Liquid metal-based metal-coated eeg dry electrode and preparation method and application thereof

Abstract

The application belongs to the field of non-invasive brain-computer interface, and particularly relates to a liquid metal-based metal-coated dry electroencephalogram electrode, a preparation method and application thereof, which is composed of a liquid metal dry electrode base and a flexible metal coating layer with conductivity completely covering the outer surface of the liquid metal dry electrode base, and the melting temperature of the liquid metal dry electrode base is between room temperature and body temperature. Compared with the prior art, the application solves the problems that the excellent flexibility and high conductivity of the dry electrode in the prior art are difficult to be considered, the liquid metal is difficult to be packaged under a complex electrode shape, and the precision in the preparation process is uncontrollable. The electroencephalogram dry electrode of the scheme realizes the combination of flexibility and metal-level conductivity, significantly reduces the scalp contact impedance, and the preparation method adopted is controllable in precision.

Description

Technical Field

[0001] This invention belongs to the field of non-invasive brain-computer interfaces, specifically relating to a metal-coated EEG dry electrode based on liquid metal, its preparation method, and its application. Background Technology

[0002] Electroencephalography (EEG), as the most commonly used non-invasive brain-computer interface, has wide applications in medical monitoring, attention monitoring, sleep monitoring, neurological recovery, and prosthetic control. Currently, the most commonly used electrodes in the industry are wet electrodes (usually made of silver / silver chloride, used in conjunction with conductive gel), which offer good signal quality. However, during prolonged monitoring, the contact impedance between the electrode and the scalp increases due to the evaporation of the conductive gel and absorption by the scalp, leading to a significant decrease in signal quality or even signal disconnection. Furthermore, the conductive gel can cause discomfort to the subject. In addition, the placement of the conductive gel requires professional personnel, and it needs to be cleaned after testing, thus limiting the innovative application and widespread adoption of EEG technology by the general public.

[0003] Dry electrodes do not require conductive gel, aligning with the future development trend of wearable and long-term monitoring EEG devices. However, dry electrodes are often made of rigid materials (such as stainless steel, tin, and gold-plated copper), resulting in a significant modulus difference between them and the scalp. This prevents them from forming good conformal contact with the scalp, leading to high electrode-scalp contact impedance and significant motion interference, resulting in a low signal-to-noise ratio. In this context, flexible electrodes, with a more similar modulus to the scalp, can conform to the scalp's surface contours, making them an effective method to reduce contact impedance and improve wearing comfort. To improve flexibility, existing dry electrode technologies include conductive composite material electrodes (combining conductive fillers with a flexible polymer substrate) and metal-coated electrodes based on flexible polymer substrates. For example, the array-type flexible EEG dry electrode disclosed in Chinese patent application CN102579041A sputters a conductive metal film onto the surface of a flexible dry electrode made of polymer material. However, these electrodes still cannot perfectly balance high conductivity and flexibility, facing a trade-off between excellent flexibility and intrinsically high electrode conductivity.

[0004] Liquid metals, such as gallium and gallium-based alloys, possess high electrical conductivity, a room-temperature melting point, and good fluidity, making them ideal materials for achieving flexibility and high conductivity. However, direct contact between gallium-indium alloys and skin can lead to skin residue, failing to meet biocompatibility and reusability requirements. Therefore, encapsulation of liquid metals is necessary to meet these requirements.

[0005] For example, Chinese patent application CN113397551A describes a flexible patch electrode prepared by infiltrating liquid metal into cowhide leather and then coating it with silver paste. However, this patch electrode cannot collect signals from areas covered by hair. Another example is the liquid metal-based neural electrode encapsulation structure provided in Chinese patent application CN121421544A, which includes a liquid metal wire, a low-melting-point metal encapsulation layer, a functional coating, and an insulating shell. The low-melting-point metal encapsulation layer works in conjunction with the insulating shell, encapsulating the liquid metal wire within the insulating shell. The functional coating covers the low-melting-point metal encapsulation layer. However, due to the drawback of the flexible insulating shell blocking electrical signal conduction between the scalp and the liquid metal, the neural electrode encapsulation structure provided by this patent is unsuitable for EEG dry electrode applications that require contact with the scalp to collect bioelectrical signals. Summary of the Invention

[0006] The purpose of this invention is to provide a liquid metal-coated EEG dry electrode, its preparation method, and its application, to solve the problems in existing technologies such as the difficulty in achieving both flexibility and high conductivity in dry electrodes, the challenge of encapsulating liquid metal in complex electrode shapes, and the lack of control over the precision of the preparation process. The EEG dry electrode provided by this invention achieves both excellent flexibility and metallic conductivity, and significantly reduces scalp contact resistance.

[0007] The objective of this invention is achieved through the following technical solution: The present invention found through research that the main difficulties in encapsulating liquid metal in the context of EEG dry electrodes are: (1) the encapsulation layer needs to have good encapsulation ability of liquid metal, and also needs to take into account excellent flexibility and high conductivity. For example, although polymer materials have excellent flexibility, they do not have conductivity; (2) the low melting point of liquid metal (e.g., the melting point of gallium is 29.8 °C) limits the temperature range for the preparation of the encapsulation layer; (3) the preparation of encapsulation layers with complex shapes poses challenges to the process, resulting in uncontrollable preparation accuracy.

[0008] Based on this, in a first aspect, the present invention provides a metal-coated EEG dry electrode based on liquid metal, comprising a liquid metal dry electrode substrate and a conductive micro-nano-scale flexible metal coating layer that completely covers the outer surface of the liquid metal dry electrode substrate, wherein the melting temperature of the liquid metal dry electrode substrate is between room temperature and body temperature.

[0009] Furthermore, the flexible metal cladding layer is made of one or more of gold, silver, silver / silver chloride, copper, tin, stainless steel, platinum, cobalt, palladium, and nickel, and its thickness is 5~10 μm. For example, it can be 5μm, 8μm, 10μm, etc.

[0010] In a second aspect, the present invention also provides a method for preparing a metal-coated EEG dry electrode based on liquid metal, comprising the following steps: S1: After melting liquid metal, it is poured into a casting mold with a set cavity, and after solidification, a liquid metal dry electrode substrate is obtained; S2: The flexible metal coating layer is deposited on the outer surface of the liquid metal dry electrode substrate by electroplating and / or chemical plating, and then cleaned and dried to obtain the metal-coated EEG dry electrode.

[0011] In a third aspect, the present invention provides the application of metal-coated EEG dry electrodes based on liquid metal in the fabrication of non-invasive brain-computer interface devices.

[0012] Furthermore, in the non-invasive brain-computer interface device, the metal-coated EEG dry electrode is configured to be placed at the Fpz or Oz point for signal acquisition.

[0013] The working principle of this invention is as follows: Gallium and gallium-based alloys, among other liquid metals, possess unique properties such as room-temperature melting points, high conductivity, and fluidity, but they face challenges in encapsulation. While metals like silver and gold exhibit excellent conductivity, making them suitable as interface layers in contact with the scalp, their high modulus results in extremely stiff electrodes when used as substrate materials, leading to poor scalp contact. This invention, through research, has discovered that when the scale of metals like gold and silver is reduced to the micro-nano scale, their flexibility is greatly enhanced, thus meeting the requirements for encapsulating liquid metals. Based on this, the present invention proposes a metal-coated EEG dry electrode based on liquid metal.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The flexible metal coating layer and the liquid metal in the inner layer play the following synergistic role: First, the fluidity of the liquid metal reduces the resistance to deformation of the metal thin layer (i.e., the flexible metal coating layer) to the greatest extent compared with the solid substrate, ensuring the excellent flexibility of the electrode and preventing interface damage; Second, the high conductivity of the liquid metal and the metal thin layer makes the electrode as a whole have metal-level conductivity, thus achieving both flexibility and high conductivity of the dry electrode; Third, the room temperature melting point of the liquid metal, under the good encapsulation of the metal thin layer, gives the electrode the unique function of achieving rigid-flexible transformation through body temperature triggering. In the air, the internal liquid metal is solid and rigid, and after contacting the scalp, the internal liquid metal melts and becomes flexible. This function effectively solves the trade-off problem of "rigid hair penetration" and "flexible fit" faced in signal acquisition in the thick hair area.

[0015] (2) This structure makes full use of the physical properties of liquid metal, such as its room temperature melting point, high conductivity, and fluidity. Firstly, it achieves a balance between excellent flexibility and high conductivity: for example, the conductivity of the copper-clad gallium electrode at 25 °C is 3.85 × 10⁻⁶. 6The S / m test demonstrates the high conductivity of the copper-coated gallium electrode; the contact impedance of the electrode at 8 Hz is 20.3% lower than that of the commercial Ag / AgCl dry electrode; the signal correlation between the copper-coated gallium electrode and the "gold standard" Ag / AgCl wet electrode at the Oz point is 95.5%, demonstrating the high fidelity performance of the copper-coated gallium electrode; secondly, body temperature triggering enables the electrode to transition from rigid to flexible. In air, the electrode remains rigid, allowing it to easily pass through hair; upon contact with the scalp, the liquid metal is heated and melted by body temperature, thus transforming the electrode into a flexible one, thereby solving the trade-off between "rigid hair penetration" and "flexible fit".

[0016] (3) Electroplating and chemical plating can be used to directly coat the surface of the liquid metal dry electrode substrate. At the same time, the coating prepared by electroplating and chemical plating has the characteristics of being dense, continuous and high-purity, and the thickness of the coating can be precisely controlled, which is especially important for the preparation of extremely thin coatings.

[0017] (4) The surface of dry electrodes is easy to clean and convenient to operate, which reduces the cost of using EEG technology and is conducive to promoting the application innovation and popularization of EEG technology to the public. Attached Figure Description

[0018] Figure 1 The image shows the actual product and cross-sectional view of the copper-coated gallium electrode prepared in Example 1.

[0019] Figure 2 The contact impedance comparison diagrams for different electrodes are as follows: the gallium electrode with a copper shell prepared in Example 1, the pure copper electrode used in Comparative Example 1, and the Ag / AgCl dry electrode used in Comparative Example 2.

[0020] Figure 3 The EEG data curves and their signal correlations at Oz are obtained by comparing the copper-shell gallium electrode prepared in Example 1 with the Ag / AgCl wet electrode used in the control example.

[0021] Figure 4 The power spectral density curve is obtained by transforming the electroencephalogram (EEG) data collected at Oz using the copper-shell-encased gallium electrode prepared in Example 1 after performing an eye-opening and eye-closing task using the Welch method.

[0022] Figure 5 The conductivity curve of the gallium electrode encased in a copper shell as described in Example 1 is a function of temperature.

[0023] Figure 6 The compression load-displacement curves of the copper shell including the gallium electrode described in Example 1 at 20 °C and 37 °C are shown.

[0024] Figure 7 This is a photograph of the gold-copper double-layer coated gallium-indium alloy electrode prepared in Example 5.

[0025] Figure 8 Images of electrodes with different plating solution compositions.

[0026] Explanation of markings in the diagram: 1-Liquid metal dry electrode substrate; 2-Flexible metal coating layer. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0028] In the case of EEG dry electrodes, the main difficulties in encapsulating liquid metal are: (1) the encapsulation layer needs to have good encapsulation ability for liquid metal, and also needs to take into account excellent flexibility and high conductivity. For example, although polymer materials have excellent flexibility, they do not have conductivity; (2) the low melting point of liquid metal (such as gallium melting point of 29.8 ℃) limits the temperature range for encapsulation layer preparation; (3) the preparation of complex-shaped encapsulation layers poses a challenge to the process, resulting in uncontrollable preparation accuracy.

[0029] Based on this, the present invention provides a metal-coated EEG dry electrode based on liquid metal, such as... Figure 1 As shown, it consists of a liquid metal dry electrode substrate 1 and a conductive flexible metal coating layer 2 that completely covers the outer surface of the liquid metal dry electrode substrate 1. The melting temperature of the liquid metal dry electrode substrate 1 is between room temperature and body temperature.

[0030] In some specific embodiments, the liquid metal dry electrode substrate is made of gallium or a gallium-based alloy.

[0031] In some specific embodiments, the flexible metal cladding layer is made of one or more of gold, silver, silver / silver chloride, copper, tin, stainless steel, platinum, cobalt, palladium and nickel, and its thickness is 5~10 μm.

[0032] Furthermore, the flexible metal cladding layer is a single-layer structure or a multi-layer structure, and when the cladding layer is a multi-layer structure, it is composed of several metal single layers stacked together, and the different metal single layers may be made of the same or different materials.

[0033] In some specific embodiments, the liquid metal dry electrode substrate has a comb-like structure, comprising an integrally formed electrode base and a plurality of electrode pillars disposed on the same side surface of the electrode base. For example, the electrode pillars may be evenly distributed and arranged in a circle near the edge of a circular electrode base.

[0034] In addition, the present invention also provides a method for preparing a metal-coated EEG dry electrode based on liquid metal, comprising the following steps: S1: After melting liquid metal, it is poured into a casting mold with a set cavity, and after solidification, a liquid metal dry electrode substrate is obtained; S2: The flexible metal coating layer is deposited on the outer surface of the liquid metal dry electrode substrate by electroplating and / or chemical plating, and then cleaned and dried to obtain the metal-coated EEG dry electrode.

[0035] In some specific embodiments, in S2, the liquid metal dry electrode substrate is pretreated before the flexible metal coating layer is deposited. The pretreatment process is as follows: The liquid metal dry electrode substrate was ultrasonically cleaned for 10 min in acetone, ethanol, deionized water, 20 wt% HCl solution and deionized water, respectively.

[0036] In this invention, high-quality coatings can be deposited on complex parts at low temperatures through electroplating and / or electroless plating. Compared to the silver plating method described in patent CN113397551A, electroplating and electroless plating produce dense, continuous, and high-purity coatings with precisely controllable thickness, which is especially crucial for the preparation of extremely thin coatings. However, gallium-based metals, due to their low melting point, easy oxidation, and unique surface energy and active states, are not conventional substrates for electroplating in traditional electroplating processes. Existing technologies have significant technical blind spots regarding pretreatment and plating parameters for such gallium-based metals. This leads to insurmountable technical obstacles when constructing high-quality metal coatings on gallium-based metal surfaces, such as poor coating coverage, poor adhesion, and narrow process windows. Specifically, in step S2, the electroless plating process, for example, is as follows: Within a temperature range of 20~30 °C, a liquid metal dry electrode substrate is placed in a chemical plating solution for deposition for 0.1~24 h to prepare coatings of different thicknesses; preferably, the temperature is 25 °C.

[0037] The electroplating process is as follows: Within a temperature range of 20~30 ℃, the liquid metal dry electrode substrate is immersed in the electroplating solution, and a current density of 1~5 A / dm is applied. 2 The deposition current is maintained for 1 to 120 minutes to prepare coatings of different thicknesses. Preferably, the electroplating solution is prepared from copper sulfate, sulfuric acid, hydrochloric acid, and sodium polydisulfide dipropane sulfonate. For example, the concentration of copper sulfate can be 200 g / L, the concentration of H2SO4 can be 60 g / L, the concentration of HCl can be 50 mg / L, and the concentration of sodium polydisulfide dipropane sulfonate can be 0.05 g / L.

[0038] Each of the above implementation methods can be implemented individually, or in any combination of two or more.

[0039] The above implementation methods will be described in more detail below with reference to specific embodiments.

[0040] Example 1 A copper-coated EEG dry electrode based on liquid metal and its preparation method, comprising the following steps: Step 1, the specific steps for preparing the liquid metal dry electrode substrate using the casting method are as follows: molten gallium is poured into a mold, solidified for 1 hour, and then demolded to obtain a comb-shaped gallium substrate electrode.

[0041] Step 2, the specific steps for pretreatment of the liquid metal dry electrode substrate are as follows: the gallium substrate electrode is ultrasonically cleaned in acetone, ethanol, 20wt% HCl solution and deionized water solution for 10 min in sequence.

[0042] Step 3, the specific steps for copper coating on the liquid metal dry electrode substrate using electroplating are as follows: Immerse the liquid metal dry electrode substrate in the copper electroplating solution (200 g / L CuSO4·5H2O, 60 g / L H2SO4, 50 mg / L HCl, 0.05 g / L Sodium 3,3'-dithiopropane-1,2-disulfonate (i.e., sodium polydisulfide dipropane sulfonate, SPS)) and apply a current density of 2 A / dm³. 2 The deposition current was applied for 30 minutes. After electroplating, the electrode was rinsed with deionized water and dried in a drying oven for 1 hour to obtain a copper-coated gallium electrode. Specifically, the copper shell thickness at the tip of the electrode comb was approximately 5 μm. Images of the copper-coated gallium electrode and its cross-section are shown below. Figure 1 (The left image is a picture of the actual object, and the right image is a cross-sectional view.)

[0043] Comparative Example 1 This comparative example uses a pure copper electrode with the exact same shape as that in Example 1.

[0044] Comparative Example 2 This comparative example uses commercially available Ag / AgCl dry electrodes (manufactured by Wuhan Greentech Technology Co., Ltd., made of conductive thermoplastic elastomer with Ag / AgCl coating, model: DX-S02A).

[0045] Comparative Example 3 This comparative example uses a commercially available Ag / AgCl wet electrode (Shanghai Niantong Intelligent Technology Co., Ltd.) and a commercially available medical conductive paste (manufactured by Wuhan Greentech Technology Co., Ltd., model: GT10).

[0046] Electrode-scalp contact impedance of copper-coated gallium electrodes was measured using a CHI760E electrochemical workstation from Shanghai Chenhua Co., Ltd. Commercial Ag / AgCl dry electrodes (Comparative Example 2) and pure copper electrodes (Comparative Example 1) were used as control groups. Two identical electrodes were placed symmetrically at a distance of 2.5 cm from the Fpz point. The scalp was sequentially treated with alcohol, saline solution, and a dry paper towel before electrochemical impedance spectroscopy (EIS) measurements were performed. The excitation pulse voltage amplitude for each test was 5 mV. The contact impedances of the three electrodes at 8 Hz are shown below. Figure 2 As shown, the copper-shell-encased gallium-indium alloy electrode prepared in Example 1 has a lower impedance at 8 Hz than the copper electrode of Comparative Example 1 and the Ag / AgCl dry electrode of Comparative Example 2 (a 20.3% reduction compared to the commercial Ag / AgCl dry electrode of Comparative Example 3).

[0047] The resistivity of the copper-cased gallium electrode of Example 1 at different temperatures was measured using a Tonghui TH2515 resistivity meter via a four-terminal method. The conductivity was obtained by taking the reciprocal of the resistivity. Temperature control was achieved using an environmental temperature control chamber. Figure 5 The conductivity of a copper-cased gallium electrode at different temperatures is shown, reflecting its high conductivity. The compressive load-displacement curves of the copper-cased gallium electrode at 20℃ and 37℃ were obtained using a microcomputer-controlled universal testing machine (MTS SANS CMT6104), as shown below. Figure 6 As shown, the stiffness of the copper-cased gallium electrode at 37 ℃ is significantly lower than that at 20 ℃, demonstrating the electrode's excellent flexibility at body temperature. Electroencephalogram (EEG) data of one subject were collected using the iRecorder W16 device from Shanghai NianTong Intelligent Technology Co., Ltd., and the copper-cased gallium electrode. The Ag / AgCl wet electrode (control) and the copper-cased gallium electrode were simultaneously placed at Oz, approximately 2 cm apart. Figure 3 The 4-second EEG data shown demonstrates that the copper-coated gallium electrode prepared in Example 1 has a signal correlation of 95.5% with the wet electrode used as the gold standard, reflecting the excellent signal acquisition quality of the copper-coated gallium electrode.

[0048] Resting-state EEG data of a subject at the Oz location were acquired using the iRecorder W16 device from Shanghai Niantong Intelligent Technology Co., Ltd., with copper-cased gallium electrodes. The acquisition process consisted of 1 minute with eyes open and 1 minute with eyes closed. The signals were then subjected to bandpass filtering (1-30 Hz) and power frequency filtering (50 Hz). The power spectral density curve was obtained by transforming the signal using the Welch method based on the Hamming window. The window length was 5 s and the overlap rate was 20%. Figure 4The power spectral density curves of EEG signals during the open and closed eye stages are shown. It can be observed that obvious alpha wave features (8~12 Hz) appear during the closed eye stage, while alpha waves are suppressed during the open eye stage.

[0049] Comparative Example 4: Compared to Example 1, except that the thickness of the copper shell is controlled to be 60 μm. Combined with Figure 2 It can be seen that when the copper shell coating is too thick, the contact resistance increases significantly, making it difficult to meet the application requirements for collecting bioelectrical signal data through contact between brain electrodes and the scalp.

[0050] Comparative Example 5: Compared to Example 1, the only difference is that the electroplating solution does not contain Sodium 3,3'-dithiopropane-1,2-disulfonate (i.e., sodium polydisulfide dipropane sulfonate, SPS).

[0051] Combination Figure 8 It can be seen that when SPS is omitted in the electroplating solution, the copper plating layer on the surface of the gallium electrode exhibits obvious defects such as incomplete coverage and poor adhesion.

[0052] Example 2: A liquid metal-based Ag / AgCl coated electroencephalogram (EEG) dry electrode and its preparation method, comprising the following steps: Step (1), the specific steps for preparing the liquid metal dry electrode substrate by casting are as follows: the molten gallium-indium alloy is poured into the mold, solidified for 1 h, and then demolded to obtain the gallium-indium alloy substrate electrode.

[0053] Step (2) Pretreatment of the base electrode: The gallium base electrode is ultrasonically cleaned in acetone, ethanol, 20 wt% HCl solution and deionized water for 10 min in sequence.

[0054] Step (3) involves electroless plating to coat the substrate electrode with silver. The specific steps are as follows: The substrate electrode is immersed in an electroless silver plating solution (composed of 10 g / L silver nitrate, 20 mL / L ammonium hydroxide, and 50 g / L potassium sodium tartrate) to deposit a silver layer for 30 min at a reaction temperature of 20 ℃. After electroless plating, the electrode is rinsed with deionized water and dried in a drying oven for 1 h to obtain a silver-coated gallium-indium alloy electrode.

[0055] Step (4) involves preparing a silver chloride layer on a silver-coated gallium-indium alloy electrode using a constant current method. The specific steps are as follows: The silver-coated gallium-indium alloy electrode is used as the anode and immersed in a 0.5 mol / L HCl solution. A platinum wire electrode is used as the cathode. The constant voltage parameter is set to 1 V for 5 min. Subsequently, the electrode is removed, washed with deionized water, and dried in a drying oven for 1 h to obtain an Ag / AgCl-coated gallium-indium alloy electrode.

[0056] The performance results of this embodiment are similar to those of Embodiment 1, and no further examples or analysis will be provided here.

[0057] Example 3 A gold-coated EEG dry electrode based on liquid metal and its preparation method, comprising the following steps: Step (1), the specific steps for preparing the liquid metal dry electrode substrate by casting are as follows: the molten gallium-indium alloy is poured into the mold, solidified for 1 h, and then demolded to obtain the gallium-indium alloy substrate electrode.

[0058] Step (2) Pretreatment of the base electrode: The gallium indium alloy base electrode is ultrasonically cleaned in acetone, ethanol, 20 wt% HCl solution and deionized water for 10 min in sequence.

[0059] Step (3) involves electroplating the substrate electrode with gold. The specific steps are as follows: Immerse the substrate electrode in the gold plating solution and apply a current density of 1 A / dm. 2 The deposition current was set for 15 minutes. After electroplating, the electrode was rinsed with deionized water and dried in a drying oven for 1 hour to obtain a gold-coated gallium-indium alloy electrode.

[0060] The performance results of this embodiment are similar to those of Embodiment 1, and no further examples or analysis will be provided here.

[0061] Example 4 A nickel-coated electroencephalogram (EEG) dry electrode based on liquid metal and its preparation method, comprising the following steps: Step (1), the specific steps for preparing the liquid metal dry electrode substrate by casting are as follows: the molten gallium-indium alloy is poured into the mold, solidified for 1 h, and then demolded to obtain the liquid metal dry electrode substrate.

[0062] Step (2) Pretreatment of the base electrode: The gallium indium alloy base electrode is ultrasonically cleaned in acetone, ethanol, 20 wt% HCl solution and deionized water for 10 min in sequence.

[0063] Step (3) involves electroplating the substrate electrode with nickel. The specific steps are as follows: Immerse the substrate electrode in the nickel plating solution and apply a current density of 2 A / dm². 2 The deposition current was set for 15 minutes. After electroplating, the electrode was rinsed with deionized water and dried in a drying oven for 1 hour to obtain a nickel-coated gallium-indium alloy electrode.

[0064] The performance results of this embodiment are similar to those of Embodiment 1, and no further examples or analysis will be provided here.

[0065] Example 5 A multilayer metal-coated EEG dry electrode based on liquid metal and its fabrication method, comprising the following steps: Step (1), the specific steps for preparing the liquid metal dry electrode substrate by casting are as follows: the molten gallium-indium alloy is poured into the mold, solidified for 1 h, and then demolded to obtain the gallium-indium alloy substrate electrode.

[0066] Step (2) Pretreatment of the base electrode: The gallium indium alloy base electrode is ultrasonically cleaned in acetone, ethanol, 20 wt% HCl solution and deionized water for 10 min in sequence.

[0067] Step (3) Copper coating is performed on the base electrode using chemical plating. The specific steps are as follows: In the temperature range of 20~30 ℃, the pretreated gallium indium alloy base electrode is placed in the chemical copper plating solution for 30 min, then washed with deionized water, and placed in a drying oven to dry for 1 h to obtain a copper-coated gallium indium alloy electrode.

[0068] Step (4) involves electroplating gold onto the copper-clad gallium-indium alloy electrode. The specific steps are as follows: Immerse the copper-clad gallium-indium alloy electrode in the gold plating solution and apply a current density of 1 A / dm³. 2 The deposition current was set for 5 minutes. After electroplating, the electrode was rinsed with deionized water and dried in a drying oven for 1 hour to obtain a gold-copper double-layer coated gallium-indium alloy electrode. A photograph of the gold-copper double-layer coated gallium-indium alloy electrode can be found below. Figure 7 .

[0069] The performance results of this embodiment are similar to those of Embodiment 1, and no further examples or analysis will be provided here.

[0070] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A metal-coated EEG dry electrode based on liquid metal, characterized in that, It consists of a liquid metal dry electrode substrate and a conductive micro-nano-scale flexible metal coating layer that completely covers the outer surface of the liquid metal dry electrode substrate. The melting temperature of the liquid metal dry electrode substrate is between room temperature and body temperature.

2. The metal-coated EEG dry electrode based on liquid metal according to claim 1, characterized in that, The liquid metal dry electrode substrate is made of gallium or a gallium-based alloy.

3. The metal-coated EEG dry electrode based on liquid metal according to claim 1, characterized in that, The flexible metal cladding layer is made of one or more of the following materials: gold, silver, silver / silver chloride, copper, tin, stainless steel, platinum, cobalt, palladium, and nickel, and its thickness is 5~10 μm.

4. The metal-coated EEG dry electrode based on liquid metal according to claim 3, characterized in that, The flexible metal cladding layer is a single-layer structure or a multi-layer structure. When the cladding layer is a multi-layer structure, it is composed of several stacked metal single layers, and the materials of the different metal single layers are the same or different.

5. The metal-coated EEG dry electrode based on liquid metal according to claim 1, characterized in that, The liquid metal dry electrode substrate has a comb-like structure, including an integrally formed electrode base and several electrode posts disposed on the same side surface of the electrode base.

6. A method for preparing a metal-coated EEG dry electrode based on liquid metal as described in any one of claims 1-5, characterized in that, Includes the following steps: S1: After melting liquid metal, it is poured into a casting mold with a set cavity, and after solidification, a liquid metal dry electrode substrate is obtained; S2: The flexible metal coating layer is deposited on the outer surface of the liquid metal dry electrode substrate by electroplating and / or chemical plating, and then cleaned and dried to obtain the metal-coated EEG dry electrode.

7. The method for preparing a metal-coated EEG dry electrode based on liquid metal according to claim 6, characterized in that, In S2, the liquid metal dry electrode substrate undergoes pretreatment before the deposition of the flexible metal coating layer. The pretreatment process is as follows: The liquid metal dry electrode substrate was ultrasonically cleaned for 10 min in acetone, ethanol, deionized water, 20% HCl solution and deionized water in sequence.

8. The method for preparing a metal-coated EEG dry electrode based on liquid metal according to claim 6, characterized in that, In step S2, the electroless plating process specifically includes: Within a temperature range of 20~30 ℃, the liquid metal dry electrode substrate was deposited in a chemical plating solution for 0.1~24 h. The electroplating process is as follows: Within a temperature range of 20~30 ℃, the liquid metal dry electrode substrate is immersed in the electroplating solution, and a current density of 1~5 A / dm is applied. 2 The deposition current lasts for 1 to 120 minutes.

9. The application of the liquid metal-coated EEG dry electrode as described in any one of claims 1-5 in the fabrication of a non-invasive brain-computer interface device.

10. The application according to claim 9, characterized in that, In the non-invasive brain-computer interface device, the metal-coated EEG dry electrode is configured to be placed at the Fpz or Oz point for signal acquisition.

Images