CN114190947A - Non-invasive electroencephalogram sensor based on flexible substrate and preparation method thereof - Google Patents
Non-invasive electroencephalogram sensor based on flexible substrate and preparation method thereof Download PDFInfo
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- A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
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- A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
- A61B5/25—Bioelectric electrodes therefor
- A61B5/263—Bioelectric electrodes therefor characterised by the electrode materials
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Abstract
The invention relates to a non-invasive electroencephalogram sensor based on a flexible substrate and a preparation method thereof. Compared with the prior art, the non-invasive electroencephalogram sensor based on the flexible substrate has the advantages of good conductivity, low skin impedance and good contact with the scalp, and can effectively monitor electroencephalograms.
Description
Technical Field
The invention belongs to the field of flexible electronic devices, and particularly relates to a non-invasive electroencephalogram sensor based on a flexible substrate and a preparation method thereof.
Background
The electroencephalogram sensor is a detection device which converts an ion current into an available electronic current in a conductor, and converts sensed measured information into the electronic current so as to meet the requirements of information transmission, processing, storage, display, control and the like. The general electroencephalogram sensor has low impedance and can reduce the impedance of the stratum corneum of the skin, the electroencephalogram sensor commonly used at present is a silver chloride wet electrode, and the purpose is achieved by smearing conductive gel on the skin. But this experience is generally unpleasant and requires cumbersome preparation and cleaning after use. Other approaches have been attempted, such as collecting brain electrical signals using specially configured dry electrodes, but the signal quality is far from that of the signals collected by wet electrodes. The semi-dry electrode is a hot direction of the current electroencephalogram sensing, and the idea of attaching a conductive substance to a porous material is widely adopted through the search of documents in the prior art, but at present, most of the semi-dry electrodes use metal particles as attachments, and the characteristics of unstable chemical properties and high manufacturing cost prevent the further development of the semi-dry electrodes.
The patent application CN201510847132.2 discloses a graphene flexible electroencephalogram capacitive electrode for inhibiting motion artifacts, which is composed of a base layer, a fabric conducting layer, a first motion artifact inhibiting layer, a filling layer, a second motion artifact inhibiting layer, a contact surface layer and an insulating shielding layer, wherein the flexible fabric forms the base layer; the conductive cloth forms a fabric conductive layer; the conductive sponge and the conductive cloth form a first motion artifact inhibiting layer; the insulating rubber plate forms a filling layer; the conductive cloth and the conductive sponge form a second motion artifact inhibiting layer; the graphene coating forms a contact surface layer; the insulating fabric constitutes an insulating barrier. The invention is an electroencephalogram dry electrode based on the capacitive coupling principle, adopts flexible electrode materials, has no stimulation and damage to skin, and can be worn for a long time. However, in the conductive cloth of the patent technology, nickel and copper are plated under high strength to form a metalized surface, the graphene coating only forms a contact surface layer and is essentially a capacitive brain electrode, the metal deposition cost is high, and the metal has chemical activity, and under a complex biochemical environment in contact with a human body, oxidation and sulfuration reactions may occur to generate substances harmful to the human body. And the capacitance electrode has the defect of high skin impedance, which can cause a large amount of low-frequency noise.
The porous sponge material has the advantages of simple preparation, low cost and wide application, and is widely applied to the fields of packaging and transportation, biomedicine, heat insulation materials, building engineering and the like due to the characteristics of high elasticity, large specific surface area, large porosity, small density and the like. The flexible sponge is also a popular choice in the field of sensors due to high recycling rate and flexibility, and an important design direction for realizing electric signal sensing is to attach a conductive substance on the surface of a flexible substrate.
Patent application CN202011196286.7 discloses a three-dimensional porous graphene/polyurethane flexible stress-strain sensor and a preparation method thereof, wherein a specific surfactant is preferably selected, and graphene sheets are uniformly coated on a polyurethane framework and have good binding force with the framework, so that a stably communicated conductive network is formed; when the composite structure (the three-dimensional porous graphene/polyurethane flexible stress strain sensor) is subjected to pressure, graphene sheet layers are mutually contacted, and the conductive network is changed, so that the resistance of the composite structure is changed, and a pressure signal is converted into a resistance signal; although the technology does improve the sensitivity, copper sheets are adhered to the upper bottom surface and the lower bottom surface of the sponge, the advantage of using the flexible sponge as a substrate is just covered, the electrode plane cannot be perfectly contacted with the uneven skull surface due to the high modulus of the copper sheets, the skin contact resistance is in negative correlation with the contact area, the larger the contact area is, the lower the skin contact resistance is, the fewer motion artifacts are, and the high-modulus metal sample is easily subjected to the chemical reaction after being etched by acidic sweat in the complex environment of a human body. In addition, a specific surfactant is preferably selected in the patent technology, the surfactant is used for controlling the agglomeration phenomenon of the graphene oxide in the reduction process, namely the graphene is not a uniform dispersion liquid after reduction, the graphene is converged into a lump, and a sponge is pressed in the middle, the patent technology utilizes the surfactant to resist the agglomeration phenomenon, because the final sample is applied to a stress strain sensor, and the linear relation between the resistance change and the deformation amount is extremely high, so that the graphene is uniformly dispersed on a matrix as far as possible and the dispersion is realized by using a dispersing agent (the surfactant), but the addition of the surfactant increases the cost and the working procedure on one hand, and also increases the impedance of the sensor on the other hand, and reduces the service life.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a non-invasive electroencephalogram sensor based on a flexible substrate and a preparation method thereof.
The purpose of the invention can be realized by the following technical scheme: a non-invasive electroencephalogram sensor based on a flexible substrate comprises the flexible substrate and reduced graphene oxide, wherein the reduced graphene oxide is deposited on the flexible substrate in a soaking and drying mode.
Further, the diameter of the sensor is 10mm to 15mm, preferably 12 mm.
Further, the height of the sensor is 12mm to 18mm, preferably 18 mm.
Furthermore, the flexible substrate is made of one of natural sponge, melamine and polyurethane, and has a porous sponge-like structure. The invention is finally applied to an electroencephalogram sensor after being added with physiological saline, so that the high flexibility and the high porosity of the sponge are both advantages utilized by the invention, the special flexibility ensures good contact with the skin, and the high porosity is a necessary condition for water storage. The hydrophilicity of the flexible substrate is influenced by surface active groups, the structure of the flexible substrate plays a crucial role for the porous materials, different substrates have great difference in micro-morphology, and the invention searches for the optimal flexible substrate with impedance, mechanical property and electroencephalogram sensing performance after long-time use. The density of the three measured is respectively: 14.7kg/m3、9.3kg/m3、18.5kg/m3。
The invention also provides a preparation method of the non-invasive electroencephalogram sensor based on the flexible substrate, which comprises the following steps:
s1, preparing graphene oxide ethanol dispersion liquid, and uniformly stirring and dispersing to obtain dispersion liquid;
s2, after the flexible substrate is pretreated, immersing the flexible substrate into the dispersion liquid to enable the flexible substrate to be completely soaked;
and S3, adding a reducing agent, completely reducing the system obtained in the step S2, cleaning, and drying to obtain the non-invasive electroencephalogram sensor product.
Further, the graphene oxide ethanol dispersion liquid in the step S1 is obtained by dispersing graphene oxide in ethanol and deionized water to obtain a suspension with a concentration of 1-12 mg/ml, and the specific method includes adding graphene oxide into ethanol and deionized water, stirring for 10-30 min at a rotation speed of 500rpm by using a magnetic stirrer, and then performing ultrasonic dispersion for 30-60 min at a frequency of 30-60 KHz by using an ultrasonic machine.
Further, the graphene oxide is prepared by an improved Hummers method, and specifically comprises the following steps: adding flake graphite into concentrated sulfuric acid in which potassium nitrate is dissolved in an ice water bath, wherein the mass ratio of the flake graphite to the potassium nitrate is 1:1, the mass-volume ratio of the flake graphite to the concentrated sulfuric acid is 1: 20-25 g/mL, stirring at 10-15 ℃ for 0.5 hour, raising the temperature to 40 ℃, continuing stirring for 3.5 hours, diluting with deionized water, centrifuging the precipitate, and drying to obtain pretreated graphite;
in an ice-water bath, KMnO is added4Slowly adding into concentrated sulfuric acid, KMnO4The mass volume ratio of the graphite to concentrated sulfuric acid is 3: 20-25 g/mL, then the pretreated graphite prepared in the previous step is added, stirred at 40 ℃ for 2 hours, and diluted by deionized water. Subsequently, H is added dropwise2O2Reduction of the remaining KMnO4. The prepared graphene oxide is washed by 5% hydrochloric acid and then is washed by deionized water for multiple times. And dialyzing the cellulose membrane for 7 days to obtain pure low-concentration graphene oxide. The concentration of the graphene oxide is determined by a gravimetric method, and the mass fraction is 2wt％。
Further, the reducing agent is one of hydrazine hydrate, sodium borohydride or ascorbic acid, preferably hydrazine hydrate.
Further, in the step S2, the flexible substrate is preprocessed by cutting the flexible substrate to a size suitable for the size of the electrode cap clamping groove, washing the flexible substrate with alcohol and deionized water for multiple times, and drying the flexible substrate in an oven;
after the flexible substrate is immersed into the dispersion liquid, ultrasonically dispersing for 30-60 min at the frequency of 30-60 KHz by using an ultrasonic machine; then extruding for 1-5min under the pressure of 10-30N; then placing the flexible substrate into the dispersion liquid again, carrying out ultrasonic dispersion and extrusion for 3-5 times to enable the flexible substrate to be completely soaked, and then carrying out ultrasonic dispersion for 1 hour.
Further, step S3
When the reducing agent is hydrazine hydrate, reducing by adopting steam at the temperature of 30-90 ℃ for 4 h;
when the reducing agent is sodium borohydride or ascorbic acid, heating and reducing in water bath at 90 deg.C for 12 h.
Compared with the prior art, the invention has the following beneficial effects:
1. compared with the traditional wet electrode electroencephalogram sensor, the semi-dry electroencephalogram sensor prepared by the invention can reduce skin impedance without using conductive gel, and is more convenient. The invention adopts the sponge as the matrix, the porous sponge material has high elasticity, large specific surface area, large porosity and small density, the flexible sponge is widely applied to the field of sensors with high repeated utilization rate and flexibility, but the conductivity is poor, the invention prepares the graphene oxide into the solvent to soak the flexible sponge, the washed and dried sponge substrate is soaked in the dispersion liquid and is extruded for a plurality of times to ensure complete soaking, then the graphene oxide is heated to generate reduction reaction on the sponge substrate, the high-frequency ultrasound can lead the graphite oxide flake to be 'embedded' on the substrate, and the subsequent processes of heating reduction and heating drying lead the reduced graphene oxide to be tightly adhered on the sponge framework, the good pore space of the sponge substrate can store a large amount of liquid, the self-release of saline water can reduce the skin contact impedance in the use process, even if the electrolyte can be gradually reduced after being released for a long time, but the reduced graphene oxide attached to the sponge matrix can still ensure that the electrode has good conductivity. In addition, the flexibility of the sponge can ensure that the electrode has high geometric consistency with uneven skull, and better contact is kept.
2. According to the invention, reduced graphene oxide is attached to the flexible substrate, and the double functions of ion conduction and electronic conduction can be realized after saline water is added, so that the impedance is reduced. The noninvasive brain electrode is bendable, good in conductivity and high in stability.
3. The sensor obtained by the method does not need to use high-modulus electrodes such as copper sheets and the like, and when the sensor is used, a sample is clamped into the clamping groove of the electrode cap and saline (common medical normal saline) is added for use. Due to good biocompatibility of the reduced graphene oxide, the sample can directly contact with the skin, and the contact impedance of the skin is reduced by adaptively releasing saline.
4. According to the invention, a surfactant is not needed, observation and experiments prove that the noninvasive electroencephalogram sensor based on the flexible substrate has the advantages of good conductivity, low skin impedance and good contact with scalp, and can effectively monitor electroencephalogram, wherein the flexible substrate is preferably natural sponge, the reducing agent is preferably hydrazine hydrate, and the reduction method is preferably steam reduction, because the reduction of GO in a sponge complex pore structure is more thorough due to the hydrazine hydrate steam reduction, the reducing agent is added into an aqueous solution to reduce GO, the agglomeration of rGO can cause the blockage of some pore structures, the interior cannot be reduced uniformly, and the non-uniform degree caused by the agglomeration of rGO can be avoided by reducing the hydrazine hydrate steam, so that the process of adding the surfactant is reduced, and the non-uniform degree caused by the agglomeration of rGO can be avoided.
Drawings
FIG. 1 is a schematic diagram of a combination of a conductive sponge and an electrode card slot prepared by a dipping method;
FIG. 2 is a schematic view of a sensor according to the present invention in use;
fig. 3 is a diagram of pure polyurethane sponge and reduced graphene oxide/polyurethane composite sponge with different concentrations.
Fig. 4 shows the microstructure of the polyurethane porous sponge and the microstructure of the polyurethane porous sponge after being compounded with reduced graphene oxide.
Fig. 5 is a brain wave image and a corresponding frequency domain diagram in the case where the eyes of the multiple shot region (Cz) are open and closed.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
Fig. 1 is a schematic structural diagram of a non-invasive electroencephalogram sensor 1 based on a flexible substrate and an electrode cap clamping groove 2, wherein one end of the non-invasive electroencephalogram sensor 1 is inserted into the electrode cap clamping groove 2, and is rotationally fixed on an electrode cap through a knob on the electrode cap clamping groove 2, so that the non-invasive electroencephalogram sensor 1 is in contact with an electrode 3 (an Ag/AgCl electrode is adopted in the invention), and the electrode 3 is connected with an electroencephalogram acquisition system through a lead 4. The non-invasive electroencephalogram sensor 1 comprises a flexible substrate and a reduced graphene oxide attachment layer. Graphene oxide is attached to a sponge matrix by means of immersion, ultrasound and high temperature reduction.
The invention discloses a method for preparing a non-invasive electroencephalogram sensor based on a flexible substrate, which comprises the following steps
Firstly, adding graphene oxide into 10mL of deionized water and 2.5mL of alcohol, stirring for 10-30 min by using a magnetic stirrer at the rotating speed of 500rpm, then ultrasonically dispersing for 30-60 min to obtain 12mg/mL viscous dispersion liquid by using an ultrasonic machine at the frequency of 30-60 KHz, and preparing the dispersion liquid with different concentrations (1mg/mL, 2mg/mL, 4mg/mL, 8mg/mL, 12mg/mL) by adjusting the adding amount of the graphene oxide
Cutting the flexible substrate into a cylinder with the diameter of 12mm and the height of 18mm, washing the cylinder with alcohol and deionized water for multiple times, putting the cylinder into an oven for drying, then putting the cylinder into the dispersion liquid, and ultrasonically dispersing the cylinder for 30-60 min by using an ultrasonic machine at the frequency of 30-60 KHz; then extruding for 1-5min under the pressure of 10-30N; then putting the flexible substrate into the dispersion liquid again, and carrying out ultrasonic dispersion and extrusion for 3-5 times to enable the flexible substrate to be completely soaked. Then reducing by adding a reducing agent.
And (3) washing the reduced conductive sponge with deionized water and alcohol, and then drying the conductive sponge in a vacuum drying oven at 80 ℃ for 12 hours to obtain a final sample.
And (3) immersing the obtained sample in medical normal saline for 1-5min, taking out, putting into the electrode cap clamping groove 2, contacting with the electrode 3, and arranging the electrode according to a standard international 10-20 system in a use state as shown in figure 2.
The present invention will be described in more detail with reference to examples
Specific example 1:
firstly, cutting polyurethane sponge to adapt to the size of a clamping groove of an electrode cap, washing the polyurethane sponge for multiple times by using ethanol and deionized water, and drying the polyurethane sponge in a 60 ℃ drying oven for 12 hours.
And secondly, taking 6g of graphene oxide, adding 10ml of deionized water and 2.5ml of alcohol into a reactor, magnetically stirring for 30min at 500rpm, and then carrying out ultrasonic treatment for 30min at the frequency of 40KHz to uniformly disperse the graphene oxide.
Thirdly, adding polyurethane sponge, and performing ultrasonic dispersion for 30min in the dispersion liquid at the frequency of 40KHz by using an ultrasonic machine; then extruding for 1min under the pressure of 10N, repeatedly performing ultrasonic infiltration extrusion to ensure that the sponge is completely infiltrated, and then performing ultrasonic treatment for 1h at the frequency of 40 KHz.
And step four, taking out the sample completely soaked by the GO solution, putting the sample into a beaker 1, adding 5mL of hydrazine hydrate into a beaker 2, and placing the beaker 1 and the beaker 2 into a fresh-keeping box with good sealing.
Fifthly, the preservation box is placed into an oven and heated and reduced for 4 hours at 90 ℃.
And sixthly, washing and drying the reduced conductive sponge, and then using the conductive sponge. The prepared sample has a macroscopic appearance as f in figure 3, and a is pure polyurethane sponge.
The microstructure of the prepared reduced graphene oxide/polyurethane sponge composite material is shown in fig. 4, wherein in fig. 4, (a) is a pure polyurethane porous sponge structure, and (b) is a microstructure of the composite of the polyurethane sponge and the reduced graphene oxide. It can be seen from the figure that (a) the surface of the pure polyurethane sponge in the figure is very smooth, after the pure polyurethane sponge is attached, the reduced graphene oxide is attached to the substrate skeleton, the micro-morphology becomes rough, and the sheet-like object in the figure is a lamellar structure of the reduced graphene oxide.
The prepared sample was added to physiological saline by directly immersing the sample in a beaker equipped with physiological saline and then taken out. The sample was then placed into the neck of an electrode cap, purchased from martin tyker, and the electrodes were arranged according to the standard international 10-20 system. The EEG signals were measured using an iRecorder W16 electroencephalogram acquisition system from Shanghai Miutong, Inc. with a sample rate set at 500 Hz.
Alpha wave measurements were performed in the multiple-shot region (Cz), see fig. 5. (a) The middle is a time domain image of the brain electrical signal, and the middle is a corresponding frequency domain image. It can be seen that after the eyes are closed at rest, the time domain graph has a remarkable regularization trend, and a remarkable alpha wave characteristic frequency appears at 10Hz in the frequency domain graph.
The experimental test results show that: the semi-dry electrode based on the flexible sponge can effectively detect electroencephalogram signals, and is simple to prepare and convenient to use.
Example 2
The preparation method was substantially the same as in specific example 1 except that 0.5g of graphene oxide was added, i.e., the concentration of the graphene oxide dispersion was 1 mg/mL. The macroscopic appearance of the prepared sample is shown as b in figure 3.
Example 3
The preparation method was substantially identical to that of specific example 1 except that the amount of graphene oxide added was 1g and that the concentration of the graphene oxide dispersion was 2 mg/mL. The macroscopic appearance of the prepared sample is shown as c in fig. 3.
Example 4
The preparation method was substantially identical to that of specific example 1 except that the amount of graphene oxide added was 2g and that the concentration of the graphene oxide dispersion was 4 mg/mL. The macroscopic appearance of the prepared sample is shown as d in fig. 3.
Example 5
The preparation method was substantially identical to that of specific example 1, except that the amount of graphene oxide added was 4g and that the concentration of the graphene oxide dispersion was 8 mg/mL. The macroscopic appearance of the prepared sample is shown as e in fig. 3.
Example 6
The preparation method was substantially identical to that of specific example 1 except that 2mL of hydrazine hydrate was added.
Example 7
The preparation method was substantially identical to that of specific example 1 except that 8mL of hydrazine hydrate was added.
Example 8
The preparation method was substantially the same as in example 1 except that the heating temperature by steam reduction was 30 deg.C
Example 9
The preparation method was substantially the same as in example 1 except that the steam reduction heating temperature was 60 ℃.
Example 10
The preparation method is basically the same as that of the specific example 1, except that sodium borohydride is selected as a reducing agent, 190mg of the reducing agent is directly added into GO dispersion liquid, the mixture is stirred and dispersed uniformly, and after the sponge is soaked completely, the dispersion liquid and the sample are placed into a water bath heating table together, and the water bath temperature is 90 ℃ and the heating is carried out for 12 hours.
Example 11
The preparation method is basically the same as that of the specific example 1, except that ascorbic acid is selected as a reducing agent, 880mg of ascorbic acid is directly added into GO dispersion liquid, the mixture is stirred and dispersed uniformly, and after sponge soaking is completed, the dispersion liquid and a sample are placed into a water bath heating table, and the water bath temperature is 90 ℃ for heating for 12 hours.
Example 12
The preparation method is basically the same as that of the specific example 1, except that the flexible substrate adopts natural sponge,
example 13
The preparation method is substantially identical to that of embodiment 1, except that melamine is used for the flexible substrate.
The products obtained in the above examples 1 to 13 were tested for their performance, and the test procedures and results were as follows:
the electrode impedance measuring method comprises the following steps: after the conductive sponge is immersed in saline water, conductive double-sided adhesive tapes are adhered to two ends of the cylinder, then conductive copper adhesive tapes are adhered to the two ends of the cylinder, and then a CHI660E electrochemical workstation is adopted to clamp a working electrode crocodile to a conductive copper tape at one end, and a reference electrode and a counter electrode are clamped to a conductive copper tape at the other end, wherein the frequency is set to be 10Hz (the typical frequency of brain waves is below 30 Hz). The resistance is conductivity, and the smaller the resistance, the better the conductivity.
Skin contact impedance measurement method: after the electrode cap of the testee is worn, the two electrodes are arranged at the positions of Fp1 and Fp2, a CHI660E electrochemical workstation is adopted, the working electrode crocodile clamp is clamped to an electrode cap lead at the Fp1 position, the reference electrode and the counter electrode are clamped to an electrode cap lead at the Fp1 position, and the frequency is set to be 10 Hz.
The mechanical stability measuring method comprises the following steps: similar to the electrode impedance measurement method, the measurement results are impedance values after 1000 cycles of fatigue compression of 50%. In order to simulate the extreme condition of whether the sample surface attachments still maintain good conductivity after being used for multiple times in practical application scenes.
5h contact resistance change: similar to the skin contact impedance measurement method, the electrode cap was worn after immersion in saline and the skin contact impedance increase was tested after 5 h. In order to simulate the feasibility of wearing the sample for a long time in a practical application scene.
From the above table, it can be seen that the electrode impedance and the skin contact impedance are substantially in a positive correlation, i.e. the lower the electrode impedance, the lower the skin contact impedance. It can be seen that (examples 1 to 5) impedance decreases significantly as GO dispersion concentration increases, because when GO concentration is too low, a complete electronic conduction path cannot be formed on the surface of the sponge skeleton, and therefore conduction can only be achieved by ions in the electrolyte (i.e., physiological saline), and in addition, the amount of the reducing agent and the setting of the reducing conditions also affect the effect of the final conductive adhesion layer (examples 6 to 9), i.e., the more completely the graphene oxide is reduced, the lower the impedance. Moreover, as can be seen from the examples 1, 10 and 11, the same graphene oxide attachment concentration and hydrazine hydrate vapor reduction effect are better than that of the reduction in aqueous solution, because hydrazine hydrate is extremely volatile at normal temperature, and even after heating, the vapor can easily enter into the complex structure inside the sponge, so that the reaction can be more complete. And reducing agent is added into the aqueous solution to reduce GO, and the aggregation of rGO can cause the blockage of some pore structures, so that the inside can not be reduced uniformly.
After 1000 cycles, the impedance increment of a sample (examples 1 to 11) using polyurethane as a substrate is basically below 30%, and by virtue of the structural characteristics of polyurethane, compared with natural sponge and melamine sponge, the framework is thicker and firmer, and is easier to recover after deformation, while the frameworks of natural sponge and melamine sponge are finer and have higher distribution density, and after multiple cycles, surface attachments fall off, but the capillary fiber structure has stronger water storage capacity. Therefore, the contact impedance does not change much in the case of long-time measurement.
Under long-time measurement, impedance is increased mainly because of the evaporation of normal saline, if the surface adheres to the good reduction graphene oxide layer, normal saline still can conduct electricity through the graphene layer on the skeleton after evaporating for a few, and the sample with lower concentration or poorer reduction degree, after normal saline evaporates, the graphene layer can not form a complete conduction path network, so the contact impedance changes greatly.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that; the above embodiments are exemplary, and those skilled in the art can change or modify the above embodiments within the scope of the present invention, and such modifications should be construed as the scope of the present invention.
Claims (10)
1. The non-invasive electroencephalogram sensor based on the flexible substrate is characterized by comprising the flexible substrate and reduced graphene oxide, wherein the reduced graphene oxide is deposited on the flexible substrate in a soaking and drying mode.
2. The non-invasive brain wave sensor based on a flexible substrate according to claim 1, wherein the diameter of the sensor is 10mm to 15 mm.
3. The non-invasive brain wave sensor based on a flexible substrate according to claim 1, wherein the height of the sensor is 12mm to 18 mm.
4. The non-invasive electroencephalogram sensor based on the flexible substrate as claimed in claim 1, wherein the flexible substrate is made of one of natural sponge, melamine and polyurethane, and is of a porous sponge-like structure.
5. A method for preparing a flexible substrate based non-invasive brain electrical sensor according to any one of claims 1-4, comprising the steps of:
s1, preparing graphene oxide ethanol dispersion liquid, and uniformly stirring and dispersing to obtain dispersion liquid;
s2, after the flexible substrate is pretreated, immersing the flexible substrate into the dispersion liquid to enable the flexible substrate to be completely soaked;
and S3, adding a reducing agent, completely reducing the system obtained in the step S2, cleaning, and drying to obtain the non-invasive electroencephalogram sensor product.
6. The method for preparing the non-invasive electroencephalogram sensor based on the flexible substrate as claimed in claim 5, wherein the concentration of the graphene oxide ethanol dispersion liquid in the step S1 is 1-12 mg/mL.
7. The method for preparing the non-invasive electroencephalogram sensor based on the flexible substrate according to claim 6, wherein the graphene oxide ethanol dispersion liquid is obtained by adding graphene oxide into ethanol and deionized water, stirring for 10-30 min at a rotation speed of 500rpm by using a magnetic stirrer, and then performing ultrasonic dispersion for 30-60 min at a frequency of 30-60 KHz by using an ultrasonic machine.
8. The method for preparing a non-invasive electroencephalogram sensor based on a flexible substrate according to claim 6, wherein the graphene oxide is prepared by a modified Hummers method.
9. The method for preparing the non-invasive electroencephalogram sensor based on the flexible substrate as claimed in claim 5, wherein the flexible substrate is pre-treated in step S2 by cutting the flexible substrate into a proper size, washing the flexible substrate with alcohol and deionized water for multiple times, and drying the flexible substrate in an oven;
after the flexible substrate is immersed into the dispersion liquid, ultrasonically dispersing for 30-60 min at the frequency of 30-60 KHz by using an ultrasonic machine; then extruding for 1-5min under the pressure of 10-30N; then placing the flexible substrate in the dispersion liquid again, and carrying out ultrasonic dispersion and extrusion for multiple times to enable the flexible substrate to be completely soaked, and then carrying out ultrasonic dispersion for 1 h.
10. The method for preparing a non-invasive electroencephalogram sensor based on a flexible substrate according to claim 5, wherein the reducing agent in step S3 is one of hydrazine hydrate, sodium borohydride or ascorbic acid;
when the reducing agent is hydrazine hydrate, reducing by adopting steam at the temperature of 30-90 ℃ for 4 h;
when the reducing agent is sodium borohydride or ascorbic acid, heating and reducing in water bath at 90 deg.C for 12 h.
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