JP2010185890A - Piezoelectric sensor and sensing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric sensor with improved detection capability and a sensing device including this piezoelectric sensor. <P>SOLUTION: The piezoelectric sensor, which keeps electrodes each including a gold layer respectively formed by sputtering on one surface side and the other surface side of a piezoelectric piece through joining layers, an adsorbing layer including an antibody provided on the surface of the electrode on one surface side, and the electrode on the other surface side being provided so as to face an airtight space to detect the antigen adsorbed by the antibody according to a change in the frequency of the piezoelectric piece, includes: a conductive passage through which the electrodes and an oscillation circuit are connected; and a conductive adhesive, provided so as to straddle the conductive passage from the electrodes in order to fix the electrodes to the conductive passage, in which a binder is cured with a conductive filler joined to the gold layer. The thickness of the gold layer is set to be 3,000 Å or above. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, an adsorption layer made of an antibody is provided on the surface of an electrode formed on one side of a piezoelectric piece, and an antigen adsorbed on the antibody by an antigen-antibody reaction is detected according to a change in the frequency of the piezoelectric piece. The present invention relates to a piezoelectric sensor and a sensing device using the piezoelectric sensor.

  In order to detect trace substances in the sample liquid, for example, environmental pollutants such as mouse IGg or disease markers such as hepatitis C virus and C-reactive protein (CPR), and to measure these substances, crystals A measurement method using a crystal sensor including a vibrator and a measuring instrument that is electrically connected to the crystal sensor and includes an oscillation circuit for oscillating the crystal vibrator is widely known (for example, Patent Document 1).

  Specifically, the measurement method includes, for example, a plate-shaped crystal piece and 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 crystal sensor including a crystal resonator called a Langevin type with an electrode is configured so that the electrode on one side contacts the measurement atmosphere (sample liquid) and the electrode on the other side faces the airtight space. An antibody that captures an antigen by an antigen-antibody reaction is formed as an adsorption layer on the surface of the electrode, and the antigen is captured in this adsorption layer, and the characteristic that the natural frequency of the quartz crystal varies according to the amount of adsorption is utilized. Is. Then, the difference between the natural frequency of the crystal unit before the antigen is adsorbed on the adsorption layer and the natural frequency of the crystal unit after the antigen is adsorbed on the adsorption layer, that is, the amount of change is obtained. The presence or concentration of the measurement object is detected.

  FIG. 10 shows an example of the configuration around the crystal resonator provided in the crystal sensor. In FIG. 10, reference numeral 11 denotes a wiring board, and the crystal resonator 10 is placed on the wiring board 11. In this crystal resonator 10, excitation electrodes 13 are provided on one side and the other side of a plate-like crystal piece 12, and the electrode 13 is provided with a conductive adhesive 14 made of a conductive filler and a binder. And is electrically connected to an electrode 11a provided on the wiring board 11 side.

  Reference numeral 15 in FIG. 10 denotes a through hole formed in the wiring substrate 11 in the thickness direction, and reference numeral 15 a in FIG. 10 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 10 forms an airtight space, and the electrode 13 on the back surface side of the crystal resonator 10 faces the airtight space. Reference numeral 16 in FIG. 10 denotes a plate-like crystal pressing member made of rubber or the like, and presses the crystal resonator 10 against the substrate 11 to fix the position thereof.

  Reference numeral 17 in FIG. 10 denotes an opening provided so as to penetrate the crystal pressing member 16 in the thickness direction, and faces the electrode 13 on the surface side of the crystal resonator 10. Reference numeral 18 in FIG. 10 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 16 and the annular protrusion 18 so that the electrode 13 is in contact with the measurement atmosphere.

  Further, as shown in FIG. 11, the electrodes 13 provided on one side and the other side of the crystal piece 12 of the crystal unit 10 are generally composed of a gold (Au) layer 100 and, for example, chromium (Cr), nickel (Ni ) And the like and a base layer 101 made of a metal. These two layers are formed by sputtering, for example. The reason for using gold for the upper layer is to vibrate quartz efficiently, and the reason for using a metal such as chromium or nickel for the lower layer is to increase the adhesion between the gold layer 100 and the crystal piece 12. The film thickness of the gold layer 100 is set to 2000 mm in order to stably vibrate the crystal piece 12, and the film thickness of the base layer 101 is sufficient to ensure close contact between the crystal piece 12 and the gold layer 100. It is set to 100cm to get.

  Conventionally, a conductive adhesive 14 in which a conductive filler made of, for example, silver (Ag) is dispersed in a silicone resin as a binder for bonding between the electrode 11a of the wiring substrate 11 and the excitation electrode 13 of the crystal resonator 10 is used. Is used. However, in this conductive adhesive 14, since the resin around the surface portion of the gold layer 100 is cured after the resin around the Ag is cured first, the Ag bonded to the surface of the gold layer 100 is cured and contracted. It moves in the direction away from the surface of the gold layer 100, and as a result, a resin film is formed on the surface of the gold layer 100 and the conductivity is hindered. Therefore, by utilizing the fact that the metal of the underlayer 101 such as chromium is deposited on the surface of the gold layer 100 by thermal diffusion and the resin around the Ag and the resin around the Cr surface are cured at the same speed, The movement of Ag was suppressed (Patent Document 2).

However, in the quartz sensor, as shown in FIG. 11, the adsorption layer 202 is formed by adhering the antibody 201 that captures the antigen 200 by the antigen-antibody reaction to the surface of the electrode 13, so that if chromium is deposited on the surface of the gold layer 100, The following problems arise. That is, the antibody 201, such as protein, easily adheres to gold, but hardly adheres to chromium. Therefore, when chromium is deposited on the surface of the gold layer 100, the amount of the antibody 201 attached to the surface of the electrode 13 decreases, and the crystal sensor The detection ability of is reduced. Therefore, it is considered that such a thermal diffusion treatment is not performed and that the binder is cured as the conductive adhesive 14 with the conductive filler bonded to the surface of the gold layer 100. Specifically, a conductive adhesive 14 is used in which the conductive filler is, for example, silver and the binder is an epoxy resin. By the way, in recent years, there is a demand for detecting a very small amount of a substance such as dioxin in a quartz sensor, and it is necessary to meet this demand.

  On the other hand, in Patent Document 3, diffusion is performed on the surface of the electrode film in the bonding process in an annealing process, a molding process, or the like performed after the connection electrode (lead) is bonded to the electrode film formed on the surface of the crystal piece with solder. In order to prevent the solder component from diffusing into the electrode film, it is described that chromium is formed on the upper surface of the electrode film, and this chromium component is thermally diffused in the film thickness direction of the electrode film. In the present invention, it is described that the film thickness of the electrode film is set to 1000 mm or more and 5000 mm or less, but the above-described problem is not described at all.

JP 2001-194866 A JP 2000-151345 (paragraph 0006 to paragraph 0008, paragraph 0014 and paragraph 0015) JP 2002-50937 (paragraph 0012 and paragraph 0067)

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an adsorption layer made of an antibody on the surface of an electrode formed on one side of a piezoelectric piece and to adsorb the antibody by an antigen-antibody reaction. In the piezoelectric sensor for detecting the detected antigen according to the change in the vibration frequency of the piezoelectric piece, the detection capability of the piezoelectric sensor is to be improved.

In the present invention, an electrode made of a gold layer is formed by sputtering through an adhesion layer on one side and the other side of the piezoelectric piece, and an adsorption layer made of an antibody is provided on the surface of the electrode on the one side. In the piezoelectric sensor for detecting the antigen adsorbed to the antibody by the antigen-antibody reaction according to the change in the frequency of the piezoelectric piece, the electrode on the other side is provided so as to face the airtight space,
A conductive path for connecting the electrode and the oscillation circuit;
A conductive adhesive that is provided across the conductive path from the electrode to fix the electrode to the conductive path, and the binder is cured in a state where a conductive filler is bonded to the gold layer;
The gold layer has a thickness of 3000 mm or more.

  In the above-described piezoelectric sensor, it is preferable that the conductive filler is at least one selected from, for example, silver and gold, and the binder is, for example, an epoxy resin. The adhesion layer is preferably at least one selected from, for example, chromium, titanium, nickel, aluminum, and copper.

  According to the present invention, in the electrode formed on the surface of the piezoelectric piece, the thickness of the gold layer is set to 3000 mm or more, so that the adsorption layer formed on the surface of the gold layer as shown in the examples to be described later. Increased amount of antigen adsorption. This is because the surface of the gold layer is roughened by increasing the thickness of the gold layer by depositing gold atoms by sputtering, the contact area with the antibody on the gold layer surface is increased, and an adsorption layer is formed on the surface of the gold layer. It is presumed that the amount of antibody adhering to the surface of the gold layer has increased. That is, by increasing the thickness of the gold layer, the amount of antibody adhering to the gold layer surface increases, and it is considered that a large amount of antigen can be captured by the antibody.

It is a longitudinal cross-sectional view of the crystal sensor which concerns on embodiment of this invention. It is sectional drawing which showed the structure of the crystal piece which concerns on embodiment of this invention. It is an idea figure explaining the adsorption layer formed in the electrode surface of the said crystal piece. It is an idea figure explaining formation of an adsorption layer in the gold layer surface. It is a perspective view of the crystal sensor. It is a disassembled perspective 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 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. It is an idea figure explaining the adsorption layer formed in the electrode surface of the crystal piece shown in FIG.

  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 longitudinal sectional view showing a quartz sensor 20 which is an example of a piezoelectric sensor according to the present invention, and FIG. 2 is a plan view showing the structure of a quartz vibrator 2 which is a piezoelectric vibrator provided in the piezoelectric sensor. It is. 5 is a perspective view of the crystal sensor 20, and FIG. 6 is an exploded perspective view showing the upper surface side of each component of the crystal sensor 20. As shown in FIG. As shown in FIGS. 1, 5, and 6, the quartz sensor 20 has a sealing member 3A, a wiring board 3, a quartz vibrator 2, a quartz pressing member 4, and a liquid injection cover 5 that are stacked in this order from the bottom. It is constituted by.

  As shown in FIG. 1, the crystal resonator 2 has excitation electrodes 22 and 23 formed on one side and the other side of a crystal piece 21 which is a piezoelectric piece. The electrode 22 formed on the one surface side of the crystal piece 21 is continuously formed on the peripheral portion on the other surface side, and the electrode 23 formed on the other surface side of the crystal piece 21 is continuously formed on the peripheral portion on the one surface side. ing. As shown in FIG. 2, the electrodes 22 and 23 are composed of a gold (Au) layer 70 for efficiently vibrating the quartz crystal, for example, chromium (Cr) for increasing the fixing force between the gold layer 70 and the crystal piece 21, An underlayer 71 that is an adhesion layer made of a metal selected from titanium (Ti), nickel (Ni), aluminum (Al), and copper (Cu) is laminated in order from the underlayer 71.

The thickness of the gold layer 70 is set to 3000 mm or more, and in this example, 3000 mm. By setting the thickness of the gold layer 70 to such a size, the gold layer 70 is formed as shown in the examples described later. The adsorption amount of the antigen 74 with respect to the adsorption layer 7 formed on the surface of 70 increases. The reason why the adsorption amount of the antigen 74 on the adsorption layer 7 is increased is that the gold layer 70 is deposited on the surface of the base layer 71 by sputtering to increase the thickness of the gold layer 70 as described later. New gold atoms are deposited on the deposited gold atoms, and this deposition is repeated to form a 3000-thick gold layer 70. As a result, the surface of the gold layer 70 becomes rough and the surface of the gold layer 70 is reduced. It is presumed that the contact area with the antibody 72 is increased, and the amount of the antibody 72 adhering to the surface of the gold layer 70 is increased in forming the adsorption layer 7 on the surface of the gold layer 70 as will be described later.

The upper limit value of the thickness of the gold layer 70 is 10,000 mm, and if it is larger than this, an oscillation frequency jump tends to occur in the crystal unit 2. In addition, the thickness of the underlayer 71 is set to 10 to 500 mm, and in this example, 100 mm in order to obtain sufficient adhesion between the crystal piece 21 and the gold layer 70. The electrodes 22 and 23 are formed by, for example, laminating a base layer 71 and a gold layer 70 in this order on both surfaces of the crystal piece 21 in this order, and then forming a mask with a predetermined pattern on both surfaces of the crystal piece 21 and performing etching. A layered electrode pattern is obtained.

  As will be described later, since the electrode 22 is provided so as to face the liquid storage space 45 to which the sample liquid is supplied, the antigen 74 is captured on the electrode 22 by an antigen-antibody reaction as shown in FIG. The antibody 72 is formed as the adsorption layer 7, and a blocking substance (block body) 73 is adsorbed in the gap between the antibodies 72 so that the antigen 74 as the measurement target is not adsorbed on the surface of the electrode 22. .

Here, the formation of the adsorption layer 7 on the surface of the gold layer 100 will be described in detail. In the present embodiment, as described above, gold is deposited on the surface of the base layer 71 by sputtering to form a gold layer 70 having a thickness of 3000 mm, so that the surface of the gold layer 70 is roughened and the gold layer 70 is formed. Since the contact area with the antibody 72 on the surface is increased, a large number of antibodies 74 adhere to the surface of the gold layer 70 as shown in FIG. On the other hand, since the gold layer 100 constituting the electrode 13 of the crystal resonator 12 used in the conventional quartz sensor has a smaller thickness than the gold layer 70 of this embodiment, the surface of the gold layer 100 is almost rough. First, as shown in FIG. 4B, the amount of antibody 201 attached to the surface of the gold layer 100 is smaller than the amount of antibody 74 attached to the surface of the gold layer 70 of this embodiment. That is, increasing the thickness of the gold layer 70 increases the amount of antibody 74 attached to the surface of the gold layer 70.

  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, as shown in FIG. 1, a conductive adhesive 8 made of a conductive filler and a binder is attached to a portion of the wiring board 3 where the electrodes 31 and 32 are provided. The electrodes 22, 23 formed on the peripheral edge of the other surface 21 overlap the electrodes 31, 32 on the wiring board 3 side through the conductive adhesive 8. The conductive adhesive 8 is one in which the binder is cured in a state where the conductive filler is bonded to the surface of the gold layer 100. Specifically, the conductive filler is, for example, silver and gold, in this example, silver (Ag ), A conductive adhesive 8 whose binder is made of an epoxy resin is used.

Here, the conductive adhesive 8 used in the present embodiment will be described in detail. Since the conductive adhesive 8 uses an epoxy resin having a high curing speed as a binder, the timing at which the resin around the Ag and the resin around the surface portion of the gold layer 70 are hardly changed. As a result, the Ag However, the resin is quickly cured in a state where the resin is bonded to the surface of the gold layer 70. Therefore, in the conductive adhesive 8 used in this embodiment, as described in the item of the prior art, the curing rate of the resin around the surface portion of the gold layer 100 is higher than the curing rate of the resin around Ag. Due to the slowness, the phenomenon that Ag that has been bonded to the surface of the gold layer 70 moves away from the surface of the gold 100 due to curing shrinkage does not occur.

  Returning to the description of the wiring board 3, a through-hole 33 is formed between the electrodes 31 and 32 of the wiring board 3 so as to be spaced from the electrodes 31 and 32 in the thickness direction of the wiring board 3. Has been. As will be described later, the through-hole 33 constitutes a recess that forms an airtight space where the electrode 23 on the back surface side of the crystal resonator 2 faces. 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.

  In FIG. 6, reference numeral 36 denotes a weir. The weir 36 has a role of aligning the crystal resonator 2, and the crystal resonator 2 is placed in a region surrounded by the weir 36. In FIG. 6, 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. In addition, 38a, 38b, and 38c in FIG. 6 are notches formed on the periphery of the wiring board 3, and are respectively formed on the claw portions 52a, 52b, and 52c bent inward provided on the periphery of the lower surface of the cover 5. Engage. 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.

  In FIG. 6 and FIG. 7, reference numeral 4 denotes a crystal pressing member, and the crystal pressing member 4 has a plate-like shape having rectangular cutout portions 41a, 41b, and 41c respectively corresponding to the cutout portions 38a, 38b, and 38c. Is formed. Further, as shown in FIGS. 1 and 7, a recess 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 in the center of the ceiling surface portion (bottom surface portion in the case of description in FIG. 7) of the recess 42. 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 44 a of the opening 44 and the inner peripheral surface 43 a of the annular protrusion 43 are inclined inward and downward, and the tip portion 47 of the annular protrusion 43 presses the peripheral edge of the crystal piece 20. A region 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. 6 are engagement holes that 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. 6, 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.

  A sample solution injection port 53 and a confirmation port 54 are formed on the front and rear sides of the upper surface of the cover 5, respectively. An injection path 55, which is a groove, is formed in the lower surface of the cover 5 along the length direction of the cover 5. One end and the other end of the injection path 55 are connected to the injection port 53 and the confirmation port 54, respectively. ing. 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. An annular weir 56 surrounding the injection path 55 is provided on the lower surface of the cover 5 to prevent leakage of the sample solution.

  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 to the surfaces of the electrodes 31 and 32 of the wiring board 3. Thereafter, the electrodes 22 and 23 formed on the peripheral portion on the other surface side of the crystal piece 21 overlap the electrodes 31 and 32 on the wiring substrate 3 side, and are formed on the center portion on the other surface side of the crystal piece. The crystal resonator 2 is placed on the wiring board 3 so that 23 overlaps the recess.

  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 also 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 portion 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 electrode 23 formed at the center portion on the other surface side of the crystal piece 21 While facing the space, the conductive adhesive 8 formed on the surfaces of the electrodes 31 and 32 of the wiring board 3 and the electrodes 22 and 23 formed on the peripheral portion on the other surface side of the crystal piece 21 are bonded to each other. 22 and 23 and the electrodes 31 and 32 on the wiring board 3 side are electrically connected to each other.

  Next, the operation of the above-described quartz sensor 20 will be described. First, the operator injects the sample liquid into the injection port 53 of the liquid injection cover 5 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 electrode 22 on the surface side of the crystal unit 2 is in contact with the sample liquid. The antigen 74 in the sample solution is adsorbed by the antigen-antibody reaction to the adsorption layer 7 made of the antibody 72 formed on the surface of the electrode 22. When the antigen 74 is adsorbed on the adsorption layer 7, the natural frequency of the crystal unit 2 is reduced according to the amount of adsorption of the antigen 74. As a result, the difference between the natural frequency of the crystal unit 2 before the antigen 74 is adsorbed on the adsorption layer 7 and the natural frequency of the crystal unit 2 after the antigen 74 is adsorbed on the adsorption layer 7, that is, the amount of change is obtained. .

  According to the above-described embodiment, the gold layer 70 has a thickness of 3000 mm, in this example 3000 mm, in the electrodes 22 and 23 formed on the surface of the crystal piece 21, so that the gold layer 70 is shown in the examples described later. The adsorption amount of the antigen 74 to the adsorption layer 7 formed on the surface of the layer 70 is increased. This is because, as described above, gold atoms are deposited on the surface of the base layer 71 by sputtering to increase the thickness of the gold layer 70, that is, new gold atoms are deposited on the irregularly deposited gold atoms. This deposition is repeated to form a 3000-mm gold layer 70. As a result, the surface of the gold layer 70 becomes rough and the contact area with the antibody 72 on the surface of the gold layer 70 increases, as described later. It is presumed that the amount of antibody 72 adhering to the surface of the gold layer 70 has increased in forming the adsorption layer 7 on the surface of the layer 70. That is, by increasing the thickness of the gold layer 70, it is considered that the amount of the antibody 72 attached to the surface of the gold layer 70 increases, so that more antigen 74 can be captured by the antibody 72.

  In the above-described embodiment, the following effects can be obtained by setting the thickness of the gold layer 70 to 3000 mm or more, in this example 3000 mm. The metal, for example, chromium, of the underlayer 71 used to increase the adhesion between the gold layer 70 and the crystal piece 21 gradually diffuses into the gold layer 70 over time. When the thickness of the gold layer 100 is 2000 mm as in the conventional quartz sensor shown in FIGS. 11 and 12, chromium is deposited on the surface of the gold layer 100 in half to one year, and the gold layer 100 is deposited by the deposited chromium. The antibody 201 adhering to the surface of the gold was detached and the service life of the quartz sensor was shortened. However, by setting the thickness of the gold layer 70 to 3000 mm, chromium is deposited on the surface of the gold layer 100. Since this takes more than one year, this has the effect of extending the service life of the quartz sensor.

  Further, the above-described quartz sensor 20 is used as a detection unit of a sensing device by being connected to a measuring device body 7 having a configuration as shown in FIG. 8 which is a block diagram, for example. In FIG. 8, 62 is an oscillation circuit that oscillates the crystal piece 21 of the crystal sensor 20, 63 is a reference clock generation unit that generates a reference frequency signal, and 64 is a frequency difference detection means that includes, for example, a heterodyne detector. 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.

  Since the frequency of the quartz sensor 20 is 9.2 MHz, for example, 10 MHz is selected as the frequency of the reference clock generator 63. When the antigen 74 that is the measurement object, for example, dioxin, is not adsorbed on the adsorption layer 7 provided on the quartz crystal resonator 2 of the quartz sensor 20, the frequency difference detecting means 64 uses the frequency and the reference from the quartz sensor side. A frequency signal (frequency difference signal) of 1 MHz, which is a difference from the clock frequency, is output. When the antigen 74 contained in the sample solution is adsorbed to the adsorption layer 7 of the crystal resonator 2, the natural vibration of the crystal resonator 2 is output. Since the number changes, and therefore 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.

An experiment conducted for confirming the effect of the present invention will be described.
Example 1
In the crystal sensor 20 shown in FIG. 1, the adsorption layer 7 was formed by the antibody 72 on the surface of the electrode 22 having a gold layer 70 having a thickness of 3000 mm and a base layer 71 having a thickness of 100 mm. The adsorption layer 7 was formed as follows. First, 0.2 ml of a buffer solution is supplied into the liquid storage space 45, and then a sample solution containing 100 μg / ml of a protein called BSA (bovine serum albumin), which is the antibody 72, is added to the liquid storage space 45. 2 ml was supplied. Thereby, the antibody 72 adheres to the electrode 22 surface, and the adsorption layer 7 is formed.
After the adsorption layer 7 was formed, 1 ml of a sample solution containing 10 μg / ml of antigen 74, for example, mouse IGg, was injected into the injection port 53 of the crystal sensor. Then, the amount of the antigen 74 adsorbed on the adsorption layer 7 on the surface of the electrode 22 is determined based on the natural frequency of the crystal resonator 2 before the antigen 74 is adsorbed on the adsorption layer 7 and the crystal after the antigen 74 is adsorbed on the adsorption layer 7. It was obtained by taking the difference from the natural frequency of the vibrator 2.
(Example 2)
The adsorption layer 7 is formed in the same manner as in Example 1 except that the thickness of the gold layer 70 is 4000 mm. Thereafter, a sample solution containing mouse IGg is injected to adsorb the adsorption layer 7 on the surface of the electrode 22. The amount of the antigen 74 adsorbed on was determined.
(Example 3)
The same test as in Example 2 was performed except that the thickness of the gold layer was 5000 mm.
Example 4
The same test as in Example 2 was performed except that the thickness of the gold layer was 6000 mm.
(Example 5)
The same test as in Example 2 was performed, except that the thickness of the gold layer was changed to 7000 mm.
(Comparative Example 1)
The adsorption layer 7 was formed in the same manner as in Example 1 except that the thickness of the gold layer 70 was changed to 1000 mm, and then a sample solution containing mouse IGg was injected to adsorb the adsorption layer 7 on the surface of the electrode 22. The amount of the antigen 74 adsorbed on was determined.

(Comparative Example 2)
The adsorption layer 7 was formed in the same manner as in Example 1 except that the thickness of the gold layer 70 was 2000 mm, and then a sample solution containing mouse IGg was injected to adsorb the adsorption layer 7 on the surface of the electrode 22. The amount of the antigen 74 adsorbed on was determined.
(Results and discussion)
As shown in FIG. 9, the adsorption amounts of the antigens 74 of Examples 1 to 5 were 9.8 ng / cm ² , 11.0 ng / cm ² , 11.7 ng / cm ² , 12.0 ng / cm ² and 12.2 ng / cm ² . The adsorption amount of the antigen 74 of Comparative Example 1 and Comparative Example 2 was 6.5 ng / cm ² and 8.0 ng / cm ^2. That is, it can be seen that the amount of the antigen 74 adsorbed on the adsorption layer 7 formed on the surface of the gold layer 100 increases by increasing the thickness of the gold layer 100. As described above, when gold atoms are deposited on the surface of the underlayer 71 by sputtering and the thickness of the gold layer 70 is increased as described above, the surface of the gold layer 70 becomes rough accordingly, and the antibody 201 on the surface of the gold layer 70 is increased. This is presumed to be because the contact area with the surface of the gold layer 100 increases and the amount of antibody 72 attached to the surface of the gold layer 100 increases. Therefore, it can be seen that when the thickness of the gold layer 100 is 3000 mm or more, the amount of the antibody 72 attached increases and high sensitivity can be obtained for the piezoelectric sensor. In addition, the Cerbury equation was used as the equation for obtaining the reaction amount based on the measurement frequency.

20 Crystal sensor 2 Crystal oscillator 21 Crystal piece 22 and 23 Electrode 3 Wiring board 4 Crystal holding member 45 Liquid storage space 5 Liquid injection cover 6 Measuring instrument body 7 Adsorption layer 70 Gold layer 71 Underlayer 72 Antibody 73 Block body 74 Antigen

Claims (4)

Electrodes made of a gold layer are formed on the one surface side and the other surface side of the piezoelectric piece by sputtering through an adhesion layer, respectively, and an adsorption layer made of an antibody is provided on the surface of the electrode on the one surface side. In the piezoelectric sensor for detecting the antigen adsorbed to the antibody by the antigen-antibody reaction according to the change in the frequency of the piezoelectric piece, the electrode is provided to face the airtight space,
A conductive path for connecting the electrode and the oscillation circuit;
A conductive adhesive that is provided across the conductive path from the electrode to fix the electrode to the conductive path, and the binder is cured in a state where a conductive filler is bonded to the gold layer;
The piezoelectric sensor according to claim 1, wherein the gold layer has a thickness of 3000 mm or more.   The piezoelectric sensor according to claim 1, wherein the conductive filler is at least one selected from silver and gold, and the binder is an epoxy resin.   The piezoelectric sensor according to claim 1, wherein the adhesion layer is at least one selected from chromium, titanium, nickel, aluminum, and copper.   A piezoelectric sensor according to any one of claims 1 to 3, and a measuring instrument main body that detects the natural frequency of the piezoelectric vibrator and detects an antigen based on the detection result. Sensing device.

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