Fluidic device and method for controlling the fluidic device

Abstract

To provide a fluid device that can stably generate standing wave.SOLUTION: The fluidic device includes a flow path extending along a first axis and inside of which fluid flows, an ultrasonic wave transmitting unit arranged in the flow path and for transmitting ultrasonic wave in the inside of the flow path along a second axis orthogonal to the first axis by input of driving signal, and a control unit for controlling the ultrasonic wave transmitting unit, and in which the control unit changes driving frequency of the driving signal within a prescribed range and measures the impedance of the ultrasonic wave transmitting unit when the ultrasonic wave transmitting unit is driven, identifies the driving frequency at which the impedance becomes maximum as a first driving frequency, and inputs the driving signal having the first driving frequency to the ultrasonic wave transmitting unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fluidic device and a method for controlling a fluidic device. [Background technology]

[0002] Conventionally, 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. The particles in the fluid are trapped within a predetermined range in the flow channel due to the pressure gradient of the fluid formed by the standing wave. [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 it has been difficult to generate standing waves stably because the conditions for generating the standing waves change due to external disturbances such as temperature fluctuations. [Means for solving the problem]

[0005] A fluidic device of a first aspect according to the present disclosure comprises a flow path extending along a first axis and through which a fluid flows, an ultrasonic transmitter disposed in the flow path and configured to transmit ultrasonic waves into the flow path along a second axis perpendicular to the first axis upon input of a drive signal, and a control unit for controlling the ultrasonic transmitter, wherein the control unit measures the impedance of the ultrasonic transmitter when the ultrasonic transmitter is driven by changing the drive frequency of the drive signal within a predetermined range, identifies the drive frequency at which the impedance is maximized, sets this as a first drive frequency, and inputs the drive signal of the first drive frequency to the ultrasonic transmitter.

[0006] A first aspect of the control method for a fluidic device is a control method for a fluidic device that captures microparticles in a fluid flowing inside a flow path extending along a first axis, and includes an ultrasonic transmitting unit that is arranged in the flow path and transmits ultrasonic waves into the flow path along a second axis perpendicular to the first axis upon input of a drive signal, measures the impedance of the ultrasonic transmitting unit when the drive frequency of the drive signal is changed within a predetermined range to drive the ultrasonic transmitting unit, identifies the drive frequency at which the impedance is maximized and sets it as a first drive frequency, and inputs the drive signal of the first drive frequency to the ultrasonic transmitting unit. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram schematically illustrating a fluidic device according to a first embodiment. [Figure 2] 5 is a diagram showing a change in impedance of a second ultrasonic element when the drive frequency of a second drive signal is changed in the first embodiment. FIG. [Figure 3] 4 is a flowchart showing a control method for the fluidic device of the first embodiment. [Figure 4] FIG. 10 is a diagram showing the relationship between the drive frequency and the impedance of the second ultrasonic element when the temperature of the fluid is changed in the first embodiment. [Figure 5] FIG. 10 is a diagram schematically illustrating a fluidic device according to a second embodiment. [Figure 6]10 is a flowchart showing a control method for a fluidic device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] [First embodiment] The fluidic device of the first embodiment will be described below. (Configuration of fluidic device) FIG. 1 is a cross-sectional view schematically showing a fluidic device 10 of the first embodiment. The fluidic device 10 includes a flow path 20 that extends along a first axis, the X-axis, and through which a fluid S flows, a first ultrasonic element 30 that generates a standing wave SW along a second axis, the Y-axis, in the fluid S within the flow path 20, a second ultrasonic element 40 that transmits ultrasonic waves to the fluid S within the flow path 20 and receives ultrasonic waves transmitted by the fluid S, and a control unit 50 that controls the driving of the first ultrasonic element 30. The X-axis and Y-axis are mutually orthogonal, and the axis orthogonal to each of the X-axis and Y-axis is referred to as the Z-axis.

[0009] In this fluidic device 10, a standing wave SW of an arbitrary mode order is formed along the Y-axis in a partial region in the X-axis direction within the flow channel 20. As particles M dispersed in the fluid S flow through the flow channel 20, they are affected by the pressure gradient formed by the standing wave SW and converge to a predetermined range centered on a node of the standing wave SW. The fluid S is not particularly limited, but may be, for example, water or blood. The particles M may be, for example, microfibers or cells. In such a fluid device 10, for example, 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 converged within the flow path 20. In addition, as an example, FIG. 1 also schematically illustrates a standing wave SW of a first mode generated within the flow path 20, but the mode order of the standing wave SW is not particularly limited.

[0010] The flow channel 20 has a first wall surface 21 and a second wall surface 22 that face each other in the Y-axis direction. The flow channel width L between the first wall surface 21 and the second wall surface 22 is a known value. The specific configuration of the flow channel 20 is not particularly limited, but may be formed, for example, by a base substrate having a groove formed therein and a lid substrate that covers the groove, and each substrate may be a glass substrate, a silicon substrate, or the like. Furthermore, in this embodiment, the distance between the first wall surface 21 and the second wall surface 22 of the flow channel 20, that is, the width along the Y axis (second axis), is formed to be the same. Note that it is sufficient that at least the width along the Y axis at the first position 20A where the first ultrasonic element 30 described below is provided and the width along the Y axis at the second position 20B where the second ultrasonic element 40 is provided are the same, and for example, the width along the Y axis may be wider or narrower between the first position 20A and the second position 20B. Furthermore, in the example shown in FIG. 1, the first position 20A is located downstream (+X side) of the second position 20B, but it may be located upstream of the second position 20B.

[0011] Although not shown, the flow path 20 is provided with an inlet for injecting the fluid S into the flow path 20 and one or more outlets for discharging the fluid S from the flow path 20. When the flow path 20 is provided with the concentration flow path and the discharge flow path as described above, an outlet is provided for each flow path.

[0012] The first ultrasonic element 30 constitutes the ultrasonic transmission unit of the present disclosure. This first ultrasonic element 30 is provided at a first position 20A of the flow channel 20 so as to face the inside of the flow channel 20, and generates a standing wave SW along the Y-axis in the fluid S by transmitting ultrasonic waves of a predetermined frequency to the fluid S. In this embodiment, the ultrasonic transmission surface 30S of the first ultrasonic element 30 constitutes a part of the first wall surface 21 of the flow channel 20, and generates a standing wave SW along the Y-axis direction.

[0013] The second ultrasonic element 40, together with the first ultrasonic element 30, constitutes the ultrasonic transmission unit of the present disclosure. This second ultrasonic element 40 is disposed at a second position 20B that is different from the first position 20A where the first ultrasonic element 30 is disposed in the flow channel 20. The second ultrasonic element 40 transmits ultrasonic waves of an arbitrary frequency to the fluid S in the flow channel 20. In this embodiment, the ultrasonic transmission surface 40S of the second ultrasonic element 40 constitutes a part of the first wall surface 21 of the flow channel 20.

[0014] The specific configuration of each ultrasonic element constituting the first ultrasonic element 30 or the second ultrasonic element 40 is not particularly limited. For example, the ultrasonic element may have a configuration that vibrates a piezoelectric actuator, a configuration that vibrates a vibration plate on which a piezoelectric thin film is formed, or a configuration that vibrates a vibration plate included in an electrostatic actuator. Such ultrasonic elements vibrate when a drive signal (voltage) of a predetermined drive frequency is applied, and transmit ultrasonic waves. Furthermore, the relative position of the second position 20B where the second ultrasonic element 40 is provided relative to the first position 20A where the first ultrasonic element 30 is provided is not particularly limited. However, it is preferable that the second ultrasonic element 40 is far enough from the first ultrasonic element 30 that it does not affect the generation of the standing wave SW. It is also preferable that the temperatures of the fluid S flowing through the first position 20A and the fluid S flowing through the second position 20B are approximately the same. For example, the first position 20A and the second position 20B are located within a distance range that does not cause a temperature difference between the first position 20A and the second position 20B. Note that when the distance between the first position 20A and the second position 20B is large, it is preferable that the ambient environment is set so that the temperatures of the fluid S are approximately the same at the first position 20A and the second position 20B.

[0015] The control unit 50 includes a continuous wave generating circuit 51, an impedance measuring circuit 52, a memory 53, and one or more processors 54 that control the first ultrasonic element 30 and the second ultrasonic element 40 via each circuit.

[0016] The continuous wave generating circuit 51 corresponds to the first driving unit of the present disclosure, and generates a first drive signal to be output to the first ultrasonic element 30. This continuous wave generating circuit 51 is a circuit that can change the drive frequency of the first drive signal to be output, and forms a first drive signal with the drive frequency set to a predetermined first drive frequency Fd under the control of the processor 54, and outputs it continuously to the first ultrasonic element 30.

[0017] The impedance measurement circuit 52 corresponds to the second drive unit of the present disclosure, and generates a second drive signal to be output to the second ultrasonic element 40. This continuous wave generation circuit 51 is a circuit that can change the drive frequency of the second drive signal to be output, and forms a drive signal of any drive frequency in response to a measurement command from the processor 54, and outputs it to the second ultrasonic element 40. The impedance measurement circuit 52 also measures the impedance of the second ultrasonic element 40. For example, the impedance measurement circuit 52 has an ammeter that measures the value of the current flowing through the second ultrasonic element 40, and measures the impedance of the second ultrasonic element 40 based on the voltage value of the second drive signal applied to the second ultrasonic element 40 and the current value measured by the ammeter.

[0018] The memory 53 is a storage device that stores various programs and various data. For example, the memory 53 stores the value of the first drive frequency Fd of the current first drive signal of the first ultrasonic element 30, etc. By executing a program stored in the memory 53, the processor 54 functions as a measurement control unit 541 that outputs a measurement command to the impedance measurement circuit 52 and a drive control unit 542 that controls the first drive frequency Fd of the first ultrasonic element 30.

[0019] (Control mechanisms of fluidic devices) Next, a mechanism and method for capturing the particle M at the node of the standing wave SW at the first position 20A of the flow channel 20 in the fluidic device 10 of this embodiment will be described. If the frequency of the ultrasonic waves transmitted to the fluid is f, the order of the standing wave formed by the ultrasonic waves is m, the speed of sound in the fluid is c, and the width of the flow path along the Y axis is L, then in order to form a standing wave SW at the first position 20A, the frequency f of the ultrasonic waves output from the first ultrasonic element 30 must satisfy the condition of the following equation (1).

[0020]

number

[0021] Here, when the temperature in the fluid changes, the speed of sound c in the fluid S changes, and therefore the frequency f for forming the standing wave SW also changes.

[0022] On the other hand, when a standing wave SW is formed in the flow path 20, the sound pressure increases at the antinode positions of the standing wave SW. Therefore, the impedance when driving the first ultrasonic element 30 and the second ultrasonic element 40 also increases. FIG. 2 is a diagram showing the change in impedance of the second ultrasonic element 40 when the drive frequency of the second drive signal is changed. 2, by increasing the drive frequency of the second drive signal, the impedance of the second ultrasonic element 40 gradually decreases, but peak points Pn (n=1, 2, 3, etc.) where the impedance reaches a maximum value appear at predetermined intervals. These peak points Pn are observed when a standing wave SW is formed in the flow path 20, and indicate that the antinode position where the sound pressure of the standing wave SW is maximum is located on the ultrasonic transmission surface 40S of the second ultrasonic element 40. That is, even if the sound speed c changes due to a change in the temperature of the fluid S, the optimal drive frequency for forming the standing wave SW can be identified by detecting the peak point Pn of the impedance of the second ultrasonic element 40. Furthermore, in this embodiment, the flow path width L at the second position 20B where the second ultrasonic element 40 is provided is the same as the flow path width L at the first position 20A where the first ultrasonic element 30 is provided, and the temperatures of the fluid S at the first position 20A and the second position 20B are also the same. Therefore, the drive frequency conditions for forming the standing wave SW at the second position 20B are the same as the drive frequency conditions for forming the standing wave SW at the first position 20A.

[0023] (Method for controlling a fluid device) Next, a method for controlling the fluidic device 10 of this embodiment will be described. FIG. 3 is a flowchart showing a method for controlling the fluidic device 10 of this embodiment.

[0024] In this embodiment, the frequency of the ultrasonic waves output from the first ultrasonic element 30 is feedback-controlled based on the impedance measurement results of the second ultrasonic element 40. The impedance of the second ultrasonic element 40 may be measured at regular intervals, for example, when the fluidic device 10 is started up. In the example shown in FIG. 3, the impedance of the second ultrasonic element 40 is measured at regular intervals. That is, the drive control unit 542 of the control unit 50 reads out the first drive frequency Fd recorded in the memory 53, and outputs a drive command to the continuous wave generating circuit 51 to drive the first ultrasonic element 30 with a first drive signal of the first drive frequency Fd (step S1). As a result, the continuous wave generating circuit 51 continues to output the first drive signal of the first drive frequency Fd to the first ultrasonic element 30, and a continuous wave of the first drive frequency is transmitted from the first ultrasonic element 30 to the fluid S (step S2). At this time, if the first drive frequency Fd satisfies the optimum condition for forming the standing wave SW, the particle M is captured at the node position of the standing wave SW formed at the first position 20A.

[0025] Then, when a predetermined measurement timing has arrived (step S3; Yes), the measurement control unit 541 outputs an impedance measurement command to the impedance measurement circuit 52 and measures the change in impedance in the second ultrasonic element 40 (step S4). If it is not the measurement timing, the measurement control unit 541 continues transmitting the continuous wave in step S2. When a measurement command is input, the impedance measurement circuit 52 outputs a second drive signal to the second ultrasonic element 40 and changes the drive frequency of the second drive signal within a predetermined range. Then, the impedance measurement circuit 52 measures the change in impedance of the second ultrasonic element 40 due to the change in the drive frequency of the second drive signal. Here, "within a predetermined range" refers to a range according to the order m of the standing wave SW formed in the flow path 20. Fig. 4 is a diagram showing the relationship between the drive frequency and the impedance of the second ultrasonic element 40 when the temperature of the fluid S is changed. For example, in Fig. 2, when a standing wave SW with an order m of 3 is formed, a peak point P3 appears near 1570 kHz. If the temperature of the fluid S changes, the drive frequency corresponding to peak point P3 also changes, but the range of frequency change is approximately ±10 kHz, as shown in Fig. 4. Therefore, in this case, the drive frequency may be changed within the predetermined range of 1560 kHz to 1580 kHz. The predetermined range of the drive frequency of the second drive signal can be set appropriately depending on the allowable temperature range of the fluid S flowing through the flow path 20 and the order m of the peak point to be detected. For example, if the allowable temperature range of the fluid S flowing through the flow path 20 is 20°C to 40°C and the order m is 3, the drive frequency can be changed within a range of ±10 kHz centered around 1570 kHz, as shown in Figure 4. Furthermore, if the allowable temperature range of the fluid S is to be wider, the range of change in the drive frequency of the second drive signal can be wider. Furthermore, when changing the drive frequency of the second drive signal, the impedance measurement circuit 52 may, for example, sweep the drive frequency within a predetermined range, or may change it sequentially at predetermined intervals (for example, 1 kHz intervals) that are set in advance.

[0026] Then, the measurement control unit 541 identifies the drive frequency (second drive frequency Fs) of the second drive signal at the timing when the impedance of the second ultrasonic element 40 becomes maximum, based on the impedance measurement result output from the impedance measurement circuit 52 (step S5). As described above, if the change range of the drive frequency is small (a narrow range of about ±10 kHz), the drive frequency at which the impedance becomes maximum may be identified as the second drive frequency Fs. Note that if the change range of the drive frequency is wider, for example, if the drive frequency is changed in a range from 500 kHz to 3000 kHz, multiple maximum values ​​(peak points Pn) may be detected from the change in impedance, and the second drive frequency Fs corresponding to the desired order m may be identified from each peak point Pn.

[0027] Then, the drive control section 542 determines whether the current first drive frequency Fd matches the second drive frequency Fs identified in step S5 (step S6). Here, "match" means that the first drive frequency Fd and the second drive frequency Fs match perfectly, as well as including a slight error within the range in which a standing wave SW is formed. That is, in step S6, it is determined that the two match if |Fd - Fs| is within a preset error range.

[0028] If the determination in step S6 is No, the drive control unit 542 rewrites and updates the first drive frequency Fd recorded in the memory 53 with the second drive frequency Fs identified in step S5 (step S7), and returns to step S1. That is, in step S1, the first ultrasonic element 30 is driven at the updated first drive frequency Fd. As a result, in step S2, the first ultrasonic element 30 is driven at the optimal first drive frequency Fd for forming the standing wave SW.

[0029] If the determination in step S6 is Yes, the first ultrasonic element 30 continues to be driven by the first drive signal at the current first drive frequency Fd. In other words, the first ultrasonic element 30 continues to be driven in step S2 without updating the first drive frequency Fd. Then, the control unit 50 determines whether or not to continue forming the standing wave SW (step S8). For example, if an input to end the process is received through a user setting input or the like, the determination in step S8 is No, and the driving of the fluid device 10 is stopped. If the determination in step S8 is Yes, the process returns to step S2. That is, the driving of the first ultrasonic element 30 in step S2 continues. In FIG. 3, the process of step S8 is performed after the determination in step S6 is Yes, but step S8 may be performed at any timing.

[0030] 3, in step S1, the first drive frequency Fd stored in the memory 53 is read out and the first ultrasonic element 30 is driven. That is, immediately after starting up the fluidic device 10, the fluidic device 10 is driven at the first drive frequency Fd measured during the previous operation of the fluidic device 10. However, before step S1, the processes of steps S4 to S7 may be performed to initially set the optimal first drive frequency Fd for forming the standing wave SW.

[0031] (Effects of this embodiment) The fluidic device 10 of this embodiment includes a flow path 20 that extends along the X-axis (first axis) and through which a fluid S flows, a first ultrasonic element 30 and a second ultrasonic element 40 that are disposed in the flow path 20 and transmit ultrasonic waves into the flow path 20 along the Y-axis (second axis) in response to input of a drive signal, and a control unit 50. The control unit 50 measures the impedance of the second ultrasonic element 40 when the second ultrasonic element 40 is driven by changing the drive frequency of the second drive signal within a predetermined range, identifies the drive frequency at which the impedance is maximized, sets this as the first drive frequency, and inputs the first drive signal of the first drive frequency to the first ultrasonic element 30. The fluidic device 10 generates a standing wave SW in the fluid S in the flow path 20 using the first ultrasonic element 30. However, if the temperature of the fluid S changes, the speed of sound in the fluid S changes, and the conditions for forming the standing wave SW also change. Therefore, in this embodiment, as described above, the impedance of the second ultrasonic element 40 is measured while changing the drive frequency of the second ultrasonic element 40. In this case, the drive frequency (second drive frequency Fs) at which the impedance is maximized can be identified as the first drive frequency Fd for forming the standing wave SW. Therefore, even if the temperature of the fluid changes and the speed of sound fluctuates, the drive frequency of the first drive signal of the first ultrasonic element 30 can be feedback-controlled in response to the temperature change. As a result, the standing wave SW can be stably generated even if the temperature of the fluid changes.

[0032] In this embodiment, the first ultrasonic element 30 is provided at a first position 20A of the flow path 20 and transmits ultrasonic waves along the Y axis in response to an input of a first drive signal. The second ultrasonic element 40 is provided at a second position 20B of the flow path 20 and transmits ultrasonic waves along the Y axis in response to an input of a second drive signal. The first position 20A and the second position 20B of the flow path 20 have the same flow path width L. As described above, the control unit 50 measures the impedance of the second ultrasonic element 40 by varying the drive frequency of the second drive signal input to the second ultrasonic element 40 within a predetermined range, and identifies the drive frequency (second drive frequency Fs) at which the impedance is maximized, and sets this as the first drive frequency Fd. In other words, if the first drive frequency Fd already stored in the memory 53 does not match the identified second drive frequency Fs, the control unit 50 records the identified second drive frequency Fs in the memory 53 as a new first drive frequency Fd. The control unit 50 then inputs a first drive signal of the new first drive frequency Fd to the first ultrasonic element 30. In the flow path 20, the flow path width L is the same at the first position 20A where the first ultrasonic element 30 is provided and the second position 20B where the second ultrasonic element 40 is provided, and therefore, as shown in formula (1), the frequency f of the ultrasonic waves for forming the standing wave SW at the first position 20A is the same as the frequency f of the ultrasonic waves for forming the standing wave at the second position 20B. Therefore, the first drive frequency Fd for driving the first ultrasonic element 30 can be set based on the impedance of the second ultrasonic element 40 provided at the second position 20B. In this way, by separating the second ultrasonic element 40 that measures the impedance from the first ultrasonic element 30 that forms the standing wave SW, it is possible to measure the impedance at the second ultrasonic element 40 while continuing to form the standing wave SW at the first position 20A, and to perform feedback control of the first ultrasonic element 30 based on the measurement results.

[0033] In this embodiment, the control unit 50 includes a continuous wave generating circuit 51, which is a first driving unit, and an impedance measuring circuit 52, which is a second driving unit. The continuous wave generating circuit 51 is a circuit that outputs a first driving signal to the first ultrasonic element 30 and is capable of changing the driving frequency of the first driving signal. The impedance measuring circuit 52 is a circuit that outputs a second driving signal to the second ultrasonic element 40 and is capable of changing the driving frequency of the second driving signal within a predetermined range, and measures the impedance of the second ultrasonic element 40 when the driving frequency of the second driving signal is changed within the predetermined range. In this embodiment, the impedance of the second ultrasonic element 40 can be measured by the impedance measurement circuit 52 while the first ultrasonic element 30 is driven by the continuous wave generation circuit 51. That is, in this embodiment, feedback control can be performed based on the impedance of the second ultrasonic element 40 provided at the second position 20B while continuing to form the standing wave SW at the first position 20A.

[0034] Furthermore, in this embodiment, by using water as the fluid S, a fluidic device 10 capable of appropriately separating fine particles M contained in water can be provided, thereby broadening the scope of applications. For example, by flowing domestic wastewater discharged from a washing machine or a kitchen into the fluidic device 10, the fine particles contained in the domestic wastewater can be separated. In this case, fine plastic fibers contained in laundry water and abrasive powder from detergent contained in kitchen wastewater can be separated, making it possible to reduce environmental damage caused by substances such as plastic waste. However, the fluid S is not limited to water. For example, by using blood as the fluid S, a fluidic device 10 capable of separating cellular components contained in blood can be provided. If the cellular components are cancer cells in the blood, the cancer cells contained in the blood can be separated and removed, making it possible to suppress cancer metastasis.

[0035] [Second embodiment] Next, a fluidic device according to a second embodiment will be described. In the first embodiment described above, an example was shown in which the ultrasonic transmission unit of the present disclosure includes the first ultrasonic element 30 and the second ultrasonic element 40, the first ultrasonic element 30 generates a standing wave SW in the flow path 20, and the optimal drive frequency is identified using the impedance of the second ultrasonic element 40. In contrast, the second embodiment differs from the first embodiment in that the ultrasonic transmission unit is composed of a single ultrasonic element.

[0036] 5 is a diagram schematically showing a fluidic device 10A according to the second embodiment. In the following description, the same reference numerals will be used to designate components that have already been described, and their description will be omitted or simplified. Similar to the first embodiment, the fluidic device 10A has a flow path 20, and a third ultrasonic element 60 having the same configuration as the first ultrasonic element 30 is provided at a predetermined position in the flow path 20. That is, the third ultrasonic element 60 is provided on a first wall surface 21 of the flow path 20 so that an ultrasonic transmission surface 60S forms part of the first wall surface 21, and transmits ultrasonic waves along the Y-axis toward the second wall surface 22.

[0037] The control unit 50A includes a continuous wave generating circuit 51, an impedance measuring circuit 52, a memory 53, a processor 54, and a switch unit 55. The switch unit 55 is connected to the continuous wave generating circuit 51, the impedance measuring circuit 52, and the third ultrasonic element 60. The switch unit 55 is switchable between a drive mode connection that connects the continuous wave generating circuit 51 and the third ultrasonic element 60, and a measurement mode connection that connects the impedance measuring circuit 52 and the third ultrasonic element 60, and switches these connections under the control of the processor 54.

[0038] The processor 54 executes the programs stored in the memory 53 to function as a measurement control unit 541 , a drive control unit 542 , and a mode switching unit 543 . In this embodiment, the mode switching unit 543 switches the connection state of the switch unit 55 between a measurement mode connection and a drive mode connection. Then, when the mode switching unit 543 switches the switch unit 55 to the measurement mode connection, the measurement control unit 541 outputs a measurement command to the impedance measurement circuit 52. As a result, the impedance measurement circuit 52 sweeps the drive frequency of the drive signal input to the third ultrasonic element 60 within a predetermined range, and measures the impedance of the third ultrasonic element 60. Furthermore, when the mode switching unit 543 switches the switch unit 55 to the drive mode connection, the drive control unit 542 outputs a drive command to the continuous wave generating circuit 51 to output a drive signal of the first drive frequency Fd to the third ultrasonic element 60. As a result, ultrasonic waves of an optimum drive frequency for forming a standing wave SW are output from the third ultrasonic element 60.

[0039] (Method for controlling a fluid device) Next, a method for controlling the fluidic device 10A of the second embodiment will be described below. Fig. 6 is a flowchart showing the method for controlling the fluidic device 10A of the second embodiment.

[0040] In this embodiment, the frequency of the ultrasonic waves output from the third ultrasonic element 60 is feedback-controlled based on the impedance measurement results measured in the measurement mode. The impedance of the third ultrasonic element 60 may be measured at regular intervals, for example, when the fluidic device 10 is started up. In the example shown in FIG. 6, the impedance of the third ultrasonic element 60 is measured at regular intervals.

[0041] In this embodiment, first, the mode switching unit 543 switches the operation mode to the drive mode. That is, the mode switching unit 543 switches the switch unit 55 to the drive mode connection and connects the third ultrasonic element 60 and the continuous wave generating circuit 51 (step S11). Thereafter, similar to step S1 in the first embodiment, the drive control unit 542 reads out the first drive frequency Fd recorded in the memory 53, and outputs a drive command to the continuous wave generating circuit 51 to drive the third ultrasonic element 60 with a drive signal of the first drive frequency Fd (step S12). As a result, similar to step S2, the continuous wave generating circuit 51 continues to output the first drive signal of the first drive frequency Fd to the third ultrasonic element 60, and a continuous wave of the first drive frequency Fd is transmitted from the third ultrasonic element 60 to the fluid S (step S13).

[0042] Thereafter, the mode switching unit 543 determines whether a predetermined measurement timing has arrived (step S14), and when the measurement timing has arrived (step S14: Yes), switches the operation mode to the measurement mode. That is, the mode switching unit 543 switches the switch unit 55 to the measurement mode connection, and connects the third ultrasonic element 60 and the impedance measurement circuit 52 (step S15). Then, similar to step S4, the measurement control unit 541 outputs an impedance measurement command to the impedance measurement circuit 52, and measures the change in impedance in the third ultrasonic element 60 (step S16). Furthermore, similar to step S5, the measurement control unit 541 determines the drive frequency (second drive frequency Fs) of the drive signal that was output to the third ultrasonic element 60 at the time when the impedance of the third ultrasonic element 60 became maximum based on the impedance measurement result output from the impedance measurement circuit 52 (step S17).

[0043] After this, the same processes as steps S6 to S8 of the first embodiment are performed. That is, in step S6, it is determined whether the current first drive frequency Fd matches the second drive frequency Fs identified in step S17. If the determination in step S6 is No, in step S7, the first drive frequency Fd recorded in the memory 53 is updated, and the process returns to step S11. As a result, after switching to the drive mode in step S11, a drive command to drive the third ultrasonic element 60 at the updated first drive frequency Fd is output to the continuous wave generating circuit 51 in step S12, and a standing wave SW is formed in the fluid S by the third ultrasonic element 60 in step S13.

[0044] If the determination in step S6 is Yes, the process in step S8 determines whether or not to continue forming the standing wave SW, and if it is to be continued (step S8: Yes), the process returns to step S11. That is, the first drive frequency Fd is not updated, and the operation mode is switched to the drive mode. Note that, as in the first embodiment, the process in step S8 may be performed at any timing. 6, after the drive mode is implemented in steps S11 to S13, the processes of steps S14 to S17 and steps S6 to S7 are implemented, but this is not limiting. For example, before step S11, step S14 may be implemented to switch to the measurement mode, and the impedance measurement process of steps S13 to S17 and the update process of the first drive frequency of steps S6 to S7 may be implemented, and then the process of switching to the drive mode in step S11 may be implemented.

[0045] (Effects of this embodiment) In the fluidic device 10A of this embodiment, the ultrasonic transmission unit is composed of a single third ultrasonic element 60. The control unit 50A operates in a measurement mode in which the drive frequency of a drive signal is changed within a predetermined range and input to the third ultrasonic element 60, and a drive mode in which the drive signal is input to the third ultrasonic element 60 at a fixed drive frequency. In the measurement mode, the impedance of the third ultrasonic element 60 is measured, and the drive frequency at which the impedance is maximized is identified and set as the first drive frequency. In the drive mode, a drive signal of the first drive frequency Fd set in the measurement mode is input to the third ultrasonic element 60. In this case, a single third ultrasonic element 60 can be used to form a standing wave SW and measure impedance to set an optimal drive frequency (first drive frequency Fd), thereby simplifying the configuration of the ultrasonic device.

[0046] In this embodiment, the control unit 50A includes a continuous wave generating circuit 51, an impedance measuring circuit 52, and a switch unit 55. As a result, by switching the switch unit 55 to the drive mode connection, the third ultrasonic element 60 can form a standing wave SW in the flow path 20, and by switching the switch unit 55 to the measurement mode connection, the impedance of the third ultrasonic element 60 can be measured and the first drive frequency FD suitable for forming the standing wave SW can be identified.

[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] (Variation 1) In the first embodiment, the second drive frequency Fs based on the impedance measured by the second ultrasonic element 40 is stored in the memory 53 as the first drive frequency Fd, and the drive control unit 542 reads out the first drive frequency Fd to drive the first ultrasonic element 30, but this is not limiting. Once the second drive frequency Fs is obtained, the drive control unit 542 may output a drive command to the continuous wave generating circuit 51 with the second drive frequency Fs as the first drive frequency Fd.

[0049] (Variation 2) In the first embodiment, the first ultrasonic element 30 and the second ultrasonic element 40 are provided on the first wall surface 21, and in the second embodiment, the third ultrasonic element 60 is provided on the first wall surface 21, but this is not limited to this. For example, the first ultrasonic element 30, the second ultrasonic element 40, and the third ultrasonic element 60 may be provided on the second wall surface 22. Furthermore, when ultrasonic waves are transmitted from the first ultrasonic element 30, the second ultrasonic element 40, and the third ultrasonic element 60, the ultrasonic waves propagate by diffusing and spreading around the ultrasonic transmission surfaces 30S, 40S, and 60S. Therefore, the first ultrasonic element 30, the second ultrasonic element 40, and the third ultrasonic element 60 may be configured to be provided on a side surface perpendicular to the first wall surface 21 and the second wall surface 22, for example, on the bottom surface of a groove in the base substrate or on the lid substrate. In this case, the first ultrasonic element 30, the second ultrasonic element 40, and the third ultrasonic element 60 may be provided so as to be positioned at the antinodes of the standing wave SW.

[0050] (Variation 3) In the first embodiment, the first ultrasonic element 30 and the second ultrasonic element 40 each form a flow path wall surface of the flow path 20, but are not limited to this. For example, a wall member of the flow path 20 may be disposed between the first ultrasonic element 30 and the fluid S, or a wall member of the flow path 20 may be disposed between the second ultrasonic element 40 and the fluid S. The same applies to the third ultrasonic element 60 in the second embodiment.

[0051] Summary of this disclosure A fluidic device of a first aspect according to the present disclosure comprises a flow path extending along a first axis and through which a fluid flows, an ultrasonic transmitter disposed in the flow path and configured to transmit ultrasonic waves into the flow path along a second axis perpendicular to the first axis upon input of a drive signal, and a control unit for controlling the ultrasonic transmitter, wherein the control unit measures the impedance of the ultrasonic transmitter when the ultrasonic transmitter is driven by changing the drive frequency of the drive signal within a predetermined range, identifies the drive frequency at which the impedance is maximized, sets this as a first drive frequency, and inputs the drive signal of the first drive frequency to the ultrasonic transmitter. When a standing wave is formed by an ultrasonic transmitter, the ultrasonic transmitter is located at the antinode of the standing wave. Since the sound pressure is maximized at the antinode of the standing wave, the resistance (impedance) when driving the ultrasonic transmitter is also maximized. Therefore, as described above, by measuring the impedance of the ultrasonic transmitter while changing the drive frequency of the ultrasonic transmitter, it is possible to determine whether a standing wave is formed. In other words, when the ultrasonic transmitter is driven at a drive frequency that maximizes the impedance, it is possible to determine that a standing wave is formed in the flow path and that the sound pressure is maximized at the ultrasonic transmitter. Therefore, even if the temperature of the fluid changes and the speed of sound fluctuates, the first drive frequency of the drive signal for forming the standing wave can be identified, and the frequency of the ultrasonic waves transmitted from the ultrasonic transmitter can be feedback-controlled in response to temperature changes. As a result, a standing wave can be stably generated even when the temperature of the fluid changes.

[0052] In the fluid device of the first aspect, the ultrasonic transmission unit includes a first ultrasonic element that is provided at a first position in the flow path and that transmits ultrasonic waves along the second axis in response to input of a first drive signal, and a second ultrasonic element that is provided at a second position in the flow path that is different from the first position in a direction along the first axis and that transmits ultrasonic waves along the second axis in response to input of a second drive signal, wherein the flow path has a width along the second axis at the first position and a width along the second axis at the second position that are the same, and the control unit measures the impedance of the second ultrasonic element when the second ultrasonic element is driven by changing the drive frequency of the second drive signal input to the second ultrasonic element within the predetermined range, sets the drive frequency at which the impedance of the second ultrasonic element is maximized as the first drive frequency, and sets the drive frequency of the first drive signal to the first drive frequency and inputs it to the first ultrasonic element. In this aspect, the flow path width along the second axis is the same at the first position where the first ultrasonic element is provided and the second position where the second ultrasonic element is provided, and the conditions for forming a standing wave are the same at the first position and the second position. Therefore, by measuring the change in impedance of the second ultrasonic element when the drive frequency of the second drive signal input to the second ultrasonic element is changed, the conditions for forming a standing wave at the first position can be identified. In other words, by identifying the drive frequency at which the impedance of the second ultrasonic element is maximized as the first drive frequency and applying the first drive signal of the first drive frequency to the first ultrasonic element, a standing wave can be properly formed at the first position. In this way, by separating the second ultrasonic element that measures the impedance from the first ultrasonic element that forms the standing wave, it is possible to measure the impedance with the second ultrasonic element while continuing to form the standing wave at the first position, and perform feedback control of the first ultrasonic element based on the measurement results.

[0053] In the fluid device of the first aspect, the control unit includes a first drive unit that outputs the first drive signal and is capable of changing the drive frequency of the first drive signal, and is connected to the first ultrasonic element; and a second drive unit that outputs the second drive signal and is capable of changing the drive frequency of the second drive signal, and is connected to the second ultrasonic element, and measures the impedance of the second ultrasonic element when the drive frequency of the second drive signal is changed within the predetermined range. As described above, when a first ultrasonic element and a second ultrasonic element are provided in the flow path, the control unit is provided with a first drive unit for driving the first ultrasonic element and a second drive unit for driving the second ultrasonic element and measuring the impedance of the second ultrasonic element. By separating the first drive unit for driving the first ultrasonic element from the second drive unit for driving the second ultrasonic element in this way, it is possible to measure the impedance of the second ultrasonic element while continuing to form a standing wave by the first ultrasonic element at the first position.

[0054] In the fluid device of the first aspect, the ultrasonic transmitting unit is a single ultrasonic element, and the control unit implements a measurement mode in which the drive frequency of the drive signal is changed within the predetermined range and input to the ultrasonic element, and a drive mode in which the drive frequency of the drive signal is fixed and input to the ultrasonic element, and in the measurement mode, the impedance of the ultrasonic element is measured, and the drive frequency at which the impedance is maximized is identified and set as the first drive frequency, and in the drive mode, the drive frequency of the drive signal is fixed to the first drive frequency and input to the ultrasonic element. In this case, the formation of a standing wave and the measurement of impedance for setting an optimum drive frequency can be performed using a single ultrasonic element, thereby simplifying the configuration of the ultrasonic device.

[0055] In the first embodiment of the fluidic device, the control unit includes a first drive unit that outputs the drive signal and is capable of changing the drive frequency of the drive signal, a second drive unit that outputs the drive signal and is capable of changing the drive frequency of the drive signal and measures the impedance of the ultrasonic transmission unit when the drive frequency of the drive signal is changed within the specified range, and a switch unit that is connected to the first drive unit, the second drive unit, and the ultrasonic transmission unit and is capable of switching between a drive mode connection that connects the first drive unit and the ultrasonic transmission unit and a measurement mode connection that connects the second drive unit and the ultrasonic transmission unit. As described above, when the ultrasonic transmission unit is configured with one ultrasonic element, the control unit is provided with a first drive unit for forming a standing wave, a second drive unit for measuring impedance, and a switch unit. As a result, by switching the switch unit to a drive mode connection, a standing wave can be formed in the flow path by the ultrasonic element, and by switching the switch unit to a measurement mode connection, the impedance of the ultrasonic element can be measured and a first drive frequency suitable for forming a standing wave can be identified.

[0056] A second aspect of the control method for a fluidic device according to the present disclosure is a control method for a fluidic device that captures microparticles in a fluid flowing inside a flow path extending along a first axis, and includes an ultrasonic transmitting unit that is arranged in the flow path and transmits ultrasonic waves into the flow path along a second axis perpendicular to the first axis upon input of a drive signal, and measures the impedance of the ultrasonic transmitting unit when the drive frequency of the drive signal is changed within a predetermined range to drive the ultrasonic transmitting unit, identifies the drive frequency at which the impedance is maximized and sets it as a first drive frequency, and inputs the drive signal of the first drive frequency to the ultrasonic transmitting unit. As a result, similar to the first aspect of the present disclosure, standing waves can be generated stably even when the temperature of the fluid changes.

[0057] In a second aspect of the method for controlling a fluidic device, the ultrasonic transmission unit includes a first ultrasonic element that is provided at a first position in the flow path and that transmits ultrasonic waves along the second axis in response to input of a first drive signal, and a second ultrasonic element that is provided at a second position in the flow path that is different from the first position in a direction along the first axis and that transmits ultrasonic waves along the second axis in response to input of a second drive signal, wherein the flow path has the same width along the second axis at the first position and the same width along the second axis at the second position, and the impedance of the second ultrasonic element is measured when the drive frequency of the second drive signal input to the second ultrasonic element is changed within the predetermined range to drive the second ultrasonic element, and the drive frequency at which the impedance is maximized is set to the first drive frequency, and the drive frequency of the first drive signal is set to the first drive frequency and input to the first ultrasonic element. This allows the second ultrasonic element that measures the impedance to be separated from the first ultrasonic element that forms the standing wave, so that the impedance can be measured using the second ultrasonic element while continuing to form the standing wave at the first position, and feedback control of the first ultrasonic element can be performed based on the measurement results.

[0058] In the second aspect of the control method for a fluid device, the ultrasonic transmitting unit is a single ultrasonic element, and a measurement mode is implemented in which the drive frequency of the drive signal is changed within the predetermined range and input to the ultrasonic element, and a drive mode is implemented in which the drive frequency of the drive signal is fixed and input to the ultrasonic element, and in the measurement mode, the impedance of the ultrasonic element is measured, and the drive frequency at which the impedance is maximized is identified and set as the first drive frequency, and in the drive mode, the drive frequency of the drive signal is fixed to the first drive frequency and input to the ultrasonic element. This allows the formation of a standing wave and the measurement of impedance for setting an optimal drive frequency to be performed using a single ultrasonic element, thereby simplifying the configuration of the ultrasonic device. [Explanation of symbols]

[0059] 10, 10A...fluidic device, 20...flow path, 20A...first position, 20B...second position, 21...first wall surface, 22...second wall surface, 30...first ultrasonic element, 30S...ultrasonic transmission surface, 40...second ultrasonic element, 40S...ultrasonic transmission surface, 50, 50A...control unit, 51...continuous wave generating circuit, 52...impedance measurement circuit, 53...memory, 54...processor, 55...switch unit, 60...third ultrasonic element, 60S...ultrasonic transmission surface, 541...measurement control unit, 542...drive control unit, 543...mode switching unit, L...flow path width, M...microparticle, SW...standing wave.

Claims

1. a channel extending along a first axis and through which a fluid flows; an ultrasonic wave transmitting unit disposed in the flow channel and transmitting an ultrasonic wave into the flow channel along a second axis perpendicular to the first axis in response to an input of a drive signal; a control unit that controls the ultrasonic wave transmitting unit, The ultrasonic wave transmitting unit a first ultrasonic element provided at a first position in the flow channel, the first ultrasonic element transmitting an ultrasonic wave along the second axis in response to an input of a first drive signal; a second ultrasonic element that is provided at a second position in the flow path that is different from the first position in a direction along the first axis, and that transmits an ultrasonic wave along the second axis in response to an input of a second drive signal; the flow path has a width along the second axis at the first position that is the same as a width along the second axis at the second position; The control unit By continuing to output the first drive signal to the first ultrasonic element, a continuous wave is transmitted from the first ultrasonic element; A fluidic device that measures the impedance of the second ultrasonic element when the drive frequency of the second drive signal is changed within a predetermined range to drive the second ultrasonic element, identifies the drive frequency at which the impedance is maximized and sets it as a first drive frequency, and inputs the first drive signal of the first drive frequency to the first ultrasonic element.

2. The control unit a first driving unit that outputs the first drive signal, is capable of changing a drive frequency of the first drive signal, and is connected to the first ultrasonic element; a second driving unit that outputs the second drive signal, is capable of changing the drive frequency of the second drive signal, is connected to the second ultrasonic element, and measures the impedance of the second ultrasonic element when the drive frequency of the second drive signal is changed within the predetermined range; The fluidic device according to claim 1 .

3. A method for controlling a fluidic device that captures particles in a fluid flowing through an interior of a channel extending along a first axis, comprising: an ultrasonic transmission unit disposed in the flow path and transmitting an ultrasonic wave into the flow path along a second axis perpendicular to the first axis in response to an input of a drive signal; The ultrasonic wave transmitting unit a first ultrasonic element provided at a first position in the flow channel, the first ultrasonic element transmitting an ultrasonic wave along the second axis in response to an input of a first drive signal; a second ultrasonic element that is provided at a second position in the flow path that is different from the first position in a direction along the first axis, and that transmits an ultrasonic wave along the second axis in response to an input of a second drive signal; the flow path has a width along the second axis at the first position that is the same as a width along the second axis at the second position; By continuing to output the first drive signal to the first ultrasonic element, a continuous wave is transmitted from the first ultrasonic element; A method for controlling a fluid device, comprising: measuring the impedance of the second ultrasonic element when the drive frequency of the second drive signal is changed within a predetermined range to drive the second ultrasonic element; identifying the drive frequency at which the impedance is maximized as a first drive frequency; and inputting the first drive signal of the first drive frequency to the first ultrasonic element.

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