Flexible pressure sensor with cyclic monitoring stability and preparation method thereof

Abstract

The invention discloses a flexible pressure sensor with cyclic monitoring stability and a preparation method thereof, and belongs to the field of flexible pressure sensors. The invention aims to solve the technical problem that most flexible pressure sensors are simply attached and fixed only by using adhesive tapes, so that the wearable performance and the stability of the sensors are greatly reduced. The flexible SEBS substrate with a prismatic table microstructure is prepared by using a template method, and the conductive adhesive is prepared from amylopectin, citric acid, PEDOT: PSS and PVA and is used for interlayer adhesion of a sensing layer, so that the stability of the sensor is enhanced. The structure of the sensor is simplified, the sensor is easier to wear, the anti-interference performance of the sensor is enhanced, the relative displacement of the sensor structure possibly caused by human body movement is eliminated, and the accuracy of the sensor for monitoring physiological signals is enhanced. The method is applied to the fields of postoperative treatment of joint patients, man-machine interaction and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of flexible pressure sensor, in particular, relates to a kind of flexible pressure sensor with cyclic monitoring stability and preparation method thereof.It can be applied to joint patient postoperative treatment, human-computer interaction and other fields. BACKGROUND

[0002] With the advent of the Internet era, people's demand for electronic products is increasing, and flexible electronic products have gradually entered people's day, changing the way of human life. As a representative device of flexible electronics, flexible pressure sensor has great application potential in human health monitoring, human-computer interaction, biosensing and other fields. Generally speaking, the material used to make flexible pressure sensor requires enough softness and thinness, so that the sensor can better fit the human skin. In recent years, the research of flexible pressure sensor has made continuous progress, and the sensitivity and pressure range of the sensor have been improved, however, most of the flexible pressure sensors only use adhesive tape for simple fitting and fixing, which will greatly reduce the wearability and stability of the sensor. Therefore, it is crucial to design a stable, wearable and mass-produced flexible pressure sensor. SUMMARY

[0003] The present application solves the technical problem that most flexible pressure sensors only use adhesive tape for simple fitting and fixing, which will greatly reduce the wearability and stability of the sensor, and provides a flexible pressure sensor with cyclic monitoring stability and a preparation method thereof.

[0004] In order to achieve the above technical problem, the present application adopts the following technical solution: The sensor of the present application realizes the interlayer adhesion of the sensor by conductive adhesive, so that the sensor has excellent monitoring stability. The sensor is composed of a high molecular conductive adhesive, a flexible substrate with microstructure and a gold interdigital electrode. Compared with traditional rigid pressure sensors, the sensor has better wearability and is more suitable for human health monitoring. The introduction of microstructure enables the conductive adhesive to better connect the sensing layer and the electrode layer without short circuit, while enhancing the sensitivity and stability of the sensor. And the sensor is simple to prepare, and there is no too complex process, which can realize mass production.

[0005] The present application aims to provide a preparation method of a flexible pressure sensor with cyclic monitoring stability, comprising the following steps: Step 1, SEBS particles are fully dissolved in organic solvent under oil bath heating, uniformly spread on a microstructure template, and after the solvent is volatilized, the film is removed to obtain a flexible substrate with microstructure; Step 2, branched amylose and citric acid are added into deionized water, and fully dissolved at 80 ℃ to obtain a branched amylose / citric acid solution, Water is added to PVA, and after PVA is swelled for a certain time, heating is performed at 100 ℃ until fully dissolved to obtain a PVA solution, The branched amylose / citric acid solution and the PVA solution are mixed, glutaraldehyde is added, and fully stirred to be uniform, a PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate) solution is added to obtain a precursor solution; Step 3, DMSO is added to the precursor solution obtained in step 2, and after oscillation and uniform spreading, the microstructure surface of the flexible substrate obtained in step 1 is coated, and drying is performed; Step 4, then the microstructure surface treated in step 3 is drop-coated with the precursor solution, the interdigital electrode is covered on the microstructure, drying is performed, and wiring is performed to obtain the sensor. Further limitation, in step 1, the mass ratio of SEBS particles to organic solvent is 1:17-5:17.

[0006] Further limitation, in step 1, the organic solvent is toluene or tetrahydrofuran.

[0007] Further limitation, in step 1, the microstructure is a quadrangular pyramid arranged in a two-dimensional matrix.

[0008] Further limitation, in step 1, the material of the template is polytetrafluoroethylene.

[0009] Further limitation, in step 2, the mass ratio of branched amylose to citric acid in the mixed solution of branched amylose and citric acid is 10:1-1:1.

[0010] Further limitation, in step 2, the swelling time is 12 h; and the mass concentration of the PVA solution is 0.5 %-10 %.

[0011] Further limitation, in step 2, the amount of PEDOT:PSS added accounts for 0.6 %-35 % of the total mass of the precursor solution.

[0012] Further limitation, in step 2, the ratio of the PVA solution to glutaraldehyde is 0.2 g:2 μL-1.2 g:2 μL.

[0013] Further limitation, in step 2, the mass ratio of the branched amylose / citric acid solution to the PVA solution is 1:1-5:1.

[0014] Further limitation, in step 3, the mass ratio of DMSO to the precursor solution is 1:5-1:15.

[0015] Further limitation, in step 4, the drying time of the conductive layer is 24 h.

[0016] Further limited, the step 4 uses the enameled wire to make the sensor wiring, mainly using a scalpel to carefully cut off the protective paint of the copper wire outer layer, and then use the conductive tape to fix the copper wire and the interface of the interdigital electrode.

[0017] Another object of the present application is to provide a flexible pressure sensor prepared by any of the above-mentioned methods.

[0018] Compared with the prior art, the present application has the following beneficial effects: The present application uses a template method to prepare a flexible SEBS substrate with a prism microstructure, and uses branched amylose, citric acid, PEDOT:PSS and PVA to prepare a conductive adhesive for interlayer adhesion of the sensing layer, thereby enhancing the stability of the sensor. Using flexible materials such as branched amylose and PVA as adhesives, the Young's modulus of the adhesive itself is much lower than that of common rigid adhesives, thereby effectively reducing the impact of the adhesive on the sensing performance of the sensor. After connecting the sensing layer and the electrode layer of the sensor through the adhesive, not only the sensor structure is simplified, but also the sensor is more easily worn, and the anti-interference performance of the sensor is enhanced, the relative displacement of the sensor structure caused by human body movement is eliminated, and the accuracy of the sensor in monitoring physiological signals is enhanced.

[0019] In order to further understand the features and technical contents of the present application, please refer to the following detailed description of the present application and the accompanying drawings, however, the accompanying drawings are provided for reference and illustration only, and are not used to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The present application is an embodiment of the step schematic diagram, Figure 1 (a) is a schematic diagram of the SEBS flexible substrate with a microstructure according to the present application, Figure 1 (b) is a schematic diagram of the flexible substrate with a deposited conductive layer according to the present application, Figure 1 (c) is a schematic diagram of the conductive adhesive coated on the microstructure according to the present application, Figure 1 (d) is a schematic diagram of the assembled sensor according to the present application; wherein, 1-SEBS flexible substrate, 2-prism microstructure on the flexible substrate, 3-conductive adhesive doped with DMSO used as a conductive layer, 4-conductive adhesive, 5-gold interdigital electrode, 6-enameled copper wire; Figure 2 The sensing mechanism of the sensor; Figure 3 The effect diagram of the sensor 10000 times of cycle detection; Figure 4 The effect diagram of the sensor detecting the bending amplitude of the human finger. DETAILED DESCRIPTION

[0021] The application will be described in detail below with specific examples. The following examples will help those skilled in the art to further understand the patent of the application, and at the same time, do not limit the application in any form. It should be pointed out that, for those skilled in the art, without departing from the concept of the patent of the application, a number of modifications and improvements can also be made. These all belong to the protection scope of the patent of the application.

[0022] Example 1: The preparation method of the flexible pressure sensor with monitoring stability is completed by the following steps: Specifically, the application is to prepare a flexible SEBS substrate with microstructure by template method, then prepare a branched amylose / citric acid mixed solution and a PVA solution, take one part of each of the two to prepare a conductive adhesive by mixing with PEDOT:PSS, take a part of the conductive adhesive and mix with DMSO, then uniformly spread on the flexible substrate to prepare a conductive layer, then connect the microstructure and the interdigital electrode by using the conductive adhesive, and finally use the enameled copper wire to connect the interface of the interdigital electrode to complete the production of the flexible pressure sensor. The specific features of the flexible pressure sensor production method provided by the application will be further described below in combination with the drawings: Step 1, flexible substrate with microstructure: mix SEBS particles and toluene according to the mass ratio of 3:17 and heat to dissolve at 40 ℃, then uniformly spread the solution on a polytetrafluoroethylene plate with microstructure (a two-dimensional matrix arranged four-prism, the bottom of the prism is a square of 2x2 mm, the top is a square of 1x1 mm, the prism is 1 mm high, and the distance between adjacent prisms is 2 mm). After the solvent evaporates, the cured flexible substrate is removed, and a flexible SEBS substrate with microstructure is obtained. Figure 1 a) Step 2, preparation of conductive adhesive precursor: take 1 g of branched amylose and 0.5 g of citric acid, add 5 g of deionized water and dissolve at 80 ℃; obtain a branched amylose / citric acid solution, then take 1 g of PVA and put it into 10 g of deionized water to swell for 12 h, then heat and dissolve at 100 ℃, obtain a PVA solution, take 1.6 g of branched amylose / citric acid solution and 0.8 g of PVA solution, mix and add 2 μL of glutaraldehyde and 1.6 g of PEDOT:PSS to complete the preparation of the conductive adhesive precursor.

[0023] Step 3, Preparation of Conductive Layer: Take 0.2 g of conductive adhesive and then add 0.02 g of DMSO. Mix the two evenly with an oscillator and spread on a flexible SEBS substrate. Dry at room temperature for 24 hours. The conductivity of the conductive adhesive after adding DMSO is greatly improved and the adhesion performance is reduced, making it suitable for making a conductive layer. (See Figure 1 b) Step 4: Assemble the sensor: Apply a conductive adhesive precursor solution on the pyramidal microstructure, and cover the microstructure with evaporated gold interdigital electrodes. Then, place the entire sensor in an oven at 60°C for 4 hours. After drying, use enameled copper wire and conductive glue to connect the interdigital electrode interface to complete the fabrication of the flexible pressure sensor (see Figure 1 c, d).

[0024] The effect of the sensor's 10,000 cycle test is shown in the figure below. Figure 3 As shown by Figure 3 It can be seen that during the 10,000 pressure cycle detection process of the sensor, the overall signal output of the sensor is very stable, reflecting the excellent cycle monitoring stability of the sensor.

[0025] The effect of the sensor detecting the bending amplitude of human fingers is shown in the figure Figure 4 As shown, by Figure 4 It can be seen that when the human fingers are bent to different degrees, the pressure exerted by the finger joints on the sensor changes, causing the current signal output by the sensor to change. As the finger bending amplitude increases, the signal output of the sensor also increases accordingly. The current signals corresponding to different bending amplitudes are quite different, which can achieve accurate identification of different joint bending amplitudes.

[0026] The present invention is not limited to the specific embodiments described above. Those skilled in the art may make various modifications, additions, or substitutions to the specific embodiments described, without departing from the spirit of the present invention or exceeding the scope defined by the appended claims, and all such modifications and additions are within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a flexible pressure sensor with cyclic monitoring stability, characterized in that: The following steps are involved: Step 1: Fully dissolve SEBS particles in an organic solvent under oil bath heating, evenly spread on a template with a microstructure, and peel off the film after the solvent evaporates to obtain a flexible substrate with a microstructure; Step 2: Add amylopectin and citric acid into deionized water and fully dissolve them at 80°C to obtain amylopectin / citric acid solution. Add water to PVA, wait for PVA to swell for a certain period of time, and then heat at 100°C until it is fully dissolved to obtain a PVA solution. The pullulan / citric acid solution and the PVA solution were mixed, glutaraldehyde was added, the mixture was thoroughly stirred, and the PEDOT:PSS solution was added to obtain a precursor solution; Step 3, adding DMSO to the precursor solution obtained in step 2, shaking and spreading it evenly on the microstructure surface of the flexible substrate obtained in step 1, and drying; Step 4: Then, the precursor solution is drop-coated on the surface of the microstructure treated in step 3, and interdigital electrodes are covered on the microstructure, dried, and connected to obtain the sensor.

2. The method according to claim 1, characterized in that The mass ratio of SEBS particles to organic solvent is 3:17, and the organic solvent is toluene or tetrahydrofuran.

3. The method according to claim 1, characterized in that The microstructure is a quadrangular pyramid arranged in a two-dimensional matrix, and the template material is polytetrafluoroethylene.

4. The method according to claim 1, wherein The mass ratio of amylopectin to citric acid is 10:1 to 1:

1.

5. The method according to claim 1, wherein Swelling for 12 h; the mass concentration of the PVA solution is 0.5% to 10%.

6. The method according to claim 1, characterized in that The amount of PEDOT:PSS added accounts for 0.6% to 35% of the total mass of the precursor solution.

7. The method according to claim 1, characterized in that The ratio of PVA solution to glutaraldehyde is 0.2 g:2 μL to 1.2 g:2 μL.

8. The method according to claim 1, characterized in that The mass ratio of pullulan / citric acid solution to PVA solution is 1:1 to 5:

1.

9. The method according to claim 1, characterized in that The mass ratio of DMSO to precursor solution is 1:5 to 1:

15.

10. A flexible pressure sensor prepared by the method according to any one of claims 1 to 9.

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