Device, air filter element, and method for mechanical cleaning of pathogens

Abstract

Microelectromechanical device (2) for mechanical cleaning of pathogens, comprising • a body ( 6 ); • an actuatable membrane (10) arranged on said body (6); • an actuating element (60) arranged at an actuating side (20) of said membrane (10) for actuating the membrane; whereby on an active side (18) of said membrane (10) the membrane (10) comprises a surface structure with pillars (158) in the nanometer-micrometer range.

Description

[0001] 2022PF1403 - 1 - DEVICE, AIR FILTER ELEMENT, AND METHOD FOR MECHANICAL CLEANING OF PATHOGENS DESCRIPTION The purification of gases (air) and liquids (water) from compounds that are harmful to the human body has become an increasingly important task. The most critical compounds are, on the one hand, pathogens such as bacteria and viruses and, on the other hand, substances harmful to the human body such as volatile organic compounds (VOCs) as well as ammonia ammonia, NOx, Sox. The task in these purification efforts is to eliminate the pathogens as efficiently / quickly as possible. Bacteria and viruses are typically attempted to be rendered harmless by means of UVC irradiation. A common method to destroy pathogens, especially bacteria, is the irradiation with direct UV radiation, leading to genetic damage of the pathogens which prevents them from infecting and replicating and leads to cell inactivation. Irradiation with UV radiation has also been combined with photocatalysis. Another common method is to use photoexcitation, whereby carbon-based nanomaterials can function as photosensitizers to kill bacterial cells through photo-dependent ROS production. Alternatively, photoexcited carbon-based nanomaterials can decay back to the ground state by emitting fluorescence or through nonradiative relaxation pathways to generate a photothermal effect. Technical solutions according to the state of the art are based on the use of one, maximum of two of these active principles simultaneously. 2022PF1403 - 2 - The disadvantage of UVC-based pathogen removal is the high level of safety measures to prevent UVC radiation from escaping. Exposure of users to UVC must be prevented. Photothermal effect requires the deposition of very specific materials and leads to heating which is not always unproblematic in terms of aging. The object of the invention is to provide a device, a manufacturing method for the device, an air filter element and a method for effective cleaning of pathogens in an air stream. With respect to the device, this object is solved by a microelectromechanical device with the features of claim 1. This microelectromechanical device comprises a body, an actuatable membrane arranged on this body, and an actuating element arranged at an actuating side of the membrane for actuating the membrane. On an active side of the membrane, the membrane comprises a surface structure with pillars in the nanometer-micrometer range. The invention is based on the basic idea to utilize the physical and mechanical mechanism of action used by cycads against bacteria on demand. To destroy bacteria, the cycad has surface structures in the nanometer range on its wings. These are "beaten onto the bacteria" with each wing beat. The relative speed plus the surface properties of the wing structures lead to a "rupture" of the bacteria cell / membrane and thus to an inactivation of the bacteria. inactivation of the bacteria. Applicant has found that this concept can be made usable for air filter systems by employing a defined controllable / movable membrane which is equipped with a suitable surface structure. Due to the continuous oscillation of the silicon membrane at a high frequency, high relative velocities between the membrane surface and the bacteria are achieved. In this way, a large number of impact events of the membrane surface and the bacteria is achieved. Applicant has 2022PF1403 - 3 - recognized that, for example, silicon-based MEM Sloudspeakers which are modified such that the side facing the air flow has a nanopillar structure are suitable for destroying the bacteria. The principle of the current invention therefore is the generation of a high impact velocity of germs on surface structures and subsequent decomposition by means of moving membrane surfaces. The described microelectromechanical device is built as MEMS (microelectromechanical system). The term “pillars in the nanometer-micrometer range” especially denotes pillars which have a width / diameter and / or height which lies between 100 nm and 5 µm. Advantageously, the surface structure of the membrane comprises an array of pillars. The array preferably has a spatial expansion in the low single-digit mm² range. The pillars are preferably built as pointed structures (pyramids, cones). The resulting shapes are typically defined by the manufacturing process. Grey scale lithography offers the greatest flexibility, but other common processes are also conceivable. However, limitations in the manufacturing process can also lead to "blunt" variants such as blunt cone, blunt pyramid. In a first preferred embodiment, the pillars have a height between 100 nm and 500 nm and a width between 50 nm and 500 nm and a pitch corresponding to height / pitch ration between 0.5 and 30. In a second preferred embodiment, the pillars have a height between 500 nm to 5 µm and a width between 50 nm and 4 µm and a pitch corresponding to height / pitch ration between 0.5 and 2022PF1403 - 4 - When the pillars have a cross section and / or base corresponding to a circle, the width of the respective pillar corresponds to its diameter. The width generally corresponds to the largest extension of the pillar in a with direction. For example, for a rectangle cross section, the width corresponds to its larger side length. The preferred size of the structures depends on the pathogens to be destroyed. Viruses are orders of magnitude smaller than bacteria and have different structural properties. Therefore, smaller structures are likely to be more advantageous for viruses, whereas bacteria are more likely to be sufficiently destroyed by the µm structures. Bacteria require longer structures to penetrate the bacterial envelope. Preferably, laterally in the membrane at least one perforated region is built. Advantageously, the membrane is framed / encompassed by a perforated region. The perforation of the membrane in the edge area minimizes the flow resistance and increases the probability of pathogens hitting the moving membrane. In a preferred embodiment, the actuating element is built as a piezoelectric layer arranged on the actuating side of the membrane. In this way, a piezoelectric transducer can be realized. In a further preferred embodiment, the actuating element is built as or is part of an electrostatic transducer In a further preferred embodiment, actuating element is built or is part of an electrodynamic transducer. In a further preferred embodiment, the actuating element is built or is part of a thermoacoustic transducer. The membrane of the microelectromechanical device described above is built to vibrate with high frequencies. It preferably comprises a thickness between 0.5 µm and 20 µm. 2022PF1403 - 5 - In a further aspect, the invention relates to a system of microelectromechanical device described above and a driving unit for actuating the actuating element. The driving unit can for example, be built as a voltage source. With respect to the air filter element, the object is solved by an air filter element with the features of claim 10. The air filter element comprises an entrance region for air to be filtered and an exit region. It further comprises at least one microelectromechanical device described above arranged in an air-flow path between the entrance region and the exit region. In a preferred embodiment, the air filter element comprises a plurality of microelectromechanical devices arranged in an array. Preferably, between 10 and 300 microelectromechanical devices are provided. In a further preferred embodiment, between the entrance region and the exit region, an air channel is built in such way that the air flowing from the entrance region to the exit region passes sequentially a plurality of microelectromechanical devices. The air channel especially can be built in a zig-zag way built between a housing of the air filter element and the microelectromechanical devices. The microelectromechanical devices are preferably arranged in several groups. These groups together with the housing preferably define the air channel which preferably is built in a zig-zag manner. The described air filter element allows the generation of a high impact velocity of germs on surface structures and subsequent decomposition by accelerating a volume flow onto a target of suitable surface quality. With respect to the manufacturing method, the object is solved by the following steps: 2022PF1403 - 6 - a) providing a body; b) forming a membrane in the body; c) on an actuating side of the membrane, providing an actuating element; d) structuring the membrane to provide an array of pillars in the micrometer-nanometer range. The body is preferably made of silicon. It advantageously comprises a first and a second silicon layer, whereby an insulating layer is sandwiched between these two silicon layers. Preferably at the edges of the membrane, perforated regions are built. With respect to the method for mechanical cleaning pathogens in an air stream, a membrane comprising a structured surface with an array of pillars in the micrometer-nanometer range is vibrated at a high frequency. The high frequency preferably lies in the range between 100 Hz and 200 kHz. The concrete voltages can, dependent on the concrete realization of the microelectromechanical device 2, typically range from a few V (2 V) to about 200 kHz. The frequencies of the vibrations typically range from 100 Hz to 200 kHz. The advantages of the invention are especially as follows. The disclosed invention opens up the utilization of an additional attack scheme on germs and allows a physical / mechanical destruction to be implemented in filter systems. Mechanical cleaning is very efficient because the relative speed between germs and the destroying membrane is high. The filter element disclosed can be integrated as an additional low-maintenance / maintenance-free filter stage and can therefore replace / supplement more maintenance- 2022PF1403 - 7 - intensive elements (activated carbon filter, …). This increases the service life before maintenance. The proposed concept of the invention scalable. A preferred embodiment of the invention is described in connection with a drawing. In this drawing: FIG. 1 shows a microelectromechanical device in a preferred embodiment; FIG. 2 shows a microelectromechanical device in a further preferred embodiment; FIG. 3 shows an air filter element with a plurality of microelectromechanical devices in a first preferred embodiment; FIG. 4 shows a microelectromechanical device of the air filter element according to FIG. 3; FIG. 5 shows an air filter element with a plurality of microelectromechanical devices in a second preferred embodiment; FIG. 6 shows a microelectromechanical device of the air filter element according to FIG. 5; FIGs. 7-14 show steps of a manufacturing method for a microelectromechanical device. Identical parts are labelled with same reference numerals in all FIGs. In FIG. 1, a microelectromechanical device 2 in a preferred embodiment is shown. The microelectromechanical device 2 comprises a body 6 made of a first silicon layer 100, a second silicon layer 106 and an insulating layer sandwiched partly between these two silicon layers 100, 106. 2022PF1403 - 8 - The microelectromechanical device 2 comprises an actuatable membrane 10 which on an active side 18, i.e., the side on which pathogens impinge and are destroyed, comprises an array 154 of pillars. In edge areas of membrane 10, perforated regions 14 are built which allow air to flow through. By providing sufficient perforation in the perforated regions 14 at the edges of the membrane, the flow resistance is minimized and the probability of pathogens hitting the moving membrane 10 is increased. The microelectromechanical device 2 shown in FIG. 1 is based on the principle of electrostatic actuation. To this end, a K+ doped SiO2layer 160, which functions as an actuating element 60, is arranged on membrane 10 on an actuation side 20 opposite to active side 18 of membrane 10. Opposite to the K+ doped layer 160, two K+ electrets 164 are arranged. A voltage source 24 for alternating current is connected to both silicon layers 100, 106. When voltage is applied, the membrane 10 conducts high-frequency vibrations. The concrete voltages can, dependent on the concrete realization of the microelectromechanical device 2, typically range from a few V to about 200 kHz. The frequencies of the vibrations typically range from 100 Hz to 200 kHz. In an enlarged view 28 in FIG. 1, the pillars 158 of the array of pillars 154 are shown with their height, width and pitch, i.e., distance, indicated. The pillars 158 in a first configuration can have a height h between 100 nm and 500 nm and a diameter or width w between 50 nm and 500 nm and a pitch p corresponding to height / pitch ration between 0.5 and 30. In a second configuration with larger pillars 158, the pillars 158 have a height h between 500 nm to 1 µm and a diameter or width w between 50 nm and 4 µm and a pitch p corresponding to height / pitch ration between 0.5 and 30. 2022PF1403 - 9 - A microelectromechanical device 2 in a second preferred embodiment is shown in FIG. 2. It comprises a body 6 comprising a second silicon layer 106 and an insulation layer 108 arranged on second silicon layer 106. Second silicon layer 106 comprises on an active side 18 a structured region in which a membrane 10 is built. The membrane 10 comprises an array 154 of pillars in the micrometer-nanometer range as in the preferred embodiment shown in FIG. 1. On an actuation side 20 of membrane 10, several layers are arranged. Starting from membrane 10, on actuation side 20 an insulation layer 188, a first electrode layer 124, a piezoelectric layer 128, an insulating layer 134, and a second electrode layer 138 are arranged. The piezoelectric layer is the actuating element 60. When the piezoelectric layer 128 is activated, i.e., connected to a voltage source, the membrane 10 conducts high- frequency vibrations. In FIG. 3, an air filter element 30 in a preferred embodiment is shown. The air filter element 30 comprises an entrance region 62 for air to enter and an exit region 64 from which the filtered air leaves the air filter element. The air filter element 30 comprises an array of microelectromechanical devices 2. Such an array of microelectromechanical devices 2 can for example comprise microelectromechanical devices 2 arranged in a square or rectangular grid. Typical arrays can have the shape from 2x2 to 5x5. The incoming air stream, i.e., the air which enters air filter element 30 and which contains pathogens, and the outgoing air stream, i.e., the air in which pathogens have been destroyed, are indicated by big arrows 34. The air flow through perforated regions 14 of the respective membrane 10 is indicated by small arrows 34. The microelectromechanical devices 2 of air filter element 30 of which one is surrounded 2022PF1403 - 10 - in a dashed box 46 are built as the preferred embodiment shown in FIG. 4. Other preferred embodiments, such as shown in FIG. 2 or based on other transduction principles can also be arranged in the air filter element 30. The preferred embodiment of the microelectromechanical device 2 shown in FIG. 4 is built similarly to the microelectromechanical device 2 of FIG. 1. The orientation of membrane 10, however, is reversed. In this embodiment, the destructive structures are on the side of the dynamic pressure. If the air flows through the element from the "rear" / lower side, the effective cross-section is increased with the structured array. In FIG. 5, an air filter element 30 in a further preferred embodiment is shown which comprises four groups 38, 40, 42, 44 of microelectromechanical devices 2. Between a housing 70 and / or the groups 38, 40, 42, 44 of microelectromechanical devices 2, an air channel 68 in a zig-zag path for the air stream which enters the air filter element 30 in entrance region 62 and leaves the air filter element 30 in exit region 64 is provided. Groups 38 and 44 which are arranged at the entrance or exit of the air filter element 30 comprise, respectively, a row of microelectromechanical devices 2. Groups 40 and 42 comprise, respectively, two rows of microelectromechanical devices 2 which are oriented with respect to each other in such a way that the arrays of pillars 154 face away from a center line of these groups. In this way it is assured that the air stream hits as many pillars 158 as possible, thereby destroying pathogens which impinge on the pillars 158. A microelectromechanical device 2 of air filter element 30 of FIG. 5 which is surrounded by a dashed box 48 is shown in FIG. 6. Also seen are channels 50, 54 for electric cables. In FIGS 7-14, steps of a method for manufacturing a microelectromechanical device in a preferred embodiment are described. 2022PF1403 - 11 - In a first step shown in FIG. 7, a first silicon layer 100 and a second silicon layer 106, between which an insulating layer 108 made of SiO2is sandwiched, are provided. In a second step shown in FIG. 8, the second silicon layer 106 is structured by removing silicon material, leading to a recessed region 114 of the second silicon layer. In a third step shown in FIG. 9, an insulated layer 118 is structurally deposited in the recessed region 144 and a first electrode layer 124 is structurally deposited on the insulated layer 118. In a fourth step shown in FIG. 10, a piezoelectric layer 128 is structurally deposited on the first electrode layer 124. In a fifth step shown in FIG. 11, an insulating layer 134 is structurally deposited laterally to the piezoelectric layer 128, and a second electrode layer 138 is structurally deposited on the piezoelectric layer 128. In a sixth step shown in FIG. 12, an opening 144 is formed in the first silicon layer 100. The opening 144 has a rectangular cross section. In a seventh step shown in FIG. 13, the insulating layer 108 is removed in the opening 144. In this way, a part 148 of second silicon layer 106 is exposed in the opening 144. After this removal, the part of the second silicon layer 106 in opening 144 is structured, resulting in a membrane 10 which is designed to conduct high-frequency vibrations. An array of pillars 154 on the nanometer scale is provided in membrane 10. In an eighth step shown in FIG. 14, the first silicon layer 100 is removed to expose the active region containing the array of pillars 154. 2022PF1403 - 12 - Several preferred embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

[0002] 2022PF1403 - 13 - LIST OF REFERENCE SIGNS 2 microelectromechanical device 6 body 10 membrane 14 perforated region 18 active side 20 actuation side 24 voltage source 28 enlarged view 30 air filter element 34 big arrow 36 small arrow 38 group 40 group 42 group 44 group 46 dashed box 48 dashed box 50 channel 54 channel 60 actuating element 62 entrance region 64 exit region 68 air channel 70 housing 100 first silicon layer 106 second silicon layer 108 insulating layer 114 recessed region 118 insulating layer 124 first electrode layer 128 piezoelectric layer 134 insulating layer 138 second electrode layer 144 opening 148 part 154 array of pillars 2022PF1403 - 14 - 158 pillars 160 K+ doped SiO2layer 164 K+ electret w width h height p pitch

Claims

2022PF1403 - 15 - CLAIMS 1. Microelectromechanical device (2) for mechanical cleaning of pathogens, comprising ^ a body (6); ^ an actuatable membrane (10) arranged on said body (6); ^ an actuating element (60) arranged at an actuating side (20) of said membrane (10) for actuating the membrane; whereby on an active side (18) of said membrane (10) the membrane (10) comprises a surface structure with pillars (158) in the nanometer-micrometer range.

2. Microelectromechanical device (2) according to claim 1, whereby said surface structure comprises an array (154) of pillars.

3. Microelectromechanical device (2) according to claim 2, whereby said pillars (158) have a height (h) between 100 nm and 500 nm and a width (w) between 50 nm and 500 nm and a pitch (p) corresponding to height / pitch ration between 0.5 and 30.

4. Microelectromechanical device (2) according to claim 2, whereby said pillars (158) have a height (h) between 500 nm to 5 µm and a width (w) between 50 nm and 4 µm and a pitch (p) corresponding to height / pitch ration between 0.5 and 30.

5. Microelectromechanical device (2) according to one of the claims 1 to 4, whereby laterally in said membrane (10) at least one perforated region (14) is built.

6. Microelectromechanical device (2) according to one of the claims 1 to 5, whereby said actuating element (60) is built as a piezoelectric layer (128) arranged on said actuating side (20) of said membrane (10).

7. Microelectromechanical device (2) according to one of the claims 1 to 5, whereby said actuating element (60) is built or is part of an electrostatic transducer.2022PF1403 - 16 - 8. Microelectromechanical device (2) according to one of the claims 1 to 5, whereby said actuating element (60) is built or is part of an electrodynamic transducer.

9. Microelectromechanical device (2) according to one of the claims 1 to 5, whereby said actuating element (60) is built or is part of a thermoacoustic transducer.

10. Air filter element (30), comprising an entrance region (62) for air to be filtered and an exit region (64), and comprising at least one microelectromechanical device (2) according to one of the claims 1 to 9 arranged in an air-flow path between said entrance region (62) and said exit region (64).

11. Air filter element (30) according to claim 10, comprising a plurality of microelectromechanical device (2) is arranged in an array.

12. Air filter element (30) according to claim 10, whereby between said entrance region (62) and said exit region (64), an air channel (68) is built in such way that the air flowing from the entrance region (62) to the exit region (64) passes sequentially a plurality of microelectromechanical devices (2).

13. Air filter element (30) according to claim 12, whereby said microelectromechanical devices (2) are arranged in several groups (38, 40, 42, 44).

14. Method for manufacturing a microelectromechanical device (2) for mechanical cleaning of pathogens with the following steps: a) providing a body (6); b) forming a membrane (10) in said body (10); c) on an actuating side (20) of said membrane (10), providing an actuating element (60);2022PF1403 - 17 - d) structuring said membrane (10) to provide an array of pillars (154) in the micrometer-nanometer range.

15. Method according to claim 14, whereby at the edges of said membrane (10), perforated regions (14) are built.

16. Method for mechanical cleaning pathogens in an air stream, whereby a membrane (10) comprising a structured surface with an array of pillars (154) in the micrometer- nanometer range is vibrated at a high frequency.

17. Method according to claim 15, whereby said high frequency lies in the range between 100 Hz and 200 kHz.

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