A high viscosity silicone rubber electrode material and a method for preparing the same

Abstract

The application belongs to the technical field of biological electrode materials, and particularly relates to a high-viscosity silicon rubber electrode material and a preparation method thereof. The application obtains a silica gel mixture by pre-polymerizing and dispersing tetraethenylcyclotetrasilane, dithiothreitol, benzoin dimethyl ether, vinyl-terminated polydimethylsiloxane and boric acid under a nitrogen atmosphere; obtains hyperbranched crosslinked silane by ultraviolet irradiation, and the hyperbranched crosslinked silane is denoted as PDMS-V; then, a conductive filler dispersion liquid is uniformly coated on the PDMS-V to obtain a conductive composite material with a conductive network on the surface. The method is simple and efficient, only one step is needed for synthesis, and the obtained material has biocompatibility. The material has high adhesion and universality to all biological interfaces, is deformable, can be closely attached to biological surfaces of different shapes, and has high adhesion in a body fluid environment due to the hydrophobicity of the main chain and the excess hydrogen bonds in the system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of biological electrode materials, and particularly relates to a silicone rubber electrode material and a preparation method thereof. BACKGROUND

[0002] The neural activity and muscle movement of a living body are accompanied by very weak current and potential changes, i.e. bioelectricity. Bioelectricity can provide important information of the living body, which will help doctors diagnose the condition of patients. Electrodes are key devices for collecting electrical signals, such as electrocardiogram (ECG) or electromyogram (EMG). Commercial electrodes, such as rigid electrodes, usually need to penetrate tissues with damage to measure bioelectricity. Compared with rigid facial interfacial electrodes, flexible electrodes have the characteristics of softness and stretchability, have been widely used in wearable devices, can be applied to the detection of different parts of the human body, and greatly reduce the pain in clinical treatment. In recent years, several substrates have been used in the research of soft interfacial electrodes, such as polydimethylsiloxane (PDMS), polyimide (PI), polyethylene terephthalate (PET), etc. Compared with PI and PET, the PDMS substrate can easily form a conformal interface with human skin. However, due to the stable chemical properties of PDMS itself, the interfacial adhesion between PDMS and tissues is poor, which often leads to poor performance of the electrode during long-term monitoring or body movement. In order to ensure stable and reliable signal measurement, two methods are currently mainly adopted, one is through physical method, i.e. constructing micro-nano structure on the surface, increasing the specific surface area to improve adhesion, which can improve the adhesion between the electrode and different surfaces, but the time-consuming is long and the cost of micro-nano processing is high. The other is through chemical method, introducing some adhesion groups, but the modification time of the currently reported PDMS usually needs to be more than 12 hours and the modification step needs to be carried out in a solution. In addition, the adhesion of this type of electrode will be greatly reduced in the body fluid environment (such as sweating) and under the skin. Therefore, it is an urgent problem to develop a preparation method for rapidly preparing a silicone electrode material with universal high adhesion. SUMMARY

[0003] The purpose of the present application is to overcome the shortcomings of the existing silicone rubber electrode material, and to provide a silicone rubber electrode material and a preparation method thereof, which have the advantages of fast preparation speed, good biocompatibility and strong adhesion.

[0004] The preparation method of the silicone rubber electrode material provided by the present application has the following specific steps:

[0005] (1) Put 3-10 mg of tetra-vinyl cyclo-tetrasilane, 50-300 mg of dithiothreitol (DTT), 5-100 mg of benzoin dimethyl ether, 1-10 g of vinyl-terminated polydimethylsiloxane, and 50-200 mg of boric acid into a reaction bottle, introduce nitrogen, fully stir, and make the prepolymer completely dispersed to obtain a silica gel mixture;

[0006] (2) After the silica gel mixture obtained in step (1) is irradiated with ultraviolet light for 12-15 min while stirring is maintained, a hyperbranched crosslinked silane is obtained, denoted as PDMS-V;

[0007] (3) The conductive filler dispersion liquid is uniformly coated on the PDMS-V obtained in step (2) to obtain a conductive composite material with a conductive network on the surface; or the conductive filler is fully mixed with the elastomer, and then solidified to obtain an isotropic conductive composite material, which is the flexible electrode material.

[0008] In the present application, the volume of the reaction bottle in step (1) is 10-100 mL.

[0009] In the present application, the molecular weight of the vinyl-terminated polydimethylsiloxane in step (1) is 4 kg / mol-50 kg / mol.

[0010] In the present application, the conductive filler in step (3) is any one of metal particles, metal wires, metal sheets, carbon nanomaterials (including carbon black, carbon nanotubes, graphene or reduced graphene oxide), conductive polymers or ceramic materials, and the dispersion liquid is any one of deionized water, ethanol, n-hexane or tetrahydrofuran.

[0011] In the present application, the substrate of the flexible electrode material is any one of a silicon wafer or a glass plate.

[0012] In the present application, the synchronous reaction of tetra-vinyltetrasilane and backbone vinyl polydimethylsiloxane with dithiothreitol can greatly improve the synthesis efficiency of the polymer, shorten the reaction time, and at the same time increase the content of hydroxyl groups in the system, thereby resulting in good tissue adhesion of the electrode prepared by using the polymer as the flexible substrate to the skin, skull and the like.

[0013] Compared with the existing method for preparing high-adhesion electrode material, the present application has the following advantages:

[0014] 1. The present application provides a method for preparing a high-adhesion silicone rubber electrode material, which is the fastest so far. The synthesis reaction of the flexible substrate involved is efficient and simple, and at most only 15 min is needed, and the material has biocompatibility.

[0015] 2. The silicone rubber electrode material provided by the present application has high adhesion under water due to the hydrophobicity of the main chain and a large number of hydrogen bonds in the system, i.e. high adhesion and universality to all biological interfaces, and the material is deformable and can be closely attached to biological surfaces of different shapes.

[0016] 3. The electrode material prepared by the method has high adhesion in a body fluid environment, and can be used not only for epidermal electronics, but also for detection of in-vivo electrophysiological signals. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a schematic diagram of the network structure of the PDMS-V flexible material.

[0018] Figure 2 is the infrared spectrum of tetra-vinyl cyclo-tetra-silane, vinyl-terminated polydimethylsiloxane, dithiothreitol, pre-polymer and final product PDMS-V.

[0019] Figure 3 is a photo of the flexible material prepared in Example 1, and the adhesion strength between different biological tissues.

[0020] Figure 4 is the material used in Example 1 prepared into an electrode, which is attached to the surface of human skin to measure the impedance.

[0021] Figure 5 is the flexible electrode obtained in Example 1 attached to the forearm and can detect accurate electrocardiogram signals, attached to the forehead to detect electroencephalogram and blinking signals. DETAILED DESCRIPTION

[0022] The above scheme is further described in conjunction with specific examples. It should be understood that these examples are used to illustrate the present application and are not intended to limit the scope of the present application. The implementation conditions used in the examples can be further adjusted according to the specific conditions of the manufacturer. The implementation conditions not specified are usually conventional experimental conditions.

[0023] Example 1

[0024] (1) Take 3 mg of tetramethyl tetra-vinyl cyclo-tetra-siloxane, 12 mg of dithiothreitol, 32 mg of benzoin dimethyl ether, 5 g of vinyl-terminated polydimethylsiloxane, and 120 mg of boric acid and add them to a reaction bottle, introduce nitrogen, and fully stir to disperse the pre-polymer to obtain a silica gel mixture;

[0025] (2) After ultraviolet irradiation of the silica gel mixture obtained in step (1) for 15 min while maintaining stirring, PDMS-V is obtained;

[0026] (3) Uniformly coat the conductive filler solution on the PDMS-V obtained in step (2) to obtain a conductive composite material with a conductive network on the surface; or fully mix the conductive network with the elastomer, and solidify to obtain an isotropic conductive composite material, which is a self-repairing electrode material.

[0027] Example 2: The same as Example 1, the molecular weight of the polydimethylsiloxane in step (1) is 8 kg / mol.

[0028] Example 3: The stoichiometric ratio of boric acid to polydimethylsiloxane in step (1) is 1.

[0029] Example 4: The UV irradiation time in step (2) is 3h.

[0030] Example 5: The stoichiometric ratio of boric acid and PDMS-OH in step (3) is 1.

[0031] Example 6: The same as example 1, but the stoichiometric ratio of boric acid and vinyl-terminated polydimethylsiloxane in step (3) is 2.

[0032] Example 7: The same as example 1, but the conductive network solution in step (3) is one-dimensional conductive material such as carbon nanotube.

[0033] Example 8: The same as example 1, but the conductive material in step (3) is replaced by two-dimensional conductive filler such as graphene.

[0034] Figure 1 is a reaction schematic diagram for preparing PDMS-V.

[0035] Figure 2 is the infrared spectrum of tetra-vinyl cyclo-tetra-silane, vinyl-terminated polydimethylsiloxane, dithiothreitol, pre-polymer and final product PDMS-V. As can be seen from the figure, dithiothreitol, tetra-vinyl cyclo-tetra-silane and vinyl PDMS have successfully reacted, cross-linking structure has been generated by using double bond, and a large number of hydroxyl groups have been introduced by dithiothreitol.

[0036] Figure 3 is a photo of the flexible material prepared in example 1, and the adhesion strength with different biological tissues, from which it can be seen that the sample has strong adhesion and universality, and the adhesion can be precisely controlled by cross-linking agent, while the commercial electrode has no adhesion with the tissue.

[0037] Figure 4 is the material used in example 1 prepared into an electrode, which is attached to the surface of human skin to measure impedance, and it can be seen that it has impedance level comparable to that of commercial electrode, but in the case of sweating, the impedance of the flexible electrode is more stable, and the commercial electrode will have certain attenuation and fall off phenomenon during testing.

[0038] Figure 5 is the conductive material obtained in example 1, which is attached to the forearm and can detect accurate electrocardiogram signal, and is attached to the forehead to detect electroencephalogram and blinking signal.

[0039] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and it cannot limit the protection scope of the present application. Any equivalent transformation or modification made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A method for preparing a high-viscosity silicone rubber electrode material, characterized in that, The specific steps are as follows: (1) Add 3 mg of tetravinylcyclotetrasilane, 12 mg of dithiothreitol, 32 mg of benzoin dimethyl ether, 5 g of vinyl-terminated polydimethylsiloxane, and 120 mg of boric acid to a reaction flask, purge with nitrogen, and stir thoroughly to completely disperse the prepolymer and obtain a silica gel mixture. (2) While stirring, the silica gel mixture obtained in step (1) is irradiated with ultraviolet light for 12-15 min to obtain hyperbranched crosslinked silane, denoted as PDMS-V; (3) The conductive filler dispersion is uniformly coated on the PDMS-V obtained in step (2) to obtain a conductive composite material with a conductive network on the surface; or the conductive filler is fully mixed with the PDMS-V obtained in step (2) and then cured to obtain an isotropic conductive composite material, which is a flexible electrode material.

2. The preparation method according to claim 1, characterized in that, The vinyl-terminated polydimethylsiloxane described in step (1) has a molecular weight of 4 kg / mol to 50 kg / mol.

3. The preparation method according to claim 1, characterized in that, The conductive filler mentioned in step (3) is any one of metal particles, metal wires, metal sheets, carbon nanomaterials, conductive polymers, or ceramic materials, and the dispersion solution is any one of deionized water, ethanol, n-hexane, or tetrahydrofuran.

4. A high-viscosity silicone rubber electrode material obtained by the preparation method according to any one of claims 1-3.

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