JP2017020836A - Droplet detection device and droplet detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an accurate measurement of a droplet position without complicating a configuration.SOLUTION: A droplet detection device 100 comprises: a resilience wave device 1 that has an excitation electrode 102 provided on a piezoelectric substrate 101 and conveys a droplet on the piezoelectric substrate 101; power source circuits 3, 5 and 7 that apply an AC electric signal to the excitation electrode 102; a signal waveform measuring instrument 11 that measures a reflection signal of the AC electric signal in the excitation electrode 102; and a data processing unit 13 that detects a time lag between the reflection signal measured by the signal waveform measuring instrument 11 and the AC electric signal, and calculates a position of the droplet on the piezoelectric substrate 101 on the basis of the time lag. The data processing unit 13 is configured to use a computation expression having a propagation path of the reflection signal set to a path circulating the droplet via a surface on a side opposite an interface between the droplet and the piezoelectric substrate 101, and the interface between the droplet and the piezoelectric substrate 101, and thereby calculate the position thereof from the time lag.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a droplet detection apparatus and a droplet detection method for detecting a droplet using an acoustic wave device.

  In recent years, droplet manipulation technology using surface acoustic waves has been developed, and application of this technology to microfluidic systems and the like is expected. It is important to detect where a droplet is located during droplet operation. For example, in the spectroscopic method described in Patent Document 1 below, a droplet is conveyed using a surface acoustic wave, and when the droplet crosses the laser beam, a change in the amount of the laser beam is detected by a detector. To detect the position.

  As other techniques for measuring the position of a droplet in a droplet manipulation device using surface acoustic waves, those described in Non-Patent Documents 1 and 2 below are known. Non-Patent Document 1 below describes that the position of a droplet can be measured using a reflected wave from the droplet. Further, in Non-Patent Document 2 below, a surface acoustic wave is propagated in a direction orthogonal to the direction in which the droplet is conveyed, and the droplet position is determined by detecting the attenuation of the surface acoustic wave caused by the droplet crossing. Techniques for measuring have been proposed.

JP 2006-112790 A

Alan Renaudinet al., “Monitoring SAW-actuated microdroplets in view of biological applications”, Sensors and Actuators B 138 (2009), p. 374-382 Jonathan Bennes et al., “Detection and High-Precision Positioning of Liquid Droplets Using SAW Systems”, IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICICS, AND FREQUENCY CONTROL, October 2007, Vol. 54, no. 10, p. 2146-2151

  However, in the method described in Patent Document 1 described above, the apparatus configuration tends to be complicated because it is necessary to irradiate and detect a laser beam on the droplet. In addition, in the device described in Non-Patent Document 1 described above, since the droplet position is measured by detecting the time difference between the two reflected waves, the initial position of the droplet needs to be known, It is difficult to accurately measure the droplet position when the initial position is unknown. In the device described in Non-Patent Document 2 described above, it is necessary to add an excitation electrode for detecting a droplet position in addition to the excitation electrode for droplet conveyance, and the configuration tends to be complicated.

  Accordingly, the present invention has been made in view of the above problems, and provides a droplet detection device and a droplet detection method that enable accurate droplet position measurement without complicating the configuration. Objective.

  In order to solve the above problems, a droplet detection apparatus according to an embodiment of the present invention is provided with an excitation electrode for exciting a surface acoustic wave on a piezoelectric substrate and conveys the droplet on the piezoelectric substrate. A power supply circuit unit that applies an AC electrical signal having a predetermined frequency to the excitation electrode for a set time width, a detection circuit unit that measures a reflected signal of the AC electrical signal at the excitation electrode, and a reflection measured by the detection circuit unit An arithmetic circuit unit that detects a time difference between the signal and the AC electric signal and calculates a position of the droplet on the piezoelectric substrate based on the time difference. The arithmetic circuit unit sets the propagation path of the reflected signal between the droplet and the piezoelectric The position is calculated from the time difference by using an arithmetic expression set in a path for circulating the droplets via the surface opposite to the substrate interface and the interface between the droplets and the piezoelectric substrate.

  Alternatively, in the droplet detection method according to another aspect of the present invention, a liquid using an acoustic wave device that is provided with an excitation electrode for exciting a surface acoustic wave on a piezoelectric substrate and transports the droplet on the piezoelectric substrate. A method for detecting a droplet position, in which an AC electrical signal having a predetermined frequency is applied to an excitation electrode for a set time width, a reflected signal of the AC electrical signal at the excitation electrode is measured, and the measured reflected signal and an AC electrical signal are measured. The propagation path of the reflected signal is set to the path that circulates the droplet via the surface opposite to the interface between the droplet and the piezoelectric substrate and the interface between the droplet and the piezoelectric substrate. By using the equation, the position of the droplet on the piezoelectric substrate is calculated from the time difference.

  According to the droplet detection device and the droplet detection method of the above aspect, an AC electric signal having a predetermined frequency is applied to the excitation electrode on the piezoelectric substrate with a predetermined time width, and a reflected signal of the AC electric signal at the excitation electrode is measured. The time difference between the measured reflected signal and the AC electrical signal is detected, and a path for circulating the droplets via the surface of the droplet opposite to the piezoelectric substrate and the interface of the droplet on the piezoelectric substrate side is detected. The position of the droplet is calculated from the time difference using an arithmetic expression set in the propagation path of the reflected signal. Thus, since the position of the droplet is detected from the measurement result of the reflection signal using the excitation electrode for transporting the droplet, the apparatus configuration can be simplified. At the same time, the accuracy of the detection result of the droplet position is improved by calculating the position using an arithmetic expression in which the propagation path of the reflection signal is set to the path for circulating the droplet. As a result, accurate droplet position measurement can be realized without complicating the configuration.

  Here, the power supply circuit unit includes an AC signal generation circuit that generates an AC electric signal, a pulse signal generation circuit that repeatedly generates a pulse signal having a time width, and a synthesis circuit that superimposes the AC electric signal on the pulse signal. It is good as well. In this way, AC electric signals can be repeatedly generated in the set time width, and the measurement of the droplet position can be repeatedly executed.

  The pulse signal generation circuit may be configured to be able to variably set the time width of the pulse signal. In this case, the time width of the surface acoustic wave to be generated can be adjusted. As a result, it is possible to perform switching between droplet conveyance and droplet position measurement.

In addition, the arithmetic circuit unit includes a propagation speed (V _SAW ) of the surface acoustic wave on the piezoelectric substrate, a width (i) of the excitation electrode in the droplet transport direction, a tip of the excitation electrode on the droplet side and the excitation electrode of the droplet. The following equation (1) between the distance (l) to the side tip, the diameter (d) of the droplet, and the propagation velocity (V _l ) of the longitudinal wave in the droplet, and the time difference (Δt);


The distance (l) may be calculated using, and the position may be calculated based on the distance (l). In this case, the position is calculated using an arithmetic expression in which the length of a part of the propagation path of the reflected signal is set to the length of the path for circulating the droplet (d × (1 + π / 2)). , The accuracy of the detection result of the droplet position obtained from the distance (l) is improved.

  The arithmetic circuit unit may calculate the amount of the droplet from the time difference by using an arithmetic expression, or the arithmetic circuit unit may propagate the longitudinal wave in the droplet from the time difference by using the arithmetic expression. The velocity may be calculated, and the characteristics of the droplet may be calculated based on the propagation velocity. In this case, even when the amount of droplets or the characteristics of the droplets are unknown, they can be obtained using an acoustic wave device.

  The acoustic wave device may further include a transport path plate disposed via a liquid phase on a propagation surface on which the surface acoustic wave generated on the surface of the piezoelectric substrate propagates. By adopting such a configuration, it is possible to improve the efficiency of the droplet transport operation by eliminating the need to clean the piezoelectric substrate.

  According to the present invention, an accurate droplet position can be measured without complicating the configuration.

1 is a diagram illustrating a schematic configuration of a droplet detection device 100 according to a preferred embodiment of the present invention. (A) is the top view which looked at the elastic wave device 1 of FIG. 1 from the surface side of the piezoelectric substrate, (b) is sectional drawing along the II-II line of the elastic wave device 1 of (a). (A) is a graph which shows the time change of the voltage measured before arrange | positioning the droplet Dp on the piezoelectric substrate 101 of the acoustic wave device 1, (b) is on the piezoelectric substrate 101 of the acoustic wave device 1. FIG. It is a graph which shows the time change of the voltage measured after arrange | positioning the droplet Dp. FIG. 2 is a model diagram of the acoustic wave device 1 of FIG. 1 as viewed from a direction perpendicular to the transport direction of the droplet Dp and parallel to the piezoelectric substrate 101. It is the figure which expanded the part of the droplet Dp in the model figure of FIG. It is the graph which compared the relationship between the volume of the droplet Dp calculated by the arithmetic expression used in this embodiment, and time difference (DELTA) T with an actual measurement result. It is the graph which compared the relationship between the volume of the droplet Dp calculated by the arithmetic expression used in this embodiment, and time difference (DELTA) T with an actual measurement result. It is the graph which compared the relationship between the volume of the droplet Dp calculated by the arithmetic expression used in this embodiment, and time difference (DELTA) T with an actual measurement result. FIG. 4 is a side view of an acoustic wave device 1A according to a modification of the present invention from a direction perpendicular to the droplet Dp transport direction and parallel to the piezoelectric substrate 101. It is a figure which shows schematic structure of 100 A of droplet detection apparatuses containing the elastic wave device 1A of FIG. It is the top view which looked at the elastic wave device 1B concerning the modification of this invention from the surface side of the piezoelectric substrate. (A) is the top view which looked at the elastic wave device 1C concerning the modification of this invention from the surface side of a piezoelectric substrate, (b) is the cross section along the XII-XII line | wire of the elastic wave device 1C of (a). FIG.

  Hereinafter, preferred embodiments of a droplet detection device and a droplet detection method according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Each drawing is made for the purpose of explanation, and is drawn so as to particularly emphasize the target portion of the explanation. Therefore, the dimensional ratio of each member in the drawings does not necessarily match the actual one.

  An acoustic wave device provided in a droplet detection apparatus according to a preferred embodiment of the present invention is an apparatus that conveys a droplet in a predetermined direction using a surface acoustic wave. Here, the surface acoustic wave (SAW) is a wave composed of a longitudinal wave and a transverse wave propagating on the surface of the elastic body.

  FIG. 1 shows a schematic configuration of a droplet detection apparatus 100 according to the present embodiment. As shown in the figure, the droplet detection apparatus 100 includes an acoustic wave device 1, a sine wave generator (AC signal generation circuit) 3, a pulse wave generator (pulse signal generation circuit) 5, and a signal amplifier (synthesis circuit) 7. , A bridge circuit 9, a signal waveform measuring device (detection circuit unit) 11, and a data processing unit (arithmetic circuit unit) 13. The sine wave generator 3, the pulse wave generator 5, and the signal amplifier 7 constitute a power supply circuit unit that supplies an electric signal to the acoustic wave device 1.

  First, the configuration of the acoustic wave device 1 will be described. FIG. 2 shows an example of the configuration of the acoustic wave device 1. 2A is a plan view of the acoustic wave device 1 as viewed from the surface side of the piezoelectric substrate, and FIG. 2B is a cross-sectional view taken along the line II-II of the acoustic wave device 1 of FIG. It is. The acoustic wave device 1 includes a piezoelectric substrate 101 formed in a rectangular flat plate shape, and an excitation electrode 102 for exciting a surface acoustic wave on the piezoelectric substrate 101. Here, the surface side of the piezoelectric substrate indicates the propagation surface side on which the surface acoustic wave propagates.

The piezoelectric substrate 101 is made of a crystal that generates a surface acoustic wave by a piezoelectric effect, such as lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), crystal, langasite, and the like. The piezoelectric substrate 101 is a substrate that generates elastic waves including longitudinal waves, such as piezoelectric ceramics such as PZT, or a piezoelectric thin film made of zinc oxide (ZnO), aluminum nitride (AlN), etc., from glass, silicon, or the like. It may be one that is entirely or partially laminated on the surface of the substrate. The piezoelectric substrate 101 may be a polymer substrate that generates a piezoelectric effect. The piezoelectric effect is a phenomenon in which, when a force or an electric field is applied to a crystal such as quartz, a voltage or a distortion corresponding to the force or electric field is generated. In this embodiment, an electric field is applied to the piezoelectric substrate 101. This refers to a phenomenon in which electrostriction occurs according to the electric field.

  The excitation electrode 102 is a pair of electrode members provided at one end (left end in FIG. 2A) on the surface of the piezoelectric substrate 101. The excitation electrode 102 is an electrode for exciting a surface acoustic wave on the piezoelectric substrate 101, and is constituted by two interdigital transducers (IDT) 102a and 102b. Specifically, the two interdigital electrodes 102a and 102b each extend in parallel to each other in a direction perpendicular to the base portion extending in a direction perpendicular to one end portion of the piezoelectric substrate 101 and in a direction orthogonal to the base portion. It has a plurality of electrode fingers, and the two interdigital electrodes 102a and 102b are arranged in a state of entering between the electrode fingers. The excitation electrode 102 is made of a single metal such as Al, Au, Cu, Cr, Ti, or Pt, or an alloy thereof, and is formed on the surface of the piezoelectric substrate 101 by photolithography, sputtering, or the like. The excitation electrode 102 having such a configuration causes the droplet Dp on the surface of the piezoelectric substrate 101 to be directed from one end portion on the excitation electrode 102 side to the other end portion on the surface of the piezoelectric substrate 101 by applying an alternating electric signal. That is, it can be conveyed along the direction orthogonal to the electrode fingers of the two interdigital electrodes 102a and 102b.

  Returning to FIG. 1, details of the configuration of each part of the droplet detection apparatus 100 will be described.

  The sine wave generator 3 is a power supply circuit that generates a sine wave AC electric signal having a predetermined high frequency (for example, 50 MHz, 100 MHz, etc.), and the pulse wave generator 5 is a predetermined low frequency ( For example, the power supply circuit generates a rectangular electric signal (pulse signal) having a predetermined duty ratio (for example, 50%) at a frequency of several Hz such as 1 Hz. That is, the pulse wave generator 5 repeatedly generates a pulse signal having a preset time width (for example, a time width of 0.5 sec when the duty ratio is 50% at a frequency of 1 Hz) at a specified frequency. The signal amplifier 7 has two inputs connected to the sine wave generator 3 and the pulse wave generator 5, respectively, and the AC electric signal output from the sine wave generator 3 is the pulse signal output from the pulse wave generator 5. Are combined with each other to generate a composite signal, and the composite signal is amplified and output. The power supply circuit unit configured by the sine wave generator 3, the pulse wave generator 5, and the signal amplifier 7 continuously outputs a sine wave AC electric signal with a predetermined time width corresponding to the time width of the pulse signal. And applied to the excitation electrode 102 of the acoustic wave device 1 via the bridge circuit 9. And this power supply circuit part repeats application of an alternating current electric signal intermittently with a specified frequency.

  The bridge circuit 9 is a three-terminal directional coupling bridge circuit, the first terminal is connected to the output of the signal amplifier 7, and the second terminal is connected to one terminal of the excitation electrode 102 of the acoustic wave device 1. The third terminal is connected to the input of the signal waveform measuring instrument 11. The other terminal of the excitation electrode 102 of the acoustic wave device 1 is grounded. The bridge circuit 9 applies the combined signal output from the signal amplifier 7 to the excitation electrode 102 via the first terminal and the second terminal, while the voltage change generated in the excitation electrode 102 is used as an electrical signal. The signal is output to the signal waveform measuring instrument 11 via the second terminal and the third terminal.

  The signal waveform measuring instrument 11 is a measuring instrument that measures a time change of the voltage generated in the excitation electrode 102 and outputs data indicating the time change. For example, an oscilloscope is used as such a signal waveform measuring instrument 11. This signal waveform measuring instrument 11 changes the voltage of the excitation electrode 102 over time according to the AC electrical signal applied to the excitation electrode 102 and the reflection signal caused by the reflected wave in the droplet Dp on the piezoelectric substrate 101 corresponding thereto. Measure. The signal waveform measuring instrument 11 can acquire the time variation data of the measured voltage as a time series data series and output the data series.

  The data processing unit 13 is a data processing unit that processes a data series indicating a temporal change in voltage output from the signal waveform measuring instrument 11. Such a data processing unit 13 physically includes an arithmetic processing circuit such as a CPU and a data storage device such as a RAM and a ROM, and detects the position of the droplet Dp on the piezoelectric substrate 101 of the acoustic wave device 1. It is a data processing device. The data processing unit 13 may be realized by a general-purpose computer terminal or may be realized by a dedicated CPU board on which a microcontroller unit (MPU) or the like is mounted. Details of the function of the data processing unit 13 will be described later.

In FIG. 3, an example of the time change of the voltage measured by the signal waveform measuring instrument 11 is shown. FIG. 3A is a graph showing a change with time of the voltage measured before placing the droplet Dp on the piezoelectric substrate 101 of the acoustic wave device 1, and FIG. 6 is a graph showing a change with time of a voltage measured after placing a droplet Dp on a piezoelectric substrate 101. In these graphs, time is plotted on the horizontal axis, and voltage amplitude is plotted on the vertical axis. As shown in FIG. 3A, before the droplet Dp is placed on the piezoelectric substrate 101, the voltage change measured by the signal waveform measuring instrument 11 is applied to the excitation electrode 102 by the power supply circuit unit. only the waveform WF ₁ alternating electric signal will appear in correspondence with the application timing of the AC electric signal. On the other hand, as shown in FIG. 3B, when the droplet Dp is arranged at a position facing the excitation electrode 102 on the piezoelectric substrate 101, the time of the voltage measured by the signal waveform measuring instrument 11 is measured. In the change, in addition to the waveform WF ₁ of the AC electrical signal, a waveform WF _{2 of the} reflected signal caused by the surface acoustic wave droplet Dp generated by the AC electrical signal appears. And start time ST ₁ which begins to occur in the waveform WF ₁ of the alternating electric signal, the time difference ΔT between the start time ST ₂ which begins to occur in the waveform WF ₂ of the reflected signal, the excitation electrodes of the liquid drop Dp in the piezoelectric substrate 101 on 102 The data processing unit 13 uses this fact to calculate the position of the droplet Dp on the piezoelectric substrate 101 based on the time difference ΔT.

  Specifically, in the calculation of the position of the droplet by the data processing unit 13, a model diagram as shown in FIGS. 4 and 5 is assumed. FIG. 4 is a model diagram of the acoustic wave device 1 viewed from a direction perpendicular to the transport direction of the droplet Dp and parallel to the piezoelectric substrate 101, and FIG. 5 is an enlarged view of the portion of the droplet Dp in the model diagram of FIG. FIG. Here, it is assumed that the center of the droplet Dp is arranged on the center line of the excitation electrode 102. In this model, the width in the transport direction of the droplet Dp of the electrode finger of one interdigital electrode 102a of the excitation electrode 102 is i, the front end of the interdigital electrode 102a in the transport direction, and the front end of the droplet Dp on the interdigital electrode 102a side. Is assumed to be l, the shape of the droplet Dp disposed on the piezoelectric substrate 101 is hemispherical, and the diameter thereof is assumed to be d.

  In such a model, when an AC electrical signal is applied to the excitation electrode 102, a surface acoustic wave is generated that propagates on the piezoelectric substrate 101 from the tip of the interdigital electrode 102a of the excitation electrode 102 in the transport direction. When the surface acoustic wave reaches the droplet Dp when the droplet Dp is present in the propagation direction of the surface acoustic wave, the surface acoustic wave is gradually attenuated while emitting a longitudinal wave into the droplet Dp. When the power of the surface acoustic wave is large and its duration is also long, the droplet Dp is transported on the piezoelectric substrate 101 in the transport direction by the radiation pressure generated in the droplet Dp by the longitudinal wave. . On the other hand, the longitudinal wave radiated into the droplet Dp generates a reflected wave RW that circulates within the droplet Dp.

In the calculation model applied to the data processing unit 13, the propagation path of the reflected wave RW is assumed to be the path shown in FIG. That is, the propagation path of the reflected wave RW is assumed to be a path including _two paths RT ₁ and RT ₂ in a cross section along the propagation direction X of the surface acoustic wave through the center of the droplet Dp assumed to be hemispherical. Route RT ₁ is assumed boundary line of the opposite surface of the interface between the liquid drop Dp and the piezoelectric substrate 101 in the cross section, the route RT ₂ is on the interface between the liquid drop Dp and the piezoelectric substrate 101 in the cross-section It is assumed to be a boundary line. In such a model, the length r of the route RT ₁ can be calculated as r = (1/2) πd, and the length of the route RT ₂ is equal to d.

Under the assumption of such a calculation model, the data processing unit 13 uses the arithmetic expression in which the propagation path of the reflected wave is set as described above, so that the liquid processing unit 13 can calculate the liquid based on the time difference ΔT between the AC electrical signal and the reflected signal. The position of the drop Dp is calculated. Specifically, the data processing unit 13 first processes the data series of the time change of the voltage output from the signal waveform measuring instrument 11, so that the start time of the waveform WF ₁ of the AC electrical signal appearing in the time change is obtained. The start time of the reflected signal waveform WF ₂ is specified. Further, the data processing unit 13 calculates a time difference ΔT from the two specified start times. At this time, the data processing unit 13 can also calculate the average value of the time difference repeatedly calculated as the time difference ΔT by applying the combined signal in which the AC electric signal and the pulse signal are superimposed on the excitation electrode 102. Further, the data processing unit 13 determines the calculated time difference ΔT, the width i of the excitation electrode 102, the distance l between the excitation electrode 102 and the droplet Dp, the diameter d of the droplet Dp, and the propagation of the surface acoustic wave on the piezoelectric substrate 101. Formula (1) showing the relationship between the velocity V _SAW and the propagation velocity V ₁ of the longitudinal wave in the droplet Dp;


To calculate the distance l based on the time difference ΔT.

The numerical values i and d in the arithmetic expression (1) are set in advance in the data processing unit 13 corresponding to the configuration of the acoustic wave device 1 and the amount of the droplet Dp to be used. Similarly, the propagation velocity V _SAW is previously set in the data processing unit 13 in accordance with the material constituting the piezoelectric substrate 101, the condition of the applied composite signal, the type of gas on the piezoelectric substrate 101, and the like. Is set. The propagation velocity V _l is set in advance in the data processing unit 13 in accordance with the characteristics of the material of the droplet Dp to be used, the conditions of the applied composite signal, and the like.

  Then, the data processing unit 13 calculates and outputs the position of the droplet Dp on the piezoelectric substrate 101 by converting the calculated distance l under a predetermined condition. For example, the distance l may be converted into a distance of a predetermined scale with a predetermined position of the piezoelectric substrate 101 as a reference, or coordinate values converted into a predetermined coordinate system may be calculated. The output of the position of the droplet Dp may be output to an output device such as a display provided directly in the data processing unit 13, or output to the outside via a data recording medium such as a communication network or a memory. Also good.

Note that the data processing unit 13 can also calculate the amount of the droplet Dp based on the time difference ΔT between the AC electrical signal and the reflected signal by using the arithmetic expression (1). That is, when the position of the droplet Dp is clear and the amount thereof is unknown, the numerical values i, l, V _SAW , V _l are set in the data processing unit 13 in advance. Then, the data processing unit 13 calculates the diameter d of the droplet Dp by solving the arithmetic expression (1) based on the time difference ΔT calculated with the application of the composite signal. Further, the data processing unit 13 calculates and outputs a value representing the amount of the droplet Dp based on the diameter d.

Similarly, the data processing unit 13 can also calculate the characteristics of the droplet Dp based on the time difference ΔT between the AC electrical signal and the reflected signal by using the arithmetic expression (1). That is, when the position and amount of the droplet Dp are clear and the material is unknown, the numerical values i, l, d, and V _SAW are set in the data processing unit 13 in advance. Then, the data processing unit 13 calculates the propagation velocity V ₁ in the droplet Dp by solving the arithmetic expression (1) based on the time difference ΔT calculated with application of the composite signal. Furthermore, the data processing unit 13 calculates and outputs a value representing a characteristic of the material of the liquid drop Dp based on the propagation velocity V _l. The characteristics of the droplet Dp calculated at this time include density, density, specific gravity and the like.

  Next, the procedure of a droplet detection method using the droplet detection apparatus 100 of this embodiment will be described. First, when the processing of the droplet detection apparatus 100 is activated, a combined signal generated by the power supply circuit unit is applied to the excitation electrode 102 of the acoustic wave device 1. Next, the time variation of the voltage at the excitation electrode 102 is measured by the signal waveform measuring instrument 11, and the reflected signal included in the time variation is detected. Thereafter, the data processing unit 13 processes the data series output from the signal waveform measuring instrument 11 to detect the time difference ΔT between the AC electrical signal and the reflected signal that appear in the time change of the voltage of the excitation electrode 102. . Further, the position of the droplet Dp is calculated and output by the data processing unit 13 by using the arithmetic expression (1) in which the propagation path of the reflected signal is set by the calculation model based on the detected time difference ΔT.

  According to the droplet detection device 100 and the droplet detection method using the droplet detection device described above, an AC electric signal having a predetermined frequency is applied to the excitation electrode 102 on the piezoelectric substrate 101 at a set time width. The reflected signal of the AC electrical signal is measured, and the time difference ΔT between the measured reflected signal and the AC electrical signal is detected, and the surface of the droplet Dp opposite to the piezoelectric substrate 101 and the droplet Dp on the piezoelectric substrate 101 side are detected. The position of the droplet is calculated from the time difference ΔT by using the arithmetic expression (1) in which the path for circulating the droplet Dp through the interface is set as the propagation path of the reflected signal. Thus, since the position of the droplet Dp is detected from the measurement result of the reflection signal using the excitation electrode 102 for transporting the droplet, the configuration of the apparatus can be simplified. In addition, the accuracy of the detection result of the droplet position is improved by calculating the position using the arithmetic expression (1) in which the propagation path of the reflection signal is set to the path for circulating the droplet Dp. As a result, accurate droplet position measurement can be realized without complicating the configuration.

Here, the result of confirming the accuracy of the arithmetic expression (1) in the calculation model used in the present embodiment is shown. FIG. 6 shows a graph comparing the relationship between the volume of the droplet Dp calculated by the calculation formula (1) and the time difference ΔT with the actual measurement result. Here, assuming that water is used as the material of the droplet Dp, the numerical values i, l, V _SAW , V ₁ are assumed to be known values, and the time difference ΔT determined from the calculation formula (1) and the volume of the droplet Dp are Shows the relationship. Moreover, the actual value measured by the signal waveform measuring instrument 11 using the water as the droplet Dp under the application condition of the same AC electric signal using the acoustic wave device 1 of the same condition is also shown. As shown in this result, it can be understood that the relationship obtained from the calculation formula (1) is in good agreement with the actual measurement value, and it can be understood that the position accuracy of the droplet Dp obtained using this calculation formula (1) is high. .

  Similarly, FIG. 7 shows a graph comparing the relationship between the volume of the droplet Dp calculated by the arithmetic expression (1) and the time difference ΔT with the actual measurement result. The difference from FIG. 6 is that 25% by weight of glycerol was used as a droplet. FIG. 8 shows a graph comparing the relationship between the volume of the droplet Dp calculated by the arithmetic expression (1) and the time difference ΔT with the actual measurement result. The difference from FIG. 6 is that 50% by weight of glycerol was used as a droplet. From these results, it can be seen that even when the material of the droplet Dp is changed, the relationship obtained from the calculation formula (1) agrees well with the actual measurement value, and the position of the droplet Dp calculated using this calculation formula (1). It can be understood that the accuracy of is high.

  In the present embodiment, the power supply circuit unit includes the sine wave generator 3, the pulse wave generator 5, and the signal amplifier 7. With such a configuration, an AC electrical signal can be repeatedly generated in a set time width, and the measurement of the droplet position can be repeatedly executed. Further, position measurement can be performed based on the average value of the time difference ΔT, and the measurement accuracy is improved.

In the present embodiment, the amount of the droplet Dp can be calculated from the time difference ΔT by using the arithmetic expression (1), and the propagation velocity V ₁ of the longitudinal wave in the droplet Dp is calculated from the time difference ΔT. and it can also calculate the characteristics of the droplets on the basis of the propagation velocity V _1. Thus, even when the amount of the droplet Dp or the characteristics of the droplet Dp is unknown, they can be obtained using the acoustic wave device 1.

  The present invention is not limited to the embodiment described above.

  In the above embodiment, the pulse wave generator 5 may be configured to be able to variably set the duty ratio of the pulse signal. According to such a configuration, the time width of the ON period of the pulse signal can be made variable. In this case, the time width of the surface acoustic wave to be generated can be adjusted. As a result, the transport of the droplet Dp and the measurement of the droplet position can be switched and executed. Specifically, when it is desired to transport the droplet Dp, the duty ratio can be increased to increase the duration of the surface acoustic wave, and when the position of the droplet Dp is to be detected, the duty ratio can be decreased to generate an AC electrical signal. Therefore, it is possible to increase the accuracy of measurement by preventing the reflection signal from being buried.

  Moreover, in said embodiment, you may use the thing provided with two or more excitation electrodes as the elastic wave device 1. FIG. 9 is a side view of the acoustic wave device 1A according to the modification of the present invention as viewed from a direction perpendicular to the transport direction of the droplet Dp and parallel to the piezoelectric substrate 101, and FIG. 10 is an acoustic wave device 1A of FIG. It is a figure which shows schematic structure of 100 A of droplet detection apparatuses containing these.

  The acoustic wave device 1A shown in FIG. 9 has an excitation having the same configuration as that of the excitation electrode 102 at the end opposite to the excitation electrode 102 on the piezoelectric substrate 101 in addition to the excitation electrode 102 formed of a pair of interdigital electrodes. An electrode 102A is provided. The excitation electrode 102 </ b> A is configured to have a shape symmetrical to the excitation electrode 102 with respect to the center line of the piezoelectric substrate 101. That is, the width of the interdigital electrode constituting the excitation electrode 102 </ b> A along the conveying direction of the electrode fingers is set to the same value i as that of the excitation electrode 102. 10 includes a sine wave generator 3, a pulse wave generator 5, a signal amplifier 7, and a bridge circuit 9 as a configuration for applying an AC voltage signal to the excitation electrode 102A. A sine wave generator 3A, a pulse wave generator 5A, a signal amplifier 7A, and a bridge circuit 9A having the same configuration are added. The signal waveform measuring instrument 11A measures the time change of the voltage at the excitation electrode 102 via the bridge circuit 9, and measures the time change of the voltage at the excitation electrode 102A via the bridge circuit 9A. A data series indicating the time change of the voltage in each of 102A is simultaneously output to the data processing unit 13A.

The data processing unit 13A of the droplet detection apparatus 100A calculates the time differences ΔT ₁ and ΔT ₂ between the AC electrical signal and the reflected signal with reference to the data series corresponding to the two excitation electrodes 102 and 102A. The data processing unit 13A can simultaneously calculate and output the position and amount of the droplet Dp based on these time differences ΔT ₁ and ΔT ₂ . Specifically, in the calculation model used at this time, the width of the excitation electrodes 102 and 102A along the transport direction is i, the distance between the tip of the excitation electrode 102 and the tip of the droplet Dp is l1, and the tip of the excitation electrode 102A and the liquid Assume that the distance from the tip of the droplet Dp is l2, the diameter of the droplet Dp is d, the propagation velocity of the surface acoustic wave on the piezoelectric substrate 101 is V _SAW , and the propagation velocity of the longitudinal wave in the droplet Dp is V _l. To do. In this calculation model, the time difference ΔT ₁ is expressed by the following equation (2):


The time difference ΔT ₂ is expressed by the following equation (3):


Represented by

Using the calculation model as described above, the data processing unit 13A simultaneously calculates the position and amount of the droplet Dp based on the time differences ΔT ₁ and ΔT ₂ . That is, the data processing unit 13A is set from a known distance L between the tips of the two excitation electrodes 102 and 102A on the piezoelectric substrate 101 with reference to preset values i, V _{SAW and} V _1. The following arithmetic expression (4);
L = l1 + l2 + d (4)
Then, the diameter d of the droplet Dp and the distances l1 and l2 can be obtained by solving the arithmetic expressions (2) and (3). The amount and position of the droplet Dp can be calculated based on the diameter d and the distances l1 and l2. Further, the data processing unit 13A can simultaneously calculate the amount and characteristics of the droplet Dp when the position of the droplet Dp is known. If the amount of the droplet Dp is known, the data processing unit 13A can calculate the droplet Dp. The position and characteristics of Dp can be calculated simultaneously.

According to such a modification, it is possible to realize accurate droplet position and droplet amount measurement without complicating the configuration. In this modification, the number of power supply circuit portions corresponding to the number of excitation electrodes is provided, but AC power signals are time-divisionally applied to the excitation electrodes 102 and 102A using a switch or the like with one power supply circuit portion. You may make it apply. At this time, the detection of the time differences ΔT ₁ and ΔT ₂ may also be performed in time division in synchronization with switching of the AC electric signal in time division.

  FIG. 11 shows the configuration of an acoustic wave device 1B according to another modification of the present invention. In this modification, an acoustic wave device 1B is shown in which three excitation electrodes 102, 102B, and 102C are provided at one end on the piezoelectric substrate 101 of the acoustic wave device 1B. These excitation electrodes 102, 102B, and 102C are connected to independent power supply circuit units, respectively, so that the operation can be controlled independently. Further, on the piezoelectric substrate 101 in the acoustic wave device 1B, a hydrophilic guide 107 for transporting the droplets Dp1, Dp2, Dp3 in their transport direction from the respective sides of the excitation electrodes 102, 102B, 102C. Is provided. The guide 107 is configured to join at the central portion of the piezoelectric substrate 101 and further extend in a direction away from the excitation electrode 102. According to the elastic wave device 1B having such a configuration, the three droplets Dp1, Dp2, and Dp3 arranged on the guide 107 extending from the vicinity of the excitation electrodes 102, 102B, and 102C are guided by the operation control of the power supply circuit unit. 107, and these three droplets Dp1, Dp2, Dp3 can be made into one droplet Dp. In this case, the integrated droplets Dp are uniformly stirred and mixed by the longitudinal wave propagated to the piezoelectric substrate 101. Further, the integrated droplet Dp can be transported toward the other end on the piezoelectric substrate 101. Note that the guide 107 may be omitted, but in some cases, the transport of the droplet Dp is easier, and a guide groove formed in a concave shape in place of the hydrophilic guide 107 can be used as the guide 107.

  The position of the droplets Dp1, Dp2, Dp3, Dp can be detected by using the droplet detection device having the same configuration as that shown in FIG. 10 for the acoustic wave device 1B having such a configuration. However, in this case, one set of power supply circuit units is added to the configuration of FIG. That is, the position of the droplets Dp1, Dp2, Dp3 can be calculated and output by operating the signal waveform measuring instrument 11A and the data processing unit 13A at the timing before the droplets Dp1, Dp2, Dp3 merge. Alternatively, the position of the droplet Dp can be calculated and output by operating the signal waveform measuring instrument 11A and the data processing unit 13A at the timing after the droplets Dp1, Dp2, and Dp3 merge.

  12 shows the configuration of an elastic wave device 1C according to another modification of the present invention, and FIG. 12 (a) is a plan view of the elastic wave device 1C as viewed from the surface side of the piezoelectric substrate. (B) is sectional drawing which followed the XII-XII line | wire of the elastic wave device 1C of Fig.12 (a). As in such a modification, the transport path plate 104 may be disposed via the liquid phase W (for example, water) in the traveling direction of the surface acoustic wave excited by the excitation electrode 102 on the piezoelectric substrate 101. . The transport path plate 104 is a plate member that constitutes a surface on which the droplets Dp are transported, and is formed of a transparent glass material formed in a square plate shape. The transport path plate 104 is formed on the piezoelectric substrate 101 by the surface tension of the liquid phase W. It is fixed. With such a configuration, it is possible to improve the efficiency of the transporting operation of the transported object (droplet Dp) without the need to clean the piezoelectric substrate 101, and to handle a wide variety of transported objects (droplet Dp). Can do.

  Although the transport path plate 104 is made of a transparent glass material, the transport path plate 104 is not limited to this as long as it is a substance that can displace the droplets Dp by the radiation pressure caused by the surface acoustic wave generated in the piezoelectric substrate 101. For example, the conveyance path plate 104 may be made of an iron-based or non-ferrous material in addition to a glass-based material.

The liquid phase W is not limited to water as long as it is a liquid capable of propagating longitudinal waves radiated from surface acoustic waves. Specifically, it may be an incompressible fluid that is a liquid that hardly volatilizes. In this case, the incompressible fluid is a fluid having a compressibility of approximately 2 × 10 ⁻⁹ (1 / N / m ² ) or less in an atmosphere of 15 ° C.

DESCRIPTION OF SYMBOLS 1,1A, 1B ... Elastic wave device, 3, 3A ... Sine wave generator (AC signal generation circuit, power supply circuit part), 5,5A ... Pulse wave generator (pulse signal generation circuit, power supply circuit part), 7, 7A: Signal amplifier (synthetic circuit, power supply circuit unit), 9, 9A: Bridge circuit, 11, 11A ... Signal waveform measuring device, 13, 13A ... Data processing unit (arithmetic circuit unit) 100, 100A ... Droplet detection device, 101 ... piezoelectric substrate, 102, 102a, 102B, 102C ... excitation electrodes, 104 ... transport path plate, Dp, Dp1, Dp2, Dp3 ... droplets, _RT 1, RT 2 _... propagation path.

Claims (8)

An excitation electrode for exciting a surface acoustic wave on the piezoelectric substrate, and an acoustic wave device for transporting droplets on the piezoelectric substrate;
A power supply circuit section for applying an alternating current electric signal having a predetermined frequency to the excitation electrode with a set time width;
A detection circuit unit for measuring a reflected signal of the AC electrical signal at the excitation electrode;
An arithmetic circuit unit that detects a time difference between the reflected signal and the AC electric signal measured by the detection circuit unit, and calculates a position of a droplet on the piezoelectric substrate based on the time difference;
The arithmetic circuit unit circulates the droplet through a propagation path of the reflected signal via a surface opposite to the interface between the droplet and the piezoelectric substrate and the interface between the droplet and the piezoelectric substrate. The position is calculated from the time difference by using an arithmetic expression set for the route.
Droplet detection device. The power supply circuit unit includes: an AC signal generation circuit that generates the AC electrical signal; a pulse signal generation circuit that repeatedly generates the pulse signal having the time width; and a synthesis circuit that superimposes the AC electrical signal on the pulse signal. Have
The droplet detection device according to claim 1. The pulse signal generation circuit is configured to be able to variably set the time width of the pulse signal.
The droplet detection device according to claim 2. The arithmetic circuit unit includes a propagation velocity (V _SAW ) of the surface acoustic wave on the piezoelectric substrate, a width (i) of the excitation electrode in the droplet transport direction, a tip of the excitation electrode on the droplet side, The distance (l) from the tip of the droplet on the excitation electrode side, the diameter (d) of the droplet, the propagation speed (V _l ) of the longitudinal wave in the droplet, and the time difference (Δt) The following arithmetic expression (1) between:


The distance (l) is calculated using, and the position is calculated based on the distance (l).
The droplet detection apparatus of any one of Claims 1-3. The arithmetic circuit unit calculates the droplet amount from the time difference by using the arithmetic expression.
The droplet detection apparatus of any one of Claims 1-4. The arithmetic circuit unit calculates the propagation velocity of longitudinal waves in the droplet from the time difference by using the arithmetic expression, and calculates the characteristics of the droplet based on the propagation velocity.
The droplet detection device according to any one of claims 1 to 5. The acoustic wave device further includes a transport path plate disposed via a liquid phase on a propagation surface on which the surface acoustic wave generated on the surface of the piezoelectric substrate propagates.
The droplet detection device according to claim 1. A method of detecting a position of a droplet using an acoustic wave device provided with an excitation electrode for exciting a surface acoustic wave on a piezoelectric substrate and transporting the droplet on the piezoelectric substrate,
Applying an alternating electrical signal of a predetermined frequency to the excitation electrode with a set time width,
Measuring the reflected signal of the AC electrical signal at the excitation electrode;
A time difference between the measured reflected signal and the AC electric signal is detected, and the propagation path of the reflected signal is determined on the surface opposite to the interface between the droplet and the piezoelectric substrate, and the interface between the droplet and the piezoelectric substrate. The position of the droplet on the piezoelectric substrate is calculated from the time difference by using an arithmetic expression set in a path for circulating the droplet via
Droplet detection method.