Patent Publication Number: US-2022211116-A1

Title: An aerosol-generating system and a thermal output element for an aerosol-generating system

Description:
The present invention relates to an aerosol-generating system, to a device for use with the system, and to a method of generating an aerosol. In particular, the invention relates to handheld aerosol-generating systems and devices which vaporise an aerosol-forming substrate by heating to generate an aerosol to be puffed or inhaled by a user, and which include an interface element. 
     One type of aerosol-generating system is an electrically heated smoking system that generates an aerosol for a user to puff or inhale. Electrically heated smoking systems come in various forms. Some types of electrically heated smoking systems are e-cigarettes that vaporise a liquid or gel substrate to form an aerosol, or release an aerosol from a solid substrate by heating it to a certain temperature below the combustion temperature of the solid substrate. 
     Handheld electrically operated aerosol-generating devices and systems are known that consist of a device portion comprising a battery and control electronics, a portion for containing or receiving an aerosol-forming substrate and an electrically operated heater for heating the aerosol-forming substrate to generate an aerosol. A mouthpiece portion is also included on which a user may puff to draw aerosol into their mouth. 
     Some devices and systems use a liquid or gel aerosol-forming substrate stored in a storage portion. Such devices can use a wick to carry the liquid or gel aerosol-forming substrate from the storage portion to the heater where it is aerosolised. Such devices can use a displacement mechanism such as a pump and piston to displace the liquid or gel aerosol-forming substrate from the storage portion to the heater. Other types of aerosol-generating devices and systems use a solid aerosol-forming substrate that includes a tobacco material. Such devices may comprise a recess for receiving a cigarette-shaped rod comprising the solid aerosol-forming substrate, such as folded sheets that include a tobacco material. A blade-shaped heater arranged in the recess is inserted into the centre of the rod as the rod is received in the recess. The heater is configured to heat the aerosol-forming substrate to generate an aerosol without substantially combusting the aerosol-forming substrate. 
     Electrically heated smoking systems can provide a significantly different user experience than a conventional, combustion-based cigarette. For example, the user interacts with a device rather than lighting a cigarette. In some cases, the interaction may not necessarily be limited to a single device but can include interaction with other peripheral devices, such as a device charger, charging case, consumable holder, smartphone, tablet computer, personal computer, vending machine, or other device. Additionally, a given manufacturer may have different electrically heated smoking systems available on the market at a given time, and may introduce new products to replace older products. 
     Such a multitude of different systems, devices, and peripheral devices can mean a multitude of different interactions with the user. For example, depending on the particular electrically heated smoking system, exemplary activation of a given electrically heated smoking system can be performed by a single press on a button, multiple presses on a button, or an extended press on a button. Additionally, depending on the particular electrically heated smoking system, certain feedback may be provided to the user responsive to the activation, such as a vibration signal, an auditory signal, or a light signal, or no feedback may be provided responsive to the actuation. Additionally, depending on the particular electrically heated smoking system, the user may have to wait for a certain time before the aerosol can be consumed, e.g., before the heater is at a sufficient temperature to generate the aerosol. The system may or may not indicate whether a waiting time is running, and may or may not give an indication of the elapsed waiting time or remaining waiting time. Such indication, if provided, may include one or more of a number of illuminated lights, a brightness of one or more lights, a pulsing or intermittent illumination of a light, a change of colour of one or more lights, or an output of a textual or graphical interface. Additionally, depending on the particular electrically heated smoking system, the device may or may not give feedback when the consumable (e.g., liquid, gel, or solid aerosol-forming substrate) is ready for consumption, such as a vibration signal, an auditory signal, or a light signal, which may be in a state in the indication of the waiting time as indicated above. Additionally, some electrically heated smoking systems can use the same output (such as a light, vibration, or auditory signal) to indicate different functionalities or statuses of the same system, which may be confusing for the user. Similarly, some electrically heated smoking systems can use the same input element (such as a button) to provide different types of user input to the same device, which may be confusing for the user. 
     Additionally, different electrically heated smoking systems even from the same manufacturer may use different input elements or output elements to interact with the user in different ways than one another. For example, the user may be able to check the battery level of the smoking system using interfaces of the system itself, of a first peripheral device such as the system&#39;s charging case, and of a second peripheral device such as a smartphone associated with the system. However, the system and the peripheral devices may have different interfaces than one another, making the user&#39;s interaction with the system complex, and distracting from the smoking experience. Furthermore, outputs such as lights and vibrations may disturb others or be distracting to the user. 
     As such, information provided to the user by a given electrically heated smoking system may convey limited information, may be confusing, or may disturb others. This can result in a diminished experience for the user. Furthermore, interfaces on different systems—even from the same manufacturer—may differ significantly from one another. This can make it difficult for the user to switch between devices or may deter the user from trying a new system or even a new model of the same system. 
     An objective of the present invention is to provide the user with easily understandable feedback that conveys meaningful information, preferably without disturbing others. For example, some configurations of the present invention can enhance feedback to users by providing an interface on an aerosol-generating device that includes a thermal output element, via which the user can perceive a temperature change that conveys information. The interface, including the thermal output element, optionally can be provided in the form of a button or other distinct element which is attached to the housing of the aerosol-generating device and which is controlled by appropriate circuitry. Preferably, any peripheral devices associated with the aerosol-generating device also can include such an interface configured so as to provide the same type of output to the user, such that the user can interact with multiple components of an aerosol-generating system in a consistent manner via such interfaces. Optionally, the user receives an immediate and understandable response following actuation of the interface. For example, the interface optionally can include a user-actuatable input element that is located at or sufficiently close to the thermal output element that responsive to the user&#39;s finger, lip, or palm actuating the input element, the thermal output element is actuated so as to provide a user-perceptible temperature change to the user&#39;s finger, lip, or palm, thus providing a temperature-changing tactile interface. However, it should be understood that the thermal output element can be actuated in any suitable manner, and is not limited to use with a user-actuated input element. As an additional or alternative option, complex information can be conveyed by modulating the user-perceptible temperature change, e.g., increasing or decreasing a temperature via the interface. It will be appreciated that the present thermal output elements can avoid or reduce the need for audible or vibrational signals which the user and others may hear, as well as visible signals which the user and others may see, thus potentially improving the experience for the user and others around him or her. 
     According to a first embodiment of the invention, there is provided an aerosol-generating device. The aerosol-generating device comprises a housing. The housing optionally comprises one or more of an air inlet, an air outlet, and an airflow path extending therebetween. The aerosol-generating device comprises an aerosol-generating element disposed within the housing and configured to generate an aerosol. The aerosol-generating device comprises a thermal output element coupled to the housing. The thermal output element is distinct from the aerosol-generating element. The aerosol-generating device comprises a circuit coupled to the thermal output element and configured to cause the thermal output element to generate a user-perceptible temperature change. 
     In some configurations, the device further includes a sensor coupled to the circuit and configured to output to the circuit a temperature of the thermal output element. The circuit optionally is configured to adjust operation of the thermal output element or to terminate operation of the thermal output element based on the temperature received from the sensor. 
     In some configurations, the thermal output element is selected from the group consisting of a thermoelectric device, a resistive member, an inductive member, and an infrared source. Additionally, or alternatively, the user-perceptible temperature change optionally comprises cooling. Additionally, or alternatively, the user-perceptible temperature change optionally comprises heating. 
     In some configurations, the device further comprises an input element configured to generate an input signal. The circuit optionally is configured to cause the thermal output element to generate the user-perceptible temperature change responsive to the input signal. Optionally, the input element is user-actuatable. In some configurations, the thermal output element is located sufficiently close to the input element that the user can perceive the temperature change while actuating the input element. As a further option, the input element and the thermal output element are arranged in a stack. Additionally, or alternatively, the input element optionally is selected from the group consisting of a mechanical button, a membrane button, a mechanical switch, a rotary encoder, a dial, a knob, a capacitive touch button, a resistive touch button, a joystick, a slider, a trigger button, a touch screen, and a magnetic switch. As another alternative, the input signal corresponds to a condition of the aerosol-generating device. 
     In some configurations, an aerosol-generating system comprises an aerosol-generating device such as described herein, and a peripheral device in operable communication with the aerosol-generating device. The peripheral device optionally is configured to transmit to the aerosol-generating device a signal corresponding to a condition of the aerosol-generating device. The circuit optionally is configured to cause the output element to generate the user-perceptible temperature change responsive to receipt of the signal. In nonlimiting configurations, the peripheral device optionally comprises a device charger, charging case, consumable holder, smartphone, tablet computer, personal computer, or vending machine. 
     In some configurations, the circuit determines a status of the device, and the user-perceptible temperature change indicates the status of the device. 
     In some configurations, an aerosol-generating system comprises an aerosol-generating device such as described herein and an aerosol-forming substrate, optionally wherein the aerosol-forming substrate comprises nicotine. 
     As used herein, the term ‘aerosol-generating system’ relates to a system that interacts with one or more other elements. One such element with which an ‘aerosol-generating system’ can interact is an aerosol-forming substrate to generate an aerosol. Another such element with which an ‘aerosol-generating system’ can interact is a peripheral device. An ‘aerosol-generating’ system optionally can interact with both an aerosol-forming substrate (e.g., provided within an aerosol-generating article) and any suitable number of peripheral devices. 
     As used herein, the term ‘peripheral device’ relates to a device that is part of an aerosol-generating system and interacts directly or indirectly with an aerosol-generating device, but is not itself an aerosol-generating device. Examples of peripheral devices include, but are not limited to, a charger for the aerosol-generating device, a charging case for the aerosol-generating device, a holder for one or more aerosol-generating articles, a smartphone, tablet computer, or personal computer configured to communicate directly or indirectly with the aerosol-generating device, or a vending machine configured to sell the aerosol-generating device or aerosol-generating articles. 
     As used herein, the term ‘aerosol-generating article’ relates to an article comprising an aerosol-forming substrate. Optionally, the aerosol-generating article also comprises one or more further components, such as a reservoir, carrier material, wrapper, etc. An aerosol-generating article may generate an aerosol that is directly inhalable into a user&#39;s lungs through the user&#39;s mouth. An aerosol-generating article may be disposable. An aerosol-generating article comprising an aerosol-forming substrate comprising tobacco may be referred to as a tobacco stick. 
     As used herein, the term ‘aerosol-forming substrate’ relates to a substrate capable of releasing one or more volatile compounds that can form an aerosol. Such volatile compounds are released by heating the aerosol-forming substrate to form a vapour. The vapour can condense to form an aerosol, for example a suspension of fine solid particles or liquid droplets in a gas such as air. An aerosol-forming substrate may conveniently be part of an aerosol-generating device or system. In some configurations, the aerosol-forming substrate comprises a gel or liquid, while in other configurations, the aerosol-forming substrate comprises a solid. The aerosol-forming substrate may comprise both liquid and solid components. 
     As used herein, the term ‘coupled’ relates to an arrangement of elements that can be directly or indirectly in contact with one another. Elements that are ‘directly’ coupled to one another touch one another. Elements that are ‘indirectly’ coupled to one another do not directly touch one another, but are attached to one another via one or more intermediate elements. Depending on the particular arrangement, elements that are part of the same device or system as one another may be ‘directly’ in contact with one another or ‘indirectly’ in contact with one another. 
     As used herein, the term ‘thermal communication’ relates to elements that are coupled to one another in such a manner that a change in temperature of one such element causes a change in temperature of another such element. 
     As used herein, the term ‘interface’ relates to an element through which information can be transmitted, through which information can be received, or through which information can be both transmitted and received. An exemplary interface provided herein includes a thermal output element for transmitting information, and optionally includes a user-actuatable input element for receiving information. 
     As used herein, the term ‘thermal output element’ relates to an element that provides information to a user by generating a user-perceptible temperature change. For example, the thermal output element is configured such that when such element is actuated, a user can feel and recognize a corresponding change in temperature via the user&#39;s sense of touch. The thermal output element may be actuated in such a manner as to convey information to the user via the user-perceptible temperature change. 
     As used herein, the term ‘user-perceptible temperature change’ relates to a change of temperature that can be felt and recognized by a user. Typically, the user can feel the user-perceptible change of temperature via his or her sense of touch at a defined portion of the device or system that the user is touching, for example using his or her finger, palm, or lip. Such defined portion of the device or system at which the user-perceptible temperature change is generated can be or include, for example, as a defined outer (peripheral) portion of the housing of the device of system, or the thermal output element, or any other suitable element of the interface, device, or system that is in thermal communication with the interface element. The portion of the device or system at which the user-perceptible temperature change is generated can initially be at a first temperature, such as ambient (room) temperature, or warmer than ambient temperature, for example because of heat transferred to such element by the aerosol-generating element or because of heat transferred from the user&#39;s skin, e.g., finger or lip. Actuation of the thermal output element causes the temperature at the defined portion of the device or system to increase or decrease to a second temperature that is perceptibly different from the first temperature. 
     Examples of user-perceptible temperature changes generated by actuation of the thermal output element may include, for example, a temperature increase of about 0.02 degrees Celsius or greater, or a temperature increase of about 0.05 degrees Celsius or greater, or a temperature increase of about 0.1 degrees Celsius or greater, or a temperature increase of about 0.2 degrees Celsius or greater, or a temperature increase of about 0.5 degrees Celsius or greater, or a temperature increase of about 1 degree Celsius or greater, or a temperature increase of about 2 degrees Celsius or greater, or a temperature increase of about 5 degrees Celsius or greater. For example, the user-perceptible temperature increase may be in a range of about 0.02 degrees Celsius to about 10 degrees Celsius, or may be in a range of about 0.05 degrees Celsius to about 10 degrees Celsius, or may be in a range of about 0.1 degrees Celsius to about 10 degrees Celsius, or may be in a range of about 0.1 degrees Celsius to about 10 degrees Celsius, or may be in a range of about 0.2 degrees Celsius to about 10 degrees Celsius, or may be in a range of about 0.5 degrees Celsius to about 10 degrees Celsius, or may be in a range of about 1 degree Celsius to about 10 degrees Celsius, or may be in a range of about 0.05 degrees Celsius to about 5 degrees Celsius, or may be in a range of about 0.1 degrees Celsius to about 5 degrees Celsius, or may be in a range of about 0.5 degrees Celsius to about 5 degrees Celsius, or may be in a range of about 0.5 degrees Celsius to about 2 degrees Celsius. 
     Other examples of user-perceptible temperature changes generated by actuation of the thermal output element may include, for example, a temperature decrease of about 0.02 degrees Celsius or greater, or a temperature decrease of about 0.05 degrees Celsius or greater, or a temperature decrease of about 0.1 degrees Celsius or greater, or a temperature decrease increase of about 0.2 degrees Celsius or greater, or a temperature decrease of about 0.5 degrees Celsius or greater, or a temperature decrease of about 1 degrees Celsius or greater, or a temperature decrease of about 2 degrees Celsius or greater, or a temperature decrease of about 5 degrees Celsius or greater. For example, the user-perceptible temperature decrease may be in a range of about 0.02 degrees Celsius to about 10 degrees Celsius, or may be in a range of about 0.05 degrees Celsius to about 10 degrees Celsius, or may be in a range of about 0.1 degrees Celsius to 10 degrees Celsius, or may be in a range of about 0.1 degrees Celsius to about 10 degrees Celsius, or may be in a range of about 0.2 degrees Celsius to about 10 degrees Celsius, or may be in a range of about 0.5 degrees Celsius to about 10 degrees Celsius, or may be in a range of about 1 degree Celsius to about 10 degrees Celsius, or may be in a range of about 0.05 degrees Celsius to about 5 degrees Celsius, or may be in a range of about 0.1 degrees Celsius to about 5 degrees Celsius, or may be in a range of about 0.5 degrees Celsius to about 5 degrees Celsius, or may be in a range of about 0.5 degrees Celsius to about 2 degrees Celsius. 
     The user-perceptible temperature change generated by actuation of the thermal output element may be at a rate that is sufficiently high to convey relevant information to the user. For example, if the rate is too low, then the user may have difficulty perceiving the temperature change, may become annoyed at having to wait too long to obtain the information conveyed by the temperature change, or may move his or her lips, palm, or finger before all of the information is conveyed and thus miss receiving part of the information. Preferably, the user-perceptible temperature change generated by actuation of the thermal output element may be at a rate such that the change is completed within less than 10 seconds, or within less than 5 seconds, or within less than 2 seconds, or within less than 1 second, or within less than 0.5 seconds, or within less than 0.2 seconds, or within less than 0.1 seconds. For example, the user-perceptible temperature change generated by actuation of the thermal output element may be at a rate such that the change is completed within 0.1-10 seconds, or within 0.1-5 seconds, or within 0.5-5 seconds, or within 0.2-2 seconds, or within 0.2-1 second, or within 0.1-0.5 seconds, or within 0.1-0.2 seconds. 
     The user-perceptible temperature increase generated by actuation of the thermal output element may be a linear function of time, or the user-perceptible temperature increase generated by actuation of the thermal output element may be a nonlinear function of time. The user-perceptible temperature decrease generated by actuation of the thermal output element may be a linear function of time, or the user-perceptible temperature decrease generated by actuation of the thermal output element may be a nonlinear function of time. The user-perceptible temperature change generated by actuation of the thermal output element may be ‘modulated,’ that is, may include a predefined sequence of temperature change that conveys predefined information. Nonlimiting examples of predefined sequences of user-perceptible temperature change include a temperature increase followed by a temperature decrease, a temperature decrease followed by a temperature increase, a first temperature increase followed by a second, distinct temperature increase, or a first temperature decrease followed by a second, distinct temperature decrease. 
     The present thermal output elements suitably can be used with and included as part of any aerosol-generating system or device, including as part of any peripheral device to such a system. That is, the present thermal output elements need not necessarily be directly coupled to or provided as part of an aerosol-generating element, but may be directly coupled to or provided as part of any suitable device that is an element of an aerosol-generating system or device. 
     The aerosol-generating system or device can include a gel, liquid, or solid aerosol-forming substrate, and can include a suitably configured aerosol-generating element configured as to generate an aerosol therefrom. 
     In configurations in which the aerosol-forming substrate comprises a gel or liquid, the aerosol-generating system or device can include a reservoir holding the aerosol-forming substrate, which reservoir optionally may contain a carrier material for holding the aerosol-forming substrate. The carrier material optionally may be or include a foam, a sponge, or a collection of fibres. The carrier material optionally may be formed from a polymer or co-polymer. In one embodiment, the carrier material is or includes a spun polymer. 
     In some configurations, the aerosol-generating system optionally comprises a cartridge and a mouthpiece couplable to the cartridge. The cartridge optionally comprises at least one of the reservoir and the aerosol-generating element. Additionally, or alternatively, the housing of the aerosol-generating system optionally further comprises an air inlet, an air outlet, and an airflow path extending therebetween, wherein the vapour optionally at least partially condenses into an aerosol within the airflow path. 
     For example, in various configurations provided herein, the cartridge may comprise a housing having a connection end and a mouth end remote from the connection end, the connection end configured to connect to a control body of an aerosol-generating system. The aerosol-generating element may be located fully within the cartridge, or located fully within the control body, or may be partially located within the cartridge and partially located within the control body. Electrical power may be delivered to the aerosol-generating element from the connected control body through the connection end of the housing. In some configurations, the aerosol-generating element optionally is closer to the connection end than to the mouth end opening. This allows for a simple and short electrical connection path between a power source in the control body and the aerosol-generating element. 
     The aerosol-generating element, which optionally is or includes a heating element, may be substantially planar. The heating element may comprise a resistive material, e.g., a material that generates heat responsive to flow of electrical current therethrough. In one configuration, the heating element comprises one or a plurality of electrically conductive filaments. The term ‘filament’ refers to an electrical path arranged between two electrical contacts. The heating element may be or include an array of filaments or wires, for example arranged parallel to each other. In some configurations, the filaments or wires may form a mesh. However, it should be appreciated that any suitable configuration and material of the heating element can be used. 
     For example, the heating element may include or be formed from any material with suitable electrical properties. Suitable materials include but are not limited to: semiconductors such as doped ceramics, electrically ‘conductive’ ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys and composite materials made of a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum and metals from the platinum group. Examples of suitable metal alloys include stainless steel, constantan, nickel-, cobalt-, chromium-, aluminum-, titanium-, zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetal®, iron-aluminum based alloys and iron-manganese-aluminum based alloys. Timetal® is a registered trade mark of Titanium Metals Corporation. Exemplary materials are stainless steel and graphite, more preferably  300  series stainless steel like AISI 304, 316, 304L, 316L. Additionally, the heating element may comprise combinations of the above materials. In one nonlimiting configuration, the heating element includes or is made of wire. More preferably, the wire is made of metal, most preferably made of stainless steel. The heater assembly further may comprise electrical contact portions electrically connected to the heating element. The electrical contact portions may be or include two electrically conductive contact pads. In configurations including a housing, the contact portions may exposed through a connection end of the housing to allow for contact with electrical contact pins in a control body. 
     The reservoir may comprise a reservoir housing. The aerosol-generating element, a heating assembly comprising the aerosol-generating element, or any suitable component thereof may be fixed to the reservoir housing. The reservoir housing may comprise a moulded component or mount, the moulded component or mount being moulded over the aerosol-generating element or the heating assembly. The moulded component or mount may cover all or a portion of the aerosol-generating element or heating assembly and may partially or fully isolate electrical contact portions from one or both of the airflow path and the aerosol-forming substrate. The moulded component or mount may comprise at least one wall forming part of the reservoir housing. The moulded component or mount may define a flow path from the reservoir to the aerosol-generating element. 
     The housing may be formed form a mouldable plastics material, such as polypropylene (PP) or polyethylene terephthalate (PET). The housing may form a part or all of a wall of the reservoir. The housing and reservoir may be integrally formed. Alternatively the reservoir may be formed separately from the housing and assembled to the housing. 
     In configurations in which the aerosol-generating system or device includes a cartridge, the cartridge may comprise a removable mouthpiece through which aerosol may be drawn by a user. The removable mouthpiece may cover the mouth end opening. Alternatively the cartridge may be configured to allow a user to draw directly on the mouth end opening. 
     The cartridge may be refillable with liquid or gel aerosol-forming substrate. Alternatively, the cartridge may be designed to be disposed of when the reservoir becomes empty of liquid or gel aerosol-forming substrate. 
     In configurations in which the aerosol-generating system or device further includes a control body, the control body may comprise at least one electrical contact element configured to provide an electrical connection to the aerosol-generating element when the control body is connected to the cartridge. The electrical contact element optionally may be elongate. The electrical contact element optionally may be spring-loaded. The electrical contact element optionally may contact an electrical contact pad in the cartridge. Optionally, the control body may comprise a connecting portion for engagement with the connection end of the cartridge. Optionally, the control body may comprise a power supply. Optionally, the control body may comprise control circuitry configured to control a supply of power from the power supply to the aerosol-generating element. 
     The control circuitry optionally may comprise a microcontroller. The microcontroller is preferably a programmable microcontroller. The control circuitry may comprise further electronic components. The control circuitry may be configured to actuate the present thermal output elements. The control circuitry further may be configured to regulate a supply of power to the aerosol-generating element. Power may be supplied to the aerosol-generating element continuously following activation of the system or may be supplied intermittently, such as on a puff-by-puff basis. The power may be supplied to the aerosol-generating element in the form of pulses of electrical current. 
     The control body may comprise a power supply arranged to supply power to at least one of the control system, the thermal output element, and the aerosol-generating element. The aerosol-generating element may comprise an independent power supply. The aerosol-generating system or device may comprise a first power supply arranged to supply power to the control circuitry, a second power supply configured to supply power to the aerosol-generating element, and a third power supply configured to supply power to the thermal output element, or may comprise fewer power supplies that respectively are configured to supply power to any suitable combination of the control circuitry, the aerosol-generating element, and the thermal output element. 
     Each such power supply may be or include a DC power supply. The power supply may be or include a battery. The battery may be or include a lithium based battery, for example a lithium-cobalt, a lithium-iron-phosphate, a lithium titanate or a lithium-polymer battery. The battery may be or include a nickel-metal hydride battery or a nickel cadmium battery. The power supply may be or include another form of charge storage device such as a capacitor. Optionally, the power supply may require recharging and be configured for many cycles of charge and discharge. The power supply may have a capacity that allows for the storage of enough energy for one or more user experiences; for example, the 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 power supply may have sufficient capacity to allow for a predetermined number of puffs or discrete activations of the heating assembly. Preferably, the power supply further may have sufficient capacity to allow for any suitable number of actuations of the thermal output element. 
     The aerosol-generating system or device may be or include a handheld aerosol-generating system. The handheld aerosol-generating system may be configured to allow a user to puff on a mouthpiece to draw an aerosol through the mouth end opening. The aerosol-generating system may have a size comparable to a conventional cigar or cigarette. The aerosol-generating system optionally may have a total length between about 30 mm and about 150 mm. The aerosol-generating system may have an external diameter between about 5 mm and about 30 mm. 
     Optionally, the housing may be elongate. The housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics or composite materials containing one or more of those materials, or thermoplastics that are suitable for food or pharmaceutical applications, for example polypropylene, polyetheretherketone (PEEK) and polyethylene. The material may be light and non-brittle. 
     The thermal output element can be coupled to any suitable portion of the housing as to generate a user-perceptible temperature change. 
     The cartridge, control body or aerosol-generating system or device may comprise a puff detector in communication with the control circuitry. The puff detector may be configured to detect when a user draws through the airflow path. Additionally, or alternatively, the cartridge, control body or aerosol-generating system may comprise a temperature sensor in communication with the control circuitry. The cartridge, control body or aerosol-generating system or device may comprise a user input, such as a switch or button. The user input may enable a user to turn the system on and off. Optionally, the user input may be coupled to the thermal output device. Additionally, or alternatively, the cartridge, control body or aerosol-generating system or device optionally may comprise indication means for indicating the determined amount of aerosol-forming substrate held in the reservoir to a user. The control circuitry may be configured to activate the indication means after a determination of the amount of aerosol-forming substrate held in the reservoir has been made. The indication means optionally may comprise one or more of lights, such as light emitting diodes (LEDs), a display, such as an LCD display and audible indication means, such as a loudspeaker or buzzer and vibrating means. The control circuitry may be configured to light one or more of the lights, display an amount on the display, emit sounds via the loudspeaker or buzzer and vibrate the vibrating means. 
     Preferably, the control circuitry is configured to actuate the thermal output element so as to convey suitable information to the user. For example, the control circuitry optionally may be configured to actuate the thermal output element responsive to one or more of the following: the user turning on the system or device; the user turning off the system or device; the reservoir containing sufficient liquid or gel for a user experience; the reservoir containing insufficient liquid or gel for a user experience; the aerosol-generating element heating up; the aerosol-generating element being sufficiently heated to generate an aerosol; the battery level being low; the battery level being sufficient for a user experience; or indicating any other suitable system status or responsive to any other suitable user input. 
     The aerosol-forming substrate can have any suitable composition. For example, the aerosol-forming substrate may comprise nicotine. The nicotine containing aerosol-forming substrate may be or include a nicotine salt matrix. The aerosol-forming substrate may comprise plant-based material. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds, which are released from the aerosol-forming substrate upon heating. The aerosol-forming substrate may comprise homogenised tobacco material. The aerosol-forming substrate may comprise a non-tobacco-containing material. The aerosol-forming substrate may comprise homogenised plant-based material. 
     The aerosol-forming substrate may comprise one or more aerosol-formers. An aerosol-former is any suitable known compound or mixture of compounds that, in use, facilitates formation of a dense and stable aerosol and that is substantially resistant to thermal degradation at the temperature of operation of the system. Examples of suitable aerosol formers include glycerine and propylene glycol. Suitable aerosol-formers are well known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, 1,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. The aerosol-forming substrate may comprise water, solvents, ethanol, plant extracts and natural or artificial flavours. The aerosol-forming substrate may comprise nicotine and at least one aerosol former. The aerosol former may be glycerine or propylene glycol. The aerosol former may comprise both glycerine and propylene glycol. The aerosol-forming substrate may have a nicotine concentration of between about 0.5% and about 10%, for example about 2%. 
     It should be appreciated that the present thermal output elements are not limited to use with aerosol-generating systems or devices configured for use with liquid or gel aerosol-forming substrates. For example, in other configurations the present thermal output elements can be used with or included in aerosol-generating systems or devices that are configured for use with a solid aerosol-forming substrate. One type of aerosol-generating element that can be used with a solid-aerosol forming substrate includes a heater configured to be inserted into a solid aerosol-forming substrate, such as a plug of tobacco. 
     In some configurations, the heater is substantially blade-shaped for insertion into the aerosol-forming substrate and optionally has a length of between 10 mm and 60 mm, a width of between 2 mm and 10 mm, and a thickness of between 0.2 mm and 1 mm. A preferred length may be between 15 mm and 50 mm, for example between 18 mm and 30 mm. A preferred length may be about 19 mm or about 20 mm. A preferred width may be between 3 mm and 7 mm, for example between 4 mm and 6 mm. A preferred width may be about 5 mm. A preferred thickness may be between 0.25 mm and 0.5 mm. A preferred thickness may be about 0.4 mm. The heater can include an electrically-insulating heater substrate and an electrically-resistive heating element supported by the heater substrate. A through-hole optionally may be defined through the thickness of the heater. The heater mount may provide structural support to the heater and may allow the heater to be located within the aerosol-generating device. The heater mount optionally may be formed from a mouldable material that is moulded around a portion of the heater and may extend through the though-hole to couple to the heater to the heater mount. The heater optionally may have a tapered or pointed end to facilitate insertion into an aerosol-forming substrate. 
     The heater mount is preferably moulded to a portion of the heater that does not significantly increase in temperature during operation. Such a portion may be termed a holding portion and the heating element may have lower resistivity at this portion so that it does not heat up to a significant degree on the passage of an operational current. The through-hole may be located in the holding portion. The through-hole, if provided, may be formed in the heater before or after the electrically-resistive heating element is formed on the heater substrate. A device may be formed by fixing or coupling a heating assembly to, or within, a housing. The through-hole may be formed by machining, for example by laser machining or by drilling. 
     The heater mount may provide structural support to the heater and allows it to be securely fixed within an aerosol-generating device. The use of a mouldable material such as a mouldable polymer allows the heater mount to be moulded around the heater and thereby firmly hold the heater. It also allows the heater mount to be produced with a desired external shape and dimensions in an inexpensive manner. 
     Advantageously, the heating element may be formed from different materials. A first part, or heating part, of the heating element (i.e. that portion supported by the insertion or heating portion of the heater) may be formed from a first material and a holding part of the heating element (i.e. that part supported by a holding portion of the heater) may be formed from a second material, wherein the first material has a greater electrical resistivity coefficient than the second material. For example, the first material may be Ni—Cr (Nickel-Chromium), platinum, tungsten or alloy wire and the second material may be gold or silver or copper. The dimensions of the first and second parts of the heating element may also differ to provide for a lower electrical resistance per unit length in the second portion. 
     The heater substrate is formed from an electrically insulating material and may be a ceramic material such as Zirconia or Alumina. The heater substrate may provide a mechanically stable support for the heating element over a wide range of temperatures and may provide a rigid structure suitable for insertion into an aerosol-forming substrate. The heater substrate comprises a planar surface on which the heating element is positioned and may comprise a tapered end configured to allow for insertion into an aerosol-forming substrate. The heater substrate advantageously has a thermal conductivity of less than or equal to 2 Watts per metre Kelvin. 
     The aerosol-generating device preferably comprises a housing defining a cavity surrounding an insertion portion of the heater. The cavity is configured to receive an aerosol-forming article containing an aerosol-forming substrate. The heater mount may form a surface closing one end of the cavity. 
     In some configurations, the device is preferably a portable or handheld device that is comfortable to hold between the fingers of a single hand. 
     The power supply of the device may be any suitable power supply, for example a DC voltage source such as a battery. In one embodiment, the power supply is a Lithium-ion battery. Alternatively, the power supply may be a Nickel-metal hydride battery, a Nickel cadmium battery, or a Lithium based battery, for example a Lithium-Cobalt, a Lithium-Iron-Phosphate, Lithium Titanate or a Lithium-Polymer battery. 
     The device preferably comprises a control element. The control element may be a simple switch. Alternatively the control element may be electric circuitry and may comprise one or more microprocessors or microcontrollers, which may be configured to control the heater as well as the thermal output element. 
     The disclosure provides an aerosol-generating system comprising an aerosol-generating device as described above and one or more aerosol-forming articles configured to be received in a cavity of the aerosol-generating device. 
     During a usage session, an aerosol-generating article containing the aerosol-forming substrate may be partially contained within the aerosol-generating device. The aerosol-generating article may be substantially cylindrical in shape. The aerosol-generating article may be substantially elongate. The aerosol-generating article may have a length and a circumference substantially perpendicular to the length. The aerosol-forming substrate may be substantially cylindrical in shape. The aerosol-forming substrate may be substantially elongate. The aerosol-forming substrate may also have a length and a circumference substantially perpendicular to the length. The aerosol-generating article may have a total length between approximately 30 mm and approximately 100 mm. The aerosol-generating article may have an external diameter between approximately 5 mm and approximately 12 mm. 
     The solid aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds which are released from the substrate upon heating. Alternatively, the solid aerosol-forming substrate may comprise a non-tobacco material. The solid 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. 
     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 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. 
     As used herein, homogenised tobacco refers to material formed by agglomerating particulate tobacco. Homogenised tobacco may be in the form of a sheet. Homogenised tobacco material may have an aerosol-former content of greater than 5% on a dry weight basis. Homogenised tobacco material may alternatively have an aerosol former content of between 5% and 30% by weight on a dry weight basis. Sheets of homogenised tobacco material may be formed by agglomerating particulate tobacco obtained by grinding or otherwise combining one or both of tobacco leaf lamina and tobacco leaf stems. Alternatively, or in addition, sheets of homogenised tobacco material may comprise one or more of tobacco dust, tobacco fines and other particulate tobacco by-products formed during, for example, the treating, handling and shipping of tobacco. Sheets of homogenised tobacco material may comprise one or more intrinsic binders, that is tobacco endogenous binders, one or more extrinsic binders, that is tobacco exogenous binders, or a combination thereof to help agglomerate the particulate tobacco; alternatively, or in addition, sheets of homogenised tobacco material may comprise other additives including, but not limited to, tobacco and non-tobacco fibres, aerosol-formers, humectants, plasticisers, flavourants, fillers, aqueous and non-aqueous solvents and combinations thereof. 
     Optionally, the solid aerosol-forming substrate may be provided on or embedded in a thermally stable carrier. The carrier may take the form of powder, granules, pellets, shreds, spaghettis, strips or sheets. Alternatively, the carrier may be a tubular carrier having a thin layer of the solid substrate deposited on its inner surface, or on its outer surface, or on both its inner and outer surfaces. Such a tubular carrier may be formed of, for example, a paper, or paper like material, a non-woven carbon fibre mat, a low mass open mesh metallic screen, or a perforated metallic foil or any other thermally stable polymer matrix. 
     In some configurations, the aerosol-forming substrate comprises a gathered crimpled sheet of homogenised tobacco material. As used herein, the term ‘crimped sheet’ denotes a sheet having a plurality of substantially parallel ridges or corrugations. Preferably, when the aerosol-generating article has been assembled, the substantially parallel ridges or corrugations extend along or parallel to the longitudinal axis of the aerosol-generating article. This advantageously facilitates gathering of the crimped sheet of homogenised tobacco material to form the aerosol-forming substrate. However, it will be appreciated that crimped sheets of homogenised tobacco material for inclusion in the aerosol-generating article may alternatively or in addition have a plurality of substantially parallel ridges or corrugations that are disposed at an acute or obtuse angle to the longitudinal axis of the aerosol-generating article when the aerosol-generating article has been assembled. In certain embodiments, the aerosol-forming substrate may comprise a gathered sheet of homogenised tobacco material that is substantially evenly textured over substantially its entire surface. For example, the aerosol-forming substrate may comprise a gathered crimped sheet of homogenised tobacco material comprising a plurality of substantially parallel ridges or corrugations that are substantially evenly spaced-apart across the width of the sheet. 
     The solid aerosol-forming substrate may be deposited on the surface of the carrier in the form of, for example, a sheet, foam, gel or slurry. The solid aerosol-forming substrate may be deposited on the entire surface of the carrier, or alternatively, may be deposited in a pattern in order to provide a non-uniform flavour delivery during use. 
     It should be appreciated that although certain configurations described herein include aerosol-generating elements that generate aerosols via resistive heating, any suitable aerosol-generating element can be used, for example an inductive heating arrangement. 
     In a second embodiment of the invention, there is provided a method for generating an output in an aerosol-generating device. Optionally, the aerosol-generating device comprises a housing comprising an air inlet, an air outlet, an airflow path extending therebetween, and an aerosol-generating element disposed within the housing and configured to generate an aerosol. The method can include providing a thermal output element coupled to the housing, the thermal output element being distinct from the aerosol-generating element. The method further can include providing a circuit coupled to the thermal output element. The method further can include causing, by the circuit, the thermal output element to generate a user-perceptible temperature change. 
     Features of the aerosol-generating device of the first embodiment of the invention may be applied to the second embodiment of the invention. 
    
    
     
       Configurations of the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic illustration of a cross-section of an aerosol-generating system including an interface in accordance with the invention; 
         FIG. 2  is a schematic illustration of a cross-section of another aerosol-generating system including an interface in accordance with the invention; 
         FIG. 3A  is a schematic illustration of a cross-section of an exemplary interface, in accordance with the invention; 
         FIG. 3B  is a schematic illustration of a cross-section of an aerosol-generating system including the exemplary interface of  FIG. 3A  in accordance with the invention; 
         FIG. 3C  is a schematic illustration of an exemplary use of the aerosol-generating system of  FIG. 3B  including the exemplary interface of  FIG. 3A  in accordance with the invention; 
         FIGS. 4A-4F  are schematic illustrations of cross sections of interfaces including various exemplary thermal output elements for generating a user-perceptible temperature change, in accordance with the invention; 
         FIGS. 5A-5B  are schematic illustrations of cross sections of exemplary interfaces with integrated user-actuatable input elements and thermal output elements, in accordance with the invention; 
         FIGS. 6A-6D  are schematic illustrations of exemplary devices including interfaces, in accordance with the invention; and 
         FIG. 7  illustrates a flow of operations in an exemplary method, in accordance with the invention. 
     
    
    
     Configurations provided herein relate to an improved interface for an aerosol-generating system. The interface preferably includes a thermal output element that generates a user-perceptible temperature change for conveying information. Optionally, the interface further can include an input element. Optionally, the interface, e.g., thermal output element, has a clearly recognizable shape so that if the interface is included on multiple devices or versions of the present aerosol-generating system, the user can recognise the interface element. Additionally, or alternatively, the interface, e.g., thermal output element, optionally may be associated with one or more consistent, specific functions on the aerosol-generating system, such that after the user becomes familiar with the functionality of the interface, the user will immediately know the function of the interface on any other system or device which includes such an interface. Additionally, or alternatively, the present interface, e.g., thermal output element, optionally can include consistent components both in the aerosol-generating system and in any other systems and devices, such that after the user becomes familiar with the feel and interpretation of the interface, the user will immediately know how to interpret the interface on any other system or device which includes such an interface. 
     The present output elements may be used in any suitable aerosol-generating system or device therein. For example,  FIG. 1  is a schematic illustration of an aerosol-generating system  100  including an interface element  30  in accordance with the invention. The system  100  comprises two main components, a cartridge  20  containing a liquid or gel aerosol-forming substrate, and a control body  10 . A connection end of the cartridge  20  is removably connected to a corresponding connection end of the control body  10 . The control body  10  includes housing  11 , disposed within which is a battery  12 , which in one example is a rechargeable lithium ion battery, control circuitry  13 , and interface element  30  coupled to control circuitry  13  via electrical interconnect  31 . The aerosol-generating system  100  is portable and can have a size comparable to a conventional cigar or cigarette. For example, system  100  preferably is sized and shaped so as to be handheld, and preferably sized and shaped so as to be holdable in one hand, e.g., between a user&#39;s fingers. 
     The cartridge  20  comprises a housing  21  containing a heating assembly  25  and a reservoir  24 . A liquid or gel aerosol-forming substrate is held in the reservoir  24 . The upper portion of reservoir  24  is connected to the lower portion of the reservoir  24  illustrated in  FIG. 1 . The heating assembly  25  receives substrate from reservoir  24  and heats the substrate to generate a vapour, e.g., includes a resistive heating element coupled to controller  13  via electrical interconnects  26 ,  14  so as to receive power from battery  12 . One side of heating assembly  25  is in fluidic communication with reservoir  24  (for example, via fluidic channels  27 ) so as to receive the aerosol-forming substrate from reservoir  24 , e.g., by capillary action. The heating assembly  25  is configured to heat the aerosol-forming substrate to generate a vapour. 
     In the illustrated configuration, an air flow path  23  extends through the cartridge  20  from air inlet  15  (optionally which may be between control body  10  and cartridge  20 ), past the heating assembly  25 , and through a path  23  through reservoir  24  to a mouth end opening  22  in the cartridge housing  21 . The system  100  is configured so that a user can puff on the mouth end opening  22  of the cartridge  20  to draw aerosol into their mouth. In operation, when a user puffs on the mouth end opening  22 , air is drawn into and through the airflow path  23  from the air inlet  15  and past the heating assembly  25  as illustrated in dashed arrows in  FIG. 1 , and to the mouth end opening  22 . The control circuitry  13  controls the supply of electrical power from the battery  12  to the cartridge  20  via electrical interconnects  14  (in control body  10 ) coupled to electrical interconnects  26  (in cartridge  20 ) when the system is activated. This in turn controls the amount and properties of the vapour produced by the heating assembly  25 . The control circuitry  13  may include an airflow sensor (not specifically illustrated) and the control circuitry may  13  supply electrical power to the heating assembly  25  when the user puffs on the cartridge  20  as detected by the airflow sensor. This type of control arrangement is well established in aerosol-generating systems such as inhalers and e-cigarettes. When a user puffs on the mouth end opening  22  of the cartridge  20 , the heating assembly  25  is activated and generates a vapour that is entrained in the air flow passing through the air flow path  23 . Optionally, the vapour at least partially cools within the airflow path  23  to form an aerosol within the airflow path, which is then drawn into the user&#39;s mouth through the mouth end opening  22 . In some configurations, the vapour at least partially cools within the user&#39;s mouth to form an aerosol within the user&#39;s mouth. 
     Interface element  30  illustrated in  FIG. 1  includes a thermal output element configured to generate a user-perceptible temperature change responsive to actuation by control circuitry  13  via electrical interconnect  31 . The thermal output element can be configured, for example, so as to generate at least one temperature change (e.g., heating, or cooling, or heating and cooling sequentially) at interface element  30  or at a defined outer portion of housing  11  in such a manner that a user can perceive the temperature change, typically through the user&#39;s sense of touch. For example, in some configurations, the thermal output element may be selected from the group consisting of a thermoelectric device, a resistive member, an inductive member, and an infrared source. It should be appreciated that interface element  30  may be located at any suitable portion of aerosol-generating system  100  and is not limited to generating the user-perceptible temperature change only at an outer portion of housing  11  or other portion of control body  10 . For example, interface element  30  can be located at any suitable location of control body  10  or cartridge  20 , e.g., can be coupled to any suitable portion of housing  11  or housing  21  so as to generate a user-perceptible temperature change at any suitable outer portion of system  100 , e.g., any suitable portion of system  100  that may be touched by the user&#39;s lip, finger, or palm during use. 
     In some configurations, aerosol-generating system  100  further comprises an input element configured to generate an input signal. Circuit  13  can be configured to cause the thermal output element to generate the user-perceptible temperature change responsive to the input signal. Optionally, the input element is user-actuatable. In one non-limiting configuration, the thermal output element optionally is located sufficiently close to the input element that the user can perceive the temperature change while or after actuating the input element. As a further option, the input element and the thermal output element are arranged in a stack. Additionally, or alternatively, the input element optionally is selected from the group consisting of a mechanical button, a membrane button, a mechanical switch, a rotary encoder, a dial, a knob, a capacitive touch button, a resistive touch button, a joystick, a slider, a trigger button, a touch screen, and a magnetic switch. As another alternative, the input signal corresponds to a condition of the aerosol-generating device, e.g., need not necessarily be generated directly responsive to actuation of an input element. Additionally, or alternatively, system  100  optionally further includes a sensor coupled to the circuit  13  and configured to output to the circuit a temperature of the thermal output element of interface  30 . The circuit  13  optionally is configured to adjust operation of the thermal output element or to terminate operation of the thermal output element based on the temperature received from the sensor. 
     In some configurations, an aerosol-generating system  100  comprises an aerosol-generating device such as described herein, and a peripheral device in operable communication with the aerosol-generating device (not specifically illustrated in  FIG. 1 ). The peripheral device optionally is configured to transmit to the aerosol-generating device a signal corresponding to a condition of the aerosol-generating device. The circuit optionally is configured to cause the output element to generate the user-perceptible temperature change responsive to receipt of the signal. In nonlimiting configurations, the peripheral device optionally comprises a device charger, charging case, consumable holder, smartphone, tablet computer, personal computer, or vending machine. 
     In some configurations, the circuit determines a status of the device, and the user-perceptible temperature change indicates the status of the device. 
     In some configurations, an aerosol-generating system comprises an aerosol-generating device such as described herein and an aerosol-forming substrate, optionally wherein the aerosol-forming substrate comprises nicotine. 
       FIG. 2  is a schematic illustration of an alternative aerosol-generating system  200  including interface element  30 ′ in accordance with the invention. Interface element  30 ′ can include a thermal output element and can be configured similarly as interface  30  described with reference to  FIG. 1 . The system  200  comprises an aerosol-generating device having a housing  39 , and an aerosol-forming article  40 , for example a tobacco stick. The aerosol-forming article  40  includes an aerosol-forming substrate  41  that is pushed inside the housing  39  to come into thermal proximity with a portion of a heater  36 . Responsive to heating by heater  36 , the aerosol-forming substrate  41  will release a range of volatile compounds at different temperatures. 
     Within the housing  39  there is an electrical energy supply  32 , for example a rechargeable lithium ion battery. A controller  33  is connected to the heater  36  via electrical interconnects  34 , to the electrical energy supply  32 , and to interface  30 ′ via electrical interconnect  31 ′. The controller  33  controls the power supplied to the heater  36  in order to regulate its temperature, and actuates interface  30 ′ in a manner such as described elsewhere herein. Typically the aerosol-forming substrate is heated to a temperature of between 250 and 450 degrees centigrade. 
     The housing  39  of aerosol-generating device defines a cavity, open at the proximal end (or mouth end), for receiving an aerosol-generating article  40  for consumption. Optionally, system  200  includes element(s)  37  disposed within the cavity which, together with housing  39 , form(s) air inlet channels  38 . The distal end of the cavity is spanned by a heating assembly comprising heater  36  and a heater mount  35 . The heater  36  is retained by the heater mount  35  such that an active heating area (heating portion) of the heater  36  is located within the cavity. In one example, the heater  36  includes a through hole (not specifically illustrated) through which material of heater mount  35  extends so as to further secure heater  36  in place. The active heating area of the heater  36  is positioned within a distal end of the aerosol-generating article  40  when the aerosol-generating article  40  is fully received within the cavity. The heater mount  35  optionally may be formed from polyether ether ketone and may be moulded around a holding portion of the heater. The heater  36  optionally is shaped in the form of a blade terminating in a point. That is, the heater  36  optionally has a length dimension that is greater than its width dimension, which is greater than its thickness dimension. First and second faces of the heater  36  may be defined by the width and length of the heater. 
     An exemplary aerosol-forming article  40 , as illustrated in  FIG. 2 , can be described as follows. The aerosol-generating article  40  comprises three or more elements: an aerosol-forming substrate  41 , an intermediate element  42 , and a mouthpiece filter  43 . These elements may be arranged sequentially and in coaxial alignment and assembled by a cigarette paper (not specifically illustrated) to form a rod. In one nonlimiting configuration, when assembled, the aerosol-forming article  40  may be  45  millimetres long and have a diameter of  7  millimetres, although it should be appreciated that any other suitable combination of dimensions can be used. 
     The aerosol-forming substrate  41  optionally comprises a bundle of crimped cast-leaf tobacco wrapped in a filter paper (not shown) to form a plug. The cast-leaf tobacco includes one or more aerosol formers, such as glycerine. The intermediate element  42  may be located immediately adjacent the aerosol-forming substrate  41  The intermediate element  42  may be configured so as to locate the aerosol-forming substrate  41  towards the distal end of the article  40  so that it can be contacted with the heater  36 . Additionally, or alternatively, the intermediate element  42  may be configured so as to inhibit or prevent the aerosol-forming substrate  41  from being forced along the article  40  towards the mouthpiece when heater  36  is inserted into the aerosol-forming substrate  41 . Additionally, or alternatively, the intermediate element  42  may be configured so as to allow volatile substances released from the aerosol-forming substrate  41  to pass along the article towards the mouthpiece filter  43 . The volatile substances may cool within the transfer section to form an aerosol. In one nonlimiting configuration, intermediate element  42  may include or may be formed from a tube of cellulose acetate directly coupled to the aerosol-forming substrate. In one nonlimiting configuration, the tube defines an aperture having a diameter of 3 millimetres. Additionally, or alternatively, intermediate element  42  may include or be formed from a thin-walled tube of  18  millimetres in length directly coupled to the mouthpiece filter  43 . In one exemplary configuration, intermediate element  42  includes both such tubes. The mouthpiece filter  43  may be a conventional mouthpiece filter, e.g., formed from cellulose acetate, and having a length of approximately 7.5 millimetres. Elements  41 ,  42 , and  43  optionally are assembled by being tightly wrapped within a cigarette paper (not specifically illustrated), e.g., a standard (conventional) cigarette paper having standard properties or classification. The paper in this specific embodiment is a conventional cigarette paper. The interface between the paper and each of the elements  41 ,  42 ,  43  locates the elements and defines the aerosol-forming article  40 . 
     As the aerosol-generating article  40  is pushed into the cavity, the tapered point of the heater  36  engages with the aerosol-forming substrate  41 . By applying a force to the aerosol-forming article  40 , the heater  36  penetrates into the aerosol-forming substrate  41 . When the aerosol-forming article  40  is properly engaged, the heater  36  is inserted into the aerosol-forming substrate  41 . When the heater  36  is actuated, the aerosol-forming substrate  41  is warmed and volatile substances are generated or evolved. As a user draws on the mouthpiece filter  43 , air is drawn into the aerosol-forming article  40  via air inlet channels  38  and the volatile substances condense to form an inhalable aerosol. This aerosol passes through the mouthpiece filter  43  of the aerosol-forming article  40  and into the user&#39;s mouth. 
     Further exemplary configurations of the present interfaces are described with reference to  FIGS. 3A-3C, 4A-4F, and 5A-5B . 
       FIG. 3A  is a schematic illustration of a cross-section of an exemplary interface  300  that can be implemented as interface  30  illustrated in  FIG. 1  or interface  30 ′ illustrated in  FIG. 2 . Interface  300  illustrated in  FIG. 3A  can include user-actuatable input element  301 , sensor  302 , thermal output element  303 , suitable electrical connections  304  between elements of interface  300 , logic circuit  305 , and connections  306  to other elements of an aerosol-generating device or system such as system  100  illustrated in  FIG. 1  or system  200  illustrated in  FIG. 2 . Optionally, input element  301  may be stacked on top of and coupled to one or more of sensor(s)  302 , thermal output element  303 , logic circuit  305 , and connections  306  so as to provide an integrated interface element that may be incorporated into various types of devices in a consistent and relatively straightforward manner. For example,  FIG. 3B  is a schematic illustration of a cross-section of an aerosol-generating system  400  including the exemplary interface  300  of  FIG. 3A . Interface  300  may include housing  307  configured so as to securably couple other elements of interface  300  to one another such that interface  300  may be handled and installed as a single element. In simplified system  400 , housing  307  of interface  300  may be coupled to housing  411  such that input element  301  is user-actuatable via an aperture through the housing  411 , and optionally at a height which is higher than that of housing  411 . The connections  306  of interface  300  may be coupled to control circuitry  430 , for example so that control circuitry  430  may control operation of logic circuit  305  and provide power from battery  440  to power logic circuit  305 , input element  301 , and thermal output element  303 . In some configurations, connections  306  may include one or multiple pins that can be coupled, e.g., soldered, to a printed circuit board or other suitable components of system  400 . In other configurations, connections  306  may include a cable with a connector that plugs into a printed circuit board or other suitable components of system  400 . 
     Housing  307  may include one or multiple structures configured to hold together the other elements of interface  300 . Examples of structures that can form or be included in housing  307  include any suitable combination of a plastic case into which the other elements of interface  300  fit, fasteners such as screws or clamps that secure together the other elements of interface  300 , a cured resin fully or partially surrounding other elements of interface  300 , a visual feedback element such as a light emitting diode which optionally can be multi-coloured, and an audio feedback element such as a speaker, beeper, or buzzer. 
       FIG. 3C  is a schematic illustration of an exemplary use of the aerosol-generating system  400  of  FIG. 3B  including the exemplary interface  300  of  FIG. 3A . The user, using his or her finger  310 , can provide input  311  actuating input element  301  of interface  300 , e.g., by touching or depressing the input element. Responsive to such actuation, logic circuit  305  generates an input signal and transmits the input signal to control circuitry  430  of system  400  via connections  306 . Responsive to receiving the input signal, control circuitry  430  actuates thermal output element  303 , e.g., by transmitting an output signal to logic circuit  305  via connections  306 . Responsive to receiving such output signal, logic circuit  305  causes thermal output element  303  to generate a user-perceptible temperature change  312 . Because thermal output element  303  is sufficiently close to user-actuatable input element  301  (e.g., stacked under input element  301 ), the user can perceive the temperature change while or after actuating the input element. 
     It should be appreciated that elements of interface  300  can have any suitable arrangement relative to one another and to elements of aerosol-generating system  400 , and are not limited to the particular arrangement illustrated in  FIGS. 3A-3C . For example, in the nonlimiting configuration illustrated in  FIGS. 3A-3C , the thermal output element  303  is partially or fully located below (behind) user-actuatable input element  301  and in direct or indirect contact and thermal communication with user-actuatable input element  301  so as to readily transfer heat or cooling to element  301  and thereby make the temperature change readily perceivable to the user. Alternatively, the user-actuatable input element  301  may be arranged so as to be accessible from one or more other sides of interface  300  and the connections  306  may be arranged so as to be accessible from one or more other sides of interface  300 . In still other configurations, the thermal output element  303  can be partially or fully located above (over) user-actuatable input element  301  or at any other suitable location within interface  300  so as to be directly contactable by the user and thereby make the temperature change readily perceivable to the user. The user-actuatable input element  301  may be arranged so as to be accessible through thermal output element  303 , and the connections  306  may be arranged so as to be accessible from one or more other sides of interface  300 . Alternatively, the user-actuatable input element  301  and thermal output element  303  may be accessible from the same side as one another, e.g., arranged directly or indirectly next to each other, rather than stacked. 
     In other nonlimiting examples, thermal output element  303  and user-actuatable input element  301  may be fully or partially integrated with one another, such as a resistive heating wire (thermal output element) embedded in a button (user-actuatable input element), or a resistive coating (thermal output element) disposed on the surface of a button (user-actuatable input element). Optionally, thermal output element  303  and sensor  302  can be fully or partially integrated with user-actuatable input element  301 , e.g., a resistive heating coil (thermal output element) and temperature sensor both can be fully or partially integrated into a button (user-actuatable input element). In still other configurations, the thermal output element  303  and sensor  302  can be the same structure; for example, the resistance of a resistive member can indicate the temperature of the resistive member, obviating the need for a separate sensor  302 . Some exemplary configurations are described with reference to  FIGS. 4A-4F and 5A-5B , and others may be readily envisioned based on the teachings provided herein. Indeed, thermal output element  303  can have any suitable location within the present systems and devices, e.g., can be spaced apart from user-actuatable input element  301 , for example on the opposite side of interface  300  or even on another portion of the system or device. 
     Furthermore, it should be appreciated that thermal output element  303  can be actuated responsive to input signals that are generated responsive to any suitable condition or status of system  400  or any suitable user action, and the input signals need not necessarily be generated by interface element  300 . For example, the input signal received by control circuitry  430  can correspond to a condition of the aerosol-generating system  400 . Purely by way of example, control circuitry  430  can be in operable communication with battery  440  and configured to detect a condition of battery  440 . For example, control circuitry  430  can be configured to detect the level of charge storage by battery  440  and to compare such level to one or more thresholds. The level being determined to be above a first threshold (e.g., indicating a ‘full’ battery) can correspond to a first input signal to the control circuitry  430 , responsive to which the control circuitry can transmit a first output signal to logic circuit  305  of interface  300  causing actuation of thermal output element  303  communicating the ‘full’ battery status to the user. The level being determined to be below a second threshold (e.g., indicating an ‘empty’ battery) can correspond to a second input signal to the control circuitry  430 , responsive to which the control circuitry can transmit a second output signal to logic circuit  305  of interface  300  causing actuation of thermal output element  303  communicating the ‘empty’ battery status to the user. Control circuitry  430  optionally is configured so as to modulate thermal output element  303  so as to convey both such conditions to the user at different times than one another, e.g., by using a decreasing temperature to convey ‘empty’ battery status and an increasing temperature to convey ‘full’ battery status. 
     As another example, control circuitry  430  can be configured to detect the level of heating by aerosol-generating element  420  and to compare such level to one or more thresholds. The level being determined to be above a third threshold (e.g., indicating a ‘ready’ status of the aerosol-generating element) can correspond to a third input signal to the control circuitry  430 , responsive to which the control circuitry can transmit a third output signal to logic circuit  305  of interface  300  causing actuation of thermal output element  303  communicating the ‘ready’ status to the user. The level being determined to be below a second threshold (e.g., indicating a ‘not ready’ status of the aerosol-generating element) can correspond to a fourth input signal to the control circuitry  430 , responsive to which the control circuitry can transmit a fourth output signal to logic circuit  305  of interface  300  causing actuation of thermal output element  303  communicating the ‘not ready’ status to the user. Control circuitry  430  optionally is configured so as to modulate thermal output element  303  so as to convey both such conditions to the user at different times than one another, e.g., by using a decreasing temperature to convey ‘not ready’ status and an increasing temperature to convey ‘ready’ status. Additionally, control circuitry  430  optionally is configured such that modulations corresponding to the status of battery  440  are different from modulations corresponding to readiness of the aerosol-generating element  420 , thus facilitating use of interface  300  to communicate different types of information to the user. 
     Although  FIGS. 3A-3C  illustrate particular configurations of an interface  300 , it should be appreciated that any suitable configuration can be used. For example, in embodiments that include a user-actuatable input element  301 , such element optionally can be one of, or can include any suitable combination of, a mechanical button, a mechanical switch, a rotary encoder, a dial, a knob, a capacitive touch button, a resistive touch button, a joystick, a slider, or a trigger button. Or, for example, the user-actuatable input element  301  optionally can be one of, or can include any suitable combination of, a touch screen or a magnetic switch. In optional configurations in which the interface  300  includes multiple user-actuatable input elements  301 , optionally all of such elements are located on the same side of interface  300  as one another. Additionally, or alternatively, the user-actuatable interface element(s)  301  optionally can be configured at one of the outer sides of interface  300  (at a peripheral surface of interface  300 ) so that the element(s) can remain easily accessible by a user after the interface has been installed in a device. However, it should be appreciated that in some configurations one or more the user-actuatable interface element(s) may be inaccessible from any of the sides of the interface  300 . In various optional configurations of interface  300 , one or multiple thermal output elements  303  can be connected to logic circuit  305  so as to be actuated through one or multiple input signals which respectively can be generated responsive to actuation of the user-actuatable input element(s)  301  or can be generated responsive to one or more conditions of the aerosol-generating device or system of which the interface  300  is a part. 
     Optional sensor  302  can include one or multiple sensors optionally implemented in a feedback loop, for example by logic circuit  305  or by control circuitry  430 , to control the temperature change generated by thermal output element  303 . For example, sensor  302  can be used as an integrated safety feature which limits the maximum temperature generated by the thermal output element  303 . Illustratively, sensor  302  can be coupled so as to output to logic circuit  305  or control circuitry  430  a signal corresponding to the temperature of the thermal output element  303 , and logic circuit  305  or control circuitry  430  can be configured so as to adjust operation of the thermal output element (e.g., reduce heating by the thermal output element) or to terminate operation of the thermal output element based upon the signal corresponding to a temperature that exceeds a predetermined threshold. 
     Additionally, or alternatively, optional sensor  302  and logic circuit  305  or control circuitry  430  can be configured so as to determine whether a user has touched interface  300  for a certain amount of time, even if the user-actuatable input element  301  has not been actuated. For example, regardless of whether the user-actuatable input element  301  has not been actuated, sensor  302  can provide to logic circuit  305  or to control circuitry  430  a signal corresponding to a temperature of sensor  302 , which can correspond to a temperature of user-actuatable input element  301 . Prior to contact with a finger or palm of a user, user-actuatable input element  301  can have a first temperature, e.g., ambient (room) temperature, or a temperature that is different than ambient because of heat transferred from the aerosol-generating element or because of heat or cooling generated by thermal output element  303 , responsive to which sensor  302  may output a signal having a value corresponding to such temperature. Responsive to contact with the finger or palm of a user who is touching interface  300 , e.g., who is touching user-actuatable element  301 , the temperature of sensor  302  may increase or decrease to a second temperature, causing the value of the signal generated by sensor  300  to change correspondingly. Based on such changes in the value of the signal that sensor  302  generates, logic circuit  305  or control circuitry  430  can determine that the user&#39;s finger or palm was in contact with user-actuatable element  301 , e.g., was in such contact during generation of the user-perceptible temperature change by thermal output element  303 , and therefore can determine that the user received the information conveyed by such temperature change. As a further option, responsive to such determination, logic circuit  305  or control circuitry  430  can terminate operation of thermal output element  303 . 
     Thermal output element  303  of interface  300  can include any suitable element or combination of elements configured to generate a user-perceptible temperature change, for example at interface  300 , or at an outer portion of housing  411 , or at any other defined portion of system  400  that a user may touch during use. Examples of elements suitable for generating such a user-perceptible temperature change include, but are not limited to, thermoelectric devices, resistive members, inductive members, and infrared sources. One nonlimiting example of a thermoelectric device that can be provided as a thermal output element in the present interface is one or more Peltier elements. Optionally, the control circuitry  430  can be configured so as to cause current to flow in one direction through the Peltier element(s) so as selectively to cause the Peltier element(s) to generate a user-perceptible temperature increase. Additionally, or alternatively, the control circuitry  430  can be configured so as to cause current to flow in the other direction through the Peltier element(s) so as selectively to cause the Peltier element(s) to generate a user-perceptible temperature decrease. A configuration providing both heating and cooling can expand the amount of information that can be conveyed to a user via the same interface. Optionally, the thermal output element  303  and control circuitry  430  and logic circuit  305  can be configured so as to convey different types of information by switching between different types of temperature changes. Such switching optionally may be continuous, e.g., may make a continuous transition between different temperature changes. 
     It should be appreciated that the user-perceptible temperature changes generated by thermal output element  303  can be linked to any suitable user input, to any suitable condition of the aerosol-generating device or system, or any suitable combination of such inputs or conditions, so as to convey information to the user. The particular information to be conveyed by such user-perceptible temperature changes may vary based on the given device or system in which the thermal output element  303  is included. However, in preferred configurations the user-perceptible temperature change generated by thermal output element  303  may relate to the same parameter on the different devices. 
     Nonlimiting examples of resistive members that can be provided as a thermal output element in the present interface include resistive heating elements such as a resistive wire, a resistive coil, a sheet of resistive material, a sheet of resistive material cut into any shape, and a coating of resistive material. A nonlimiting example of inductive member that can be provided as a thermal output element in the present interface includes an induction heating element that heats a part of the interface or a part of the system or device. A nonlimiting example of an infrared source that can be provided as a thermal output element in the present interface includes an infrared light source. Another exemplary element suitable for generating a user-perceptible temperature change includes a heat exchanger in contact with a temperature changing component which is part of the device or system of which the interface is a part or is coupled to. Another exemplary element suitable for generating a user-perceptible temperature change includes a source of a flame, electric arc, plasma arc, exothermal chemical reaction, or explosion. Another exemplary element suitable for generating a user-perceptible temperature change includes use of a laser beam, such as a focused laser beam. Another exemplary element suitable for generating a user-perceptible temperature change includes elements for expanding or compressing gas within a fixed volume. Another exemplary element suitable for generating a user-perceptible temperature change includes elements for generating friction. 
       FIGS. 4A-4F  are schematic illustrations of cross sections of interfaces including various exemplary thermal output elements for generating a user-perceptible temperature change. It should be appreciated that any of the interfaces illustrated in  FIGS. 4A-4F  suitably can be used as interface  30  illustrated in  FIG. 1 , interface  30 ′ illustrated in  FIG. 2 , or interface  300  illustrated in  FIGS. 3A-3C . 
     The exemplary interface  460  illustrated in  FIG. 4A  includes user-actuatable input element  401 , sensor  402 , thermal output element  403 , suitable electrical connections  404  between elements of interface  460 , logic circuit  405 , and connections  406  (such as pins) to other elements of an aerosol-generating device or system such as system  100  illustrated in  FIG. 1 , system  200  illustrated in  FIG. 2 , or system  400  illustrated in  FIGS. 3B-3C . Optionally, input element  401  may be stacked on top of and coupled to one or more of sensor  402 , thermal output element  403 , logic circuit  405 , and connections  406  via housing  407  so as to provide an integrated interface element that may be incorporated into various types of devices in a consistent and relatively straightforward manner. In the configuration illustrated in  FIG. 4A , thermal output element  403  includes a resistive member, such as a resistive heating coil configured to generate heat responsive to actuation by logic circuit  405 , which in turn is configured to actuate the resistive heating coil by passing current through the coil responsive to an output signal received from control circuitry of the aerosol-generating device or system via connections  406 . The resistive heating coil of thermal output element  403  may be in direct or indirect contact and in thermal communication with user-actuatable input element  401 , and optionally also in direct or indirect contact with the housing of the device or system, so as to cause a user-perceptible temperature change, for example at the outer (upper) portion of user-actuatable input element  401  or at any other suitable (e.g., outer) defined portion of the housing of the aerosol-generating system or device that is in thermal communication with thermal output element  403 . 
     The exemplary interface  461  illustrated in  FIG. 4B  includes user-actuatable input element  411 , sensor  412 , thermal output element  413 , suitable electrical connections  414  between elements of interface  461 , logic circuit  415 , connections  416  (such as pins) to other elements of an aerosol-generating device or system such as system  100  illustrated in  FIG. 1 , system  200  illustrated in  FIG. 2 , or system  400  illustrated in  FIGS. 3B-3C , and optional housing  417  configured similarly as described elsewhere herein. In the configuration illustrated in  FIG. 4B , thermal output element  413  includes an alternative resistive member, such as a cut sheet of resistive heating material configured to generate heat responsive to actuation by logic circuit  415 , which in turn is configured to actuate the resistive heating material by passing current through the material responsive to an output signal received from control circuitry of the aerosol-generating device or system via connections  416 . The cut sheet of resistive heating material of thermal output element  413  may be in direct or indirect contact and in thermal communication with user-actuatable input element  411 , and additionally or alternatively in direct or indirect contact with the housing of the device or system, so as to cause a user-perceptible temperature change, for example at the outer (upper) portion of user-actuatable input element  411  or at any other suitable (e.g., outer) defined portion of the housing of the aerosol-generating system or device that is in thermal communication with thermal output element  413 . 
     The exemplary interface  462  illustrated in  FIG. 4C  includes user-actuatable input element  421 , sensor  422 , thermal output element  423 , suitable electrical connections  424  between elements of interface  462 , logic circuit  425 , connections  426  (such as pins) to other elements of an aerosol-generating device or system such as system  100  illustrated in  FIG. 1 , system  200  illustrated in  FIG. 2 , or system  400  illustrated in  FIGS. 3B-3C , and optional housing  427  configured similarly as described elsewhere herein. In the configuration illustrated in  FIG. 4C , thermal output element  423  includes inductive member, such as an induction coil wound around a portion of the user-actuatable input element  421  and configured to generate a user-perceptible temperature change by heating up that portion responsive to actuation by logic circuit  425 , which in turn is configured to actuate the induction coil by passing current through the coil responsive to an output signal received from control circuitry of the aerosol-generating device or system via connections  426 . The induction coil of thermal output element  423  may be in direct or indirect contact with user-actuatable input element  421  so as to cause a user-perceptible temperature change, for example at the outer (upper) portion of user-actuatable input element  421  or at any other suitable (e.g., outer) defined portion of the housing of the aerosol-generating system or device that is in thermal communication with thermal output element  423 . 
     The exemplary interface  463  illustrated in  FIG. 4D  includes user-actuatable input element  431 , sensor  432 , thermal output element  433 , suitable electrical connections  434  between elements of interface  463 , logic circuit  435 , connections  436  (such as pins) to other elements of an aerosol-generating device or system such as system  100  illustrated in  FIG. 1 , system  200  illustrated in  FIG. 2 , or system  400  illustrated in  FIGS. 3B-3C , and optional housing  437  configured similarly as described elsewhere herein. In the configuration illustrated in  FIG. 4D , thermal output element  433  includes a thermoelectric device, such as a Peltier element configured to generate cooling or heating responsive to actuation by logic circuit  435 , which in turn is configured to actuate the Peltier element by passing current in an appropriate direction through the element responsive to an output signal received from control circuitry of the aerosol-generating device or system via connections  436 . The Peltier element of thermal output element  433  may be in direct or indirect contact and in thermal communication with user-actuatable input element  431 , and additionally or alternatively in direct or indirect contact with the housing of the device or system, so as to cause a user-perceptible temperature change, for example at the outer (upper) portion of user-actuatable input element  431  or at any other suitable (e.g., outer) defined portion of the housing of the aerosol-generating system or device that is in thermal communication with thermal output element  433 . 
     The exemplary interface  464  illustrated in  FIG. 4E  includes user-actuatable input element  441 , sensor  442 , thermal output element  443 , suitable electrical connections  444  between elements of interface  464 , logic circuit  445 , connections  446  (such as pins) to other elements of an aerosol-generating device or system such as system  100  illustrated in  FIG. 1 , system  200  illustrated in  FIG. 2 , or system  400  illustrated in  FIGS. 3B-3C , and optional housing  447  configured similarly as described elsewhere herein. In the configuration illustrated in  FIG. 4E , thermal output element  443  includes another alternative resistive member, such as a coated layer of resistive heating material configured to generate heat responsive to actuation by logic circuit  445 , which in turn is configured to actuate the resistive heating coil by passing current through the material responsive to an output signal received from control circuitry of the aerosol-generating device or system via connections  446 . The coated layer of resistive heating material of thermal output element  443  may be disposed over and in direct or indirect contact and in thermal communication with user-actuatable input element  441 , and additionally or alternatively in direct or indirect contact with the housing of the device or system, so as to cause a user-perceptible temperature change, for example at the outer (upper) surface of the coated layer of resistive heating material or at any other suitable (e.g., outer) defined portion of the housing of the aerosol-generating system or device that is in thermal communication with thermal output element  443 . 
     The exemplary interface  465  illustrated in  FIG. 4F  includes user-actuatable input element  451 , sensor  452 , thermal output element  453 , suitable electrical connections  454  between elements of interface  465 , logic circuit  455 , connections  456  (such as pins) to other elements of an aerosol-generating device or system such as system  100  illustrated in  FIG. 1 , system  200  illustrated in  FIG. 2 , or system  400  illustrated in  FIGS. 3B-3C , and optional housing  457  configured similarly as described elsewhere herein. In the configuration illustrated in  FIG. 4F , thermal output element  453  includes an infrared source, such as an infrared light source configured to generate infrared light  458  responsive to actuation by logic circuit  455 , which in turn is configured to actuate the infrared source by passing current through the source responsive to an output signal received from control circuitry of the aerosol-generating device or system via connections  456 . The infrared light source of thermal output element  453  may be in direct or indirect contact with user-actuatable input element  451  and configured so as to irradiate the user-actuatable input element  451  with infrared light  458 , and additionally or alternatively in direct or indirect contact with the housing of the device or system, so as to cause a user-perceptible temperature change, for example at the outer (upper) portion of user-actuatable input element  451  or at any other suitable (e.g., outer) defined portion of the housing of the aerosol-generating system or device that is in thermal communication with thermal output element  453 . 
     It should be appreciated that the components of interfaces such as illustrated in  FIGS. 3A-3C and 4A-4F  can have any suitable configuration and are not limited to the specifically illustrated elements or arrangements of elements. For example, certain elements of the interfaces optionally may be fully or partially integrated with one another. Illustratively,  FIGS. 5A-5B  are schematic illustrations of cross sections of exemplary interfaces with integrated user-actuatable input elements and thermal output elements. The exemplary interface  560  illustrated in  FIG. 5A  includes user-actuatable input element  501  into which sensor  502  and thermal output element  503  are fully or partially integrated, suitable electrical connections  504  between elements of interface  560 , logic circuit  505 , housing  507 , and connections  506  (such as pins) to other elements of an aerosol-generating device or system such as system  100  illustrated in  FIG. 1 , system  200  illustrated in  FIG. 2 , or system  400  illustrated in  FIGS. 3B-3C . In the configuration illustrated in  FIG. 5A , thermal output element  503  is fully or partially embedded in user-actuatable input element  501 . Additionally, or alternatively, optional sensor  502  is fully or partially embedded in user-actuatable input element  501 . In the configuration illustrated in  FIG. 5A , thermal output element  503  includes a resistive member, such as a resistive heating coil configured to generate heat responsive to actuation by logic circuit  505 , which in turn is configured to actuate the resistive heating coil by passing current through the coil responsive to an output signal received from control circuitry of the aerosol-generating device or system via connections  506 . However, it should be appreciated that any other type of thermal output element, including but not limited to those described herein, suitably may be integrated with (e.g., embedded within) user-actuatable input element  501 . As such, any suitable thermal output element  503  may be in direct contact and in thermal communication with user-actuatable input element  501 , and optionally also in indirect contact with the housing of the device or system, so as to cause a user-perceptible temperature change, for example at the outer (upper) portion of user-actuatable input element  501  or at any other suitable (e.g., outer) defined portion of the housing of the aerosol-generating system or device that is in thermal communication with thermal output element  503 . 
     The exemplary interface  561  illustrated in  FIG. 5B  includes user-actuatable input element  511 , sensor  512  partially or fully embedded within user-actuatable input element  511 , thermal output element  513 , suitable electrical connections  514  between elements of interface  561 , logic circuit  515 , connections  516  (such as pins) to other elements of an aerosol-generating device or system such as system  100  illustrated in  FIG. 1 , system  200  illustrated in  FIG. 2 , or system  400  illustrated in  FIGS. 3B-3C , and optional housing  517  configured similarly as described elsewhere herein. In the configuration illustrated in  FIG. 5B , thermal output element  513  includes an alternative resistive member, such as a coated layer of resistive heating material configured to generate heat responsive to actuation by logic circuit  515 , which in turn is configured to actuate the resistive heating coil by passing current through the material responsive to an output signal received from control circuitry of the aerosol-generating device or system via connections  516 . The coated layer of resistive heating material of thermal output element  513  may be disposed over and in direct or indirect contact and in thermal communication with user-actuatable input element  511 , and optionally also in direct or indirect contact with the housing of the device or system, so as to cause a user-perceptible temperature change, for example at the outer (upper) surface of the coated layer of resistive heating material or at any other suitable (e.g., outer) defined portion of the housing of the aerosol-generating system or device that is in thermal communication with thermal output element  513 . 
     Additionally, it should be appreciated that the user-actuatable input element, sensor, housing, and logic circuit and the particular configurations of electrical connections are not essential elements of the present invention. For example, any of the interfaces illustrated in  FIGS. 3A-3C, 4A-4F, and 5A-5B  suitably can omit any suitable ones of the user-actuatable input element, sensor, housing, logic circuit, and any appropriate electrical connections. 
     The present thermal output elements may be used to convey any suitable information to a user via one or more user-perceptible temperature changes. For example, any suitable combination of a logic circuit coupled to the thermal output element and control circuitry of the aerosol-generating device or system may be configured so as to actuate the thermal output element responsive to an input signal. The input signal can have any suitable source within or outside of the aerosol-generating device or system. For example, a condition of the aerosol-generating device can cause the circuit to generate the input signal based upon which the thermal output element is actuated. That is, the input signal optionally corresponds to a condition of the aerosol-generating device. A variety of suitable conditions and statuses readily may be envisioned. 
     Illustratively, the condition may correspond to a status of a particular component of the aerosol-generating device. As one example, the user-perceptible temperature change (e.g., increase in temperature) can correspond to the temperature of the aerosol-generating element while the aerosol-generating element is warming up. As another example, the user-perceptible temperature change can correspond to the aerosol-generating element being ready to generate an aerosol (e.g., sufficiently pre-heated). As another example, the user-perceptible temperature change can correspond to the aerosol-generating element not yet being ready to generate an aerosol (e.g., not sufficiently pre-heated). As another example, the user-perceptible temperature change can correspond to an amount of the aerosol-forming substrate being insufficient to generate an aerosol or insufficient for a complete user experience (e.g., usage session). As another example, the user-perceptible temperature change can correspond to the charge level of the power supply. As another example, the user-perceptible temperature change can correspond to an aerosol-generating article being correctly positioned within the device or system. As another example, the user-perceptible temperature change can correspond to the device or system needing to be cleaned. 
     Additionally, or alternatively, the condition may correspond to the user&#39;s use of the aerosol-generating device. For example, the user-perceptible temperature change can correspond to the user experience (e.g., usage session) being over or almost over. As another example, the user-perceptible temperature change can correspond to user&#39;s consumption of the aerosol within a given time period, such as over the course of a usage session or over the course of a day. As another example, the user-perceptible temperature change can correspond to the user&#39;s consumption of the aerosol exceeding a threshold within a given time period, such as exceeding a threshold during a usage session or during the course of a day. As another example, the user-perceptible temperature change can correspond to use of a counterfeit aerosol-generating article with the device or system. As another example, the user-perceptible temperature change can correspond to the user&#39;s consumption of the aerosol exceeding a threshold within a given time period, such as exceeding a threshold during a usage session or during the course of a day. As another example, the user-perceptible temperature change can correspond to the length of the user&#39;s puff, or to the length of the user&#39;s puff exceeding a threshold. As another example, the user-perceptible temperature change can correspond to the device or system not being unlocked (for example using the aerosol-generating device or a peripheral device) before it is attempted to be used. 
     Optionally, any user-perceptible temperature change can be sufficiently high as to be unpleasant for the user, whilst still being safe for the user. Unpleasant user-perceptible temperature changes may be, for example, about 5 degrees Celsius or greater, or about 10 degrees Celsius or greater, for example in a range of about 5 degrees Celsius to about 10 degrees Celsius. Pleasant user-perceptible changes may be, for example, about 5 degrees Celsius or less, or about 2 degrees Celsius or less. 
     Any suitable combination of information may be conveyed to the user via corresponding user-perceptible temperature changes. Indeed, different user-perceptible temperature changes may be used to convey multiple different types of information. For example, a pleasant, warm user-perceptible temperature change may be used to convey when the aerosol-forming substrate is ready for consumption; an unpleasant, warm user-perceptible temperature change may be used to convey that someone is trying to use the device without unlocking it; and a pleasant, cold user-perceptible temperature change may be used to convey that the device or system needs to be cleaned. As another example, a pleasant, warm user-perceptible temperature change may be used to convey when the aerosol-forming substrate is ready for consumption; and a pleasant, cold user-perceptible temperature change may be used to convey that the aerosol-generating article needs to be replaced or refilled. As another example, a pleasant user-perceptible temperature may increase over the course of a usage session; and a pleasant, cold user-perceptible temperature change may be used to convey the end of the usage session. 
     Additionally, or alternatively, actuation of an input element (such as a user-actuatable input element) can generate the input signal based upon which the thermal output element is actuated. That is, the device or system optionally includes an input element configured to generate an input signal, wherein an appropriate circuit of the device or system is configured to cause the thermal output element to generate the user-perceptible temperature change responsive to the input signal. Nonlimiting configurations of interfaces that include a user-actuatable input element and a thermal output element are provided elsewhere herein, such as with reference to  FIGS. 3A-3C, 4A-4F, and 5A-5B . 
     Interfaces including a thermal output element optionally may include one or more other elements, such as an optional user-actuatable interface element or to an optional sensor. The thermal output element and any other elements preferably are fixedly coupled to one another so as to be immovable relative to one another before or after installation in a device. For example, some configurations of the present thermal output element optionally include a housing configured to securably couple the thermal output element to one or more other elements, such as an optional user-actuatable interface element or to an optional sensor. However, it should be appreciated that the thermal output element and any other elements can be coupled to one another in any suitable arrangement, for example connected by flexible conductors, such as wires, that provide the elements with some freedom of movement relative to one another. 
     Regardless of the particular manner in which the thermal output element and any other elements of the interface are coupled to one another, the interface can be included in any suitable device or system, including but not limiting to an aerosol-generating device or system, and in any suitable element of such a device or system. An aerosol-generating system can include an aerosol-generating device that includes a thermal output element, e.g., a device such as device  100 ,  200 , or  400 , and optionally can include one or more peripheral devices. Examples of peripheral devices that can be included in the present aerosol-generating systems include, but are not limited to, one or multiple of a charger for the aerosol-generating device, a charging case for the aerosol-generating device, a holder for one or more aerosol-generating articles, a smartphone, tablet computer, or personal computer configured to communicate directly or indirectly with the aerosol-generating device, or a vending machine configured to sell the aerosol-generating device or aerosol-generating articles. Optionally, one or more of such peripheral devices can include the present interface. In some configurations, the interface has a consistent appearance or a consistent function, or a consistent appearance and a consistent function, in each such aerosol-generating device or peripheral device (if any) in which the interface is included. 
     For example,  FIGS. 6A-6D  are schematic illustrations of exemplary devices including the present interfaces.  FIG. 6A  illustrates an aerosol-generating device  600  including interface  601  that includes a thermal output element coupled to a housing of device  600 .  FIG. 6B  illustrates an exemplary peripheral device, such as a charging case  610  for an aerosol-generating device, including interface  611  that includes a thermal output element coupled to a housing of the device and having a consistent appearance or consistent function, or a consistent appearance and a consistent function, as interface  601 .  FIG. 6C  illustrates another exemplary peripheral device, such as a holder  620  for a plurality of aerosol-generating articles, including interface  621  that includes a thermal output element coupled to a housing of the device and having a consistent appearance or consistent function, or a consistent appearance and a consistent function, as interfaces  601  and  611 . 
       FIG. 6D  illustrates an exemplary element of an aerosol-forming system, such as aerosol-generating article  630  (which optionally holds a liquid or gel aerosol-forming substrate), including interface  631  that includes a thermal output element coupled to a housing of the article and having a consistent appearance or consistent function, or a consistent appearance and a consistent function, as interfaces  601 ,  611 , and  621 . By including such consistent interfaces on multiple devices, consistent information may be consistently conveyed through the thermal output element, thus improving the user&#39;s interaction with different elements of the aerosol-generating system. 
       FIG. 7  illustrates a flow of operations in an exemplary method  70 . Although the operations of method  70  are described with reference to elements of systems  100 ,  200 , and  400  it should be appreciated that the operations can be implemented by any other suitably configured systems or devices. 
     Method  70  includes providing a thermal output element coupled to a housing of an aerosol-generating device ( 71 ). The aerosol-generating device may include an aerosol-generating element configured to generate an aerosol using any suitable aerosol-forming substrate, such as a liquid, gel, or solid. The thermal output element may be provided as part of an interface that optionally includes any suitable combination of one or more other elements, such as one or more sensors, one or more user-actuatable interface elements, or one or more logic circuits, in any suitable configuration relative to one another and relative to the housing of the aerosol-generating device. Nonlimiting examples of aerosol-generating devices are described herein with reference to  FIGS. 1, 2, and 3B-3C . Nonlimiting examples of interfaces including thermal output elements are described herein with reference to  FIGS. 1, 2, 3A-3C, 4A-4F, 5A-5B, and 6A-6D . 
     Method  70  illustrated in  FIG. 7  includes providing a circuit coupled to the thermal output element ( 72 ). For example, in some configurations such as described with reference to  FIGS. 3A-3C, 4A-4F, and 5A-5B , the thermal output element optionally is coupled to a logic circuit provided as part of an interface, and the logic circuit is configured to actuate the thermal output element. As a further option, the logic circuit optionally is coupled to control circuitry of the aerosol-generating device, and the control circuitry is configured to cause the logic circuit to actuate the thermal output element. Alternatively, the thermal output element optionally is coupled to the control circuitry of the aerosol-generating device without such a logic circuit, and the control circuitry is configured to actuate the thermal output element. Any other suitable circuit coupled to the thermal output element can be provided. 
     Method  70  illustrated in  FIG. 7  also includes causing, by the circuit, the thermal output element to generate a user-perceptible temperature change ( 73 ). For example, in some configurations such as described with reference to  FIGS. 3A-3C, 4A-4F, and 5A-5B , the circuit optionally may actuate the thermal output element responsive to actuation of a user-actuatable interface element. Additionally, or alternatively, the circuit optionally may actuate the thermal output element based on a condition of the aerosol-generating device. Various options for actuating the thermal output element are described elsewhere herein. 
     Although some configurations of the invention have been described in relation to a system comprising a control body and a separate but connectable cartridge, it should be clear that the elements suitably can be provided in a one-piece aerosol-generating system. 
     It should also be clear that alternative configurations are possible within the scope of the invention. For example, the present thermal output elements suitably may be integrated into any type of device or system, and are not limited to use in aerosol-generating devices and systems. Illustratively, the present thermal output elements may be included in medical devices, smartphones, or the like.