Membranes for vibrating mesh modules

Abstract

The present invention relates to a membrane for a vibrating mesh module used in an aerosol generating device, the membrane comprising a plurality of recesses, the recesses defining portions of the membrane having reduced thickness, the portions of the membrane having reduced thickness provided with one or more through-holes defining perforations in the membrane. The present invention also relates to a method of manufacturing a membrane for a vibrating mesh module used 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 on the first surface of the bulk wafer; providing through-holes in the cover layer using MEMS fabrication techniques; etching the second surface of the bulk wafer to define recesses therein; etching the second surface of the bulk wafer until the bulk wafer material is removed from the recesses; and cutting out the membrane.

Description

[Technical Field]

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

[0002] Aerosol generators that use a vibrating mesh module are often referred to as vibrating mesh (VM) nebulizers. Such vibrating mesh nebulizers are used to produce inhalable aerosols that can be used, for example, to treat respiratory disorders.

[0003] Vibrating mesh nebulizers use deformation or vibration of a mesh to force the liquid through the mesh. A typical vibrating mesh nebulizer uses a piezoelectric element in contact with the mesh to vibrate the mesh. The mesh is adjacent to and in direct contact with a liquid-containing substrate. The holes in the mesh may have a conical configuration, with the largest cross-section of the cone in contact with the liquid substrate. The deformation of the mesh creates a pressure field within the liquid, which forces the liquid into and fills the holes. The liquid volume displaced through the holes breaks up into droplets and is expelled into the mouthpiece chamber. The droplets mix with air to form an aerosol directly within the mouthpiece chamber. During inhalation, ambient air passes through the mouthpiece chamber, carrying the aerosol to the user.

[0004] Currently, several off-the-shelf vibrating mesh nebulizer devices are commercially available. These devices include a vibrating mesh module, which can be composed of two main parts: an annular piezoelectric element and a circular porous membrane. When the membrane is made of metal or stainless steel, the perforations are typically formed by laser drilling, which 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 combination of lithography and electroplating processes. In a first step, such membranes are perforated using a lithography process to obtain the desired hole pattern with a relatively large diameter. Next, the entire membrane is electroplated to deposit material on the surface, thereby reducing the hole size. The resulting hole shape is funnel-shaped, which is generally more favorable in terms of their microfluidic properties. Furthermore, this process can result in a lower aspect ratio, and therefore is preferred over conical laser-drilled holes for this reason.

[0005] The pore size of the membrane used in any of these commercially available devices is limited to approximately 3–4 micrometers. Therefore, the MMAD (median aerodynamic diameter) of the aerosol size distribution that can be obtained by such devices is also in the 3–4 micrometer range, which is too large for inhalation into the deep lungs. Therefore, most of the aerosol is deposited in the upper respiratory tract, which is unfavorable for efficient drug uptake and may cause throat irritation.

[0006] Conventional membranes may not be able to reduce the hole dimensions because a smaller hole diameter requires higher pressure to force the liquid through the holes. This increase can be compensated for by decreasing the hole aspect ratio (hole length divided by hole diameter). However, for mechanical stability reasons, conventional manufacturing methods do not allow for arbitrarily thin membrane thickness. Furthermore, the liquid throughput rate per hole decreases quadratically with decreasing pore size. Therefore, to maintain the desired aerosol throughput, such membranes must contain a significantly larger number of holes.

[0007] Finally, standard manufacturing techniques for VM modules can require several tedious assembly steps, including bonding the piezoelectric actuators to the porous membrane. If the bonding is not done properly, the energy conversion efficiency of the VM module can decrease and damage can occur during operation. Additionally, adhesives may be incompatible with some liquids used in VM modules, posing a risk of liquid contamination and requiring additional protective measures.

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

[0009] It would be desirable to provide a porous membrane that allows for the production of aerosol particles with reduced diameter while at the same time maintaining the volume of the aerosol produced.

[0010] It would further be desirable to provide a manufacturing method that allows for the reliable and reproducible production of porous membranes with specific aerosol generating properties. In particular, it would be desirable to provide a method for manufacturing a vibrating mesh module without the need for adhesives or bonding processes.

[0011] In summary, there is a need in the art to produce membranes for VM modules with smaller exit hole diameters, smaller through-hole aspect ratios, increased hole counts, and no adhesives used to assemble the modules. Summary of the Invention

[0012] According to one embodiment of the present invention, there is provided a membrane for a vibrating mesh module for use in an aerosol generating device, the membrane comprising a plurality of recesses that define portions of the membrane having a reduced thickness h, the portions of the membrane having reduced thickness h having one or more through holes that define perforations in the membrane.

[0013] By providing a membrane with recesses, portions of the membrane are defined that have reduced thickness. The overall structural stability of such a membrane is maintained by the non-recessed portions of the membrane. At the same time, the recesses with reduced thickness allow for the definition of through-holes therein having diameters small enough to generate aerosol droplets for inhalation into the deep lungs.

[0014] The through-holes formed in the recesses may have a diameter of 0.1 to 4 micrometers, or 0.2 to 3 micrometers.

[0015] The diameter of the through-holes on the membrane is a key parameter for determining the resulting aerosol droplet size. The smaller the diameter, the smaller the droplets formed upon aerosolization. The through-hole diameter of conventional membranes manufactured with currently available technology is limited to approximately 3-4 micrometers. Similarly, the median aerodynamic diameter (MMAD) of the aerosol particle size distribution ranges from 3-4 micrometers. In contrast, the membranes described herein have through-holes with smaller diameters, thus enabling a smaller MMAD of the aerosol particle size distribution.

[0016] A through-hole in a membrane may have an aspect ratio of less than 3. A 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 in a 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 advantageous. The smaller the aspect ratio, the less pressure is required to force liquid through the through-hole.

[0017] The through-holes may have any hole shape. The through-holes may be circular in cross section. A circular cross section provides the highest ratio of opening cross-sectional area to bounding surface area, which helps reduce microfluidic flow resistance through the hole. However, the through-holes may be formed to have any other desired cross-sectional shape. For simplicity, references to the lateral dimensions of the through-holes will often refer herein to the diameter of the through-hole. In the case of through-holes of non-circular cross section, the term "diameter" shall be interpreted as referring to the largest lateral dimension of the through-hole.

[0018] The thickness of the non-recessed portions of the film can be significantly greater than the thickness of the remaining film in the recesses. The film may be 5 micrometers to 500 micrometers thick. The film may be 10 micrometers to 400 micrometers thick. The film may be 30 micrometers to 200 micrometers thick. The film thickness has a significant effect on the mechanical behavior of the film. Therefore, the film thickness can be selected depending on the target operating frequency and the properties of the film material.

[0019] As explained above, the membrane is provided with recesses that define portions of the membrane having reduced thickness. The recesses themselves may have any desired cross-sectional shape. The recesses may have a circular cross-sectional shape. The diameter of the recesses may be in the range of 5 micrometers to 300 micrometers. The diameter of the recesses may be in the range of 10 micrometers to 200 micrometers. The diameter of the recesses may be in the range of 15 micrometers to 100 micrometers.

[0020] The above geometric dimensions allow the formation of recesses covering a wide range of aspect ratios. However, it is preferable to form recesses so that the aspect ratio is less than 3. The aspect ratio of the recesses is the same as that described above for the aspect ratio of the through-holes. The smaller the aspect ratio of the recesses, the smaller the pressure required to force the liquid out of the recesses.

[0021] Each recess has 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 have 1 to 1500 through holes. The recess may have 10 to 1000 through holes.

[0022] The density of the through holes in the entire membrane may be 10 to 10,000 holes / mm 2. The density of the through holes in the entire membrane may be 50 to 5,000 holes / mm 2 .

[0023] The details of the final configuration of the membrane can be selected depending on the liquid substrate to be aerosolized.The details of the final configuration of the membrane can be selected depending on the desired liquid throughput.

[0024] The liquid throughput per through-hole is highly dependent on the diameter and open area of ​​each through-hole. Therefore, the liquid throughput of a through-hole decreases quadratically with decreasing hole diameter. Therefore, to maintain a desired throughput for a membrane with smaller through-holes, the number of through-holes in the membrane must be increased accordingly. Furthermore, the aspect ratio of the through-holes must be reduced to maintain a sufficiently low pressure to force the liquid out of the through-holes. Therefore, the final configuration of the membrane may need to take these factors into account. The final configuration may also need to be adapted to the properties of the liquid to be aerosolized. The configuration may depend, inter alia, on the viscosity of the liquid to be aerosolized.

[0025] The membrane may be fabricated using microelectromechanical systems (MEMS) fabrication techniques, including process techniques used in semiconductor device fabrication, which involve depositing a layer of material, patterning it by photolithography, and etching the material to create the required shape.

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

[0027] The membrane structure may include multiple layers of different materials, which may be applied to a bulk wafer by thin film deposition techniques.

[0028] MEMS technology allows for the tailoring of hole morphology and shape to meet application needs. As mentioned above, this specifically includes the diameter of the through-holes, which is a key parameter for tailoring the size of the resulting aerosol droplets. MEMS technology also allows for the definition of the aspect ratio of the through-holes, which is a key parameter for enabling and controlling microfluidic flow through the through-holes. As described in more detail below, the MEMS fabrication process may include multiple photolithographic masking and etching steps. The lateral size of the mask determines the lateral placement and size of the recesses and through-holes in the membrane structure, making it easily tailored to specific needs. The combination of the etchant, wafer material, and wafer lattice orientation allows for the determination of the cross-sectional shape of the etched recesses and the resulting recess depth. Subsequent etching steps, therefore, enable the fabrication of complex shapes for the recesses and through-holes in the membrane structure.

[0029] Etching may be performed by wet 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 independent of lattice orientation. In contrast, most wet etching techniques are anisotropic, meaning that the resulting pattern is determined not only by the mask but also by the lattice orientation, e.g., <100> KOH etching of oriented silicon results in pyramidal shapes throughout the thickness of the film at angles determined by the orientation of the lattice planes.

[0030] The present invention further relates to an aerosol-generating device having a vibrating mesh 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 including the aerosol-forming substrate and a cartridge including the aerosol-forming substrate. The aerosol-generating device may comprise a housing, an electrical circuit including a controller, a power source, and multiple sensors.

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

[0032] The present invention further relates to a method for manufacturing a membrane for a vibrating mesh module for use in an aerosol generating device, the method comprising:

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

[0034] depositing a cover layer of a second material on the first surface of the bulk wafer;

[0035] providing a through hole in the cover layer using MEMS fabrication 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] and excising the membrane.

[0039] The method of fabricating the membrane is also used in MEMS fabrication and may involve multiple manufacturing steps, which may include processes such as depositing a layer of material, patterning by photolithography, and etching the material to create the required shape.

[0040] Thin film deposition can be achieved by techniques such as evaporation, magnetron sputtering, or physical vapor deposition (PVD), including pulsed laser deposition (PLD). Using these techniques, one or more layers of materials can be deposited in a desired sequence on a bulk wafer.

[0041] Photolithography is a well-known technique that uses light to form finely patterned thin films of a suitable material on a bulk substrate, protecting selected areas of the substrate during subsequent etching, deposition, or implantation operations. Typically, ultraviolet light is used to transfer a geometric design from an optical mask to a light-sensitive chemical (photoresist) coated on the substrate. The photoresist dissolves, or hardens, when exposed to light. A suitable solvent is then used to remove the softened portions of the coating, forming a patterned film.

[0042] The etching step may be performed by wet etching or dry etching, or a combination thereof. Dry etching, for example reactive ion etching or plasma etching, may be preferred as it can be used to create perpendicular edges in the substrate, regardless of the crystallographic orientation of the substrate. Wet etching techniques can also be used. However, these techniques are usually anisotropic, and the resulting pattern is not only determined by the mask already applied, but may also depend on the lattice orientation. For example, <100> KOH etching of oriented silicon results in pyramidal shapes throughout the thickness of the film at angles determined by the orientation of the lattice planes.

[0043] The bulk wafer may be made of any first material suitable for processing by MEMS fabrication techniques. The bulk wafer material may 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 may also be selected from any material suitable for processing by MEMS fabrication techniques. The material of the one or more additional layers applied to the bulk wafer may be selected from silicon, silicon oxide, silicon nitride, aluminum nitride, or a combination thereof. Furthermore, the additional layer may be formed from a material with specific functional properties, such as a selective etch stopper or a material that enhances the flow properties of the aerosolized liquid substrate.

[0044] In a method for fabricating a membrane for a vibrating mesh module for use in an aerosol generating device, a first material, e.g., a bulk wafer of silicon, is provided. Wafer material is commercially available in a variety of dimensions. The final membrane structure may have a thickness of 5 micrometers to 500 micrometers. The membrane may have a thickness of 10 micrometers to 400 micrometers. The membrane may have a thickness of 30 micrometers to 200 micrometers. The thickness of the membrane structure has a significant impact on the mechanical behavior of the membrane. Therefore, the thickness of the membrane can be selected depending on the target operating frequency and the material properties of the membrane. As described in more detail below, the final thickness of the membrane structure may be adjusted by a selective etching step during the fabrication method.

[0045] Deposition of the cover layer on the first surface of the bulk wafer may be performed by any of the physical vapor deposition (PVD) techniques described above. The cover layer may be formed from silicon dioxide or silicon nitride.

[0046] The cover layer may have a thickness of 0.1 micrometers to 5 micrometers. The cover layer may have a thickness of 0.2 micrometers to 3 micrometers. The cover layer may have a thickness of 0.3 micrometers to 1 micrometer. The thickness of the cover layer and the dimensions of the through-holes defined therein are important parameters for controlling the resulting MMAD (mass median aerodynamic diameter). A small aspect ratio is desirable for microfluidic considerations. Therefore, a thin cover layer may be preferred. The final thickness selection may represent a trade-off with mechanical stability, which may set a lower limit for the cover layer thickness. This lower limit depends on the lateral extent of the cover layer and the forces expected to be applied to the cover layer during use.

[0047] Thereafter, through-holes are provided in the cover layer using another MEMS manufacturing technique. The through-holes through the cover layer can be obtained by a combination of photolithography and etching. For this purpose, the cover layer may be provided with a mask that determines the size and position of the through-holes on the cover layer. In a subsequent etching step, the unmasked areas of the cover layer are etched away, resulting in a plurality of through-holes in the cover layer.

[0048] The through-holes formed in the recesses may have a diameter of 0.1 to 4 micrometers, or 0.2 to 3 micrometers.

[0049] In another method step, the second surface of the bulk wafer is treated to define recesses therein. These recesses can be obtained, as before, by masking and subsequent etching of the bulk wafer material. Etching of the silicon bulk wafer can be performed using sulfur hexafluoride (SF6). 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 to coincide with the positions of the through holes provided in the cover layer. The bulk wafer and the cover layer combine to form a membrane structure having recesses of reduced thickness.

[0050] Etching the second surface of the bulk wafer may determine the final thickness of the membrane structure, which primarily determines the vibration characteristics of the membrane structure.

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

[0052] In the final step, the membrane is cut from the bulk wafer material. The membrane is cut to the required dimensions as needed for this application. Because the bulk wafer size is typically much larger than the required dimensions of the membrane, this manufacturing method allows for multiple membrane structures to be fabricated simultaneously on a single bulk wafer. This parallel processing allows for convenient mass production of membranes.

[0053] One or more additional material layers can be applied to the fabrication of the film. For example, an additional layer can be deposited between the bulk wafer and the cover layer. This additional cover layer can be configured as a selective etch stopper layer. Such a selective etch stopper layer can protect the cover layer on the first surface of the bulk wafer when a recess is formed on the second surface of the bulk wafer. The selective etch stopper layer ensures that the etching process for forming the recess on the second surface of the bulk wafer is terminated when the etching solution removes the bulk wafer material from the recess and reaches the selective etch stopper layer. This is typically achieved by forming the selective etch stopper layer from a material that does not dissolve when in contact with the etching agent used to etch the bulk wafer material. The selective etch stopper layer can then be removed using another etching solution.

[0054] The thickness of the selective stopper layer can be suitably selected and may be in the range of several nanometers to 20 micrometers.

[0055] In the above example where sulfur hexafluoride is used to etch a silicon bulk wafer, the selective etch stop layer may be formed from any material that does not dissolve when in contact with sulfur hexafluoride. In this regard, a suitable material is silicon dioxide. Because silicon dioxide does not dissolve when in contact with sulfur hexafluoride, the vertical etching process of the bulk wafer will stop when the etching solution reaches the silicon dioxide layer. This silicon dioxide layer may then be removed by another etchant, such as hydrogen fluoride (HF) or trifluoromethane (CHF).

[0056] Typically, techniques using selective etch-stop layers are used to provide layers of a predetermined thickness in a film structure. In this way, the material that determines the thickness of the film itself may also be deposited as a layer of material sandwiched between two layers of selective etch-stop material. In this way, specific thin films can be provided. In this way, films with well-defined thicknesses can also be provided. The thickness of such films may be the same as those described above for films etched from bulk wafer material. The thickness of such films may range from 30 micrometers to 150 micrometers.

[0057] Fabricating membranes using MEMS technology allows for the construction of membrane structures with desirable surface properties beneficial to the aerosolization process. Specifically, the material properties of the surfaces that form the through-holes and that may come into contact with the liquid substrate to be aerosolized can be engineered to have such desirable surface properties.

[0058] For example, a layer of polycrystalline silicon may be provided below and directly adjacent to the cover layer, such that the inlet faces of the through-holes in the cover layer are covered with the layer of polycrystalline silicon. Polycrystalline silicon is more hydrophilic than single-crystal silicon or silicon nitride, thereby enhancing microfluidic flow through the through-holes.

[0059] The individual method steps described above may also be performed in different orders, and those skilled in the art may vary the order of the individual manufacturing steps as deemed suitable.

[0060] The present disclosure also relates to a membrane for a vibrating mesh module for use in an aerosol generating device, the membrane comprising bulk wafer material processed by MEMS fabrication, the membrane comprising a plurality of through-holes, the membrane material being patterned with conductive structures, such that when an electric current is passed through the conductive tracks, the conductive tracks can function as a built-in resistive heater.

[0061] MEMS fabrication allows for the incorporation of specific membrane functional features that are difficult to achieve with traditional membrane fabrication techniques or that were previously only available as add-ons to vibrating mesh modules. According to the present disclosure, such functional features can be incorporated into bulk wafer material during the fabrication process. For example, the bulk wafer material that serves as the basis for the fabrication of the membrane may be provided with a pattern of conductive structures at the beginning of the fabrication process. Other details of the membrane, such as the application of additional layers or etching of recesses, may then be achieved 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 to extend through a portion of the membrane material adjacent to the through-hole but not exposed to the liquid substrate flowing through the membrane. In this way, the conductive structure can be protected from direct contact with the aerosolized liquid material. This may help prevent degradation of the conductive structure. This may also help prevent undesirable effects on the liquid substrate due to contact with the material of the conductive structure.

[0063] To allow current to flow through the conductive structure, the end of the conductive structure may reach the outer surface of the membrane structure at a location where there is no liquid flow and no risk of the contact portion coming into contact with the liquid substrate being aerosolized. Such a location may be close to the periphery of the membrane structure. Specifically, the membrane may include contact pads on its periphery to establish electrical contact with the conductive structure.

[0064] When the aerosol generator is in use, an electric current can be passed through the conductive structure, which acts as an internal heater element that allows the operating temperature of the membrane to be adjusted.

[0065] The use of an integrated heater element can ensure that the temperature of the liquid substrate flowing through the through-holes is a well-defined temperature. Specifically, the heater element can ensure that the temperature of the liquid substrate is largely independent of external conditions, such as ambient temperature. The amount of liquid flowing through the through-holes with each cycle is quite small, possibly only a few microliters per second. Furthermore, the target temperature increase is also relatively small, likely only a few tens of Kelvin above ambient temperature. Therefore, the heating power required to achieve the temperature increase in the liquid substrate is quite low. Thus, the liquid is heated almost instantaneously upon reaching the membrane and passing through the through-holes. This advantageous effect is achieved by focusing the heating around the through-holes in the membrane, while avoiding the need to heat the entire bulk liquid in the reservoir.

[0066] Increased temperature of the liquid substrate near or within the through-holes can also locally decrease the viscosity of the liquid substrate. Thus, the use of a heated membrane allows liquid substrates that may be too viscous at room temperature or lower ambient temperatures to be used in aerosol generating devices equipped with such membrane modules with built-in heater elements. This modification generally expands the design range of liquids that can be used in such devices. Liquid substrates with increased viscosity can have the beneficial effect of reducing substrate leakage.

[0067] The temperature of the heater element may be kept below the boiling point of the liquid substrate being aerosolized. The primary reason for this is that the primary source of aerosolization should be the physical interaction of the liquid substrate with the vibrating mesh module. Instead, aerosolization caused by heating and evaporation of the liquid substrate, followed by recondensation, should be avoided in such a system.

[0068] Because typical liquid substrates aerosolized by vibrating mesh devices contain a large amount of water, the heater element target temperature should not exceed 100 degrees Celsius. The difference between the heater element target temperature and the ambient temperature should not exceed 80 degrees Celsius. The difference between the heater element target temperature and the ambient temperature should not exceed 60 degrees Celsius. The difference between the heater element target temperature and the ambient temperature should not exceed 40 degrees Celsius.

[0069] The main advantage of a vibrating mesh module for an aerosol generator with an integrated heater element appears to be related to the stabilization of the operating point with respect to the ambient temperature. By using an integrated heater, more uniform aerosolization conditions are achieved, resulting in a more consistent user experience.

[0070] Furthermore, a vibrating mesh module for an aerosol generating device with a built-in heater element may expand the design scope of such devices. Liquid substrates with higher viscosities may also be used. The use of liquid substrates can have beneficial effects on substrate handling, particularly preventing substrate leakage from the source.

[0071] The present disclosure also relates to a membrane for a vibrating mesh module for use in an aerosol generating device, the membrane including bulk wafer material processed by MEMS fabrication, the membrane including a plurality of through holes.

[0072] MEMS fabrication can allow for the incorporation of piezoelectric elements into the vibrating mesh module during the manufacturing process. The piezoelectric elements may be deposited onto the membrane module. Incorporating the piezoelectric elements already during the fabrication of the membrane module facilitates the attachment of the piezoelectric elements to the membrane module. Conventional manufacturing methods require the piezoelectric elements to be glued to the membrane module, which can typically be a tedious and fault-prone manufacturing step.

[0073] Furthermore, growing the piezoelectric elements directly on the membrane module allows for a more targeted geometric design of the piezoelectric elements. The piezoelectric material may be deposited at specific, predetermined locations on the membrane module. Deposition of the piezoelectric material may be done by MEMS techniques, for example, sputtering or coating techniques. A mask may be used to achieve the desired lateral shape of the piezoelectric patch. Alternatively, the desired lateral shape can be achieved by forming an entire layer of piezoelectric material and then removing the piezoelectric material from locations where it is not required. Such removal can again be done 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 on the periphery of the membrane structure. If deemed useful, contact areas may also be defined on other surface areas of the membrane structure.

[0075] In principle, any material suitable for manufacturing piezoelectric elements can be used, including lead zirconate titanate, zinc oxide, barium titanate, aluminum nitride, scandium aluminum nitride, lithium niobate, ferroelectric ceramics with a perovsite structure, and combinations thereof.

[0076] The membrane structure disclosed above may further include one or more integrated piezoelectric elements and may also be referred to as a vibrating mesh module. Such a vibrating mesh module may be used in the manufacture of a vibrating mesh aerosol generating devices. Such a vibrating mesh module may also be manufactured and sold as a replaceable accessory for such devices. Accordingly, the present disclosure also relates to a vibrating mesh module for an aerosol generating device and a corresponding method of manufacturing the same.

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

[0078] MEMS fabrication also offers the possibility of incorporating at least part of the necessary electronic circuitry directly into the material of the membrane structure of the vibrating mesh module. Specifically, the electronic circuitry may be integrally formed within 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, as well as sensor components.

[0079] The vibrating mesh module may include one or more piezoelectric elements. The vibrating mesh module may include one or more piezoelectric elements integrally formed with the membrane structure of the vibrating mesh module. The piezoelectric elements can be integrated into the membrane structure fabrication using MEMS fabrication techniques. Additionally, the vibrating mesh module may include contact pads for each of the piezoelectric elements. These contact pads may be electrically connected to the piezoelectric elements or integrally formed within the material of the membrane structure. The contact pads may be shaped and configured to allow electrical contact with corresponding contact pins of the aerosol generating device. This structure allows for easy user replacement of the vibrating mesh module. To further facilitate such replacement, the aerosol generating device and the vibrating mesh module may be configured so that the vibrating mesh module can slide into the aerosol generating device. When the vibrating mesh module is slid into the aerosol generating device, the contact pins of the device can contact the contact pads of the module. Using multiple piezoelectric elements may allow different vibration modes of the membrane to be excited depending on which piezoelectric elements are powered at which frequencies. This can alter the aerosol formation process and the properties of the resulting aerosol.

[0080] The vibrating mesh module may further include one or more sensors embedded within the material of the vibrating mesh module or within 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 the controller of the aerosol generating device. Because the sensors are embedded directly within the material of the vibrating mesh module, the sensors may provide an immediate and direct response from the vibrating mesh module.

[0081] The present invention further relates to a method of manufacturing a membrane for a vibrating mesh module for use in an aerosol generating device as described above, the method further comprising the steps of a method for patterning bulk wafer material with conductive structures.

[0082] The patterning step may be performed before etching of the bulk wafer material. Specifically, the patterning step may be performed as a first method step after providing the bulk wafer material. The pattern of conductive structures may be such that the conductive structures are disposed adjacent to the through-holes of the membrane.

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

[0084] The present invention further relates to a method for manufacturing a membrane for a vibrating mesh module for use in the above-mentioned aerosol generating device, the method further comprising the step of providing one or more piezoelectric elements integrally formed on the contact surface of the membrane structure.

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

[0086] Alternatively, the desired lateral shape of the piezoelectric elements may be obtained by depositing an entire layer of piezoelectric material on the contact surface of the membrane and then removing the piezoelectric material where it is not required. Forming the piezoelectric elements already during the fabrication of the membrane module potentially avoids the tedious and error-prone manufacturing step of gluing the piezoelectric elements to the membrane structure, which is performed in conventional manufacturing methods of vibrating mesh modules.

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

[0088] The electronic circuitry integrally formed within the material of the vibrating mesh module may include contacts for the piezoelectric elements. The electronic circuitry integrally formed within 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. Additionally, these sensors may be used to provide feedback to the aerosol generating device controller. Because the sensors are located directly within the material of the vibrating mesh module, the sensors may provide an immediate and direct response from the vibrating mesh module. [Example]

[0090] The following provides a non-exhaustive list of non-limiting examples, any one or more of the features of which may be combined with any one or more features of any other example, embodiment, or aspect described herein.

[0091] Example 1: 1. A membrane for a vibrating mesh module for use in an aerosol generating device, comprising: the membrane includes a plurality of recesses defining portions of the membrane having a reduced thickness; A membrane, wherein the portion of the membrane having a reduced thickness is provided with one or more through holes that define perforations in the membrane. Example 2: The membrane of Example 1, wherein the through-holes have a diameter of 0.1 to 5 micrometers, preferably 0.2 to 3 micrometers. Example 3: The membrane according to any one of Examples 1 to 2, wherein the through-holes have an aspect ratio of less than 3, preferably less than 1. Example 4: The membrane of any one of Examples 1 to 3, wherein the through-holes have a circular cross section. Example 5: The membrane according to any one of Examples 1 to 4, wherein the membrane has a thickness of 5 micrometers to 500 micrometers, 10 to 400 micrometers, or 30 to 200 micrometers. Example 6: 6. The membrane of any one of Examples 1 to 5, wherein the recesses defining the portions of the membrane having reduced thickness have a diameter of 5 micrometers to 300 micrometers, preferably 10 to 200 micrometers, preferably 15 to 100 micrometers. Example 7: The membrane according to any one of Examples 1 to 6, wherein the recess comprises 1 to 1500 through-holes, preferably 10 to 1000 through-holes. Example 8: The membrane of any one of Examples 1 to 7, wherein the membrane comprises a perforation density of 10 to 10,000 perforations per square millimeter, preferably 50 to 5,000 perforations per square millimeter. Example 9: The film according to any one of Examples 1 to 8, wherein the recesses have an aspect ratio of less than 3. Example 10: The membrane of any one of Examples 1 to 9, wherein the membrane comprises multiple layers of material. Example 11: The membrane of example 10, wherein the membrane comprises a bulk layer formed from a material provided in the form of a wafer. Example 12: The membrane of Example 11, wherein the wafer material is made of a material suitable for MEMS fabrication. Example 13: The membrane of example 12, wherein the wafer material is made of silicon, silicon oxide, silicon nitride, aluminum nitride, or a combination thereof. Example 14: a vibrating mesh module for aerosolization of the aerosol-forming substrate; An aerosol generating device, wherein a vibrating mesh module comprises the film according to any one of Examples 1 to 13. Example 15: 1. A method of manufacturing a membrane 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 on the first surface of the bulk wafer; providing a through hole in the cover layer using MEMS fabrication 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; and excising the membrane. Example 16: The through hole is masking the cover layer to define the placement and dimensions of the through-holes in the membrane to be produced; and etching the cover layer to form through-holes in the cover layer. Example 17: 17. The method of example 15 or 16, further comprising depositing an additional layer between the bulk wafer and the cover layer, the additional layer configured as a selective etch stop layer. Example 18: depositing an additional selective etch stop layer between the bulk wafer and the cover layer; and depositing a layer of additional material between the two selective etch stop layers, the thickness of the layer of additional material determining the thickness of the film produced. Example 19: 19. The method of any one of Examples 15-18, wherein the material of the bulk wafer and / or the layer of additional material is selected from silicon, silicon oxide, silicon nitride, aluminum nitride, or a combination thereof. Example 20: 19. The method of any one of Examples 15-18, further comprising depositing an additional layer of material under the cover layer, the additional layer allowing for tailoring of surface properties of the material defining the through holes of the membrane. 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. Example 22: 22. The method of any one of embodiments 20 or 21, wherein the additional layer is a layer of polycrystalline silicon. Example 23: 1. A membrane for a vibrating mesh module for use in an aerosol generating device, comprising: the membrane is made from a material suitable for MEMS fabrication; A membrane, wherein the membrane comprises a plurality of through holes, and wherein the material of the membrane is patterned with conductive structures. Example 24: 24. The membrane of example 23, wherein the conductive structure is configured to extend through a portion of the membrane material. Example 25: 25. The membrane of any one of Examples 23 or 24, wherein the conductive structure is disposed adjacent to the through-holes but does not touch the liquid flow path defined through the through-holes of the membrane. Example 26: 26. The membrane of any one of Examples 23 or 25, wherein the membrane comprises contact pads on its periphery for establishing electrical contact to a conductive structure. Example 27: 27. The membrane of any one of Examples 23 or 26, wherein, in use, an electric current is passed through the conductive structure, which functions as a heater element, allowing the operating temperature of the membrane to be adjusted. Example 28: The membrane of any one of Examples 1-14 or 23-27, further comprising one or more piezoelectric elements deposited on a contact surface of the membrane structure. Example 29: 29. The membrane of example 28, wherein the contact surface is an annular portion disposed on the periphery of the membrane structure. Example 30: 30. The 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, aluminum scandium nitride, lithium niobate, or ferroelectric ceramics having a perovsite structure. Example 31: 1. A vibrating mesh module for use in an aerosol generating device, the vibrating mesh module comprising: A vibrating mesh module comprising the membrane according to any one of Examples 1 to 14 or 23 to 27, and further comprising one or more piezoelectric elements deposited on the contact surface of the membrane structure. Example 32: The membrane of any one of Examples 1-14 or 23-30, wherein the electronic circuitry is integrally formed within the material of the vibrating mesh module. Example 33: The film of examples 1-32, wherein the electronic circuitry comprises an electronic contact structure for one or more piezoelectric elements of the film structure. Example 34: 34. The membrane of any one of Examples 32-33, wherein the electronic circuit comprises one or more sensor elements. Example 35: 35. The membrane of example 34, wherein the one or more sensor elements are selected from a temperature sensor, a stress bending sensor, or an acceleration sensor. Example 36: 36. The membrane of any one of Examples 34-35, wherein the sensor is used for device diagnostics during operation or to provide feedback to a controller of the aerosol generating device. Example 37: The method is 23. The method of any one of examples 15-22, further comprising patterning the bulk wafer material with conductive structures. Example 38: The method of example 37, wherein the conductive structure is a metal track. Example 39: 39. The method of any one of Examples 37 or 38, wherein the patterning step is performed before etching the bulk wafer material. Example 40: 23. The method according to any one of embodiments 15 to 22, wherein one or more piezoelectric elements are integrally formed on the contact surface of the membrane structure. Example 41: The method of example 40, wherein the piezoelectric element is deposited on the contact surface of the membrane structure by sputtering or by a coating technique. Example 42: 42. The method of claim 41, wherein the desired lateral shape of the piezoelectric element is obtained by using a mask. Example 43: 43. The method of example 42, wherein the desired lateral shape of the piezoelectric element is obtained by depositing a full layer of piezoelectric material on the membrane contact surface and then removing the piezoelectric material at locations where it is not required. Example 44: 23. The method of any one of embodiments 15-22, wherein the electronic circuitry is integrally formed within the material of the vibrating mesh module during manufacture. Example 45: 45. The method of example 44, wherein the electronic circuit comprises one or more sensor elements selected from a temperature sensor, a stress bending sensor, or an acceleration sensor. Example 46: The method of example 45, wherein the sensor is used for device diagnostics during operation or to provide feedback to a controller of the aerosol generating device.

[0092] Features described with respect to one embodiment may be equally applied to other embodiments of the invention.

[0093] The invention will now be further described, by way of example only, with reference to the accompanying drawings in which: [Brief explanation of the drawings]

[0094] [Figure 1]FIG. 1 shows the schematic design of a conventional vibrating mesh nebulizer. [Figure 2] 2A-2C show the geometries of through-holes in membranes obtained by various manufacturing methods. [Figure 3] 3A-3C show a detailed view of the MEMS membrane. [Figure 4] FIG. 4 illustrates the steps of a method for manufacturing a MEMS membrane. [Figure 5] FIG. 5 shows a modification of the method of FIG. [Figure 6] FIG. 6 shows a MEMS membrane provided with a hydrophilic layer. [Figure 7] FIG. 7 shows a MEMS membrane with an integrated heater. [Figure 8] FIG. 8 shows a MEMS membrane provided with an integrated piezoelectric element. [Figure 9] FIG. 9 shows the VM module connecting to the upstream liquid flow chamber. DETAILED DESCRIPTION OF THE INVENTION

[0095] FIG. 1 shows an aerosol generating device 10, which may also be referred to as a nebulizer. The nebulizer includes a liquid reservoir 12 that holds a supply of liquid substrate 14 to be aerosolized. A vibrating mesh module 20 is provided that includes an annular piezoelectric element 22 surrounding a circular mesh in direct contact with the liquid substrate 14. The mesh is configured as a membrane 24 with perforations 26. The perforations 26 in the membrane 24 have a conical configuration, with the largest cross-section of the cone in contact with the liquid formulation. Vibration of the membrane 26 forces the liquid substrate 14 through the perforations 26 and into a mouthpiece chamber 28 where it is sprayed. During inhalation, ambient air passes through the mouthpiece chamber 28, carrying the generated aerosol 30 to the user.

[0096] The size of the perforations 26 at the exit surface of the membrane 24, as well as the aspect ratio of the perforations 26, are important parameters for determining the aerosolization process. FIG. 2 shows an enlarged schematic view of a membrane 24 with perforations 26. The membranes 24 are arranged in descending order from left to right according to the aspect ratio AR of their perforations 26. This order is indicated by the arrows pointing from left to right in FIG. 2. Each membrane 24 has the same thickness H, and the perforations 26 have the same minimum diameter d at the exit surface 32 of the membrane 24. The perforations 26 in the membrane 24 can be obtained by various manufacturing methods, each of which results in perforations 26 with different aspect ratios. Generally, the aspect ratio AR of a perforation 26 is determined by dividing its length by its diameter.

[0097] The membrane 24 shown in FIG. 2A is made of stainless steel. Through-holes 26 therein are formed by laser drilling. Laser drilling results in through-holes 26 having a conical shape with a small taper angle. The through-holes 26 thus obtained have a relatively large aspect ratio A R These through holes have an aspect ratio A R may 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.

[0098] The membrane 24 shown in FIG. 2B is made of a nickel-cobalt alloy. Through-holes 26 therein are formed by lithography and subsequent electroplating. In a first step, lithography is used to form a pattern of through-holes 26 with relatively large diameters in the membrane 26. Subsequently, electroplating is performed across the membrane 24 to deposit material on the membrane surface, thereby reducing the diameter of the through-holes 26. This results in through-holes 26 with a funnel-like shape. These through-holes 26 may be preferable to laser-drilled through-holes 26 due to their slightly smaller aspect ratio AR.

[0099] The membrane 24 shown in Figure 2C is a membrane 24 according to the present disclosure. The membrane 24 includes a recess 34 in which a through-hole 26 is provided. The remaining thickness H of the membrane 24 within the recess 34 is significantly smaller than the overall thickness H of the membrane 24. Therefore, the aspect ratio AR of the through-hole 26 of such a membrane 24 may be expressed as the quotient h / d, which is much smaller than the aspect ratio AR of the through-hole 26 of the membrane 24 shown in Figures 2A and 2B.

[0100] In Figure 3, a portion of a membrane 24 according to the present disclosure is shown in more detail. Figure 3A shows an enlarged view of a recess 34 in such membrane 24. Membrane 24 is made of silicon and has an overall thickness H. Recess 34 has a circular cross section with a diameter D and a depth t. The thickness h of the recessed portion of membrane 24 is determined as h = Ht. A plurality of through-holes 26 are provided in recess 34. These through-holes 26 also have a circular cross section and a diameter d that is much smaller than the diameter D of recess 34.

[0101] As shown in FIG. 3B, the membrane 24 may have a plurality of recesses 34, and each of the recesses 34 may have a plurality of through holes 26 through which the liquid substrate 14 is released into the mouthpiece chamber 28 of the aerosol generating device 10.

[0102] Figure 3C shows an electron microscope image of a portion of a membrane comprising recesses 34. The membrane is approximately 100 micrometers thick. The circular recesses 34 have a diameter D of approximately 50 micrometers. The remaining thickness h of the recesses 34 is 1 micrometer. The recesses comprise 14 circular through-holes 26 uniformly distributed in a hexagonal pattern within the recesses 34. The diameter d of the through-holes 26 is approximately 2 micrometers. Thus, the aspect ratio of the through-holes in the membrane shown in Figure 3C is approximately 0.5.

[0103] The membrane 24 shown in FIG. 3 can be manufactured by a series of manufacturing steps involving various MEMS processing techniques. A suitable manufacturing method is illustrated in FIG. 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 layers of material 42, 44 are formed by thin film deposition. Layer 42 is made of silicon dioxide and serves as a selective etch stop layer. Layer 44 is deposited on top of layer 42, made of silicon nitride. Layer 44 serves as a cover layer for membrane 24.

[0104] In a second step, a mask defining the location and diameter of the through-holes 26 is lithographically applied to the cover layer 44. The cover layer 44 is then dry etched with carbon tetrafluoride (CF4) to locally remove material of the cover layer 44 and form the through-holes 26 in the silicon nitride cover layer 44.

[0105] In a third step, recesses are defined on the second or back surface of the silicon bulk wafer 40. For this purpose, a mask defining the position and cross-section of the recesses is applied lithographically to the second surface of the bulk wafer 40. The recesses 34 are then formed by etching the second surface of the silicon bulk wafer 40 with sulfur hexafluoride (SF6).

[0106] In a fourth step, the entire second surface of the silicon bulk wafer 40 is further etched until the bulk wafer material is removed from the recess 34. Due to the use of a selective etch stop layer 42 made of silicon dioxide, which does not dissolve when in contact with sulfur hexafluoride, the etching of the recess 34 stops when it reaches the silicon dioxide layer 42. In this step, the bulk wafer material surrounding the recess 34 is etched until the bulk wafer reaches a desired thickness. The thickness of the remaining silicon bulk wafer material surrounding the recess 34 determines the final thickness of the membrane 24.

[0107] In a fifth step, the silicon dioxide layer 42 is removed by etching with hydrogen fluoride (HF). This etching step removes the accessible portions of the silicon dioxide layer 42 within the recesses 34, thereby connecting the through holes 26 in the cover layer 44 to the recesses 34 in the bulk wafer 40. In a final step (not shown), the membrane 24 can be cut to the desired size from the bulk wafer 40.

[0108] 4, a membrane 24 with through-holes 26 is obtained by utilizing a series of MEMS techniques. These techniques are used to obtain a membrane 24 with well-defined through-holes 26 having diameters significantly smaller than those obtainable with currently used manufacturing techniques. The membrane 24 allows for sufficient liquid throughput and has a flow resistance suitable for use in a vibrating mesh module 20 for an aerosol generation device 10.

[0109] FIG. 5 shows another membrane 24, with another silicon layer 46 disposed between two selective etch-stop layers 42A, 42B. The membrane 24 is generally obtained in a manner similar to that described in FIG. 4 , except that in a first manufacturing step, the selective etch-stop layer 42A, silicon layer 46, selective etch-stop layer 42B, and cover layer 44 are deposited on a silicon bulk wafer 40 in this order, as shown in the top view of FIG. 5 . The final structure of the membrane 24 is shown in the bottom diagram of FIG. 5 . Here, the actual thickness of the membrane 24 is determined by the other silicon layer 46, and recesses 34 are formed within this silicon layer 46. Most of the bulk wafer 40 is etched away, leaving only sidewalls 41 as a lateral framework supporting the membrane 24 extending therebetween. Again, these frameworks and recesses 34 are obtained by the masking and etching sequence described above. While only two recesses 34 are shown in FIG. 5 , the membrane 24 may, of course, include a much larger number of recesses 34. 4, each recess 34 is again covered by a cover layer 44. Again, the cover layer 44 has through-holes 26 through which the liquid substrate 14 is sprayed into the mouthpiece chamber 28 of the aerosol generating device 10. By using another silicon layer 46 between the two selective etching stopper layers 42A, B, a membrane 24 with a well-defined thickness is obtained. This method therefore allows for more precise control of the membrane thickness.

[0110] Through suitable selection of materials, the membrane structure can be configured to have desired surface properties that may be beneficial to the aerosolization process. In this regard, FIG. 6 illustrates a membrane structure in which another layer of polycrystalline silicon 48 is provided below and directly adjacent to the cover layer 44. In this manner, the surface of the cover layer 44 that contacts the liquid substrate 14 stored in the liquid supply 12 is covered with the layer of polycrystalline silicon 48. Polycrystalline silicon is more hydrophilic compared to single-crystal silicon or silicon nitride, thereby enhancing microfluidic flow through the through-holes 26.

[0111] FIG. 7 illustrates another modification of the membrane structure shown in FIG. 4. The bulk wafer 40, which forms the base substrate of the membrane 24, is patterned with conductive structures 50. Patterning of the membrane material can be performed using any suitable doping method known to those skilled in the art. In the method of FIG. 5, the conductive structures 50 can also be formed during vapor deposition of the material layers forming the membrane 24. As shown in FIG. 7, the conductive structures 50 extend through portions of the membrane material adjacent the recesses 34 and through-holes 26, but are not exposed to the liquid substrate 14 flowing through the membrane 24. Such conductive structures 50 can form built-in resistive heater elements. By passing an electric current through these conductive structures 50, the temperature of the membrane 24 and the aerosolized liquid substrate 14 can be adjusted.

[0112] MEMS technology also allows for the deposition of further functional layers or components on the membrane structure. In this regard, Figure 8 shows yet another modification of the membrane structure described above. The membrane structure incorporates a piezoelectric element 52 formed on an annular contact area 54 of the membrane structure.

[0113] A piezoelectric material, in this case lead zirconate titanate, is deposited on top of the membrane structure during the fabrication process of the membrane 24. As shown in FIG. 8, the piezoelectric material is deposited on annularly extending contact areas 54 located around the periphery of the membrane structure 24. Deposition of the piezoelectric material is performed by a coating technique that includes a masking step to achieve the desired lateral geometry of the piezoelectric elements 52. Forming the piezoelectric elements 52 integrally with the membrane structure 24 simplifies the fabrication of the vibrating mesh module 20 compared to conventional fabrication methods, which require separately provided piezoelectric elements 52 to be glued to the membrane module, a typically tedious and error-prone manufacturing process.

[0114] The membrane structure 25 may further be provided with contacts for electrically connecting the piezoelectric elements 52 to a controller of the aerosol generating device 10. A membrane structure such as that shown in Figure 8, further provided with one or more integrated piezoelectric elements 52 and electrical contacts, may also be referred to as a vibrating mesh module 20. Such a vibrating mesh module 20 may be used in the manufacture of a vibrating mesh aerosol generating device 10. The vibrating mesh module 20 may be manufactured as a replaceable accessory for such an aerosol generating device 10, or may be configured to be replaceable and replaceable by the user themselves.

[0115] FIG. 9 shows the vibrating mesh module 20 of FIG. 8 coupled to an upstream liquid flow chamber 60. The liquid flow chamber 60 is configured to supply the liquid substrate 14 to the inlet face of the membrane structure 24. The liquid flow chamber 60 is in fluid communication with a liquid supply (not shown) of an aerosol generating device. Fluid communication is established through an inlet 62 and an outlet 64, allowing the liquid substrate 14 to circulate freely between the flow chamber 60 and the liquid supply. This configuration ensures that the inlet face of the membrane 24 is always in contact with the liquid substrate 14. This configuration ensures that excess liquid substrate 14 that is not diffused through the perforations is resupplied into the liquid supply. In this configuration, the liquid substrate 14 is not pressed against or forced through the perforations of the membrane 24. This configuration improves the reproducibility of aerosol formation and avoids unwanted leakage of the liquid substrate 14.

Claims

1. 1. A membrane for a vibrating mesh module for use in an aerosol generating device, comprising: the membrane includes a plurality of recesses defining portions of the membrane having reduced thickness; the portion of the membrane having a reduced thickness is provided with one or more through holes defining perforations in the membrane; The membrane further comprising one or more piezoelectric elements integrally formed with the membrane.

2. 2. The membrane of claim 1, wherein the through holes have an aspect ratio of less than 3, preferably less than 1.

3. 3. The membrane according to claim 1, wherein the membrane comprises a perforation density of 10 to 10,000 perforations per square millimeter, preferably 50 to 5,000 perforations per square millimeter.

4. The membrane of any one of claims 1 to 3, wherein the recesses have an aspect ratio of less than 3.

5. The membrane of any one of claims 1 to 4, wherein the membrane comprises multiple layers of material.

6. The membrane of claim 5 , wherein the membrane comprises a bulk layer formed from material provided in the form of a wafer.

7. The membrane of claim 6 , wherein the wafer material is made of silicon, silicon oxide, silicon nitride, aluminum nitride, or a combination thereof.

8. 1. An aerosol generating device comprising a vibrating mesh module for aerosolization of an aerosol-forming substrate, the aerosol generating device comprising: An aerosol generating device, wherein the vibrating mesh module comprises a membrane according to any one of claims 1 to 7.

9. 1. A method of manufacturing a membrane for a vibrating mesh module for use in an aerosol generating device, said 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 on the first surface of the bulk wafer; providing through holes in the cover layer using MEMS fabrication techniques; Etching the second surface of the bulk wafer to define a recess therein; Etching the second surface of the bulk wafer until the bulk wafer material is removed from the recess; and cutting out the membrane; The method, wherein the membrane further comprises one or more piezoelectric elements integrally formed with the membrane.

10. The through hole is masking the cover layer to define the arrangement and dimensions of the through-holes in the membrane to be produced; 10. The method of claim 9, wherein the insulating layer is provided on the cover layer by the steps of: etching the cover layer to form through holes in the cover layer.

11. 1. A membrane for a vibrating mesh module for use in an aerosol generating device, comprising: the membrane is made from a material suitable for MEMS fabrication; A membrane, wherein the membrane comprises a plurality of through holes and the material of the membrane is patterned with conductive structures.

12. The membrane of claim 11 , wherein the conductive structure is configured to penetrate 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. 1. A vibrating mesh module for use in an aerosol generating device, the vibrating mesh module comprising: A vibrating mesh module comprising the membrane according to any one of claims 1 to 7 or 11 to 13, and further comprising one or more piezoelectric elements deposited on the contact surface of the membrane structure.

15. The method comprises:

11. The method of claim 9, further comprising patterning the bulk wafer material with conductive structures.

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