Fluid equipment

Abstract

The present invention discloses a fluid device capable of easily generating a standing wave with a large sound power in a flow path. The fluid device (10) includes: a flow path (20) through which a fluid (S) flows; a pressure chamber (51) formed at an interval from the flow path (20) in a first direction (Y direction) orthogonal to the flow direction of the fluid (S) in the flow path (20); a communication path (52) formed along the Y direction and communicating the flow path (20) with the pressure chamber (51); and an ultrasonic wave transmitting unit (40) that transmits ultrasonic waves to the fluid (S) by contacting the fluid (S) flowing into the pressure chamber (51), thereby generating a standing wave (SW) along the Y direction in the flow path (20).

Description

Technical Field

[0001] The present invention relates to a fluid device. Background Art

[0002] Conventionally, a fluid device that acoustically focuses microparticles in a fluid has been known.

[0003] For example, the fluid device disclosed in Non-Patent Document 1 includes: a flow path substrate (glass substrate) in which a flow path is formed; and a piezoelectric element provided on the flow path substrate. Ultrasonic waves generated by the piezoelectric element are transmitted into the flow path via the flow path substrate, causing standing waves to be generated in the fluid in the flow path. Microparticles in the fluid converge within a specified range in the flow path due to the pressure gradient of the fluid formed by the standing waves.

[0004] Prior Art Documents

[0005] Non-Patent Documents

[0006] Non-Patent Document 1: Nobutoshi Ota, et al. 6 others, "Enhancement in acoustic focusing of micro and nanoparticles by thinning a microfluidic device", December 2019, Royal Society Open Science, Vol. 6, No. 2, Report No. 181776 Summary of the Invention

[0007] However, in the fluid device described in Non-Patent Document 1 above, the difference in acoustic impedance between the fluid and the flow path substrate is large. Therefore, when ultrasonic waves generated by the piezoelectric element propagate from the flow path substrate to the fluid, most of the ultrasonic waves are reflected at the boundary between the flow path substrate and the fluid. As a result, it is difficult to generate standing waves with a large acoustic power in the flow path. Consequently, it is necessary to increase the drive voltage and drive frequency applied to the piezoelectric element.

[0008] The fluid device of the present disclosure includes: a first flow path through which a fluid flows; a pressure chamber formed at an interval from the first flow path in a first direction orthogonal to the flow direction of the fluid in the first flow path; a first communication path formed along the first direction and communicating the first flow path with the pressure chamber; and an ultrasonic wave transmitting unit that transmits ultrasonic waves to the fluid flowing into the pressure chamber by contacting the fluid, thereby generating a first standing wave in the fluid in the first flow path along the first direction. Brief Description of the Drawings

[0009] Figure 1It is a cross-sectional view schematically showing a part of the fluid device of the first embodiment.

[0010] Figure 2 It is Figure 1 a sectional view taken along line A-A of

[0011] Figure 3 It is a cross-sectional view schematically showing the fluid device of the comparative example.

[0012] Figure 4 It is a cross-sectional view schematically showing a part of the fluid device of the second embodiment.

[0013] Figure 5 It is Figure 4 a sectional view taken along line B-B of

[0014] Figure 6 It is a cross-sectional view schematically showing a part of the fluid device of the third embodiment.

[0015] Figure 7 It is a cross-sectional view schematically showing a part of the fluid device of the fourth embodiment.

[0016] Figure 8 It is a cross-sectional view schematically showing a part of the fluid device of the modified example.

[0017] Explanation of reference numerals

[0018] 10, 10A, 10B, 10C, 10D, 10E... fluid devices, 20... flow path, 20A, 20C... first flow paths, 20B, 20D... second flow paths, 30... flow path substrate, 31... upper side wall portion, 32... lower side wall portion, 33... side wall portion, 311, 331... through holes, 34... side wall portion, 40, 40A... ultrasonic transmission portions, 41... element substrate, 411... opening portion, 42... vibration film, 421... vibration portion, 422... fluid contact surface, 43... piezoelectric element, 44... ultrasonic element, 51... pressure chamber, 52... communication path, 52A, 52C... first communication paths, 52B, 52D... second communication paths, A... antinode, H... flow path depth, L... flow path width, M... fine particles, N... node, RA... antinode region, RN... node region, S... fluid, SW... standing wave, t... thickness, W... dimension. Detailed description of the embodiments

[0019] [First Embodiment]

[0020] Hereinafter, with reference to Figure 1 and Figure 2 the fluid device 10 of the first embodiment will be described.

[0021] Figure 1is a cross-sectional view schematically showing a part of the fluid device 10 of the first embodiment, Figure 2 is Figure 1 a cross-sectional view taken along line A-A of

[0022] The fluid device 10 includes a flow path substrate 30 having a flow path 20 and the like formed therein, and an ultrasonic transmission unit 40 provided on the flow path substrate 30.

[0023] In this fluid device 10, the ultrasonic transmission unit 40 applies ultrasonic waves to the fluid S flowing in the flow path 20, thereby generating standing waves SW of an arbitrary mode number in one direction orthogonal to the flow direction of the fluid S. The fine particles M dispersed in the fluid S are affected by the pressure gradient formed by the standing waves SW during the flow in the flow path 20, and converge within a specified range in the flow path 20.

[0024] In such a fluid device 10, for example, by providing a concentration flow path for selectively flowing the fluid S in the range where the fine particles M in the flow path 20 converge and a discharge flow path for selectively flowing the fluid S in the other ranges, the concentration of the fine particles M in the fluid S can be concentrated.

[0025] It should be noted that in Figure 1 , a case where the fine particles M are converged by the standing waves SW of the first mode is schematically illustrated. In addition, in Figure 2 , the illustration of the fine particles M is omitted, and the standing waves SW generated in the flow path 20 are shown as pressure waveforms.

[0026] [Structure of Fluid Device 10]

[0027] Refer to Figure 1 and Figure 2 to describe the simple structure of the fluid device 10.

[0028] The flow path substrate 30 is a substrate having a flow path 20 (first flow path), a pressure chamber 51, and a communication path 52 (first communication path) formed therein. This flow path substrate 30 can be manufactured, for example, by joining a pair of substrates having groove portions corresponding to the flow path 20, the pressure chamber 51, and the communication path 52. Each substrate constituting the flow path substrate 30 is not particularly limited, and for example, a glass substrate or a silicon substrate can be used.

[0029] It should be noted that although not shown, an injection port for injecting the fluid S into the flow path 20 and one or more discharge ports for discharging the fluid S from the flow path 20 are provided on the flow path substrate 30.

[0030] In the present embodiment, the cross-section of the flow path 20 formed in the flow path substrate 30 is rectangular, and the depth direction of the flow path 20 coincides with the thickness direction of the flow path substrate 30. Further, the flow direction of the fluid S flowing in the flow path 20 is orthogonal to the depth direction of the flow path 20, and the width direction of the flow path 20 is orthogonal to the depth direction of the flow path 20 and the flow direction of the fluid S, respectively.

[0031] Hereinafter, the flow direction of the fluid S is defined as the X direction, the width direction of the flow path 20 is defined as the Y direction, and the depth direction of the flow path 20 is defined as the Z direction. The X, Y, and Z directions are orthogonal to each other.

[0032] The flow path substrate 30 includes: an upper side wall portion 31 that forms a wall portion of the flow path 20 on one side in the Z direction; a lower side wall portion 32 that forms a wall portion of the flow path 20 on the other side in the Z direction; and side wall portions 33, 34 that form wall portions of the flow path 20 on both sides in the Y direction.

[0033] The pressure chamber 51 is a storage chamber for the fluid S formed in the flow path substrate 30, and is formed at an interval from the flow path 20 in the Y direction. In the present embodiment, the pressure chamber 51 is formed inside the side wall portion 33 on the Y direction side of the flow path 20, but may also be formed in the side wall portion 34 on the other side in the Y direction.

[0034] The communication path 52 is formed inside the side wall portion 33 of the flow path substrate 30, and is a flow path that connects the pressure chamber 51 and the flow path 20. The communication path 52 is formed along the Y direction and is connected to the side portion of the flow path 20.

[0035] The flow path 20 is connected to the pressure chamber 51 via the communication path 52, and the fluid S flowing in the flow path 20 flows into the pressure chamber 51. The pressure chamber 51 is filled with the fluid S.

[0036] In the present embodiment, in the side wall portion 33 of the flow path substrate 30, a through hole 331 is provided that penetrates a portion of the wall portion that becomes the pressure chamber 51 in the Y direction.

[0037] The ultrasonic transmitting portion 40 is provided on the flow path substrate 30 so as to block the through hole 331, thereby forming a part of the wall portion of the pressure chamber 51.

[0038] The ultrasonic transmitting portion 40 includes: an element substrate 41; a diaphragm 42 supported by the element substrate 41; and a piezoelectric element 43 provided on the diaphragm 42.

[0039] The element substrate 41 is made of a semiconductor substrate such as Si. In the present embodiment, the element substrate 41 is arranged in the through hole 331 of the flow path substrate 30 such that the thickness direction of the element substrate 41 is along the Y direction, and the outer peripheral surface of the element substrate 41 is in liquid-tight contact with the inner peripheral surface of the through hole 331 of the flow path substrate 30.

[0040] In addition, the element substrate 41 is provided with an opening 411 that penetrates the element substrate 41 along the thickness direction of the element substrate 41 .

[0041] The vibration film 42 is composed of a laminate of multiple films such as SiO2 film and ZrO2 film, etc. The vibration film 42 is arranged in a manner such that the thickness direction of the vibration part 421 is along the Y direction, is provided on one surface of the element substrate 41, and closes one side of the opening 411 (the opposite side of the flow path 20 side).

[0042] In addition, the portion of the vibrating film 42 that overlaps with the opening 411 when viewed from the thickness direction of the element substrate 41 constitutes the vibrating portion 421 that transmits ultrasonic waves. The surface of the pair of surfaces of the vibrating portion 421 that faces the opening 411 becomes a fluid contact surface 422 that contacts the fluid S that flows from the pressure chamber 51 into the opening 411. That is, the vibrating portion 421 has a fluid contact surface 422 that contacts the fluid S in the pressure chamber 51.

[0043] Here, the vibrating membrane 42 is arranged so that the thickness direction of the vibrating membrane 42 (the normal direction of the fluid contact surface 422 ) is along the Y direction.

[0044] The piezoelectric element 43 is provided on the surface opposite to the fluid contact surface 422 with respect to the vibration part 421. Although not shown in the figure, the piezoelectric element 43 is formed by laminating a lower electrode, a piezoelectric film, and an upper electrode in this order on the vibration part 421.

[0045] In such an ultrasonic transmitter 40 , the ultrasonic element 44 is constituted by the vibration portion 421 and the piezoelectric element 43 disposed on the vibration portion 421 .

[0046] In the ultrasonic element 44, the piezoelectric element 43 is connected to a driving unit (not shown), and when a driving signal is input from the driving unit to the piezoelectric element 43, a voltage is applied between the lower electrode and the upper electrode, causing the piezoelectric film to expand and contract. As a result, the vibrating portion 421 flexurally vibrates in the normal direction of the fluid contact surface 422 at a predetermined oscillation frequency corresponding to the dimension W in the short side direction of the vibrating portion 421 (the opening width of the opening portion 411), etc. The flexural vibration of the vibrating portion 421 is converted into a sparse and dense wave of the fluid S to propagate the ultrasonic wave.

[0047] The ultrasonic wave propagating from the vibration part 421 to the fluid S in the pressure chamber 51 diffuses radially with the vibration part 421 as the center, and the ultrasonic wave moving toward the Y direction reaches the flow path 20 from the pressure chamber 51 via the connecting path 52, and is repeatedly reflected by the inner wall of the flow path 20, thereby generating a standing wave SW (first standing wave) in the flow path 20.

[0048] Here, in the flow path 20, in order to generate a standing wave SW in the Y direction, the dimension of the flow path 20 in the Y direction, that is, the flow path width L [m], satisfies the following formula (1).

[0049]

[0050] It should be noted that n is the mode number of the standing wave SW, C is the sound speed [m / s] of the medium of the fluid S, and F is the driving frequency [Hz] of the piezoelectric element 43. It should be noted that the driving frequency F corresponds to the oscillation frequency of the vibration unit 421 described above.

[0051] According to the above formula (1), assuming that the sound speed C of the medium in the case of water is 1500 m / s, the mode number n of the standing wave SW is 1, and the driving frequency F of the piezoelectric element 43 is 600 kHz, the flow path width L is set to 1.25 mm.

[0052] In addition, in order to suppress the generation of a standing wave in the Z direction in the flow path 20, the dimension of the flow path 20 in the Z direction, that is, the flow path depth H [m], satisfies the following formula (2).

[0053]

[0054] That is, the flow path depth H is smaller than the flow path width L when the mode number n of the standing wave SW calculated by the above (1) is 1. That is, according to the above formulas (1) and (2), the flow path 20 is formed such that the flow path depth H is smaller than the flow path width L.

[0055] Alternatively, in order to suppress the generation of a standing wave in the Z direction in the flow path 20, the flow path depth H may not satisfy the above formula (2), but may be set to be significantly larger than the flow path width L set by the above formula (1). In this case, there is a possibility of generating a standing wave of a higher mode in the Z direction, but such a standing wave of a higher mode has a smaller sound power than the standing wave SW generated in the Y direction, so its influence can be ignored.

[0056] [Thickness of the vibration unit 421]

[0057] When the piezoelectric element 43 is driven, not only a transverse wave that causes the vibration unit 421 to generate a flexural vibration is generated, but also a longitudinal wave that propagates inside the vibration unit 421 is generated.

[0058] Assuming that the thickness t of the vibration unit 421 is larger than the wavelength λ of the longitudinal wave, the longitudinal wave dominates in the vibration unit 421, and the propagation efficiency of the ultrasonic wave from the vibration unit 421 to the fluid S is reduced. That is, it is the same as the state where the acoustic impedance is not matched.

[0059] In addition, even when it is assumed that the thickness t of the vibrating portion 421 is smaller than the wavelength λ of the longitudinal wave, some longitudinal waves are generated within the vibrating membrane 42. In particular, when the thickness t of the vibrating portion 421 is equal to λ / 4, the vibrating portion 421 functions as a sound matching layer for the longitudinal wave, and the longitudinal waves generated within the vibrating portion 421 are likely to propagate to the fluid S. However, when the longitudinal wave emits sound, the propagation efficiency of the ultrasonic wave from the vibrating portion 421 to the fluid S is lower than when the transverse wave emits sound.

[0060] Therefore, in the present embodiment, the vibrating portion 421 is formed such that the thickness t is smaller than 1 / 4 of the wavelength λ of the longitudinal wave. That is, the thickness t [m] of the vibrating portion 421 satisfies the following formula (3).

[0061]

[0062] It should be noted that the thickness t of the vibrating portion 421 is the dimension of the vibrating portion 421 along the normal direction with respect to the fluid contact surface 422, and corresponds to the film thickness of the vibrating membrane 42.

[0063] The wavelength λ [m] of the longitudinal wave in the above formula (3) is represented by the following formula (4).

[0064]

[0065] In the above formula (4), C’ is the average sound velocity [m / sec] of the longitudinal wave generated within the vibrating portion 421, and F is the driving frequency [Hz] of the piezoelectric element 43.

[0066] According to the above formula (4), the above formula (3) is represented by the following formula (5).

[0067]

[0068] In addition, as described above, the driving frequency F in the above formula (5) satisfies the following formula (1).

[0069]

[0070] In the above formula (1), L is the flow path width [m], n is the mode number of the standing wave SW, C is the sound velocity [m / s] of the medium of the fluid S, and F is the driving frequency [Hz] of the piezoelectric element 43.

[0071] According to the above formulas (1) and (5), the thickness t of the vibrating portion 421 satisfies the following formula (6).

[0072]

[0073] In addition, the diaphragm 42 of the present embodiment is a laminate of multiple membranes. That is, the vibrating portion 421 of the present embodiment is composed of multiple membranes. In this case, the average sound velocity C' of the longitudinal wave generated in the vibrating portion 421 is calculated by the following method.

[0074] Here, when the number of membranes constituting the vibrating portion 421 is set to m, and the thickness of each membrane constituting the vibrating portion 421 is set to t k (k = 1, 2,... m), and the average value of the longitudinal wave sound velocity in each membrane constituting the vibrating portion 421 is set to C k (k = 1, 2,... m), the following formula (7) holds.

[0075]

[0076] In addition, the thickness t of the vibrating portion 421 is expressed by the following formula (8).

[0077]

[0078] Therefore, according to the above formulas (7) and (8), the average sound velocity C' of the longitudinal wave generated in the vibrating portion 421 is expressed by the following formula (9).

[0079]

[0080] In addition, from the viewpoint of improving the propagation efficiency of ultrasonic waves from the vibrating portion 421 to the fluid S, the thickness t of the vibrating portion 421 is preferably a value that satisfies the above formula (6) and is smaller.

[0081] However, if the thickness t of the vibrating portion 421 is too small, the stress gradient in the thickness direction of the vibrating portion 421 becomes large. Therefore, when the piezoelectric element 43 is driven, the possibility of the vibrating portion 421 being damaged becomes high.

[0082] Therefore, in the present embodiment, an experiment was conducted to drive the piezoelectric element 43 by changing the dimension W in the short side direction of the vibrating portion 421 and the thickness t of the vibrating portion 421. As a result, the thickness t of the vibrating portion 421 preferably satisfies the following formula (10).

[0083]

[0084] In the above formula (10), W is the dimension [m] in the short side direction of the vibrating portion 421, E' is the average Young's modulus [Pa] of the vibrating portion 421 when the Poisson's ratio is set to 0.3, n is the mode number of the standing wave SW, and C is the sound velocity [m / sec] of the medium of the fluid S. If the thickness t of the vibrating portion 421 is thinner than the thickness obtained by the left side of the above formula (10), the possibility of the vibrating portion 421 being damaged becomes high.

[0085] It should be noted that, as described above, the vibrating portion 421 of the present embodiment is composed of multiple (m) films. In this case, the average Young's modulus E' of the vibrating portion 421 can be expressed by the following formula (11).

[0086]

[0087] In addition, α in the above formula (11) is defined by the following formula (12).

[0088]

[0089] In the above formulas (11) and (12), m is the number of films constituting the vibrating portion 421, and E i (i = 1, 2,... m) is the Young's modulus of each film constituting the vibrating portion 421 when the Poisson's ratio is 0.3.

[0090] In addition, d i is expressed by the following formula (13).

[0091]

[0092] In the above formula (13), t k is the thickness of each film constituting the vibrating portion 421 (k = 1, 2,... m). That is, d i is the value obtained by adding the thickness t k of each film constituting the vibrating portion 421 to the i-th one.

[0093] Here, assuming that the fluid device 10 of the present embodiment has the structure described below, through the above formulas (6) and (10), the thickness t of the vibrating portion 421 is preferably within the range of the following formula (14).

[0094] Size W in the short side direction of the vibrating portion: 19 μm

[0095] Flow path width L: 375 μm

[0096] Sound velocity C of the medium of the fluid S: 1500 m / s

[0097] Mode number n of the standing wave SW: 1

[0098] Vibrating film 42: Two-layer structure of SiO2 film and ZrO2 film

[0099] Film thickness t1 of SiO2 film: 0.35 μm

[0100] Film thickness t2 of ZrO2 film: 0.15 μm

[0101] Young's modulus E1 of SiO2: 75 GPa

[0102] Young's modulus E2 of ZrO2: 190 GPa

[0103] Sound velocity C1 of SiO2: 5900 m / s

[0104] Sound velocity C2 of ZrO2: 4650 m / s

[0105] 0.5×10 -6 (m) ≤ t < 685×10 -6 (m) … Equation (14)

[0106] [Configuration of communication path 52]

[0107] When a standing wave SW in the Y direction is generated inside the flow path 20, an antinode A where the sound pressure becomes maximum and a node N where the sound pressure becomes 0 appear periodically along the Y direction. It should be noted that an antinode A appears at each end portion in the Y direction of the flow path 20.

[0108] For example, as Figure 2 shown, when a standing wave SW of the first mode is generated, a node N appears at the center in the Y direction of the flow path 20, and antinodes A appear at each end portion in the Y direction of the flow path 20. In this case, while the fine particles M dispersed in the fluid S flow inside the flow path 20, they converge (sound focusing) toward the range corresponding to the node N of the standing wave SW, that is, the center portion in the Y direction of the flow path 20.

[0109] Here, the range in the Y direction of the flow path 20 is divided into a node region RN corresponding to the node N of the standing wave SW and an antinode region RA corresponding to the antinode A of the standing wave SW.

[0110] It should be noted that when the flow path width of the flow path 20 is set to L and the mode number of the standing wave SW is set to n, each node region RN is set to the range from the center of each node N to ±L / 4n in the Y direction, and each antinode region RA is set to the range other than this.

[0111] In this case, the communication path 52 is connected to the antinode region RA in the flow path 20 corresponding to any antinode A in the standing wave SW. Thus, the ultrasonic wave transmitted from the pressure chamber 51 to the flow path 20 via the communication path 52 is applied to the antinode region RA inside the flow path 20.

[0112] It should be noted that Figure 2 although a standing wave SW of the first mode is illustrated, the standing wave SW generated in the present embodiment may be of the first mode or higher. The antinode region RA and the node region RN in the standing wave SW can be determined based on the mode number of the standing wave SW generated inside the flow path 20, the size in the Y direction of the flow path 20, etc.

[0113] [Each Structure of the Pressure Chamber and the Communication Path]

[0114] In the present embodiment, two communication paths 52 are provided at intervals in the X direction with respect to one pressure chamber 51, and each communication path 52 connects the pressure chamber 51 and the flow path 20. Accordingly, the size of each communication path 52 in the X direction is smaller than the size of the pressure chamber 51 in the X direction. It should be noted that the number of the communication paths 52 is not limited to two, and one or more are acceptable.

[0115] In addition, the size of the communication path 52 in the Z direction is equal to or less than the size of the pressure chamber 51 in the Z direction, and is equal to or less than the size of the flow path 20 in the Z direction.

[0116] Here, the pressure chamber 51 and the communication path 52 are configured such that standing waves are not generated in the fluid S in the pressure chamber 51 and the communication path 52, but standing waves are generated in the fluid S in the flow path 20, and thus the following formula (15) is satisfied.

[0117]

[0118] In the above formula (15), Lr is the size of the communication path 52 in the Y direction [m], Lp is the size of the pressure chamber 51 in the Y direction [m], M is a natural number, n is the mode number of the standing wave SW, and L is the size of the flow path 20 in the Y direction (flow path width) [m] (refer to Figure 1 ).

[0119] In addition, the fluid device 10 is configured to satisfy the following formulas (16) to (18).

[0120]

[0121] W r ≤0.3×d r …Formula (17)

[0122]

[0123] In the above formulas (16) and (17), W r is the width of the communication path 52 in the X direction [m], L is the flow path width [m], n is the mode number of the standing wave SW, and d r is the depth of the communication path 52 in the Z direction [m].

[0124] When the above formulas (16) and (17) are satisfied, when the ultrasonic wave irradiated into the flow path 20 from the communication path 52 is reflected by the wall surface of the flow path 20 and returns to the communication path 52, the beam width of the ultrasonic wave is larger than the width W r of the communication path 52. That is, it becomes a state in which the beam width of the ultrasonic wave is more greatly expanded than the width W r of the communication path 52.

[0125] In addition, in the above formula (18), Sr is the cross-sectional area of the flow path orthogonal to the Y direction of all the communication paths 52 [m 2 , L is the flow path width [m], n is the mode number of the standing wave SW, and Sb is the area of the fluid contact surface 422 of the vibrating portion 421 [m 2 , and δ is the displacement amount of the vibrating portion 421 during vibration [m].

[0126] When the above formula (18) is satisfied, the value obtained by dividing the volume of the range in the flow path 20 facing the Y direction of the communication path 52 by the mode number n of the standing wave SW becomes greater than the maximum change amount of the volume of the pressure chamber 51 generated by the flexural vibration of the vibrating portion 421.

[0127] [Effects of the present embodiment]

[0128] As described above, the fluid device 10 of the present embodiment includes: a flow path 20 through which the fluid S flows; a pressure chamber 51 formed at an interval from the flow path 20 in a first direction (Y direction) orthogonal to the flow direction (X direction) of the fluid S in the flow path 20; a communication path 52 formed along the Y direction and connecting the flow path 20 and the pressure chamber 51; and an ultrasonic transmission unit 40 that transmits ultrasonic waves to the fluid S by contacting the fluid S flowing into the pressure chamber 51, thereby generating a standing wave SW in the fluid S in the flow path 20 along the Y direction.

[0129] In such a structure, since the ultrasonic transmission unit 40 contacts the fluid S, there is no flow path substrate 30 in the ultrasonic wave propagation path from the ultrasonic transmission unit 40 to the fluid S. Therefore, the ultrasonic waves are directly transmitted from the ultrasonic transmission unit 40 to the fluid S, and it is easy to generate a standing wave SW in the flow path 20.

[0130] Here, a fluid device 10A as a comparative example of the fluid device 10 of the present embodiment is shown in Figure 3 . It should be noted that in this comparative example, the same reference numerals as those in the present embodiment are used for the structures corresponding to the present embodiment.

[0131] The fluid device 10A of the comparative example does not include the pressure chamber 51 and the communication path 52 as in the present embodiment, and the ultrasonic transmission unit 40 faces the fluid S in the flow path 20. In such a comparative example, the ultrasonic waves reflected in the flow path 20 directly return to the ultrasonic transmission unit 40. Therefore, the ultrasonic waves transmitted from the ultrasonic transmission unit 40 are defeated by the ultrasonic waves reflected and returned in the flow path 20 and become weak, and it is difficult to overlap the sound power of the ultrasonic waves in the flow path 20. That is, the sound power of the ultrasonic waves in the flow path 20 is determined by the sound power of the initially transmitted ultrasonic waves, and it is difficult to supplement the sound power.

[0132] In contrast, the fluid device 10 of the present embodiment includes a pressure chamber 51 formed separately from the flow path 20 and a communication path 52 that connects the flow path 20 and the pressure chamber 51, and the ultrasonic transmission unit 40 is arranged in contact with the fluid S in the pressure chamber 51.

[0133] According to such a structure, a part of the ultrasonic wave reflected by the wall surface of the flow path 20 returns to the ultrasonic transmission unit 40 via the communication path 52, but the remaining part of the ultrasonic wave is reflected again by the wall surface of the flow path 20. Therefore, it is possible to suppress the weakening of the ultrasonic wave transmitted from the ultrasonic transmission unit 40 due to the ultrasonic wave returning after being reflected in the flow path 20, increase the pressure in the pressure chamber 51, and supplement the sound power in the flow path 20.

[0134] Therefore, in the present embodiment, it is possible to easily generate a standing wave with a large sound power in the flow path 20. As a result, the drive voltage and drive frequency applied to the piezoelectric element 43 can be set lower than before, and the width of the flow path 20 in which the standing wave SW is generated can be made wider than before. As a result, the volume flow rate of the fluid S that can be processed using the fluid device 10 can be increased.

[0135] In the present embodiment, the fluid device 10 is configured to satisfy the above equations (16) and (17), so that the beam width of the ultrasonic wave expands more greatly than the width W of the communication path 52. r Therefore, the effect of suppressing the ratio of the ultrasonic wave returning to the vibration unit 421 can be appropriately exerted. Thereby, the weakening of the ultrasonic wave transmitted from the ultrasonic transmission unit 40 can be appropriately suppressed.

[0136] In the present embodiment, the size (flow path depth H) of the flow path 20 in the Z direction (the second direction orthogonal to the flow direction and the first direction) is smaller than the size (flow path width L) of the flow path 20 in the Y direction.

[0137] Thereby, in the flow path 20, the generation of a standing wave in the Z direction can be suppressed, and a standing wave SW in the Y direction can be appropriately generated.

[0138] In the present embodiment, the communication path 52 is connected to the wave belly region RA corresponding to any wave belly A in the standing wave SW in the flow path 20.

[0139] In such a structure, the ultrasonic wave transmitted from the ultrasonic transmission unit 40 is applied to the wave belly region RA in the flow path 20 via the communication path 52, thereby improving the generation efficiency of the standing wave SW in the flow path 20.

[0140] In the present embodiment, the ultrasonic transmitting unit 40 includes an ultrasonic element 44. The ultrasonic element 44 includes a vibrating portion 421 having a fluid contact surface 422 that contacts the fluid S, and a piezoelectric element 43 disposed on the vibrating portion 421 to cause the vibrating portion 421 to flexurally vibrate in the normal direction of the fluid contact surface 422.

[0141] In such a structure, by converting the flexural vibration of the vibrating portion 421 into a compression wave of the fluid S, ultrasonic waves can be efficiently transmitted to the fluid S.

[0142] In the present embodiment, the fluid device 10 is configured such that the above-described formula (18) holds. Here, the value obtained by dividing the volume of the range within the flow path 20 facing the Y direction of the communication path 52 by the mode number n of the standing wave SW corresponds to the volume change of the medium within the communication path 52. By this value becoming greater than or equal to the maximum volume change of the pressure chamber 51 caused by the flexural vibration of the vibrating portion 421, the volume change of the medium within the pressure chamber 51 caused by the deformation of the vibrating film 42 is discharged as the volume change of the medium within the communication path 52, thereby suppressing the pressure rise within the pressure chamber 51. Therefore, breakage of the vibrating film 42 and the piezoelectric element 43 can be suppressed.

[0143] In the present embodiment, the ultrasonic element 44 is arranged such that the normal direction of the fluid contact surface 422 is along the Y direction.

[0144] According to such a structure, the main transmission direction of the ultrasonic waves from the ultrasonic element 44 is consistent with the propagation direction of the ultrasonic waves that synthesize the standing wave SW within the flow path 20. As a result, the formation efficiency of the standing wave SW can be further improved.

[0145] In the present embodiment, the fluid device 10 is configured such that the above-described formula (6) holds. That is, the thickness of the vibrating portion 421 that contacts the fluid S is formed to be less than 1 / 4 of the wavelength λ of the longitudinal wave generated in the vibrating portion 421.

[0146] According to such a structure, generation of longitudinal waves within the vibrating portion 421 and propagation of longitudinal waves from the vibrating portion 421 to the fluid S can be suppressed, resulting in a state similar to achieving impedance matching between the vibrating portion 421 and the fluid S in contact with the vibrating portion 421. As a result, the propagation efficiency of ultrasonic waves from the ultrasonic element 44 to the fluid S can be improved.

[0147] [Second Embodiment]

[0148] Next, the second embodiment will be described. Hereinafter, the same reference numerals may be given to the same structures as those in the first embodiment, and their descriptions may be omitted or simplified.

[0149] Figure 4is a top view schematically showing a part of the fluid device 10B of the second embodiment, Figure 5 is Figure 4 a sectional view taken along the line B-B of. As Figure 4 and Figure 5 shown, compared with the first embodiment, the fluid device 10B of the second embodiment is mainly different in the arrangement of the ultrasonic transmitting portion 40 with respect to the pressure chamber 51.

[0150] Specifically, on the flow path substrate 30 of the second embodiment, instead of the through hole 331 in the side wall portion 33 of the first embodiment, a through hole 311 is provided which penetrates in the Z direction through a portion of the upper side wall portion 31 of the flow path substrate 30 that forms the wall portion of the pressure chamber 51.

[0151] The ultrasonic transmitting portion 40 is provided on the flow path substrate 30 so as to block the through hole 311 of the flow path substrate 30, thereby forming a part of the wall portion of the pressure chamber 51.

[0152] The element substrate 41 of the ultrasonic transmitting portion 40 is arranged in the through hole 311 of the flow path substrate 30 in such a manner that the thickness direction of the element substrate 41 is along the Z direction, and the outer peripheral surface of the element substrate 41 is in liquid-tight contact with the inner peripheral surface of the through hole 311 of the flow path substrate 30.

[0153] In addition, in the first embodiment, two communication paths 52 are provided with respect to one pressure chamber 51, but in the second embodiment, one communication path 52 is provided with respect to one pressure chamber 51. The size of the communication path 52 in the X direction is equal to the size of the pressure chamber 51 in the X direction. In addition, the size of the communication path 52 in the Z direction is smaller than the size of the pressure chamber 51 in the Z direction and smaller than the size of the flow path 20 in the Z direction.

[0154] In such a fluid device 10B of the second embodiment, the pressure chamber 51 and the communication path 52 also satisfy the above formulas (15) to (17).

[0155] [Effects of the Second Embodiment]

[0156] According to the above second embodiment, the same effects as those of the fluid device 10 of the first embodiment can be achieved.

[0157] In addition, in the second embodiment, the ultrasonic transmitting portion 40 is arranged in such a manner that the thickness direction of the vibration film 42 is along the thickness direction (Z direction) of the flow path substrate 30. Therefore, it is possible to easily utilize MEMS technology when forming the vibration film 42 and the piezoelectric element 43.

[0158] In addition, in the second embodiment, the arrangement range of the ultrasonic transmitting unit 40 with respect to the flow path substrate 30 is not limited to the formation range of the flow path 20, so it is easy to expand the arrangement range of the ultrasonic transmitting unit 40 with respect to the flow path substrate 30. Therefore, as described in the deformation example below, it is easy to provide a plurality of ultrasonic elements 44 in the ultrasonic transmitting unit 40.

[0159] [Third Embodiment]

[0160] Next, the third embodiment will be described.

[0161] Figure 6 is a cross-sectional view schematically showing a part of the fluid device 10C of the third embodiment. As Figure 6 shown, compared with the above-described first and second embodiments, the number of flow paths 20 in the fluid device 10C of the third embodiment is different. That is, the fluid device 10C of the third embodiment includes two flow paths formed in the flow path substrate 30, namely, a first flow path 20A and a second flow path 20B.

[0162] Specifically, the first flow path 20A and the second flow path 20B of the third embodiment are arranged on both sides of the pressure chamber 51 in the Y direction. In other words, the first flow path 20A is arranged at an interval from the pressure chamber 51 in the Y direction, and the second flow path 20B is arranged at an interval from the pressure chamber 51 in the Y direction and is arranged on the opposite side of the pressure chamber 51 in the Y direction with respect to the first flow path 20A.

[0163] It should be noted that the first flow path 20A and the second flow path 20B respectively have the same structure as the flow path 20 described in the above-described first and second embodiments. For example, the first flow path 20A and the second flow path 20B respectively satisfy the above-described formulas (1) and (2).

[0164] In addition, the fluid device 10C of the third embodiment includes a first communication path 52A that communicates the pressure chamber 51 with the first flow path 20A and a second communication path 52B that communicates the pressure chamber 51 with the second flow path 20B.

[0165] The first communication path 52A and the second communication path 52B in the third embodiment are respectively formed along the Y direction and have the same structure as the communication path 52 described in the above-described second embodiment. For example, the first communication path 52A and the second communication path 52B respectively satisfy the above-described formulas (15) to (17).

[0166] In such a structure, the ultrasonic waves transmitted from the ultrasonic wave transmitting unit 40 into the pressure chamber 51 radially spread around the vibrating unit 421. Among them, the ultrasonic waves advancing toward one side in the Y direction reach the inside of the first flow path 20A from the pressure chamber 51 via the first communication path 52A, and are repeatedly reflected on the inner wall of the first flow path 20A, thereby generating a first standing wave in the Y direction within the first flow path 20A. In addition, the ultrasonic waves advancing toward the other side in the Y direction reach the inside of the second flow path 20B from the pressure chamber 51 via the second communication path 52B, and are repeatedly reflected on the inner wall of the second flow path 20B, thereby generating a second standing wave in the Y direction within the second flow path 20B.

[0167] [Effects of the Third Embodiment]

[0168] According to the above third embodiment, the same effects as those of the fluid device 10 of the first and second embodiments can be achieved.

[0169] It should be noted that, in the third embodiment, compared with the standing waves SW generated in the flow path 20 of the first and second embodiments, the acoustic energy of the standing waves respectively generated in the first flow path 20A and the second flow path 20B becomes smaller.

[0170] However, according to the third embodiment, the ultrasonic waves can be propagated from one pressure chamber 51 to two flow paths, namely the first flow path 20A and the second flow path 20B, so that the flow path density in the flow path substrate 30 can be increased.

[0171] In addition, in the third embodiment, the second flow path 20B is arranged on the opposite side of the first flow path 20A with respect to the pressure chamber 51. Here, the first flow path 20A and the second flow path 20B need to be arranged in the Y direction with respect to the pressure chamber 51 respectively. In the third embodiment, for example, compared with a comparative example in which the first flow path 20A and the second flow path 20B are overlapped and arranged in the Z direction, the thickness of the fluid device 10 in the Z direction can be suppressed, and it is easy to miniaturize the fluid device.

[0172] [Fourth Embodiment]

[0173] Next, the fourth embodiment will be described.

[0174] Figure 7 is a cross-sectional view schematically showing a part of the fluid device 10D of the fourth embodiment. As Figure 7 shown, the fluid device 10D of the fourth embodiment has two flow paths, namely the first flow path 20C and the second flow path 20D, formed in the flow path substrate 30 in the same manner as in the above third embodiment. However, the respective arrangements of the first flow path 20C and the second flow path 20D in the fourth embodiment are different from the respective arrangements of the first flow path 20A and the second flow path 20B in the third embodiment.

[0175] In the fourth embodiment, the first flow path 20C and the second flow path 20D are arranged on one side in the Y direction of the pressure chamber 51. In other words, the first flow path 20C is arranged at an interval from the pressure chamber 51 in the Y direction, the second flow path 20D is arranged at an interval from the first flow path 20C in the Y direction, and is arranged on the opposite side of the pressure chamber 51 with respect to the first flow path 20C in the Y direction.

[0176] It should be noted that the first flow path 20C and the second flow path 20D respectively have the same structure as the flow path 20 described in the above first and second embodiments. For example, the first flow path 20C and the second flow path 20D respectively satisfy the above formulas (1) and (2).

[0177] In addition, the fluid device 10D of the fourth embodiment includes a first communication path 52C that communicates the pressure chamber 51 with the first flow path 20C and a second communication path 52D that communicates the first flow path 20C with the second flow path 20D.

[0178] The first communication path 52C and the second communication path 52D in the fourth embodiment are respectively formed along the Y direction and have the same structure as the communication path 52 described in the above second embodiment. For example, the first communication path 52C and the second communication path 52D respectively satisfy the above formulas (15) to (17).

[0179] In such a structure, the ultrasonic wave transmitting unit 40 transmits ultrasonic waves to the fluid S in the pressure chamber 51. The ultrasonic waves propagated from the vibrating unit 421 to the fluid S in the pressure chamber 51 are radially diffused with the vibrating unit 421 as the center. Among them, the ultrasonic waves advancing toward the Y direction side reach the first flow path 20C from the pressure chamber 51 via the first communication path 52C and are repeatedly reflected on the inner wall of the first flow path 20C, thereby generating a first standing wave in the Y direction in the first flow path 20C.

[0180] In addition, a part of the ultrasonic waves reaching the first flow path 20C further reaches the second flow path 20D via the second communication path 52D and is repeatedly reflected on the inner wall of the second flow path 20D, thereby generating a second standing wave in the Y direction in the second flow path 20D.

[0181] [Effects of the Fourth Embodiment]

[0182] According to the above fourth embodiment, the same effects as those of the fluid devices 10 of the first and second embodiments can be achieved.

[0183] It should be noted that in the fourth embodiment, compared with the standing waves SW generated in the flow path 20 of the first and second embodiments, the acoustic energy of the standing waves respectively generated in the first flow path 20C and the second flow path 20D becomes smaller.

[0184] However, according to the fourth embodiment, ultrasonic waves can be made to propagate from one pressure chamber 51 to two flow paths, namely the first flow path 20C and the second flow path 20D. Therefore, the flow path density in the flow path substrate 30 can be increased.

[0185] In addition, in the fourth embodiment, the second flow path 20D is arranged on the opposite side of the first flow path 20C with respect to the pressure chamber 51. With such a structure, the ultrasonic waves propagating from the pressure chamber 51 to the first flow path 20C can be made to propagate to the second flow path 20D more efficiently.

[0186] [Modification Example]

[0187] It should be noted that the present invention is not limited to the above-described embodiments. Modifications, improvements, and structures obtained by appropriately combining the embodiments within the scope where the object of the present invention can be achieved are also included in the present invention.

[0188] (Modification Example 1)

[0189] In the above-described embodiments, an example in which the ultrasonic wave transmitting unit 40 has one ultrasonic element 44 has been described. However, the ultrasonic wave transmitting unit 40 may also have a plurality of ultrasonic elements 44.

[0190] For example, Figure 8 is a cross-sectional view schematically showing a fluid device 10E according to a modification of the second embodiment. The fluid device 10E has an ultrasonic wave transmitting unit 40A composed of a plurality of ultrasonic elements 44. In the ultrasonic wave transmitting unit 40A, a plurality of openings 411 are arranged in an array with respect to the element substrate 41, and the portions of the vibration film 42 provided on the element substrate 41 that overlap the respective openings 411 constitute vibration portions 421. In addition, a plurality of ultrasonic elements 44 are constituted by the respective vibration portions 421 and piezoelectric elements 43 provided on the respective vibration portions 421. Each ultrasonic element 44 has a fluid contact surface 422 that contacts the fluid S in the pressure chamber 51. According to such a modification example, it is easy to increase the pressure in the pressure chamber 51.

[0191] It should be noted that when the ultrasonic wave transmitting unit 40 has a plurality of ultrasonic elements 44, Sb in the above formulas (16) and (17) is the total area of the fluid contact surfaces 422 of the plurality of ultrasonic elements 44.

[0192] (Modification Example 2)

[0193] Various modifications can be made to the specific structure of the ultrasonic wave transmitting unit 40 described in the above-described embodiments.

[0194] For example, the component substrate 41 may also be disposed outside the through-holes 311 and 331 of the flow path substrate 30. In this case, the opening 411 of the component substrate 41 is disposed so as to overlap the through-holes 311 and 331 of the flow path substrate 30, and the lower surface of the component substrate 41 is liquid-tightly joined to the flow path substrate 30.

[0195] In addition, the ultrasonic wave transmitting unit 40 may not include the component substrate 41, and the vibrating membrane 42 may be provided on the flow path substrate 30. In this case, the portion of the vibrating membrane 42 that overlaps the through-holes 311 and 331 of the flow path substrate 30 constitutes the vibrating portion 421.

[0196] (Modification 3)

[0197] In each of the above-described embodiments, as the first direction orthogonal to the flow direction of the fluid S, a standing wave SW is generated in the width direction (Y direction) of the flow path 20, but a standing wave SW may also be generated in the depth direction (Z direction) of the flow path 20. In this case, a structure in which the Y direction described in each of the above-described embodiments is replaced with the Z direction can be adopted.

[0198] [Summary of the Present Disclosure]

[0199] A fluid device according to one aspect of the present disclosure includes: a first flow path through which a fluid flows; a pressure chamber formed at an interval from the first flow path in a first direction orthogonal to the flow direction of the fluid in the first flow path; a first communication path formed along the first direction to communicate the first flow path with the pressure chamber; and an ultrasonic wave transmitting unit that transmits ultrasonic waves to the fluid by contacting the fluid flowing into the pressure chamber, thereby generating a first standing wave in the fluid in the first flow path along the first direction.

[0200] In such a structure, since the ultrasonic wave transmitting unit contacts the fluid, there are no other components in the propagation path of the ultrasonic wave from the ultrasonic wave transmitting unit to the fluid. Thus, the ultrasonic wave is directly transmitted from the ultrasonic wave transmitting unit to the fluid, and it is easy to generate a standing wave in the flow path.

[0201] In addition, a part of the ultrasonic wave reflected by the wall surface of the flow path returns to the ultrasonic wave transmitting unit via the communication path, but the remaining part of the ultrasonic wave is reflected again by the wall surface of the flow path. Therefore, it is possible to suppress the weakening of the ultrasonic wave transmitted from the ultrasonic wave transmitting unit due to the ultrasonic wave returning after being reflected in the flow path, and it is possible to increase the pressure in the pressure chamber and supplement the sound power in the flow path.

[0202] According to the above structure, a standing wave with a large sound power can be easily generated in the flow path. Thus, the driving voltage and driving frequency applied to the ultrasonic transmitting unit can be set lower than before, and the width of the flow path generating the standing wave can be made wider than before. As a result, the volume flow rate of the fluid S that can be processed by the fluid device can be greatly increased.

[0203] In the fluid device according to the present embodiment, preferably, the size of the first flow path in the first direction is set to L, the mode order of the first standing wave is set to n, and the size of the first communication path in the first direction is set to W. r , the dimension of the first communication path in the second direction orthogonal to the flow direction and the first direction is d r When , the following formula is satisfied:

[0204]

[0205] w r ≤0.3×d r .

[0206] In such a configuration, since the ultrasonic beam width is expanded larger than the width of the communication path, the ratio of the ultrasonic wave returning to the vibration unit can be appropriately suppressed, thereby appropriately suppressing the ultrasonic wave transmitted from the ultrasonic wave transmitting unit from being weakened.

[0207] In the fluid device according to this aspect, a dimension of the first flow path in a second direction perpendicular to the flow direction and the first direction is smaller than a dimension of the first flow path in the first direction.

[0208] Thus, in the first flow channel, generation of standing waves in the second direction can be suppressed, and standing waves in the first direction can be appropriately generated.

[0209] In the fluid device according to this aspect, it is preferable that the first communication passage is connected to an antinode region corresponding to an arbitrary antinode of the first standing wave in the first flow channel.

[0210] In such a configuration, the ultrasonic wave transmitted from the ultrasonic wave transmitting unit is applied to the anti-node region in the flow path via the communication path, so that the generation efficiency of the standing wave in the flow path can be improved.

[0211] In the fluid device involved in this method, it is preferred that the ultrasonic transmitting part has one or more ultrasonic elements, and the ultrasonic elements include: a vibrating part having a fluid contact surface in contact with the fluid; and a piezoelectric element arranged in the vibrating part so that the vibrating part flexurally vibrates in the normal direction of the fluid contact surface.

[0212] In such a structure, by converting the flexural vibration of the vibrating portion into a density wave of the fluid, ultrasonic waves can be efficiently transmitted to the fluid.

[0213] In the fluid device according to this embodiment, preferably, when the cross-sectional area of the flow path of the first communication path orthogonal to the first direction is set as Sr, the total area of the fluid contact surfaces of the one or more ultrasonic elements is set as Sb, the maximum displacement amount of the vibrating portion during vibration is set as δ, and the mode number of the first standing wave is set as n, the following formula is satisfied:

[0214]

[0215] According to such a structure, an excessive increase in the pressure in the pressure chamber can be suppressed, and thus breakage of the vibration film and the piezoelectric element can be suppressed.

[0216] In the fluid device according to this embodiment, the ultrasonic element may be arranged such that the normal direction of the fluid contact surface is along the first direction.

[0217] According to such a structure, the main transmission direction of the ultrasonic waves from the ultrasonic element coincides with the propagation direction of the ultrasonic waves that form a standing wave in the flow path. Thereby, the formation efficiency of the standing wave can be further improved.

[0218] In the fluid device according to this embodiment, preferably, when the thickness of the vibrating portion is set as t, the sound speed of the medium of the fluid is set as C, the average sound speed of the longitudinal wave transmitted in the vibrating portion is set as C', the size of the first flow path in the first direction is set as L, and the mode number of the first standing wave is set as n, the following formula is satisfied:

[0219]

[0220] In such a structure, generation of longitudinal waves in the vibrating portion and propagation of longitudinal waves from the vibrating portion to the fluid can be suppressed, resulting in a state similar to achieving impedance matching between the vibrating portion and the fluid in contact with the vibrating portion. As a result, the propagation efficiency of ultrasonic waves from the ultrasonic element to the fluid can be improved.

[0221] Alternatively, the fluid device according to this embodiment further includes: a second flow path arranged at an interval from the pressure chamber in the first direction for the fluid to flow through; and a second communication path formed along the first direction to connect the second flow path and the pressure chamber. The ultrasonic wave transmitting unit transmits ultrasonic waves to the fluid by contacting the fluid flowing into the pressure chamber, thereby further generating a second standing wave along the first direction in the second flow path.

[0222] In such a structure, ultrasonic waves can be made to propagate from one pressure chamber to two flow paths, namely a first flow path and a second flow path, and thus the flow path density in the fluid device can be increased.

[0223] In addition, in the fluid device according to the present embodiment, preferably, the second flow path is arranged on the opposite side of the first flow path with respect to the pressure chamber.

[0224] According to such a structure, it is easy to miniaturize the fluid device.

[0225] Alternatively, the fluid device according to the present embodiment may further include: a second flow path arranged at an interval from the first communication path in the first direction for the fluid to flow through; and a second communication path formed along the first direction to connect the first flow path and the second flow path. The ultrasonic wave transmitting unit contacts the fluid flowing into the pressure chamber and transmits ultrasonic waves to the fluid, thereby further generating a second standing wave along the first direction in the second flow path.

[0226] In such a structure, ultrasonic waves can be made to propagate from one pressure chamber to two flow paths, namely a first flow path and a second flow path, and thus the flow path density in the fluid device can be increased.

[0227] In addition, in the fluid device according to the present embodiment, preferably, the second flow path is arranged on the opposite side of the pressure chamber with respect to the first flow path.

[0228] According to such a structure, the ultrasonic waves propagating from the pressure chamber to the first flow path can be made to propagate more efficiently toward the second flow path.

Claims

1. A fluid device, characterized in that, Comprising: A first flow path for fluid to flow through; A pressure chamber formed at a distance from the first flow path in a first direction orthogonal to the flow direction of the fluid in the first flow path; A first communication path formed along the first direction to connect the first flow path and the pressure chamber; and An ultrasonic transmitting unit that transmits ultrasonic waves to the fluid by contacting the fluid flowing into the pressure chamber, thereby generating a first standing wave in the fluid in the first flow path along the first direction, When the size of the first flow path in the first direction is set to L, the mode number of the first standing wave is set to n, and the size of the first communication path in the first direction is set to W r , and the size of the first communication path in the second direction that is orthogonal to the flow direction and the first direction respectively is set to d r , the following formula is satisfied: w r ≤0.3×d r 。 2. The fluid device according to claim 1, wherein: The size of the first flow path in a second direction orthogonal to the flow direction and the first direction is smaller than the size of the first flow path in the first direction.

3. The fluid device according to claim 1, wherein: The first communication path is connected to a belly region corresponding to any belly of the first standing wave in the first flow path.

4. The fluid device according to claim 1, wherein: The ultrasonic transmitting unit includes one or more ultrasonic elements, The ultrasonic element comprises: A vibrating portion having a fluid contact surface in contact with the fluid; and A piezoelectric element disposed on the vibrating portion and causing the vibrating portion to flexurally vibrate in the normal direction of the fluid contact surface.

5. The fluid device according to claim 4, wherein: When the flow cross-sectional area of the first communication path orthogonal to the first direction is set as Sr, the total area of the fluid contact surfaces of the one or more ultrasonic elements is set as Sb, the maximum displacement amount of the vibrating portion during vibration is set as δ, and the mode number of the first standing wave is set as n, the following formula is satisfied:

6. The fluid device according to claim 4 or 5, wherein: The ultrasonic elements are arranged such that the normal direction of the fluid contact surface is along the first direction.

7. The fluid device according to claim 4, wherein: When the thickness of the vibrating portion is set as t, the sound speed of the medium of the fluid is set as C, the average sound speed of the longitudinal wave transmitted in the vibrating portion is set as C', the size of the first flow path in the first direction is set as L, and the mode number of the first standing wave is set as n, the following formula is satisfied:

8. The fluid device according to claim 1, wherein: The fluid device further comprises: A second flow path arranged at a distance from the pressure chamber in the first direction for the fluid to flow through; and A second communication path formed along the first direction to connect the second flow path and the pressure chamber, The ultrasonic transmitting unit transmits ultrasonic waves to the fluid by contacting the fluid flowing into the pressure chamber, thereby further generating a second standing wave in the second flow path along the first direction.

9. The fluid device according to claim 8, wherein: The second flow path is arranged on the opposite side of the pressure chamber with respect to the first flow path.

10. The fluid device according to claim 1, wherein: The fluid device further comprises: A second flow path, which is arranged at an interval from the first communication path in the first direction and through which the fluid flows; and A second communication path, which is formed along the first direction and connects the first flow path and the second flow path, The ultrasonic wave transmitting unit transmits ultrasonic waves to the fluid by contacting the fluid flowing into the pressure chamber, thereby further generating a second standing wave along the first direction in the second flow path.

11. The fluid device according to claim 10, wherein The second flow path is arranged on the opposite side of the pressure chamber with respect to the first flow path.

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