Membrane for vibrating grid module

Abstract

The present invention relates to a membrane for a vibrating grid module for use in an aerosol-generating device, the membrane comprising a plurality of recesses defining a portion of the membrane having a reduced thickness, where the portion of the membrane having a reduced thickness is provided with one or more through-holes to define perforations of the membrane. The present invention relates to a method of manufacturing a film for a vibrating mesh module for use in an aerosol-generating device, the method comprising: providing a bulk wafer of a first material, the bulk wafer having opposing first and second surfaces, depositing a cover layer of a second material onto the first surface of the bulk wafer, a via is provided to the capping layer using MEMS manufacturing techniques, a second surface of the bulk wafer is etched to define a recess therein, the second surface of the bulk wafer is etched until bulk wafer material is removed from the recess, and the film is cut off.

Description

Technical Field

[0001] The present invention relates to a membrane for a vibrating grid module for use in an aerosol generating device. The present invention also relates to an aerosol generating device comprising such a vibrating grid module. The present invention also relates to a method of manufacturing a membrane for a vibrating grid module for use in an aerosol generating device. Background Art

[0002] Aerosol generating devices using a vibrating mesh module are also commonly referred to as vibrating mesh (VM) nebulizers.Such vibrating mesh nebulizers are used to generate a respirable aerosol that can be used, for example, to treat respiratory diseases.

[0003] Vibrating mesh nebulizers use mesh deformation or vibration to propel liquid through the mesh. In a typical vibrating mesh nebulizer, a piezoelectric element in contact with the mesh is used to generate vibrations of the mesh. The mesh is adjacent to and in direct contact with a matrix containing a liquid drug. The holes in the mesh can have a cone-shaped structure, where the largest cross-section of the cone is in contact with the liquid matrix. The mesh deformation generates a pressure field in the liquid, thereby pumping and loading the holes with liquid. The liquid volume expelled through the holes breaks up into droplets and is ejected into the mouthpiece chamber. The droplets mix with air and form an aerosol directly in the mouthpiece chamber. During inhalation, ambient air passes through the mouthpiece chamber to deliver the aerosol to the user.

[0004] There are currently several off-the-shelf vibrating mesh atomizer devices available. These devices include a vibrating mesh module, which may consist essentially of two parts: an annular piezoelectric element and a circular perforated membrane. In the case where the membrane is formed of metal or stainless steel, the perforations are typically produced by laser drilling. Laser drilling produces conical holes with a small cone angle and a relatively high aspect ratio. Membranes made of nickel or nickel alloys are typically perforated by a combined photolithography and electroplating process. In a first step, such a membrane is perforated using a photolithography process to obtain the desired pattern of holes with a relatively large diameter. The entire membrane then undergoes electroplating to deposit material on the surface, thereby reducing the size of the holes. The shape of the resulting holes is funnel-shaped, which is generally preferred in terms of their microfluidic properties. In addition, the process may produce a lower aspect ratio and is therefore also superior to conical laser drilling for this reason.

[0005] The size of the pores of the membranes used in these commercially available devices is limited to about 3 to 4 microns. Therefore, the MMAD (median mass aerodynamic diameter) of the aerosol size distribution obtainable by such devices is also in the range of 3 to 4 microns, which is too large for deeper lung inhalation. Therefore, most of the aerosol will be deposited in the upper regions of the respiratory tract, which may not be conducive to effective drug uptake and may cause throat irritation.

[0006] Reducing the size of the holes in conventional membranes may be impossible because the reduced hole diameter requires increased pressure to push the liquid through the hole. This increase can be compensated by reducing the aspect ratio of the hole (the length of the hole divided by the diameter of the hole). However, due to mechanical stability reasons, the thickness of the film cannot be arbitrarily reduced in conventional manufacturing methods. In addition, the liquid throughput rate of each hole decreases quadratically with the reduction of the hole diameter. Therefore, in order to maintain the desired aerosol flux, such a film will have to be provided with a significantly larger number of holes.

[0007] Finally, standard manufacturing techniques for VM modules may require several tedious assembly steps, including gluing the piezoelectric actuator to the perforated membrane. If the gluing is not done correctly, the VM module will have low energy conversion efficiency and may even cause damage during operation. The glue may also be incompatible with some of the liquids used with the VM module, with the risk of liquid contamination, and additional protective means will be required. Summary of the invention

[0008] It would be desirable to provide a perforated membrane for a vibrating mesh module that overcomes at least one of the above-mentioned disadvantages.

[0009] It would be desirable to provide a perforated membrane that allows the generation of aerosol particles having a reduced diameter while maintaining the volume of the generated aerosol.

[0010] It is also desirable to provide a manufacturing method that allows for reliable and repeatable manufacturing of perforated membranes with specific aerosol generating properties. In particular, it is desirable to provide a method of manufacturing a vibrating mesh module without the need for glue or gluing steps.

[0011] In summary, there is a need in the art to make membranes for VM modules that have reduced exit hole diameters, reduced through-hole aspect ratios, increased hole counts, and avoid the use of glue to assemble the module.

[0012] According to an embodiment of the present invention, there is provided a membrane for a vibrating mesh module for use in an aerosol generating device. The membrane comprises a plurality of recesses defining a portion of the membrane having a reduced thickness h. The portion of the membrane having a reduced thickness h is provided with one or more through holes to define the perforation of the membrane.

[0013] By providing a membrane comprising a recessed portion, a portion of the membrane having a reduced thickness is defined. The overall structural stability of such a membrane is maintained by the non-recessed portion of the membrane. At the same time, the recessed portion having a reduced thickness allows for through holes to be defined therein having a diameter small enough to generate aerosol droplets for deep lung inhalation.

[0014] The via formed in the concave portion may have a diameter between 0.1 and 4 micrometers. The via formed in the concave portion may have a diameter between 0.2 and 3 micrometers.

[0015] The diameter of the through hole on the film is a key parameter for limiting the size of the resulting aerosol droplets. The smaller this diameter is, the smaller the droplets formed during aerosolization are. The through hole diameter of the conventional film manufactured with currently available technology is limited to about 3 to 4 microns. Correspondingly, the median mass aerodynamic diameter (MMAD) of the aerosol particle size distribution is in the range of 3 to 4 microns. In contrast, the film described herein has a through hole with a smaller diameter, and therefore allows a smaller MMAD of aerosol particle size distribution.

[0016] The through hole in the membrane may have an aspect ratio of less than 3. The through hole may have an aspect ratio of less than 1. The aspect ratio of a through hole may be defined as the length of the through hole divided by its diameter. Thus, for a through hole disposed in a recess of the membrane, the aspect ratio is given by the reduced thickness of the membrane at the recess divided by the diameter of the through hole. A small aspect ratio may be beneficial. The smaller the aspect ratio, the smaller the pressure required to push a liquid through the through hole.

[0017] The through hole can have any hole geometry. The through hole can have a circular cross section. A circular cross section provides the highest ratio of open cross-sectional area to bounding surface area, which is beneficial for reducing the resistance to microfluid flow through the hole. However, the through hole can be formed to have any other desired cross-sectional shape. For simplicity, with respect to the lateral dimension of the through hole, it is generally referred to herein as the diameter of the through hole. In the case of a through hole having a non-circular cross section, the term diameter should be interpreted as referring to the maximum lateral dimension of the through hole.

[0018] The thickness of the non-recessed portion of the membrane can be significantly greater than the remaining thickness of the membrane at the recess. The membrane can have a thickness of 5 microns to 500 microns. The membrane can have a thickness of 10 microns to 400 microns. The membrane can have a thickness of 30 microns to 200 microns. The thickness of the membrane significantly determines the mechanical behavior of the membrane. Therefore, the thickness of the membrane can be selected depending on the target operating frequency and properties of the membrane material.

[0019] As explained above, the film is provided with a recessed portion which defines a portion of the film having a reduced thickness. The recessed portion itself can have any desired cross-sectional shape. The recessed portion can have a circular cross-sectional shape. The diameter of the recessed portion can be in the range of 5 microns to 300 microns. The diameter of the recessed portion can be in the range of 10 microns to 200 microns. The diameter of the recessed portion can be in the range of 15 microns to 100 microns.

[0020] With the above-described geometric dimensions, recesses covering a wide range of aspect ratios can be formed. However, it is preferred that the recess is formed such that its aspect ratio is less than 3. The aspect ratio of the recess is the same as described above for the aspect ratio of the through hole. The smaller the aspect ratio of the recess, the smaller the pressure required to push the liquid through the recess.

[0021] Each recess is provided with one or more through holes. The number of through holes may depend on the size of the recess and the size of the through holes. The recess may include 1 to 1500 through holes. The recess may include 10 to 1000 through holes.

[0022] The entire membrane may comprise a through-hole density of 10 to 10,000 through-holes / mm2. The entire membrane may comprise a through-hole density of 50 to 5,000 through-holes / mm2.

[0023] The details of the final configuration of the membrane may be selected depending on the liquid matrix to be aerosolized.The details of the final configuration of the membrane may be selected depending on the desired liquid flux.

[0024] The liquid flux of each through hole depends largely on the diameter and open surface area of ​​each through hole. Therefore, the liquid flux of the through hole decreases quadratically as the hole diameter decreases. Therefore, in order to maintain the desired flux of a membrane with smaller through holes, the number of through holes in the membrane must be increased accordingly. In addition, it is necessary to reduce the aspect ratio of the through holes so that the pressure that pushes the liquid through the through holes is kept at a sufficiently low level. Therefore, these factors may have to be considered for the final configuration of the membrane. The final configuration may also need to be adapted to the properties of the liquid to be aerosolized. The configuration may depend in particular on the viscosity of the liquid to be aerosolized.

[0025] The membrane can be manufactured by utilizing micro-electromechanical systems (MEMS) manufacturing techniques. Such manufacturing techniques include process techniques used in semiconductor device manufacturing. These techniques include deposition of material layers, patterning by photolithography, and etching of materials to produce the desired shape.

[0026] Thus, the membrane may be made of a material suitable for processing by MEMS manufacturing techniques. The membrane may include a bulk layer formed of a material provided in wafer form. The wafer material may be made of silicon, silicon oxide, silicon nitride, aluminum nitride or a combination thereof.

[0027] The membrane structure may include multiple additional layers of material. These layers may be applied to the bulk wafer by thin film deposition techniques.

[0028] MEMS technology allows customization of hole geometry and shape to meet the needs required for the application. As mentioned above, this particularly includes the diameter of the through hole, which is a key parameter for regulating the size of the resulting aerosol droplets. MEMS technology also allows the aspect ratio of the through hole to be defined, which is an important parameter for achieving and controlling the flow of microfluids through the through hole. As will be discussed in more detail below, the MEMS manufacturing process can include multiple photolithographic masking and etching steps. The lateral dimensions of the mask define the lateral placement and size of the recesses and through holes in the membrane structure, and can be easily adapted to specific needs. The combination of etchant, wafer material, and wafer lattice orientation allows the cross-sectional shape of the etched recess and the depth of the resulting recess to be defined. Therefore, subsequent etching steps allow the complex shapes of the recesses and through holes of the membrane structure to be manufactured.

[0029] Etching can be done by wet etching or dry etching or a combination thereof. Dry etching (e.g. reactive ion etching or plasma etching) is preferred because it results in vertical edges that are independent of the lattice orientation. In contrast, most wet etching techniques are anisotropic and the resulting pattern is defined not only by the mask but also by the lattice orientation, e.g. <100> Etching the oriented silicon through the film thickness using KOH produces pyramidal shapes with angles defined by the orientation of the lattice planes.

[0030] The present invention also relates to an aerosol generating device having a vibrating grid module comprising a membrane as described herein. As used herein, the term "aerosol generating device" refers to a device that interacts with an aerosol-forming substrate to generate an aerosol. The aerosol generating device may interact with one or both of an aerosol generating article comprising an aerosol-forming substrate and a cartridge comprising an aerosol-forming substrate. The aerosol generating device may include a housing, a circuit system including a controller, a power supply, and a plurality of sensors.

[0031] As used herein, the term "aerosol generating system" refers to the combination of an aerosol generating device and an aerosol-forming substrate. When the aerosol-forming substrate is disposed in a cartridge, the aerosol generating system refers to the combination of the aerosol generating device and the cartridge. In an aerosol generating system, the aerosol-forming substrate and the aerosol generating device cooperate to generate an aerosol.

[0032] The present invention also relates to a method of manufacturing a membrane for a vibrating mesh module for use in an aerosol generating device. The method comprises:

[0033] providing a bulk wafer of a first material, the bulk wafer having opposing first and second surfaces,

[0034] depositing a blanket layer of a second material onto the first surface of the bulk wafer,

[0035] The cover layer is provided with through holes using MEMS manufacturing techniques,

[0036] etching the second surface of the bulk wafer to define a recess therein,

[0037] etching the second surface of the bulk wafer until bulk wafer material is removed from the recess,

[0038] The membrane was cut.

[0039] The method of manufacturing the membrane may include a number of manufacturing steps that are also used in MEMS manufacturing and may include processes such as deposition of material layers, patterning by photolithography, and etching of the material in order to produce the desired shape.

[0040] Thin film deposition can be achieved by physical vapor deposition (PVD), including techniques such as evaporation, magnetron sputtering, or pulsed laser deposition (PLD). These techniques can be used to deposit one or more material layers onto a bulk wafer in a desired sequence.

[0041] Photolithography is a well-known technique in which light is used to create tiny patterned thin films of a suitable material on a bulk substrate to protect selected areas of the substrate during subsequent etching, deposition or implantation operations. Typically, ultraviolet light is used to transfer the geometric design from an optical mask to a light-sensitive chemical (photoresist) coated on the substrate. The photoresist decomposes or hardens where it is exposed to light. The patterned film is then created by removing the softer portions of the coating with an appropriate solvent.

[0042] The etching step may be accomplished by wet etching or dry etching, or a combination thereof. Dry etching, such as reactive ion etching or plasma etching, may be preferred because it can be used to produce vertical edges in the substrate regardless of the substrate's crystallographic orientation. Wet etching techniques may also be used. However, these techniques are generally anisotropic and the resulting pattern is not only defined by the previously applied mask, but may also depend on the lattice orientation. For example, <100> Etching the oriented silicon through the film thickness using KOH produces pyramidal shapes with angles defined by the orientation of the lattice planes.

[0043] The bulk wafer can be made of any first material suitable for processing by MEMS manufacturing technology. The bulk wafer material can be made of silicon, silicon oxide, silicon nitride, aluminum nitride or a combination thereof. The material of the one or more additional layers applied to the bulk wafer can also be selected from any material suitable for processing by MEMS manufacturing technology. The material of the one or more additional layers applied to the bulk wafer can be selected from silicon, silicon oxide, silicon nitride, aluminum nitride or a combination thereof. In addition, the additional layer can be formed by a material with a specific functional property (e.g., a selective etching stopper or a material that enhances the flow properties of a liquid matrix to be aerosolized).

[0044] In a method of manufacturing a membrane for a vibrating grid module for use in an aerosol generating device, a bulk wafer of a first material such as silicon is provided. Commercially available wafer materials have different sizes. The final membrane structure can have a thickness of 5 microns to 500 microns. The membrane can have a thickness of 10 microns to 400 microns. The membrane can have a thickness of 30 microns to 200 microns. The thickness of the membrane structure significantly determines the mechanical behavior of the membrane. Therefore, the membrane thickness can be selected based on the target operating frequency and the material properties of the membrane. As discussed in more detail below, the final thickness of the membrane structure can be adjusted by a selective etching step during the manufacturing method.

[0045] Depositing the capping layer onto the first surface of the bulk wafer may be performed by any of the above-mentioned physical vapor deposition (PVD) techniques.The capping layer may be formed of silicon dioxide or silicon nitride.

[0046] The cover layer may have a thickness of 0.1 to 5 microns. The cover layer may have a thickness of 0.2 to 3 microns. The cover layer may have a thickness of 0.3 to 1 micron. The thickness of the cover layer and the size of the through-holes defined therein are decisive parameters for controlling the resulting MMAD (median mass aerodynamic diameter). Due to considerations of microfluidic properties, a small aspect ratio is required. Therefore, a cover layer with a small thickness may be preferred. The final choice of thickness may represent a trade-off with mechanical stability, which may form a lower limit to the thickness of the cover layer. The lower limit may also depend on the lateral extension of the cover layer and the expected force applied to the cover layer during use.

[0047] The cover layer is then provided with through holes using further MEMS manufacturing techniques. The through holes through the cover layer may be obtained by a combination of photolithography and etching. For this purpose, the cover layer may be provided with a mask defining the size and position of the through holes on the cover layer. In a subsequent etching step, unmasked areas of the cover layer may be etched away, so that the cover layer is provided with a plurality of through holes.

[0048] The via formed in the concave portion may have a diameter between 0.1 and 4 micrometers. The via formed in the concave portion may have a diameter between 0.2 and 3 micrometers.

[0049] In a further method step, the second surface of the bulk wafer is processed to define recesses therein. These recesses can again be obtained by masking and subsequent etching of the bulk wafer material. The etching of the silicon bulk wafer can be performed by using sulfur hexafluoride (SF6). The etching of the second surface of the bulk wafer is continued until the bulk wafer material is removed from the recesses. The recesses in the second surface are preferably positioned so that they coincide with the positions of the through holes provided in the cover layer. The combination of the bulk wafer and the cover layer forms a membrane structure with recesses of reduced thickness.

[0050] By etching the second surface of the bulk wafer, the final thickness of the membrane structure can be defined. The thickness of the membrane determines to a large extent the vibration characteristics of the membrane structure.

[0051] The two sides of the membrane may also be referred to as the "inlet side" and the "release side" of the membrane. In this respect, the side of the membrane comprising the recess is the "inlet side", which in use faces the liquid storage portion and through which liquid enters the through-holes. The other side of the membrane forms the "release side" of the membrane, which is the side through which droplets are released into the downstream mouthpiece chamber. Therefore, the cover layer comprising through-holes is provided on the release side of the membrane structure.

[0052] In the final step, the membrane is cut from the bulk wafer material. The membrane is cut into the desired size required in the application. Typically, the size of the bulk wafer is significantly larger than the desired size of the membrane, so that in the manufacturing method, multiple membrane structures can be manufactured in parallel on a single bulk wafer. This parallel processing allows for convenient mass production of membranes.

[0053] One or more additional material layers may be applied when manufacturing the membrane. For example, an additional layer may be deposited between the bulk wafer and the cover layer. The additional cover layer may be configured as a selective etch stopper layer. Such a selective etch stopper layer may protect the cover layer on the first surface of the bulk wafer when a recess is formed at the second surface of the bulk wafer. The selective etch stopper layer may ensure that the etching process for forming the recess at the second surface of the bulk wafer is terminated when the etching fluid has removed the bulk wafer material from the recess and has reached the selective etch stopper layer. Typically, this is achieved by forming the selective stopper layer from a material that does not dissolve when in contact with the etchant used to etch the bulk wafer material. The selective etch stopper layer may then be removed by using a different etching solvent.

[0054] The thickness of the selective stopper layer can be appropriately selected. The thickness of the selective stopper layer can be in the range of a few nanometers to 20 micrometers.

[0055] In the above example where sulfur hexafluoride is used to etch a silicon bulk wafer, the selective etch stopper layer can be formed of any material that does not dissolve when in contact with sulfur hexafluoride. In this regard, a suitable material is silicon dioxide. Silicon dioxide does not dissolve when in contact with sulfur hexafluoride, so that the vertical etching process of the bulk wafer will stop when the etching fluid reaches the silicon dioxide layer. The silicon dioxide layer can be removed later by another etchant, such as hydrogen fluoride (HF) or trifluoromethane (CHF3).

[0056] The technique of using a selective etch stopper layer can generally be used to provide a layer with a predetermined thickness for a membrane structure. In this way, the material defining the thickness of the membrane itself can also be deposited as a material layer sandwiched between two selective etch stopper material layers. In this way, a particularly thin membrane can be provided. In this way, a membrane with a well-defined thickness can also be provided. As discussed above with respect to a membrane etched from a bulk wafer material, the thickness of such a membrane can be the same. The thickness of such a membrane can be in the range of 30 microns to 150 microns.

[0057] Fabricating the membrane using MEMS technology allows the membrane structure to be configured to have desired surface properties that may be beneficial to the aerosolization process. In particular, the material properties of the surface forming the through holes and the surface that may contact the liquid matrix to be aerosolized can be designed to have such desired surface properties.

[0058] For example, a polysilicon layer can be disposed below the cover layer and directly adjacent to the cover layer. In this way, the entrance side of the through hole of the cover layer is lined with a polysilicon layer. Since polysilicon is more hydrophilic than single crystal silicon or silicon nitride, the microfluidic flow through the through hole is enhanced.

[0059] The various method steps discussed above may also be performed in different sequences. A person skilled in the art may change the order of the various manufacturing steps as deemed appropriate.

[0060] The present disclosure also relates to a membrane for a vibrating grid module for use in an aerosol generating device, wherein the membrane comprises a bulk wafer material processed by MEMS manufacturing, and wherein the membrane comprises a plurality of through holes. The material of the membrane is patterned to have a conductive structure. Such a conductive track can act as an intrinsic resistive heater if current is flowing through it.

[0061] MEMS manufacturing allows for the integration of specific functional features of the membrane that are difficult to achieve with conventional membrane manufacturing techniques or are usually only provided as additional features to the vibrating grid module. According to the present disclosure, such functional features can be integrated into the bulk wafer material during the manufacturing process. For example, a bulk wafer material that can be used as a basis for membrane fabrication can be provided with a pattern of conductive structures at the beginning of the manufacturing process. Other details of the membrane, such as the application of additional layers or the etching of recessed portions, can then be provided in subsequent processing steps.

[0062] The conductive structure may be a track made of a conductive material. The conductive structure may be a metal track. Such a track may be designed so that it extends through a portion of the membrane material that is adjacent to the through hole but is not exposed to the liquid matrix flowing through the membrane. In this way, the conductive structure may be protected from direct contact with the liquid material to be aerosolized. This may help prevent degradation of the conductive structure. This may also help prevent any undesirable effects on the liquid matrix caused by the material contacting the conductive structure.

[0063] In order to enable current to flow through the conductive structure, the end portion of the conductive structure may reach the outer surface of the membrane structure at a position where there is no liquid flow and there is no risk of the contact portion coming into contact with the liquid matrix to be aerosolized. Such a position may be close to the circumference of the membrane structure. In particular, the membrane may include contact pads at its outer circumference to establish electrical contact with the conductive structure.

[0064] When the aerosol generating device is in use, an electric current may flow through the conductive structure, causing the conductive structure to act as an inherent heater element. This inherent heater element may allow the operating temperature of the membrane to be adjusted.

[0065] Intrinsic heater elements can also be used to ensure that the temperature of the liquid matrix flowing through the through hole has a well-defined temperature. In particular, the heater element can ensure that the temperature of the liquid matrix is ​​quite independent of external conditions such as ambient temperature. The volume of liquid flowing through the through hole in each cycle is quite small, and can be equivalent to only a few microliters per second. In addition, the target temperature increase can also be relatively small, and can be equivalent to only tens of Kelvin higher than the ambient temperature. Therefore, the required heating power required to obtain the temperature increase of the liquid matrix is ​​quite low. Therefore, the liquid will be heated almost instantaneously when it reaches the membrane and when it flows through the through hole. By heating the circumference of the through hole of the membrane in a targeted manner, this favorable effect is obtained while avoiding the need to heat the entire body liquid in the reservoir.

[0066] The temperature increase of the liquid matrix near the through hole or inside the through hole can also cause the local reduction of the viscosity of the liquid matrix. Therefore, using the heated film, the liquid matrix that can have too high viscosity at room temperature or at a lower ambient temperature can also be used together with an aerosol generating device including such a membrane module with an inherent heater element. This modification generally increases the design space of the liquid that can be used with such a device. The liquid matrix with increased viscosity can have the beneficial effect of reducing matrix leakage.

[0067] The temperature of the heater element may be maintained below the boiling point of the liquid matrix to be aerosolized. The main reason for this is that the primary cause of aerosolization should be the physical interaction of the liquid matrix with the vibrating grid module. Instead, in such systems, aerosolization caused by heating and evaporation of the liquid matrix and subsequent recondensation should be avoided.

[0068] Since typical liquid matrices to be aerosolized by a vibrating grid device contain a large amount of water, the target temperature of the heater element should not exceed 100 degrees Celsius. The difference between the target temperature of the heater element and the ambient temperature should not be higher than 80 degrees Celsius. The difference between the target temperature of the heater element and the ambient temperature should not be higher than 60 degrees Celsius. The difference between the target temperature of the heater element and the ambient temperature should not be higher than 40 degrees Celsius.

[0069] The main advantage of a vibrating mesh module for an aerosol generating device comprising an intrinsic heater element can be seen as relating to the stabilization of the operating point relative to the ambient temperature. By using an intrinsic heater, more uniform aerosolization conditions can be achieved, which can allow for a more consistent user experience.

[0070] In addition, a vibrating grid module for an aerosol generating device comprising an inherent heater element may increase the design latitude of such a device. Liquid substrates with higher viscosities may be used. The use of liquid substrates may have beneficial effects in terms of handling the substrate and may in particular prevent leakage of the substrate from the supply device.

[0071] The present disclosure also relates to a membrane for a vibrating mesh module for use in an aerosol generating device, wherein the membrane comprises a bulk wafer material processed by MEMS manufacturing, and wherein the membrane comprises a plurality of through holes. The vibrating mesh module may include an integrated piezoelectric element. The piezoelectric element may be glued to the membrane during the manufacturing process. The piezoelectric element glued to the membrane is considered an embodiment of "integrally formed with the membrane".

[0072] MEMS manufacturing can offer the possibility to include piezoelectric elements during the manufacturing process of the vibrating mesh module. The piezoelectric elements can be deposited on the membrane module. By already including the piezoelectric elements during the manufacturing of the membrane module, the attachment of the piezoelectric elements to the membrane module is facilitated. In conventional manufacturing methods, the piezoelectric elements have to be glued to the membrane module, which can often be a tedious and error-prone manufacturing step.

[0073] Furthermore, growing the piezoelectric element directly onto the membrane module allows for a more target-specific geometric design of the piezoelectric element. The piezoelectric material can be deposited at certain predetermined locations of the membrane module. The deposition of the piezoelectric material can be obtained by MEMS technology, for example by sputtering or coating techniques. Masks can be used to achieve the desired lateral geometry of the piezoelectric patch. Alternatively, the desired lateral geometry can also be achieved by providing a full layer of piezoelectric material and subsequently removing the piezoelectric material from the undesired locations. This removal can again be achieved by masking and etching or by mechanical removal.

[0074] One or more piezoelectric elements may be deposited on the contact surface of the membrane structure. The contact surface of the membrane structure may be an annular portion located at the peripheral region of the membrane structure. If considered helpful, the contact portion may also be defined at other surface regions of the membrane structure.

[0075] In principle, any material suitable for producing a piezoelectric element may be used. Such suitable piezoelectric materials may include lead zirconate titanate, zinc oxide, barium titanate, aluminum nitride, scandium aluminum nitride, lithium niobate, ferroelectric ceramics with a perovskite structure, and combinations thereof.

[0076] A membrane structure as described above that is also provided with one or more integrated piezoelectric elements may also be referred to as a vibrating grid module. Such a vibrating grid module may be used to manufacture a vibrating grid aerosol generating device. Such a vibrating grid module may be manufactured and sold as an interchangeable accessory for such a device. Therefore, the present disclosure also relates to a vibrating grid module for an aerosol generating device and a corresponding manufacturing method thereof.

[0077] The present disclosure also relates to a membrane for a vibrating mesh module for use in an aerosol generating device, wherein electronic circuitry is integrally formed in the material of the vibrating mesh module.

[0078] MEMS manufacturing may even offer the possibility of including at least part of the required electronic circuitry directly in the material of the membrane structure of the vibrating grid module. In particular, the electronic circuitry may be integrally formed in the material of the membrane structure. The electronic circuitry included in the membrane structure may include parts of the driver electronics, parts of the microcontroller, and sensor components.

[0079] The vibration grid module may include one or more piezoelectric elements. The vibration grid module may include one or more piezoelectric elements formed integrally with the membrane structure of the vibration grid module. The piezoelectric element may be included in the membrane structure manufacturing of the membrane using MEMS manufacturing technology. The piezoelectric element may also be glued to the membrane during the manufacturing process. The piezoelectric element glued to the membrane is regarded as an embodiment of "formed integrally with the membrane". In addition, the vibration grid module may include a contact pad for each of the piezoelectric elements. These contact pads may be electrically connected to the piezoelectric element and may be integrally formed in the material of the membrane structure. The contact pads may be formed and configured to allow electrical contact with corresponding contact pins of the aerosol generating device. This construction may allow the vibration grid module to be easily replaced even by the user himself. In order to further facilitate such replacement, the aerosol generating device and the vibration grid module may be configured so that the vibration grid module can be slid into the aerosol generating device. When the vibration grid module is slid into the aerosol generating device, the contact pins of the device may contact the contact pads of the module. By using multiple piezoelectric elements, it is possible to excite different vibration modes of the membrane depending on which of the piezoelectric elements is powered at what frequency. This allows to modify the aerosol formation process and ultimately the properties of the resulting aerosol.

[0080] The vibrating grid module may further comprise one or more sensors integrated into the material of the vibrating grid module or into the material of the membrane structure. Such sensors may include, but are not limited to, temperature sensors, stress bending sensors or acceleration sensors. These sensors may be used for device diagnostics during operation of the aerosol generating device. These sensors may also be used to provide feedback to a controller of the aerosol generating device. Since the sensors are disposed directly in the material of the vibrating grid module, they may provide an immediate and direct response from the vibrating grid module.

[0081] The present invention also relates to a method of manufacturing a membrane of a vibrating grid module for use in an aerosol generating device as described above, wherein the method further comprises the method step of patterning the bulk wafer material to have conductive structures.

[0082] The patterning step may be performed before completing the etching of the bulk wafer material. In particular, the patterning step may be performed as a first method step after providing the bulk wafer material. The pattern of the conductive structure may be such that the conductive structure is arranged adjacent to the through-hole of the membrane.

[0083] The conductive structure may be a metal track.The conductive structure may be formed such that the contact portion with the conductive portion is provided at the outer periphery of the membrane structure.

[0084] The present invention also relates to a method for manufacturing a membrane of a vibrating grid module as described above for use in an aerosol generating device, wherein the method further comprises a method step of providing one or more piezoelectric elements, wherein the one or more piezoelectric elements are integrally formed on a contact surface of the membrane structure.

[0085] The piezoelectric element can be glued to the membrane structure. The piezoelectric element can be glued to the contact surface of the membrane structure. The piezoelectric element can be deposited on the contact surface of the membrane structure by sputtering or by coating techniques. The desired lateral geometry of the piezoelectric element can be obtained by using a mask.

[0086] Alternatively, the desired lateral geometry of the piezoelectric element can be obtained by depositing a full layer of piezoelectric material onto the membrane contact surface and subsequently removing the piezoelectric material at locations where it is not needed. Forming the piezoelectric element already during the manufacture of the membrane module can avoid the tedious and error-prone manufacturing step of gluing the piezoelectric element to the membrane structure (as is done in conventional manufacturing methods for vibrating mesh modules).

[0087] The present invention also relates to a method of manufacturing a membrane of a vibrating grid module as described above for use in an aerosol generating device, wherein the method further comprises the method step of integrally forming at least part of the electronic circuitry of the aerosol generating device in the material of the vibrating grid module.

[0088] The electronic circuitry integrally formed in the material of the vibrating mesh module may include contact portions for the piezoelectric elements. The electronic circuitry integrally formed in the material of the vibrating mesh module may include one or more sensor elements selected from a temperature sensor, a stress bending sensor or an acceleration sensor.

[0089] These sensors may be used for device diagnostics during operation of the aerosol generating device. These sensors may also be used to provide feedback to a controller of the aerosol generating device. Since the sensors are disposed directly in the material of the vibrating mesh module, they may provide an immediate and direct response from the vibrating mesh module.

[0090] A non-exhaustive list of non-limiting examples is provided below.Any one or more features of these examples may be combined with any one or more features of another example, embodiment or aspect described herein.

[0091] Example 1: A membrane for a vibrating mesh module for use in an aerosol generating device, the membrane comprising a plurality of recesses defining portions of the membrane having a reduced thickness,

[0092] The portion of the membrane having reduced thickness is provided with one or more through holes to define a perforation of the membrane.

[0093] Example 2: The membrane according to example 1, wherein the through-holes have a diameter between 0.1 and 5 microns, preferably between 0.2 and 3 microns.

[0094] Example 3: The film according to any of the preceding examples, wherein the through-holes have an aspect ratio lower than 3, preferably lower than 1.

[0095] Example 4: The membrane of any of the preceding examples, wherein the through-holes have a circular cross-section.

[0096] Example 5: The film of any of the preceding examples, wherein the film has a thickness of 5 to 500 microns, 10 to 400 microns, 30 to 200 microns.

[0097] Example 6: The membrane according to any of the preceding examples, wherein the recesses defining the portion of the membrane having reduced thickness have a diameter of 5 to 300 microns, preferably 10 to 200 microns, preferably 15 to 100 microns.

[0098] Example 7: The membrane according to any of the preceding examples, wherein the recess comprises 1 to 1500 through holes, preferably 10 to 1000 through holes.

[0099] Example 8: The membrane according to any of the preceding examples, wherein the membrane comprises a through-hole density between 10 and 10,000 through-holes / mm2, preferably between 50 and 5,000 through-holes / mm2.

[0100] Example 9: A film according to any of the preceding examples, wherein the recess has an aspect ratio of less than 3.

[0101] Example 10: The film of any of the preceding examples, wherein the film comprises multiple layers of material.

[0102] Example 11: The film of the preceding example, wherein the film includes a bulk layer formed from a material provided in wafer form.

[0103] Example 12: A membrane according to the preceding example, wherein the wafer material is made of a material suitable for MEMS fabrication.

[0104] Example 13: The membrane of the preceding example, wherein the wafer material is made of silicon, silicon oxide, silicon nitride, aluminum nitride, or a combination thereof.

[0105] Example 14: An aerosol generating device comprising a vibrating grid module for aerosolizing an aerosol-forming substrate,

[0106] Wherein the vibration grid module comprises a membrane according to any one of Examples 1 to 13.

[0107] Example 15: A method of making a membrane for a vibrating mesh module for use in an aerosol generating device, the method comprising:

[0108] providing a bulk wafer of a first material, the bulk wafer having opposing first and second surfaces,

[0109] depositing a blanket layer of a second material onto the first surface of the bulk wafer,

[0110] The cover layer is provided with through holes using MEMS manufacturing techniques,

[0111] etching the second surface of the bulk wafer to define a recess therein,

[0112] etching the second surface of the bulk wafer until bulk wafer material is removed from the recess,

[0113] The membrane was cut.

[0114] Example 16: The method according to Example 15, wherein the through hole is provided to the cover layer by the following steps

[0115] masking the cover layer to define the location and size of the through holes of the membrane to be produced,

[0116] The capping layer is etched to create the through hole in the capping layer.

[0117] Example 17: The method according to Example 15 or 16, further comprising:

[0118] An additional layer is deposited between the bulk wafer and the capping layer, wherein the additional layer is configured as a selective etch stopper layer.

[0119] Example 18: The method according to Example 17, further comprising:

[0120] depositing another selective etch stopper layer between the bulk wafer and the capping layer, and

[0121] A further material layer is deposited between the two selective etch stopper layers, wherein the thickness of the further material layer determines the thickness of the film to be produced.

[0122] Example 19: The method according to any one of Examples 15 to 18, wherein the material of the bulk wafer and / or the another material layer is selected from silicon, silicon oxide, silicon nitride, aluminum nitride, or a combination thereof.

[0123] Example 20: The method according to any one of Examples 15 to 18, further comprising:

[0124] An additional material layer is deposited below the cover layer, wherein the additional layer allows to define and adjust the surface properties of the material defining the through holes of the membrane.

[0125] Example 21: The method of Example 20, wherein the additional layer is a layer that is more hydrophilic than the material of the cover layer.

[0126] Example 22: The method of any of Examples 20 or 21, wherein the additional layer is a polysilicon layer.

[0127] Example 23: A membrane for a vibrating mesh module for use in an aerosol generating device,

[0128] The membrane is made of a material suitable for MEMS manufacturing,

[0129] The membrane includes a plurality of through holes, wherein the material of the membrane is patterned to have a conductive structure.

[0130] Example 24: A film according to Example 23, wherein the conductive structure is configured to extend through a portion of the film material.

[0131] Example 25: The membrane of any of Examples 23 or 24, wherein the conductive structure is disposed adjacent to the through-hole but is not exposed to a liquid flow path defined by the through-hole in the membrane.

[0132] Example 26: The film of any of Examples 23 or 25, wherein the film comprises contact pads at its outer circumference to establish electrical contact with the conductive structure.

[0133] Example 27: A membrane according to any of Examples 23 or 26, wherein in use, an electric current flows through the conductive structure such that the conductive structure acts as a heater element allowing the operating temperature of the membrane to be adjusted.

[0134] Example 28: The membrane of any of Examples 1 to 14 or 23 to 27, further comprising one or more piezoelectric elements deposited on the contact surface of the membrane structure.

[0135] Example 29: The membrane according to the previous example, wherein the contact surface is an annular portion located at the peripheral area of ​​the membrane structure.

[0136] Example 30: A film according to any one of Examples 28 to 29, wherein the material of the piezoelectric element is selected from lead zirconate titanate, zinc oxide, barium titanate, aluminum nitride, scandium aluminum nitride, lithium niobate, or a ferroelectric ceramic having a perovskite structure.

[0137] Example 31: A vibrating mesh module for use in an aerosol generating device, the vibrating mesh module comprising:

[0138] The membrane according to any one of Examples 1 to 14 or 23 to 27, further comprising one or more piezoelectric elements deposited on the contact surface of the membrane structure.

[0139] Example 32: A membrane according to any one of Examples 1 to 14 or 23 to 30, wherein the electronic circuit system is integrally formed in the material of the vibrating grid module.

[0140] Example 33: The membrane of the preceding example, wherein the electronic circuit system includes electronic contact structures for one or more piezoelectric elements of the membrane structure.

[0141] Example 34: The film of any of Examples 32 to 33, wherein the electronic circuit system comprises one or more sensor elements.

[0142] Example 35: The membrane of the preceding example, wherein the one or more sensor elements are selected from a temperature sensor, a stress bending sensor, or an acceleration sensor.

[0143] Example 36: A film according to any one of Examples 34 to 35, wherein the sensor is used for device diagnostics or to provide feedback to a controller of the aerosol generating device during operation.

[0144] Example 37: The method according to any one of Examples 15 to 22, further comprising:

[0145] The bulk wafer material is patterned to have conductive structures.

[0146] Example 38: The method of Example 37, wherein the conductive structure is a metal trace.

[0147] Example 39: The method of any of Examples 37 or 38, wherein the patterning step is performed before etching the bulk wafer material.

[0148] Example 40: The method of any one of Examples 15 to 22, wherein the one or more piezoelectric elements are integrally formed on the contact surface of the membrane structure.

[0149] Example 41: The method according to the previous example, wherein the piezoelectric element is deposited on the contact surface of the membrane structure by sputtering or by a coating technique.

[0150] Example 42: The method according to the preceding example, wherein the desired lateral geometry of the piezoelectric element is obtained by using a mask.

[0151] Example 43: The method of the preceding example, wherein the desired lateral geometry of the piezoelectric element is obtained by depositing a full layer of piezoelectric material onto the membrane contact surface and subsequently removing the piezoelectric material where it is not needed.

[0152] Example 44: The method of any of Examples 15 to 22, wherein the electronic circuit system is integrally formed into the material of the vibration grid module during manufacturing.

[0153] Example 45: The method of the preceding example, wherein the electronic circuit system includes one or more sensor elements selected from a temperature sensor, a stress bending sensor, or an acceleration sensor.

[0154] Example 46: The method of the preceding example, wherein the sensor is used to perform device diagnostics or provide feedback to a controller of the aerosol generating device during operation.

[0155] Features described with respect to one embodiment may be equally applicable to other embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0156] The present invention will be further described, by way of example only, with reference to the accompanying drawings, in which:

[0157] Figure 1 A schematic design of a conventional vibrating mesh atomizer is shown;

[0158] Figure 2 shows the geometries of through-holes in membranes that can be obtained by different manufacturing methods;

[0159] Figure 3 A detailed view of a MEMS membrane is shown;

[0160] Figure 4 The method steps of manufacturing a MEMS membrane are shown;

[0161] Figure 5 Shows Figure 4 Modification of the method;

[0162] Figure 6A MEMS membrane provided with a hydrophilic layer is shown;

[0163] Figure 7 A MEMS membrane provided with an intrinsic heater is shown;

[0164] Figure 8 A MEMS membrane is shown provided with an integrated piezoelectric element; and

[0165] Fig. 9 The VM module is shown connected to an upstream liquid flow chamber. DETAILED DESCRIPTION

[0166] Figure 1 An aerosol generating device 10 is shown, which may also be referred to as a nebulizer. The nebulizer includes a liquid storage portion 12 that holds a supply of a liquid matrix 14 to be aerosolized. A vibrating grid module 20 is provided in direct contact with the liquid matrix 14, the vibrating grid module including an annular piezoelectric element 22 surrounding a circular grid. The grid is constructed as a membrane 24 including through holes 26. The through holes 26 in the membrane 24 have a conical structure, wherein the maximum cross-section of the cone is in contact with the liquid drug. By the vibration of the membrane 26, the liquid matrix 14 is pumped through the through holes 26 and ejected into a mouthpiece chamber 28. During inhalation, ambient air passes through the mouthpiece chamber 28 to deliver the generated aerosol 30 to the user.

[0167] The size of the through-holes 26 at the outlet side of the membrane 24 and the aspect ratio of the through-holes 26 are key parameters in determining the aerosolization process. Figure 2 An enlarged schematic diagram of a membrane 24 including a through hole 26 is shown. The membranes 24 are shown in descending order from left to right according to the aspect ratio AR of their through holes 26. The order is represented by Figure 2 24. The through holes 26 in the membrane 24 are obtained by different manufacturing methods, each of which produces a through hole 26 with a different aspect ratio. In general, the aspect ratio AR of the through hole 26 is defined by its length divided by its diameter.

[0168] Figure 2 The membrane 24 shown in A is a membrane 24 made of stainless steel. The through hole 26 therein is produced by laser drilling. The laser drilling makes the through hole 26 have a conical shape with a small cone angle. The through hole 26 obtained in this way has a relatively large aspect ratio A. R The aspect ratio of these vias is A R It can be approximated by the quotient H / d, where H is the thickness of the membrane 24 and d is the smallest diameter of the through-holes 26 at the outlet end of the membrane 24 .

[0169] Figure 2The membrane 24 shown in B is a membrane 24 made of a nickel-cobalt alloy. The through holes 26 therein are produced by photolithography and subsequent electroplating. In a first step, a pattern of a plurality of through holes 26 with a relatively large diameter is produced in the membrane 26 using photolithography. Subsequently, the entire membrane 24 undergoes electroplating to deposit material on the membrane surface, thereby reducing the diameter of the through holes 26. This gives the through holes 26 a funnel-like shape. These through holes 26 have a slightly smaller aspect ratio AR and will therefore be superior to the through holes 26 drilled by the laser.

[0170] Figure 2 The membrane 24 shown in FIG. 3 is a membrane 24 according to the present disclosure. The membrane 24 includes a recess 34 in which the through hole 26 is disposed. The remaining thickness h of the membrane 24 in the recess 34 is significantly less than the total thickness H of the membrane 24. Therefore, the aspect ratio AR of the through hole 26 of such a membrane 24 can be expressed as the quotient h / d, which is Figure 2 The through-holes 26 of the membrane 24 depicted in A and 2B have a much smaller aspect ratio AR.

[0171] exist Figure 3 , a portion of a membrane 24 according to the present disclosure is shown in more detail. Figure 3 A shows an enlarged view of a recess 34 of such a membrane 24. The membrane 24 is made of silicon and has a total thickness H. The recess 34 has a circular cross section with a diameter D and a depth t. The thickness h of the recessed portion of the membrane 24 is determined as h=Ht. A plurality of through holes 26 are provided at the recess 34. These through holes 26 also have a circular cross section and have a diameter d much smaller than the diameter D of the recess 34.

[0172] like Figure 3 As shown in FIG. 2B , the membrane 24 may include a plurality of recesses 34 , while each recess 34 may include a plurality of through holes 26 through which the liquid matrix 14 is released into the mouthpiece chamber 28 of the aerosol generating device 10 .

[0173] Figure 3 C shows an electron microscope image of a portion of the membrane including the recess 34. The membrane has a thickness of about 100 micrometers. The circular recess 34 has a diameter D of about 50 micrometers. The remaining thickness h of the recess 34 is equal to 1 micrometer. The recess comprises 14 circular through holes 26 evenly distributed in the recess 34 in a hexagonal pattern. The diameter d of the through holes 26 is equal to about 2 micrometers. Therefore, Figure 3 The through-holes of the membrane shown in C have an aspect ratio equal to about 0.5.

[0174] like Figure 3 The membrane 24 shown in FIG. 1 can be manufactured by a series of manufacturing steps involving various MEMS processing techniques. Suitable manufacturing methods are described in Figure 4. In a first step, a bulk wafer 40 made of silicon is provided as a base substrate. On top of a first surface of the bulk wafer 40, two material layers 42, 44 are formed by thin film deposition. Layer 42 is formed of silicon dioxide and serves as a selective etch stopper layer. On top of layer 42, a layer 44 formed of silicon nitride is deposited. Layer 44 serves as a capping layer for membrane 24.

[0175] In a second step, a mask defining the position and diameter of via 26 is applied to capping layer 44 by photolithography. Capping layer 44 is then dry etched with carbon tetrafluoride (CF4) to locally remove material of capping layer 44 and create via 26 in silicon nitride capping layer 44.

[0176] In a third step, a recess is defined in the second surface or back side of the silicon bulk wafer 40. For this purpose, a mask defining the position and cross section of the recess is applied to the second surface of the bulk wafer 40 by photolithography. Subsequently, the recess 34 is formed by etching the second surface of the silicon bulk wafer 40 with sulfur hexafluoride (SF6).

[0177] In a fourth step, the complete second surface of the silicon bulk wafer 40 is further etched until the bulk wafer material is removed from the recess 34. Since a selective etch stopper layer 42 made of silicon dioxide that does not dissolve when in contact with sulfur hexafluoride is used, the etching of the recess 34 is stopped once the silicon dioxide layer 42 is reached. In this step, the bulk wafer material surrounding the recess 34 is etched until the bulk wafer has reached the desired thickness. The thickness of the remaining silicon bulk wafer material surrounding the recess 34 defines the final thickness of the membrane 24.

[0178] In a fifth step, the silicon dioxide layer 42 is removed by etching with hydrogen fluoride (HF). By this etching step, the accessible portion of the silicon dioxide layer 42 in the recess 34 is removed, whereby the via 26 in the cover layer 44 is connected to the recess 34 in the bulk wafer 40. In a final step (not shown), the membrane 24 can be cut from the bulk wafer 40 in the desired size.

[0179] use Figure 4 By using a series of MEMS techniques, a membrane 24 including through holes 26 is obtained. Using these techniques, a membrane 24 including well-defined through holes 26 is obtained, the diameter of which is significantly smaller than that obtainable by currently used manufacturing techniques. The membrane 24 allows sufficient liquid flux and has a flow resistance, which makes the membrane 24 suitable for use in the vibrating mesh module 20 of the aerosol generating device 10.

[0180] exist Figure 5 In FIG. 4 , another membrane 24 is shown, wherein an additional silicon layer 46 is arranged between two selective etch stopper layers 42A, 42B. The membrane 24 is typically formed by contacting Figure 4A similar method is obtained, except that in a first manufacturing step, a sequence of a selective etch stopper layer 42A, a silicon layer 46, a selective etch stopper layer 42B and a capping layer 44 is deposited on a silicon bulk wafer 40, such as Figure 5 As shown in the top view of Figure 5 The final structure of the membrane 24 is shown in the lower view of FIG. The thickness of the actual membrane 24 is now defined by the additional silicon layer 46, and the recesses 34 are formed in this silicon layer 46. The bulk wafer 40 is mostly etched away, and only the sidewalls 41 remain as lateral frame structures supporting the membrane 24 extending therebetween. These frame structures and the recesses 34 are again obtained by a sequence of masking and etching as described above. Figure 5 In the embodiment, only two recesses 34 are shown, but the membrane 24 may of course include a greater number of recesses 34. Figure 4 In the same manner, each recess 34 is again covered by a cover layer 44. The cover layer 44 again comprises a through hole 26 through which the liquid matrix 14 is ejected into the mouthpiece chamber 28 of the aerosol generating device 10. By using an additional silicon layer 46 between the two selective etch stopper layers 42A, B, a membrane 24 with a well-defined thickness is obtained. Therefore, this method allows a more precise control of the membrane thickness.

[0181] By appropriate selection of materials, the membrane structure can be constructed to have desired surface properties that may be beneficial to the aerosolization process. Figure 6 A membrane structure is shown in which an additional layer 48 of polysilicon is disposed below and directly adjacent to the cover layer 44. In this manner, the surface of the cover layer 44 that is in contact with the liquid matrix 14 stored in the liquid supply portion 12 is lined with the polysilicon layer 48. Since polysilicon is more hydrophilic than single crystal silicon or silicon nitride, microfluidic flow through the through-holes 26 is enhanced.

[0182] Figure 7 Shows Figure 4 A further modification of the membrane structure shown in FIG. The bulk wafer 40 forming the base substrate of the membrane 24 is patterned to have a conductive structure 50. The patterning of the membrane material can be performed using any suitable doping method known to those skilled in the art. Figure 5 In the method of FIG. 5 , the conductive structure 50 can also be formed during the vapor deposition of the material layer forming the film 24. Figure 7 As shown in FIG. 1 , the conductive structures 50 extend through portions of the membrane material adjacent to the recesses 34 and the through-holes 26, but are not exposed to the liquid matrix 14 flowing through the membrane 24. Such conductive structures 50 may form an inherently resistive heater element. By passing an electric current through these conductive structures 50, the temperature of the membrane 24 and the liquid matrix 14 to be aerosolized may be adjusted.

[0183] MEMS technology also allows the deposition of additional functional layers or components on the membrane structure.

[0184] Figure 8 A further modification of the previously described membrane structure is shown. The membrane structure is provided with an integrated piezoelectric element 52 formed on an annular contact area 54 of the membrane structure.

[0185] During the manufacturing process of membrane 24, a piezoelectric material (in this case lead zirconate titanate) is deposited on top of the membrane structure. Figure 8 As shown in , the piezoelectric material is deposited in an annularly extending contact area 54 located at the peripheral area of ​​the membrane structure 24. The deposition of the piezoelectric material is performed by a coating technique including a masking step in order to achieve the desired lateral geometry of the piezoelectric element 52. Integrally forming the piezoelectric element 52 with the membrane structure 24 makes the manufacture of the vibration grid module 20 easier than conventional manufacturing methods. In conventional manufacturing methods, the separately provided piezoelectric element 52 must be glued to the membrane module, which is usually a tedious and error-prone manufacturing step.

[0186] The membrane structure 25 may also be provided with a contact portion for electrically contacting the piezoelectric element 52 to a controller of the aerosol generating device 10. Figure 8 Such a membrane structure shown in FIG. 1 , which is additionally provided with one or more integrated piezoelectric elements 52 and electrical contacts, may also be referred to as a vibrating grid module 20. Such a vibrating grid module 20 may be used to manufacture a vibrating grid aerosol generating device 10. The vibrating grid module 20 may be manufactured as an interchangeable accessory to such an aerosol generating device 10 and may be configured to be replaced and replaced by the user himself.

[0187] Fig. 9 The connection to the upstream liquid flow chamber 60 is shown. Figure 8 The vibrating grid module 20 of the present invention. The liquid flow chamber 60 is configured to provide the liquid matrix 14 to the inlet side of the membrane structure 24. The liquid flow chamber 60 is in fluid communication with the liquid supply part (not shown) of the aerosol generating device. Fluid communication is established via the inlet 62 and the outlet 64, which allows the liquid matrix 14 to circulate freely between the flow chamber 60 and the liquid supply part. This configuration ensures that the inlet side of the membrane 24 is always in contact with the liquid matrix 14. This configuration also ensures that the excess liquid matrix 14 that is not dispersed through the through hole is sent back to the liquid supply part. With this configuration, the liquid matrix 14 is not pressed against or through the through hole of the membrane 24. This configuration allows the enhanced reproducibility of aerosol formation and avoids the undesirable leakage of the liquid matrix 14.

Claims

1. A membrane for a vibrating mesh module for use in an aerosol generating device, the membrane comprising a plurality of recesses defining portions of the membrane having a reduced thickness, wherein the portion of the membrane having reduced thickness is provided with one or more through holes to define a perforation of the membrane, and Wherein the membrane further comprises one or more piezoelectric elements formed integrally with the membrane.

2. The membrane according to claim 1, wherein the through holes have an aspect ratio lower than 3, preferably lower than 1.

3. The membrane according to any of the preceding claims, wherein the membrane comprises a through-hole density between 10 and 10,000 through-holes / mm2, preferably between 50 and 5,000 through-holes / mm2.

4. The film according to any one of the preceding claims, wherein the recesses have an aspect ratio below 3.

5. The membrane of any preceding claim, wherein the membrane comprises a plurality of layers of material.

6. Membrane according to the preceding claim, wherein the membrane comprises a bulk layer formed from a material provided in wafer form.

7. Membrane according to the preceding claim, wherein the wafer material is made of silicon, silicon oxide, silicon nitride, aluminum nitride or a combination thereof.

8. An aerosol generating device comprising a vibrating grid module for aerosolizing an aerosol-forming substrate, Wherein the vibrating grid module comprises a membrane according to any one of claims 1 to 7.

9. A method of manufacturing a membrane for a vibrating mesh module for use in an aerosol generating device, the method include: providing a bulk wafer of a first material, the bulk wafer having opposing first and second surfaces, depositing a blanket layer of a second material onto the first surface of the bulk wafer, The cover layer is provided with through holes using MEMS manufacturing techniques, etching the second surface of the bulk wafer to define a recess therein, etching the second surface of the bulk wafer until bulk wafer material is removed from the recess, Cut the membrane, Wherein the membrane further comprises one or more piezoelectric elements formed integrally with the membrane.

10. The method according to claim 9, wherein the through hole is provided to the cover layer by the following steps: masking the cover layer to define the location and size of the through holes of the membrane to be produced, The capping layer is etched to create the through hole in the capping layer.

11. A membrane for a vibrating mesh module for use in an aerosol generating device, The membrane is made of a material suitable for MEMS manufacturing, The membrane includes a plurality of through holes, wherein the material of the membrane is patterned to have a conductive structure.

12. The membrane of claim 11, wherein the conductive structure is configured to extend through a portion of the membrane material.

13. The membrane of any one of claims 1 to 7, 11 or 12, further comprising one or more piezoelectric elements deposited on a contact surface of the membrane structure.

14. A vibrating mesh module for use in an aerosol generating device, the vibrating mesh module include: A membrane according to any one of claims 1 to 7 or 11 to 13, further comprising one or more piezoelectric elements deposited on a contact surface of the membrane structure.

15. The method according to any one of claims 9 or 10, further comprising: include: The bulk wafer material is patterned to have conductive structures.

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