WO2021200245A1

WO2021200245A1 - Biosensor

Info

Publication number: WO2021200245A1
Application number: PCT/JP2021/011268
Authority: WO
Inventors: ダニエルポポビッチ
Original assignee: 日東電工株式会社
Priority date: 2020-03-30
Filing date: 2021-03-18
Publication date: 2021-10-07
Also published as: JPWO2021200245A1

Abstract

Provided is a biosensor that is air-permeable, has a noise suppression effect, and can stably detect biological signals. This biosensor has an electrode assembly that detects biological information from a skin surface. In the electrode assembly, an electrode, a hydrophilic substrate, and a rigid cover are positioned in this order from a surface of contact with the skin, and a space is provided between the hydrophilic substrate and the rigid cover.

Description

Biosensor

The present invention relates to a biosensor.

When a dry electrode is used for a sensor that detects biological signals such as electrocardiography (ECG) waveforms, pulse waves, electroencephalograms, and myoelectric signals, the electrodes are exposed on the surface of the sensor and the electrodes are brought into direct contact with the skin. Measure the bioelectric potential. At this time, it is desirable that the electrodes and the skin are in stable contact. It is known that an electrode is placed on the surface of a biocompatible polymer substrate and attached to the skin to detect data (see, for example, Patent Document 1).

When measuring by directly contacting the electrodes of the biosensor with the skin, the electrodes may expand or contract, distort, etc. due to the influence of body movement depending on the mounting position. When the electrode expands or contracts, is distorted, or the like, it easily peels off from the skin and the contact impedance increases. The contact state between the electrodes and the skin is also exacerbated by sweat and water contained in secretions, which contributes to noise. When the biosensor is worn for a long period of time, sweat or the like may accumulate between the electrodes and the skin, causing itching of the skin. It is desirable that the biosensor has both breathability and noise suppression effect.

An object of the present invention is to provide a biological sensor that has air permeability and noise suppression effect and can stably detect biological signals.

In one aspect of the invention, the biosensor has an electrode assembly that detects biometric information from the surface of the skin.
In the electrode assembly, the electrodes, the hydrophilic base material, and the rigid cover are arranged in this order from the contact surface with the skin.
A space is provided between the hydrophilic substrate and the rigid cover.

With the above configuration, breathability and noise suppression effect can be realized, and biological signals can be detected stably.

It is a top view of the biosensor of the embodiment. It is a bottom view of the biosensor of the embodiment. It is a schematic diagram of the sensor unit of a biological sensor. This is a modified example of the sensor unit. It is a process drawing of the assembly process of the electronic component used in a biosensor. It is a schematic view of an electrode assembly, (A) is a top view, and (B) is a cross-sectional view taken along the line AA'. It is sectional drawing of the state which covered the electrode assembly with a top cover and a casing. FIG. 5 is a cross-sectional view of another configuration in which the electrode assembly is covered with a top cover and a casing. It is a figure which shows the design example of an electrode. It is an evaluation result of the measurement using the electrode configuration of FIG. It is a schematic diagram of the system which evaluates a rigid cover. It is a bottom view and a top view of the evaluation system of FIG. The ECG waveform and its FFT when the non-stretchable film is not arranged. The ECG waveform and its FFT when a one-piece non-stretchable film covering a pair of electrodes is provided. The ECG waveform and its FFT when a separate type non-stretchable film that individually covers each of the pair of electrodes is provided. The ECG waveform and its FFT when a non-stretchable film having an opening having the same size as the electrode is provided. The ECG waveform and its FFT when a non-stretchable film having an opening larger than that of the electrode is provided. It is a figure which compares the ECG waveform when the non-stretchable support layer is used for the electrode sample, and when the stretchable support layer is used.

The inventor suppresses the distortion and expansion and contraction of the electrodes due to body movements, etc., and improves the air permeability around the electrodes that come into contact with the skin, thereby reducing the noise of the biosensor and enabling stable signal measurement. I found that it would be. Improving breathability also leads to improved fit and extended continuous use. The specific configuration of the biosensor will be described below.

<Structure of biosensor>
FIG. 1 is a top view of the biosensor 1 of the embodiment. The surface on which the biosensor 1 is mounted, that is, the surface in contact with the skin is defined as the XY plane, and the direction orthogonal to the XY plane is defined as the Z direction. For convenience, the upper surface side of the biosensor 1 in the + Z direction is referred to as “upper side”, and the −Z direction is referred to as “lower side”. In the top view, the shape of the casing 120 that houses the entire casing 120 is drawn with a solid line, and the substantial sensor unit housed inside the casing 120 is drawn with a broken line.

In the configuration example of FIG. 1, the main part of the biosensor 1 is housed inside the casing 120, but the casing 120 is not essential and can be omitted. When the casing 120 is used, a ventilation hole 125 is provided at the end of the casing 120. Even if the biosensor 1 is attached for a long time with the casing attached, sweat, moisture, heat, and the like can be released from the ventilation holes 125 to the outside.

The biosensor 1 has an electronic component 150 and a pair of electrode assemblies 30 that are electrically connected to the electronic component 150. The surface on which the electrode assembly 30 is placed becomes the contact surface with the skin.

In the electrode assembly 30, as will be described later, the electrode 10, the hydrophilic base material 25, and the rigid cover 31 covering the electrode 10 and its peripheral region are arranged in this order from the contact surface with the skin. There is. A space or air layer is provided between the hydrophilic base material 25 and the rigid cover 31. Due to this laminated structure of the electrode assembly 30, air permeability is ensured, expansion and contraction and distortion of the electrode 10 are suppressed, and low noise characteristics are realized. Details of the electrode assembly 30 will be described with reference to FIGS. 5 and later.

In FIG. 1, a pair of electrode assemblies 30 are used to acquire biometric information in a single channel, but the configuration is not limited to this. Two differential electrode assemblies 30 and one ground electrode assembly may be used, or two or more pairs of electrode assemblies 30 may be used to acquire biometric information in multiple channels. A wearable sensor is realized by bringing the electrode assembly 30 into contact with the skin and attaching the biosensor 1 to the living body.

The casing 120, which is shown in three

regions

101, 102, and 103 for convenience, corresponds to the arrangement position of the electrode assembly 30 and the electronic component 150, but can be integrally molded.

Regions

101 and 103, respectively, in which the pair of electrode assemblies 30 are arranged, are provided on both sides of the region 102 accommodating the electronic component 150.

The ventilation holes 125 at both ends of the casing 120 are provided outside the position where the electrodes 10 are arranged. As described above, by providing the ventilation holes 125, it is possible to release the moisture radiated from the skin such as sweat and secretion, and reduce the influence of the moisture on the electrode assembly 30.

The electrode assembly 30 is connected to the electronic component 150 by wiring 160. The electrode assembly 30 functions as a probe and comes into contact with the skin during measurement to detect a biological signal. The biological signal detected by the electrode assembly 30 is processed and stored by the electronic component 150.

A notch 106 may be formed at the boundary between at least one of the

regions

101 and 103 and the central region 102. By providing the notch 106, the casing 120 is easily bent in the major axis direction (X direction). The biosensor 1 as a whole has improved followability to the surface shape of the living body, and can suppress peeling of the electrode assembly 30 from the skin surface.

FIG. 2 is a bottom view of the biological sensor 1. The electrode 10 is exposed on the bottom surface (attachment surface) which is the contact surface with the skin. Although omitted in FIG. 2, an adhesive layer may be provided on the bottom surface of the biosensor 1 in a region other than the electrode 10. By providing the adhesive layer, the sensor unit including the electrode 10 can be fixed to the skin.

FIG. 3A is a schematic view of the sensor unit 100 used in the biological sensor 1 as viewed from the bottom surface side, that is, from the −Z direction. The sensor unit 100 is the main part of the biosensor 1 and includes an electronic component 150 and a pair of electrode assemblies 30 that are electrically connected to the electronic component 150.

The entire electronic component 150 is protected by a waterproof film 141. As will be described later, it is desirable that the electronic component 150 includes an integrated circuit (IC) chip, a battery, and the like, and has moisture resistance from the viewpoint of operational reliability.

The waterproof film 141 is made of a non-woven fabric having hydrophobicity and adhesiveness, a hydrophobic resin, or the like. In order to enhance the water repellency, the surface of the waterproof film 141 may be water repellent. As a water repellent treatment, the surface of the non-woven fabric or hydrophobic resin may be coated with a thin silicone resin, polystyrene resin, acrylic resin, or other suitable material.

In the electrode assembly 30, when viewed from the −Z direction, the electrode 10, the hydrophilic base material 25, and the rigid cover 31 are arranged in this order, and the electrode 10 is exposed on the back surface side. The electrode 10 is connected to the electronic component 150 by the wiring 160 and the connecting portion 161. The back surface of the electrode assembly 30 including the electrode 10 is a contact surface Pcont with a living body. The biological signal detected by the electrode 10 is processed by the electronic component 150 and recorded over a certain period of time.

The electrode 10 is made of, for example, a polymer material. The polymer material is superior in flexibility, oxidation resistance, etc. as compared with the metal material, and is suitable for direct contact with the skin. The electrode 10 may be formed of a conductive composition containing a conductive polymer and a binder resin. As the conductive polymer, polythiophene, polyacetylene, polypyrrole, polyaniline, polyphenylene vinylene, one of these, or a combination of two or more thereof can be used. As an example, polythiophene compounds, especially polystyrene sulfonic acid (poly4-styrene sulfonate; PEDOT-PSS doped with PSS) is used. As another example, the electrode 10 may be formed of a mixture of a polymer and a conductive filler such as carbon nanoparticles, carbon nanotubes, carbon nanobuds, and silver nanowires.

The binder resin may be a water-soluble polymer or a water-insoluble polymer, but in the embodiment, the water-soluble polymer is used from the viewpoint of compatibility with other components contained in the conductive composition. The water-soluble polymer contains a polymer (hydrophilic polymer) that is completely insoluble in water and has hydrophilicity. As the water-soluble polymer, a hydroxyl group-containing polymer or the like can be used. As the hydroxyl group-containing polymer, saccharides such as agarose, polyvinyl alcohol (PVA), modified polyvinyl alcohol, or a copolymer of acrylic acid and sodium acrylate can be used. These may be used alone or in combination of two or more. Among these, polyvinyl alcohol or modified polyvinyl alcohol is preferable, and modified polyvinyl alcohol is more preferable.

One or more holes 15 are formed in the electrode 10. When the biosensor 1 is attached to the skin of the subject, the hydrophilic base material 25 comes into contact with the skin through the holes 15. The hydrophilic base material 25 is a hydrophilic and adhesive tape base material, which is pressed against the skin through the holes 15 to hold the electrode 10 in a predetermined position on the skin. The diameter of the hole 15 is preferably 2 mm or more and 8 mm or less, more preferably 3 mm or more and 8 mm or less, and further preferably 5 mm or more and 8 mm or less from the viewpoint of air permeability and adhesiveness. The shape of the hole 15 provided in the electrode 10 is not limited to a circle, and may be a hole such as an ellipse, an oval, a rectangle, a triangle, or a polygon.

When the diameter of the hole 15 is within the above range, the hydrophilic base material 25 adheres to the skin through the hole 15 and can maintain the contact between the electrode 10 and the skin while ensuring breathability. When the biosensor 1 is used during sweating or for a long period of time (for example, one week), the diameter of the hole 15 is preferably 5 mm or more and 8 mm or less.

In order to acquire a biological signal with low noise, it is desirable that a certain distance is maintained between the hole 15 and the edge of the electrode 10. By providing the electrode 10 with a conductive path having a certain width or more, the reliability of biological signal acquisition is improved. As long as the width of the conductive path can be made sufficiently wide, two holes having a diameter of 5 to 6 mm may be arranged in one electrode 10.

The shape of the electrode 10 is not particularly limited as long as it can be held on the skin surface of the wearer and can detect a biological signal, but it is preferably a shape that follows the contour of the hydrophilic base material 25. This is because the signal-to-noise ratio can be improved by increasing the contact area with the living body. An example of the shape of the electrode 10 will be described later with reference to FIG. As the hydrophilic base material 25, for example, kinesiology tape manufactured by Nitto Denko KK can be used. Kinesiology tape uses an acrylic adhesive that is less irritating to the skin and has hydrophilicity. At the time of use, the skin does not become tight and adheres to the skin, and can absorb moisture such as sweat. No adhesive remains on the skin after use.

A rigid cover 31 is arranged on the surface of the hydrophilic base material 25 opposite to the electrode 10. Although the rigid cover 31 is flexible, it is more rigid than the electrode 10 and the hydrophilic base material 25. By surrounding the region corresponding to the electrode 10 with the rigid cover 31, expansion and contraction and distortion of the electrode 10 due to body movement and the like are suppressed, and the contact property between the electrode 10 and the skin is maintained.

As will be described later, the rigid cover 31 may be provided with a through hole. The through hole functions as a ventilation hole, and the ventilation of the electrode assembly 30 is improved.

The entire sensor unit 100 including the electronic component 150 and the electrode assembly 30 is extremely flexible and has high followability to the skin. When the sensor unit 100 is housed inside the casing 120, the biosensor 1 may be fixed to the skin by providing an adhesive layer in a region other than the electrode 10 on the back surface of the biosensor 1.

FIG. 3B shows a modified example of the sensor unit. The sensor unit 100A has a configuration in which top covers 40a, 40b, and 40c are provided on the sensor unit 100 of FIG. 3A. FIG. 3B is a view seen from the back surface side of the sensor unit 100A, that is, from the −Z direction, and the electrode 10 is located on the outermost surface.

The top covers 40a to 40c are breathable and hydrophilic adhesive covers. The electronic component 150 protected by the waterproof film 141 is covered with the top cover 40b. The pair of electrode assemblies 30 are covered with

top covers

40a and 40b, respectively.

The top cover 40b is larger than the size of the electronic component 150. The top covers 40a and 40b are larger than the electrode assembly 30. During use, the top covers 40a, 40b, 40c secure the sensor unit 100A to the skin. The top covers 40a to 40c are desired to be mild in addition to being breathable and hydrophilic. As an example, an acrylic tape such as "Kino white" manufactured by Nitto Denko KK can be used.

By using the individual

top covers

40a, 40b, and 40c for the electrode assembly 30 and the electronic component 150, the sensor unit 100A can be fixed to the skin of the person to be measured while maintaining high flexibility. When the top covers 40a to 40c are provided, the casing 120 itself may not be used.

FIG. 4 shows an assembly process of the electronic component 150 used in the biosensor 1. An electrical insulating layer 142 is arranged in a predetermined area of the waterproof film 141. The insulating layer 142 is provided at a position where the IC chip is arranged, and is formed of, for example, an insulating resin such as an epoxy resin.

The IC chip 145 is placed on the insulating layer 142. A wiring 160 having a connection portion 161 extends from the IC chip 145. The battery 180 is arranged at a predetermined position on the waterproof film 141. The battery 180 is electrically connected to the IC chip 145 to supply power to the IC chip 145.

After arranging the IC chip 145 and the battery 180, fold the waterproof film 141 in half and attach it. The wiring 160 is pulled out of the bonded waterproof film 141. The electrode 10 of the electrode assembly 30 is connected to the connection portion 161 at the tip of the wiring 160.

FIG. 5 is a schematic view of the electrode assembly 30. 5A is a top view and FIG. 5B is a cross-sectional view taken along the line AA'of FIG. 5A. In the electrode assembly 30, the electrode 10, the hydrophilic base material 25, and the rigid cover 31 are arranged in this order from the side of the contact surface Pcont with the skin.

The base material 25 covers the electrode 10 and its surroundings. By covering the periphery of the electrode 10 with the hydrophilic base material 25, moisture such as sweat can be released to the outside while the biosensor 1 is attached.

A cover 31 having a higher rigidity than the base material 25 and the electrode 10 is arranged so as to cover the base material 25. A space (or air layer) 33 is formed between the base material 25 and the rigid cover 31. The space 33 contributes to air permeability and can serve as a cushioning material for external impact. It is possible to prevent noise from being mixed into the biological signal due to rubbing of the clothes of the user wearing the biological sensor 1 or contact with a hand or the like.

By arranging the rigid cover 31 so as to cover the periphery of the electrode 10, expansion and contraction and distortion of the electrode 10 due to body movement and the like are suppressed. Even if the wearer's skin expands and contracts significantly when the biosensor 1 is attached in daily life, the expansion and contraction of the electrode 10 is suppressed by the rigid cover 31. The increase in contact impedance due to the elongation and displacement of the electrode 10 is suppressed, and a good biological signal waveform is obtained.

In FIG. 5, a rectangular rigid cover 31 is used, but the present invention is not limited to this example. When the rigid cover 31 is shaped along the contour of the electrode 10, the expansion / contraction / distortion of the electrode 10 can be suppressed more effectively.

FIG. 6A is a cross-sectional view of the electrode assembly 30 covered with the top cover 40 and the casing 120. As shown in FIG. 3B, when the top cover 40 is provided on the sensor unit 100A, the electrode assembly 30 is covered with the top cover 40 when the biosensor 1 is used. The top cover 40 is a flexible adhesive film having breathability and hydrophilicity. The top cover 40 brings the entire electrode assembly 30 into close contact with the skin.

Although the casing 120 is not essential, the entire sensor unit 100A can be protected when the biosensor 1 is used for a long period of time. The casing 120 may be made of a soft resin such as silicone rubber or urethane. Since the ventilation holes 125 are provided at both ends of the casing 120, water, sweat, secretions and the like absorbed by the hydrophilic base material 25 can be released to the outside of the biosensor 1.

FIG. 6B shows another configuration example covered with the electrode assembly 30, the top cover 40, and the casing 120. In FIG. 6B, the rigid cover 31 is provided with a through hole 32. The through hole 32 can release moisture, moisture, heat, etc. such as sweat trapped in the space 33. In this case, it is desirable to cover the through hole 32 with a porous membrane 35 that prevents water from entering from the outside and allows air to pass through. As the porous membrane 35, for example, "TEMISH" (registered trademark of Nitto Denko KK) can be used. When the through hole 32 is provided in the rigid cover 31, a through hole may be provided in at least one of the top cover 40 and the casing 120 at a position corresponding to the through hole 32 or in the vicinity thereof. In FIG. 6B, the through hole 42 is formed in the top cover 40, and the through hole 126 is formed in the casing 120 separately from the ventilation hole 125, but the through

hole

42 and 126 are not essential. At least a part of the through hole 32, the through hole 42, and the ventilation hole 125 may overlap in the stacking direction. As a result, the air permeability can be ensured when the biosensor 1 is used.

<Electrode design example>
FIG. 7 shows a design example of the electrode 10. The electrode 10 is formed of a conductive layer 11 having good conductivity, and is designed in a shape that maintains good contact with the skin. A hole 15 is formed in the conductive layer 11 in order to prevent the electrode 10 from peeling off from the skin surface.

When the electrode assembly 30 is pressed against the skin when the biosensor 1 is used, the hydrophilic base material 25 exposed in the hole 15 is pressed against the skin, and the electrode 10 is adhered and held to the skin. In order to stabilize the contact between the skin and the electrode 10, the holes 15 have a certain size and are arranged so as not to obstruct the conductive path for signal detection formed in the conductive layer 11.

In order to secure the contact area between the skin and the electrode 10, the total area of the electrode 10 is 80 mm ² or more, more preferably 100 mm ² or more. The diameter of the hole 15 is in the range of 2 mm to 8 mm, more preferably 3 mm to 8 mm, still more preferably 5 mm to 8 mm in order to achieve both breathability and adhesiveness.

In (A) of FIG. 7, two holes 15 are formed along the short side in the rectangular electrode 10. The minimum width Pmin of the conductive path formed in the conductive layer 11 is the distance between the edge of the electrode 10 and the holes 15, or the distance between the two holes 15. Two holes 15 may be arranged along the long side of the electrode 10 in order to keep Pmin wide. Since the electrode 10 can be adhered to the skin through the two holes 15, the diameter of the holes 15 may be about 2 to 6 mm.

In FIG. 7B, one hole 15 is formed in the U-shaped electrode 10. The contour of the electrode 10 may be curved in an arc shape along the contours of both ends of the biosensor 1. The minimum width Pmin of the conductive path formed in the conductive layer 11 is the distance between the edge of the electrode 10 and the hole 15.

In (C) of FIG. 7, an oval hole 15 is formed in the rectangular electrode 10 along the short side. The minimum width Pmin of the conductive path formed in the conductive layer 11 is the distance between the edge of the electrode 10 and the hole 15. Instead of an oval, an elliptical hole 15 may be formed.

(D) and (E) of FIG. 7 are modified examples of the U-shaped electrode of (B), and the shape of the base portion on the opposite side to the curved portion is changed. The straight portion of the base is an area that receives the connection portion 161 of the wiring 160. The shape of the base can be designed to an appropriate shape as long as the electrical connection between the wiring 160 and the electrode 10 is established.

FIG. 8 is an evaluation result using the electrode 10 of FIG. 7A. The size of the electrode 10 is made constant (280 mm ² ), and a plurality of samples having different diameters and arrangements of the holes 15 are easily measured to measure biological signals. In each sample, a rigid cover 31 was provided on the surface of the base material opposite to the electrode 10, and a pair of electrode samples were adhered to the skin for measurement.

The leftmost column is the pore diameter (mm), the second column from the left is the minimum width Pmin (mm) of the conductive path, and the rightmost column is the evaluation result. The evaluation result shows the monitor result after 1 day and the monitor result after 7 days, and includes the monitor result at the time of normal and the monitor result at the time of sweating, respectively. The double circle indicates that a good biological signal waveform was obtained and the contact between the skin and the electrode 10 was not impaired. The triangular marks indicate that the signal was somewhat noisy due to some loss of contact between the skin and the electrode 10, but a relatively stable biological signal waveform was obtained. The cross mark indicates that the biological signal waveform is deteriorated by noise.

In the arrangement in which the diameter of the holes 15 is set to 2 mm and the minimum width Pmin of the conductive path is set to 2 mm, five holes 15 (one in the center and four around the holes) are formed in the electrode 10. A stable signal waveform can be obtained if the measurement is performed for one day under normal conditions. The signal waveform deteriorates in a sweaty state or in the measurement after 7 days.

Among the cross-mark evaluations, those with one asterisk peeled off at the interface between the electrode assembly 30 and the skin 30 minutes after intense sweating, making it impossible to measure. Those with two asterisks indicate that moisture is accumulated at the interface between the electrode 10 and the skin, and the contact between the pressure-sensitive adhesive and the skin is gradually impaired.

In the arrangement in which the diameter of the holes 15 is set to 3 mm and the minimum width Pmin of the conductive path is set to 3 mm, four holes 15 are formed in the electrode 10 in a 2 × 2 arrangement. Under normal conditions, a relatively stable biological signal waveform can be obtained even after 7 days have passed. After strong sweating after 7 days, noise is mixed in the biological signal waveform and the waveform deteriorates.

When the diameter of the hole is 5 mm or more, a good biological signal waveform can be obtained regardless of the monitoring conditions. The diameters of the holes are 5 mm and 6 mm, and the numerical values outside the parentheses indicate the minimum width Pmin of the conductive path when two holes 15 are arranged, and the numerical values in the parentheses indicate that one hole 15 is arranged in the center of the electrode 10. The minimum width of the conductive path at the time is Pmin. When the diameter of the hole 15 is 8 mm, one hole 15 is arranged in the center of the electrode 10 to secure a minimum width Pmin of a conductive path of 3 mm.

From this measurement result, the electrode 10 is configured to cover the hydrophilic base material 25, and the diameter of the hole 15 formed in the electrode 10 is 2 mm to 8 mm for daily use. When the biosensor 1 is continuously worn for one week, the diameter of the hole 15 is 3 mm to 8 mm, more preferably 5 mm to 8 mm. In the case of an oval or ellipse, the diameter is the average of the minor and major diameters.

<Evaluation of rigid cover>
9 is a schematic view of the evaluation system 20S of the rigidity cover 31, and FIG. 10 is a bottom view (A) and a top view (B) of the evaluation system of FIG. The electrode 10 is held by the hydrophilic base material 25, and the non-stretchable film 60 is arranged on the surface of the base material 25 opposite to the electrode 10. The non-stretchable film 60 simulates a rigid cover 31. Although the non-stretchable film 60 is flexible, it is more rigid than the base material 25 and the electrode 10 and is not easily deformed.

A part of the lower surface of the electrode 10 is covered with the insulating layer 22, and the size of the electrode 10 is fixed to 14 mm × 20 mm. Two holes having a diameter of 5 mm are arranged in the electrode 10 along the direction of the long side (length L). The electrode 10S is made of PEDOT-PSS and is connected to the ECG monitor by a conductive hook 21.

The ECG waveform is measured by changing the arrangement area of the non-stretchable film 60. In FIG. 10B, the opening 65 formed in the non-stretchable film 60 is for changing the exposed state of the electrode 10, and the space 33 is simulated by the opening 65. Two types of openings 65 are formed: an opening having the same size as the electrode 10 (indicated by a chain line in the figure) and an opening larger than the electrode 10.

FIGS. 11A to 11E are measurement results using the non-stretchable film 60. Through FIGS. 11A to 11E, (a) is an ECG waveform and (b) is a Fast Fourier Transform (FFT) spectrum thereof. The horizontal axis of the ECG waveform is time [seconds], and the vertical axis is potential [V]. The horizontal axis of the FFT spectrum is frequency [Hz], and the vertical axis is magnitude. Since it is difficult to evaluate the hidden noise generated at the same frequency as the peak only with the ECG waveform, the state of the noise is observed in the FFT spectrum.

FIG. 11A is a measurement result when the non-stretchable film 60 is not covered. Since the non-stretchable film 60 is not used, the entire upper surface of the base material 25 is open to the air layer, and there is no physical restraint on the base material 25 and the electrodes 10.

Looking at the ECG waveform, the baseline, which is the line connecting the start point of the waveform to the start point of the next waveform, is stable. In the FFT spectrum, the signal-to-noise ratio (SNR) to noise up to 0.5 Hz is 6.6. This value is used as the evaluation standard.

FIG. 11B is a measurement result when a pair of electrodes is covered with a one-piece non-stretchable film 60. In this model, the surface region of the base material 25 corresponding to the pair of electrodes 10 is covered with the non-stretchable film 60, but no space or air layer is provided between the base material 25 and the non-stretchable film 60. ..

Looking at the ECG waveform, the baseline fluctuates greatly, and the vertical position of the waveform also fluctuates. The SNR of the FFT spectrum is as low as 3.0. It is considered that as a result of the electrode 10 being completely restrained by the non-stretchable film 60, external vibration or the like is directly transmitted to the electrode 10 to increase noise.

FIG. 11C is a measurement result when each of the pair of electrodes is individually covered with the two-piece non-stretchable film 60. In this model, the surface area of the substrate 25 corresponding to each electrode 10 is covered with the non-stretchable film 60.

Looking at the ECG waveform, the baseline fluctuates even more than in FIG. 10B, and the vertical position of the waveform also fluctuates. The SNR of the FFT spectrum is even lower at 2.3. It is considered that as a result of covering the region of the base material 25 corresponding to each electrode 10 with the non-stretchable film 60, the vibration transmitted from the individual non-stretchable film 60 to the corresponding electrode 10 increased.

FIG. 11D is a measurement result when the non-stretchable film 60 with an opening 65 covers the periphery of the electrode 10. The opening 65 is formed to have the same size as the electrode 10. The expansion and contraction or strain of the electrode 10 is constrained by the non-stretchable film 60 surrounding the periphery, and the base material 25 in the region corresponding to the electrode 10 is released by the opening 65.

Looking at the ECG waveform, the baseline is constant and a uniform ECG waveform is obtained. The SNR of the FFT spectrum is as high as 10.0. It is considered that the expansion and contraction of the electrode 10 is suppressed by the non-stretchable film 60 surrounding the periphery, while the transmission of vibration from the outside is relaxed by the air layer.

FIG. 11E is a measurement result when the non-stretchable film 60 with an opening 65 covers the periphery of the electrode 10. The opening 65 is formed to have a size larger than that of the electrode 10. Specifically, openings 65 are formed on both sides of the electrode 10 in the W direction of FIG. 10 by expanding the space by 3 mm. The size of the opening 65 in the L direction is the same as the length of the long side of the electrode 10. The expansion and contraction or strain of the electrode 10 is constrained by the non-stretchable film 60 surrounding the electrode 10. Even if the opening 65 is slightly wider in the W direction, the deformation of the electrode 10 is sufficiently restrained. The surface region of the base material 25 corresponding to the electrode 10 is opened by the opening 65.

Looking at the ECG waveform, the slope of the baseline is constant, and a uniform ECG waveform is obtained. The SNR of the FFT spectrum is as high as 7.5. It is considered that the non-stretchable film 60 suppresses the expansion and contraction of the electrode 10 (particularly the expansion and contraction in the L direction), while the air layer relaxes the transmission of vibration from the outside.

From the results of FIGS. 11A to 11E, the non-stretchable or rigid cover 31 restrains the expansion or contraction or deformation of the electrode 10, and the space 33 or the air layer is provided between the base material 25 and the rigid cover 31. , A good biological signal waveform with suppressed noise can be obtained. The space 33 also serves to release the moisture absorbed by the hydrophilic base material 25, and the air permeability of the electrode assembly 30 is improved. By providing the through hole 32 in the rigid cover 31 and communicating the space 33 with the outside, the air permeability is further improved.

FIG. 12 is a diagram comparing the ECG waveforms when the non-stretchable support layer is used for the electrode sample and when the stretchable support layer is used. The size of the electrode 10 is fixed to 14 mm × 20 mm, and two holes having a diameter of 6 mm are arranged along the long axis. The ECG waveform is measured with the distance between the electrodes 10 fixed. The solid line is the ECG waveform when the non-stretchable support layer is used, and the broken line is the ECG waveform when the stretchable support layer is used.

When a non-stretchable support layer is used, the potential of the ECG waveform is in the range of less than ± 1 mV, on average, in the range of ± 500 μV over the measurement time. On the other hand, when the elastic support layer is used, it fluctuates greatly over the measurement time, and particularly fluctuates violently in the range of ± 4 mV for 5 seconds after the start of measurement.

When measuring biological signals while performing normal living activities, the elastic support layer expands and contracts or deforms together with the electrode 10, the contact impedance fluctuates, and the noise component increases. By using a non-stretchable support layer, that is, a support layer that is flexible but has a higher rigidity than the electrode 10 and the hydrophilic base material 25, the expansion and contraction of the electrode 10 is suppressed and noise is reduced. be able to.

In the biosensor 1, the electrode assembly 30 is provided with a rigid cover 31 to suppress expansion and contraction of the electrode 10 due to body movement and the like. By providing the space 33 between the rigid cover 31 and the hydrophilic base material 25, the influence of external vibration is mitigated. This makes it possible to measure biological signals with less noise.

By holding the electrode 10 with the hydrophilic base material 25, moisture such as sweat can escape even if the biosensor 1 is worn for a long period of time. When the casing 120 is used, sweat, moisture and the like can be released to the outside by the ventilation holes 125 formed in the casing 120. When the through hole 32 is provided in the rigid cover 31, the space 33 between the base material 25 and the rigid cover 31 communicates with the outside of the porous membrane, and the air permeability is further improved.

Although the present invention has been described above based on a specific configuration example, the present invention is not limited to the above-mentioned example. The rigid cover 31 can be designed into an appropriate shape according to the electrode 10 as long as it can suppress expansion and contraction and deformation of the electrode 10 and alleviate noise or vibration. If a space is formed above the electrode 10 via the hydrophilic base material 25, the edge of the rigid cover 31 and the hydrophilic base material 25 may be directly bonded to each other in the region surrounding the electrode 10. ..

As the material of the rigid cover 31, that is, the material having flexibility and non-stretchability or rigidity, a resin containing silicone rubber, styrene-butadiene rubber, natural rubber, etc. with adjusted rigidity may be used. The base material 25 may be a pressure-sensitive adhesive tape as long as it has hydrophilicity. When the electrode assembly 30 and the electronic component 150 are covered with the top covers 40a, 40b, 40c as shown in FIG. 3B, the casing 120 may be omitted. In this case, the sensor unit 100A can be used as the biosensor 1.

This application is based on patent application No. 2020-059647 filed with the Japan Patent Office on March 30, 2020, and includes the entire contents thereof.

1 Biosensor 10 Electrode 11 Conductive layer 15 Hole 25

Base material

30, 30A Electrode assembly 31 Rigid cover 32 Through hole (first through hole)
35

Porous Membrane

40, 40a, 40b, 40c Top Cover 42 Through Hole (Second Through Hole)
100, 100A Sensor Unit 106 Notch 120 Casing 125 Vent 150 Electronic Components 160 Wiring

Japanese Unexamined Patent Publication No. 2012-10978

Claims

Has an electrode assembly, which detects biological information from the surface of the skin,
In the electrode assembly, the electrodes, the hydrophilic base material, and the rigid cover are arranged in this order from the contact surface with the skin.
A space is provided between the hydrophilic substrate and the rigid cover.
Biosensor.
A casing that covers the electrode assembly on the opposite side of the contact surface.
Have more
The casing has vents.
The biosensor according to claim 1.
The rigid cover is less stretchable than the electrodes and the hydrophilic substrate.
The biosensor according to claim 1 or 2.
The biosensor according to any one of claims 1 to 3, wherein the rigid cover surrounds the electrode through the hydrophilic base material.
The rigid cover has a first through hole that communicates with the space and a porous membrane that covers the first through hole.
The biosensor according to any one of claims 1 to 4.
An adhesive and flexible top cover that covers the electrode assembly on the opposite side of the contact surface.
The biosensor according to any one of claims 1 to 5, further comprising.
An adhesive and flexible top cover that covers the electrode assembly on the opposite side of the contact surface.
Have more
The biosensor according to claim 5, wherein the top cover has a second through hole at a position corresponding to the first through hole.
The rigid cover has a first through hole that communicates with the space.
The casing has a third through hole at a position corresponding to the first through hole.
The biosensor according to claim 2.
Electronic components that are electrically connected to the electrode assembly,
The electronic component is protected by a waterproof film.
The biosensor according to any one of claims 1 to 8.
The electrode has at least one hole, in which the hydrophilic substrate is exposed.
The biosensor according to any one of claims 1 to 9.
The biosensor according to claim 10, wherein the diameter of the hole of the electrode is in the range of 3 mm to 8 mm.