JP5066442B2 - Piezoelectric sensor and sensing device - Google Patents

Description

  The present invention includes a piezoelectric vibrator configured such that an excitation electrode provided on one surface side of a piezoelectric piece contacts a measurement atmosphere and an excitation electrode provided on the other surface side faces an airtight space. The present invention relates to a piezoelectric sensor that senses an object to be measured by detecting the natural frequency of a child and a sensing device that uses this piezoelectric sensor.

  To detect the presence of trace substances in the sample liquid, for example, environmental pollutants such as dioxin, disease markers such as hepatitis C virus and C-reactive protein (CPR), and to measure these substances, crystal vibration A measurement method using a crystal sensor including a child and a measuring instrument that is electrically connected to the crystal sensor and includes an oscillation circuit for oscillating the crystal resonator is widely known (for example, a patent) Reference 1).

  Specifically, the measurement method includes, for example, a plate-shaped crystal piece and a pair of foil-like excitation electrodes (a pair of foil-like excitation electrodes provided so as to sandwich the crystal piece on one side and the other side of the crystal piece) A quartz sensor including a crystal resonator called a Langevin type with an excitation electrode) is configured so that the electrode on one side contacts the measurement atmosphere (sample solution) and the electrode on the other side faces the airtight space Then, an antibody that captures the antigen to be measured by an antigen-antibody reaction is formed as an adsorption layer on the surface of the electrode on one side, and the antigen is captured in this adsorption layer. This utilizes the property that the frequency fluctuates. Then, the difference between the natural frequency of the crystal unit before the measurement object is adsorbed on the adsorption layer and the natural frequency of the crystal unit after the measurement object is adsorbed on the adsorption layer, that is, the amount of change is obtained. The presence or concentration of the measurement object is detected according to the amount.

  As described above, only one side of the crystal unit is brought into contact with the measurement atmosphere and the other side faces the airtight space. It is because it is preferable to do. In the above measurement, an adsorption layer is provided on the surface of the excitation electrode, and the measurement object is chemically adsorbed on the adsorption layer. The measurement is performed directly on the surface of the electrode on the one side. In some cases, the measurement object is measured based on physical adsorption. Specifically, in the development stage of the quartz sensor, an antibody is physically adsorbed on the surface of the electrode itself to form an adsorption layer, and the adsorption amount of the antibody adhering to the surface of the electrode is obtained.

  FIG. 11 shows an example of the configuration around the crystal resonator provided in the crystal sensor. In FIG. 11, reference numeral 11 denotes a wiring board, and the crystal unit 1 is placed on the wiring board 11. In this crystal resonator 1, one excitation electrode 12 and the other excitation electrode 13 are respectively formed on one surface side and the other surface side of a plate-shaped crystal piece 10, and are connected to one excitation electrode 12 on one surface side. The crystal piece 10 is connected to one lead electrode 12a drawn from one surface side of the crystal piece 10 to the other surface side through the end of the crystal piece 10 and the other excitation electrode 13 on the other surface side. The other lead electrode 13a drawn to one surface side through the end of 10 is formed, and the lead electrodes 12a, 13a are provided on the wiring board 11 side through the conductive adhesive 14 Is electrically connected.

  Reference numeral 15 in FIG. 11 denotes a through hole formed in the wiring substrate 11 in the thickness direction, and reference numeral 15 a in FIG. 11 denotes a sealing member that closes the through hole 15 from the back side of the substrate 11. A region surrounded by the sealing member 15a, the through-hole 15 and the crystal resonator 1 constitutes an airtight space, and the excitation electrode 13 on the back side of the crystal resonator 1 faces the airtight space. Reference numeral 16 in FIG. 11 denotes a plate-like crystal pressing member made of, for example, rubber or the like, and presses the crystal resonator 1 against the substrate 11 to fix its position.

  Reference numeral 17 in FIG. 11 denotes an opening provided so as to penetrate the crystal pressing member 16 in the thickness direction, and faces the excitation electrode 12 on the surface side of the crystal unit 1. Reference numeral 18 in FIG. 11 denotes an annular protrusion of the crystal pressing member 16. A predetermined amount of sample liquid is stored in a liquid storage space 19 surrounded by the opening 17 and the annular protrusion 18, and the excitation electrode 12 is in contact with the measurement atmosphere.

  However, the above-described quartz sensor has the following problems. Since the crystal sensor is mounted on the wiring board 11 via the conductive adhesive 14, it is difficult to make the height of the conductive adhesive 14 uniform between the crystal sensors. That is, in the above-described quartz sensor, it is difficult to avoid variations in the height of the conductive adhesive 14. If there is variation in the height of the conductive adhesive 14 applied to the part where the extraction electrodes 12a, 13a and the electrode 11a face each other between the quartz sensors, the distance from the quartz pressing member 16 to the substrate 11 is constant. The stress due to the restoring force of the crystal pressing member 16 varies. For this reason, the frequency change amount (Δf), which is the difference between the natural frequency f of the crystal unit before the antigen is adsorbed on the adsorption layer and the natural frequency f of the crystal unit after the antigen is adsorbed on the adsorption layer, is obtained. In determining, the amount of change of f with respect to the amount of adsorption changes according to the stress applied to the crystal piece 10, and the amount of antigen cannot be detected with high accuracy.

  Even when the amount of antibody adsorption is determined by attaching an antibody to the surface of one excitation electrode 12 itself in the development stage of the quartz sensor, the amount of antibody cannot be detected with high accuracy for the same reason as described above.

  On the other hand, in Patent Document 2, there is a gap between a piezoelectric plate mounted in a container and having excitation electrodes on both sides, and the piezoelectric plate fixed with a conductive adhesive between the bottom plate in the container. In the piezoelectric vibrator having a support base that holds and supports the piezoelectric vibrator, a groove having a coating width for the conductive adhesive is provided on the upper surface of the support base fixed with the conductive adhesive, and the piezoelectric plate and the support base are Although it is described that the conductive adhesive is prevented from expanding when it is stuck and fixed, the piezoelectric sensor configured to press the piezoelectric vibrator against the substrate with the pressing member has the above-described problems. There is no suggestion or description about.

JP 2006-194866 A JP-A-5-283967 (paragraphs 0009 and 0012 and FIG. 1)

  The present invention has been made in view of such circumstances, and an object of the present invention is to include a Langevin type piezoelectric vibrator, and a measurement object comes into contact with an excitation electrode on one side of the piezoelectric vibrator, thereby the piezoelectric vibrator. A piezoelectric sensor that detects a measurement object in a sample liquid based on a change in the natural frequency of the piezoelectric vibrator, and the amount of change in the oscillation frequency of the piezoelectric vibrator caused by adsorption of the measurement object between the piezoelectric sensors An object of the present invention is to provide a technique capable of suppressing the variation and detecting the amount of the measurement object with high accuracy.

The present invention relates to a piezoelectric sensor that is electrically connected to a measuring instrument body in order to detect an object to be measured in a sample liquid.
A wiring board provided with a connection terminal portion connected to the measuring instrument main body, and on one surface side thereof, an electrode electrically connected to the connection terminal portion and a recess for configuring an airtight space;
One excitation electrode and the other excitation electrode are formed on one surface side and the other surface side of the plate-shaped piezoelectric piece, respectively, and are connected to one excitation electrode on the one surface side, and from one surface side of the piezoelectric piece, the piezoelectric piece One extraction electrode drawn to the other side through the end, and the other extraction electrode connected to the other excitation electrode on the other side and drawn to the end of the piezoelectric piece are formed, A piezoelectric vibrator provided on the wiring substrate in a state in which the other excitation electrode on the other surface side faces the concave portion and a liquid storage space having a bottom surface on one surface side of the piezoelectric vibrator is formed. A pressing member made of an elastic material provided so as to surround the liquid storage space and provided with an annular protrusion for attaching the outer portion of the concave portion on one surface side of the crystal resonator to the wiring board side ;
A cover for covering the pressing member facing the wiring board, communicating with the liquid storage space on the surface thereof, and a liquid injection cover provided with an injection port for injecting a sample liquid into the liquid storage space;
The annular protrusion is configured such that the diameter decreases as the inner peripheral surface surrounding the liquid storage space faces downward ,
The wiring board includes a recess for accommodating a conductive adhesive at a portion where the one extraction electrode and the other extraction electrode and the electrode face each other,
The conductive adhesive in the recess and the extraction electrode are bonded in a state where the peripheral edge of the piezoelectric piece is in close contact with the wiring substrate, and the extraction electrode and the electrode are electrically connected. To do.

  Further, the sensing device of the present invention includes the above-described piezoelectric sensor, and a measuring instrument main body that detects the natural frequency of the piezoelectric vibrator and detects a measurement object in the sample liquid based on the detection result. It is characterized by.

  The piezoelectric sensor of the present invention includes a recess for accommodating a conductive adhesive at a portion of the wiring board where the lead-out electrode on the back side of the piezoelectric vibrator and the electrode on the wiring board face each other, and the periphery of the piezoelectric piece The conductive adhesive in the recess and the extraction electrode are bonded together in a state in which the portion is in close contact with the wiring substrate, and the extraction electrode and the electrode are electrically connected. In this way, the stress applied to the piezoelectric piece by the crystal pressing member is uniformly applied within the surface of the piezoelectric piece, and there is no possibility that the stress applied to the piezoelectric piece by the crystal pressing member varies between the piezoelectric sensors. . As a result, variation in the change in the oscillation frequency of the piezoelectric vibrator due to adsorption of the measurement object between the piezoelectric sensors can be suppressed, and the amount of the measurement object can be detected with high accuracy.

  An embodiment of a crystal sensor which is an example of a piezoelectric sensor according to the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing a quartz sensor 20 which is an example of a piezoelectric sensor according to the present invention. FIG. 2 is an exploded perspective view showing the upper surface side of each component of the crystal sensor 20. As shown in FIG. 2, the crystal sensor 20 includes a sealing member 3A, a wiring board 3, and a crystal resonator 2 that is a piezoelectric resonator. Each component of the crystal pressing member 4 and the liquid injection cover 5 is configured by overlapping from the bottom in this order.

  The crystal resonator 2 includes a crystal piece 21 that is a piezoelectric piece, excitation electrodes 22 and 23, and extraction electrodes 24 and 25. As shown in FIGS. 2 and 3, the crystal piece 21 has, for example, an equivalent thickness of 1 μm to 300 μm, preferably 185 μm, and is formed in a circular shape. One excitation electrode 22 and the other excitation electrode 23 in the form of a foil are attached to the one surface side and the other surface side of the crystal piece 21, respectively, and are formed in a circular shape having a smaller diameter than the crystal piece 21. In addition, one end side of one foil-shaped extraction electrode 24 is formed on one surface side of the crystal piece 21 and connected to the one excitation electrode 22, and the extraction electrode 24 is bent along the end surface of the crystal piece 21. The crystal piece 21 is turned to the other surface side (back surface side).

Further, on the other surface side of the crystal piece 21, one end side of the other foil-like extraction electrode 25 is formed by being connected to the other excitation electrode 23 in the same layout as the previous extraction electrode 24. On both sides, the layout of the excitation electrode 22 (23) and the extraction electrode 24 (25) is the same.
The equivalent thicknesses of the excitation electrodes 22 and 23 and the extraction electrodes 24 and 25 are 0.2 μm, for example, and gold (Au) is used as an electrode material, for example.

  As will be described later, since the excitation electrode 22 is provided so as to face the liquid storage space 45 to which the sample liquid is supplied, an antibody that captures an antigen by an antigen-antibody reaction is used as an adsorption layer on the excitation electrode 22. In addition, blocking substances (block bodies) are adsorbed in the gaps between the antibodies. When the measurement object is adsorbed on the adsorption layer, the frequency of the crystal unit 2 changes according to the adsorption amount of the measurement object.

  Next, the wiring board 3 will be described. The wiring board 3 is composed of, for example, a printed circuit board, and electrodes 31 and 32 are provided at an interval from the front end side to the rear end side of the surface. Further, for example, a rectangular groove 7 which is a recess for accommodating the conductive adhesive 8 is formed at a portion where the electrodes 31 and 32 of the wiring board 3 are provided, as shown in FIG. The electrodes 31 and 32 are integrally formed on the bottom and side surfaces of the groove portion 7. Between the electrodes 31 and 32 of the wiring board 3, a through hole 33 is formed which is perforated in the thickness direction of the wiring board 3 at a distance from the electrodes 31 and 32. As will be described later, the through-hole 33 constitutes a recess that forms an airtight space where the excitation electrode 23 on the back surface side of the crystal resonator 2 faces, and the diameter of the through-hole 33 is formed so as to accommodate the excitation electrode 23. Yes.

  Further, two parallel line-shaped conductive path patterns are formed as connection terminal portions 34 and 35, respectively, closer to the rear end side than the portion where the electrode 32 is formed. One connection terminal portion 34 is electrically connected to the electrode 31 via the pattern 34a, and the other connection terminal portion 35 is electrically connected to the electrode 32 via the pattern 35a.

  Reference numeral 36 in FIG. 2 denotes a weir formed by photolithography using a resist, for example, and is formed along the outer shape of the crystal unit 2. The weir 36 serves to align the crystal resonator 2, and the crystal resonator 2 is placed in a region surrounded by the weir 36. In FIG. 2, 37 a, 37 b, and 37 c are engagement holes, which are drilled in the thickness direction of the wiring board 3. These engagement holes 37a, 37b, and 37c are engaged with engagement protrusions 51a, 51b, and 51c provided on the lower surface of the cover 5, respectively. Further, reference numerals 38 a, 38 b, and 38 c in FIG. 2 are notches formed on the periphery of the wiring board 3. Further, claw portions 52a, 52b, and 52c bent inward are provided on the peripheral edge portion of the lower surface of the cover 5, and the notches 38a, 38b, and 38c are engaged with the claw portions 52a, 52b, and 52c, respectively. .

  The sealing member 3 </ b> A is a film-like member and constitutes a concave portion that forms an airtight space together with the through-hole 33.

  Next, the crystal pressing member 4 will be described. The crystal pressing member 4 is made of, for example, silicon rubber, and has a shape corresponding to the wiring board 3. More specifically, the crystal pressing member 4 is formed in a plate shape provided with rectangular cutout portions 41a, 41b, and 41c respectively corresponding to the cutout portions 38a, 38b, and 38c. Further, when the side where the notches 41 b and 41 c are formed is the rear side, the notch 41 a is formed at the center of one edge on the front side of the crystal pressing member 4.

  FIG. 4 is a perspective view showing the lower surface side of the crystal pressing member 4, and the configuration of the pressing member 4 will be described with reference to this drawing. As shown in FIGS. 3 and 4, a concave portion 42 for accommodating the crystal resonator 2 is formed on the lower surface of the crystal pressing member 4. An annular protrusion 43 that is slightly larger than the through hole 33 on the upper surface of the wiring board 3 is provided at the center of the ceiling surface portion (bottom surface portion in the case of description in FIG. 4) of the recess 42. The annular protrusion 43 has a role of pressing the crystal unit 2 against a region surrounding the through hole 33 of the wiring substrate 3 to fix the position of the crystal unit 2.

As shown in FIGS. 2, 3, and 4, an opening 44 is formed on the surface side of the crystal pressing member 4, and the opening 44 communicates with a space surrounded by the annular protrusion 43. .
The peripheral surface 44a of the opening 44 and the inner peripheral surface 43a of the annular protrusion 43 are inclined inward and downward. That is, the diameters of the opening 44 and the annular protrusion 43 become smaller as it goes downward. The tip 47 of the annular protrusion 43 presses the peripheral edge of the crystal piece 20. The area surrounded by the peripheral surfaces 43a and 44a and the crystal resonator 2 constitutes a liquid storage space 45 for storing the sample liquid.

  Further, 46a and 46b in FIG. 2 are engagement holes which are perforated so as to penetrate the pressing member 4 in the thickness direction, and the engagement holes 37a and 37b of the wiring board 3 and the liquid injection cover 5 are engaged. It is formed so as to correspond to the protrusions 51a and 51b. In FIG. 2, 46 c is an arc-shaped cutout formed at the center of the rear edge, and corresponds to the engagement hole 37 c of the wiring board 3 and the engagement protrusion 51 c of the liquid injection cover 5.

  Next, the configuration of the liquid injection cover 5 will be described. The cover 5 is made of, for example, polycarbonate, and a sample solution inlet 53 and a check port 54 are formed on the front side and the back side of the upper surface, respectively. As shown in FIG. 3, an injection path 55 that is a groove is formed in the lower surface of the cover 5 along the length direction of the cover 5, and one end and the other end of the injection path 55 are an injection port 53 and a confirmation port. 54, respectively. The injection path 55 is provided so as to face the opening 44, and the sample liquid injected into the injection port 53 is supplied to the liquid storage space 45 through the injection path 55. When a predetermined amount of sample liquid is supplied to the crystal sensor 20, the liquid level of the sample liquid appears at the confirmation port 54, and it is possible to check whether or not the liquid is supplied to the sensor 20.

  An annular weir 56 surrounding the injection path 55 is provided on the lower surface of the cover 5, and the weir 56 is recessed into the crystal pressing member 4 so that the sample liquid injected into the injection port 51 is pressed against the liquid injection cover 5. It has a role of preventing leakage from between the members 4.

  The crystal sensor 20 is assembled as follows. First, the through hole 33 of the wiring board 3 is closed by the sealing member 3 </ b> A, and a recess is formed in the board 3. Subsequently, a predetermined amount of conductive adhesive 8 is applied in the groove portion 7 of the wiring board 3. Thereafter, the crystal resonator 2 is formed so that the extraction electrodes 24 and 25 on the crystal resonator 2 side overlap with the electrodes 31 and 32 on the wiring substrate 3 side and the excitation electrode 23 on the back surface side of the crystal resonator 2 overlaps the concave portion. Is placed on the wiring board 3.

  Next, the engagement protrusions 51a to 51c of the liquid injection cover 5 are engaged with the engagement holes 46a and 46b and the notch 46c of the crystal pressing member 4, and the liquid injection cover 5 and the pressing member 4 are overlapped. Thereafter, the claw portions 52 a, 52 b, 52 c of the liquid injection cover 5 and the notches 38 a, 38 b, 38 c of the wiring substrate 3 are put on each other and pressed toward the wiring substrate 3. Thereby, each claw part 52a-52c of the cover 5 for liquid injection is bent to the outer side of the wiring board 3, and further, each claw part 52a-52c is the lower surface of the peripheral part of the wiring board 3 via each notch part 38a-38c. At the same time, the claw portions 52a to 52c are restored to their original shapes by the inward restoring force, and the wiring board 3 is sandwiched between the claw portions 52a to 52c and locked together. The pressing member 4 sandwiched between the substrate 3 and the cover 5 is pressed against them.

  Due to the elasticity of the pressed pressing member 4, the annular protrusion 43 presses the outer portion of the recess on the surface of the crystal resonator 2 toward the wiring substrate 3, thereby fixing the position of the crystal resonator 2. The peripheral edge is in close contact with the wiring substrate 3, and the concave portion formed by the through-hole 33 and the sealing member 3 </ b> A becomes an airtight space, and the excitation electrode 23 on the back surface side of the crystal unit 2 faces the airtight space. The conductive adhesive 8 in the groove 7 and the extraction electrodes 24 and 25 on the back surface side of the crystal unit 2 are bonded, and the extraction electrodes 24 and 25 and the electrodes 31 and 32 on the wiring board 3 side are electrically connected. Is done.

  Before the measurement, in order to prevent impurities entering from the injection port 53 and the confirmation port 54 from adhering to the crystal unit 2, the injection port 53 and the confirmation port 54 are covered with a film-like protective sheet.

  When the crystal sensor 20 in the present embodiment is used, an operator injects the sample liquid into the injection port 53 of the liquid injection cover 5 by using, for example, an injector. The sample liquid injected into the inlet 53 is supplied to the liquid storage space 45 of the sample liquid constituted by the opening 44 and the annular protrusion 43, and the excitation electrode 22 on the surface side of the crystal unit 2 is in contact with the sample liquid. .

According to the above-described embodiment, the conductive adhesive 8 is accommodated in the portion of the wiring board 3 where the extraction electrodes 24 and 25 on the back surface side of the crystal unit 2 and the electrodes 31 and 32 on the wiring board 3 side face each other. The conductive adhesive 8 in the groove 7 and the extraction electrodes 24 and 25 are bonded in a state where the peripheral edge of the crystal piece 21 is in close contact with the wiring board 3, and the extraction electrode 24, 25 and the electrodes 31, 32 are electrically connected. In this way, the stress applied to the crystal piece 21 by the crystal pressing member 4 is uniformly applied within the plane of the crystal piece 21, and the stress applied to the crystal piece 21 by the crystal pressing member 4 varies between the crystal sensors 20. There is no risk of occurrence. As a result, as shown in an embodiment to be described later, variation in the frequency stability of the crystal unit 2 after the oscillation frequency of the crystal unit 2 has changed due to adsorption of the measurement object between the crystal sensors 20 is suppressed. .
In the crystal sensor 20, the crystal pressing member 4 may be formed of an elastic body other than rubber.

  The above-described quartz sensor 20 is used as a detection unit of the sensing device by being connected to the measuring device main body 6 having the configuration shown in FIG. 5 which is a block diagram, for example. 5, 62 is an oscillation circuit for oscillating the crystal piece 21 of the crystal sensor 20, 63 is a reference clock generator for generating a reference frequency signal, and 64 is a frequency difference detection means comprising a heterodyne detector, for example. Based on the frequency signal from 62 and the clock signal from the reference clock generator 63, a frequency signal corresponding to the frequency difference between the two is extracted. 65 is an amplifying unit, 66 is a counter that counts the frequency of an output signal from the amplifying unit 65, and 67 is a data processing unit.

  For example, 9 MHz is selected as the frequency of the quartz sensor 20, and 10 MHz is selected as the frequency of the reference clock generator 63, for example. When the object to be measured, for example, dioxin is not adsorbed to the above-described adsorption layer provided on the quartz crystal resonator 2 of the quartz sensor 20, the frequency difference detecting means 64 determines the difference between the frequency from the quartz sensor side and the frequency of the reference clock. 1 MHz frequency signal (frequency difference signal) is output, but when the measurement object contained in the sample solution is adsorbed to the adsorption layer of the crystal resonator 2, the natural frequency of the crystal resonator 2 changes, and this Therefore, since the frequency difference signal also changes, the count value in the counter 66 changes, and thus the concentration of the measurement object or the presence or absence of the substance can be detected.

  FIG. 6 is a view showing an example of the measuring instrument main body 6 described above. As shown in FIG. 6A, the measuring instrument main body 6 includes a main body portion 68 and an openable / closable lid portion 69 formed on the front surface of the main body portion 68. When the lid 69 is opened, the front surface of the main body 68 appears as shown in FIG. A plurality of insertion ports 60 of the crystal sensor are formed on the front surface of the main body 68, and the number of the insertion ports is, for example, eight, and is formed in a straight line with a constant interval.

  By inserting the rear end side of the wiring substrate 3 of each crystal sensor 20 horizontally to a certain depth into each insertion port 60 of the measuring device main body 6, the connection terminal portions 34 and 35 of the substrate 3 and the insertion ports are inserted. The electrodes formed inside 60 are electrically connected to each other, and at the same time, the inside of the insertion port 60 holds the wiring board 3 so that the crystal sensor 20 is fixed to the measuring device main body 6 while keeping the level. The

  By configuring the sensing device using the above-described crystal sensor 20 as described above, the quartz crystal after the oscillation frequency of the crystal sensor 20 is changed by the adsorption of the measurement object in the plurality of eight crystal sensors 20 in this example. Since there is almost no variation in the frequency stability of the sensor 20, when measuring eight measurement objects having different concentrations using the eight crystal sensors 20, the amount of change in frequency of the eight measurement objects is accurately measured. be able to.

An experiment conducted for confirming the effect of the present invention will be described.
A. Experiment 1
(Example)
Frequency measurement was performed using the quartz sensor 20 described above. In this frequency measurement, first, 0.12 m of a PBS solution of pH 6.7, which is a buffer solution, is injected into the injection port 53 of the crystal sensor 20. As a result, the environmental atmosphere of the crystal unit 2 changes from the gas phase to the liquid phase, and accordingly, the oscillation frequency of the crystal unit 2 decreases. Next, 0.6 ml of a sample solution containing 100 μg / ml of P protein as an antigen is injected into the injection port 53 of the crystal sensor 20. The P protein is captured by the adsorption layer on the surface of the crystal unit 2, and the oscillation frequency of the crystal unit 2 changes according to the amount of adsorption.

  FIG. 7 shows the result of the above-described frequency measurement performed on each of the three crystal sensors 20. The vertical axis in FIG. 7 is frequency (Hz), and the horizontal axis is time (seconds).

(Comparative example)
In the conventional quartz sensor shown in FIG. 11, that is, in the wiring board, a groove for accommodating the conductive adhesive is not formed in a portion where the extraction electrode on the back surface side of the crystal resonator and the electrode on the wiring board side face each other. First, frequency measurement was performed in the same manner as in the example using a crystal sensor having a structure in which a crystal resonator was mounted on a wiring board via a conductive adhesive. This frequency measurement was performed for each of three conventional quartz sensors. The result is shown in FIG. The vertical axis in FIG. 8 is frequency (Hz), and the horizontal axis is time (seconds).
(Results and discussion)
As shown in FIG. 8, in the comparative example, in the three conventional quartz sensors, when the oscillation frequency of the crystal resonator after the P protein is adsorbed on the adsorption layer and the oscillation frequency of the crystal resonator is changed, the P protein is observed. It can be seen that the three quartz sensors are stable at different frequencies, even though their concentrations are the same. That is, it can be seen that the frequency stability of the crystal resonator after the oscillation frequency of the crystal resonator changes due to the adsorption of P protein to the adsorption layer in the three crystal sensors varies.

On the other hand, as shown in FIG. 7, in the embodiment, when the quartz crystal 2 after the P protein is adsorbed to the adsorption layer and the oscillation frequency of the quartz crystal 2 is changed is observed in the three quartz sensors 20, It can be seen that the quartz sensors are stable at substantially the same frequency. That is, it can be seen that there is almost no variation in the frequency stability of the crystal unit 2 after the oscillation frequency of the crystal unit 2 has changed due to the P protein adsorbing to the adsorption layer in the three crystal sensors 20.
B. Experimental example 2
(Example)
An experiment for confirming the frequency stability of the quartz sensor 20 was performed using the quartz sensor 20 described above. In this experiment, 0.12 ml of a pH 7.2 PBS solution as a reagent is injected into the injection port 53 of the crystal sensor 20, and the crystal resonator 2 after the environmental atmosphere of the crystal resonator 2 has changed from a gas phase to a liquid phase. The oscillation frequency is observed.

The above-described experiment was performed on each of the three crystal sensors 20. The experiment for each crystal sensor 20 is Example 1-1, Example 1-2, and Example 1-3, and the results are shown in FIG.
(Comparative example)
In the conventional quartz sensor shown in FIG. 11, that is, in the wiring board, a groove for accommodating the conductive adhesive is not formed in a portion where the extraction electrode on the back surface side of the crystal resonator and the electrode on the wiring board side face each other. First, an experiment was conducted to confirm the frequency stability of the quartz crystal sensor in the same manner as in the example using a quartz crystal sensor having a structure in which the quartz crystal resonator was placed on the wiring board via a conductive adhesive. This experiment was performed on three conventional quartz sensors, respectively. The experiment for each crystal sensor is referred to as Comparative Example 1-1, Comparative Example 1-2, and Comparative Example 1-3, and the results are shown in FIG.
(Results and discussion)
FIG. 9 shows the oscillation frequency of the crystal unit 10 minutes after the introduction of the reagent and 15 minutes after the introduction of the reagent in Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-3. The amount of change that is the difference between the oscillation frequency of the subsequent crystal resonator and the oscillation frequency of the crystal resonator 10 minutes after the reagent is added and the oscillation frequency of the crystal resonator 15 minutes after the reagent is added (ΔF), respectively. As shown in FIG. 9, the change amounts (ΔF) of Example 1-1, Example 1-2, and Example 1-3 are 0.32 Hz, 2.61 Hz, and 1.18 Hz, respectively. 1, the amount of change (ΔF) of Comparative Example 1-2 and Comparative Example 1-3 is 4.00 Hz, 3.75 Hz, and 4.65 Hz, respectively. From this result, the Example is more changed than the Comparative Example. It can be seen that (ΔF) is small. That is, it can be seen that the crystal sensor of the example has higher frequency stability of the crystal sensor than the crystal sensor of the comparative example. FIG. 10 shows the oscillation frequency of the crystal unit after the environmental atmosphere of the crystal unit in Example 1-1 and Comparative Example 1-1 has changed from the gas phase to the liquid phase. As shown in FIG. 10, the frequency of the quartz sensor of the comparative example is gradually increased, whereas the frequency of the quartz sensor of the embodiment does not increase and is stable.

1 is a perspective view of a crystal sensor according to an embodiment of the present invention. It is a disassembled perspective view of the crystal sensor. It is a vertical side view of the crystal sensor. It is a perspective view of the back surface side of the crystal pressing member which comprises the said crystal sensor. It is a block diagram of the sensing apparatus containing the said quartz sensor. It is a perspective view of the sensing device. It is explanatory drawing which shows the experimental result performed in order to confirm the effect of this invention. It is explanatory drawing which shows the experimental result performed in order to confirm the effect of this invention. It is explanatory drawing which shows the experimental result performed in order to confirm the effect of this invention. It is explanatory drawing which shows the experimental result performed in order to confirm the effect of this invention. It is a schematic vertical side view which shows the principal part of the conventional quartz sensor.

Explanation of symbols

20 Crystal sensor 2 Crystal oscillator 21 Crystal pieces 22 and 23 Excitation electrodes 24 and 25 Extraction electrode 3 Wiring board 4 Crystal pressing member 43 Annular projection 44 Opening 45 Liquid storage space 5 Liquid injection cover 6 Measuring instrument body 7 Groove 8 Conductive adhesive

Claims (2)

In the piezoelectric sensor that is electrically connected to the measuring instrument body to detect the measurement object in the sample liquid,
A wiring board provided with a connection terminal portion connected to the measuring instrument main body, and on one surface side thereof, an electrode electrically connected to the connection terminal portion and a recess for configuring an airtight space;
One excitation electrode and the other excitation electrode are formed on one surface side and the other surface side of the plate-shaped piezoelectric piece, respectively, and are connected to one excitation electrode on the one surface side, and from one surface side of the piezoelectric piece, the piezoelectric piece One extraction electrode drawn to the other side through the end, and the other extraction electrode connected to the other excitation electrode on the other side and drawn to the end of the piezoelectric piece are formed, A piezoelectric vibrator provided on the wiring substrate in a state in which the other excitation electrode on the other surface side faces the concave portion and a liquid storage space having a bottom surface on one surface side of the piezoelectric vibrator is formed. A pressing member made of an elastic material provided to surround the liquid storage space and provided with an annular protrusion for pressing the outer portion of the concave portion on one surface side of the crystal resonator against the wiring board side ;
A cover for covering the pressing member facing the wiring board, communicating with the liquid storage space on the surface thereof, and a liquid injection cover provided with an injection port for injecting a sample liquid into the liquid storage space;
The annular protrusion is configured such that the diameter decreases as the inner peripheral surface surrounding the liquid storage space faces downward ,
The wiring board includes a recess for accommodating a conductive adhesive at a portion where the one extraction electrode and the other extraction electrode and the electrode face each other,
The conductive adhesive in the recess and the extraction electrode are bonded in a state where the peripheral edge of the piezoelectric piece is in close contact with the wiring substrate, and the extraction electrode and the electrode are electrically connected. Piezoelectric sensor.   The piezoelectric sensor according to claim 1, and a measuring instrument body that detects a natural frequency of the piezoelectric vibrator and detects a measurement object in the sample liquid based on the detection result. Sensing device.

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