High-viscosity silicone rubber electrode material and preparation method thereof

Abstract

The invention belongs to the technical field of biological electrode materials, and particularly relates to a high-viscosity silicone rubber electrode material and a preparation method thereof. The preparation method comprises the following steps: pre-polymerizing and dispersing tetravinyl cyclotetrasilane, dithiothreitol, benzoin dimethyl ether, vinyl-terminated polydimethylsiloxane and boric acid in a proper ratio in a nitrogen atmosphere to obtain a silica gel mixture; carrying out ultraviolet light irradiation to obtain hyperbranched cross-linked silane, which is marked as PDMS-V; and uniformly coating PDMS-V with the conductive filler dispersion liquid to obtain the conductive composite material of which the surface is coated with a conductive network. The method is simple and efficient, only one step is needed for synthesis, and the obtained material has biocompatibility, has high adhesion and universality to all biological interfaces, is deformable and can be tightly attached to biological surfaces of different shapes, so that the material is suitable for large-scale popularization and application. Due to the hydrophobicity of a main chain and excessive hydrogen bonds in a system, the material also has high adhesion in a body fluid environment.

Description

Technical Field

[0001] The invention belongs to the technical field of biological electrode materials, and in particular relates to a silicone rubber electrode material and a preparation method thereof. Background Art

[0002] The neural activity and muscle movement of organisms are accompanied by very weak current and potential changes, namely biocurrent. Biocurrent can provide important information about organisms, which will help doctors diagnose patients' conditions. 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 in a damaging way to measure bioelectricity. Compared with rigid inter-facial electrodes, flexible electrodes have soft and stretchable properties and have been widely used in wearable devices. They can be applied to different parts of the human body for detection and greatly reduce pain in clinical treatment. In recent years, several substrates have been used in the study of soft interface electrodes, such as polydimethylsiloxane (PDMS), polyimide (PI), polyethylene terephthalate (PET), etc. Compared with PI and PET, PDMS substrate can easily form a conformal interface with human skin. However, due to the stable chemical properties of PDMS itself and poor interfacial adhesion with tissues, the electrodes often show poor performance during long-term monitoring or body movement. In order to ensure stable and reliable signal measurement, two main methods are currently adopted. One is through physical methods, that is, constructing micro-nano structures on the surface, increasing the specific surface area to improve adhesion, which can improve the adhesion between the electrode and different surfaces, but it is time-consuming and the cost of micro-nano processing is high. The other is through chemical methods to introduce some adhesive groups, but the currently reported PDMS modification time is usually more than 12 hours and the modification step needs to be carried out in the solution. In addition, the adhesion of this type of electrode will be greatly reduced in body fluid environments (such as sweating) and under the skin. Therefore, the development of a preparation method for quickly preparing a universal high-viscosity silicone electrode material is a problem that needs to be solved urgently. Summary of the invention

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

[0004] The preparation method of the silicone rubber electrode material proposed in the present invention comprises the following specific steps:

[0005] (1) Add 3-10 mg of tetravinylcyclotetrasilane, 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, and stir thoroughly to completely disperse the prepolymer to obtain a silica gel mixture;

[0006] (2) while stirring, irradiating the silica gel mixture obtained in step (1) with ultraviolet light for 12-15 minutes to obtain a hyperbranched cross-linked silane, which is denoted as PDMS-V;

[0007] (3) The conductive filler dispersion is evenly 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 and the elastomer are fully mixed and cured to obtain an isotropic conductive composite material, which is a flexible electrode material.

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

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

[0010] In the present invention, 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) or conductive polymers or ceramic materials, and the dispersion liquid is any one of deionized water, ethanol, n-hexane or tetrahydrofuran.

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

[0012] The present invention particularly adopts tetravinylcyclotetrasilane and main chain vinyl polydimethylsiloxane to react synchronously with dithiothreitol, which can greatly improve the efficiency of polymer synthesis, shorten the reaction time, and at the same time increase the content of hydroxyl groups in the system, thereby resulting in the electrode prepared with the polymer as a flexible substrate having good tissue adhesion to the skin, skull, etc.

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

[0014] 1. The present invention provides a method for preparing a highly viscous silicone rubber electrode material which is the fastest so far. The synthetic reaction of the flexible substrate involved is efficient and simple, requiring only 15 minutes at most, and the material is biocompatible;

[0015] 2. The hydrophobicity of the main chain of the silicone rubber electrode material provided by the present invention and the large number of hydrogen bonds in the system enable the material to have high adhesion underwater, that is, it has high adhesion and universality to all biological interfaces. At the same time, the material is deformable and can be closely attached to biological surfaces of different shapes;

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

[0017] Figure 1 This is a schematic diagram of the network structure for preparing PDMS-V flexible materials.

[0018] Figure 2 It is the infrared spectra of tetravinylcyclotetrasilane, vinyl terminated polydimethylsiloxane, dithiothreitol, prepolymer and the final product PDMS-V.

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

[0020] Figure 4 The material used in Example 1 is used to prepare electrodes, which are then attached to the surface of human skin to measure impedance.

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

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

[0023] Example 1

[0024] (1) Weigh 3 mg of tetramethyltetravinylcyclotetrasiloxane, 12 mg of dithiothreitol, 32 mg of benzoin dimethyl ether, 5 g of vinyl-terminated polydimethylsiloxane, and 120 mg of boric acid into a reaction bottle, introduce nitrogen, and stir thoroughly to completely disperse the prepolymer to obtain a silica gel mixture;

[0025] (2) While stirring, irradiate the silica gel mixture obtained in step (1) with ultraviolet light for 15 minutes to obtain PDMS-V;

[0026] (3) The conductive filler solution is evenly 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 network and the elastomer are fully mixed and cured to obtain an isotropic conductive composite material, which is a self-healing electrode material.

[0027] Example 2: 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 ultraviolet light irradiation time in step (2) is 3 hours.

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

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

[0032] Example 7: Same as Example 1, but the conductive network solution in step (3) is a one-dimensional conductive material such as carbon nanotubes.

[0033] Example 8: Same as Example 1, but the conductive material in step (3) is replaced with two-dimensional conductive fillers such as graphene.

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

[0035] Figure 2 This is the infrared spectrum of tetravinylcyclotetrasilane, vinyl-terminated polydimethylsiloxane, dithiothreitol, prepolymer and the final product PDMS-V. It can be seen from the figure that dithiothreitol, tetravinylcyclotetrasilane and vinyl PDMS successfully reacted to produce a cross-linked structure using double bonds, and dithiothreitol introduced a large number of hydroxyl groups.

[0036] Figure 3 This is a photo of the flexible material prepared in Example 1, and the adhesion strength between it and different biological tissues. It can be seen that the sample has strong adhesion and universality. At the same time, this adhesion can be precisely controlled by cross-linking agents, while there is no adhesion between commercial electrodes and tissues.

[0037] Figure 4 The material used in Example 1 was used to prepare an electrode, and the electrode was attached to the surface of human skin to measure the impedance. It can be seen that the electrode has an impedance level comparable to that of the commercial electrode. However, when sweating, the impedance of the flexible electrode is more stable, while the commercial electrode has a certain attenuation and falls off during testing.

[0038] Figure 5 The conductive material test patch obtained in Example 1 can detect accurate electrocardiogram signals when applied to the forearm, and can detect brain waves and blinking signals when applied to the forehead.

[0039] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high-viscosity silicone rubber electrode material, characterized in that: The specific steps are as follows: (1) Add 3-10 mg of tetravinylcyclotetrasilane, 50-300 mg of dithiothreitol, 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, and stir thoroughly to completely disperse the prepolymer to obtain a silica gel mixture; (2) while stirring, irradiating the silica gel mixture obtained in step (1) with ultraviolet light for 12 to 15 minutes to obtain a hyperbranched cross-linked silane, which is denoted as PDMS-V; (3) The conductive filler dispersion is evenly 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 and the elastomer are fully mixed 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 molecular weight of the vinyl-terminated polydimethylsiloxane in step (1) is 4kg / mol-50kg / mol.

3. The preparation method according to claim 1, characterized in that: The conductive filler in step (3) is any one of metal particles, metal wires, metal sheets, carbon nanomaterials, conductive polymers, or ceramic materials, and the dispersion liquid 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 to 3.

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