heating element, for example when the device is not in use. Such a casing member may also help to make it easier to clean components of the device, such as the heating element. The casing member may therefore be arranged to at least partially enclose the heating element, and more preferably fully enclose the heating element when the casing member is attached to the main body of the aerosol-generating device.

The casing member may comprise: a first end; a second end defining the opening of the cavity for receiving the heating element; and one or more walls extending from the first end to the second end. The one or more walls preferably comprises a single cylindrical wall. The second end of the casing member may be attachable to the main body of the aerosol- generating device. The first end of the casing member may be arranged to permit ambient light to enter the light chamber of the heating element through the first end of the heating element, when the casing member is attached to the main body of the device and extends over the heating element. The first end of the casing member may comprise an optical component for increasing the amount of ambient light receivable through the first end of the casing member. The optical component may have any of the features described below in reference to an optical component which may be provided at the first end of the elongate body of the heating element.

The heating element of the first aspect of the present invention comprises a heating surface having a plurality of metallic nanoparticles arranged to receive ambient light from a light source external to the device. This light source is referred to herein as“the ambient light source”. The heating element may also be arranged to receive light from a light source, which is provided as part of the aerosol-generating device. This light source is referred to herein as “the device light source” or“the light source of the aerosol-generating device”.

Accordingly, preferably the aerosol-generating device comprises a device light source for providing light to the plurality of metallic nanoparticles. Where the device comprises the device light source and the heating element comprises the elongate body, the elongate body is preferably arranged such that light from the device light source is received through the second end of the elongate body.

Where the aerosol-generating device comprises a main body, the device light source may be provided as part of the main body, or may be provided as part of the heating element. Where the heating element is releasably attachable to the main body of the device, the device light source may be provided as part of the main body of the device. This may be advantageous if the device light source does not need to be replaced as often as the heating element.

In such embodiments, the device light source is preferably provided at the base of the cavity. This may help to minimise the distance for light to travel from the device light source to the plurality of metallic nanoparticles of the heating element. Alternatively, the device light source may be spaced apart from the cavity in the main body of the device, and the aerosol- generating device may comprise one or more optical components for facilitating transmission of light from the device light source to the plurality of metallic nanoparticles of the heating element.

Where the aerosol-generating device comprises a main body and the heating element is releasably attachable to the main body of the device, the device light source may be provided as part of the releasably attachable heating element. This may be advantageous if a specific relationship is desired between the device light source and the plurality of metallic nanoparticles of the heating surface of the heating element, such as a specific relationship between the wavelength of light emitted by the device light source and composition of the plurality of metallic nanoparticles. The device light source may be provided at the second end of the elongate body of the heating element.

Where the device light source is provided as part of the releasably attachable heating element, the heating element preferably comprises one or more electrical contacts for electrically connecting the device light source to a supply of electrical power in the main body of the device. The one or more electrical contacts of the releasably attachable heating element are preferably provided at the second end of the elongate body of the heating element. Preferably, the base of the cavity of the device comprises one or more electrical contacts for connecting to the one or more electrical contacts of the releasably attachable heating element.

Where the heating element comprises an elongate body having a light chamber, preferably, the aerosol-generating device further comprises an optical element disposed within the light chamber of the elongate body of the heating element. The optical element is preferably arranged to divert ambient light received through the first end of the substantially cylindrical body towards the heating surface.

Where the aerosol-generating device comprises a device light source for providing light to the plurality of metallic nanoparticles, the optical element is preferably arranged to divert light received from the device light source through the second end of the substantially cylindrical body towards the heating surface.

The optical element may therefore be advantageously used to influence the light that is received by the plurality of metallic nanoparticles of the heating element, from one or both of the ambient light source and the device light source. In particular, the optical element may be used to influence the total amount of light that is received by the plurality of metallic nanoparticles, or control the amount of light that is received by one or more portions of the plurality of metallic nanoparticles on the heating surface, or both. This may help to improve properties of heat generated by surface plasmon resonance with the heating element.

The optical element may divide the light chamber of the heating element into a first portion and a second portion. The first portion may be arranged to receive light from the ambient light source. The second portion may be arranged to receive light from the device light source. The optical element may comprise a light transmissive substrate. The light transmissive substrate is preferably arranged to transmit light having a wavelength of between about 495 nanometres and about 580 nanometres. The light transmissive substrate may comprise glass or plastic.

Preferably, the optical element is substantially conical shaped element comprising a light transmissive substrate. In some embodiments, the optical element is substantially conical shaped, with the wider end of the optical element being disposed towards the first end of the elongate body of the heating element. In such embodiments, the conical shape of the optical element may be used to divert ambient light received through the first end of the elongate body towards the inner surface of the one or more walls of the elongate body.

In some embodiments, the optical element is substantially conical shaped, with the wider end of the optical element being disposed towards the second end of the elongate body of the heating element. Such embodiments may be particularly advantageous when the second end of the elongate body of heating element is arranged to receive light from a device light source. In particular, the conical shape of the optical element may be used to divert ambient light received through the first end of the elongate body towards the inner surface of the one or more walls of the elongate body, as well as diverting light received from the device light source through the second end of the elongate body towards the inner surface of the one or more walls of the elongate body.

The optical element disposed in the light chamber may be arranged to permit one-way light transmission. For example, the optical element may comprise a light transmissive substrate having a reflective layer on one side of the substrate. The reflective layer may be used to prevent light from passing from the reflective layer side of the substrate to the other side of the substrate. However, the reflective layer may still permit light to pass from the other side of the substrate to the reflective layer side of the substrate. The reflective layer may comprise one or more layers. At least one of the layers may comprise metal.

An optical element having one-way light transmission properties may be particularly advantageous when ambient light is arranged to enter a first portion of the light chamber from the first end of the elongate body, and light from a device light source is arranged to enter a second portion of the light chamber from the second end of the elongate body. This is because, in such embodiments, there may be times when it is desirable to not power up the device light source, and thus only make use of ambient light for surface plasmon resonance. For example, it may be desirable to preserve power and only make use of ambient light when seeking to pre-heat an aerosol-forming substrate to an elevated temperature prior to operating the device.

At such times, in order to maximise the amount of ambient light received by the heating surface, the optical element is preferably arranged to prevent ambient light from passing from the first portion of the light chamber into the second portion of the light chamber. The optical element may instead reflect such ambient light towards the plurality of metallic nanoparticles of the heating surface and thus enhance the ambient light’s contribution towards surface plasmon resonance.

Preferably, the second end of the elongate body is provided with at least one lens for directing light which enters the light chamber through the second end of the elongate body towards the heating surface. In embodiments where the elongate body comprises at least one lens at its second end and a conical shaped optical element disposed within the light chamber, the wider end of the optical element is preferably disposed towards the first end of the elongate body of the heating element. That is the narrower end of the conical shaped optical element is preferably disposed towards the second end of the elongate body of the heating element. The narrower end of the conical shaped optical element may be disposed at the second end of the elongate body of the heating element in contact with the at least one lens.

Preferably, the first end of the elongate body of the heating element is provided with mechanism for controlling the amount of light which may pass through the first end of the elongate body.

In some embodiments, the mechanism at the first end of the heating element comprises a one-way light transmissive optical element. This may allow ambient light to enter the light chamber through the first end of the elongate body, whilst also preventing light from exiting the light chamber through the first end of the elongate body. This may be particularly advantageous in embodiments where a device light source transmits light into the light chamber from the second end of the elongate body, because the one-way light transmissive optical element may prevent such light from escaping through the first end of the elongate body. This may be particularly advantageous if the light produced by the light source could cause harm or discomfort if viewed by a user of the device.

In some embodiments, the mechanism at the first end of the heating element comprises a mechanism for restricting the amount of light which may pass into the light chamber of the heating element through the first end of the elongate body. The mechanism may be a mechanically controllable mechanism, such as one or both of a shutter and an iris. The mechanism may be electrically controllable. For example, the mechanism may comprise a substrate whose light transmission properties are altered when a voltage is applied to the substrate. Examples of such mechanisms include electrochromic devices, polymer dispersed liquid crystal devices, and nanocrystal devices.

The mechanism may be configured to selectively control the total amount of light, such as the total luminous flux, which may pass into the light chamber of the heating element through the first end of the elongate body. For example the mechanism may comprise an iris.

The mechanism may be configured to selectively control the type of light, which may pass into the light chamber of the heating element through the first end of the elongate body. For example, the mechanism may be configured to selectively filter out certain types of light, and prevent these from passing into the light chamber of the heating element through the first end of the elongate body. The mechanism may filter light based on properties such as wavelength and polarization.

Preferably, the heating element further comprises an optical component affixed to the first end of the elongate body for increasing the amount of ambient light receivable through the first end of the elongate body. Preferably, the optical component is arranged to guide ambient light towards the first end of the elongate body. The optical component preferably comprises a bulbous light transmissive substrate extending from the first end of the elongate body. The bulbous light transmissive substrate preferably comprises glass or plastic.

Arranging for the plurality of metallic nanoparticles to be able to receive light from a light source, which is provided as part of the aerosol-generating device, in addition to being able to receive ambient light from a light source external to the device, may be particularly advantageous. For example, providing the aerosol-generating device with a light source may advantageously allow the heating element to generate heat without receiving light from an external light source. Advantageously, providing the aerosol-generating device with a light source may provide improved control of the illumination of the heating element. Advantageously, controlling the illumination of the heating element controls the temperature to which the heating element is heated by surface plasmon resonance.

The device light source may be configured to emit at least one of ultraviolet light, infrared light and visible light. Preferably, the device light source is configured to emit visible light. Advantageously, a device light source configured to emit visible light may be inexpensive, convenient to use, or both.

Preferably, the device light source is configured to emit light comprising at least one wavelength between 380 nanometres and 700 nanometres.

Preferably, the device light source is configured for a peak emission wavelength of between about 495 nanometres and about 580 nanometres. As used herein,“peak emission wavelength” refers to the wavelength at which a light source exhibits maximum intensity. Advantageously, a peak emission wavelength of between about 495 nanometres and about 580 nanometres may provide maximum heating of the heating element by surface plasmon resonance, particularly when the plurality of metallic nanoparticles comprises at least one of gold, silver, platinum, and copper.

The device light source may comprise at least one of a light emitting diode and a laser. Advantageously, light emitting diodes and lasers may have a compact size suited to use in an aerosol-generating device. In embodiments in which the device light source comprises at least one laser, the at least one laser may comprise at least one of a solid state laser and a semiconductor laser.

The device light source may comprise a plurality of light sources. The plurality of light sources may be the same type of light source. At least some of the plurality of light sources may be different types of light source. The plurality of light sources may comprise any combination of the types of light source described herein.

Advantageously, a plurality of light sources may facilitate customisation of a heating profile generated by the aerosol-generating device during use. At least one of the plurality of light sources may be a primary light source and at least one of the plurality of light sources may be a backup light source. The aerosol-generating device may be configured to emit light from one or more backup light sources only when one or more of the primary light sources is inoperative.

At least one of the plurality of light sources may be arranged to irradiate only a portion of the plurality of metallic nanoparticles. Each of the plurality of light sources may be arranged to irradiate a different portion of the plurality of metallic nanoparticles.

The aerosol-generating device may be configured so that the plurality of light sources irradiate different portions of the plurality of metallic nanoparticles at the same time. Advantageously, irradiating different portions of the plurality of metallic nanoparticles at the same time may facilitate homogenous heating of the heating element. Advantageously, irradiating different portions of the plurality of metallic nanoparticles at the same time may facilitate simultaneous heating of a plurality of discrete aerosol-forming substrates.

The aerosol-generating device may be configured so that the plurality of light sources irradiate different portions of the plurality of metallic nanoparticles at different times. Advantageously, irradiating different portions of the plurality of metallic nanoparticles at different times may facilitate heating of different portions of an aerosol-forming substrate at different times. Advantageously, irradiating different portions of the plurality of metallic nanoparticles at different times may facilitate heating of a plurality of discrete aerosol-forming substrates at different times.

Preferably, the aerosol-generating device comprises an electrical power supply and a controller configured to supply electrical power from the electrical power supply to the light source.

In embodiments in which the aerosol-generating device comprises a plurality of light sources, the electrical power supply may comprise a single source of electrical power arranged to supply electrical power to the plurality of light sources.

In embodiments in which the aerosol-generating device comprises a plurality of light sources, the electrical power supply may comprise a plurality of sources of electrical power arranged to supply electrical power to the plurality of light sources.

Preferably, the aerosol-generating device comprises a user input device. The user input device may comprise at least one of a push-button, a scroll-wheel, a touch-button, a touch-screen, and a microphone. Advantageously, the user input device allows a user to control one or more aspects of the operation of the aerosol-generating device. In embodiments in which the aerosol-generating device comprises a light source, a controller and an electrical power supply, the user input device may allow a user to activate a supply of electrical power to the light source, to deactivate a supply of electrical power to the light source, or both.

In embodiments in which the controller is configured to selectively supply electrical power to at least some of a plurality of light sources, preferably the controller is configured to selectively supply electrical power to at least some of the plurality of light sources in response to a user input received by the user input device.

In embodiments in which the controller is configured to selectively vary a supply of electrical power to at least some of a plurality of light sources, preferably the controller is configured to selectively vary a supply of electrical power to at least some of the plurality of light sources in response to a user input received by the user input device.

The electrical power supply may comprise a DC power supply. The electrical power supply may comprise at least one battery. The at least one battery may include a rechargeable lithium ion battery. The electrical power supply may comprise another form of charge storage device such as a capacitor. The electrical power supply may require recharging. The electrical power supply may have a capacity that allows for the storage of enough energy for one or more uses of the aerosol-generating device. For example, the electrical power supply may have sufficient capacity to allow for the continuous generation of aerosol for a period of around six minutes, corresponding to the typical time taken to smoke a conventional cigarette, or for a period that is a multiple of six minutes. In another example, the electrical power supply may have sufficient capacity to allow for a predetermined number of puffs or discrete activations.

The controller may be configured to commence a supply of electrical power from the electrical power supply to the device light source at the start of a heating cycle. The controller may be configured to terminate a supply of electrical power from the electrical power supply to the device light source at the end of a heating cycle.

The controller may be configured to provide a continuous supply of electrical power from the electrical power supply to the device light source.

The controller may be configured to provide an intermittent supply of electrical power from the electrical power supply to the device light source. The controller may be configured to provide a pulsed supply of electrical power from the electrical power supply to the device light source.

Advantageously, a pulsed supply of electrical power to the device light source may facilitate control of the total output from the device light source during a time period. Advantageously, controlling a total output from the light source during a time period may facilitate control of a temperature to which the heating element is heated by surface plasmon resonance. Advantageously, a pulsed supply of electrical power to the device light source may increase thermal relaxation of free electrons excited by surface plasmon resonance compared to other relaxation processes, such as oxidative and reductive relaxation. Therefore, advantageously, a pulsed supply of electrical power to the light source may increase heating of the heating element. Preferably, the controller is configured to provide a pulsed supply of electrical power from the electrical power supply to the device light source so that the time between consecutive pulses of light from the light source is equal to or less than about 1 picosecond. In other words, the time between the end of each pulse of light from the light source and the start of the next pulse of light from the light source electrical power is equal to or less than about 1 picosecond.

The controller may be configured to vary the supply of electrical power from the electrical power supply to the device light source. In embodiments in which the controller is configured to provide a pulsed supply of electrical power to the device light source, the controller may be configured to vary a duty cycle of the pulsed supply of electrical power. The controller may be configured to vary at least one of a pulse width and a period of the duty cycle.

The aerosol-generating device may comprise a temperature sensor. The temperature sensor may be arranged to sense a temperature of at least one of the heating element and an aerosol-forming substrate during use of the aerosol-generating device. The aerosol- generating device may be configured to vary a supply of electrical power to the device light source in response to a change in temperature sensed by the temperature sensor. In embodiments in which the aerosol-generating device comprises an electrical power supply and a controller, preferably the controller is configured to vary the supply of electrical power from the electrical power supply to the device light source in response to a change in temperature sensed by the temperature sensor.

The aerosol-generating device may comprise one or more optical elements to facilitate the transmission of light from a light source, such as the ambient light source or the device light source, to the heating element. The one or more optical elements may include at least one of an aperture, a window, a lens, a reflector, and an optical fibre.

The plurality of metallic nanoparticles may comprises at least one of gold, silver, platinum, copper, palladium, aluminium, chromium, titanium, rhodium, and ruthenium. The plurality of metallic nanoparticles may comprise at least one metal in elemental form. The plurality of metallic nanoparticles may comprise at least one metal in a metallic compound. The metallic compound may comprise at least one metal nitride. Preferably, the plurality of metallic nanoparticles comprises at least one of gold, silver, platinum, and copper. Advantageously, gold, silver, platinum, and copper nanoparticles may exhibit strong surface plasmon resonance when irradiated with visible light.

The plurality of metallic nanoparticles may comprise a single metal. The plurality of metallic nanoparticles may comprise a mixture of different metals.

The plurality of metallic nanoparticles may comprise a plurality of first nanoparticles comprising a first metal and a plurality of second nanoparticles comprising a second metal.

At least some of the plurality of metallic nanoparticles may each comprise a mixture of two or more metals. At least some of the plurality of metallic nanoparticles may comprise a metal alloy. At least some of the plurality of metallic nanoparticles may each comprise a core- shell configuration, wherein the core comprises a first metal and the shell comprises a second metal.

In embodiments in which the aerosol-generating device comprises a light source, preferably the plurality of metallic nanoparticles comprises a number average maximum diameter that is less than or equal to the peak emission wavelength of the device light source.

The plurality of metallic nanoparticles may comprise a number average maximum diameter of less than about 700 nanometres, preferably less than about 600 nanometres, preferably less than about 500 nanometres, preferably less than about 400 nanometres, preferably less than about 300 nanometres, preferably less than about 200 nanometres, preferably less than about 150 nanometres, preferably less than about 100 nanometres.

The heating element may be formed from the plurality of metallic nanoparticles.

The heating element may comprise a substrate layer and a coating layer positioned on at least a portion of the substrate layer, wherein the coating layer comprises the plurality of metallic nanoparticles. Advantageously, the substrate layer may be formed from a material selected for desired mechanical properties. Advantageously, the coating layer may be formed to optimise the surface plasmon resonance of the plurality of metallic nanoparticles when the coating layer is exposed to light from a light source, such as the ambient light source or the device light source.

The substrate layer may be formed from any suitable material. The substrate layer may comprise a metal. The substrate layer may comprise a polymeric material. The substrate layer may comprise a ceramic.

The substrate layer may be electrically conductive. The substrate layer may be electrically insulating.

The coating layer may be provided on the substrate layer using any suitable process. The coating layer may be formed by depositing the plurality of metallic nanoparticles on the substrate layer using a physical vapour deposition process. The coating layer may be a substantially continuous layer.

The coating layer may comprise a plurality of discrete areas of metallic nanoparticles, wherein the plurality of discrete areas are spaced apart from each other on the substrate layer. Advantageously, a plurality of discrete areas of metallic nanoparticles may facilitate heating of a plurality of discrete portions of an aerosol-forming substrate. Advantageously, a plurality of discrete areas of metallic nanoparticles may facilitate heating of a plurality of discrete aerosol- forming substrates.

The aerosol-generating device may comprise a light source arranged to irradiate a plurality of the discrete areas of metallic nanoparticles. The aerosol-generating device may comprise a plurality of light sources arranged to irradiate the plurality of discrete areas of metallic nanoparticles. Each of the plurality of light sources may be arranged to irradiate only one of the discrete areas of metallic nanoparticles.

The heating element may comprise an electrically resistive portion arranged to receive a supply of electrical power. During use, a supply of electrical power to the electrically resistive portion may resistively heat the electrically resistive portion. Advantageously, the electrically resistive portion may provide a source of heat in addition to heat generated by surface plasmon resonance of the plurality of metallic nanoparticles.

The plurality of metallic nanoparticles may form the electrically resistive portion.

In embodiments in which the heating element comprises a substrate layer and a coating layer, at least one of the substrate layer and the coating layer may form the electrically resistive portion. The substrate layer may comprise an electrically resistive material. The electrically resistive material may comprise at least one of an electrically resistive metal and an electrically resistive ceramic. The substrate layer may be formed from the electrically resistive material. The substrate layer may comprise a woven material, wherein a plurality of threads of the electrically resistive material form at least part of the woven material.

In embodiments in which the aerosol-generating device comprises an electrical power supply and a controller, preferably the controller is arranged to provide a supply of electrical power from the electrical power supply to the electrically resistive portion.

The aerosol-generating device may be arranged to generate heat using the electrically resistive portion in addition to generating heat by surface plasmon resonance of the plurality of metallic nanoparticles. The aerosol-generating device may be arranged to generate heat using the electrically resistive portion as an alternative to generating heat by surface plasmon resonance of the plurality of metallic nanoparticles.

The aerosol-generating device may be arranged to generate heat using the electrically resistive portion as a backup to generating heat by surface plasmon resonance of the plurality of metallic nanoparticles. For example, the aerosol-generating device may be arranged to generate heat using the electrically resistive portion in the event that heating of the plurality of metallic nanoparticles by surface plasmon resonance is insufficient.

The aerosol-generating device may be arranged to generate heat using the electrically resistive portion at the start of a heating cycle. In other words, the electrically resistive portion may be used to generate heat to raise the temperature of the heating element to an initial operating temperature. The aerosol-generating device may be arranged to reduce or terminate a supply of electrical power to the electrically resistive portion when the temperature of the heating element reaches an initial operating temperature.

The heating element may comprise a first surface arranged to receive light from a light source and generate heat by surface plasmon resonance of the plurality of metallic nanoparticles. The first surface may comprise a plurality of surface features defining a three- dimensional shape. The first surface may comprise at least one of a plurality of protrusions and a plurality of depressions. The first surface may have an undulating shape.

Advantageously, a first surface comprising a plurality of surface features may increase the surface area of the first surface. Advantageously, increasing the surface area of the first surface may increase heating of the plurality of metallic nanoparticles by surface plasmon resonance when light is incident on the first surface.

In embodiments in which the heating element comprises a substrate layer and a coating layer, a first surface of the substrate layer may define the plurality of surface features, wherein the coating layer is provided on the first surface of the substrate layer to form the first surface of the heating element.

The heating element may comprise a second surface arranged to transfer heat to an aerosol-forming substrate during use. The second surface may be on an opposite side of the heating element to the first surface. In embodiments in which the heating element comprises a substrate layer and a coating layer, preferably the substrate layer comprises a first surface on which the coating layer is provided to form the first surface of the heating element, and a second surface forming the second surface of the heating element. Preferably, the substrate layer comprises a thermally conductive material to facilitate the transfer of heat from the coating layer to the second surface of the heating element.

According to a second aspect of the present invention, there is provided an aerosol- generating system comprising an aerosol-generating device according to the first aspect of the invention, and an aerosol-generating article configured to be at least partially received within the cavity of the aerosol-generating device, the aerosol-generating article comprising an aerosol-forming substrate. Examples of suitable aerosol-generating articles and aerosol- forming substrates are described in more detail below. According to a third aspect of the present invention, there is provided: an aerosol- generating device comprising: a cavity having a first end comprising an opening, a second end, and one or more side walls extending from the opening at the first end of the cavity to the second end of the cavity; and a heating element comprising an elongate body having a first end, a second end and one or more walls extending from the first end of the elongate body to the second end of the elongate body. The heating element is configured to be inserted into the cavity through the opening to define a space for accommodating at least part of an aerosol- forming substrate, said space being defined between the one or more side walls of the cavity and the one or more walls of the heating element. An inner surface of the one or more walls of the heating element comprises a heating surface having a plurality of metallic nanoparticles arranged to receive light from a light source and generate heat by surface plasmon resonance for heating the aerosol-generating article when the aerosol-generating article is received within the cavity. The cavity may comprise a base at its second end.

The aerosol-generating device of the third aspect of the invention advantageously comprises a heating element, which utilises surface plasmon resonance, and which is arranged to form a space for receiving at least part of an aerosol-forming substrate, when the heating element is disposed with a cavity of the device. The space is defined between the one or more side walls of the cavity and the one or more walls of the heating element. The cavity may be provided as part of a main body of the device. The space may be an annular space.

By providing a heating element which is configured to be inserted into the cavity, the heating element may be easily replaced or repaired. The heating element may be inserted into the cavity before an aerosol-forming substrate is inserted into the cavity. The heating element may be inserted into the cavity after an aerosol-forming substrate has been inserted into the cavity. The aerosol-generating device may supplied to the consumer in a configuration where the heating element is already disposed in the cavity, or in a configuration where the heating element is disposed externally to the cavity.

The heating element may be loosely disposable within the cavity. For example, the heating element may be disposable on a base wall of the cavity in order to form the space for receiving at least part of an aerosol-forming substrate. Alternatively, the heating element may instead be held in place within the cavity by forming a snug engagement with an aerosol- forming substrate, which is at least partially received in the cavity. In particular, an outer surface of the aerosol-forming substrate may engage with the side walls of the cavity, and an inner surface of the aerosol-forming substrate may engage with an outer surface of the heating element to hold the heating element in place with respect to the cavity. The heating element may be releasably attachable to the portion of the main body of the device, which defines the cavity. That is, the heating element may be movable between: an attached position, in which the heating element is attached to the main body of the device and at least partially disposed within the cavity; and a detached position, in which the heating element is detached from the main body of the device and disposed external to the cavity; wherein, the space for receiving at least part of an aerosol-forming substrate is formed between the one or more side walls of the cavity and the one or more walls of the heating element, when the heater is in the attached position. The attachment mechanism may comprise one or both of a screw thread and a bayonet locking mechanism.

The present invention also encompasses arrangements, in which the heating element is not removably insertable into the cavity of the main body of the device, but is instead disposed in and permanently affixed to cavity of the main body of the device. Therefore, according to a fourth aspect of the present invention, there is provided: an aerosol-generating device comprising: a main body comprising a cavity having an opening, a base, and one or more side walls extending from the opening of the cavity to the base of the cavity; and a heating element comprising an elongate body having a first end, a second end and one or more walls extending from the first end of the elongate body to the second end of the elongate body. The heating element is disposed in the cavity to form a space for receiving at least part of an aerosol-forming substrate, said space being defined between the one or more side walls of the cavity and the one or more walls of the heating element. A surface of the one or more walls of the heating element comprises a heating surface having a plurality of metallic nanoparticles arranged to receive light from a light source and generate heat by surface plasmon resonance for heating the aerosol-generating article when the aerosol-generating article is received within the cavity.

The aerosol-generating device of the third and fourth aspects of the invention may have any of the features described above in reference to the first and second aspects of the invention, and may have any of the further features described below. Equally, the aerosol- generating device of the first and second aspects of the invention may have any of the features described herein in reference to the third and fourth aspects of the invention.

Preferably, the cavity of the third or fourth aspect is substantially cylindrical and has a single cylindrical side wall. Preferably, the elongate body is substantially cylindrical and has a single cylindrical side wall. In such embodiments, the space for receiving the aerosol- forming substrate is substantially annular.

The base of the cavity may comprise a base wall, which extends between the ends of the one or more side walls of the cavity. The base wall of the cavity may comprise a light source for providing light to the plurality of metallic nanoparticles of the heating element. The base of the cavity may comprise an attachment mechanisms for attaching the heating element to the cavity.

The base of the cavity preferably comprises one or more openings for allowing aerosol to exit the cavity. The main body of the device may comprise one or more air channels for air to flow through after the air has exited the cavity. The one or more air channels may be in fluid communication with the air outlet. The air outlet may be disposed at a mouthpiece of the aerosol-generating device. The one or more air channels may comprise a venturi tube.

Preferably, the heating surface forms at least part of an inner surface of at least one of the one or more walls of the elongate body of the heating element. This may be advantageous if the aerosol-forming substrate to be heated is not light transmissive, because light may be transmitted to the heating surface through the inside of the heating element, and thus does not need to pass through the space for receiving the aerosol-forming substrate.

Preferably, the elongate body of the heating element tapers from the first end of the elongate body to the second end of the elongate body. This may help to facilitate insertion of one or both of the aerosol-forming substrate and the heating element into the cavity of the device.

Preferably, the aerosol-generating device comprises an airflow path extending from an air inlet to an air outlet via the space for receiving at least part of an aerosol-forming substrate. This advantageously enables the airflow path to pass directly through at least a portion of the aerosol-forming substrate, when the aerosol-forming substrate has been received in the cavity. This may help to improve one or more properties of the aerosol, which is produced by the aerosol-generating device.

The air outlet may be provided as part of a mouthpiece of the aerosol-generating device.

The air inlet may be provided as part of the heating element. Preferably, the air inlet is disposed at the first end of the elongate body of the heating element. For example, the heating element may comprise a flange, which extends laterally from the first end of the elongate body of the heating element; the flange being configured to cover a peripheral region of the opening of the cavity. The air inlet may comprise one or more openings in the flange of the heating element. This may advantageously help to control one or more of the amount of air, the rate of airflow, and the location of airflow. In such embodiments, airflow may enter the aerosol-generating device via the one or more openings in the flange of the heating element and pass straight into the space for receiving the at least part of an aerosol-forming substrate.

In some embodiments, the air inlet may comprise one or more openings in the first end of the elongate body for air to flow into the light chamber of the elongate body of the heating element. In such embodiments, at least some air must flow through at least part of the light chamber before it may reach the space for receiving the at least part of an aerosol-forming substrate, where it may form an aerosol. The air may exit the light chamber by one or more openings provided in the one or more walls of the elongate body of the heating element.

By arranging for at least some air to first flow through the light chamber before the airflow passes to the aerosol-forming substrate, heat may be drawn away from the light chamber. This may help to pre-heat the airflow before it reaches the aerosol-forming substrate. This may help to prevent the light chamber from overheating.

The one or more openings provided in the one or more walls of the elongate body of the heating element may consist of a single hole. Alternatively, at least one of the walls of the elongate body may be formed as a porous substrate such that airflow may pass through the wall. This may advantageously increase the efficiency of heat transfer from the heating surface to the airflow.

Use of such a porous substrate for surface plasmon resonance in an aerosol- generating article is therefore advantageous in its own right. Consequently, according to a fifth aspect of the present invention, there is provided a heating element for an aerosol- generating device, the heating element comprising a porous substrate comprising a heating surface, the heating surface having a plurality of metallic nanoparticles for generating heat by surface plasmon resonance when the plurality of metallic nanoparticles receive light.

The porous substrate may comprise a woven material, wherein a plurality of pores are formed between threads of the woven material. The porous substrate may have a plurality of pores. A plurality of pores may be formed using any suitable process. A plurality of pores may be formed using at least one of laser perforation and electron discharge machining.

The heating element of the fifth aspect of the present invention may have any of the features described above in respect of the first to fourth aspects of the present invention. For example, the heating element may comprise an elongate body having a first end, a second end, and a one or more walls extending from the first end to the second end, wherein the porous substrate forms at least a portion of the one or more walls.

The heating element of the fifth aspect of the present invention may be used in connection with an aerosol-generating device having any of the features described above in respect of the first to fourth aspects of the present invention. For example, an aerosol- generating device may comprise: a main body having a cavity for receiving at least part of an aerosol-forming substrate; and a heating element according to the fifth aspect of the present invention. The heating element may be removably insertable into the cavity, such that when the heating element is disposed in the cavity, the device comprises an airflow path extending from an air inlet to an air outlet, with at least a portion of the air flow path passing through the porous substrate of the heating element.

An aerosol-generating device may comprise: a cavity for receiving at least part of an aerosol-forming substrate; and a heating element according to the fifth aspect of the present invention. The heating element may be configured to be inserted into the cavity, such that when the heating element is disposed in the cavity, the device comprises an airflow path extending from an air inlet to an air outlet, with at least a portion of the air flow path passing through the porous substrate of the heating element. The aerosol-generating device may comprise a main body comprising the cavity. The heating element may be releasably attachable to the main body of the device, such that the heating element is movable between: an attached position, in which the heating element is attached to the main body of the device and at least partially disposed within the cavity; and a detached position, in which the heating element is detached from the main body of the device and disposed external to the cavity.

An aerosol-generating device may comprise: a cavity for receiving at least part of an aerosol-forming substrate; and a heating element according to the fifth aspect of the present invention; the heating element being at least partially disposed within the cavity, such that the device comprises an airflow path extending from an air inlet to an air outlet, with at least a portion of the air flow path passing through the porous substrate of the heating element. The aerosol-generating device may comprise a main body comprising the cavity.

The aerosol-generating device and heating element of the first to fifth aspects of the present invention may be used in conjunction with any suitable aerosol-forming substrate as described above and below.

As used herein, an‘aerosol-generating device’ relates to a device that may interact with an aerosol-forming substrate to generate an aerosol.

As used herein, the term‘aerosol-forming substrate’ relates to a substrate capable of releasing volatile compounds that may form an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate.

The aerosol-forming substrate may be part of an aerosol-forming article.

As used herein, the term‘aerosol generating system’ refers to a combination of an aerosol-generating device and one or more aerosol-forming articles for use with the device. An aerosol-generating system may include additional components, such as a charging unit for recharging an on-board electric power supply in an electrically operated or electric aerosol- generating device.

The aerosol-forming substrate may be part of an aerosol-generating article. The aerosol-forming substrate may have any suitable configuration. Preferably, the aerosol- forming substrate or aerosol-forming article has the shape of a substantially annular cylinder. Such a shape may be particularly suited to aerosol-generating articles and heating elements in accordance with the present invention.

The aerosol-forming substrate may be a solid aerosol-forming substrate. Alternatively, the aerosol-forming substrate may comprise both solid and liquid components. The aerosol- forming substrate may comprise a tobacco-containing material containing comprising volatile tobacco flavour compounds which are released from the substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may further comprise an aerosol former that facilitates the formation of a dense and stable aerosol. Examples of suitable aerosol formers are glycerine and propylene glycol.

If the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosol- forming substrate may comprise, for example, one or more of: powder, granules, pellets, shreds, spaghettis, strips or sheets containing one or more of: herb leaf, tobacco leaf, fragments of tobacco ribs, reconstituted tobacco, homogenised tobacco, extruded tobacco, cast leaf tobacco and expanded tobacco. The solid aerosol-forming substrate may be in loose form, or may be provided in a suitable container or cartridge. Optionally, the solid aerosol- forming substrate may contain comprise additional tobacco or non-tobacco volatile flavour compounds, to be released upon heating of the substrate. The solid aerosol-forming substrate may also contain capsules that, for example, include the additional tobacco or non-tobacco volatile flavour compounds and such capsules may melt during heating of the solid aerosol- forming substrate.

In embodiments in which the aerosol-generating device comprises a device connector, preferably the aerosol-generating article comprises an article connector configured to connect to the device connector. The article connector may comprise at least one of a screw connector, a bayonet connector, and a snap connector.

The aerosol-generating article may comprise an article housing, wherein the aerosol- forming substrate is disposed within the article housing. An aerosol-generating article comprising an article housing may also be referred to as a cartridge.

Preferably, the article housing defines an article air inlet and an article air outlet, wherein the aerosol-forming substrate is in fluid communication with the article air inlet and the article air outlet.

The article housing may define a heater cavity, wherein at least a portion of the heating element is received within the heater cavity when the aerosol-generating device receives the aerosol-generating article.

The aerosol-generating article may comprise a wrapper wrapped around at least a portion of the aerosol-forming substrate. Aerosol-generating articles comprising a wrapper may be particularly suited to embodiments in which the aerosol-forming substrate comprises a solid aerosol-forming substrate. The wrapper may be a paper wrapper.

The aerosol-generating article may have a total length of between approximately 30 millimetres and approximately 100 millimetres. The aerosol-generating article may have an external diameter of between approximately 5 millimetres and approximately 13 millimetres.

The aerosol-generating article may comprise a mouthpiece positioned downstream of the aerosol-forming substrate. The mouthpiece may be located at a downstream end of the aerosol-generating article. The mouthpiece may be a cellulose acetate filter plug. Preferably, the mouthpiece is approximately 7 millimetres in length, but may have a length of between approximately 5 millimetres to approximately 10 millimetres.

The aerosol-generating article may have a diameter of between approximately 5 millimetres and approximately 12 millimetres.

In a preferred embodiment, the aerosol-generating article has a total length of between approximately 40 millimetres and approximately 50 millimetres. Preferably, the aerosol- generating article has a total length of approximately 45 millimetres. Preferably, the aerosol- generating article has an external diameter of approximately 7.2 millimetres.

The aerosol-generating article may have any suitable cross-sectional shape, such as a circular, oval, square, or triangular shaped cross-section. In some preferred embodiments, the aerosol-generating article has a substantially cylindrical outer shape.

The aerosol-forming substrate may have any suitable cross-sectional shape, such as a circular, oval, square, or triangular shaped cross-section. Preferably, the aerosol-forming substrate has a substantially annular cross-sectional shape. That is, preferably the aerosol- forming substrate comprises a substantially cylindrical outer surface and a substantially cylindrical inner surface and an annular body disposed between the outer surface and the inner surface.

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

Figure 1A shows a cross-sectional view of an aerosol-generating article, together with an aerosol-generating device according to a first embodiment of the present invention, as seen in an unassembled condition;

Figure 1 B shows a cross-sectional view of an aerosol-generating article, together with an aerosol-generating device according to a first embodiment of the present invention, as seen in an assembled condition;

Figure 2 shows a cross-sectional view of the heating element of Figures 1 A and 1 B; Figure 3A shows a cross-sectional view of an aerosol-generating article, together with an aerosol-generating device according to a second embodiment of the present invention, as seen in an unassembled condition;

Figure 3B shows a cross-sectional view of an aerosol-generating article, together with an aerosol-generating device according to a second embodiment of the present invention, as seen in an assembled condition;

Figure 4 shows a cross-sectional view of the heating element of Figures 3A and 3B;

Figure 5 shows a cross-sectional view of a heating element according to a third embodiment of the present invention; and

Figure 6A shows a cross-sectional view of an aerosol-generating article, together with an aerosol-generating device according to a fourth embodiment of the present invention, as seen in an unassembled condition;

Figure 6B shows a cross-sectional view of an aerosol-generating article, together with an aerosol-generating device according to a fourth embodiment of the present invention, as seen in an assembled condition.

As can be seen from Figure 1A, the aerosol-generating device 100 of an embodiment of the invention comprises a main body 110 and a heating element 120. The main body 1 10 has a cavity 140 disposed at one end. The cavity 140 is arranged to receive the heating element 120 and an aerosol-generating article 130, which comprises a substantially shaped aerosol-forming substrate 132.

The cavity has a cylindrical side wall 142, which extends from an opening 143 on the outer surface of the main body 110 of the device 100 to a cavity base wall 144. An opening is also provided around the periphery of the cavity base wall 144. This may permit aerosol to flow to an air outlet 164 of the device along a passageway 166. The outlet 164 is provided at a mouthpiece 1 12 of the device.

The cavity base wall 144 further comprises a device light source 150, in the form of a plurality of light emitting diodes (LEDs). The device light source 150 is arranged to receive electrical power from a power supply 170 within the main body 1 10, in the form of a Lithium- ion battery. A controller 180 is also provided within the main body 1 10 of the device to control the supply of electrical power to the light source 150.

As best seen from Figure 2, the heating element 120 comprises an elongate body 122 having a first end 123a and a second end 123b, with a substantially cylindrical wall 124 extending from the first end 123a to the second end 123b. The wall 124 of the elongate body 122 defines a light chamber 125 within the heating element 120. The light chamber 125 may receive ambient light from its first end, via a first optical element 127 at the light chamber’s first end, and an optical component 128 attached to and extending from the first end 123a of the elongate body 122.

The optical component 128 is in the form of a bulbous structure comprising glass. The optical component 128 functions to increase the amount of ambient light receivable through the first end 123a of the elongate body 122.

The first optical element 127 provides one way light transmission, in that it allows ambient light to enter the light chamber 125 through the first end 123a, but prevents light from escaping the light chamber 125 through the first end, by way of reflection or adsorption. In particular, the first optical element 127 may be a glass substrate having a metallic coating, which reflects any light falling incident on the surface of the element 127 facing the light chamber 125.

The second end 123b of the heating element is open or provided with a transparent transverse wall, so that light may enter the light chamber 125 through the second end 123b. As will be explained in more detail below with reference to Figure 1 B, such light may originate from the device light source 150 in the main body 1 10 of the device, when the heating element 120 is inserted into the cavity 140.

The inner surface of the wall 124 of the elongate body 122 of the heating element 120 comprises one or more portions having a coating comprising a plurality of metallic nanoparticles. When light falls incident on the plurality of metallic nanoparticles heat is generated by relaxation of the metallic nanoparticles after undergoing plasmon resonance. Such heat may be used to heat the aerosol-forming substrate 132 of the aerosol-generating article 130, when the heating element 120 is adjacent to the article 130.

The light chamber 125 of the heating element 120 contains a second optical element 126, which in the first embodiment, is in the form of a conical shaped structure, having its widest end at the second end 123b of the elongate body 122. The second optical element is arranged to redirect light towards the inner surface of the wall 124, and more specifically, towards the plurality of metallic nanoparticles on the wall 124. The second optical element 126 divides the light chamber 125 into two sections; a first section and a second section. A reflective coating is provided on the second optical element 126, such that ambient light, which is received through the first end 123a and which falls incident on the optical element 126 is reflected towards the inner surface of the wall 124. This helps to ensure that light received through the first end 123a of the light chamber is not lost through the second end of the light chamber. In addition, light received through the second end 123b of the light chamber 125 may pass through the second optical element 126 into the first section of the optical chamber 125, and is preferably diverted towards the inner surface of the wall 124 by virtue of the conical shape of the second optical element 126. Once said light is in said first section of the light chamber 125, it is prevented from escaping said section of the chamber 125 by virtue of the reflective coating on the first optical element 127 and the reflective coating on the second optical element 126. This helps to improve the amount of light that is received by plurality of metallic nanoparticles on the inner surface of the wall 124.

The heating element 120 also comprises a flange 129 extending laterally from the first end of the elongate body 122. As shown in Figure 1 B, the flange is arranged to cover a peripheral region of the opening 143 of the cavity 140, when the heating element 120 is disposed within the cavity 140. The flange includes one or more openings, which act as air inlets 162. These allow air to flow into the cavity 140 when the device 100 is in use.

As best seen from Figure 1 B, when the device 100 is to be used, the heating element 120 is inserted into the cavity 140 of the main body 1 10. Disposed around the outside of the heating element 120 is the aerosol-generating article 130 and its aerosol-forming substrate 132. The second end 123b of the elongate body 122 abuts the base 144 of the cavity 140, and the flange 129 rests on top of an edge of the housing of the main body 1 10, which edge defines the opening 143 of the cavity 144. The device light source 150 is arranged to shine light into the light chamber 125 via the second end 123b of the elongate body 122 of the heating element 120. When in the assembled condition shown in Figure 1 B, an airflow path extends from the air inlet 162 in the flange 129 of the heating element 120 to the air outlet 164 in the mouthpiece 1 12 of the device main body 1 10. The airflow path extends: from the air inlet 162; along an annular space defined between the outer surface of the wall 124 of the elongate body 120 and the inner surface of the cavity side wall 142; through an opening 146 in the base wall 144 of the cavity 140; and along passageway 166, which comprises a venturi portion 165, until it reaches the air outlet 164.

The aerosol-forming substrate 132 of the aerosol-generating article 130 may be heated by the wall 124 of the heating element 120, so that an aerosol is formed as air passes through the space in which the aerosol-generating article 130 is disposed. Heat may be created at the wall 124 of the heating element 120 by way of surface plasmon resonance, which occurs when light falls incident on the plurality of metallic nanoparticles disposed on the inner surface of the wall 124. The heat may be generated solely by way of ambient light being received through the first end of the heating element 120. Alternatively, heat may be generated by way of a combination of ambient light being received through the first end of the heating element 120, and light received from the device light source 150 through the second end of the heating element 120. Light from the light source 150 may be initiated by the controller 180 issuing a command for the electrical power supply 170 to supply electrical power to the light source 150.

Figure 3A shows a schematic view of an aerosol-generating article 330, together with an aerosol-generating device 300 according to a second embodiment of the present invention, as seen in an unassembled condition. Like numerals are used in Figures 3A, 3B, and 4 to indicate like features to those described above in respect of Figures 1 A, 1 B and 2. The device 300 of Figure 3A is equivalent to the device of Figure 1 B, except that the device light source 350 is now provided as part of the heating element 320 and the elongate body 322 of the heating element 320 now tapers from its first end 323a to its second end 323b. This may be best seen from Figure 4.

In particular, the light source is now attached to the second end 323b of the elongate body 322 of the heating element 320, and is provided with two electrical contacts 351 , 352, which are arranged to electrically connect to corresponding electrical contacts (not shown) in the base wall 344 of the cavity 340, when the heating element 320 is inserted into the cavity 340. As shown in Figure 3A, the aerosol-generating article 330 of the second embodiment also tapers from its first end to its second end.

Figure 5 shows a schematic view of a heating element 520 according to an embodiment of the present invention. Like numerals are used in Figure 5 to indicate like features to those described above in respect of Figures 1A to 4. The heating element 520 is similar to the heating elements 120, 320 of the first and second embodiments. However, in Figure 5, the air inlet 562 is not provided in the flange 529. Instead, the air inlet 562 is formed by one or more openings in the first end 523a of the elongate body 522 of the heating element 520. Consequently, when air enters the airflow path at the air inlet 562 it first flows into the light chamber 525 of the heating element 520, as indicated by the arrows in Figure 5. In order for the air to then continue along the airflow path and flow to the aerosol-forming substrate, the wall 524 of the elongate body is porous. That is, the wall 524 comprises a plurality of pores through which the air may flow. It will be appreciated that, when the heating element

520 of Figure 5 is in use, the air will flow through the porous wall 524 into a space between the wall 524 and a side wall of the cavity of the aerosol-generating device. Since this is the space that the aerosol-forming substrate is residing, and since the aerosol-forming substrate and the air will be heated by virtue of surface plasmon resonance, an aerosol may be generated.

In contrast to the heating elements 120, 320 of the first and second embodiments, the heating element 520 contains an optical element 526 in its light chamber 525, in the form of a conical shaped structure, having its widest end at the first end 523a of the elongate body 522. The heating element 520 also comprises a lens 521 disposed at its first end 523a. The lens

521 is arranged to direct light which enters the light chamber through the first end 523a of the elongate body 522 towards the heating surface. The narrower end of the conical shaped optical element 526 is disposed at the second end 523b of the elongate body of the heating element 520 in contact with the at least one lens 521 . The tip of the conical shaped optical element 526 is located centrally within the light chamber 525.

Figures 6A and 6B show cross-sectional views of an aerosol-generating article, together with an aerosol-generating device according to a fourth embodiment of the present invention, as seen in an unassembled and an assembled condition respectively. Like numerals are used in Figures 6A and 6B, to indicate like features to those described above in respect of Figures 1 A to 5.

The device 600 of Figure 6A comprises a main body 610, which is similar to the device main bodies shown in Figures 1A, 1 B, 3A and 3B. However, in Figure 6A, the cavity 640 is not provided as part of the main body 610. Instead, the cavity 640 is defined by a casing member 690, which can be releasably attached to a portion 614 of the main body 610 of the device. The casing member 690 comprises a first end 691 a; a second end 691 b defining the opening 643 of the cavity 640 for receiving the heating element 620; and a single substantially cylindrical wall 692 extending from the first end 691 a of the wall 692 to the second end 691 b of the wall 692.

As with the embodiments of Figures 1A, 1 B, 3A and 3B, the heating element 620 of Figures 6A and 6B comprises an elongate body 622 having a first end 623a arranged to receive ambient light, and a second end 623b arranged to receive light from a device light source 650 in the device main body 610. However, in contrast to the embodiments of Figures 1A, 1 B, 3A and 3B, the heating element 620 of Figures 6A and 6B does not comprise an optical component attached to and extending from the first end of its elongate body 622. Instead, such an optical component is provided as part of the casing member, and more specifically, is attached to the second end 691 b of the casing member’s substantially cylindrical wall 692. The elongate body 622 of the heating element 620 of Figures 6A and 6B now tapers from its second end 623b to its first end 623a.

The heating element 620 in Figure 6A also comprises a lens 621 disposed at its first end. The lens 621 is donut shaped and extends around the tip of the conical shaped optical element 626.

To assemble the device 600 of Figure 6A, a user may first need to ensure that the heating element is disposed in the position shown in Figure 6A. That is, the second end 623b of the elongate body 622 should be adjacent to the device light source 650. This may require no action from the user if the heating element 620 is permanently affixed to the main body 610 of the device. Alternatively, if the heating element 620 is releasably attachable to the main body 610 of the device, then the heating element 620 should first be attached into the position shown in Figure 6A. A tapered tubular aerosol-generating article 630 is then slid over the outer surface of the substantially cylindrical wall 624 of the heating element 620 to form a snug engagement. The casing member 690 is then placed over the heating element 620 and the aerosol-generating article 630 and attached to the main body 610 of the device 600, so that the device 600 and the aerosol-generating article 630 are in the configuration shown in Figure 6B. In this assembled configuration an annular space is defined between the inner surface of the substantially cylindrical wall 692 of the casing member 690 and the outer surface of the substantially cylindrical wall 624 of the heating element 620, for accommodating the aerosol- generating article. This can be best appreciated with reference to Figure 6B.

Claims

1. An aerosol-generating device comprising:

a cavity for receiving at least part of an aerosol-generating substrate; and

a heating element for heating an aerosol-generating substrate when at least part of the aerosol-generating substrate is received within the cavity,

wherein the heating element comprises a heating surface having a plurality of metallic nanoparticles arranged to receive ambient light from a light source external to the device and generate heat by surface plasmon resonance.

2. An aerosol-generating device according to claim 1 , wherein the heating element comprises an elongate body having a first end, a second end, and one or more walls extending from the first end to the second end to define a light chamber within the elongate body;

wherein an inner surface of the wall comprises the heating surface; and

wherein the plurality of metallic nanoparticles of the heating surface are arranged to receive the ambient light from the light source external to the device through the first end of the elongate body.

3. An aerosol-generating device according to claim 2, wherein the device further comprises a light source for providing light to the plurality of metallic nanoparticles through the second end of the elongate body.

4. An aerosol-generating device according to claim 2 or claim 3, further comprising an optical element disposed within the elongate body of the heating element, the optical element being arranged to divert ambient light received through the first end of the elongate body towards the heating surface.

5. An aerosol-generating device according to any of claims 2 to 4, wherein the heating element further comprises a mechanism at the first end of the elongate body for controlling the amount of ambient light which may be directed into the light chamber.

6. An aerosol-generating device according to any of claims 2 to 5, wherein heating element further comprises an optical component at the first end of the elongate body for increasing the amount of ambient light receivable through the first end of the elongate body.

7. An aerosol-generating device according to any of the preceding claims, wherein the device comprises a main body comprising the cavity and the heating element is removably insertable into the cavity.

8. An aerosol-generating system comprising:

an aerosol-generating device according to any of claims 1 to 7; and

an aerosol-generating article configured to be at least partially received within the cavity of the aerosol-generating device, the aerosol-generating article comprising an aerosol- forming substrate.

9. An aerosol-generating device comprising:

a cavity having a first end comprising an opening, a second end, and one or more side walls extending from the opening at the first end of the cavity to the second end of the cavity; and

a heating element comprising an elongate body having a first end, a second end and one or more walls extending from the first end of the elongate body to the second end of the elongate body;

wherein the heating element is configured to be inserted into the cavity through the opening to define a space for accommodating at least part of an aerosol-forming substrate, said space being defined between the one or more side walls of the cavity and the one or more walls of the heating element; and

wherein a surface of the one or more walls of the heating element comprises a heating surface having a plurality of metallic nanoparticles arranged to receive light from a light source and generate heat by surface plasmon resonance for heating the aerosol-generating article when the aerosol-generating article is received within the cavity.

10. An aerosol-generating device comprising:

a main body comprising a cavity having an opening, a base, and one or more side walls extending from the opening of the cavity to the base of the cavity; and

wherein he heating element is disposed in the cavity to form a space for receiving at least part of an aerosol-forming substrate, said space being defined between the one or more side walls of the cavity and the one or more walls of the heating element; and wherein a surface of the one or more walls of the heating element comprises a heating surface having a plurality of metallic nanoparticles arranged to receive light from a light source and generate heat by surface plasmon resonance for heating the aerosol-generating article when the aerosol-generating article is received within the cavity.

1 1 . An aerosol-generating device according to claim 9 or 10, wherein the heating surface forms at least part of an inner surface of at least one of the one or more walls of the elongate body of the heating element.

12. An aerosol-generating device according to any of claims 9 to 1 1 , wherein the elongate body of the heating element tapers from the first end of the elongate body to the second end of the elongate body.

13. An aerosol-generating device according to any of claims 9 to 12, wherein the aerosol- generating device comprises an airflow path extending from an air inlet to an air outlet via the space for receiving at least part of an aerosol-forming substrate.

14. An aerosol-generating device according to claim 13, wherein the air inlet is disposed at the first end of the elongate body of the heating element.

15. An aerosol-generating system comprising:

an aerosol-generating device according to any of claims 9 to 14; and

an aerosol-generating article configured to be at least partially received within the space defined between the one or more side walls of the cavity and the one or more walls of the elongate body of the heating element.

16. A heating element for an aerosol-generating device, the heating element comprising a porous substrate comprising a heating surface, the heating surface having a plurality of metallic nanoparticles for generating heat by surface plasmon resonance when the plurality of metallic nanoparticles receive light.

17. A heating element according to claim 16, wherein the heating element comprises an elongate body having a first end, a second end, and one or more walls extending from the first end to the second end, and wherein the porous substrate forms at least a portion of at least one of the one or more walls of the elongate body.

18. An aerosol-generating device comprising:

a cavity for receiving at least part of an aerosol-generating substrate; and

a heating element according to claim 16 or claim 17,

wherein the heating element is disposed in the cavity, such that the device comprises an airflow path extending from an air inlet to an air outlet, with at least a portion of the air flow path passing through the porous substrate of the heating element.