WO2023097766A1

WO2023097766A1 - Preparation method for ultrathin stretchable thin film electrode

Info

Publication number: WO2023097766A1
Application number: PCT/CN2021/137764
Authority: WO
Inventors: 刘志远; 李光林; 谢瑞杰; 赵阳; 于玫; 李韩飞
Original assignee: 中国科学院深圳先进技术研究院
Priority date: 2021-12-01
Filing date: 2021-12-14
Publication date: 2023-06-08
Also published as: CN114360809A

Abstract

A preparation method for an ultrathin stretchable thin film electrode. The method comprises mixing dimethyl siloxane with a cross-linking agent, then dripping the mixture on a water phase liquid level, heating and pre-curing same to obtain a polydimethylsiloxane thin film, and transferring the film to an annular substrate to obtain an electrode base; adsorbing the electrode base on a silicon wafer, and evaporating a metal conductive layer on the polydimethylsiloxane thin film on the electrode base to obtain an electrode. A polydimethylsiloxane thin film is prepared by means of a liquid surface spreading method. After the thin film is pre-cured, a metal is evaporated on the surface of the thin film to prepare a conductive layer; in addition, the polydimethylsiloxane thin film is completely cured, and part of the metal permeates into the thin film, such that the acting force between the conductive layer and the base is significantly increased, and thus the prepared thin film electrode has a good stability. The thickness of the ultrathin stretchable thin film electrode may be less than 10 μm, and the electrode can be effectively attached to the skin and can achieve high-performance monitoring of physiological electric signals of the human body.

Description

A kind of preparation method of ultrathin stretchable film electrode

technical field

The invention relates to the technical field of sensors, in particular to a method for preparing an ultrathin stretchable film electrode.

Background technique

The human body produces a wealth of electrical signals during physiological activities, such as ECG, EEG, and EMG, which contain important information reflecting the health status of the human body. Monitoring these electrical signals has important applications in the monitoring and diagnosis of related diseases, artificial prosthetics, human-computer interaction and other fields. The electrodes used in the market for monitoring human physiological electrical signals are mainly gel electrodes. However, during long-term use, it is prone to dehydration, causing allergies to users, and other problems, which affect its normal use. Therefore, flexible and stretchable dry electrodes have attracted much attention because they can be used directly without additional application of conductive gel. Compared with gel electrodes, due to the poor adhesion of dry electrodes to the skin, the contact resistance between them and the skin is relatively large, which seriously reduces the accuracy of electrical signals. Reducing the bending stiffness of the electrode by reducing its thickness is a means to improve the accuracy of electrical signals. When the thickness of the electrode is less than 10 μm, the adhesion between the electrode and the skin can be effectively improved, and the quality of the collected signal can be significantly improved. Therefore, the preparation of ultra-thin flexible stretchable electrodes with better adhesion to the skin has become a research hotspot.

The current preparation method of ultra-thin electrodes is usually to prepare a sacrificial layer on a solid substrate, and use the sacrificial layer to prepare an ultra-thin film by scraping, spin coating, spraying, etc., and prepare a conductive layer on the ultra-thin film to obtain an ultra-thin electrode. . Due to the large adsorption force between the ultra-thin electrode and the solid substrate, it usually needs to be attached to the skin by transfer, which is difficult to operate. In addition, the conductive layer is usually prepared by magnetron sputtering, thermal evaporation and other methods to prepare a metal layer or use a conductive nanoparticle dispersion to form a pattern. The small force between it and the ultra-thin film makes the electrode It is easy to peel off the conductive layer, which affects the service life of the device. For example, the Chinese patent application number 201910177997.0, a method for preparing an ultra-thin flexible array surface electromyography electrode, discloses a preparation method for an ultrathin flexible array surface electromyography electrode. After a sacrificial layer is formed on the solid substrate by a glue spreader, a flexible substrate is also formed on it by a glue spreader, and two metal layers are sputtered to prepare a flexible electrode. The thickness of the prepared electrode is 50-500 μm, and the adhesion to the skin is poor. In order to improve the stability of the electrode, two metals need to be evaporated to increase the force between the conductive layer and the substrate. The preparation process is cumbersome and the mobility of the electrode is poor. The Chinese patent application number 201820346884.X, a skin-like multi-channel surface muscle electrode based on a mesh structure design, discloses a skin-like multi-channel surface muscle electrode based on a mesh structure design. Similar to the above-mentioned patent, a sacrificial layer, a thin film, and two metal layers are sequentially prepared on the glass, and a flexible electrode is obtained after being released from the glass. The thickness of the prepared electrode is several microns, which can have excellent adhesion to the skin, but the preparation process is cumbersome and the mobility of the electrode is poor.

technical problem

In view of the above technical problems, the present invention provides a method for preparing an ultra-thin stretchable film electrode, which uses a liquid surface spreading method to prepare a pre-cured ultra-thin polydimethylsiloxane film, and deposits a layer of metal on it. Electrodes are prepared as conductive layers.

technical solution

In order to achieve the above object, the technical scheme that the present invention takes is:

The invention provides a method for preparing an ultra-thin stretchable film electrode, comprising the following steps:

(1) Preparation of ultra-thin stretchable substrates by liquid surface spreading method:

After mixing dimethylsiloxane and crosslinking agent, drop it on the surface of the water phase to obtain a spread film, and obtain a polydimethylsiloxane film after heating and pre-curing; transfer the polydimethylsiloxane film Get the electrode base on the ring substrate;

(2) Preparation of ultra-thin stretchable film electrodes by thermal evaporation method:

Adsorbing the electrode substrate obtained in step (1) on a silicon wafer, and evaporating a metal conductive layer on the polydimethylsiloxane film on the electrode substrate to obtain the electrode.

As a preferred embodiment, in step (1), the polydimethylsiloxane film has a thickness of 3 μm to 30 μm, such as 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm or any thickness in between.

As a preferred embodiment, in step (1), the curing temperature of the pre-curing is 40-120°C, and the curing time is preferably 45-120 min;

Preferably, in step (1), the pre-curing is curing at 60°C for 60 minutes.

In some specific embodiments, in step (1), the curing temperature of the pre-curing is 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C or any temperature in between.

In some specific embodiments, in step (1), the curing time of the pre-curing is 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, 95 min, 100 min, 105 min, 110 min, 115 min, 120 min or any time in between.

As a preferred embodiment, in step (1), the Young's modulus of the polydimethylsiloxane film obtained by the pre-curing is not more than 700 kPa.

In some specific embodiments, in step (1), the Young's modulus of the pre-cured polydimethylsiloxane film is 500 kPa, 550 kPa, 600 kPa, 650 kPa, 700 kPa or Any Young's modulus between them.

As a preferred embodiment, in step (1), the mass ratio of the dimethylsiloxane to the crosslinking agent is 5-15:1.

In some specific embodiments, in step (1), the mass ratio of the dimethylsiloxane to the crosslinking agent is 5: 1, 7: 1, 10: 1, 13: 1, 15: 1 or any ratio between them.

In the technical solution of the present invention, in step (1), the material of the annular substrate is not limited, as long as the film can be picked up, it is made of polyethylene terephthalate.

In the technical solution of the present invention, the thickness of the polydimethylsiloxane film can be realized by controlling the amount of dimethylsiloxane and crosslinking agent.

As a preferred embodiment, in step (2), the evaporation rate of the evaporation is 0.1-10 Å/s, preferably 0.5 Å/s.

In some specific embodiments, in step (2), the evaporation rate of the evaporation is 0.1 Å/s, 1 Å/s, 2 Å/s, 3 Å/s, 4 Å/s, 5 Å/s, 6 Å/s, 7 Å/s, 8 Å/s, 9 Å/s, 10 Å/s or any evaporation rate in between.

As a preferred implementation manner, in step (2), the thickness of the vapor-deposited metal conductive layer is 100 nm to 300 nm, preferably 150 nm.

In some specific embodiments, in step (2), the thickness of the evaporated metal conductive layer is 100 nm, 120 nm, 150 nm, 170 nm, 200 nm, 220 nm, 250 nm, 270 nm, 300 nm nm or any thickness in between.

As a preferred embodiment, in step (2), the metal of the metal conductive layer is selected from any one of gold, silver, platinum, titanium, iridium and platinum-iridium alloy;

As a preferred embodiment, in step (2), a sacrificial layer is provided on the silicon wafer, and the sacrificial layer is prepared by a spin coating method.

In the technical scheme of the present invention, the polydimethylsiloxane film is used to prepare the electrode, which can be adsorbed on the annular substrate by van der Waals force, and the silicon wafer is used as the support for the evaporated metal conductive layer, which is in contact with the electrode base Pre-coated with a sacrificial layer. In the process of preparing the conductive layer by evaporation, the metal clusters partly penetrate into the pre-cured polydimethylsiloxane film, and the film is completely cured to form a flexible and stretchable electrode. After the evaporation is completed, the sacrificial layer can be dissolved. The electrode is separated from the silicon wafer to obtain a flexible and stretchable electrode supported on a ring-shaped substrate.

The second aspect of the present invention provides the ultra-thin stretchable film electrode obtained by the above preparation method.

The above technical solution has the following advantages or beneficial effects:

In the present invention, the dimethyl siloxane monomer is mixed with a crosslinking agent and then spread into a thin film on the surface of the water phase, and after pre-curing, it is transferred to a ring-shaped substrate, and metal is evaporated on its surface as a conductive layer to prepare the Ultrathin flexible stretchable film electrodes.

Beneficial effect

The present invention has the following advantages:

1. The present invention prepares polydimethylsiloxane film by spreading method on the liquid surface. Polydimethylsiloxane prepolymer is easy to spread into a high-quality film with uniform thickness on the liquid surface. By controlling the dimethylsiloxane The amount of oxane and cross-linking agent can control the thickness of the film, thereby regulating the thickness of the electrode. The thickness of the electrode prepared by it can be as thin as 3 μm, and the preparation method is simple and fast, and has low requirements for instruments;

2. Compared with the solid substrate, the force between the water phase liquid surface and the thin polydimethylsiloxane film is small, so the film can be directly transferred from the water to the substrate, which increases the operability and increases the stability of the electrode. maneuverability;

3. Compared with the preparation method in the prior art by evaporating an adhesion layer between the polydimethylsiloxane film and the conductive layer, the film electrode prepared by the present invention uses a polydimethylsiloxane film that is not Fully cured film, during the evaporation process, the polydimethylsiloxane film is completely cured into a flexible and stretchable electrode, and at the same time, part of the metal penetrates into the film, which significantly increases the force between the conductive layer and the film substrate, so that all The prepared thin film electrode has excellent stability, thereby improving the service life of the electrode.

4. The electrode prepared by the present invention, because its thickness can be less than 10 μm, can be better attached to the skin, and can realize high-performance monitoring of human physiological electrical signals.

Description of drawings

Fig. 1 is a flow chart of the preparation of ultra-thin stretchable film electrodes in Examples 1-4 of the present invention.

Fig. 2 is a diagram of electrode characterization results of Example 1 of the present invention.

Fig. 3 is a diagram of electrode characterization results of Example 2 of the present invention.

Fig. 4 is a diagram of electrode characterization results of Example 3 of the present invention.

Embodiments of the present invention

The following embodiments are only some of the embodiments of the present invention, not all of them. Therefore, the detailed description in the embodiments of the invention provided below is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.

The crosslinking agent used in the following examples is Dow Corning 184 silicone rubber.

Example 1:

As shown in Figure 1, mix dimethylsiloxane and crosslinking agent at a mass ratio of 5:1 to obtain a dimethylsiloxane prepolymer, and use a syringe to prepolymerize about 20 μL of dimethylsiloxane The polydimethylsiloxane film was dropped on a water surface with a diameter of 9 cm and spread for 10 min to form a film, which was pre-cured in an oven at 60 °C for 80 min to obtain a polydimethylsiloxane film with a thickness of 3 μm and a Young’s modulus of 500 kPa; picked up with a polyethylene terephthalate (PET) ring and attached to a silicon wafer spin-coated with sodium polystyrene sulfonate as a sacrificial layer (silicon wafer not shown) , evaporate a 150 nm thick gold conductive layer at a speed of 0.5 Å/s, and dissolve the sacrificial layer to obtain an ultra-thin stretchable film electrode.

The ultra-thin stretchable film electrode prepared in this example is shown in Figure 2, where Figure 2a is a picture of an ultra-thin stretchable electrode; Figure 2b is a cross-sectional SEM image of the electrode, and the thickness of the electrode is 3 μm; Figure 2c is the surface of the electrode SEM image, it can be seen from the figure that there are regular wrinkles on the surface of the electrode; after the conductive layer is adhered to the conductive layer with adhesive tape, the adhesion between the conductive layer of the electrode and the substrate is characterized, and it is found that the electrode can still maintain good conductivity; Fig. 2d In order to characterize the stretchability of the electrode, the resistance during the stretching process is tested, and the stretching rate of the electrode when it is insulated is its stretchability. The stretchability of the electrode prepared in this example exceeds 140%.

Example 2:

Mix dimethylsiloxane and cross-linking agent at a mass ratio of 10:1 to obtain a dimethylsiloxane prepolymer, and use a syringe to drop about 80 μL of the obtained dimethylsiloxane prepolymer on the diameter Spread on a water surface of 9 cm for 10 min to form a film, and pre-cure it in an oven at 40°C for 120 min to obtain a polydimethylsiloxane film with a thickness of 12 µm and a Young's modulus of 650 kPa; Pick it up with a PET ring, attach it to a silicon wafer spin-coated with sodium polystyrene sulfonate as a sacrificial layer, vapor-deposit a 100 nm thick gold conductive layer at a speed of 0.1 Å/s, and dissolve the sacrificial layer to prepare Ultrathin and stretchable film electrodes.

The thin film electrode prepared in this example has a thickness of 12 μm, and the electrode can still maintain good conductivity after the conductive layer is adhered with adhesive tape. The characterization results of the ultra-thin stretchable electrode prepared in this example are shown in Figure 3, in which Figure 3a is the surface SEM image of the electrode. It can be seen from the figure that regular wrinkles are formed on the electrode surface; Figure 3b is the electrode surface. Characterized by stretchability, the stretchability of the prepared electrodes exceeds 70%.

Example 3:

Mix dimethylsiloxane and cross-linking agent at a mass ratio of 15:1 to obtain a dimethylsiloxane prepolymer, and use a syringe to add about 200 μL of the obtained dimethylsiloxane prepolymer dropwise Spread the film on a water surface with a diameter of 9 cm for 10 min, and precure it in an oven at 120 °C for 45 min to obtain a polydimethylsiloxane film with a thickness of 30 µm and a Young's modulus of 700 kPa; pick it up with a PET ring, attach it to a silicon wafer spin-coated with sodium polystyrene sulfonate as a sacrificial layer, evaporate a 300 nm thick gold conductive layer at a speed of 10 Å/s, and dissolve the sacrificial layer The ultra-thin stretchable electrode is prepared afterward.

The electrode prepared in this example has a thickness of 30 μm, and the electrode still maintains good conductivity after the conductive layer is adhered with adhesive tape. The characterization results of the ultra-thin stretchable electrode prepared in this example are shown in Figure 4, in which Figure 4a is the surface SEM image of the electrode. It can be seen from the figure that regular wrinkles are formed on the electrode surface, and Figure 4b is the stretchable electrode surface. Characterized by stretchability, the stretchability of the prepared electrodes exceeds 20%.

The above is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent transformations made by using the description of the present invention and the contents of the accompanying drawings, or directly or indirectly used in other related technical fields, are the same as The theory is included in the patent protection scope of the present invention.

Claims

A method for preparing an ultrathin stretchable film electrode, characterized in that it comprises the following steps:

(1) Preparation of ultra-thin stretchable substrates by liquid surface spreading method:

After mixing dimethylsiloxane and crosslinking agent, drop it on the surface of the water phase to obtain a spread film, and obtain a polydimethylsiloxane film after heating and pre-curing; transfer the polydimethylsiloxane film Get the electrode base on the ring substrate;

(2) Preparation of ultra-thin stretchable film electrodes by thermal evaporation method:

Adsorbing the electrode substrate obtained in step (1) on a silicon wafer, and evaporating a metal conductive layer on the polydimethylsiloxane film on the electrode substrate to obtain the electrode.
The preparation method according to claim 1, characterized in that, in step (1), the thickness of the polydimethylsiloxane film is 3 μm to 30 μm.
The preparation method according to claim 1, characterized in that, in step (1), the curing temperature of the pre-curing is 40-120°C, and the curing time is preferably 45-120 min;

Preferably, in step (1), the pre-curing is curing at 60°C for 60 minutes.
The preparation method according to claim 1, characterized in that, in step (1), the Young's modulus of the pre-cured polydimethylsiloxane film does not exceed 700 kPa.
The preparation method according to claim 1, characterized in that, in step (1), the mass ratio of the dimethylsiloxane to the crosslinking agent is 5-15:1.
The preparation method according to claim 1, characterized in that, in step (2), the evaporation rate of the evaporation is 0.1-10 Å/s, preferably 0.5 Å/s.
The preparation method according to claim 1, characterized in that, in step (2), the thickness of the vapor-deposited metal conductive layer is 100 nm to 300 nm, preferably 150 nm.
The preparation method according to claim 1, characterized in that, in step (2), the metal of the metal conductive layer is selected from any one of gold, silver, platinum, titanium, iridium and platinum-iridium alloy.
The preparation method according to claim 1, characterized in that in step (2), a sacrificial layer is provided on the silicon wafer, and the sacrificial layer is prepared by a spin coating method.
The ultra-thin stretchable film electrode obtained according to the preparation method described in any one of claims 1-9.