Body temperature controlled release semi-dry electrode with low skin contact impedance and applications thereof

Abstract

The application discloses a body temperature controlled-release semi-dry electrode with low skin contact impedance and application thereof, and the body temperature intelligent controlled-release semi-dry electrode comprises an electrode containing Ag / AgCl material, a conductive layer, a substrate and a flexible protective layer. The conductive layer changes the contact characteristics of the conductive layer and the skin by forming a temperature-sensitive ion conductive hydrogel system with a perforated structure in the metalized nanosponge, so that the conductive layer and the skin can rapidly release trace electrolyte liquid to the contact interface in a almost non-inductive state through the heat conduction effect, thereby realizing the effect of non-inductive, stable and lower contact impedance. The semi-dry electrode overcomes the shortcomings of high contact impedance and instability of the commonly used dry electrode, and overcomes the shortcomings of complicated experimental treatment and large interference of the conductive paste wet electrode, and can be used for continuous acquisition of physiological signals such as electroencephalogram and electrocardiogram, and has the advantages of body temperature intelligent control, low and stable contact impedance and good biocompatibility.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of bioelectrode, and particularly relates to a body temperature controlled-release semi-dry electrode with low skin contact impedance and application thereof. BACKGROUND

[0002] The non-invasive brain-computer interface technology (BCI) is mainly positioned as "auxiliary diagnosis" and "abnormal monitoring" in the medical field. It is mainly applied to electroencephalogram monitoring, mental illness screening, lesion positioning of epilepsy and other neurological diseases, and corresponding rehabilitation fields such as attention training, learning and memory training, character input and prosthesis control. As a key device of non-invasive brain-computer interface technology, bioelectrode is often used for collecting electroencephalogram signals. The bioelectrode for collecting electroencephalogram signals is mainly divided into wet electrode, semi-dry electrode and dry electrode.

[0003] Among them, the most commonly used wet electrode is composed of an electroencephalogram cap, an Ag / AgCl electrode and conductive paste. The electrode impedance is low, which is the gold standard for collecting electroencephalogram signals. However, the conductive paste is not convenient to use, and it is easy to cause open circuit. Moreover, the setting of the electrode usually involves skin pretreatment and conductive paste injection, which is not only laborious but also time-consuming. In addition, the conductive paste makes people feel uncomfortable, and even causes skin allergy. The conductive paste is easy to dry over time, which weakens the signal. Therefore, the wet electrode cannot meet the requirements of BCI in real life.

[0004] The dry electrode is proposed to overcome the limitations of the wet electrode. Among them, there is a flexible polymer dry electrode, and some special structures are designed into dry electrodes, such as comb electrode and brush electrode. The dry electrode is not only convenient to use, but also can maintain conformal contact with the curved scalp surface due to its flexibility. Compared with the wet electrode, the dry electrode has shown considerable advantages, such as cleanliness, convenient setting and easy wearing. However, due to the lack of sufficient electrolyte fluid, the dry electrode-skin impedance generally reaches several hundred kilo-ohms, which is too large to meet the high requirements of brain-computer interface on signals. SUMMARY

[0005] The first object of the present application is to provide a body temperature controlled-release semi-dry electrode with low skin contact impedance to overcome the shortcomings of the prior art. The electrode can rapidly release a small amount of electrolyte liquid to the contact interface through the heat conduction effect generated by the conductive layer and the skin, thereby achieving the effect of non-inductive, stable and low contact impedance.

[0006] The present application adopts the following technical solutions:

[0007] The body temperature intelligent controlled release semi-dry electrode with low skin contact impedance comprises an electrode containing Ag / AgCl material, a conductive layer, a substrate and a flexible protective layer; one end of the conductive layer is connected with one end of the electrode containing Ag / AgCl material, and the other end is used for non-inductive contact with the skin; the flexible protective layer is arranged outside the conductive layer.

[0008] The material of the flexible protective layer is polydimethylsiloxane (PDMS) material; the material of the conductive layer is a conductive sensing unit combined with PNIPAM / PVA double network hydrogel and metalized nanosponge, and the conductive sensing unit is prepared by the following steps:

[0009] Step (1), the prepared fixed shape nanosponge is soaked in metal nanosilver slurry for multiple times, and then is placed in a vacuum drying environment for solidification to obtain metalized nanosponge;

[0010] Step (2), the solvent, monomer, crosslinking agent and polymer solution are uniformly mixed, then the metalized nanosponge prepared in step (1) is added, and after a period of refrigeration, the initiator and catalyst are added and uniformly stirred to continue refrigeration, and the hydrogel with perforated structure is polymerized in the metalized nanosponge; wherein the monomer is N-isopropyl acrylamide (NIPAM), and the polymer solution is polyvinyl alcohol (PVA) solution;

[0011] Step (3), the hydrogel with perforated structure obtained in step (2) is soaked in a sodium chloride solution with a certain concentration to obtain the conductive sensing unit.

[0012] Preferably, the metal nanosilver slurry in step (1) is 15-20% mass concentration of silver nanosilver slurry.

[0013] Preferably, the pressure for solidification in step (1) is 900-1000 Pa, the solidification temperature is 120-130 DEG C, and the solidification time is 1-1.5 h.

[0014] Preferably, the crosslinking agent in step (2) is N-N' methylene bisacrylamide (BIS), the initiator is ammonium persulfate (APS), the catalyst is tetramethyl diethylamine (TEMED), and the solvent is deionized water.

[0015] Preferably, the mass volume ratio of the monomer and crosslinking agent in step (2) is (10-15) mg:2 μL.

[0016] Preferably, the mass concentration of the polymer solution in step (2) is 1%-4%, more preferably 2%.

[0017] Preferably, the first refrigeration time in step (2) is 25-35 min, and the second refrigeration time is 24 h, and the refrigeration temperature is 8-10 DEG C.

[0018] Preferably, the volume ratio of the initiator, the catalyst and the crosslinking agent in step (2) is (4-6):1:40.

[0019] Preferably, the molar concentration of the sodium chloride solution in step (3) is 0.15-0.2 mol / L.

[0020] Preferably, the polydimethylsiloxane is prepared by the following steps:

[0021] The PDMS main agent and the curing agent are mixed in a mass ratio of 10:1, and then are placed in a vacuum drying environment for a period of time, and then are taken out and placed at room temperature for a period of time to obtain the polydimethylsiloxane.

[0022] Preferably, the pressure of the vacuum drying and curing is 900-1000 Pa, the curing temperature is 45-50 DEG C, the curing time is 1-1.5 h, and the room temperature placing time is 24-48 h.

[0023] Preferably, the substrate comprises an electrode male buckle and a PET film, and a through hole is formed in the center of the PET film; the electrode comprising the Ag / AgCl material comprises an integrally-formed sheet-shaped component and a columnar component, and the surface is coated with the Ag / AgCl material; one end of the columnar component is connected to one side of the sheet-shaped component, and the other end of the columnar component passes through the through hole of the PET film and is embedded with the electrode male buckle; the sheet-shaped component is embedded in the flexible protective layer, and the PET film is arranged on one side of the flexible protective layer.

[0024] The second object of the present application is to provide the application of the above-mentioned body temperature controlled-release semi-dry electrode with low skin contact impedance in collecting bioelectric signals.

[0025] Preferably, the bioelectric signals comprise electroencephalogram signals and electrocardiogram signals.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] (1) The electrode of the present application can realize intelligent temperature-controlled release of electrolyte to achieve the effect of non-inductive, stable and low contact impedance; the present application adds the PNIPAM / PVA double network hydrogel with temperature-sensitive properties in the conductive layer, changes the contact characteristics of the conductive layer and the skin, and actively releases a small amount of electrolyte to the contact interface through the heat conduction effect under the condition of nearly inductive contact with the skin, thereby realizing the effect of non-inductive, stable and low contact impedance.

[0028] (2) The electrode conductive layer of the present application has good tensile strength and solidification, thereby avoiding problems such as large amount of residue on the skin, open circuit, and even skin allergy caused by strong fluidity of conductive paste, and improving the convenience, comfort and biocompatibility.

[0029] (3) The electrode of the present application adopts the dual-conduction enhancement principle of ion conduction as the main and electronic conduction as the auxiliary, the hydrogel serves as the electrode containing Ag / AgCl material and the skin connection medium, the charge is transmitted through the oxidation-reduction reaction of the salt in the hydrogel and Ag / AgCl, and the metalized nanosponge contains Ag nanoparticles, the free electrons move directionally to form current, thereby enhancing the overall conductivity of the electrode. The silver nanoparticle slurry has adhesion, which can adhere the nanoparticles in it to the sponge fibers, ensuring the electronic conductivity. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Structure diagram of the body temperature intelligent controlled release semi-dry electrode with low skin contact impedance.

[0031] Figure 2 Forming device diagram of the body temperature intelligent controlled release semi-dry electrode with low skin contact impedance.

[0032] Figure 3 Performance test diagram of the storage electrolyte solution of the PNIPAM / PVA double network hydrogel.

[0033] Figure 4 Performance test diagram of the PNIPAM / PVA double network hydrogel releasing electrolyte solution at different temperatures.

[0034] Figure 5 Performance test diagram of the PNIPAM / PVA double network hydrogel releasing electrolyte solution at body temperature.

[0035] Figure 6 Stretching test result diagram of the conductive sensing unit.

[0036] Figure 7 Skin-electrode impedance diagram of the body temperature intelligent controlled release semi-dry electrode with low skin contact impedance and dry and wet electrodes.

[0037] Figure 8 Electrode pair impedance diagram of the body temperature intelligent controlled release semi-dry electrode with and without metalization.

[0038] Figure 9 Signal diagram of the body temperature intelligent controlled release semi-dry electrode with low skin contact impedance collecting electrocardio signals after rest and exercise.

[0039] Figure 10 Comparison diagram of the body temperature intelligent controlled release semi-dry electrode with low skin contact impedance and commercial electrodes collecting electrocardio signals at rest.

[0040] Figure 11 Signal diagram of brain electricity collected by body temperature intelligent controlled release semi-dry electrode with low skin contact impedance.

[0041] Figure 12 Power spectrum diagram of brain electricity collected by body temperature intelligent controlled release semi-dry electrode with low skin contact impedance.

[0042] Figure 13 Signal diagram of brain electricity collected by conductive paste wet electrode.

[0043] Figure 14 Power spectrum diagram of brain electricity collected by conductive paste wet electrode.

[0044] Embodiment

[0045] The application will be described in detail below in combination with the drawings and embodiments.

[0046] As described previously, in view of the deficiencies of the prior art, the present inventors have long studied and practiced a lot and proposed the technical solution of the present application, which is mainly based on at least comprising:

[0047] The application discloses a body temperature intelligent controlled release semi-dry electrode with low skin contact impedance, wherein the electrode is added with PNIPAM / PVA double-network hydrogel with temperature-sensitive characteristics in a conductive layer, so that the electrode can actively release a small amount of electrolyte liquid through a heat conduction effect under the condition of nearly non-inductive contact with the skin, thereby realizing the effect of non-inductive, stable and low contact impedance; the conductive layer has good tensile strength and firmness, thereby avoiding the problems of a large amount of residues on the skin, open circuit, even skin allergy caused by strong fluidity of conductive paste, and improving the convenience, comfort and biocompatibility of use; the electrode adopts a double-conductive enhancement principle of mainly ion conduction and auxiliary electron conduction, thereby enhancing the overall conductivity of the electrode.

[0048] The application discloses a body temperature intelligent controlled release semi-dry electrode with low skin contact impedance, and the body temperature intelligent controlled release semi-dry electrode with low skin contact impedance comprises a substrate 1, an Ag / AgCl electrode 2, a flexible protective layer 3 and a conductive layer 4 in sequence.

[0049] The substrate 1 comprises an electrode male buckle and a PET film, and the PET film is provided with a through hole in the center and is in contact with the conductive layer 4 on one side;

[0050] The Ag / AgCl electrode 2 comprises an integrally formed sheet-shaped component and a columnar component; one end of the columnar component is connected to one side of the sheet-shaped component, and the other end of the columnar component penetrates through a through hole of the PET film in the base 1 and is embedded with an electrode male buckle; the diameter of the through hole is greater than or equal to the diameter of the columnar component and less than the diameter of the sheet-shaped component; the sheet-shaped component, the PET film in the base 1 and the conductive layer 4 are in contact;

[0051] The material of the flexible protective layer 3 is PDMS material, and the material of the flexible protective layer 3 is prepared by the following steps:

[0052] Before pouring, the mold is surface treated by spraying a release agent, and the PDMS main agent and the curing agent are mixed in a weight ratio of 10:1 and poured into the mold; after the poured mold is placed in a vacuum drying box with a pressure of 1000 Pa and a curing temperature of 50 DEG C for 1 h, it is taken out and placed at room temperature for 24 h to be demolded, thereby the flexible protective layer 3 is prepared.

[0053] The material of the conductive layer 4 is a combination of PNIPAM / PVA double network hydrogel and metalized nanosponge, and the material of the conductive layer 4 is prepared by the following steps:

[0054] The prepared fixed cylindrical nanosponge is soaked in Ag nano-solution with a concentration of 15-20% for multiple times, and then is placed in a vacuum drying box with a pressure of 900-1000 Pa and a curing temperature of 120-130 DEG C for 1-1.5 h to prepare the metalized nanosponge; deionized water, N-isopropyl acrylamide (NIPAM), N-N' methylene bisacrylamide (BIS) and polyvinyl alcohol (PVA) solution are uniformly mixed, wherein the mass-volume ratio of NIPAM and BIS is (10-15) mg:2 μL, and the mass concentration of the PVA solution is 1%-4%; then the prepared metalized nanosponge is refrigerated for 25-35 min, and then ammonium persulfate (APS) and tetramethylammonium ethyldiamine (TEMED) are added and uniformly stirred and refrigerated for 24 h, and the refrigeration temperature is 8-10 DEG C; the hydrogel with a perforated structure is slowly polymerized in the metalized nanosponge; finally, the hydrogel is soaked in a sodium chloride solution with a molar concentration of 0.15-0.2 mol / L.

[0055] In use, the electrode provided by the application is directly placed on the skin with the end of the conductive layer not in contact with the Ag / AgCl electrode, and then the GND electrode and the Ref electrode are fixed at the corresponding positions to start collecting signals; in the process of use, the electrode of the application actively releases a small amount of electrolyte liquid by relying on the heat conduction effect, so that the effect of non-inductive, stable and low contact impedance can be achieved, and physiological signals can be stably collected.

[0056] In the following, certain example embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the embodiments of the present application. Therefore, the drawings and description are to be considered exemplary in nature rather than limiting.

[0057] Nanosponge was purchased from Hubei Xijie Daily Necessities Co., Ltd., Ag nanoparticle slurry was purchased from Suzhou Jingsha Electronic Technology Co., Ltd.; N-isopropyl acrylamide (NIPAM) was purchased from Shanghai Macklin Biochemical Technology Co., Ltd., N-N' methylene bisacrylamide (BIS), polyvinyl alcohol (PVA) were purchased from Aladdin Reagent (Shanghai) Co., Ltd., deionized water, ammonium persulfate (APS) and tetramethyl ethylenediamine (TEMED) were purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd., sodium chloride (NaCl) was purchased from Zhejiang Hannuo Chemical Technology Co., Ltd.; Commercial electrode was purchased from Shanghai LiTu Medical Instrument Co., Ltd., conductive paste was purchased from Wuhan Green Tech Technology Co., Ltd.

[0058] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0059] Example 1: Preparation of double network hydrogel and its conductive layer combined with metalized nanosponge

[0060] 130 mg of N-isopropyl acrylamide (NIPAM) and 1 mL of 2% polyvinyl alcohol (PVA) solution were added to a centrifuge tube and stirred to dissolve; then 200 μL of N-N' methylene bisacrylamide (BIS) was added for crosslinking, and the solution was cooled in a refrigerator (8℃) for 30 minutes. Finally, 5 μL of tetramethyl ethylenediamine (TEMED) was added as a catalyst, and 30 μL of 4% deionized water ammonium persulfate (APS) as an initiator, to prepare a PNIPAM / PVA double network hydrogel pre-polymer solution; then the pre-polymer solution was quickly poured into the prepared mold, and the mold was placed in a sealed bag, and waited for 24 hours in a refrigerator (8℃) to obtain a PNIPAM / PVA double network hydrogel; finally, it was immersed in a 0.2 mol / L sodium chloride solution.

[0061] The prepared, fixed-shape nanosponge was repeatedly immersed in a 20% Ag nanoparticle slurry and then cured in a vacuum drying oven at 1000 Pa and 120°C for 1 hour to produce a metallized nanosponge. 130 mg of N-isopropylacrylamide (NIPAM) and 1 mL of a 2% polyvinyl alcohol (PVA) solution were added to a centrifuge tube and stirred thoroughly to dissolve. 200 μL of N-N'-methylenebisacrylamide (BIS) was then added for crosslinking. The metallized nanosponge was then added and cooled in a refrigerator (8°C) for 30 minutes. Finally, 5 μL of tetramethylethylenediamine (TEMED) was added as a catalyst, and 30 μL of 4% deionized ammonium persulfate (APS) was added as an initiator. The mixture was then placed in a refrigerator (8°C) for 24 hours to form a hydrogel-like conductive layer with a perforated structure, which was then slowly polymerized within the metallized sponge. The resulting layer was then immersed in a 0.2 mol / L sodium chloride solution.

[0062] The ability of PNIPAM / PVA double network hydrogel to intelligently store electrolytes at body temperature was measured using a gravimetric method. Each sample was placed in a 0.2 mol / L sodium chloride solution at 26°C for at least 24 hours, and its weight W was s It is obtained after wiping the surface with filter paper; W T Refers to the weight of these samples after they have been in sodium chloride solution for a certain period of time. The temperature is controlled by a heating stage. W is obtained after the samples are dried in a vacuum. d , water retention rate related to temperature (W R ) is calculated using the following formula:

[0063] W R =(W T -W d ) / (W s -W d )

[0064] The ability of PNIPAM / PVA double network hydrogel to store electrolyte solution was tested. Figure 3 .

[0065] The gravimetric method was also used to measure the ability of PNIPAM / PVA double network hydrogel to release electrolyte solution at body temperature. Each sample was placed in a sodium chloride solution with a molar concentration of 0.2 mol / L at 28-42 ° C for at least 24 hours, and its weight W was s It is obtained after wiping the surface with filter paper; W t Refers to the weight of these samples after they have been in sodium chloride solution for a certain period of time. The temperature is controlled by a heating stage. W is obtained after the samples are dried in a vacuum. d , water retention rate related to temperature (W' R) is calculated by the following formula:

[0066] W' R = (W t -W d ) / (W s -W d )

[0067] The release of electrolyte solution of the PNIPAM / PVA double network hydrogel near body temperature, i.e. 30-34℃, is calculated by the following formula:

[0068] W L = (W 30 -W 34 ) / W 30

[0069] The above W L refers to the release rate of electrolyte solution near body temperature, i.e. 30-34℃, W 30 refers to the weight at 30℃, and W 34 refers to the weight at 34℃.

[0070] The body temperature intelligent release of electrolyte solution of the PNIPAM / PVA double network hydrogel was tested, and the results are shown in Figure 4 and Figure 5 .

[0071] The mechanical properties of the conductive sensing unit were tested by using the XS(08)XG type high modulus fiber strength tester of Shanghai Xusai Instrument Co., Ltd. The conductive sensing unit (10mm x 7mm x 1mm) was placed in the tensile clamp for tensile property test at a speed of 10mm / min. The maximum tensile strength was about 258kPa, and the elongation at break was 77%.

[0072] The tensile properties of the conductive sensing unit were tested, and the results are shown in Figure 6 .

[0073] Test Example 1: Test of electrode-skin impedance

[0074] (1) The gel of the commercial electrode was removed to obtain a commercial electrode substrate as a mold, and the conductive layer prepared by combining the double network hydrogel prepared in Example 1 and the metalized nanosponge was added as a working electrode; the commercial electrode was used as a reference electrode and a counter electrode; the working electrode was attached to the forehead, and the reference electrode and the counter electrode were attached to the two places behind the ear bones, respectively, and the impedance value at 10Hz was tested. Continuous measurement for 1 hour, measurement every 5, 10, 20, 30, 40, 50, 60 minutes, and the electrode was not removed during the measurement.

[0075] (2) The conductive paste wet electrode and the suction ball dry electrode were used as working electrodes, and the commercial electrode was used as a reference electrode and a counter electrode, and the same test method was used.

[0076] This method perfectly restores the use scenario of the counter electrode, which is very suitable for comparison. Figure 7 The results show that the impedance of the prepared conductive sensing unit electrode is much lower than that of the dry electrode of the suction ball, the performance is similar to that of the conductive paste wet electrode, and the skin surface has no excess residue.

[0077] Test Example 2: Impedance of the electrode pair

[0078] (1) The conductive sensing unit combined with the double-network hydrogel and the metalized nanosponge was prepared by the method in Example 1, with a diameter of 16 mm and a thickness of 1.5 mm.

[0079] (2) Two conductive sensing unit electrodes in Test Example 1 were used to form an electrode pair, the working electrode was connected to the male buckle of one electrode, and the reference electrode was connected to the female buckle of the other electrode. The impedance of the electrode pair was measured by the two-electrode system.

[0080] (3) As a comparison, the conductive sensing unit combined with the double-network hydrogel and the non-metalized nanosponge was prepared by the method in Example 1, with a diameter of 16 mm and a thickness of 1.5 mm. The same test method was used.

[0081] Figure 8 The test results show that the impedance of the metalized conductive sensing unit at 10 Hz is 52Ω (less than 250Ω), which meets the characteristics of low impedance and excellent conductivity, and is much lower than the impedance of the non-metalized conductive sensing unit at 10 Hz, which is 100Ω.

[0082] Application Example 1

[0083] Step 1: Preparation of a body temperature intelligent controlled-release semi-dry electrode with low skin contact impedance

[0084] (1) Flexible protective layer preparation: Before pouring, the mold was treated with mold release agent for surface treatment, and the PDMS main agent and curing agent were mixed in a weight ratio of 10:1 and poured into the mold. After placing the poured mold in a vacuum drying oven with a pressure of 1000 Pa and a curing temperature of 50℃ for 1h, it was taken out and placed at room temperature for 24h to be demolded, and the flexible protective layer 3 was prepared.

[0085] (2) Electrode substrate preparation: The PET film with a center through-hole was cut by a laser cutting machine, and the columnar assembly of the electrode containing Ag / AgCl material was inserted through the center hole of the PET film, and the male buckle was embedded together.

[0086] (3) The base combined with the electrode containing Ag / AgCl material is passed through the through hole in the middle of the flexible protective layer, and the conductive sensing unit combined with the cylindrical double network hydrogel and the metalized nanosponge prepared in Example 1 is added to obtain a body temperature intelligent controlled release semi-dry electrode with low skin contact impedance, and the structure is as shown in Figure 1 , and the forming mold is as shown in Figure 2 .

[0087] Step two, collect electrocardiogram using the body temperature intelligent controlled release semi-dry electrode with low skin contact impedance

[0088] The body temperature intelligent controlled release semi-dry electrode with low skin contact impedance is pasted on the inside of the right wrist, and the GND electrode and the Ref electrode are placed on the back of the left wrist and the back of the hand, respectively, using a contrast electrode. The electrocardiogram signal acquisition and recording conditions of the subjects in resting state and after exercise are tested respectively. The results are as shown in Figure 9 , and it can be seen that the signal quality obtained by using the body temperature intelligent controlled release semi-dry electrode with low skin contact impedance is excellent and stable.

[0089] Step three, collect electrocardiogram using a commercial electrode

[0090] The commercial electrode is used instead of the body temperature intelligent controlled release semi-dry electrode with low skin contact impedance, and the remaining steps remain the same as step two. The results are as shown in Figure 10 .

[0091] Application Example 2

[0092] Step one, preparation of a body temperature intelligent controlled release semi-dry electrode with low skin contact impedance

[0093] (1) Flexible protective layer preparation: before pouring, the mold is surface treated by spraying release agent, and the PDMS main agent and curing agent are mixed in a weight ratio of 10:1 and poured into the mold; after pouring, the mold is placed in a vacuum drying box with a pressure of 1000 Pa and a curing temperature of 50℃ for 1h, then taken out and placed at room temperature for 24h to demold, and the flexible protective layer 3 is prepared.

[0094] (2) Electrode base preparation: the PET film with a central through hole is cut by a laser cutting machine, and the cylindrical assembly containing the electrode with Ag / AgCl material is passed through the central hole in the middle of the PET film and embedded with a male buckle.

[0095] (3) The base combined with the electrode containing Ag / AgCl material is passed through the through hole in the middle of the flexible protective layer, and the conductive sensing unit combined with the cylindrical double network hydrogel and the metalized nanosponge prepared in Example 1 is added to obtain a body temperature intelligent controlled release semi-dry electrode with low skin contact impedance, and the structure is as shown in Figure 1 .

[0096] Step two, using the above-mentioned body temperature intelligent controlled release semi-dry electrode with low skin contact impedance to collect brain electrical

[0097] According to the 10-20 international standard lead system, the self-adhesive electrode with low skin contact impedance is pasted at the FP1 position, and the Ref electrode and the GND electrode are placed behind the ear. The collection process is divided into two parts, open eyes and closed eyes. The collection device is Olympic CFM6000, and the collected brain electrical signals are preprocessed as Figure 11 , D1 is the electroencephalogram when the eyes are open, and D2 is the electroencephalogram when the eyes are closed. Signal preprocessing, i.e. using MATLAB to process data, including removing baseline, band-pass filtering (0.5Hz-45Hz). The signal changes of blinking and closing eyes can be clearly seen. Figure 12 is the power spectrum diagram of the signal in the two processes of opening and closing eyes, and the peak value at 10Hz during closing eyes can be seen, which represents the alpha wave (alpha wave frequency range is 8-13Hz) in the brain electrical.

[0098] Electrophysiological signals mainly include brain electrical, heart electrical and muscle electrical. Among them, brain electrical is the lowest in amplitude (μV level) and is most susceptible to noise interference, and heart electrical and muscle electrical (mv level) are relatively easy to obtain compared with brain electrical.

[0099] Step three, using conductive paste wet electrode to collect brain electrical

[0100] Using conductive paste wet electrode instead of body temperature intelligent controlled release semi-dry electrode with low skin contact impedance, the rest of the steps remain the same as step two. The results are shown in Figure 13 and Figure 14 .

[0101] As can be seen, the body temperature intelligent controlled release semi-dry electrode with low skin contact impedance not only has physiological signal collection performance comparable to the gold standard conductive paste wet electrode, but also has a nearly inductive and stable collection method, which is a better choice than dry and wet electrodes.

[0102] Comparative example 1

[0103] The concentration of polyvinyl alcohol (PVA) solution in example 1 was set to 0, 1%, 2%, 3%, and 4%, respectively, and the rest of the conditions remained unchanged, to prepare PNIPAM / PVA double network hydrogel with different concentrations of polyvinyl alcohol (PVA) solution. Test its ability to store electrolyte solution, the results are shown in Figure 3 .

[0104] Comparative example 2

[0105] The concentration of polyvinyl alcohol (PVA) solution in Example 1 was set to 0, 1%, 2%, 3%, 4%, respectively, and the rest of the conditions were unchanged, to prepare PNIPAM / PVA double network hydrogels with different concentrations of polyvinyl alcohol (PVA) solution. The ability of the body temperature intelligent release of electrolyte solution was tested, and the results are shown in Table 1. Figure 5 Table 1

Claims

1. A body temperature controlled release semi-dry electrode with low skin contact impedance, comprising an Ag / AgCl material containing electrode, a conductive layer, a substrate and a flexible protective layer; one end of the conductive layer is connected to one end of the Ag / AgCl material containing electrode, and the other end is used for non-inductive contact with the skin; the conductive layer is externally surrounded by a flexible protective layer; the material of the flexible protective layer is polydimethylsiloxane (PDMS) material; characterized in that the material of the conductive layer is a conductive sensing unit combining PNIPAM / PVA double network hydrogel and metalized nanosponge, which is prepared by the following steps: Step (1), the prepared fixed shape nanosponge is soaked in metal nanosilver slurry for multiple times, and then placed in a vacuum drying environment for solidification to obtain metalized nanosponge; Step (2), mix the solvent, monomer, crosslinking agent and polymer solution uniformly, then add the metalized nanosponge prepared in step (1), refrigerate for a period of time, then add initiator and catalyst and stir uniformly, continue to refrigerate, and polymerize in the metalized sponge to form a perforated structure of hydrogel; wherein the monomer is N-isopropyl acrylamide (NIPAM), and the polymer solution is polyvinyl alcohol (PVA) solution; Step (3), the perforated structure of hydrogel obtained in step (2) is soaked in a sodium chloride solution with a certain concentration to obtain the conductive sensing unit.

2. The body temperature controlled-release semi-dry electrode with low skin contact impedance according to claim 1, characterized in that, The metal nanosilver slurry in step (1) is a silver nanoparticle slurry with a mass concentration of 15-20%.

3. The low-impedance-to-skin temperature-controlled release semi-dry electrode of claim 1, wherein, In step (2), the crosslinking agent is N-N' methylene bisacrylamide (BIS), the initiator is ammonium persulfate (APS), the catalyst is tetramethyl ethylenediamine (TEMED), and the solvent is deionized water.

4. The low- skin contact impedance, body temperature controlled release semi-dry electrode of claim 1, wherein, In step (2), the mass volume ratio of the monomer and crosslinking agent is (10-15) mg: 2 μL.

5. The low- skin contact impedance, body temperature controlled release semi-dry electrode of claim 1, wherein, In step (2), the mass concentration of the polymer solution is 1%-4%.

6. The low- skin contact impedance, body temperature controlled release semi-dry electrode of claim 1, wherein, In step (2), the first refrigeration time is 25-35 min, and the second refrigeration time is 24 h, and the refrigeration temperature is 8-10℃.

7. The low-impedance-to-skin temperature-controlled release semi-dry electrode of claim 1, wherein, In step (2), the volume ratio of initiator, catalyst and crosslinking agent is (4-6) : 1:

40.

8. The low- skin contact impedance, body temperature controlled release semi-dry electrode of claim 1, wherein, In step (3), the molar concentration of the sodium chloride solution is 0.15-0.2 mol / L. 9.The body temperature controlled release semi-dry electrode with low skin contact impedance according to any one of claims 1-8 is used for collecting bioelectric signals.

10. Use according to claim 9, characterized in that, The bioelectric signals include electroencephalogram and electrocardiogram.

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