WO2023197130A1 - Multi-channel high-density ultra-narrow stretchable microelectrode, method for preparing same, and use thereof - Google Patents

Abstract

Disclosed are a multi-channel high-density ultra-narrow stretchable microelectrode, a method for preparing same, and use thereof. The method comprises the following steps: providing a flexible substrate comprising a stretchable area and a rigid area; stretching the stretchable area; sputtering a pattern on the stretched flexible substrate by means of a mask to prepare a conductive layer; releasing the stretchable area to allow a retraction thereof; and packaging to give the multi-channel high-density ultra-narrow stretchable microelectrode. According to the method provided by the present invention, the micro-crack gold film technology is combined with the pre-stretching of the flexible substrate, such that the electrode can be prepared into a multi-channel high-density ultra-narrow electrode, and the good stretching performance and cycling stability of the electrode can be ensured.

Description

A multi-channel high-density ultra-narrow stretchable microelectrode and its preparation method and application Technical field

The present invention relates to the technical field of flexible electrodes, and in particular to a multi-channel, high-density, ultra-narrow stretchable microelectrode and its preparation method and application.

Background technique

In the prior art, flexible electrodes are prepared from flexible substrates and stretchable conductive materials (such as gold films). Among them, the preparation process of thin-film flexible stretchable electrodes has gradually matured, and large-scale production and patterning have been achieved (Advanced Materials, 2019, 31(35):1901360.). The current flexible and stretchable electrode arrays are limited by the characteristics of the manufacturing process and materials. The sensing points and width of the electrodes cannot be soft and stretchable in a small size, which hinders the development of higher-density flexible electrode arrays. Therefore, how to prepare high-density flexible microelectrodes to achieve precise signal collection from tiny objects is still a problem.

Multi-channel high-density ultra-narrow stretchable microelectrodes can achieve physiological electrical signal collection and electrical stimulation at higher spatial resolution. However, the smaller the size of the stretchable electrode, its stretchability and impedance will decrease. The more unstable it is. This results in the current inability to stably achieve the preparation of stretchable microelectrodes with a size below 20 microns. In addition, the realization of patterning and packaging solutions in the preparation process of stretchable microelectrodes mainly rely on photolithography technology. Photolithography technology does not have the simplicity of one-piece molding by physical mask method, and the stretchable electrodes prepared by it are gradually The reduction in size, increase in cost, and deterioration in performance have affected the development of stretchable microelectrodes to a certain extent.

For example, Klas Tybrandt and others used gold-coated titanium dioxide nanowires embedded in a silica gel matrix to produce multi-channel high-density flexible stretchable electrodes with a minimum width of 30 μm and a stretch rate of 30%, and conducted long-term measurements of neural signals in the cerebral cortex of mice. Monitoring (Advanced Materials, 2018, 30(15):1706520.), this method has the disadvantages of cumbersome preparation process and high cost. Yuxin Liu et al. used soft conductive hydrogel and photolithography to prepare an electrode with a width of 20 μm and a stretch rate of 20%. Its advantages are obvious in low-voltage stimulation of the sciatic nerve in living mice, which is currently possible. The minimum limit of flexible stretchable electrode size (Nature biomedical engineering, 2019, 3(1):58-68.). Although photolithography can minimize the size of electrode patterns, its operation is complex, requires high substrate and conductive materials, and may cause a certain degree of damage to the electrodes. The process conditions are harsh, the packaging process is relatively complex, and the cost is high. , rendering it impractical for practical application. As the demand for miniaturization of soft electronics increases, flexible electrodes need to be more precise and miniaturized in recording and stimulation. Therefore, developing new flexible electrodes using material properties is a reliable strategy to achieve this goal.

Contents of the invention

In view of the above technical problems, the present invention provides a multi-channel high-density ultra-narrow stretchable microelectrode and its preparation method and application. The present invention uses the pre-stretched size enlargement method to enlarge the flexible substrate. On the enlarged flexible substrate, a conductive layer is prepared by pattern sputtering, and then the flexible substrate is released to restore its shape. After packaging, a multi-channel high-density layer can be obtained. The number of channels, density, sensing point distribution and width of a single channel of ultra-narrow stretchable microelectrodes can be changed according to different needs. The stretchable microelectrode provided by the present invention can reach the narrowest width of three electrode channels of 10 microns, and can still maintain stable tensile conductivity of more than 100% and tensile stability for thousands of cycles.

In order to achieve the above objects, the technical solutions adopted by the present invention are:

On the one hand, the present invention provides a method for preparing multi-channel, high-density, ultra-narrow stretchable microelectrodes, which includes the following steps:

Provide a flexible substrate; the flexible substrate includes a stretching zone and a fixed zone; stretch and amplify the stretching zone; perform pattern sputtering on the stretched and amplified flexible substrate through a mask to prepare a conductive layer; release The stretching zone causes it to retract; after packaging, the multi-channel high-density ultra-narrow stretchable microelectrode is obtained.

As a preferred embodiment, during the stretching and enlarging process of the stretching zone, the fixing zone is fixed by adhesion. In some specific embodiments, the fixing area is pasted and fixed with adhesive tape, which can ensure that during the stretching process, the stretching area deforms but the fixing area does not deform.

In the technical solution of the present invention, during the stretching and amplification process in the stretching zone, the transverse or longitudinal amplification rate is determined by the shape design of the electrode and the thickness and tensile properties of the flexible substrate. In order to prevent fracture, the magnification ratio does not exceed the stretch at break of the flexible substrate.

As a preferred embodiment, the pattern sputtering of the flexible substrate after stretching and amplification processing through a mask is pattern sputtering on the sticky surface of the flexible substrate after stretching and amplification processing;

Preferably, the pattern sputtering of the flexible substrate after stretching and amplification through a mask is pattern sputtering on the flat surface of the flexible substrate after stretching and amplification; a mask is required in the pattern sputtering process, so It is necessary to ensure that the sputtering surface of the flexible substrate is flat, and the conductive layer prepared by sputtering on the flat surface has better performance;

Preferably, the pattern sputtering is magnetron sputtering;

Preferably, the conductive layer is a gold conductive layer.

As a preferred embodiment, in the pattern sputtering of the stretch-amplified flexible substrate through a mask, the size of the mask matches the size of the stretch-amplified flexible substrate.

As a preferred embodiment, it also includes the step of encapsulating the conductive layer. The step of encapsulating the conductive layer is: exposing the electrode circuit area in the conductive layer that needs to be encapsulated, and encapsulating it;

Preferably, the conductive layer encapsulation is a hydrogenated styrene-butadiene block copolymer (SEBS) film encapsulation;

In some specific embodiments, the specific operation of the conductive layer encapsulation is: shielding the parts of the electrode circuits of the conductive layer that do not need to be encapsulated to expose the electrode circuit areas that need to be encapsulated: for example, using thin copper wires to block the sensing area , use cardboard to block the area connected to the printed circuit board (PCB); attach a hydrogenated styrene-butadiene block copolymer (SEBS) film to the conductive layer, remove the blockage, and complete the conductive layer encapsulation. The conductive layer is encapsulated with a hydrogenated styrene-butadiene block copolymer (SEBS) film. After the stretch zone is released, the hydrogenated styrene-butadiene block copolymer (SEBS) film will retract with the flexible substrate. While shrinking, the mutual adhesion of hydrogenated styrene-butadiene block copolymer (SEBS) films prevents them from falling off.

Wherein, the preparation method of the hydrogenated styrene-butadiene block copolymer (SEBS) film is: adding a toluene solution of the hydrogenated styrene-butadiene block copolymer (SEBS) with a mass fraction of 5 to 15%. Drop it on the water phase liquid surface to obtain a thin film with a thickness of 100~200nm.

As a preferred embodiment, the flexible substrate is a stretchable and resilient flexible substrate with adhesiveness, selected from any one or more elastic polymer materials; preferably hydrogenated styrene-butadiene block Copolymer (SEBS) flexible substrate;

In some specific embodiments, the preparation method of the hydrogenated styrene-butadiene block copolymer (SEBS) flexible substrate is: placing a toluene solution of SEBS with a mass percentage of 5 to 15% on polytetrafluoroethylene In an ethylene (PTFE) mold, a SEBS film with a thickness of about 200 to 300 microns is obtained after air drying. The side of the SEBS film obtained by the above method facing the bottom of the mold is in the form of an inverted mold of the polytetrafluoroethylene (PTFE) mold, which basically does not have Self-adhesive; after the other side is naturally air-dried, it will be in the form of a flat SEBS film with strong self-adhesiveness and mutual adhesion.

In the technical solution of the present invention, a stretchable and resilient flexible substrate with viscosity is used. After the stretching zone is released, it shrinks, and the conductive layer deforms accordingly to form an electrode structure with a specific pattern. According to the structure of the mask and The multiple of tensile deformation can control the structure of the pattern.

In the technical solution of the present invention, hydrogenated styrene-butadiene block copolymer (SEBS) is used as raw material, toluene is used as a solvent to prepare a flexible substrate, and a hydrogenated styrene-butadiene block with a thickness of 100 to 200 nm is used. The copolymer (SEBS) film encapsulates the conductive layer. After the stretch zone is released, the hydrogenated styrene-butadiene block copolymer (SEBS) film shrinks and does not fall off due to the self-adhesiveness of SEBS.

As a preferred embodiment, the package uses anisotropic conductive tape to connect the gold finger portions of the electrodes to the channels on the printed circuit board in one-to-one correspondence to form a stable conductive path.

In the technical solution of the present invention, the high density means that the density of sensing points is greater than or equal to 1/mm ² ; the ultra-narrow means that the channel width of the electrode is less than or equal to 50 microns.

In another aspect, the present invention provides multi-channel, high-density, ultra-narrow stretchable microelectrodes obtained by the above preparation method.

In another aspect, the present invention provides an application of the above-mentioned ultra-narrow stretchable microelectrode in preparing a device for collecting physiological electrical signals or in collecting physiological electrical signals.

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

The present invention utilizes the soft characteristics of the flexible substrate, introduces the pre-stretching behavior of the flexible polymer into the preparation process of the electrode, prepares the electrode pattern on the size-enlarged substrate and then releases and retracts it to ultimately realize the miniaturization and pullability of the electrode. Stretchability. The present invention finally prepares multi-channel high-density ultra-narrow stretchable microelectrodes by stretching to change the size of the flexible substrate, which is suitable for manual operation and mechanized mass production. Through the physiological electrical signal collection experiment, the multi-channel high-density ultra-narrow stretchable microelectrode prepared by the present invention not only successfully collected the physiological electrical signals of cells, but also realized the collection of myoelectric signals outside the subcutaneous muscle membrane of mice. And the data collected has high reliability. At the same time, the multi-channel high-density ultra-narrow stretchable microelectrodes provided by the present invention performed a series of electrical stimulation on nerve cells and mouse tissues, successfully achieving simultaneous stimulation and recording between different channels, that is, stimulating some channels. signal, and other channels collect stimulation signals. The electrode provided by the present invention provides new ideas for the preparation of flexible and stretchable electrodes, whether it is a change in electrode pattern style or electrode size.

Compared with the existing technology, the present invention has the following advantages:

(1) The preparation method provided by the present invention combines the microcracked gold film technology and the pre-stretched size enlargement of the flexible substrate. It can not only prepare the electrode into a multi-channel high-density ultra-narrow electrode (width 10 microns), but also ensures good electrode performance. Tensile properties and cyclic stability;

(2) The preparation method provided by the present invention utilizes the size enlargement of the flexible substrate so that the conductive layer encapsulation layer after enlargement and release will not slip or shift, and the sensing point area of the electrode will be clearly exposed without being blocked, and can adapt to the release. The change in size reduces the difficulty of overexposure of the sensing point area during the preparation of ultra-narrow electrodes, thereby achieving an ultra-narrow electrode path (width 10 microns), and the area of the exposed sensing point is also of the same size level (10 microns × 10 microns);

(3) The present invention is simpler in the preparation process, has a high success rate, and has higher electrode efficiency. The present invention does not require the participation of photolithography equipment, and accordingly reduces the preparation cost.

Description of the drawings

Figure 1 is a flow chart for the preparation of multi-channel, high-density, ultra-narrow stretchable microelectrodes in Example 1 of the present invention.

Figure 2 is a physical diagram of a 32-channel high-density ultra-narrow stretchable microelectrode prepared in Example 1 of the present invention.

Detailed ways

The following embodiments are only some of the embodiments of the present invention, rather than all of the embodiments. Therefore, the detailed description of the embodiments of the invention provided below is not intended to limit the scope of the claimed invention but rather to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without any creative work fall within the protection scope of the present invention.

In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following examples are all conventional methods in the art unless otherwise specified.

Example 1:

In this embodiment, a 32-channel high-density ultra-narrow stretchable microelectrode is prepared. The preparation method is shown in Figure 1, which specifically includes the following steps:

(1) Prepare a flexible substrate: Pour a 15% mass percent SEBS toluene solution into a square polytetrafluoroethylene (PTFE) mold, and air-dry to obtain a SEBS film with a thickness of approximately 300 microns. The SEBS film faces the bottom of the mold. One side has the inverted form of the mold, which is in a mist-like and incompletely flat state, and is recorded as the back side; the other side is in a flat form after natural air drying, with strong viscosity and self-adhesive properties, and is recorded as the front side;

(2) Pre-stretching and fixing of the flexible substrate: Use tape to stick and fix the back of the flexible substrate, which is recorded as the fixed area; pre-stretch the flexible substrate, and the fixed area will not deform during the stretching process, but the stretched deformed area will The size is stretched from the initial 1 unit length × 1 unit length to 3 unit length × 2 unit length, and the deformed flexible base is fixed to prevent its shape from shrinking;

(3) Preparing the conductive layer: Place a mask matching the size of the enlarged flexible substrate on the flat side of the stretched and amplified flexible substrate, and prepare a gold conductive layer with a special pattern design by magnetron sputtering;

(4) Conductive layer encapsulation and release: This embodiment uses hydrogenated styrene-butadiene block copolymer (SEBS) film as the encapsulation layer material of the conductive layer; hydrogenated styrene-butadiene with a mass fraction of 5% Drop the toluene solution of the block copolymer (SEBS) on the water to obtain a film with a thickness of 100nm; use copper wire to block the sensing area in the electrode circuit, and use cardboard to block the part of the electrode circuit connected to the printed circuit board (PCB). Attach the SEBS film to the conductive layer. After a few minutes, remove the shielding copper wire and cardboard to complete the encapsulation of the conductive layer. After that, release the fixation in step (2), the deformation area of the flexible substrate retracts, and the SEBS film is encapsulated. It shrinks accordingly and does not fall off due to its stickiness;

(5) Electrode packaging: Use heterogonal conductive tape to connect the gold finger part of the electrode to the channel on the printed circuit board in one-to-one correspondence to form a stable conductive path.

The actual picture of the 32-channel microelectrode prepared in this embodiment is shown in Figure 2. The density of sensing points is 3/ ^0.01mm2 ; the channel width is 10 microns.

In this embodiment, the prepared 32-channel microelectrode was used to conduct a physiological electrical signal collection experiment. Not only the physiological electrical signals of cells were successfully collected, but also the electromyographic signals outside the subcutaneous muscle membrane of mice were collected, and all results were obtained. got reliable data. In this embodiment, the prepared 32-channel microelectrode was used to perform a series of electrical stimulation on nerve cells and mouse tissue, and successfully realized simultaneous stimulation and recording between different channels, that is, some channels gave stimulation signals, and other channels collected stimulation signals.

The above are only the preferred embodiments of the present invention. It should be pointed out that those of ordinary skill in the art can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications can also be made. should be regarded as the protection scope of the present invention.

Claims (14)

1. A method for preparing multi-channel high-density ultra-narrow stretchable microelectrodes, which is characterized by including the following steps:

   Provide a flexible substrate; the flexible substrate includes a stretching zone and a fixed zone; stretch and amplify the stretching zone; perform pattern sputtering on the stretched and amplified flexible substrate through a mask to prepare a conductive layer; release The stretching zone causes it to retract; after packaging, the multi-channel high-density ultra-narrow stretchable microelectrode is obtained.
2. The preparation method according to claim 1, characterized in that, during the stretching and amplification process of the stretching zone, the fixed zone is fixed by pasting.
3. The preparation method according to claim 1, characterized in that, during the stretching and amplification process in the stretching zone, the transverse or longitudinal amplification rate does not exceed the breaking elongation rate of the flexible substrate.
4. The preparation method according to claim 1, characterized in that, performing pattern sputtering on the flexible substrate after stretching and amplification processing through a mask is pattern sputtering on the sticky surface of the flexible substrate after stretching and amplification processing. shoot.
5. The preparation method according to claim 4, wherein the pattern sputtering of the flexible substrate after stretching and amplification through a mask is pattern sputtering on the flat surface of the flexible substrate after stretching and amplification. .
6. The preparation method according to claim 1, characterized in that the pattern sputtering is magnetron sputtering.
7. The preparation method according to claim 1, wherein the conductive layer is a gold conductive layer.
8. The preparation method according to claim 1, characterized in that, in the pattern sputtering of the flexible substrate after stretching and amplification through a mask, the size of the mask is consistent with the size of the flexible substrate after stretching and amplification. The dimensions of the substrate match.
9. The preparation method according to claim 1, further comprising the step of encapsulating the conductive layer, which step is: exposing the electrode circuit area in the conductive layer that needs to be encapsulated, and encapsulating it.
10. The preparation method according to claim 9, characterized in that the conductive layer is encapsulated with a hydrogenated styrene-butadiene block copolymer (SEBS) film.
11. The preparation method according to claim 1, characterized in that the flexible substrate is a stretchable and resilient flexible substrate with viscosity, selected from any one or more types of elastic polymer materials; preferably hydrogenated Styrene-butadiene block copolymer flexible substrate.
12. The preparation method according to claim 1, characterized in that the packaging is to use anisotropic conductive tape to connect the gold finger part of the electrode to the channel on the printed circuit board in a one-to-one correspondence to form a stable conductive path.
13. Multi-channel high-density ultra-narrow stretchable microelectrode obtained by the preparation method of any one of claims 1-12.
14. The application of the ultra-narrow stretchable microelectrode according to claim 13 in preparing a device for collecting physiological electrical signals or in collecting physiological electrical signals.

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