The invention relates to an aerosol-generating device. The invention further relates to an aerosol-generating system comprising an aerosol-generating device and an aerosolgenerating article comprising aerosol-forming substrate. The invention further relates to a method for detecting the depletion degree of an aerosol-forming substrate of an aerosolgenerating article in an aerosol-generating device.

It is known to provide an aerosol-generating device for generating an inhalable vapor. Such devices may heat aerosol-forming substrate to a temperature at which one or more components of the aerosol-forming substrate are volatilised without burning the aerosolforming substrate. Aerosol-forming substrate may be provided as part of an aerosol-generating article. The aerosol-generating article may have a rod shape for insertion of the aerosolgenerating article into a cavity, such as a heating chamber, of the aerosol-generating device. A heating element may be arranged in or around the heating chamber for heating the aerosolforming substrate once the aerosol-generating article is inserted into the heating chamber of the aerosol-generating device.

It would be desirable to have an aerosol-generating device enabling a user to know when the aerosol-generating article is depleted. It would be desirable to have an aerosolgenerating device enabling a user to know the stage of the consumption of the aerosolgenerating article.

According to an embodiment of the invention there is provided an aerosol-generating device that may comprise a cavity for receiving an aerosol-forming substrate. The aerosolgenerating device may further comprise an airflow channel through the cavity. The aerosolgenerating device may further comprise a substrate sensor. The substrate sensor may be arranged in or adjacent the cavity. The substrate sensor may be configured to detect a depletion degree of the aerosol-forming substrate.

According to an embodiment of the invention there is provided an aerosol-generating device comprising a cavity for receiving an aerosol-forming substrate. The aerosol-generating device further comprises an airflow channel through the cavity. The aerosol-generating device further comprises a substrate sensor. The substrate sensor is arranged in or adjacent the cavity. The substrate sensor is configured to detect a depletion degree of the aerosol-forming substrate.

According to an embodiment of the invention there is provided an aerosol-generating device that may comprise a cavity for receiving an aerosol-forming substrate. The aerosolgenerating device may further comprise an upstream airflow channel through the cavity. The aerosol-generating device may further comprise a substrate sensor arranged to fluidically interface with the upstream airflow channel. The substrate sensor may be configured to detect a depletion degree of the aerosol-forming substrate.

According to an embodiment of the invention there is provided an aerosol-generating device comprising a cavity for receiving an aerosol-forming substrate. The aerosol-generating device further comprises an upstream airflow channel through the cavity. The aerosolgenerating device further comprises a substrate sensor arranged to fluidically interface with the upstream airflow channel. The substrate sensor is configured to detect a depletion degree of the aerosol-forming substrate.

Detecting the depletion degree of the aerosol-forming substrate enables a user to know the depletion stage of the aerosol-forming substrate. A user may thus know when the aerosolforming substrate is depleted and when new aerosol-forming substrate needs to be received in the cavity.

The substrate sensor may be a pH sensor.

During the ongoing depletion of the aerosol-forming substrate, the pH value of the aerosol-forming substrate may change. This change in the pH value of the aerosol-forming substrate may be detected by the sensor.

The substrate sensor may have a measurement range of between 2 pH and 10 pH, preferably of between 3 pH and 9 pH, most preferably of between 5 pH and 8 pH.

The substrate sensor may have a measurement accuracy at pH 7 of ± 0.02 pH, preferably the substrate sensor has a measurement accuracy at pH 7 of ± 0.01 pH.

The substrate sensor may have a drift at pH 7 of less than 0.05 pH per day.

The aerosol-generating device may be configured to heat the aerosol-forming substrate to a temperature above which aerosol is generated during puffs and in between puffs. In between puffs, the vaporizable material from the aerosol-forming substrate may be vaporized due to the temperature to which the aerosol-forming substrate is heated in between puffs. When a consumer draws on the aerosol-generating device or on the aerosol-forming substrate, the vaporized vaporizable material may be entrained in the airflow to generate an inhalable aerosol.

The substrate sensor may be configured to measure the depletion rate, preferably the pH value, of the aerosol-forming substrate in between puffs.

Measuring the depletion rate of the aerosol-forming substrate in between puffs may have the advantage that the depletion rate may be accurately determined. During a puff, air may flow through the device and the vaporized vaporizable substrate of the aerosol-forming substrate may be entrained in the airflow. It may be difficult to measure an accurate depletion rate of the aerosol-forming substrate during a puff. However, in between a puff, no airflow flows through the device so that a depletion rate measurement of the vaporized vaporizable material from the aerosol-forming substrate may be more accurate. Further, the vaporized vaporizable material from the aerosol-forming substrate may reach the substrate sensor to improve the accuracy of the measurement in between puffs due to the lack of an airflow through the aerosol-generating device.

The substrate sensor may be arranged in or adjacent an upstream end of the cavity.

The upstream end of the cavity may be a base of the cavity. When aerosol-forming substrate is received in the cavity, the aerosol-forming substrate may be arranged adjacent the upstream end of the cavity. In other words, when aerosol-forming substrate is received in the cavity, the aerosol-forming substrate may be received directly downstream of the upstream end of the cavity. By placing the substrate sensor in or adjacent the upstream end of the cavity, the substrate sensor may be placed in the area next to the area were the vaporizable material of the aerosol-forming substrate is vaporized in the cavity. Particularly in between puffs, the vaporized vaporizable material from the aerosol-forming substrate may slightly expand and flow towards the substrate sensor to enable an accurate measurement due to the small distance between the aerosol-forming substrate and the substrate sensor.

The substrate sensor may be arranged adjacent the airflow channel. The airflow channel may be a central airflow channel. The substrate sensor may be in direct contact with the airflow channel. The substrate sensor may be part of the airflow channel. The substrate sensor may comprise one or more air channels that the part of the airflow channel. Preferably, the substrate comprises at least two, preferably a multitude, of air channels that are part of the airflow channel. The air channels may be arranged in a ring-shaped arrangement to allow lateral airflow from all directions towards the aperture in the upstream end of the cavity.

The airflow channel may enter the cavity at the upstream end of the cavity. The cavity may comprise an aperture to allow air to flow into the cavity from the airflow channel. The aperture may be centrally arranged at the upstream end of the cavity. The substrate sensor may be arranged directly adjacent the aperture at the upstream end of the cavity. The substrate sensor may partly form the aperture. The aperture may be arranged in the substrate sensor. The aperture may be part of the substrate sensor.

The substrate sensor may be configured to detect a nicotine content of aerosol being drawn through the airflow channel.

The substrate sensor may be configured to detect the nicotine content of the aerosolforming substrate. The substrate sensor may be configured to detect the nicotine content of vaporized vaporizable material of the aerosol-forming substrate. The substrate sensor may be configured to detect the nicotine content during a puff. Alternatively, the substrate sensor may be configured to detect the nicotine content in between puffs. As a further alternative, the substrate sensor may be configured to detect the nicotine content of the generated aerosol during a puff and of the vaporized vaporizable material of the aerosol-forming substrate is between puffs. The substrate sensor may be configured to detect a pH value of aerosol being drawn through the airflow channel.

The substrate sensor may be configured to detect the pH value of the aerosol-forming substrate. The substrate sensor may be configured to detect the pH value of vaporized vaporizable material of the aerosol-forming substrate. The substrate sensor may be configured to detect the pH value during a puff. Alternatively, the substrate sensor may be configured to detect the pH value in between puffs. As a further alternative, the substrate sensor may be configured to detect the pH value of the generated aerosol during a puff and of the vaporized vaporizable material of the aerosol-forming substrate is between puffs.

The aerosol-generating device may further comprise a controller. The controller may be configured to generate a signal, based upon the output of the substrate sensor, if the depletion degree of the aerosol-forming substrate falls under a predetermined threshold.

The signal may be indicative of the depletion degree of the aerosol-forming substrate. The aerosol-generating device may be configured to output the signal to the consumer.

The signal may be one or more of a signal of a user interface, a light emitting signal, a sound signal and a vibration signal.

The signal may comprise information to a user when the aerosol-forming substrate has to be renewed. The signal may comprise information to a user when the aerosol-forming substrate is depleted. The signal may comprise information to a user of a change interval of the aerosol-forming substrate.

The controller may be configured to end the operation of the aerosol-generating device after a predetermined time or a predetermined number of puffs of a user, if the depletion degree of the aerosol-forming substrate may be under the predetermined threshold.

The controller may be configured and the operation of the aerosol-generating device, if the depletion degree of the aerosol-forming substrate may be under the predetermined threshold.

The depletion degree of the aerosol-forming substrate may be a nicotine content or a pH value of aerosol being drawn through the airflow channel.

The depletion degree of the aerosol-forming substrate may be a nicotine content or a pH value of aerosol during a draw of the user. The depletion degree of the aerosol-forming substrate may be a nicotine content or a pH value of the vaporized vaporizable material of the aerosol-forming substrate in between uses of the aerosol-generating device. The depletion degree of the aerosol-forming substrate may be a nicotine content or a pH value of both aerosol during a draw of the user and of the vaporized vaporizable material of the aerosol-forming substrate in between uses of the aerosol-generating device.

The aerosol-generating device may further have an activation button. The substrate sensor may be configured to start detecting the depletion degree of the aerosol-forming substrate after a predetermined time after pressing of the activation button or after a predetermined number of puffs of a user after pressing of the activation button.

Alternatively, the substrate sensor may be configured to a detection of the depletion rate of the aerosol-forming substrate immediately after the activation button is pressed. As a further alternative, the substrate sensor may be configured to conduct a depletion rate analysis of the aerosol-forming substrate immediately after the activation button is pressed and to only allow activation of the aerosol-generating device when the depletion rate of the aerosol-forming substrate is found not to be under the predetermined threshold.

The substrate sensor may be configured to detect the depletion degree of the aerosolforming substrate continuously during the operation of the aerosol-generating device or close to an estimated depletion of the aerosol-forming substrate. The depletion estimation may be based upon the predetermined time after pressing of the activation button or upon the predetermined number of puffs of a user after pressing of the activation button.

The invention further relates to an aerosol-generating system comprising an aerosolgenerating device as described herein and an aerosol-generating article comprising aerosolforming substrate.

The invention further relates to a method for detecting the depletion degree of an aerosol-forming substrate of an aerosol-generating article in an aerosol-generating device as described herein, the method comprising: detecting, by the substrate sensor, a depletion degree of the aerosol-forming substrate.

As used herein, the terms ‘proximal’, ‘distal’, ‘downstream’ and ‘upstream’ are used to describe the relative positions of components, or portions of components, of the aerosolgenerating device in relation to the direction in which a user draws on the aerosol-generating device during use thereof.

The aerosol-generating device may comprise a mouth end through which in use an aerosol exits the aerosol-generating device and is delivered to a user. The mouth end may also be referred to as the proximal end. In use, a user draws on the proximal or mouth end of the aerosol-generating device in order to inhale an aerosol generated by the aerosolgenerating device. Alternatively, a user may directly draw on an aerosol-generating article inserted into an opening at the proximal end of the aerosol-generating device. The opening at the proximal end may be an opening of the cavity. The cavity may be configured to receive the aerosol-generating article. The aerosol-generating device comprises a distal end opposed to the proximal or mouth end. The proximal or mouth end of the aerosol-generating device may also be referred to as the downstream end and the distal end of the aerosol-generating device may also be referred to as the upstream end. Components, or portions of components, of the aerosol-generating device may be described as being upstream or downstream of one another based on their relative positions between the proximal, downstream or mouth end and the distal or upstream end of the aerosol-generating device.

As used herein, an ‘aerosol-generating device’ relates to a device that interacts with an aerosol-forming substrate to generate an aerosol. The aerosol-forming substrate may be part of an aerosol-generating article, for example part of a smoking article. An aerosol-generating device may be a smoking device that interacts with an aerosol-forming substrate of an aerosolgenerating article to generate an aerosol that is directly inhalable into a user’s lungs thorough the user's mouth. An aerosol-generating device may be a holder. The device may be an electrically heated smoking device. The aerosol-generating device may comprise a housing, electric circuitry, a power supply, a heating chamber and a heating element.

As used herein with reference to the present invention, the term ‘smoking’ with reference to a device, article, system, substrate, or otherwise does not refer to conventional smoking in which an aerosol-forming substrate is fully or at least partially combusted. The aerosol-generating device of the present invention is arranged to heat the aerosol-forming substrate to a temperature below a combustion temperature of the aerosol-forming substrate, but at or above a temperature at which one or more volatile compounds of the aerosol-forming substrate are released to form an inhalable aerosol.

The aerosol-generating device may comprise electric circuitry. The electric circuitry may comprise a microprocessor, which may be a programmable microprocessor. The microprocessor may be part of a controller. The electric circuitry may comprise further electronic components. The electric circuitry may be configured to regulate a supply of power to the heating element. Power may be supplied to the heating element continuously following activation of the aerosol-generating device or may be supplied intermittently, such as on a puff- by-puff basis. The power may be supplied to the heating element in the form of pulses of electrical current. The electric circuitry may be configured to monitor the electrical resistance of the heating element, and preferably to control the supply of power to the heating element dependent on the electrical resistance of the heating element.

The aerosol-generating device may comprise a power supply, typically a battery, within a main body of the aerosol-generating device. 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. As an alternative, the power supply may be another form of charge storage device such as a capacitor. The power supply may require recharging and may have a capacity that enables to store enough energy for one or more usage experiences; for example, the power supply may have sufficient capacity to continuously generate aerosol for a period of around six minutes or for a period of a multiple of six minutes. In another example, the power supply may have sufficient capacity to provide a predetermined number of puffs or discrete activations of the heating element.

The cavity of the aerosol-generating device may have an open end into which the aerosol-generating article is inserted. The open end may be a proximal end. The cavity may have a closed end opposite the open end. The closed end may be the base of the cavity. The closed end may be closed except for the provision of air apertures arranged in the base. The base of the cavity may be flat. The base of the cavity may be circular. The base of the cavity may be arranged upstream of the cavity. The open end may be arranged downstream of the cavity. The cavity may have an elongate extension. The cavity may have a longitudinal central axis. A longitudinal direction may be the direction extending between the open and closed ends along the longitudinal central axis. The longitudinal central axis of the cavity may be parallel to the longitudinal axis of the aerosol-generating device.

The cavity may be configured as a heating chamber. The cavity may have a cylindrical shape. The cavity may have a hollow cylindrical shape. The cavity may have a shape corresponding to the shape of the aerosol-generating article to be received in the cavity. The cavity may have a circular cross-section. The cavity may have an elliptical or rectangular crosssection. The cavity may have an inner diameter corresponding to the outer diameter of the aerosol-generating article.

An airflow channel may run through the cavity. Ambient air may be drawn into the aerosol-generating device, into the cavity and towards the user through the airflow channel. Downstream of the cavity, a mouthpiece may be arranged or a user may directly draw on the aerosol-generating article. The airflow channel may extend through the mouthpiece.

In any of the aspects of the disclosure, the heating element may comprise an electrically resistive material. Suitable electrically resistive 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 platinum, gold and silver. Examples of suitable metal alloys include stainless steel, nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, gold- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetai® and iron-manganese-aluminium based alloys. In composite materials, the electrically resistive material may optionally be embedded in, encapsulated or coated with an insulating material or vice-versa, depending on the kinetics of energy transfer and the external physicochemical properties required. As described, in any of the aspects of the disclosure, the heating element may be part of an aerosol-generating device. The aerosol-generating device may comprise an internal heating element or an external heating element, or both internal and external heating elements, where "internal" and "external" refer to the aerosol-forming substrate. An internal heating element may take any suitable form. For example, an internal heating element may take the form of a heating blade. Alternatively, the internal heater may take the form of a casing or substrate having different electro-conductive portions, or an electrically resistive metallic tube. Alternatively, the internal heating element may be one or more heating needles or rods that run through the center of the aerosol-forming substrate. Other alternatives include a heating wire or filament, for example a Ni-Cr (Nickel-Chromium), platinum, tungsten or alloy wire or a heating plate. Optionally, the internal heating element may be deposited in or on a rigid carrier material. In one such embodiment, the electrically resistive heating element may be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track on a suitable insulating material, such as ceramic material, and then sandwiched in another insulating material, such as a glass. Heaters formed in this manner may be used to both heat and monitor the temperature of the heating elements during operation.

An external heating element may take any suitable form. For example, an external heating element may take the form of one or more flexible heating foils on a dielectric substrate, such as polyimide. The flexible heating foils can be shaped to conform to the perimeter of the substrate receiving cavity. Alternatively, an external heating element may take the form of a metallic grid or grids, a flexible printed circuit board, a molded interconnect device (MID), ceramic heater, flexible carbon fibre heater or may be formed using a coating technique, such as plasma vapour deposition, on a suitable shaped substrate. An external heating element may also be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track between two layers of suitable insulating materials. An external heating element formed in this manner may be used to both heat and monitor the temperature of the external heating element during operation.

As an alternative to an electrically resistive heating element, the heating element may be configured as an induction heating element. The induction heating element may comprise an induction coil and a susceptor. In general, a susceptor is a material that is capable of generating heat, when penetrated by an alternating magnetic field. When located in an alternating magnetic field. If the susceptor is conductive, then typically eddy currents are induced by the alternating magnetic field. If the susceptor is magnetic, then typically another effect that contributes to the heating is commonly referred to hysteresis losses. Hysteresis losses occur mainly due to the movement of the magnetic domain blocks within the susceptor, because the magnetic orientation of these will align with the magnetic induction field, which alternates. Another effect contributing to the hysteresis loss is when the magnetic domains will grow or shrink within the susceptor. Commonly all these changes in the susceptor that happen on a nano-scale or below are referred to as “hysteresis losses”, because they produce heat in the susceptor. Hence, if the susceptor is both magnetic and electrically conductive, both hysteresis losses and the generation of eddy currents will contribute to the heating of the susceptor. If the susceptor is magnetic, but not conductive, then hysteresis losses will be the only means by which the susceptor will heat, when penetrated by an alternating magnetic field. According to the invention, the susceptor may be electrically conductive or magnetic or both electrically conductive and magnetic. An alternating magnetic field generated by one or several induction coils heat the susceptor, which then transfers the heat to the aerosol-forming substrate, such that an aerosol is formed. The heat transfer may be mainly by conduction of heat. Such a transfer of heat is best, if the susceptor is in close thermal contact with the aerosol-forming substrate.

As used herein, the term ‘aerosol-generating article’ refers to an article comprising an aerosol-forming substrate that is capable of releasing volatile compounds that can form an aerosol. For example, an aerosol-generating article may be a smoking article that generates an aerosol that is directly inhalable into a user’s lungs through the user's mouth. An aerosolgenerating article may be disposable.

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 may be released by heating the aerosol-forming substrate. An aerosol-forming substrate may conveniently be part of an aerosol-generating article or smoking article.

The aerosol-forming substrate may be a solid aerosol-forming substrate. The aerosolforming substrate may be a liquid aerosol-forming substrate contained in a replaceable cartridge connectable with the aerosol-generating device or contained in a refillable liquid storage portion of the aerosol-generating device. The aerosol-forming substrate may comprise both solid and liquid components.

The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds which are released from the substrate upon heating. The aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may 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 aerosol-generating substrate preferably comprises homogenised tobacco material, an aerosol-former and water. Providing homogenised tobacco material may improve aerosol generation, the nicotine content and the flavour profile of the aerosol generated during heating of the aerosol-generating article. Specifically, the process of making homogenised tobacco involves grinding tobacco leaf, which more effectively enables the release of nicotine and flavours upon heating.

Below, there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

Example ex1. An aerosol-generating device comprising: a cavity for receiving an aerosol-forming substrate, an airflow channel through the cavity, and a substrate sensor, wherein the substrate sensor is arranged in or adjacent the cavity, and wherein the substrate sensor is configured to detect a depletion degree of the aerosol-forming substrate.

Example ex2. The aerosol-generating device according to example ex1 , wherein the substrate sensor is a pH sensor.

Example ex3. The aerosol-generating device according to the preceding example, wherein the substrate sensor has a measurement range of between 2 pH and 10 pH, preferably of between 3 pH and 9 pH, most preferably of between 5 pH and 8 pH.

Example ex4. The aerosol-generating device according to any of the two preceding examples, wherein the substrate sensor has a measurement accuracy at pH 7 of ± 0.02 pH, preferably wherein the substrate sensor has a measurement accuracy at pH 7 of ± 0.01 pH.

Example ex5. The aerosol-generating device according to any of the three preceding examples, wherein the substrate sensor has a drift at pH 7 of less than 0.05 pH per day.

Example ex6. The aerosol-generating device according to any preceding example, wherein the substrate sensor is arranged in or adjacent an upstream end of the cavity.

Example ex7. The aerosol-generating device according to any preceding example, wherein the substrate sensor is configured to detect a nicotine content of aerosol being drawn through the airflow channel.

Example ex8. The aerosol-generating device according to any preceding example, wherein the substrate sensor is configured to detect a pH value of aerosol being drawn through the airflow channel.

Example ex9. The aerosol-generating device according to any preceding example, wherein the aerosol-generating device further comprises a controller, and wherein the controller is configured to generate a signal, based upon the output of the substrate sensor, if the depletion degree of the aerosol-forming substrate falls under a predetermined threshold.

Example ex10. The aerosol-generating device according to the preceding example, wherein the signal is one or more of a signal of a user interface, a light emitting signal, a sound signal and a vibration signal. Example ex1 1. The aerosol-generating device according to any of the two preceding examples, wherein the controller is configured to end the operation of the aerosolgenerating device after a predetermined time or a predetermined number of puffs of a user, if the depletion degree of the aerosol-forming substrate is under the predetermined threshold.

Example ex12. The aerosol-generating device according to any preceding example, wherein the depletion degree of the aerosol-forming substrate is a nicotine content or a pH value of aerosol being drawn through the airflow channel.

Example ex13. The aerosol-generating device according to any preceding example, wherein the aerosol-generating device further has an activation button, and wherein the substrate sensor is configured to start detecting the depletion degree of the aerosol-forming substrate after a predetermined time after pressing of the activation button or after a predetermined number of puffs of a user after pressing of the activation button.

Example ex14. The aerosol-generating device according to the preceding example, wherein the substrate sensor is configured to detect the depletion degree of the aerosol-forming substrate continuously during the operation of the aerosol-generating device or close to an estimated depletion of the aerosol-forming substrate, wherein the depletion estimation is preferably based upon the predetermined time after pressing of the activation button or upon the predetermined number of puffs of a user after pressing of the activation button.

Example ex15. An aerosol-generating system comprising an aerosol-generating device according to any preceding example and an aerosol-generating article comprising aerosol-forming substrate.

Example ex16. A method for detecting the depletion degree of an aerosolforming substrate of an aerosol-generating article in an aerosol-generating device according to any of examples 1 to 14, the method comprising: detecting, by the substrate sensor, a depletion degree of the aerosol-forming substrate.

Features described in relation to one embodiment may equally be applied to other embodiments of the invention.

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

Figs. 1 A, 1 B and 1 C show an aerosol-generating device having a substrate sensor;

Figs. 2A and 2B show a more detailed view of the interaction between an aerosolgenerating article comprising aerosol-forming substrate and the substrate sensor;

Figs. 3A and 3B show a more detailed view of the substrate sensor; Fig. 4 shows a further embodiment of the aerosol-generating device utilizing liquid aerosol-forming substrate; and

Fig. 5 shows an alternative positioning of the substrate sensor in the embodiment of Figure 4.

Figure 1A shows an aerosol-generating device 10. The aerosol-generating device 10 comprises a cavity 12 for receiving aerosol-forming substrate 14. The aerosol-forming substrate 14 is part of an aerosol-generating article 16 that is partly received in the cavity 12 of the aerosol-generating device 10. A consumer may directly draw upon a proximal end of the aerosol-generating article 16 during use.

Figure 1 B shows a view of the aerosol-generating device 10 without an aerosolgenerating article 16 being received in the cavity 12. The heating element 18 is arranged at least partly surrounding the cavity 12. The heating element 18 may be arranged in a distal part or upstream part of the cavity 12. More specifically, the heating element 18 comprises an induction coil surrounding the distal part of the cavity 12. Additionally, a susceptor is arranged within the aerosol-forming substrate 14 of the aerosol-generating article 16. The induction coil creates an alternating magnetic field which heats the susceptor within the aerosol-forming substrate 14 in the aerosol-generating article 16, when the aerosol-generating article 16 is received in the cavity 12.

Adjacent an upstream end 20 of the cavity 12, a substrate sensor 22 is arranged. The substrate sensor 22 is configured to detect a depletion rate of the aerosol-forming substrate 14, when the aerosol-forming substrate 14 is received in the cavity 12.

The aerosol-generating device 10 further comprises a controller 24 and a power supply in the form of a battery 26.

Figure 1 C shows the aerosol-generating device 10 as shown in Figure 1 B but with an aerosol-generating article 16 received in the cavity 12. As can be seen, the aerosol-forming substrate 14 of the aerosol-generating article 16 is placed near the substrate sensor 22. Hence, the substrate sensor 22 can detect the depletion rate of the aerosol-forming substrate 14. The substrate sensor 22 may be configured to detect the depletion rate of the aerosol-forming substrate 14 during use, between uses or during use and in between uses.

The substrate sensor 22 is configured as a pH sensor or nicotine content sensor.

During use, air is drawn by a user through the aerosol-forming substrate 14 arranged in the cavity 12. Hence, during use, the substrate sensor 22 may be configured to detect the depletion rate of the aerosol-forming substrate 14 by measuring a pH value or nicotine content of the aerosol being drawn through the cavity 12. To this end, the substrate sensor 22 may also be placed at a different position in the cavity 12, for example at a downstream portion of the cavity 12. Preferably, the substrate sensor 22 is placed upstream the aerosol-generating article 16. Preferably, the substrate sensor 22 is placed facing an upstream end of the aerosolgenerating article 16.

In between uses, the heating element 18 is configured to heat the aerosol-forming substrate 14 of the aerosol-generating article 16 to a temperature above the vaporization temperature of the vaporizable material of the aerosol-forming substrate 14. The vaporized vaporizable material of the aerosol-forming substrate 14 will slightly expand and reach the substrate sensor 22. Hence, the substrate sensor 22 can optimally detect the depletion rate of the aerosol-forming substrate 14 in between puffs. Alternatively, the substrate sensor 22 may be configured to detect the depletion rate of the aerosol-forming substrate 14 from a distance. Exemplarily, the substrate sensor 22 may comprise a light source and a detector to detect the depletion rate of the aerosol forming substrate from a distance.

The substrate sensor 22 may be a pH sensor. Silica fiber-based electrodes may be utilized having high accuracy and small dimensions.

The measurement range of the substrate sensor 22 may be between about 2 pH and 10 pH, preferably of between about 3 pH and 9 pH, most preferably between 5 pH and 8 pH. The accuracy of the substrate sensor 22 may be with a resolution at pH = 7: ± 0.02 pH. Generally the accuracy may be at pH = 7: ± 0.1 pH. The substrate sensor 22 may utilize automatic sensor calibration performed by the controller. The substrate sensor 22 may have a drift at pH = 7: < 0.05 pH per day (sampling interval of 1 min.). The substrate sensor 22 may have a measurement temperatures range from + 5 to + 50 °C. The substrate sensor 22 may have a response time (t90) at 25 °C, standard ISO room temperature range shall be < 30 sec, preferably < 20 sec, most preferably < 10 sec.

The sensor should monitor the pH value and, depending on the value, send a signal so that different light signal is turned on i.e., for example, green light or red light when the experience is about to end.

Figure 2 shows a more detailed view of the aerosol-generating article 16 comprising the aerosol-forming substrate 14 in the airflow during use in Figure 2A and in between uses in Figure 2B. As can be seen in Figure 2A, during use, air is drawn into the aerosol-generating article 16 at the upstream end 20 of the aerosol-generating article 16. The air travels in a downstream direction 28 through the aerosol generating article and vaporized vaporizable material of the aerosol-forming substrate 14 is entrained in the airstream. Downstream, the vaporized vaporizable material of the aerosol-forming material forms small droplets so that an aerosol is in the end delivered to a consumer. Due to the adjacent arrangement of the substrate sensor 22 at the upstream end 20 of the aerosol-generating article 16, the air flowing past the substrate sensor 22 can be checked by the substrate sensor 22 for a pH value or nicotine content. The substrate sensor 22 may therefore detect the depletion rate of the aerosol-forming substrate 14. In the Figure 2B depiction, the situation is shown in between uses. In this case, no air flows through the aerosol-generating article 16. However, due to the heating element 18 still heating the aerosol-forming substrate 14 to a temperature above the vaporization temperature of the vaporizable material of the aerosol-forming substrate 14, vaporized vaporizable material of the aerosol-forming substrate 14 is created. This vaporized vaporizable material of the aerosol-forming substrate 14 may reach the substrate sensor 22. Additionally or alternatively, the substrate sensor 22 may, from a distance, be able to detect the depletion rate of the vaporized vaporizable material of the aerosol-forming substrate 14.

Figure 2 further shows more details about the aerosol-generating article 16. Downstream of the aerosol-forming substrate 14, a hollow tubular section 30 of the aerosolgenerating article 16 is provided. Downstream of the hollow tubular section 30, a filter element 32 is arranged. The filter element 32 is configured to cool the airflow for aerosol generation. Downstream of the filter element 32 and forming the most downstream section of the aerosolgenerating article 16, a downstream filter plug 34 is arranged.

Figure 3 shows a more detailed view of the configuration of the substrate sensor 22. The substrate sensor 22 comprises a multitude of laterally arranged and ring-shaped air channels 36. All of these air channels 36 lead to a central portion of the substrate sensor 22 where the actual detection takes place. The air subsequently flows downstream into the cavity 12. The central portion of the substrate sensor 22 may be part of an aperture 38 leading into the cavity 12 or may form the aperture 38 leading into the cavity 12. The substrate sensor 22 is arranged centrally at the longitudinal axis of the aerosol-generating device 10. The longitudinal axis of the aerosol-generating device 10 at the same time is the longitudinal axis of the cavity 12.

Figure 4 shows an alternative aerosol-generating device. Elements similar to elements from the previously described embodiment will be denoted with the same reference signs and not described again.

The aerosol-generating device 10 of the Figure 4 embodiment is configured for utilizing a liquid aerosol-forming substrate 14. The liquid aerosol-forming substrate 14 is provided in a cartridge 40. The cartridge 40 may be configured replaceable or refillable. In case of a refillable cartridge 40, the cartridge 40 may be part of the aerosol-generating device 10 and denoted as liquid storage portion. The cartridge 40 or the liquid storage portion may be received in the cavity 12. A mouthpiece 42 is arranged downstream of the cartridge 40. The mouthpiece 42 comprises an air outlet 44 at a downstream end through which the inhalable aerosol can exit the mouthpiece 42. An airflow channel 46 fluidly connects an air inlet 48 with an aerosolization zone 50.

The heating element 18 is arranged abutting the aerosolization zone 50. The heating element 18 is arranged fluidly connected with the aerosolization zone 50. The heating element 18 may be configured as a resistive heating element 18, preferably a mesh heater, or as an induction heating element 18. The heating element 18 is electrically connected with the controller 24 via heating connections 52.

Downstream of the aerosolization zone 50, the mouthpiece 42 is arranged. The airflow channel 46 fluidly connects the aerosolization zone 50 with the mouthpiece 42. The substrate sensor 22 is arranged adjacent, preferable abutting, the aerosolization zone 50. The substrate sensor 22 is arranged fluidly connected with the aerosolization zone 50. The substrate sensor 22 may be part of the cartridge 40 or separate from the cartridge 50 as part of the aerosolgenerating device 10. The substrate sensor 22 is electrically connected with the controller 24 via sensor connections 54.

Alternatively, as shown in Figure 5, the substrate sensor 22 may be arranged downstream of the aerosolization zone 50. In other words, the substrate sensor 22 may be arranged downstream of the cartridge 40. In this case, the substrate sensor 22 is arranged fluidly connected with the airflow channel 46 downstream of one or both of the aerosolization zone 50 and the cartridge 40.