Biosensor and method for manufacturing a biosensor
The biosensor's innovative design with shared electrodes and a piezoelectric element enables accurate and compact measurement of biological information by simplifying the sensor configuration.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- NOK CORP
- Filing Date
- 2025-01-16
- Publication Date
- 2026-07-29
AI Technical Summary
Existing biosensors face challenges in improving accuracy and miniaturization due to the need for multiple sensors to measure biological surface displacements, leading to increased complexity and size.
A biosensor design featuring a piezoelectric element with multiple first electrodes on one surface and a shared second electrode on the opposite surface, allowing for detection of biological information at multiple locations while simplifying and miniaturizing the device.
The proposed design enhances detection accuracy by allowing simultaneous measurement at multiple points, reduces errors, and minimizes the biosensor's size and complexity compared to traditional configurations.
Smart Images
Figure 2026122563000001_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the technology of biosensors.
Background Art
[0002] Various techniques for detecting biological information such as pulse rate, pulse wave propagation time, pulse wave velocity (PWV), or blood pressure have been proposed conventionally. In Non-Patent Document 1, a method of obtaining biological information by measuring displacements of the biological surface due to pulsations of blood vessels from two independent pulse sensors installed at intervals in a local area such as the wrist or neck has been reported. Also, in Non-Patent Document 2, a method of estimating blood pressure from the pulse wave propagation time of a subject has been reported.
Prior Art Documents
Non-Patent Documents
[0003]
Non-Patent Document 1
Non-Patent Document 2
Summary of the Invention
Problems to be Solved by the Invention
[0004] However, in order to improve the accuracy of detecting biological information, it is necessary to increase the number of locations where displacement of the biological surface is measured. Increasing the number of measurement locations requires increasing the number of biosensors. Therefore, in a configuration in which multiple sensors, each composed of a stack of piezoelectric elements, a first electrode, and a second electrode, are installed individually and spaced apart from each other, the complexity or size of the biosensor becomes a problem. Thus, one aspect of this disclosure aims to simplify and miniaturize the biosensor. [Means for solving the problem]
[0005] To solve the above problems, a biosensor according to one aspect of the present disclosure comprises a piezoelectric element including a first surface facing a living body and a second surface opposite the first surface, a plurality of first electrodes formed on the first surface at intervals from each other, and a second electrode formed on the second surface that overlaps the plurality of first electrodes in a plan view.
[0006] A method for manufacturing a biosensor according to one aspect of the present disclosure includes the steps of forming a plurality of first electrodes spaced apart from each other on a first surface of a piezoelectric element that faces a living organism, and forming a second electrode on a second surface opposite the first surface that overlaps the plurality of first electrodes in a plan view. [Brief explanation of the drawing]
[0007] [Figure 1] This is a schematic diagram of the biometric measurement system in the first embodiment. [Figure 2] This is a plan view of the detection substrate in the first embodiment. [Figure 3] This is a cross-sectional view of the detection substrate in the first embodiment. [Figure 4] This is a plan view of the wiring board in the first embodiment. [Figure 5] This is a cross-sectional view of the biosensor in the first embodiment. [Figure 6] This is a flowchart illustrating the manufacturing method of the detection substrate in the first embodiment. [Figure 7] This is a schematic diagram illustrating the use of the biosensor in the first embodiment. [Figure 8] This graph visualizes the waveforms of each detection signal received by the control device in the first embodiment. [Figure 9] This graph shows the correlation between the known distance between two detection units and the time difference Tp in the first embodiment. [Figure 10] This is a cross-sectional view of the detection substrate in the second embodiment. [Figure 11] This is a plan view of the detection substrate in the third embodiment. [Figure 12] This is a cross-sectional view of the detection substrate in the third embodiment. [Modes for carrying out the invention]
[0008] The embodiments for implementing this disclosure will be described with reference to the drawings. Note that the dimensions and scale of the elements in each drawing may differ from those of the actual product. Furthermore, the embodiments described below are illustrative examples of embodiments that may be envisioned when implementing this disclosure. Therefore, the scope of this disclosure is not limited to the embodiments exemplified below.
[0009] A: First Embodiment Figure 1 is a schematic diagram of the bio-measurement system 100 in the first embodiment. The bio-measurement system 100 is a system that detects minute displacements of the biological surface due to vascular pulsation and analyzes biological information such as pulse rate, pulse wave propagation time, or blood pressure. The bio-measurement system 100 includes a biosensor 1 and a control device 2. In the following description, the horizontal direction in Figure 1 is referred to as the X direction, and one direction perpendicular to the X direction is referred to as the Y direction. The X direction is an example of the "first direction," and the Y direction is an example of the "second direction."
[0010] The biosensor 1 is a device that detects minute displacements of the biological surface caused by blood vessel pulsation. As shown in Figure 1, the biosensor 1 of the first embodiment includes a detection substrate 10 and a wiring substrate 20.
[0011] FIG. 2 is a plan view of the detection substrate 10 of the biosensor 1 according to the present embodiment. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. The detection substrate 10 is a part that converts the displacement of the living body surface into voltage. As shown in FIG. 2 or FIG. 3, the detection substrate 10 includes a piezoelectric element 11, a plurality of first electrodes 15, and a second electrode 16.
[0012] The piezoelectric element 11 is a piezoelectric body in which a voltage is generated by the displacement of the living body surface propagating through the plurality of first electrodes 15. As shown in FIG. 2, the planar shape of the piezoelectric element 11 is a long rectangle along the X direction. As shown in FIG. 3, the piezoelectric element 11 is a flat plate-like member. For the material of the piezoelectric element 11, for example, lead zirconate titanate (Pb(Zr,Ti)O3), polyvinylidene fluoride, or polylactic acid can be used. The piezoelectric element 11 includes a first surface 12 facing the living body and a second surface 13 on the opposite side thereof. In the following description, the direction from the first surface 12 to the second surface 13 is defined as the Z direction. The Z direction is perpendicular to the X-Y plane. In the following description, observing an object along the line of sight in the Z direction is referred to as "plan view".
[0013] The displacement of the living body surface propagates to the piezoelectric element 11 through the plurality of first electrodes 15. As shown in FIG. or FIG. 3, the plurality of first electrodes 15 are formed on the first surface 12 of the piezoelectric element 11 and are arranged at equal intervals in the X direction with intervals between them. As shown in FIG. 2, the planar shape of each of the plurality of first electrodes 15 is a long rectangle in the Y direction. As the material of the first electrode, for example, a conductive material such as silver paste, conductive ink, or conductive rubber is preferable. However, the material of the first electrode 15 is not limited to the above examples.
[0014] As shown in FIG. 2, the planar size of the piezoelectric element 11 exceeds the combined planar size of all the plurality of first electrodes 15. Also, as shown in FIG. 3, the plate thickness of the first electrode 15 is thinner than the plate thickness of the piezoelectric element 11. However, the relationship between the plate thickness of the first electrode 15 and the plate thickness of the piezoelectric element 11 is not limited to the above examples.
[0015] The second electrode 16 is a common electrode formed on the second surface 13 of the piezoelectric element 11 and continuous across the plurality of first electrodes 15. As shown in FIG. 2, the planar shape of the second electrode 16 is a rectangle elongated in the X direction. As shown in FIG. 3, the second electrode 16 is a flat plate-like member. The plurality of first electrodes 15 and the second electrode 16 overlap in a plan view. That is, the detection substrate 10 is a structure in which the first electrode 15, the piezoelectric element 11, and the second electrode 16 are laminated in the Z direction in the above order.
[0016] As shown in FIG. 2, the planar size of the second electrode 16 exceeds the planar size of the piezoelectric element 11. Specifically, the peripheral portion of the second electrode 16 projects outward from the periphery of the piezoelectric element 11 over the entire circumference. Also, as shown in FIG. 3, the plate thickness of the second electrode 16 is the same as the plate thickness of the piezoelectric element 11. However, the relationship between the plate thickness of the second electrode 16 and the plate thickness of the piezoelectric element 11 is not limited to the above examples. For example, there may be a configuration in which the second electrode 16 is thicker than the piezoelectric element 11, or a configuration in which the piezoelectric element 11 is thicker than the second electrode 16. As the material of the second electrode 16, a conductive metal material such as stainless steel can be used. However, it is not limited to the above examples.
[0017] As shown in FIG. 3, the portion where the first electrode 15, the piezoelectric element 11, and the second electrode 16 are laminated is defined as the detection unit 19. That is, the biosensor 1 includes a plurality of detection units 19. The displacement of the living body surface propagates to the piezoelectric element 11 through each first electrode 15. That is, the piezoelectric element 11 is displaced in conjunction with the living body surface. A voltage (hereinafter referred to as "detection voltage") corresponding to the displacement amount of the piezoelectric element 11 is generated between the first electrode 15 and the second electrode 16. Therefore, each of the plurality of detection units 19 generates a detection voltage. Each detection voltage generated by each detection unit 19 is output as a detection signal to the control device 2 via the wiring substrate 20.
[0018] As shown in Figure 1, the wiring board 20 is a mounting component that connects the detection board 10 and the control device 2 and outputs a detection signal to the control device 2. The wiring board 20 is a printed circuit board such as an FPC (Flexible Printed Circuit) or FFC (Flexible Flat Cable). Figure 4 is a schematic diagram of the wiring board 20 according to this embodiment. As shown in Figure 4, the wiring board 20 comprises a base material 21 and a plurality of wirings 22.
[0019] The substrate 21 is a flexible film-like substrate. The material of the substrate 21 may be a resin material such as polyimide (PI) or polyester (PET). However, the material of the substrate 21 is not limited to the examples given above. Multiple wirings 22 are formed on the substrate 21.
[0020] Specifically, the multiple wirings 22 are conductive patterns formed on the surface of the substrate 21 facing the first surface 12 of the piezoelectric element 11, as shown in Figure 1. The multiple wirings 22 are for connecting the detection substrate 10 and the control device 2. The multiple wirings 22 are made of a low-resistance conductive material such as a metal material. However, the above examples are not limiting. All of the multiple wirings 22 have the same width. The multiple wirings 22 include multiple first wirings 23 and multiple second wirings 26.
[0021] Multiple first wires 23 are connected to multiple first electrodes 15 on the detection board 10. Each of the multiple first wires 23 outputs the detection voltage generated at the corresponding first electrode 15 as a detection signal to the control device 2. As shown in Figure 1 or Figure 4, each of the multiple first wires 23 includes a first terminal 24 and a second terminal 25 on the opposite side of the first terminal 24.
[0022] Multiple first terminals 24 are arranged along the periphery of the substrate 21 that extends in the X direction on the positive side in the Y direction. Each of the multiple first terminals 24 is connected to a multiple first electrode 15. Specifically, as shown in Figure 1, each first terminal 24 is bonded to the first electrode 15 corresponding to that first terminal 24 so as to overlap in a plan view.
[0023] Figure 5 is a cross-sectional view of the VV line in Figure 1. Anisotropic Conducting Film (ACF27) is used to bond the detection substrate 10 and the wiring substrate 20. ACF27 is an adhesive film in which multiple conductive particles 28 are dispersed. By sandwiching the ACF27 between the detection substrate 10 and the wiring substrate 20 and heat-pressing them in the Z direction, the wiring substrate 20 and the detection substrate 10 are joined while electrically connecting the first electrode 15 and the first terminal 24. Specifically, as shown in Figure 5, the conductive particles 28 are crushed between the first electrode 15 and the first terminal 24, and the first electrode 15 and the first terminal 24 are electrically connected only in the direction along the Z direction. That is, adjacent first electrodes 15 and adjacent first terminals 24 are insulated from each other.
[0024] As shown in Figure 4, the multiple second terminals 25 are arranged along the periphery extending in the X direction on the negative side in the Y direction of the base material 21. That is, the second terminals 25 are located on the opposite side of the base material 21 from the first terminals 24. However, the second range W2 in which the multiple second terminals 25 are arranged is narrower than the first range W1 in which the multiple first terminals 24 are arranged. In other words, the multiple second terminals 25 are more concentrated than the multiple first terminals 24. Also, the first wiring 23 located at both ends in the X direction is longer than the first wiring 23 located in the center. The multiple second terminals 25 are each connected to the control device 2.
[0025] As shown in Figure 1 or Figure 2, the portion of the second electrode 16 located on the negative side in the Y direction (hereinafter referred to as the "protruding portion 17") protrudes from the negative edge in the Y direction of the piezoelectric element 11 to the negative side in the Y direction. As shown in Figure 1, the wiring board 20 of this embodiment is provided with two second wires 26, each connected to the protruding portion 17 of the second electrode 16. Specifically, one of the two second wires 26 is connected to one end of the protruding portion 17 in the X direction, and the other second wire 26 is connected to the other end of the protruding portion 17 in the X direction.
[0026] The second electrode 16 is supplied with a ground voltage via the second wiring 26. In a configuration where the ground voltage is supplied to only one end of the second electrode 16 in the X direction (hereinafter referred to as "proportional relationship"), a voltage difference may occur between the voltage at that end and the voltage at the other end. In this embodiment, since the second wiring 26 is connected to both ends of the second electrode 16, the voltage of the second electrode 16 in the X direction is made uniform compared to the proportional relationship. Therefore, the error in the detection voltage that occurs between the first electrode 15 and the second electrode 16 according to the displacement of the piezoelectric element 11 can be reduced.
[0027] As shown in Figure 5, the second wiring 26 and the second electrode 16 are electrically connected by the ACF 27 only in the direction along the Z direction, similar to the first terminal 24 and the first electrode 15.
[0028] Each detection unit 19 generates a detection voltage in conjunction with the displacement of the biological surface. The biosensor 1 outputs each generated detection voltage as a detection signal. The control device 2 acquires the detection signals from the biosensor 1 and generates biological information by analyzing the detection signals. Biological information includes information such as pulse rate, pulse wave propagation time, or blood pressure. The control device 2 comprises, for example, a receiving unit that receives the detection signals, an amplifier that amplifies the received detection signals, an A / D converter that converts the amplified analog detection signals into digital data, a computing unit that generates biological information from the digital data, and a display device that displays the biological information.
[0029] Figure 6 is a flowchart illustrating the manufacturing method of the detection substrate 10 according to the embodiment described above.
[0030] First, in the lamination process P1, a plurality of first electrodes 15 are formed on the first surface 12 of the piezoelectric element 11 that faces the living body, spaced apart from each other. As described above, the elastically deformable conductive material is formed into a long, flat plate shape in the Y direction and arranged with spacing between them in the X direction.
[0031] In the lamination process P2 following the lamination process P1, a second electrode 16 is formed on the second surface 13 of the piezoelectric element 11. As described above, a conductive metal material is formed in a flat plate shape, and the peripheral portion of the second electrode 16 protrudes outward from the periphery of the piezoelectric element 11 over its entire circumference.
[0032] Figure 7 is a schematic diagram of the biomedical measurement system 100 in use. As shown in Figure 7, for example, first, multiple first electrodes 15 on the detection substrate 10 are brought into contact with the biological surface (e.g., skin 3). Each of the multiple detection units 19 is brought into contact with a different part of the biological surface. Specifically, each first electrode 15 is brought into contact with the skin 3 such that the direction in which the multiple first electrodes 15 are arranged is aligned with the blood vessels (e.g., arteries 4) inside the skin 3. That is, the multiple first electrodes 15 and the arteries 4 overlap in a plan view.
[0033] The pulse wave of blood pumped from the heart propagates through artery 4. Artery 4 pulsates due to the blood pulse wave, causing displacement in the skin 3. As a result, each of the multiple first electrodes 15 is displaced sequentially in an order that is arranged toward the downstream side of artery 4. That is, each of the multiple detection units 19 generates a detection voltage sequentially in an order that is arranged toward the downstream side of artery 4. Each generated detection voltage is output to the control device 2 as a detection signal via the first wiring 23. The control device 2 may receive the detection signals from each of the multiple detection units 19 in a time-division manner, or it may receive the detection signals from the multiple detection units 19 in parallel.
[0034] Figure 8 is a graph visualizing the waveforms of each detection signal received by the control device 2. Each detection signal represents the pulse rate of the living body at the detected site. As shown in Figure 8, the time difference Tp of the pulse peak at a different site can be obtained as the pulse wave propagation time. The control device 2 estimates the blood pressure of the living body from the pulse wave propagation time. For blood pressure estimation, known techniques such as those described in Non-Patent Document 2 can be used.
[0035] Furthermore, for example, the pulse wave velocity (PWV) can be calculated from the known distance between two detection units 19 (hereinafter referred to as "electrode spacing") and the time difference Tp. Figure 9 is a graph showing the correlation between electrode spacing and time difference Tp. As shown in Figure 9, the longer the electrode spacing, the larger the time difference Tp becomes. Since the biosensor 1 of this embodiment includes three or more detection units 19, the combination of the two detection units 19 to be observed can be changed. Two detection units 19 of a specific combination can be selected from the multiple detection units 19, and the time difference Tp for the selected combination can be obtained. That is, the pulse wave propagation time for the selected combination can be obtained, so blood pressure can be estimated and the pulse wave velocity (PWV) can be calculated for each combination. Therefore, the detection accuracy of biological information can be improved compared to a configuration in which the biosensor 1 includes only two detection units 19.
[0036] In the first embodiment, the piezoelectric element 11 and the second electrode 16 are shared across multiple detection units 19. Compared to a configuration in which the piezoelectric element 11 or the second electrode 16 are installed spaced apart from each other in each detection unit 19, the configuration of the biosensor 1 can be simplified and miniaturized.
[0037] B: Second Embodiment A second embodiment of this disclosure will now be described. For elements whose function is the same as in the first embodiment in each of the embodiments described below, the same reference numerals as in the first embodiment will be used, and detailed descriptions of each will be omitted as appropriate.
[0038] Figure 10 is a cross-sectional view of the detection substrate 10 in the second embodiment. The detection substrate 10 in this embodiment further comprises an insulating sheet 18. The insulating sheet 18 is a film formed of, for example, an insulating resin material. As shown in Figure 10, the insulating sheet 18 covers each of the plurality of first electrodes 15. The first electrodes 15 and the insulating sheet 18 overlap in a plan view. That is, the insulating sheet 18 is provided between the first electrodes 15 and the biological surface. The plurality of first electrodes 15 are protected by being covered by the insulating sheet 18. Therefore, damage to the first electrodes 15 due to contact or collision with living organisms or other elements can be prevented.
[0039] Furthermore, the first electrode 15 and the biological surface are electrically insulated by the insulating sheet 18. Therefore, it is possible to reduce the amount of current flowing through the biological tissue among the current flowing between two adjacent first electrodes 15.
[0040] C: Third Embodiment A third embodiment of this disclosure will now be described. For elements whose function is the same as in the first embodiment in each of the embodiments described below, the same reference numerals as in the first embodiment will be used, and detailed descriptions of each will be omitted as appropriate.
[0041] Figure 11 is a plan view of the detection substrate 10 in the third embodiment. Figure 12 is a cross-sectional view taken along line XII-XII in Figure 11. As shown in Figure 11 or Figure 12, in this embodiment, slits 14 are formed between each of the multiple adjacent first electrodes 15 of the piezoelectric element 11. The slits 14 extend linearly over a wider area than the first electrodes 15 in the Y direction. Each slit 14 is a bottomed hole (i.e., a recess) formed in a part of the thickness direction of the piezoelectric element 11. However, the slits 14 may also be through holes that penetrate the piezoelectric element 11 in the thickness direction.
[0042] Furthermore, vibrations may propagate between adjacent detection units 19 via the piezoelectric element 11. In a configuration where vibrations propagate from other detection units 19 to each detection unit 19, it is difficult to generate a detection voltage that reflects only the displacement of the part of the biological surface corresponding to each detection unit 19. In other words, errors may occur in the detection voltage due to vibrations propagated from other detection units 19.
[0043] In the third embodiment, a slit 14 is formed between each of the multiple adjacent first electrodes 15 of the piezoelectric element 11. In this configuration, the slit 14 suppresses the propagation of vibrations generated in the first electrodes 15 and piezoelectric element 11 of each detection unit 19 to other detection units 19 adjacent to that detection unit 19. Therefore, errors in the detection voltage caused by vibrations propagated from other detection units 19 can be reduced.
[0044] D: Variant The following are examples of specific modifications that may be added to each of the embodiments exemplified above. Two or more embodiments may be arbitrarily selected from the following examples and merged as appropriate, provided they do not contradict each other.
[0045] (1) In the above-described embodiment, the planar shape of the piezoelectric element 11 was a long rectangle along the X direction, but the planar shape of the piezoelectric element 11 can be arbitrarily changed. For example, the planar shape of the piezoelectric element 11 may be a circle, a polygon, etc. However, the configuration in which the planar shape of the piezoelectric element 11 is a long rectangle along the X direction has the effect of making it easier to obtain biological information from multiple locations along a single blood vessel compared to the case in which the planar shape of the piezoelectric element 11 is other planar shapes.
[0046] (2) In the above-described embodiment, the multiple first electrodes 15 are arranged at equal intervals, but the intervals at which the multiple first electrodes 15 are arranged are not limited to equal intervals. For example, configurations in which the intervals between the multiple first electrodes 15 become narrower toward the positive side in the X direction, or configurations in which the intervals between the multiple first electrodes 15 become wider toward the positive side in the X direction, are conceivable.
[0047] (3) In the above embodiment, the widths of the multiple wires 22 are all the same. However, the width of the longer wire among the multiple wires 22 may be made wider. Making the width of the longer wire wider than the width of the shorter wire reduces the difference in resistance in each wire. Therefore, the error in the detection voltage generated between the first electrode 15 and the second electrode 16 according to the amount of displacement of the piezoelectric element 11 can be reduced.
[0048] (4) In the above-described embodiment, the control device 2 comprises a receiving unit, an amplifier, an A / D converter, an arithmetic unit, and a display device. However, the configuration of the control device 2 may include elements not shown in the above examples, or some elements may be omitted.
[0049] (5) The notation "nth" (where n is a natural number) in this application is used solely as a formal and convenient label to distinguish each element in notation and has no substantive meaning whatsoever. Therefore, there is no room for restrictive interpretation of the position or manufacturing order of each element based on the notation "nth".
[0050] E: Addendum From the forms exemplified above, the following configuration can be understood, for example.
[0051] A biosensor according to one aspect of the present disclosure (Aspect 1) comprises a piezoelectric element including a first surface facing a living body and a second surface opposite the first surface, a plurality of first electrodes formed on the first surface at intervals from each other, and a second electrode formed on the second surface that overlaps the plurality of first electrodes in a plan view. According to the above aspect, vibrations of the living surface are transmitted to the piezoelectric element via each first electrode. Since a voltage is generated at each first electrode in response to the deformation of the piezoelectric element, the displacement generated at a location on the living surface corresponding to each first electrode can be detected by detecting the voltage at each first electrode. That is, displacement can be detected at multiple different locations on the living surface. Furthermore, the piezoelectric element and the second electrode are continuous across a plurality of first electrodes. That is, the piezoelectric element and the second electrode are shared by a plurality of first electrodes. Therefore, the configuration is simplified and miniaturized compared to a configuration in which the piezoelectric element and the second electrode are individually installed for each first electrode.
[0052] In the specific example of Embodiment 1 (Embodiment 2), the biosensor has a second electrode that is elongated in the first direction, and each of the plurality of first electrodes has a planar shape that is elongated in a second direction intersecting the first direction, and the plurality of first electrodes are arranged in the first direction. In the above embodiment, the second electrode is elongated in the first direction, and the plurality of first electrodes that are elongated in the second direction are arranged along the first direction. That is, the biosensor contacts the living body over a range that is elongated in the first direction. Therefore, compared to a configuration in which, for example, first electrodes that are elongated in the second direction are arranged in the second direction, it is possible to detect displacement over a wide range of both the first and second directions on the living body surface.
[0053] The biosensor in Embodiment 1 or a specific example of Embodiment 2 (Embodiment 3) further comprises an insulating sheet covering the plurality of first electrodes. In the above embodiments, the plurality of first electrodes are protected by being covered with the insulating sheet. Therefore, damage to the first electrodes due to contact or collision with living organisms or other elements can be prevented. In addition, the first electrodes are electrically insulated from living organisms. Therefore, it is possible to prevent current from flowing from the first electrode through the living organism to adjacent first electrodes. Note that covering the first electrodes means that the first electrodes and the insulating sheet overlap in a plan view. Specifically, it is sufficient to have an insulating sheet between the first electrodes and the living organism surface.
[0054] In the biosensor in any specific example (Aspect 4) of Embodiments 1 to 3, a slit is formed between each of the plurality of adjacent first electrodes of the piezoelectric element. In the above embodiment, a slit is formed between each of the plurality of adjacent first electrodes. In the above configuration, vibrations of the first electrode due to vibrations of the living body are less likely to propagate to other adjacent first electrodes. Therefore, the detection accuracy of the biosensor can be improved compared to a configuration in which no slits are formed between each of the plurality of adjacent first electrodes.
[0055] A biosensor in any specific example (5th embodiment) of embodiments 1 to 4 further comprises a wiring substrate including a flexible substrate and a plurality of wirings formed on the surface of the substrate, wherein the plurality of wirings include a plurality of first wirings connected to the plurality of first electrodes and a plurality of second wirings connected to the second electrodes.
[0056] In any specific example (6th embodiment) of embodiments 1 to 5, the biosensor includes a plurality of second wirings, one connected to one end of the second electrode and the other connected to the other end of the second electrode. In the embodiments described above, the second wirings are installed at both ends of the second electrode. In a configuration where the wiring is connected to only one end of the second electrode, a difference in the voltage of the second electrode occurs depending on the position in the first direction. With a configuration in which the second wiring is connected to both ends of the second electrode, the voltage is made uniform across the entire second electrode in the first direction. The difference in voltage between the first electrode and the second electrode due to the voltage distribution at the second electrode is suppressed. Therefore, the error in the voltage detected from each first electrode can be reduced, and the detection accuracy of the biosensor can be improved.
[0057] In a specific example (7th embodiment) of any of embodiments 1 to 6, each of the plurality of first wirings includes a first terminal connected to the first electrode and a second terminal on the opposite side of the first terminal, the first terminals of the plurality of first wirings are arranged over a first range along a predetermined direction, and the second terminals of the plurality of first wirings are arranged over a second range along the predetermined direction, the second range being narrower than the first range. In the above embodiment, the second range in which the plurality of second terminals are arranged is narrower than the first range in which the plurality of first terminals are arranged. That is, the plurality of second terminals are more concentrated than the plurality of first terminals. With the above configuration, the biosensor can be made smaller compared to the case where the first range and the second range are the same, or where the first range is wider than the second range.
[0058] A method for manufacturing a biosensor according to one aspect of this disclosure (Aspect 8) includes the steps of forming a plurality of first electrodes spaced apart from each other on a first surface of a piezoelectric element facing a living body, and forming a second electrode on a second surface opposite the first surface, which overlaps the plurality of first electrodes in a plan view. According to this aspect, vibrations of the living surface are transmitted to the piezoelectric element via each first electrode. Since a voltage is generated at each first electrode in response to the deformation of the piezoelectric element, the displacement generated at a location on the living surface corresponding to each first electrode can be detected by detecting the voltage at each first electrode. In other words, displacement can be detected at multiple different locations on the living surface. Furthermore, the piezoelectric element and the second electrode are continuous across a plurality of first electrodes. That is, the piezoelectric element and the second electrode are shared by a plurality of first electrodes. Therefore, the configuration is simplified and miniaturized compared to a configuration in which the piezoelectric element and the second electrode are individually installed for each first electrode. [Explanation of Symbols]
[0059] 1...Biosensor, 2...Control device, 3...Skin, 4...Artery, 10...Detection substrate, 11...Piezoelectric element, 12...First surface, 13...Second surface, 14...Slit, 15...First electrode, 16...Second electrode, 17...Protruding part, 18...Insulating sheet, 19...Detection part, 20...Wiring board, 21...Base material, 22...Multiple wirings, 23...First wiring, 24...First terminal, 25...Second terminal, 26...Second wiring, 27...ACF, 28...Conductive particles, 100...Biometric measurement system, Tp...Time difference of pulse peak at a different location, P1...Lamination process of the first electrode, P2...Lamination process of the second electrode, W1...First range, W2...Second range.
Claims
1. A piezoelectric element comprising a first surface facing a living organism and a second surface opposite the first surface, A plurality of first electrodes formed on the first surface at intervals from each other, The second surface is formed and the second electrode overlaps the plurality of first electrodes in a plan view. A biosensor equipped with the following features.
2. The second electrode has a planar shape that is elongated in the first direction, Each of the plurality of first electrodes has a planar shape that is elongated in a second direction intersecting the first direction, The plurality of first electrodes are arranged in the first direction. The biosensor according to claim 1.
3. Insulating sheet covering the plurality of first electrodes The biosensor according to claim 1 or claim 2, further comprising:
4. In the piezoelectric element, a slit is formed between each of the multiple first electrodes that are adjacent to each other. The biosensor according to claim 1 or claim 2.
5. A flexible base material, Multiple wirings formed on the surface of the substrate and Further comprising a wiring board including, The aforementioned multiple wires are, A plurality of first wires connected to each of the plurality of first electrodes, A plurality of second wires connected to the second electrode and A biosensor according to claim 1, including the following:
6. The aforementioned plurality of second wirings are A second wiring connected to one end of the second electrode, The second wiring connected to the other end of the second electrode and The biosensor according to claim 5, including the above.
7. Each of the plurality of first wirings is A first terminal connected to the first electrode, Including a second terminal on the opposite side of the first terminal, The first terminals in the plurality of first wirings are arranged over a first range along a predetermined direction, The second terminals in the plurality of first wirings are arranged over a second range along the predetermined direction, The second range is narrower than the first range. The biosensor according to claim 5 or claim 6.
8. The process involves forming multiple first electrodes on the first surface of a piezoelectric element that faces the living body, spaced apart from each other. The process includes the step of forming a second electrode on the second surface opposite to the first surface, which overlaps the plurality of first electrodes in a plan view. A method for manufacturing a biosensor.