CN110063724B

CN110063724B - Flexible bioelectrode and preparation method thereof

Info

Publication number: CN110063724B
Application number: CN201910343925.9A
Authority: CN
Inventors: 冯雪; 赵星蔚; 梁紫微
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2019-04-26
Filing date: 2019-04-26
Publication date: 2022-03-18
Anticipated expiration: 2039-04-26
Also published as: CN110063724A

Abstract

The invention provides a flexible bioelectrode and a preparation method thereof. The flexible bioelectrode includes: a conductive substrate; the one-dimensional conductive nano material is formed on the surface of the conductive substrate in a mode that the axial direction of the one-dimensional conductive nano material is approximately orthogonal to the surface of the conductive substrate, the diameter of the one-dimensional conductive nano material is 20-200 nm, and the length of the one-dimensional conductive nano material is 30-100 micrometers; wherein at least the contact interface area of the conductive substrate and the one-dimensional conductive nano material is provided with a polymer coating. The flexible bioelectrode of the present invention can realize effective contact with skin lines. Also, the measured noise will be significantly reduced as the fit of the device to the body improves.

Description

Flexible bioelectrode and preparation method thereof

Technical Field

The invention relates to a flexible bioelectrode and a preparation method thereof, belonging to the technical field of human body electric signal monitoring and flexible electronic devices.

Background

The skin surface of a human body has various electric signals related to physiological health conditions, including electroencephalogram, electrocardio, electrooculogram, myoelectricity and the like. The continuous real-time accurate acquisition of the electric signals has great significance for monitoring cardiovascular diseases, monitoring sports of athletes and researching the brain nervous system. Traditionally, the acquisition of these electrical signals has been based on bulky, non-deformable rigid electronics. However, because skin tissues and the like on the surface of a human body are very soft, the modulus mismatch between the traditional electronic device and the skin tissues of the human body cannot cause discomfort in long-term wearing, and because the traditional electronic device cannot be naturally attached to the surface of the human body, signal noise is easily caused by movement in the wearing process, and great influence is caused on the measurement precision.

The appearance of the flexible electronic technology breaks through the inherent rigid non-deformable morphological characteristics of the traditional electronic device, can greatly approach the mechanical characteristics of human skin tissues, can be bent like a rope, stretched like rubber, bent like paper, even deformed into any bent shape without obvious mechanical or other performance damage, and is beneficial to the change of the device adaptive to the environment or the integration with the human body biological phase, thereby improving the problems of poor fitness of the traditional electronic device and the human body in the measurement and the like. However, most of the surfaces of the flexible electrodes for collecting the human body electrical signals are smooth and flat, and the surface of the human body skin is covered with many tiny folds and ravines, and the existence of the microstructures greatly restricts the complete fit of the flexible electronic device and the surface of the human body, so that the problem of contact impedance still exists.

Citation [1] discloses an electrode plate for monitoring human body electric signals, which comprises a backing, a conductive button, an electrode chip and conductive adhesive, wherein the conductive button is fastened on one side of the backing, the electrode chip and the conductive adhesive are positioned on the other side of the backing, and the electrode chip is electrically connected with the conductive button. The electrode plate further comprises a microneedle electrode, the microneedle electrode comprises a mesh gasket and microneedles arranged on one side of the mesh gasket, and the other side of the mesh gasket is electrically connected with the electrode chip through conductive adhesive. The electrode sheet has a complicated structure, and the microneedle electrode still penetrates into the skin, possibly causing skin damage.

The cited document [2] discloses a fabric electrode and an electrocardiograph, the fabric electrode comprises a substrate and a conductive fabric, the conductive fabric is fixedly combined with the substrate, a cavity is formed between the conductive fabric and the substrate, an elastic supporting body is filled in the cavity, at least the conductive fabric in the area opposite to the substrate is a honeycomb weave structure woven fabric, the honeycomb opening of the honeycomb structure is far away from the substrate, and conductive adhesive is filled in the honeycomb. Although the fabric electrode can reduce the contact resistance between the conductive fabric and the skin, the problem of contact resistance still exists due to tiny wrinkles and ravines on the skin surface.

Cited document [1 ]: CN106551693A

Cited document [2 ]: CN106551693A

Disclosure of Invention

Problems to be solved by the invention

Aiming at the problem of contact impedance between the conventional bioelectrode and the skin, the invention aims to provide a flexible bioelectrode, which can effectively solve the problem of contact impedance between the bioelectrode and the skin, and can not penetrate into the skin and cause skin injury.

Further, another object of the present invention is to provide a method for preparing a bioelectrode, which is simple and efficient, and has easily available raw materials.

Means for solving the problems

[1] A flexible bioelectrode, comprising:

a conductive substrate;

the one-dimensional conductive nano material is formed on the surface of the conductive substrate in a mode that the axial direction of the one-dimensional conductive nano material is approximately orthogonal to the surface of the conductive substrate, the diameter of the one-dimensional conductive nano material is 20-200 nm, and the length of the one-dimensional conductive nano material is 30-100 micrometers; wherein

And at least the contact interface area of the conductive substrate and the one-dimensional conductive nano material is provided with a polymer coating.

[2] The flexible bioelectrode according to [1], wherein the conductive substrate has a polymer coating on all surfaces thereof.

[3] The flexible bioelectrode according to [1] or [2], wherein the conductive substrate comprises:

supporting the film; and

a conductive layer formed on at least one surface of the support film;

preferably, a metallic chromium layer is arranged between the support film and the conductive layer.

[4] The flexible bioelectrode according to [3], wherein the conductive layer is a metal conductive layer, and the metal conductive layer comprises one or a combination of more than two of a gold conductive layer, a silver conductive layer and a copper conductive layer; and/or

The material of the supporting film is a polymer material, and the polymer material comprises one or a combination of two of polyimide and polyethylene terephthalate.

[5] The flexible bioelectrode according to any one of [1] to [4], wherein the one-dimensional conductive nanomaterial comprises a nanowire and/or a nanotube, preferably comprises one or a combination of two or more of a silver nanowire, a gold nanowire and a carbon nanotube.

[6] The flexible bioelectrode according to any one of [1] to [5], wherein the polymer coating is derived from an organosilicon compound, preferably the organosilicon compound comprises a silicone rubber and/or a siloxane.

[7] The preparation method of the flexible bioelectrode comprises the following steps:

forming a one-dimensional conductive nano material on the surface of the conductive substrate in a manner that the axial direction of the one-dimensional conductive nano material is approximately orthogonal to the surface of the conductive substrate, wherein the diameter of the one-dimensional conductive nano material is 20-200 nm, and the length of the one-dimensional conductive nano material is 30-100 mu m;

and coating a polymer solution at least in the contact interface area of the conductive substrate and the one-dimensional conductive nano material, and curing to form a polymer coating.

[8] The production process according to [7], wherein,

and growing the one-dimensional conductive nano material on the surface of the conductive substrate in a manner that the axial direction of the one-dimensional conductive nano material is approximately orthogonal to the surface of the conductive substrate by using an anodic aluminum oxide template with a through hole and adopting an electrochemical deposition or vapor deposition method.

[9] The production method according to [8], wherein the production method comprises the steps of:

step 1, taking an anodic aluminum oxide template;

step 2, bonding the anodic aluminum oxide template with the conductive substrate by using a bonding agent;

step 3, removing the adhesive in the through hole;

step 4, growing the one-dimensional conductive nano material in the through hole by adopting an electrochemical deposition or vapor deposition method;

step 5, coating a polymer solution on at least the contact interface area of the conductive substrate and the one-dimensional conductive nano material, and forming a polymer coating after curing;

and 6, removing the anodic aluminum oxide template to obtain the flexible bioelectrode.

[10] The production method according to [9], wherein, between the step 3 and the step 4, the production method further comprises a step of growing the one-dimensional conductive nanomaterial regionally; specifically, the regional growth comprises the following steps:

step a, depositing a layer of metal substance on the surface of the anodic aluminum oxide template far away from the conductive substrate;

b, coating a layer of photoresist on the surface of the metal substance;

c, removing part of the metal substance and the photoresist on the surface of the part of the metal substance according to the arrangement mode of the flexible bioelectrode;

and d, removing the residual metal substances and the photoresist on the surfaces of the residual metal substances after the growth of the one-dimensional conductive nano material is finished.

[11] The production method according to [7] to [10], wherein the coating further comprises coating the polymer solution on all surfaces of the conductive substrate.

[12] The production method according to [7] to [11], wherein the production method of the conductive substrate comprises a step of connecting a conductive layer to a supporting film; preferably, a metal chromium layer is deposited between the conductive layer and the support film.

ADVANTAGEOUS EFFECTS OF INVENTION

The flexible bioelectrode of the present invention can realize effective contact with skin lines. And the measured noise can be obviously reduced along with the improvement of the fitting performance of the device and the human body, and the noise can not penetrate into the skin and can not cause skin damage.

The preparation method of the bioelectrode is simple and efficient, the raw materials are easy to obtain, and the bioelectrode is suitable for mass production.

Drawings

Fig. 1 shows a schematic view of the overall structure of a flexible bioelectrode according to an embodiment of the present invention.

Fig. 2 shows a process of preparing the conductive substrate in the embodiment of the present invention.

Fig. 3 is a schematic diagram illustrating a process of bonding a conductive substrate and an anodized aluminum template using a photoresist according to an embodiment of the present invention.

Fig. 4 shows a schematic process diagram of performing top surface patterning covering on the anodized aluminum template and performing area growth of silver nanowires in the embodiment of the invention.

Fig. 5 shows a schematic process diagram of polymer casting of the silver nanowire bottom and the flexible conductive substrate layer in the embodiment of the present invention.

Description of the reference numerals

1: a one-dimensional conductive nanomaterial; 2: a conductive substrate; 3: and (3) coating a polymer.

Detailed Description

Various exemplary embodiments, features and aspects of the invention will be described in detail below. The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In other instances, methods, means, devices and steps which are well known to those skilled in the art have not been described in detail so as not to obscure the invention.

All units used in the present invention are international standard units unless otherwise stated, and numerical values and numerical ranges appearing in the present invention should be understood to include systematic errors inevitable in industrial production.

In the present invention, "substantially" means an error of not more than 5%, etc.

First embodiment

A first embodiment of the present invention provides a flexible bioelectrode comprising: a conductive substrate 2; a one-dimensional conductive nanomaterial 1 formed on the surface of the conductive substrate 2 in a manner that the axial direction of the one-dimensional conductive nanomaterial 1 is approximately orthogonal to the surface of the conductive substrate 2, wherein the diameter of the one-dimensional conductive nanomaterial 1 is 20-200 nm, and the length of the one-dimensional conductive nanomaterial 1 is 30-100 μm; wherein, at least the contact interface area of the conductive substrate 2 and the one-dimensional conductive nanometer material 1 is provided with a polymer coating 3.

The flexible bioelectrode of the invention is a bioelectrode which still keeps normal functions in the processes of bending, folding, even stretching and deformation and the like under the action of external force. According to the invention, the one-dimensional conductive nano material 1 is tightly fixed on the conductive substrate 2, so that the one-dimensional conductive nano material 1 can exert the advantage of the length-diameter ratio in the process of measuring bioelectricity signals of a human body, and the effective contact between the flexible bioelectrode and skin lines is realized. According to the invention, the polymer coating 3 is arranged, so that the connection firmness of the one-dimensional conductive nano material 1 and the bottom conductive substrate 2 is ensured, and the overall elastic modulus of the device is effectively reduced, so that the flexible bioelectrode has better comfort in the process of carrying out human body bioelectricity measurement by being attached to the skin, and cannot penetrate into the skin and cause skin damage. Specifically, the method comprises the following steps:

< conductive substrate >

The conductive substrate 2 of the present invention is preferably a flexible conductive substrate, which is a conductive substrate having mechanical flexibility. Specifically, the flexible conductive substrate may be classified into two types according to the composition: one is a single type conductive substrate having flexibility itself, such as smooth metal electrospinning, etc.; the other type is a composite flexible conductive substrate which takes a flexible material as a supporting film and forms a conductive layer on the surface of the supporting film, and the typical representatives of the flexible conductive substrate are metal/high polymer material composite conductive substrates and the like.

In the present invention, a single type of conductive body having flexibility itself may be selected as the flexible conductive substrate. Of course, a composite flexible conductive substrate may also be used in the present invention, specifically, a metal/polymer material composite conductive substrate, and the like, and a composite conductive substrate is preferably used.

Specifically, the conductive substrate 2 of the present invention may include a support film; and a conductive layer formed on at least one surface of the support film. Wherein the conductive layer is a flat metal conductive layer, such as: a gold (Au) conductive layer, a silver (Ag) conductive layer, a copper (Cu) conductive layer, and the like, and the metal conductive layer may deposit a metal material on the flexible support film by electron beam evaporation deposition, magnetron sputtering, or the like. While the material used as the support film may be a polymer material, such as: polyimide (PI), polyethylene terephthalate (PET), polyvinyl alcohol (PVA), Polycarbonate (PC), silicone resin, and the like.

Further, when the silver nanowire is grown, the grown silver nanowire has better adhesion with the gold conductive layer because the crystal constants of silver and gold are similar. That is, a silver conductive layer or a gold conductive layer may be used for growing the silver nanowire, but since silver is not as well oxidized as gold, a gold conductive layer is preferably used. When the conductive layer is a gold conductive layer, a metallic chromium layer is provided between the support film and the conductive layer in order to strengthen the interfacial bonding force between the support film (e.g., when polyimide is used as the material of the support film) and the conductive layer. When the conducting layer is a copper conducting layer, a silver conducting layer and other conducting layers, the interface bonding force between the conducting layer and the supporting film is strong, and a metal chromium layer is not required to be arranged.

In the present invention, in order to more effectively function as the conductive substrate 2, the thickness of the support film is 3 to 20 μm, preferably 5 to 15 μm, and more preferably 6 to 12 μm. The thickness of the conductive layer is 50 to 500nm, preferably 100 to 400nm, and more preferably 150 to 300 nm. The thickness of the metal chromium layer can be 3-20 nm, preferably 5-15 nm, and more preferably 7-12 nm.

< one-dimensional conductive nanomaterial >

The one-dimensional conductive nanomaterial 1 of the present invention is a conductive material having a high aspect ratio. Due to the micro-nano scale effect, the one-dimensional conductive nano material 1 has a very large specific surface area, good conductivity and mechanical properties. In order to solve the problem of contact between a bioelectrode and a skin gap, i.e., the problem of contact resistance between a flexible bioelectrode and the skin, the inventors of the present invention have found that a one-dimensional conductive nanomaterial 1 is formed on the surface of a conductive substrate 2 in such a manner that the axial direction of the nanomaterial is substantially perpendicular to the surface of the conductive substrate 2, so that a microvilli-like electrode pattern can be formed, and a bioelectrode which can be more sufficiently contacted with the skin can be obtained.

Specifically, the one-dimensional conductive nanomaterial 1 may be grown on the surface of the conductive substrate 2 by electrochemical deposition or vapor deposition using an Anodic Aluminum Oxide (AAO) template having a through hole in such a manner that the axial direction of the nanomaterial is substantially orthogonal to the surface of the conductive substrate. The electrochemical deposition is a technique in which current is transferred through positive and negative ions in an electrolyte solution under the action of an external electric field, and an oxidation-reduction reaction of gain and loss electrons occurs on an electrode to form a plating layer. Vapor deposition is a technique for forming functional or decorative metallic, non-metallic, or compound coatings on the surface of a workpiece using physical, chemical processes that occur in the vapor phase. The invention can grow the one-dimensional conductive nano material 1 by using the anodic alumina template with the through hole and adopting the electrochemical deposition or vapor deposition method.

In the present invention, the diameter of the one-dimensional conductive nanomaterial 1 is 20 to 200nm, the length is 30 to 100 μm, and the aspect ratio (ratio of length to diameter) is 150 to 5000, preferably 300 to 4000, more preferably 500 to 2000, further preferably 600 to 1500, and further preferably 700 to 1200. Therefore, the one-dimensional conductive nanomaterial 1 of the present invention has a suitable length-diameter ratio, so that contact to skin lines can be achieved. Based on the size of the one-dimensional conductive nano material 1, an anodic alumina template with an average pore diameter of about 20-200 nm and an axial length of about 30-100 μm of a through hole can be selected.

Specifically, the one-dimensional conductive nanomaterial 1 of the present invention is not particularly limited, and may be a one-dimensional conductive nanomaterial 1 commonly used in the art. The one-dimensional conductive nanomaterial 1 of the present invention may include nanowires and/or nanotubes, preferably including one or a combination of two or more of silver nanowires, gold nanowires, and carbon nanotubes. The silver nanowires can fully exert the advantage of the length-diameter ratio of the silver nanowires, and the silver nanowires can fully contact skin lines.

< Polymer coating >

The invention is provided with a polymer coating 3 at least in the contact interface area of the conductive substrate 2 and the one-dimensional conductive nano material 1. The polymer coating 3 can play a role in protecting the conductive substrate 2 and the root of the one-dimensional conductive nano material 1, and can also enable the flexible bioelectrode to have certain extensibility (stretching) and better flexibility. In the present invention, the thickness of the polymer coating layer 3 may be 1 to 15 μm, preferably 3 to 12 μm, and more preferably 5 to 10 μm.

Preferably, the conductive substrate 2 has the polymer coating 3 on all surfaces thereof for convenience of preparation and better exertion of the effects of the polymer coating 3. I.e. as shown in fig. 1, the conductive substrate 2 is wrapped inside the polymer coating. At this time, the farthest distance (including the thickness of the conductive substrate 2) between the surface of the polymer coating 3 close to the one-dimensional conductive nanomaterial 1 and the surface far from the one-dimensional conductive nanomaterial 1 is 30 to 500 μm as a whole.

The polymer coating 3 may be obtained by curing using a polymer solution. In the present invention, the "solidification" refers to a change of the binder, the liquid polymer solution, and the like from a use form of a liquid state to a form of a solid state. For the means of curing, for example, the binder, the solution in the liquid polymer solution may be removed in the form of drying or the like. In some preferred embodiments of the present invention, the removal solution may be performed under heating. Within the scope of the "curing" according to the invention, the cured product is allowed to form a network structure at least partially inside. Such a network structure may be formed by condensation to form a covalent bond, or may be formed through a non-covalent bond such as intermolecular force. The polymer coating 3 may have a certain elasticity after curing, thereby further providing flexibility to the flexible bioelectrode of the present invention.

In the present invention, the polymer coating 3 is derived from an organosilicon compound, and compounds in which organic groups are bonded to silicon atoms through oxygen, sulfur, nitrogen, or the like are also generally regarded as organosilicon compounds. Preferably, the organosilicon compound comprises silicone rubber and/or siloxane.

In the present invention, the silicone rubber used is a silicone rubber. Silicone rubbers are compounds which contain Si-C bonds and at least one organic radical which is directly bonded to the silicon atom. The siloxane used is an organosiloxane. The organosiloxane is a polymer containing Si-O-Si bonds to form a main chain structure. The silicone rubber and/or siloxane can deform remarkably under weak stress, and can be quickly restored to be close to the original state and size after the stress is relaxed.

By way of example, the silicone rubber may be a platinum catalyzed silicone rubber, such as: ecoflex0020, ecoflex0030, etc. The siloxane may be, for example, Polydimethylsiloxane (PDMS) or the like.

According to the invention, the polymer coating 3 is arranged, so that the connection firmness of the one-dimensional conductive nano material 1 and the bottom conductive substrate 2 is ensured, and the overall elastic modulus of the device is effectively reduced, so that the flexible bioelectrode has better comfort in the process of carrying out human bioelectricity measurement by being attached to the skin.

Second embodiment

The second embodiment of the present invention provides a method for preparing the flexible bioelectrode of the first embodiment of the present invention, which specifically comprises the following steps:

Typically, the invention uses an anodic alumina template with through holes to grow one-dimensional conductive nano-materials on the surface of the conductive substrate in a way that the axial direction of the nano-materials is approximately orthogonal to the surface of the conductive substrate by adopting an electrochemical deposition or vapor deposition method.

Specifically, the preparation method comprises the following steps:

step 1, taking an anodic aluminum oxide template;

step 3, removing the adhesive in the through hole;

step 4, growing a one-dimensional conductive nano material in the through hole by adopting an electrochemical deposition or vapor deposition method;

The main chemical component of the anodic alumina template is aluminum oxide (Al)₂O₃). When aluminum is used as an anode, oxidation-reduction reaction can occur, so that a layer of film consisting of aluminum oxide is formed on the surface of the aluminum electrode, namely the anodic aluminum oxide template. Since the anodized aluminum template has through holes, one-dimensional conductive nanomaterials can be grown in the through holes.

In the process of growing the one-dimensional conductive nano material by using the anodic aluminum oxide template, a layer of adhesive can be coated on the conductive substrate. The adhesive may be a liquid organic substance, and it is preferable to use a photoresist to perform an adhesive function for the sake of convenience of preparation. When a photoresist is used as the adhesive, a thick glue may be used, and a thin glue may be used, and a thick glue is preferably used, for example: thick glue 4620, thick glue SU8, etc.

When the photoresist is used as the binder, the invention can tightly press the anodic aluminum oxide template and the conductive substrate when the photoresist is not cured, the anodic aluminum oxide template and the conductive substrate are bonded together after curing, the photoresist in the holes of the anodic aluminum oxide template is etched by using a plasma etching (RIE) method, and then subsequent electrochemical deposition or vapor deposition is carried out, so that the one-dimensional conductive nano material grows in the through holes.

Further, between the step 3 and the step 4, the preparation method further comprises the step of growing the one-dimensional conductive nano material regionally. Specifically, the regional growth of the one-dimensional conductive nanomaterial can be realized by performing patterned masking or patterned photolithography processing according to the arrangement mode of the one-dimensional conductive nanomaterial.

Specifically, the regional growth comprises the following steps:

step b, coating a layer of photoresist on the surface of the metal substance;

c, removing a part of the metal substance and the photoresist on the surface of the part of the metal substance according to the arrangement mode of the one-dimensional conductive nano material;

For the photoresist, it can be classified into a negative photoresist and a positive photoresist according to the chemical reaction mechanism and the development principle of the photoresist. The insoluble matter formed after illumination is negative glue; on the contrary, the positive glue is insoluble in some solvents and becomes a soluble substance after being irradiated by light. By utilizing the performance, the photoresist is used as a coating, a required pattern can be etched on the surface of the metal substance, and the one-dimensional conductive nano material can grow regionally according to the pattern.

In the present invention, the photoresist to be subjected to photolithography is not particularly limited as long as the requirements of the present invention can be achieved. In general, the photoresist for performing photolithography may preferably use a thin resist such as: AZ5214, and the like.

In the present invention, the arrangement of the one-dimensional conductive nanomaterial is not particularly limited, and may be any arrangement.

Specifically, a layer of metal substance may be deposited on the surface of the anodized aluminum template away from the conductive substrate by electron beam evaporation deposition. Electron beam evaporation is one kind of vacuum evaporation coating, and is one method of heating evaporation material directly with electron beam in vacuum condition to evaporate the evaporation material and transport it to the base plate for condensation to form film on the base.

The thickness of the metal substance layer obtained by electron beam evaporation deposition can be 0.5-3 μm, preferably 1-2 μm. And then coating a layer of photoresist on the surface of the metal substance. And etching off part of the metal substance and the photoresist on the surface of the part of the metal substance by using a photoetching method so as to realize patterning etching, thereby obtaining a model with a required arrangement mode. At the surface of the anodic aluminum oxide template far away from the conductive substrate, the etched part of the metal substance and the photoresist will expose part of the through hole, and the through hole is still closed where the metal substance exists.

The metal substance may preferably be metallic copper, gold, titanium, or the like, and metallic copper is preferably used for cost reduction.

When growing one-dimensional conductive nano material, the model is used as a working electrode, and a platinum electrode is used as a counter electrode to carry out direct current electrochemical deposition in electrolyte. The nanowire structure is not deposited because the electrolyte cannot enter the copper and photoresist covered area. The nanowire will only grow where the via is exposed. Therefore, the one-dimensional conductive nano material can be regionally grown according to a required arrangement mode.

In the present invention, the specific composition of the electrolyte is not particularly limited as long as the requirements of the present invention are satisfied. For example: in the direct electrochemical deposition of silver nanowires, a solution of a silver salt is added to the electrolyte, for example: AgNO₃Etc. to achieve the growth of the silver nanowires.

In the invention, the coating can be one or a combination of more than two of dipping, spin coating, spray coating and pouring, and the polymer solution can be uniformly covered on at least the contact interface area of the conductive substrate and the one-dimensional conductive nano material through the coating.

Preferably, the coating further comprises coating the polymer solution on all surfaces of the conductive substrate.

Before coating, the remaining metal substance and the photoresist on the surface of the remaining metal substance need to be removed. For example: the removal can be performed by means of wet etching. For example: the remaining metal species and the remaining photoresist on the surface of the metal species may be removed using a copper etchant and acetone, respectively. At this time, a gap of about 5 to 10 μm is formed between the anodized aluminum template and the conductive substrate, and a polymer solution may be coated in the gap and then cured to obtain a polymer coating. In order to facilitate the preparation and obtain a flexible bioelectrode with more excellent performance, the polymer solution is preferably coated on all surfaces of the conductive substrate in a pouring manner.

Further, as for the method for preparing the conductive substrate, the present invention is not particularly limited, and the conductive substrate can be prepared by a preparation method commonly used in the art. Specifically, the method comprises the following steps: the preparation method of the conductive substrate comprises the step of connecting the conductive layer with the supporting film. For example: a conductive material can be deposited on the surface of the support film using electron beam evaporation to form a conductive layer.

Preferably, a metal chromium layer is further arranged between the conductive layer and the support film. I.e. a metallic chromium layer is deposited by electron beam evaporation before the deposition of the conductive material on the surface of the support film.

Examples

Embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Examples

1. Preparation of electrically conductive substrates

The conductive substrate in this embodiment is mainly composed of a flexible commercial Polyimide (PI) film and an overlying gold conductive layer. The thickness of the commercial polyimide film was 8 μm.

Fig. 2 shows a process for preparing the conductive substrate. As shown in fig. 2, the conductive substrate is prepared by the following steps: a clean glass plate is prepared, a layer of Polydimethylsiloxane (PDMS) is spin-coated on the clean glass plate at the rotating speed of 300r/min, and the glass plate is heated at 100 ℃ for 30min to be cured. And after curing, flatly sticking the prepared flexible conductive substrate layer on polydimethylsiloxane. Then, a metal chromium layer with the thickness of 10nm is deposited on the surface of the polyimide by electron beam evaporation, and then a metal gold layer with the thickness of 200nm is deposited on the metal chromium layer to serve as a conductive layer.

2. Adhesion of conductive substrates to Anodized Aluminum (AAO) templates

Fig. 3 shows the bonding process of the conductive substrate and the anodized aluminum template. The method comprises the following specific steps: spin-coating a layer of AZ4620 photoresist on the prepared conductive substrate at 3000r/min, then slightly pressing and pasting an anodized aluminum template sheet (with an average pore diameter of 80-100 nm and a thickness of 80 microns) with through holes on the uncured AZ4620 photoresist, placing the anodized aluminum template sheet on a heating plate, heating the anodized aluminum template sheet at 110 degrees, and keeping the anodized aluminum template sheet for 90 seconds for curing, thereby completing the bonding of the conductive substrate and the anodized aluminum template (shown in (a) of fig. 3). The above-described overall structure is placed in a reactive ion etcher for plasma etching (RIE). At this time, the AZ4620 photoresist in the portion of the anodized aluminum template having the through-hole is completely etched, and the portion covered by the anodized aluminum template is still remained (shown in fig. 3 (b)).

3. Patterned masking of anodized aluminum template surfaces and localized growth of silver nanowires

Fig. 4 shows the patterned masking of the anodized aluminum template surface and the localized growth of silver nanowires. The method comprises the following specific steps: and depositing a layer of metal copper with the thickness of 1.5 microns on the surface of the anodic aluminum oxide template far away from the conductive substrate by using electron beam evaporation deposition. Subsequently, a layer of AZ5214 photoresist (shown in fig. 4 (a)) is spin-coated on the surface of the copper metal. By means of photolithography, a part of the metallic copper and the part of the photoresist of the metallic copper surface AZ5214 are etched away, and patterned etching of copper is achieved (shown in fig. 4 (b)). At the surface of the anodic aluminum oxide template far away from the conductive substrate, the part etched by the metal copper and the AZ5214 photoresist is exposed to a part of the through hole, and the through hole is closed at the place where the metal copper exists, so that a model is obtained.

The model is used as a working electrode, and a platinum electrode is used as a counter electrode to carry out direct current electrochemical deposition in electrolyte. The electrolyte consists of 20g/L AgNO₃And 20g/L of H₃BO₃Is added with HNO₃The pH was adjusted to 2 for growing silver nanowires. The applied DC voltage is 0.2V, and the deposition time is 40 min. Since the electrolyte cannot enter the copper-covered area, the silver nanowires are not deposited. The silver nanowire grows only where the via hole is exposed. Thereby, the deposition of the silver nanowires in a localized manner can be performed according to the arrangement of the silver nanowires (shown in fig. 4 (c)).

4. Coating polymer solutions

Fig. 5 shows a process for preparing a coating polymer solution. The remaining metal copper and the AZ5214 photoresist on the surface of the remaining metal copper are removed by wet etching using a copper etching solution and acetone, respectively (shown in fig. 5 (a)). At this point, a gap of about 10 microns will be left between the anodized aluminum template and the conductive substrate. After the flexible substrate and the root of the nanowire are completely wrapped by pouring the PDMS solution, the flexible substrate and the root of the nanowire are cured by heating (shown in fig. 5 (b)). The obtained product was then successively put into a NaOH solution of 10% by mass and 4mol/L to carry out anodic alumina template etching (shown in FIG. 5 (c)). After the anodized aluminum template is removed, the flexible bioelectrode is peeled off from the surface of the glass sheet, and the product shown in fig. 1 can be obtained (shown in fig. 5 (d)).

The flexible bioelectrode of the present invention may be used on the skin surface to detect electrical signals associated with physiological health conditions and the like. The flexible bioelectrode of the present invention can realize effective contact with skin lines. In addition, the measurement noise of the flexible bioelectrode is obviously reduced along with the improvement of the fit between the device and the human body, and the flexible bioelectrode does not penetrate into the skin and cause skin damage. Therefore, the method can accurately acquire the monitoring of cardiovascular diseases, the monitoring of sports of athletes, the research on the brain nervous system and the like in real time.

The above examples of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A flexible bioelectrode, comprising:

a conductive substrate;

the one-dimensional conductive nanomaterial grows on the surface of the conductive substrate in a mode that the axial direction of the nanomaterial is approximately orthogonal to the surface of the conductive substrate, and the one-dimensional conductive nanomaterial grows on the surface of the conductive substrate in a mode that the axial direction of the nanomaterial is approximately orthogonal to the surface of the conductive substrate by using an anodic alumina template with a through hole and adopting an electrochemical deposition or vapor deposition method;

the diameter of the one-dimensional conductive nano material is 20-200 nm, and the length of the one-dimensional conductive nano material is 30-100 mu m; the length-diameter ratio of the one-dimensional conductive nano material is 150-5000; wherein

At least the contact interface area of the conductive substrate and the one-dimensional conductive nano material is covered with a polymer coating; the polymer coating is derived from an organic silicon compound, the organic silicon compound comprises silicon rubber and/or siloxane, and the thickness of the polymer coating is 1-15 mu m.

2. The flexible bioelectrode according to claim 1, characterized in that it has a polymer coating on all surfaces of said electrically conductive substrate.

3. The flexible bioelectrode according to claim 1 or 2, characterized in that said electrically conductive substrate comprises:

supporting the film; and

and the conductive layer is formed on at least one surface of the support film.

4. The flexible bioelectrode according to claim 3, characterized in that a metallic chromium layer is arranged between said support membrane and said conductive layer.

5. The flexible bioelectrode according to claim 3, characterized in that said conductive layer is a metal conductive layer comprising one or a combination of two or more of a gold conductive layer, a silver conductive layer, a copper conductive layer; and/or

6. The flexible bioelectrode according to claim 1 or 2, characterized in that said one-dimensional electrically conductive nanomaterial comprises nanowires and/or nanotubes.

7. The flexible bioelectrode according to claim 6, wherein said one-dimensional conductive nanomaterial comprises one or a combination of two or more of silver nanowires, gold nanowires, and carbon nanotubes.

8. A preparation method of the flexible bioelectrode is characterized by comprising the following steps:

growing a one-dimensional conductive nano material on the surface of the conductive substrate in a mode that the axial direction of the conductive nano material is approximately orthogonal to the surface of the conductive substrate, and growing the one-dimensional conductive nano material on the surface of the conductive substrate in a mode that the axial direction of the conductive nano material is approximately orthogonal to the surface of the conductive substrate by using an anodic alumina template with a through hole and adopting an electrochemical deposition or vapor deposition method;

the diameter of the one-dimensional conductive nano material is 20-200 nm, and the length of the one-dimensional conductive nano material is 30-100 mu m; the length-diameter ratio of the one-dimensional conductive nano material is 150-5000;

coating a polymer solution on at least the contact interface area of the conductive substrate and the one-dimensional conductive nano material, and forming a polymer coating after curing; the polymer coating is derived from an organic silicon compound, the organic silicon compound comprises silicon rubber and/or siloxane, and the thickness of the polymer coating is 1-15 mu m.

9. The method of manufacturing according to claim 8, comprising the steps of:

step 1, taking an anodic aluminum oxide template;

step 3, removing the adhesive in the through hole;

10. The method for preparing a nano-material of claim 9, wherein between the step 3 and the step 4, the method further comprises the step of growing the one-dimensional conductive nano-material regionally.

11. The method of claim 10, wherein the regionally growing comprises the steps of:

b, coating a layer of photoresist on the surface of the metal substance;

12. The method of any one of claims 8-11, wherein the coating further comprises coating the polymer solution on all surfaces of the conductive substrate.

13. The production method according to any one of claims 8 to 11, wherein the production method of the conductive substrate comprises a step of connecting a conductive layer to a support film.

14. The method according to claim 13, wherein a metallic chromium layer is further deposited between the conductive layer and the support film.