Electrochemical pressure sensor based on polyelectrolyte gel and preparation method thereof

Abstract

The invention discloses an electrochemical pressure sensor based on polyelectrolyte gel and a preparation method thereof, and belongs to the technical field of pressure-sensitive elements and pressure sensors. The electrochemical pressure sensor comprises a polyelectrolyte gel pressure sensitive layer, a positive electrode and a negative electrode, wherein the surface of the polyelectrolyte gel pressure sensitive layer is provided with a bowl-shaped groove array structure; the positive electrode is positioned on the upper surface of the pressure sensitive layer; the negative electrode is positioned on the lower surface of the pressure sensitive layer; the polyelectrolyte gel pressure sensitive layer comprises PVA, LiCl and PSS. The surface bowl-shaped groove array structure prepared by using the nucleation effect has excellent pressure-sensitive performance: on one hand, the sensitivity of contact between polyelectrolyte gel and an electrode to pressure is improved, so that the sensor realizes excellent pressure response characteristic; and on the other hand, the surface microstructure gel electrolyte preparation method with less damage to the mold and wider applicability is realized. The electrochemical pressure sensor provided by the invention has the characteristics of high response rate and high output power, and has important value for development of high-performance self-energized pressure sensors.

Description

Technical Field

[0001] The present invention belongs to the technical field of pressure-sensitive elements and pressure sensors, and in particular relates to an electrochemical pressure sensor based on polyelectrolyte gel and a preparation method thereof. Background Art

[0002] A power-generating pressure sensor is a pressure sensor that can simultaneously detect pressure and generate electrical energy, achieving low or even zero power consumption during the detection process. As a cutting-edge solution for future self-functional pressure sensing technology, power-generating pressure sensors are rapidly developing. Chinese patent application publication number CN 112600460 A discloses a power-generating pressure sensor based on the postbuckling phenomenon. This pressure sensor, based on the piezoelectric effect, can detect pressure without an additional power supply. While piezoelectric pressure sensors can convert mechanical energy into electrical energy, their output voltage is low, and their power generation performance is limited by external mechanical energy stimulation, making it difficult to accurately monitor static pressure. Chinese patent application publication number CN116698233 A discloses a washable, power-generating, flexible, and highly stretchable sensor device and its preparation method. This device, based on the principle of triboelectric sensing, generates electricity while sensing pressure. While triboelectric nanogenerator pressure sensors have higher power generation than piezoelectric pressure sensors, their power generation performance still relies on external mechanical energy stimulation, making it difficult to accurately monitor static pressure. Chinese patent application publication number CN 108801509 A discloses a gradient-structured ion-type pressure sensor and its fabrication process. Based on the principle of ion diffusion power generation, the device can simultaneously generate electricity and accurately detect static pressure. While the sensor can monitor static pressure, its power generation capacity is relatively low and it is significantly affected by ambient humidity.

[0003] In recent years, in order to solve the technical problems of the above-mentioned power generation pressure sensor, an electrochemical pressure sensor based on the battery principle has been developed. The electrochemical pressure sensor uses redox reaction to generate continuous electrical energy output, and realizes pressure monitoring by regulating ion transmission through external pressure, which has greater performance improvement potential. The Chinese patent application with publication number CN115371855 A discloses an electrochemical pressure sensor and its preparation method, which has the ability to detect static pressure while ensuring excellent power generation capacity, realizing self-driven pressure sensing. However, in order to take into account both pressure sensitivity and power generation characteristics, the pressure-sensitive material and electrolyte material of the above-mentioned electrochemical pressure sensor use different materials, which increases the complexity of the structure.

[0004] Gel electrolytes are an important class of electrolyte materials in the battery field. Their plastic shape enables improved pressure-sensitive performance through appropriate mechanical structural design. Furthermore, ion gels possess excellent mechanical properties and high ionic conductivity, potentially serving as both pressure-sensitive and electrolyte materials. Chinese patent application publication number CN 119779519 A discloses a battery-type pressure sensor, its preparation method, and application. The patent proposes a pressure sensor in which an elastic ion gel electrolyte acts as both an electrolyte and a pressure-sensitive material. This prior art demonstrates the use of a molding method to prepare gel electrolytes with varying surface structures. However, the flexible molds used in this method are susceptible to aging due to deformation or surface adhesion, resulting in reduced microstructure replication accuracy. Furthermore, this method requires the precursor solution to have low viscosity and good fluidity to fill the mold microcavities, which imposes significant limitations on its use. Therefore, a method for preparing surface microstructured gel electrolytes with less mold damage and wider applicability is needed. Furthermore, power generation is a key performance indicator of power-generating sensors, and the power generation of electrochemical pressure sensors is affected by the ionic conductivity of the electrolyte material. The high ionic conductivity of the hydrogel requires sufficient water content. Too high a water content will result in insufficient mechanical strength of the hydrogel, thereby limiting the detection range of the sensor. Summary of the Invention

[0005] The purpose of the present invention is to overcome the technical problem that gel electrolyte cannot take into account both ionic conductivity and mechanical strength as a pressure-sensitive electrolyte material for electrochemical pressure sensors, and to provide an electrochemical pressure sensor based on polyelectrolyte gel and a preparation method thereof, so that the gel electrolyte can serve as both an ion conductor and a pressure-sensitive layer. At the same time, in order to improve the shortcomings of the existing molding method for preparing pressure-sensitive microstructures in terms of mold damage and applicability, a new method for preparing periodic pressure-sensitive microstructures is provided.

[0006] The technical problem proposed by the present invention is solved as follows:

[0007] A polyelectrolyte gel-based electrochemical pressure sensor comprises a positive electrode 1, a polyelectrolyte gel pressure-sensitive layer 2, and a negative electrode 3; the positive electrode 1 and the negative electrode 3 are respectively arranged on the upper and lower surfaces of the polyelectrolyte gel pressure-sensitive layer 2 to form a sandwich structure; the polyelectrolyte gel pressure-sensitive layer 2 acts as an electrolyte to conduct metal ions and hydrogen ions between the positive electrode 1 and the negative electrode 3, and regulates ion conduction to achieve pressure response when subjected to external pressure; the positive electrode 1 and the negative electrode 3 respectively output electrical signals to an external signal processing circuit through wires to achieve pressure detection.

[0008] Furthermore, the positive electrode is copper foil, and the negative electrode is zinc foil.

[0009] Furthermore, the polyelectrolyte gel pressure sensitive layer 2 is a PVA / LiCl / PSS polyelectrolyte gel, where / represents and, and the bottom surface has a bowl-shaped groove array structure.

[0010] The present invention provides a method for preparing a polyelectrolyte gel pressure-sensitive layer, comprising the following steps:

[0011] Step 1: Preparing a precursor solution: PVA particles, LiCl powder, and deionized water are mixed, and heated and stirred on a stirring table at a stirring speed to obtain a PVA / LiCl mixed solution as a precursor solution;

[0012] Step 2, preparing a pregel solution, adding a PSS solution dropwise into the precursor solution, and sonicating in an ultrasonicator to obtain a PVA / LiCl / PSS mixed solution as a pregel solution;

[0013] Step 3: Drying and cross-linking: Pour the pre-gel solution into the mold and place it in a drying oven to dry for cross-linking reaction;

[0014] Step 4: Peeling and cooling: peeling the cross-linked polyelectrolyte gel from the mold and letting it stand at room temperature for 1 hour to obtain a polyelectrolyte gel with a bowl-shaped groove array structure on the bottom surface.

[0015] Furthermore, the mass ratio of the PVA particles to the LiCl powder in step 1 is (1-4):1, and the mass ratio of the PVA particles to the deionized water is (1-4):8.

[0016] Furthermore, the heating and stirring time in step 1 is 1 to 3 hours, the heating temperature is 70 to 95° C., and the rotation speed is 400 to 800 rpm.

[0017] Furthermore, the volume ratio of the PSS solution to the precursor solution in step 2 is (1-4):4.

[0018] Furthermore, the ultrasonication time in step 2 is 1 to 2 hours.

[0019] Furthermore, the groove size of the mold in step 3 is 10mm*10mm*2.5mm, and the bottom has a 10*10 periodically arranged conical groove array, the conical groove is 0.5-1mm deep, and the groove mouth diameter is 300-600μm.

[0020] Furthermore, the drying temperature in step 3 is 70-90° C., and the drying time is 8-16 hours.

[0021] Furthermore, during the drying and crosslinking process in step 3, the nucleation effect is used to control the generation of bubbles in the pre-gel solution at the conical grooves, thereby preparing a microstructured polyelectrolyte gel with a bowl-shaped groove array structure on the bottom surface as the polyelectrolyte gel pressure-sensitive layer 2.

[0022] The present invention also provides a method for preparing an electrochemical pressure sensor based on a polyelectrolyte gel, comprising the following steps:

[0023] Step 1: fix the positive electrode 1 and the negative electrode 3 on the upper and lower surfaces of the polyelectrolyte gel pressure sensitive layer 2;

[0024] Step 2: Use PI tape for packaging to complete the preparation of the electrochemical pressure sensor.

[0025] Furthermore, the width of the positive electrode 1 and the negative electrode 3 in step 1 is 10 mm.

[0026] The beneficial effects of the present invention are:

[0027] In the electrochemical pressure sensor based on the polyelectrolyte gel described in the present invention, the bowl-shaped groove array structure on the surface of the polyelectrolyte gel can increase the effect of the applied pressure on the charge transfer process between the gel electrolyte and the electrode, thereby improving the response characteristics of the electrochemical pressure sensor.

[0028] In the method for preparing the polyelectrolyte gel pressure-sensitive layer of the present invention, the method for preparing the polyelectrolyte gel surface with a surface bowl-shaped groove array structure utilizing the nucleation effect causes less damage to the mold and has wider applicability.

[0029] In the preparation method of the polyelectrolyte gel pressure-sensitive layer of the present invention, LiCl and PSS are used as additives to improve the conductivity of the polyelectrolyte gel while optimizing the mechanical properties of the polyelectrolyte gel, effectively improving the output power and mechanical response of the electrochemical pressure sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of the electrochemical pressure sensor of the present invention;

[0031] Figure 2 Schematic diagram of a method for preparing a polyelectrolyte gel pressure-sensitive layer in the electrochemical pressure sensor of the present invention;

[0032] Figure 3 Response / recovery curves of the electrochemical pressure sensor of the present invention under different pressures;

[0033] Figure 4 The response fitting curves of the electrochemical pressure sensor of the present invention under different pressures;

[0034] Figure 5 This is a graph showing the response of the electrochemical pressure sensor of the present invention to 4000 cycles at a pressure of 100 kPa;

[0035] Figure 6The relationship curve between the output voltage and current of the electrochemical pressure sensor of the present invention and the load resistance at a pressure of 200 kPa is shown;

[0036] Figure 7 The relationship curve between the output power and the load resistance of the electrochemical pressure sensor of the present invention at a pressure of 200 kPa is shown;

[0037] Figure 8 This is a schematic diagram of the application of the electrochemical pressure sensor of the present invention for detecting the bending angle of a finger;

[0038] Figure 9 This is a schematic diagram of the application of the electrochemical pressure sensor of the present invention for Morse code transmission. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings and examples.

[0040] This embodiment provides an electrochemical pressure sensor based on a polyelectrolyte gel, which solves the contradiction between ion conductivity and detection range, innovates the ion gel material system, and achieves high ion conductivity while achieving excellent mechanical strength.

[0041] The structural diagram of the electrochemical pressure sensor based on polyelectrolyte gel described in this embodiment is shown in FIG. Figure 1 As shown, it includes a positive electrode 1, a polyelectrolyte gel pressure-sensitive layer 2 and a negative electrode 3; the positive electrode 1 and the negative electrode 3 are respectively arranged on the upper and lower surfaces of the polyelectrolyte gel pressure-sensitive layer 2 to form a sandwich structure; the polyelectrolyte gel pressure-sensitive layer 2 acts as an electrolyte to conduct metal ions and hydrogen ions between the positive and negative electrodes, and at the same time, regulates ion conduction to achieve pressure response when subjected to external pressure; the positive electrode 1 and the negative electrode 3 respectively output electrical signals to an external signal processing circuit through wires to achieve pressure detection.

[0042] In this embodiment, the positive electrode is copper foil, and the negative electrode is zinc foil.

[0043] In this embodiment, the polyelectrolyte gel pressure-sensitive layer 2 is a PVA / LiCl / PSS polyelectrolyte gel, where / represents and, and the bottom surface has a bowl-shaped groove array structure. The three-dimensional network structure of the PVA polyelectrolyte gel provides excellent pressure-sensitive response potential. PSS and LiCl synergistically regulate the morphology of the PVA gel while simultaneously increasing the ionic conductivity of the polyelectrolyte gel, significantly improving the sensor's output power and pressure sensing performance, enabling the gel electrolyte to function as both an ion conductor and a pressure-sensitive layer.

[0044] This embodiment provides a method for preparing a polyelectrolyte gel pressure-sensitive layer, comprising the following steps:

[0045] Step 1: Preparing a precursor solution: PVA (Polyvinyl Alcohol) particles, LiCl (lithium chloride) powder, and deionized water are mixed and heated and stirred on a stirring table at a stirring speed to obtain a PVA / LiCl mixed solution as a precursor solution;

[0046] Step 2: Preparing a pregel solution: adding a PSS solution (Polystyrene Sulfonic Acid) to the precursor solution, and sonicating the solution in an ultrasonicator to obtain a PVA / LiCl / PSS mixed solution as the pregel solution.

[0047] Step 3: Drying and cross-linking: Pour the pre-gel solution into the mold and place it in a drying oven to dry for cross-linking reaction;

[0048] Step 4: Peel and cool. Peel the cross-linked polyelectrolyte gel from the mold and let it stand at room temperature for 1 hour to obtain a polyelectrolyte gel with a bowl-shaped groove array structure on the bottom surface, which serves as the polyelectrolyte gel pressure-sensitive layer.

[0049] In this embodiment, the mass ratio of PVA particles, LiCl powder and deionized water in step 1 is 2:1:17;

[0050] In this embodiment, the heating and stirring time in step 1 is 2 hours, the heating temperature is 95°C, and the rotation speed is 600 rpm;

[0051] In this embodiment, the volume ratio of the PSS solution to the precursor solution in step 2 is 3:4;

[0052] In this embodiment, the ultrasonic time in step 2 is 2 hours;

[0053] In this embodiment, the groove size of the mold in step 3 is 10mm*10mm*2.5mm, and the bottom has a 10*10 periodic array of conical grooves. The conical groove is 1mm deep and the groove mouth diameter is 360μm.

[0054] In this embodiment, the drying temperature in step 3 is 80° C. and the drying time is 12 hours.

[0055] In this embodiment, the preparation method of the polyelectrolyte gel pressure sensitive layer based on the nucleation effect is as follows: Figure 2 As shown, during the drying and cross-linking process in step 3, the nucleation effect is used to control the generation of bubbles in the pre-gel solution at the conical grooves, thereby preparing a microstructured polyelectrolyte gel with a bowl-shaped groove array structure on the bottom surface.

[0056] This embodiment also provides a method for preparing an electrochemical pressure sensor based on a polyelectrolyte gel, comprising the following steps:

[0057] Step 1: fix the positive electrode 1 and the negative electrode 3 on the upper and lower surfaces of the polyelectrolyte gel pressure sensitive layer 2 to form a sandwich structure;

[0058] Step 2: Use PI tape to encapsulate the sandwich structure to complete the preparation of the electrochemical pressure sensor.

[0059] In this embodiment, the width of the positive electrode 1 and the negative electrode 3 in step 1 is 10 mm.

[0060] The working mechanism of the electrochemical pressure sensor based on the polyelectrolyte gel described in this embodiment can be explained by the effect of pressure on the polyelectrolyte gel pressure-sensitive layer and the electrochemical reaction. The difference in the activity of the metal leads to a spontaneous redox reaction inside the sensor. Since the work function of the zinc negative electrode (4.30eV) is smaller than the work function of the copper positive electrode (4.65eV), electrons are more likely to escape from the zinc negative electrode. The flow of electrons will cause charge imbalance and promote the migration of ions in the polyelectrolyte gel, thereby generating a continuous current. Specifically, a reduction reaction occurs on the copper positive electrode, and the chemical reaction equation is as follows:

[0061] 2H + +2e - →H2

[0062] An oxidation reaction occurs on the zinc negative electrode, and the chemical reaction equation is as follows:

[0063] Zn→Zn 2+ +2e -

[0064] Therefore, the overall reaction equation of the electrochemical pressure sensor based on the polyelectrolyte gel described in this embodiment can be obtained as follows:

[0065] Zn+2H + →Zn 2+ +H2

[0066] According to the power calculation formula (P = U 2 / R), the output power of the sensor can be increased by reducing the internal resistance. In the electrochemical pressure sensor based on the polyelectrolyte gel described in this embodiment, the alkali metal salt LiCl constituting the polyelectrolyte gel has high solubility and strong dissociation characteristics, which can provide free Li + and Cl - , enhance ionic conductivity and reduce internal resistance. The densely distributed sulfonic acid groups (-SO3H) on the polyelectrolyte PSS polymer chain can dissociate into sulfonate ions (-SO3 - ) and H + , respectively used for Li +The electrodes and the pressure-sensitive electrolyte provide abundant hopping sites to accelerate the transmission efficiency, enhance proton conduction, improve the conductivity of the polyelectrolyte gel, and reduce the internal resistance. Therefore, the output power of the electrochemical humidity sensor is improved under the combined action of the electrode and the pressure-sensitive electrolyte.

[0067] The performance of the electrochemical pressure sensor based on the polyelectrolyte gel described in this example was tested according to methods disclosed in the art. Specifically, different pressures of 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, and 200 kPa were applied to the electrochemical pressure sensor prepared above using a ZQ-990B universal tensile and compressive testing machine, and the response voltage of the electrochemical pressure sensor was tested using a KEITHLEY 6500 digital multimeter.

[0068] The response / recovery curves of the electrochemical pressure sensor based on polyelectrolyte gel at different pressures are shown in FIG. Figure 3 As shown, it can be seen that it has a wide range (0.1-200kPa) and high resolution (low pressure area).

[0069] The response fitting curves of the electrochemical pressure sensor based on polyelectrolyte gel at different pressures described in this embodiment are as follows: Figure 4 As shown, it can be seen that it has a wide pressure detection range (0.1-200kPa), high sensitivity (0.1-60kPa range 0.0669kPa -1 , 60-200kPa range 0.0255kPa -1 ) and high response value (response value 751.3 at 200kPa).

[0070] The response of the electrochemical pressure sensor based on polyelectrolyte gel in this embodiment to 4000 cycles under 100 kPa pressure is shown in FIG. Figure 5 As shown, it can be seen that the electrochemical pressure sensor described in this embodiment has good repeatability.

[0071] Figure 5 The response / recovery curve of the electrochemical pressure sensor based on the polyelectrolyte gel described in this embodiment under a pressure of 100 kPa is also shown. It can be seen that the response / recovery time of the electrochemical pressure sensor described in this embodiment is 509 / 655 ms, which has a fast response recovery speed.

[0072] The relationship between the output voltage and current of the electrochemical pressure sensor based on polyelectrolyte gel at a pressure of 200 kPa and the load resistance is as follows: Figure 6 As shown, it can be seen that the electrochemical pressure sensor described in this embodiment has a high open circuit voltage (0.786V) and a high short circuit current (238.23μA).

[0073] The output power curves of the electrochemical pressure sensor based on polyelectrolyte gel in this embodiment under different load resistances are shown in FIG. Figure 7 As shown, it can be seen that the electrochemical pressure sensor described in this embodiment has a high output power (47.3 μW).

[0074] The electrochemical pressure sensor based on polyelectrolyte gel described in this embodiment is used for finger bending angle detection. Figure 8 As shown, it can be seen that the electrochemical pressure sensor described in this example can produce different responses to different bending angles of the finger.

[0075] The electrochemical pressure sensor based on the polyelectrolyte gel described in this embodiment is used for Morse code transmission applications such as Figure 9 As shown, it can be seen that the Morse code of English letters can be simulated by alternately long pressing and short pressing the electrochemical pressure sensor described in this example.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An electrochemical pressure sensor based on polyelectrolyte gel, characterized in that: The invention comprises a positive electrode (1), a polyelectrolyte gel pressure-sensitive layer (2) and a negative electrode (3); the positive electrode (1) and the negative electrode (3) are respectively arranged on the upper and lower surfaces of the polyelectrolyte gel pressure-sensitive layer (2) to form a sandwich structure; the polyelectrolyte gel pressure-sensitive layer (2) acts as an electrolyte to conduct metal ions and hydrogen ions between the positive electrode (1) and the negative electrode (3), and regulates ion conduction to achieve pressure response when subjected to external pressure; the positive electrode (1) and the negative electrode (3) respectively output electrical signals to an external signal processing circuit through wires to achieve pressure detection.

2. The electrochemical pressure sensor based on polyelectrolyte gel according to claim 1, characterized in that The positive electrode (1) is a copper foil, and the negative electrode (3) is a zinc foil.

3. The electrochemical pressure sensor based on polyelectrolyte gel according to claim 1, characterized in that The polyelectrolyte gel pressure sensitive layer (2) is a PVA / LiCl / PSS polyelectrolyte gel, where / represents and, and the bottom surface has a bowl-shaped groove array structure.

4. A method for preparing a polyelectrolyte gel pressure-sensitive layer, for preparing the polyelectrolyte gel pressure-sensitive layer according to claim 1, characterized in that: The following steps are involved: Step 1: Preparing a precursor solution: PVA particles, LiCl powder, and deionized water are mixed, and heated and stirred on a stirring table at a stirring speed to obtain a PVA / LiCl mixed solution as a precursor solution; Step 2, preparing a pregel solution, adding a PSS solution dropwise into the precursor solution, and sonicating in an ultrasonicator to obtain a PVA / LiCl / PSS mixed solution as a pregel solution; Step 3: Drying and cross-linking: Pour the pre-gel solution into the mold and place it in a drying oven to dry for cross-linking reaction; Step 4: Peeling and cooling, peeling the cross-linked polyelectrolyte gel from the mold, and letting it stand at room temperature for 1 hour to obtain a polyelectrolyte gel with a bowl-shaped groove array structure on the bottom surface, which serves as the polyelectrolyte gel pressure sensitive layer (2).

5. The method for preparing a polyelectrolyte gel pressure sensitive layer according to claim 4, characterized in that: The groove size of the mold in step 3 is 10mm*10mm*2.5mm, and the bottom has a conical groove array arranged in a 10*10 period. The conical groove is 0.5-1mm deep and the groove mouth diameter is 300-600μm.

6. The method for preparing a polyelectrolyte gel pressure sensitive layer according to claim 5, characterized in that: During the drying and cross-linking process in step 3, the nucleation effect is used to control the generation of bubbles in the pre-gel solution at the conical grooves, thereby preparing a microstructured polyelectrolyte gel with a bowl-shaped groove array structure on the bottom surface.

7. The method for preparing a polyelectrolyte gel pressure sensitive layer according to claim 4, characterized in that: The mass ratio of the PVA particles to the LiCl powder in step 1 is (1-4):1, and the mass ratio of the PVA particles to the deionized water is (1-4):

8.

8. The method for preparing a polyelectrolyte gel pressure-sensitive layer according to claim 4, characterized in that: The heating stirring time in step 1 is 1 to 3 hours, the heating temperature is 70 to 95°C, and the rotation speed is 400 to 800 rpm; the volume ratio of the PSS solution to the precursor solution in step 2 is (1 to 4):4; the ultrasonic time in step 2 is 1 to 2 hours; the drying temperature in step 3 is 70 to 90°C, and the drying time is 8 to 16 hours.

9. A method for preparing an electrochemical pressure sensor based on polyelectrolyte gel, characterized in that: The following steps are involved: Step 1: fixing the positive electrode (1) and the negative electrode (3) on the upper and lower surfaces of the polyelectrolyte gel pressure-sensitive layer (2) prepared according to claim 4; Step 2: Use PI tape for packaging to complete the preparation of the electrochemical pressure sensor.

10. The method for preparing an electrochemical pressure sensor based on polyelectrolyte gel according to claim 9, characterized in that: The width of the positive electrode (1) and the negative electrode (3) in step 1 is 10 mm.

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