Airflow generating device and method thereof

Abstract

To provide an air flow generating device capable of generating a significant air flow, and a method thereof.SOLUTION: The air flow generating device comprises a first cell or first flap pair 10p and a second cell or second flap pair 20p, wherein the first cell is arranged in a first region Rg1 and generates a first air pressure having a first polarity. The second cell is disposed in the second region Rg2 and generates a second air pressure having a second polarity. The second polarity is opposite to the first polarity.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This application relates to an airflow generating device and method, and more particularly to an airflow generating device and method capable of providing significant airflow. [Background technology]

[0002] Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims of this application, nor are they admitted to be prior art by inclusion in this section.

[0003] Air pulse generating (APG) devices have been developed to generate air pulses. In addition to audio applications, air pulse generating devices may also be used for airflow applications. APG devices fabricated by MEMS (Micro Electro Mechanical Systems) have attracted significant market attention in recent years due to their small size and ability to generate airflow. There is a high market demand for strong airflow to improve performance such as heat dissipation. For microdevices using MEMS fabrication technology, providing strong airflow is a difficult challenge.

[0004] Therefore, it is an object in the art how to design a MEMS device that is capable of providing significant airflow. Summary of the Invention

[0005] Therefore, the main objective of this application is to provide an air flow generating device and method therefor to remedy the shortcomings of the prior art.

[0006] The present invention provides an air flow generating device including a first cell and a second cell, the first cell being disposed in a first region and generating a first air pressure having a first polarity, and the second cell being disposed in a second region and generating a second air pressure having a second polarity, the second polarity being opposite to the first polarity.

[0007] The present invention provides a method for generating an air flow for an air flow generating device, the method comprising: generating a first air pressure having a first polarity in a first region with a first cell; generating a second air pressure having a second polarity in the second region with the second cell; The airflow generating device includes a first cell and a second cell, the second polarity being opposite to the first polarity.

[0008] The present invention provides an air flow generating device, the air flow generating device comprising: a film structure configured to perform a push or pull movement on a volume above the film structure to generate a positive pressure and a negative pressure; a flap pair including a first flap and a second flap opposed to each other, the flap pair configured to perform a differential movement to form a virtual valve; The differential movement performed by the flap pair is synchronized with the movement performed by the membrane structure to create an air flow when the virtual valve is opened.

[0009] These and other objects of the present invention will no doubt become obvious to those skilled in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a top view of an air flow generating device according to an embodiment of the present application; [Figure 2] 1 is a schematic diagram of a cross-sectional view of an air flow generating device according to an embodiment of the present application; [Figure 3] 1 illustrates membrane movement of an air flow generating device according to one embodiment of the present application. [Figure 4] 1 illustrates a drive signal according to one embodiment of the present application. [Figure 5] 1 is a schematic diagram of an air flow generating device according to an embodiment of the present application; [Figure 6] 1 is a schematic diagram of an air flow generating device according to an embodiment of the present application; [Figure 7] 1 is a schematic diagram of an air flow generating device according to an embodiment of the present application; [Figure 8] 1 is a schematic diagram of an appearance of an air flow generating device according to an embodiment of the present application; [Figure 9] 1 is a schematic diagram of an air flow generating device according to an embodiment of the present application; [Figure 10] 1 is a schematic diagram of an air flow generating device according to an embodiment of the present application; [Figure 11]1 is a schematic diagram of an air flow generating device according to an embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0011] The contents of US Pat. No. 12,356,141 are incorporated herein by reference.

[0012] FIG. 1 is a schematic diagram of a top view of an air flow generating device 1 (particularly, a membrane portion) according to an embodiment of the present application. FIG. 2 is a schematic diagram of a cross-section of the air flow generating device 1 (particularly, a membrane portion) according to an embodiment of the present application. FIG. 3 illustrates the movement of a membrane of the air flow generating device 1 (including a covering structure 140) according to an embodiment of the present application. The air flow generating device 1 includes a first cell 10 and a second cell 20. Each of the first cell 10 and the second cell 20 is a MEMS fabricated air pulse generating device, and these air pulse generating devices have a structure similar to that of U.S. Pat. No. 12,356,141. The first cell 10 is disposed in a first region Rg1 (or region 1), and the second cell 20 is disposed in a second region Rg2 (or region 2). As can be seen, the present invention utilizes one or more cells in region 1 and one or more cells in region 2 to create an air pressure difference and produce airflow.

[0013] Specifically, cell 10 / 20 includes a film structure (or membrane) 10f / 20f. In the embodiment shown in Figure 1, membrane structure 10f / 20f includes a flap pair 10p / 20p, which includes a first flap 101 / 201 and a second flap 103 / 203 facing each other.

[0014] The flap pair 10p / 20p may receive a common-mode signal SM1 / SM2 (also known as a modulation driving signal) to perform a (first / second) common-mode movement. The flap pair 10p / 20p may also receive a pair of differential-mode signals ±SV1 / ±SV2 to perform a (first / second) differential-mode movement. In the embodiment shown in FIGS. 1 and 2, the flap pair 10p / 20p simultaneously performs common-mode and differential-mode movements. In fact, the membrane movement of the flap pair 10p / 20p may be considered to be an aggregation / combination of common-mode and differential-mode movements.

[0015] In one embodiment, as shown in FIG. 2, flap pair 10p / 20p receives differential mode signals ±SV1 / ±SV2 via the upper electrodes of the corresponding actuators and common mode signals SM1 / SM2 via the lower electrodes of the corresponding actuators.

[0016] A flap pair 10p / 20p, including opposing flaps 101 / 201 and 103 / 203, performs a first / second differential mode motion relative to a first / second virtual valve 112 / 212. When a displacement difference between the flaps 101 / 201 and 103 / 203 is greater than a flap / membrane thickness, the first / second virtual valve 112 / 212 is considered "open." When a displacement difference between the flaps 101 / 201 and 103 / 203 is less than a flap / membrane thickness, the first / second virtual valve 112 / 212 is considered "closed."

[0017] In one embodiment, the virtual valve is closed during the differential-mode movement is in transition, which means, but is not limited to, during the transition time period of the first and second flaps performing the differential-mode movement, as taught in U.S. Patent No. 12,356,141. In one embodiment, the virtual valve may be in a closed status corresponding to a reversal of flap / membrane movement during differential-mode movement, which is also within the scope of the present invention.

[0018] For the operating principles of each cell, reference may be made to (but is not limited to) US Pat. No. 12,356,141.

[0019] 3 illustrates a covering structure 140 configured to cover the flap pair 10p / 20p. In the covering structure 140, an opening 12 is formed between a first region Rg1 and a second region Rg2, and the opening 12 may have an elongated shape (as shown in FIG. 8). FIG. 1 also illustrates (a projection of) the opening 12 between the first region Rg1 and the second region Rg2.

[0020] FIG. 3 illustrates the movement of the membrane of the air flow generating device 1 at times t1, t2, t3, and t4 according to one embodiment of the present application.

[0021] At time t1, the first cell 10 or first flap pair 10p performs a first common-mode movement upward and a first differential-mode movement to close the first virtual valve 112. The second cell 20 or second flap pair 20p performs a second common-mode movement downward and a second differential-mode movement to open the second virtual valve 212. The first common-mode movement moving upward compresses a first volume in / above the first region Rg1 and generates a positive air pressure P+ in / above the first region Rg1. The second common-mode movement moving downward expands the second volume of the second region Rg2, generating a negative air pressure P− in / above the second region Rg2. The second differential-mode movement opens the second virtual valve 212, allowing airflow AF1 to flow through opening 212 and opening 12 in the +Z direction.

[0022] At time t2, the first cell 10 or first flap pair 10p performs a first common mode motion downward and a first differential mode motion to open the first virtual valve 112. The second cell 20 or second flap pair 20p performs a second common mode motion upward and a second differential mode motion to close the second virtual valve 212. The upward movement of the second common mode motion compresses a second volume in / above the second region Rg2 and generates a positive air pressure P+ in / above the second region Rg2. The downward movement of the first common mode motion expands a first volume in the first region Rg1 and generates a negative air pressure P− in / above the first region Rg1. The first differential mode movement opens the first virtual valve 112, allowing airflow AF2 to flow through opening 112 and opening 12 in the +Z direction.

[0023] At time t3, the first cell 10 or first flap pair 10p performs a first common mode movement upward and a first differential mode movement to close the first virtual valve 112. The second cell 20 or second flap pair 20p performs a second common mode movement downward and a second differential mode movement to open the second virtual valve 212. The upward movement of the first common mode movement compresses a first volume in / above the first region Rg1, generating a positive air pressure P+ in / above the first region Rg1. The downward movement of the second common mode movement expands a second volume in / above the second region Rg2, generating a negative air pressure P− in / above the second region Rg2. The second differential mode movement opens the second virtual valve 212, allowing airflow AF3 to flow through opening 212 and opening 12 in the +Z direction.

[0024] At time t4, the first cell 10 or first flap pair 10p performs a first common mode motion downward and a first differential mode motion to open the first virtual valve 112. The second cell 20 or second flap pair 20p performs a second common mode motion upward and a second differential mode motion to close the second virtual valve 212. The upward movement of the second common mode motion compresses a second volume in / above the second region Rg2 and generates a positive air pressure P+ in / above the second region Rg2. The downward movement of the first common mode motion expands a first volume in the first region Rg1 and generates a negative air pressure P− in / above the first region Rg1. The first differential mode movement opens the first virtual valve 112, allowing airflow AF4 to flow through opening 112 and opening 12 in the +Z direction.

[0025] The movement of the membrane shown in Figure 3 may be achieved by applying (driving) the signals SM1, SM2, ±SV1, ±SV2 shown in Figure 4. For the set of signals (SM1 / SM2, ±SV1 / SV2), reference may be made to U.S. Patent No. 12,356,141. The differential-mode frequency of the differential-mode signals ±SV may be half (or one-quarter) of the common-mode frequency of the common-mode signal SM.

[0026] In the embodiment shown in FIG. 4, the differential mode signals ±SV1 and ±SV2 may have a phase difference of (but is not limited to) π / 4, and the common mode signals SM1 and SM2 may have a phase difference of (but is not limited to) π / 2.

[0027] 5 to 7 illustrate top views of air flow generating devices 1′, 2, 2′, and 3 according to an embodiment of the present invention. For air flow generating devices 1, 1′, 2, and 2′ in which the air flow generating device is divided into only two regions, one or more cells located in region 1 and receiving a first set of signals (SM1, ±SV1) may be considered one or more first cells, and one or more cells located in region 2 and receiving a second set of signals (SM2, ±SV2) may be considered one or more second cells.

[0028] In Figure 5, the slit formed between the opposing first and second flaps in the first cell / second cell of the air flow generating device 1' is perpendicular to the opening 12, which also falls within the scope of the present invention.

[0029] 6, a plurality of first cells may exist in region 1, and a plurality of second cells may exist in region 2. The plurality of first cells / plurality of second cells may be arranged in an array, which also falls within the scope of the present invention.

[0030] 7, cells receiving the first signal set (SM1, ±SV1) may be adjacent to cells receiving the second signal set (SM2, ±SV2) in both a first direction (e.g., X1) and a second direction (e.g., X2) perpendicular to the first direction (e.g., X1). For example, a first cell 10 in a sub-region rg11 of Region 1 is adjacent to a second cell 20 in a sub-region rg21 of Region 2 in the first direction X1, and a first cell 10 in a sub-region rg11 of Region 1 is adjacent to a fourth cell 40 in a sub-region rg22 of Region 2 in the second direction X2 (perpendicular to the first direction X1). Similarly, the third cell 30 in the sub-region rg12 of region 1 is adjacent to the fourth cell 40 in the sub-region rg22 of region 2 in the first direction X1, and the third cell 30 in the sub-region rg12 of region 1 is adjacent to the second cell in the sub-region rg21 of region 2 in the second direction X2.

[0031] In one embodiment, all of the first cells in sub-region rg11 of region 1 and all of the third cells in sub-region rg12 of region 1 receive a first set of signals (SM1, ±SV1), and all of the second cells in sub-region rg21 of region 2 and all of the second / fourth cells in sub-region rg22 of region 2 receive a second set of signals (SM2, ±SV2).

[0032] The opening 12 may be arranged between the region 1 and the region 2. Specifically, the opening 12 may be arranged between the sub-region rg11 of the region 1 and the sub-region rg21 of the region 2, between the sub-region rg11 of the region 1 and the sub-region rg22 of the region 2, between the sub-region rg12 of the region 1 and the sub-region rg22 of the region 2, and / or between the sub-region rg12 of the region 1 and the sub-region rg21 of the region 2.

[0033] It should be noted that Figure 7 is an illustrative diagram: each sub-region (e.g., rg11, rg12, rg21, rg22, etc.) may contain only one cell, and this is also within the scope of the present invention.

[0034] 8 is a schematic diagram of an appearance of an air flow generating device 34 according to an embodiment of the present application. The air flow generating device 34 includes a covering structure 340 (e.g., a lid). Openings 12 are formed in the covering structure 340, and the openings 12 may have elongated shapes. The elongated openings 12 may partition the air flow generating device 34 into sub-regions rg11, rg12, rg21, and rg22 as shown in FIG. 7, and the covering structure 340 may be used to cover the air flow generating device 3 shown in FIG. 7 or may be positioned above the air flow generating device 3 to form the air flow generating device 34.

[0035] An advantage of the present invention is that the airflow (volume) of the present invention may be scaled up simply by incorporating more cells and expanding the arrangement of cells and openings (particularly openings 12) in direction X1 and / or direction X2; the simplicity of such cell incorporation and expansion of the arrangement of cells and openings allows for more flexible design to meet various requirements, is more robust to assembly deformations compared to previous architectures, and makes the array easier to implement.

[0036] Another advantage of the present invention is that the double differential mode (e.g., as shown in airflow generating device 34) may result in less ultrasonic energy leakage and better airflow performance compared to previous designs.

[0037] For example, three configurations are compared in the simulation, where a cell arrangement similar to the airflow generating device 3 is considered. The first configuration is "common mode", where all of the cells receive one common signal set (SM, ±SV) (where the subscripts are ignored). The second configuration is "differential mode", where cells in sub-regions rg11 and rg22 (e.g., cell 10 and cell 40) receive a first set of signals (SM1, ±SV1) and cells in sub-regions rg21 and rg12 (e.g., cell 20 and cell 30) receive a second set of signals (SM2, ±SV2). The final configuration is "double differential mode," in which cells in sub-areas rg11 and rg12 (e.g., cell 10 and cell 30) receive a first set of signals (SM1, ±SV1), and cells in sub-areas rg21 and rg22 (e.g., cell 20 and cell 40) receive a second set of signals (SM2, ±SV2).

[0038] In the simulation, the "common mode," "differential mode," and "dual differential mode" configurations generated airflow (volume velocity) of 45 cc / sec, 54 cc / sec, and 58 cc / sec, respectively. As can be seen, the "differential mode" configuration (corresponding to the present invention) is better than the "common mode" (corresponding to a previous design that may be considered an extension of Patent No. 12,356,141) in terms of airflow or volume velocity performance. Furthermore, the "dual differential mode" configuration is even better than the "differential mode." In other words, it was verified that both the "differential mode" and the "dual differential mode" configurations improved airflow or volume velocity performance over the prior art.

[0039] It should be noted that the embodiments shown above, including but not limited to, have a flap pair performing both common mode and differential mode motion (simultaneously).

[0040] 9 to 11 illustrate air flow generating devices 4 to 6 according to one embodiment of the present application.

[0041] 9, the airflow generating device 4 includes a flap pair 41v, a flap pair 42m, and a flap pair 43v. The flap pair 42m (mainly / exclusively) performs a common-mode motion to push or pull the volume above / below the flap pair 42m, resulting in a positive air pressure P+ and / or a negative air pressure P− (particularly in the illustrated chamber). The flap pair 41v and the flap pair 43v (mainly / exclusively) perform a differential motion. The timing of the common-mode motion of the flap pair 42m and the differential motion of the flap pair 41v and the flap pair 43v are synchronized. Thus, airflow to and from the airflow generating device 4 can be generated.

[0042] In one embodiment, the differential mode frequency may be half / quarter of the common mode frequency, so that the aperture may always occur at higher / lower pressure in the enclosure chamber, leading to one-directional airflow pumping.

[0043] In one embodiment, the chamber surface may be attached to a heat source or fin structure, which may allow the external heat source to heat and blow air through the chamber, dissipating heat from the heat source.

[0044] 10, the airflow generating device 5 includes a flap pair 51v, a flap pair 52m, a flap pair 53m, a flap pair 54m, and a flap pair 55v. The flap pairs 52m, 53m, and 54m (mainly / exclusively) perform common-mode motion to push or pull the volumes above the flap pairs 52m, 53m, and 54m, resulting in a positive air pressure P+ / negative air pressure P-. The flap pairs 51v and 55v (mainly / exclusively) perform differential-mode motion that is synchronous with the common-mode motion.

[0045] The pressure and airflow inside the chamber is similar to a forced swirling system, which serves to increase the equivalent heat convection coefficient of the air inside the chamber and will help to evacuate a higher temperature when the top surface is attached to a heat source.

[0046] 11, the airflow generating device 6 includes a flap pair 61v, a flap pair 62m, a flap pair 63m, and a flap pair 64v. The flap pair 62m and the flap pair 63m (mainly / exclusively) perform a common mode motion to push or pull the volume above the flap pair 62m and the flap pair 63m, resulting in a positive air pressure P+ / a negative air pressure P-. The flap pair 61v and the flap pair 64v (mainly / exclusively) perform a differential mode motion that is synchronous with the common mode motion.

[0047] Using acoustic modes within the chamber, the two push-pull flap pairs 62m and 63m may drive the chamber pressure into acoustic resonance. Controlling the valve open time to synchronize with the ultrasound acoustic pressure difference will generate airflow. Having an even number of flap pairs performing common mode motion (e.g., 62m and 63m) or differential mode motion (e.g., 61v and 64v) can enable energy reuse in the electrical, mechanical, and acoustic domains, which can lead to higher system efficiency.

[0048] Those skilled in the art will readily recognize that various modifications and changes can be made to the device and method while retaining the teachings of the present invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

Claims

1. 1. An air flow generating device, the air flow generating device comprising: a first cell disposed within the first region; a second cell disposed in the second region; the first cell generates a first air pressure having a first polarity in the first region, and the second cell generates a second air pressure having a second polarity in the second region; the second polarity is opposite to the first polarity; Air flow generating device.

2. the first cell includes a first membrane structure, and the second cell includes a second membrane structure; The first membrane structure moves in a first direction, and the second membrane structure moves in a second direction opposite to the first direction.

10. The air flow generating device of claim 1.

3. the first cell includes a first pair of flaps, and the second cell includes a second pair of flaps; At least one of the first pair of flaps and the second pair of flaps includes a first flap and a second flap that face each other.

10. The air flow generating device of claim 1.

4. the first pair of flaps performing a first common mode motion and the second pair of flaps performing a second common mode motion; the first pair of flaps performing the first common mode motion to move in a first direction, and the second pair of flaps performing the second common mode motion to move in a second direction opposite the first direction; 4. An air flow generating device according to claim 3.

5. the first pair of flaps performing a first differential mode motion to form a first virtual valve; the second pair of flaps performing a second differential mode motion to form a second virtual valve; When the first virtual valve is in an open state, the second virtual valve is in a closed state.

4. An air flow generating device according to claim 3.

6. the first pair of flaps performing a first common mode motion and a first differential mode motion to form a first virtual valve; the second pair of flaps performing a second common mode motion and a second differential mode motion to form a second virtual valve; the second virtual valve is in an open state when the first pair of flaps executes the first common mode motion and moves in a first direction, thereby compressing a volume above the first pair of flaps.

4. An air flow generating device according to claim 3.

7. At least one of the first cell and the second cell includes a flap pair; the pair of flaps undergoing common mode motion to compress or expand a volume above the pair of flaps; the pair of flaps perform differential mode motion to form a virtual valve; the pair of flaps simultaneously performing the common mode motion and the differential mode motion; 10. The air flow generating device of claim 1.

8. the virtual valve is closed while the common mode motion of the flap pair moves toward a first direction; the virtual valve is opened while the common mode motion of the flap pair moves toward a second direction opposite the first direction; 8. An air flow generating device according to claim 7.

9. the virtual valve is closed at a transition of the differential mode motion of the first flap and the second flap; 8. An air flow generating device according to claim 7.

10. the first cell includes a first pair of flaps, and the second cell includes a second pair of flaps; the first pair of flaps compresses a first volume over the first region, and a first virtual valve formed by the first pair of flaps is closed; the second pair of flaps extends a second volume over the second region, and a second virtual valve formed by the second pair of flaps is opened.

10. The air flow generating device of claim 1.

11. At least one of the first cell and the second cell includes a flap pair; the flap pair receives a pair of differential mode and common mode signals; 10. The air flow generating device of claim 1.

12. the pair of flaps receiving the pair of differential mode signals corresponding to a differential mode frequency and a common mode signal corresponding to a common mode frequency; the differential mode frequency is half or a quarter of the common mode frequency; 12. An air flow generating device according to claim 11.

13. the first cell includes a first pair of flaps, and the second cell includes a second pair of flaps; the first pair of flaps receives a first differential mode signal, and the second pair of flaps receives a second differential mode signal; the first differential mode signal and the second differential mode signal have a phase difference of π / 4; 10. The air flow generating device of claim 1.

14. the first cell includes a first pair of flaps, and the second cell includes a second pair of flaps; the first pair of flaps receives a first common mode signal, and the second pair of flaps receives a second common mode signal; the first common mode signal and the second common mode signal have a phase difference of π / 2; 10. The air flow generating device of claim 1.

15. a plurality of first cells disposed within the first region; a plurality of second cells disposed within the second region; 10. The air flow generating device of claim 1.

16. a covering structure disposed over the first cell and the second cell; 10. The air flow generating device of claim 1.

17. an opening is formed between the first region and the second region; 17. An air flow generating device according to claim 16.

18. The opening has an elongated shape.

18. An air flow generating device according to claim 17.

19. a third cell and a fourth cell; the first cell is disposed in a first sub-region of the first region; the second cell is disposed in a first sub-region of the second region; the third cell is disposed in a second sub-region of the first region; the fourth cell is disposed in a second sub-region of the second region; the first sub-region of the first region is adjacent to the first sub-region of the second region in a first direction; the first sub-region of the first region is adjacent to the second sub-region of the second region in a second direction; the first cell and the third cell generate the first air pressure having the first polarity in the first region; the second cell and the fourth cell generate the second air pressure having the second polarity in the second region; 10. The air flow generating device of claim 1.

20. the first cell and the third cell receive a first differential mode signal and a first common mode signal; the second cell and the fourth cell receive a second differential mode signal and a second common mode signal; 20. An air flow generating device according to claim 19.

21. the first differential mode signal and the second differential mode signal have a phase difference of π / 4; the first common mode signal and the second common mode signal have a phase difference of π / 2; 21. An air flow generating device according to claim 20.

22. a covering structure disposed over the first cell, the second cell, the third cell, and the fourth cell; 20. An air flow generating device according to claim 19.

23. a first opening is formed between the first sub-region of the first region and the first sub-region of the second region; a second opening is formed between the first sub-region of the first region and the second sub-region of the second region; 23. An air flow generating device according to claim 22.

24. a plurality of first cells disposed within the first sub-region of the first region; a plurality of second cells disposed within the first sub-region of the second region; a plurality of third cells disposed within the second sub-region of the first region; a plurality of fourth cells disposed within the second sub-region of the second region; the first cell and the third cell generate the first air pressure having the first polarity in the first region; the second cell and the fourth cell generate the second air pressure having the second polarity in the second region; 20. An air flow generating device according to claim 19.

25. 1. A method of generating an air flow for an air flow generating device, the method comprising: generating a first air pressure having a first polarity in a first region with a first cell; generating a second air pressure having a second polarity in the second region with the second cell; the airflow generating device includes the first cell and the second cell; the second polarity is opposite to the first polarity; method.

26. compressing a first volume of the first region with the first cell; and expanding a second volume of the second region with the second cells.

26. The method of claim 25.

27. actuating a first membrane structure to move towards a first direction; and actuating the second membrane structure to move toward a second direction opposite the first direction; the first cell includes the first membrane structure, and the second cell includes the second membrane structure; 26. The method of claim 25.

28. performing a first common mode motion in a first direction with a first pair of flaps; performing a second common mode motion with a second pair of flaps in a second direction opposite the first direction; the first cell includes the first pair of flaps, and the second cell includes the second pair of flaps; 26. The method of claim 25.

29. actuating a first pair of flaps with a first differential mode signal and a first common mode signal; actuating a second pair of flaps with a second differential mode signal and a second common mode signal; the first differential mode signal and the second differential mode signal have a phase difference of π / 4; the first common mode signal and the second common mode signal have a phase difference of π / 2; 26. The method of claim 25.

30. 1. An air flow generating device, the air flow generating device comprising: a membrane structure configured to perform a pushing or pulling motion on a volume above the membrane structure to generate positive and negative pressures; a flap pair including a first flap and a second flap opposed to each other, the flap pair configured to perform differential motion to form a virtual valve; the differential movement performed by the pair of flaps is synchronized with the movement performed by the membrane structure; When the virtual valve is opened, an air flow is created. Air flow generating device.

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