Fluidic Devices

Abstract

To provide a fluid device that facilitates capturing microparticles at a desired position.SOLUTION: A fluid device includes: a flow path 20 through which a fluid S flows; and an ultrasonic wave application device 40 including an ultrasonic element that transmits an ultrasonic wave. The flow path 20 has, as flow path wall surfaces, an ultrasonic wave application surface 41 that applies to the fluid S the ultrasonic wave transmitted from the ultrasonic element, and a reflection surface 331 that reflects the ultrasonic wave applied to the fluid S from the ultrasonic wave application surface 41. The reflection surface 331 has a concave curved surface shape.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fluidic device. [Background technology]

[0002] 2. Description of the Related Art Fluidic devices that acoustically focus particles in a fluid are known. For example, the fluidic device disclosed in Non-Patent Document 1 includes a flow channel substrate (glass substrate) on which a flow channel is formed, and a piezoelectric element provided on the flow channel substrate. Ultrasonic waves generated by the piezoelectric element are transmitted into the flow channel via the flow channel substrate, generating standing waves in the fluid in the flow channel. Particles in the fluid are trapped within a predetermined area in the flow channel due to the pressure gradient of the fluid formed by the standing waves. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Nobutoshi Ota and six others, "Enhancement in acoustic focusing of micro and nanoparticles by thinning a microfluidic device," Royal Society Open Science, Volume 6, Issue 2, Article No. 181776, December 2019 Summary of the Invention [Problem to be solved by the invention]

[0004] The fluidic device described in Non-Patent Document 1 above focuses microparticles in a fluid using ultrasonic standing waves, but because the conditions for generating the standing waves change due to external disturbances, it has been difficult to construct a fluidic device that can stably capture microparticles at the desired position. [Means for solving the problem]

[0005] A first aspect of the fluid device according to the present invention comprises a flow path through which a fluid flows and an ultrasonic element that transmits ultrasonic waves, and the flow path has, as flow path wall surfaces constituting the flow path, an ultrasonic application surface that applies the ultrasonic waves transmitted from the ultrasonic element to the fluid, and a reflection surface that reflects the ultrasonic waves applied from the ultrasonic application surface to the fluid, and the reflection surface has a concave curved shape.

[0006] In the fluidic device of the first aspect, the reflecting surface preferably has a parabolic shape that forms a focal point within the flow channel in a cross section taken along a plane intersecting the flow direction of the fluid.

[0007] In the fluidic device of the first aspect, it is preferable that the ultrasonic wave application surface faces the reflecting surface.

[0008] In the first embodiment of the fluid device, the ultrasound application surface faces the reflection surface, and it is preferable that the ultrasound application surface and the reflection surface have concentric arc shapes centered on a virtual point within the flow path when viewed in cross section at a plane intersecting the flow direction of the fluid.

[0009] In the first aspect of the fluid device, the device is provided with a plurality of ultrasonic elements, and the flow path has a plurality of ultrasonic application surfaces that apply ultrasonic waves from the plurality of ultrasonic elements to the fluid, and a plurality of reflecting surfaces that respectively face the plurality of ultrasonic application surfaces, and it is preferable that the plurality of ultrasonic application surfaces and the plurality of reflecting surfaces have concentric arc shapes centered on the same virtual point when viewed in cross section.

[0010] In the fluidic device of the first aspect, it is preferable that the phases of the ultrasonic waves transmitted from the plurality of ultrasonic elements are the same.

[0011] In the fluidic device of the first aspect, the flow path has a circular flow path cross section, and when the diameter of the flow path cross section is D, the frequency of the ultrasonic waves is f, and the sound speed of the ultrasonic waves is c, the width w of the ultrasonic wave application surface is

number

[0012] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a part of a fluidic device according to a first embodiment. [Figure 2] Cross-sectional view taken along line AA in Figure 1. [Figure 3] FIG. 3 is a perspective view schematically showing a convergence region of a flow channel in the fluidic device of the first embodiment. [Figure 4] FIG. 10 is a perspective view schematically showing a part of a fluidic device according to a second embodiment. [Figure 5] FIG. 10 is a cross-sectional view schematically showing a fluidic device according to a second embodiment. [Figure 6] 5A and 5B are schematic diagrams for explaining the beam width of ultrasonic waves in the fluidic device of the second embodiment. [Figure 7] FIG. 10 is a schematic diagram illustrating a fluidic device according to a modified example of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] [First embodiment] The fluidic device of the first embodiment will be described below. Fig. 1 is a cross-sectional view schematically showing a portion of a fluidic device 10 of this embodiment, and Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. This fluidic device 10 includes a flow path substrate 30 that forms a flow path 20, and an ultrasonic application device 40 provided on the flow path substrate 30. In the following description, the flow direction of a fluid S flowing through the flow path 20 is defined as the X direction, the direction perpendicular to the X direction is defined as the Y direction, and the direction perpendicular to the X and Y directions is defined as the Z direction.

[0014] In the fluidic device 10 of this embodiment, ultrasonic waves transmitted from an ultrasonic wave application device 40 are applied to a fluid S flowing through a convergence region R, which is a partial region in the X direction of a flow channel 20, and particles or microfibers (hereinafter referred to as particles M) dispersed in the fluid S converge. The fluid S is not particularly limited, but is, for example, water. In such a fluidic device 10, for example, by providing a fluid inlet for allowing fluid S to flow into the flow path 20 and a fluid outlet for allowing fluid S to flow out of the flow path 20, it is possible to concentrate the particles M in the flow path 20. Alternatively, the flow path 20 can be provided with a concentration flow path that selectively circulates the fluid S containing the converged particles M, and a discharge flow path that selectively circulates other fluids S, thereby concentrating the particles M in the fluid S. 1 schematically illustrates the state of the particles M being converged within the flow channel 20. In addition, in FIG. 2, the illustration of the particles M is omitted, and the traveling direction of the ultrasonic waves entering the flow channel 20 is indicated by an arrow.

[0015] (flow path substrate 30) As shown in FIGS. 1 and 2, the flow path substrate 30 includes a base substrate 31, a lid substrate 32 (see FIG. 2), and a wall portion 33. The base substrate 31 is provided with a groove 311 that is concave on the +Z side along the X direction, and the lid substrate 32 is arranged to cover the groove 311 of the base substrate 31. The wall portion 33 is arranged along one side surface of the groove 311 and has a reflective surface 331 that serves as a flow path wall surface. The flow path 20 is mainly formed by the lower surface of the lid substrate 32, the other side surface and bottom surface of the groove 311 of the base substrate 31, and the reflective surface 331 of the wall portion 33.

[0016] In addition, in the convergence region R, which is a part of the flow path 20 in the X direction, the groove 311 of the base substrate 31 includes a part formed with a larger width in the Y direction than other parts, and an ultrasonic wave application device 40 is arranged in this part so as to face the reflecting surface 331 of the wall portion 33. 3 is a perspective view schematically showing the convergence region R of the flow channel 20. In FIG. 3, the wall portion 33 and the ultrasonic application device 40 are indicated by solid lines, and the portions of the base substrate 31 and the lid substrate 32 that face the flow channel 20 are indicated by dashed lines. As shown in Figure 3, the convergence region R of the flow path 20 is formed by the lower surface of the lid substrate 32, the bottom surface of the groove 311 of the base substrate 31, the reflecting surface 331 of the wall portion 33, and the ultrasonic application surface 41 of the ultrasonic application device 40.

[0017] (Reflective surface 331) As shown in FIG. 2, the reflecting surface 331 has a parabolic shape in a cross section (i.e., YZ cross section) perpendicular to the fluid flow direction (X direction) with the axis of symmetry SL being an axis parallel to the Y direction, and this parabolic shape forms a focal point F within the flow path 20. For example, when the YZ cross section of the reflecting surface 331 has a parabolic shape expressed by the following formula (1), the distance from the origin O of the parabolic shape to the focal point F is 1 / 4a. Here, the flow channel 20 is formed so that the shortest distance from the part (bottom 332) corresponding to the origin O of the parabolic shape of the reflecting surface 331 to the ultrasound application surface 41 is greater than the distance from the bottom 332 to the focal point F (i.e., 1 / 4a).

number

[0018] As shown in FIG. 3, the reflecting surface 331 forms a linear focus FL in the flow channel 20, which is a continuation of the parabolic focus F in the X direction. In such a configuration, when ultrasonic waves are incident on the reflecting surface 331 in a direction along the symmetry axis SL (i.e., the Y direction), the angle of incidence and the angle of reflection of the ultrasonic waves become symmetrical with respect to the normal to the reflecting surface 331, and the ultrasonic waves reflected by the reflecting surface 331 are concentrated on the linear focus FL.

[0019] (ultrasonic wave application device 40) The ultrasonic wave application device 40 includes one or more ultrasonic elements, and transmits ultrasonic waves that become plane waves to the reflecting surface 331. The ultrasonic element has, for example, a piezoelectric actuator or a vibration plate as a vibrator. For example, when an ultrasonic element has a piezoelectric actuator as a vibrator, applying a drive voltage to the piezoelectric actuator causes the piezoelectric actuator itself to vibrate and generate sound waves. Furthermore, when the ultrasonic element has a diaphragm as a vibrator, applying a drive voltage to a piezoelectric thin film formed on the diaphragm vibrates the diaphragm to generate sound waves. Alternatively, the ultrasonic element may include a diaphragm as a vibrator and a substrate disposed opposite the diaphragm, and electrodes formed on the diaphragm and the substrate may constitute an electrostatic actuator. In this case, the ultrasonic element applies a drive voltage to the electrostatic actuator to vibrate the diaphragm and generate sound waves. The ultrasonic wave application device 40 may be configured to include not only the ultrasonic element described above, but also an acoustic matching layer, an acoustic lens, and the like.

[0020] The frequency of the ultrasonic waves generated by the ultrasonic elements in the ultrasonic application device 40 is not particularly limited, but is preferably ultrasonic waves in the frequency band of 300 kHz to 50 MHz. For example, ultrasonic waves in the low frequency range, specifically the frequency band of 10 kHz to 300 kHz, cause cavitation in the fluid S, making them unsuitable for capturing fine particles M in the fluid S. For this reason, it is preferable to use ultrasonic waves with a frequency of 300 kHz or higher. Furthermore, when using ultrasonic waves in a frequency band of 50 MHz or lower, a general driving source can be used as the driving source for the ultrasonic elements.

[0021] In this embodiment, the ultrasonic wave application device 40 has an ultrasonic wave application surface 41 that applies ultrasonic waves transmitted from the above-mentioned ultrasonic element to the fluid S. Here, the ultrasonic wave application surface 41 may be formed by a vibration plate that constitutes the ultrasonic element. Furthermore, when the ultrasonic wave application device 40 includes an acoustic matching layer or an acoustic lens, the ultrasonic wave application surface 41 may be formed by the acoustic matching layer or the acoustic lens. As described above, this ultrasonic wave application surface 41 becomes part of the flow channel wall surface that constitutes the convergence region R of the flow channel 20.

[0022] In this embodiment, it is preferable that the ultrasonic wave application device 40 transmits ultrasonic waves with high directionality toward the reflecting surface 331. Specifically, it is preferable that the near field limit N of the ultrasonic waves transmitted from the ultrasonic wave application device 40 is greater than the shortest distance from the ultrasonic wave application surface 41 to the bottom 332 of the reflecting surface 331.

[0023] Here, the near field limit N of the ultrasonic waves transmitted from the ultrasonic wave application device 40 of this embodiment is expressed by the following formula (2) or formula (3). Specifically, when the shape of the vibration region (hereinafter referred to as the vibration part) of the vibration plate constituting the ultrasonic element of the ultrasonic wave application device 40 is circular, the following formula (2) holds, and when the shape of the vibration part is rectangular, the following formula (3) holds.

number

[0024] In the above formulas (2) and (3), the frequency (Hz) of the ultrasonic waves is represented by f, and the speed of sound (m / s) is represented by c. In addition, in the above formula (2), the diameter (m) of the circular vibrating part is represented by d, and in the above formula (3), the long side dimension (m) of the rectangular vibrating part is represented by L. The predetermined coefficient k in the above formula (3) is defined as shown in Table 1 below. The dimensional ratio in the following Table 1 is the dimensional ratio of the short side to the long side of the vibrating part, and when the dimensional ratio is 1, the shape of the vibrating part is square. Note that the maximum value of the dimensional ratio is 1, so the maximum value of the predetermined coefficient k is 1.37. [Table 1]

[0025] (Capturing fine particles M) According to the above configuration, the ultrasonic waves applied to the fluid S from the ultrasonic application surface 41 are incident on the reflecting surface 331 in a direction along the symmetry axis SL (i.e., the Y direction). The ultrasonic waves reflected by the reflecting surface 331 are concentrated on the linear focus FL, causing constructive interference. As a result, sound pressure is concentrated on the linear focus FL, generating a sound pressure gradient that causes the particles M to remain on the linear focus FL, and the particles M in the fluid S are trapped near the linear focus FL.

[0026] (Effects of the first embodiment) As described above, the fluidic device 10 of this embodiment includes a flow path 20 through which the fluid S flows and an ultrasonic wave application device 40 that transmits ultrasonic waves, and the flow path 20 has, as flow path wall surfaces, an ultrasonic wave application surface 41 that applies ultrasonic waves to the fluid S and a reflecting surface 331 that reflects the ultrasonic waves applied from the ultrasonic wave application surface 41 to the fluid S, and the reflecting surface 331 has a concave curved surface shape. In particular, in this embodiment, the YZ cross section of the reflecting surface 331 has a parabolic shape that forms a focal point F within the flow path 20. According to this configuration, the reflecting surface 331 forms a linear focus FL in the flow channel 20, with the focus F being continuous, and the ultrasonic waves reflected by the reflecting surface 331 are concentrated at the linear focus FL in the flow channel 20. This creates an area where strong sound pressure acts near the linear focus FL in the flow channel 20, and particles M can be captured in this area. Therefore, in the fluidic device 10 of this embodiment, it is not necessary to generate standing waves, which require strict conditions for generation, and it is easy to capture particles M at desired positions.

[0027] Furthermore, in the fluidic device 10 of this embodiment, the ultrasound application surface 41 faces the reflecting surface 331. With this configuration, the ultrasound transmitted from the ultrasound application surface 41 is likely to be incident on the reflecting surface 331 along the symmetry axis SL of the parabolic shape, and therefore the ultrasound can be suitably concentrated on the linear focus FL within the flow channel 20. As a result, the particles M can be more suitably trapped.

[0028] The above-described fluidic device 10 can appropriately separate fine particles M contained in a fluid S, thereby broadening the range of uses of the fluidic device 10. For example, by flowing domestic wastewater discharged from a washing machine or a kitchen into the fluidic device 10, the fine particles M contained in the domestic wastewater can be separated. In this case, fine plastic fibers contained in the washing water and abrasive powder from detergent contained in kitchen wastewater can be separated, thereby making it possible to reduce environmental damage caused by harmful substances such as plastic waste. The fluidic device 10 can also be suitably used for separating fine particles M dispersed in a medium such as an industrial product or a pharmaceutical product, and for separating cells or viruses in a liquid.

[0029] [Second embodiment] Next, a fluidic device according to a second embodiment will be described with reference to Figures 4 to 6. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof may be omitted or simplified.

[0030] FIG. 4 is a perspective view that schematically shows a part of a fluidic device 10A of the second embodiment, and FIG. 5 is a cross-sectional view of the fluidic device 10A of the second embodiment taken along a plane perpendicular to the flow direction of the fluid S. 4 and 5, the fluidic device 10A includes a tubular member 50 and a plurality of ultrasonic wave applicators 40 provided in the tubular member 50, and forms a flow path 20A through which a fluid S flows in the X direction. In this fluidic device 10A, similar to the first embodiment, ultrasonic waves transmitted from the ultrasonic wave applicators 40 are applied to the fluid S flowing through a convergence region R, which is a partial region of the flow path 20 in the X direction, thereby converging the particles M dispersed in the fluid S.

[0031] The tubular member 50 has a cylindrical shape with a central axis C along the X direction, and the flow path 20A in the fluidic device 10A is mainly formed by an inner circumferential surface 51 of the tubular member 50. The inner circumferential surface 51 of the tubular member 50 has a circular shape centered on the central axis C when viewed in a cross section on a plane perpendicular to the flow direction of the fluid S (i.e., when viewed in a YZ cross section).

[0032] The ultrasonic wave application device 40 has the same configuration as in the first embodiment. In this embodiment, the ultrasonic wave application device 40 is disposed in a through-hole formed in the tubular member 50, and has an ultrasonic wave application surface 41 that serves as a flow path wall surface. That is, in this embodiment, the convergence region R of the flow path 20 is formed by the inner circumferential surface 51 of the tubular member 50 and the ultrasonic wave application surface 41 of the ultrasonic wave application device 40. The ultrasonic wave application devices 40 are arranged at different positions on the same circumference centered on the central axis C of the cylindrical member 50, and transmit ultrasonic waves with the same phase.

[0033] In this embodiment, it is preferable that each of the ultrasonic wave application surfaces 41 of the multiple ultrasonic wave application devices 40 has an arc shape that is the same circle as the inner circumferential surface 51 of the cylindrical member 50 when viewed in cross section on a plane perpendicular to the flow direction of the fluid S (i.e., when viewed in YZ cross section). Such ultrasonic wave application surfaces 41 apply ultrasonic waves in the radial direction of the cylindrical member 50, toward the central axis C of the cylindrical member 50. It is also preferable that such ultrasonic wave application surfaces 41 are formed by, for example, an acoustic matching layer or an acoustic lens that constitutes the ultrasonic wave application device 40.

[0034] In this embodiment, it is preferable that the ultrasonic wave application device 40 transmits ultrasonic waves with high directionality. Specifically, it is preferable that the near field limit N of the ultrasonic waves transmitted from the ultrasonic wave application device 40 is larger than the flow path diameter D, which is the diameter of the inner circumferential surface 51 of the tubular member 50 (i.e., the diameter of the flow path cross section). Note that the formula for calculating the near field limit N can be formula (2) or formula (3) described in the first embodiment above.

[0035] According to the above configuration, the ultrasonic waves applied to the fluid S from the ultrasonic application surface 41 pass through the central axis C of the cylindrical member 50 and reach the region of the inner circumferential surface 51 of the cylindrical member 50 facing the ultrasonic application surface 41 (i.e., the reflecting surface 511). These ultrasonic waves are incident on the reflecting surface 511 at an incident angle of 0°, and upon being reflected by the reflecting surface 511, they change direction by 180° from the incident direction and travel again, passing through the central axis C within the flow channel 20A. Therefore, the ultrasonic waves applied to the fluid S from the ultrasonic application surface 41 and the ultrasonic waves reflected by the reflecting surface 511 are each concentrated on the central axis C, causing constructive interference between them.

[0036] Here, the cylindrical member 50 of this embodiment is provided with a plurality (for example, three) of ultrasonic wave application devices 40, and the inner circumferential surface 51 of the cylindrical member 50 includes a plurality (for example, three) of reflecting surfaces 511 facing each of the ultrasonic wave application surfaces 41. The YZ cross sections of the inner circumferential surface 51 and the reflecting surfaces 511 each have an arc shape of the same circle. 5, in this embodiment, not only ultrasonic waves from one ultrasonic application surface 41 but also ultrasonic waves from multiple ultrasonic application surfaces 41 overlap near the central axis C. Furthermore, ultrasonic waves from multiple reflecting surfaces 511 also overlap near the central axis C. Note that since the phases of the ultrasonic waves from the multiple ultrasonic application surfaces 41 are aligned with each other, the ultrasonic waves from the multiple ultrasonic application surfaces 41 and the ultrasonic waves from the multiple reflecting surfaces 511 overlap near the central axis C, causing constructive interference. Therefore, in this embodiment, sound pressure is concentrated near the central axis C in the flow channel 20A, and a sound pressure gradient is generated such that the particles M remain near the central axis C, and the particles M in the fluid S are captured.

[0037] In this embodiment, the beam width of the ultrasonic waves applied from the ultrasonic wave application surface 41 has a suitable range of beam widths. Specifically, if the diameter d of the circular vibrating part or the long side dimension L of the rectangular vibrating part in the ultrasonic application device 40 is equal to the beam width w of the ultrasonic waves, and if K = kf / 4c in the above equation (2) (or if K = f / 4c in the above equation (3)), the following equation (4) holds.

number

[0038] Then, on the condition that the flow path diameter D is smaller than the near field limit N, the lower limit of the beam width w can be defined by the following equations (5) to (7).

number

[0039] Furthermore, when an ultrasonic wave from any ultrasonic application surface 41 reaches a reflecting surface 511 as an incident wave, the upper limit of the beam width w can be defined under the condition that the reflected wave emitted from the reflecting surface 511 does not directly reach an ultrasonic application surface 41 adjacent to the ultrasonic application surface 41. For example, FIG. 6 is a diagram that schematically shows the diffusion of ultrasonic waves from an ultrasonic wave application surface 41 that is placed in the center of the figure. In FIG. 6, the angle θ of the arc formed by the reflecting surface 511 on which the incident wave arrives is geometrically expressed by the following formula (8).

number

number

[0040] Here, in order for the reflected wave not to directly reach the adjacent ultrasonic wave application surface 41, it is necessary to satisfy the following formula (10). In the following formula (10), φ iis the angle formed by the central axes of the adjacent ultrasonic wave application surfaces 41, and the central axes of the ultrasonic wave application surfaces 41 intersect with the central axis C of the cylindrical portion. i The maximum value of the angle is 180° when the two ultrasonic wave application devices 40 are arranged facing each other with the central axis C of the cylindrical portion therebetween.

number

number

[0041] Therefore, from the above equations (7) and (13), the beam width w is expressed by the following equation (14).

number

[0042] Here, an example that satisfies the above formula (14) will be described. is the lower limit of the beam width w

number

number

number

number

number

[0043] (Effects of the second embodiment) Similar to the first embodiment, the fluidic device 10A of this embodiment has a concavely curved reflecting surface 511. The ultrasound application surface 41 faces the reflecting surface 511, and the ultrasound application surface 41 and the reflecting surface 511 have concentric arc shapes centered on the central axis C (corresponding to an imaginary point in the flow channel 20) in the YZ cross section. With this configuration, the ultrasonic waves applied from the ultrasonic application surface 41 and the ultrasonic waves reflected by the reflection surface 511 each gather near the central axis C within the flow path 20, creating an area within the flow path 20 where strong sound pressure acts, and particles M can be captured in that area. Therefore, in the fluidic device 10A of this embodiment, similarly to the first embodiment, there is no need to generate standing waves, which require strict conditions for generation, and it is easy to capture particles M at desired positions.

[0044] In the fluidic device 10A of this embodiment, the flow path 20 has a plurality of ultrasound application surfaces 41 and a plurality of reflection surfaces 511 respectively facing the plurality of ultrasound application surfaces 41, and the plurality of ultrasound application surfaces 41 and the plurality of reflection surfaces 511 have concentric arc shapes centered on a central axis C (corresponding to the same imaginary point) within the flow path 20. With this configuration, the ultrasound waves applied from the plurality of ultrasound application surfaces 41 and the ultrasound waves reflected by the plurality of reflection surfaces 511 gather near the central axis C within the flow path 20, thereby creating an area within the flow path 20 where stronger sound pressure acts, and the particles M can be suitably captured.

[0045] In the fluidic device 10A of this embodiment, the phases of the ultrasonic waves applied to the fluid S from the multiple ultrasonic application surfaces 41 are matched with each other. With this configuration, the ultrasonic waves converging near the central axis C in the flow channel 20 can favorably generate constructive interference with each other.

[0046] In the fluidic device 10A of this embodiment, it is preferable that the width of the ultrasound application surface 41 (i.e., the beam width w) satisfies the above-mentioned formula (14), particularly the above-mentioned formula (18). With such a configuration, the adjacent ultrasound application surfaces 41 do not adversely affect each other, and highly directional ultrasound can be emitted toward the corresponding reflecting surfaces 511. This allows the particles M to be suitably captured.

[0047] [Variations] The present invention is not limited to the above-described embodiments, and the present invention includes configurations obtained by modifications, improvements, and appropriate combinations of the embodiments within the scope that can achieve the object of the present invention.

[0048] In the first and second embodiments, the ultrasonic wave application device 40 has the ultrasonic wave application surface 41 which becomes the flow path wall surface, but a wall member may be disposed between the ultrasonic wave application device 40 and the fluid S, and the wall member may have the ultrasonic wave application surface which becomes the flow path wall surface. In other words, the ultrasonic waves transmitted from the ultrasonic wave application device 40 may be applied to the fluid S through the wall member.

[0049] The fluidic device 10 of the first embodiment is provided with one ultrasonic wave application device 40 having a planar ultrasonic wave application surface 41. As a modification of this, as shown in the schematic diagram of FIG. 7, a wall member 60 forming a flow path wall surface may be employed, and multiple ultrasonic wave application devices 40 may be provided for this wall member 60. In this case, the wall member 60 has an ultrasonic wave application surface 61 that applies ultrasonic waves transmitted from the multiple ultrasonic wave application devices 40 to the fluid S. Furthermore, it is preferable that the multiple ultrasonic wave application devices 40 form a plane wave W directed from the ultrasonic wave application surface 61 toward the reflecting surface 331 by mutually shifting the phases of the transmitted waves according to their respective positions.

[0050] In the second embodiment, the ultrasonic wave application surface 41 and the reflecting surface 511 have the arc shape of the same circle, but the present invention is not limited to this. For example, the ultrasonic wave application surface 41 and the reflecting surface 511 facing the ultrasonic wave application surface 41 may have the arc shape of concentric circles with different diameters. Furthermore, the fluid device 10A of the second embodiment has multiple ultrasound application surfaces 41 and multiple reflection surfaces 511 facing each ultrasound application surface 41, but the present invention is not limited to this and may have one ultrasound application surface 41 and one reflection surface 511 facing the ultrasound application surface 41.

[0051] In the first embodiment, the reflecting surface 331 serving as the flow path wall surface has a parabolic shape in a YZ cross section, and in the second embodiment, the reflecting surface 511 serving as the flow path wall surface has an arc shape in a YZ cross section, but the present invention is not limited to these. That is, the reflecting surface 331 in the first embodiment or the reflecting surface 511 in the second embodiment may have any concave curved shape.

[0052] Summary of this disclosure A first aspect of the fluid device according to the present invention comprises a flow path through which a fluid flows and an ultrasonic element that transmits ultrasonic waves, and the flow path has, as flow path wall surfaces constituting the flow path, an ultrasonic application surface that applies the ultrasonic waves transmitted from the ultrasonic element to the fluid, and a reflection surface that reflects the ultrasonic waves applied from the ultrasonic application surface to the fluid, and the reflection surface has a concave curved shape. With this configuration, ultrasonic waves reflected by the concave curved reflecting surface create constructive interference within the flow channel, creating an area where strong acoustic pressure acts, allowing particles to be trapped in that area. This eliminates the need to generate standing waves, which require strict conditions for generation, and provides a fluidic device that can easily trap particles at desired locations.

[0053] In the fluidic device of the first aspect, the reflecting surface preferably has a parabolic shape that forms a focal point within the flow channel when viewed in a cross section taken along a plane intersecting the flow direction of the fluid. In this configuration, the reflecting surface forms a continuous linear focal point within the flow channel, and ultrasonic waves reflected by the reflecting surface are concentrated at the linear focal point within the flow channel. This makes it possible to preferably generate an area within the flow channel where strong sound pressure acts near the linear focal point.

[0054] In the fluidic device of the first aspect, the ultrasonic wave application surface is preferably opposite to the reflecting surface, and with such a configuration, ultrasonic waves transmitted from the ultrasonic wave application surface are likely to be incident on the reflecting surface along the symmetry axis of the parabolic shape, thereby enabling the ultrasonic waves to be suitably concentrated at a linear focus within the flow channel.

[0055] In the fluidic device of the first aspect, it is preferable that the ultrasound application surface faces the reflecting surface, and the ultrasound application surface and the reflecting surface have concentric arc shapes centered on a virtual point in the flow channel when viewed in a cross section of a plane intersecting the flow direction of the fluid. With this configuration, ultrasound applied from the ultrasound application surface and ultrasound reflected by the reflecting surface each converge near the virtual point in the flow channel, thereby generating a region in the flow channel where strong acoustic pressure acts, and particles can be trapped in that region.

[0056] The fluidic device of the first aspect includes a plurality of ultrasonic elements, and the flow path has a plurality of ultrasonic application surfaces that apply ultrasonic waves from the plurality of ultrasonic elements to the fluid, and a plurality of reflecting surfaces that respectively face the plurality of ultrasonic application surfaces, and the plurality of ultrasonic application surfaces and the plurality of reflecting surfaces preferably have concentric arc shapes centered on the same imaginary point in the cross-sectional view. With this configuration, the ultrasonic waves applied from the plurality of ultrasonic application surfaces and the ultrasonic waves reflected by the plurality of reflecting surfaces are concentrated near the imaginary point in the flow path, thereby creating an area in the flow path where stronger sound pressure acts.

[0057] In the fluidic device of the first aspect, it is preferable that the phases of the ultrasonic waves transmitted from the plurality of ultrasonic elements are matched with each other. With this configuration, the ultrasonic waves converging near the virtual point in the flow path can preferably generate constructive interference with each other.

[0058] In the fluidic device of the first aspect, the flow path has a circular flow path cross section, and when the diameter of the flow path cross section is D, the frequency of the ultrasonic waves is f, and the sound speed of the ultrasonic waves is c, the width w of the ultrasonic wave application surface is

number

[0059] 10, 10A...fluidic device, 20, 20A...flow path, 30...flow path substrate, 31...base substrate, 311...groove, 32...lid substrate, 33...wall portion, 331...reflecting surface, 332...bottom portion, 40...ultrasonic wave application device, 41...ultrasonic wave application surface, 50...cylindrical member, 51...inner surface, 511...reflecting surface, 60...wall member, 61...ultrasonic wave application surface, C...central axis, D...flow path diameter, F...focus, FL...linear focus, M...particle, R...convergence region, S...fluid, SL...symmetry axis, w...beam width.

Claims

1. a flow path through which a fluid flows; a plurality of ultrasonic elements for transmitting ultrasonic waves; The flow path has, as flow path wall surfaces constituting the flow path, a plurality of ultrasound application surfaces that apply the ultrasound waves transmitted from the plurality of ultrasound elements to the fluid, and a plurality of reflection surfaces that face the plurality of ultrasound application surfaces and reflect the ultrasound waves applied to the fluid from the plurality of ultrasound application surfaces, the plurality of ultrasonic wave application surfaces and the plurality of reflecting surfaces have concentric arc shapes centered on the same imaginary point within the flow path in a cross-sectional view taken along a plane intersecting the flow direction of the fluid, The flow path has a circular flow path cross section, When the diameter of the flow path cross section is D, the frequency of the ultrasonic waves is f, and the sound speed of the ultrasonic waves is c, the width w of the ultrasonic wave application surface is expressed as follows: [Equation 1] Meet the fluidic device.

2. The fluidic device according to claim 1 , wherein the ultrasonic waves transmitted from the plurality of ultrasonic elements are in phase with each other.

Images