Preparation method of bionic gradient gel ionization sensor and sensor thereof

Abstract

The invention relates to a preparation method of a bionic gradient gel ionization sensor. The preparation method comprises the following steps: (1) designing a hierarchical pyramid microstructure mold drawing by using 3D max software; (2) importing the designed pyramid microstructure pattern into 3D printing software to obtain a graded pyramid microstructure mold; (3) PDMS is poured on the graded pyramid microstructure mold; and (4) obtaining the graded pyramid microstructure Au-PDMS electrode. (5) preparing a sol solution of the ATMP-PVA hydrogel; (6) obtaining hydrogels with different moduli; (7) cutting the hydrogel with different moduli and constructing a gradient gel structure; and (8) forming a sandwich structure by using the graded pyramid microstructure Au-PDMS electrode and the gradient gel dielectric layer to form a gradient gel ionization sensor, and packaging by using a PI adhesive tape. The preparation method has the advantages that an electric double layer (EDL) is formed on an interface between the micro-pyramid structure and the gradient gel, and excellent capacitance characteristics and remarkable capacitance response are shown.

Description

Technical Field

[0001] The invention relates to a preparation method of a bionic gradient gel ionization sensor and the sensor thereof, belonging to the field of electronic devices. Background Art

[0002] With the rapid development of intelligent robots and wearable medical technologies, the performance requirements for flexible pressure sensors are constantly increasing. An ideal flexible pressure sensor should have comprehensive characteristics such as high sensitivity, high linearity, and a wide pressure sensing range. High sensitivity enables the sensor to detect tiny mechanical stimuli, while linear signals facilitate signal processing using simplified circuits and respond to stimuli more accurately. Compared with sensors with a narrow sensing range, sensors with a wider range of application scenarios are more popular. Traditional sensor processing involves complex multi-step processes, which not only increases production costs but also leads to low production efficiency.

[0003] At the same time, existing sensors have the following drawbacks: Traditional flexible pressure sensors often find it difficult to achieve both high sensitivity and a wide pressure sensing range. High sensitivity means that the sensor can detect tiny pressure changes, while wide range detection means that the sensor can respond to pressure changes from slight to large. The balance between the two is a challenge in existing technologies.

[0004] If the sensor’s output signals are not linear, more complex circuits or algorithms are required in the signal processing stage to convert and interpret these signals, which not only increases costs but may also result in longer response times and reduced accuracy. Summary of the invention

[0005] In order to overcome the defects of the prior art, the present invention is inspired by the gradient elastic modulus distribution of human skin and proposes a groundbreaking ionization sensor of gradient elastic modulus hydrogel layer, which can precisely control the hydrogel modulus by using the Hofmeister effect. Using a hierarchical micro-pyramid structure, a bionic gradient gel ionization sensor (BGGITS) was successfully constructed. The bionic design based on BGGITS provides a new strategy for manufacturing tactile sensors with wide range pressure perception.

[0006] The present invention provides a method for preparing a bionic gradient gel ionization sensor. The technical solution of the present invention is:

[0007] A method for preparing a biomimetic gradient gel ionization sensor comprises the following steps:

[0008] (1) Using 3D max software to design a hierarchical pyramid microstructure mold diagram, four hierarchical pyramid microstructure electrodes are prepared on each mold at the same time, and three pyramid microstructure molds of different heights are distributed in each mold;

[0009] (2) importing the designed pyramid microstructure pattern into 3D printing software, using photosensitive resin as the 3D printing material, the photosensitive resin is heated and melted and flows out of the nozzle, and is formed according to the designed shape to obtain a graded pyramid microstructure mold;

[0010] (3) pouring PDMS on the hierarchical pyramid microstructure mold, and using a glue machine to spin coat to make the PDMS evenly spread; then using a vacuum plasma cleaning machine to treat the PET-ITO conductive film to increase its affinity, and then covering the hierarchical pyramid microstructure mold with the PET-ITO conductive film, curing and demolding;

[0011] (4) evaporating an Au layer on the surface of the hierarchical pyramid microstructure PDMS electrode to obtain a hierarchical pyramid microstructure Au-PDMS electrode;

[0012] (5) preparing a sol of ATMP-PVA hydrogel by a one-pot method, dripping the sol onto a gel mold, and freezing to obtain an ATMP-PVA gel;

[0013] (6) Rapidly immersing the ATMP-PVA gel in a salt solution to cause the gel to produce a Hofmeister effect in the salt solution, thereby obtaining hydrogels with different moduli;

[0014] (7) Cutting hydrogels with different moduli and constructing gradient gel structures;

[0015] (8) The hierarchical pyramid microstructured Au-PDMS electrode and the gradient gel dielectric layer are combined into a sandwich structure to form a gradient gel ionization sensor, which is then encapsulated with PI tape.

[0016] In the step (1), the overall size of the graded pyramid microstructure mold is 32.4mm*32.4mm, and the size of each graded pyramid microstructure electrode is 13.2mm*13.2mm; three pyramid microstructures of different heights are distributed in the graded pyramid microstructure mold, with sizes of 1mm, 0.8mm, and 0.6mm respectively, and the bottom edge length is 1mm, which is arranged periodically.

[0017] In the step (2), the nozzle temperature is set to 270°C.

[0018] In the step (3), the PDMS is prepared by the following steps: mixing the PDMS stock solution and the curing agent in a mass ratio of 10:1, and fully stirring, and then placing the mixture in a vacuum pump and evacuating for 50 minutes; the size of the PET-ITO conductive film is 1.5 cm×3 cm; during curing and demolding, after curing at room temperature for 1 hour, the film is heated at 50°C in a forced air drying oven for 5 hours and then demolded.

[0019] In the step (4), the layered pyramid microstructure PDMS electrode is placed in a high vacuum resistance evaporation coating device, and a 100 nm thick Au layer is evaporated on the surface of the electrode.

[0020] In the step (5), PVA, ATMP and H2O are mixed in a volume ratio of 4:10:30 and placed in a 105°C oil bath for reaction for 2 hours to form a sol solution; when freezing, it is frozen at -18°C for 24 hours to obtain ATMP-PVA gel.

[0021] In the step (6), the ATMP-PVA gel is rapidly immersed in various salt solutions for 12 hours.

[0022] In the step (7), gels of different moduli are cut into a size of 1.5 cm×1.5 cm, the hardest and softest hydrogels are selected as the upper and lower layers of the gradient gel, and the middle layer is selected according to actual needs to construct gradient gel structures of different combinations.

[0023] A bionic gradient gel ionization sensor is prepared by the preparation method of the bionic gradient gel ionization sensor.

[0024] The advantages of the present invention are:

[0025] 1. The interface between the micro-pyramid structure and the gradient gel forms an electric double layer (EDL), which exhibits excellent capacitive properties and significant capacitive response;

[0026] 2. The linear response is mainly attributed to the gradient micro-pyramids of different heights. As the external pressure increases, the pyramids of different heights contact the gel in turn, ensuring a steady increase in the contact area of ​​the electrode-gel interface.

[0027] 3. Gradient gel combines the advantages of the softest and hardest gel layers, with the advantages of high sensitivity of the softest hydrogel and wide range detection of the hardest hydrogel layer.

[0028] The present invention is suitable for use in future electronic skin for health monitoring and tactile perception. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the bionic gradient gel off-line pressure sensor (BGGITS) in Example 1.

[0030] Figure 2 Schematic diagram of the BGGITS manufacturing process in Example 1.

[0031] Figure 3 These are high-definition images taken by BGGITS from different angles in Example 1.

[0032] Figure 4 This is a microscopic photograph of the hierarchical pyramid microstructure in Example 1.

[0033] Figure 5 1 is the SEM image and particle size distribution curve of the gradient gel in Example 1.

[0034] Figure 6 1 is the device principle diagram and circuit diagram of BGGITS in Example 1.

[0035] Figure 7 It is a schematic diagram for comparing the sensitivity of Example 1 and the comparative example.

[0036] Figure 8 This is a diagram of the compression strain simulation process of the gradient gel ionization sensor in Example 1. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0038] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the technical solution of the present invention is further described in detail below in conjunction with specific implementation methods.

[0039] In order to verify that the ionization sensor formed by the gradient gel combination and the graded pyramid microstructure electrode has the best sensitivity and the ability of linear wide range detection, the sensitivity (S) is used to measure the sensing performance of a sensor. The calculation formula of S is as follows:

[0040]

[0041] In the absence of external pressure stimulation, the capacitance value is defined as the initial capacitance C0, and after the pressure stimulation is applied, the capacitance change value of the sensor is defined as ΔC, and P is the external pressure. As a function of the external pressure (P), the sensitivity of the sensor can be obtained.

[0042] Example 1: Step (1), use 3D max software to design a hierarchical pyramid microstructure mold, slowly drip the vacuumized PDMS into the hierarchical microstructure mold, use a glue spreader to spin coat the mold, and spread the PDMS evenly on the mold. Then, cover the mold with a PET-ITO conductive film (1.5cm×3cm) treated by a vacuum plasma cleaner, cure it at room temperature for 1 hour, and then demold it after heating at 50°C in a forced air drying oven for 5 hours. Finally, place the hierarchical pyramid microstructure PDMS electrode in a high vacuum resistance evaporation coating equipment, and evaporate a 100nm thick Au layer on the surface of the electrode to obtain a hierarchical pyramid microstructure Au-PDMS electrode.

[0043] Step (2), preparing hydrogel ATMP-PVA by a one-pot method, soaking the prepared hydrogel in sodium sulfate, disodium hydrogen phosphate, sodium acetate, sodium chloride, and sodium iodide solutions of the same concentration for 12 hours, so that the gel produces a Hofmeister effect in the salt solution. Next, the soaked gel is cut into a size of 1.5 cm×1.5 cm. First, the hardest hydrogel soaked in sodium sulfate solution and the softest hydrogel soaked in sodium iodide solution are selected as the upper and lower layers of the gradient gel, and the middle layer is the softer hydrogel soaked in sodium acetate solution, so that a gradient modulus gel structure can be constructed.

[0044] Step (3), a sandwich structure is formed by two hierarchical pyramid microstructure Au-PDMS electrodes and a gradient gel dielectric layer to form a gradient gel ionization sensor, which is finally packaged with PI tape.

[0045] Step (4), in the process of testing the sensitivity of the sensor, a universal testing machine is used to apply pressure to the sensor, and an LCR tester is used to record the capacitance values ​​under different pressure conditions.

[0046] Example 2: Step (1), use 3D max software to design a pyramid microstructure mold at the same level, slowly drip the vacuumized PDMS into the microstructure mold at the same level, and use a glue spreader to spin coat the mold to evenly spread the PDMS on the mold. Then, cover the mold with a PET-ITO conductive film (1.5cm×3cm) treated by a vacuum plasma cleaner, cure it at room temperature for 1 hour, and then demold it after heating at 50°C in a forced air drying oven for 5 hours. Finally, place the pyramid microstructure PDMS electrode at the same level in a high vacuum resistance evaporation coating device, and evaporate a 100nm thick Au layer on the surface of the electrode to obtain a pyramid microstructure Au-PDMS electrode at the same level.

[0047] Step (2), preparing hydrogel ATMP-PVA by a one-pot method, soaking the prepared hydrogel in sodium sulfate, disodium hydrogen phosphate, sodium acetate, sodium chloride, and sodium iodide solutions of the same concentration for 12 hours, so that the gel produces a Hofmeister effect in the salt solution. Next, the soaked gel is cut into a size of 1.5 cm×1.5 cm. First, the hardest hydrogel soaked in sodium sulfate solution and the softest hydrogel soaked in sodium iodide solution are selected as the upper and lower layers of the gradient gel, and the middle layer is the softer hydrogel soaked in sodium acetate solution, so that a gradient modulus gel structure can be constructed.

[0048] Step (3), the same level pyramid microstructure Au-PDMS electrode is placed on top, and a sandwich structure is formed with a gradient gel dielectric layer and a parallel plate electrode to form a gradient gel ionization sensor, which is finally packaged with PI tape.

[0049] Step (4), in the process of testing the sensitivity of the sensor, a universal testing machine is used to apply pressure to the sensor, and an LCR tester is used to record the capacitance values ​​under different pressure conditions.

[0050] This Example 2 compares the performance differences between the same-level pyramid microstructure and the graded pyramid microstructure, and illustrates that compared with Example 1, the same-level pyramid microstructure does not have the ability to give the sensor high sensitivity.

[0051] Example 3: Step (1), use 3D max software to design a hierarchical pyramid microstructure mold, slowly drip the vacuumized PDMS into the hierarchical microstructure mold, use a glue spreader to spin coat the mold, and spread the PDMS evenly on the mold. Then, cover the mold with a PET-ITO conductive film (1.5cm×3cm) treated by a vacuum plasma cleaner, cure it at room temperature for 1 hour, and then demold it after heating at 50°C in a forced air drying oven for 5 hours. Finally, place the hierarchical pyramid microstructure PDMS electrode in a high vacuum resistance evaporation coating equipment, and evaporate a 100nm thick Au layer on the surface of the electrode to obtain a hierarchical pyramid microstructure Au-PDMS electrode.

[0052] Step (2), preparing hydrogel ATMP-PVA by a one-pot method, soaking the prepared hydrogel in sodium sulfate, disodium hydrogen phosphate, sodium acetate, sodium chloride, and sodium iodide solutions of the same concentration for 12 hours, so that the gel produces a Hofmeister effect in the salt solution. Next, the soaked gel is cut into a size of 1.5 cm×1.5 cm. First, the hardest hydrogel soaked in sodium sulfate solution and the softest hydrogel soaked in sodium iodide solution are selected as the upper and lower layers of the gradient gel, and the middle layer is the softer hydrogel soaked in sodium acetate solution, so that a gradient modulus gel structure can be constructed.

[0053] Step (3), a gradient gel ionization sensor is formed by placing a graded pyramid microstructure Au-PDMS electrode on top, and forming a sandwich structure with a gradient gel dielectric layer and a parallel plate electrode, and finally encapsulating it with PI tape.

[0054] Step (4), in the process of testing the sensitivity of the sensor, a universal testing machine is used to apply pressure to the sensor, and an LCR tester is used to record the capacitance values ​​under different pressure conditions.

[0055] This example compares the performance difference between a single graded micro-pyramid electrode and a graded micro-pyramid electrode with both upper and lower electrodes, and illustrates that compared with Example 1, a single graded micro-pyramid electrode does not provide the sensor with the ability to respond linearly over a wide range.

[0056] Example 4: Step (1), use 3D max software to design a hierarchical pyramid microstructure mold, slowly drip the vacuumized PDMS into the hierarchical microstructure mold, use a glue spreader to spin coat the mold, and spread the PDMS evenly on the mold. Then, cover the mold with a PET-ITO conductive film (1.5cm×3cm) treated by a vacuum plasma cleaner, cure it at room temperature for 1 hour, and then demold it after heating at 50°C in a forced air drying oven for 5 hours. Finally, place the hierarchical pyramid microstructure PDMS electrode in a high vacuum resistance evaporation coating equipment, and evaporate a 100nm thick Au layer on the surface of the electrode to obtain a hierarchical pyramid microstructure Au-PDMS electrode.

[0057] Step (2), preparing hydrogel ATMP-PVA by a one-pot method, soaking the prepared hydrogel in sodium sulfate, disodium hydrogen phosphate, sodium acetate, sodium chloride, and sodium iodide solutions of the same concentration for 12 hours, so that the gel produces a Hofmeister effect in the salt solution. Next, the soaked gel is cut into a size of 1.5 cm×1.5 cm. First, the hardest hydrogel soaked in the sodium sulfate solution is selected as the middle layer, the softest hydrogel soaked in the sodium iodide solution is selected as the top layer of the gradient gel, and the bottom layer is the softer hydrogel soaked in the sodium acetate solution, so that a gradient modulus gel structure can be constructed.

[0058] Step (3), a sandwich structure is formed by two hierarchical pyramid microstructure Au-PDMS electrodes and a gradient gel dielectric layer to form a gradient gel ionization sensor, which is finally packaged with PI tape.

[0059] Step (4), in the process of testing the sensitivity of the sensor, a universal testing machine is used to apply pressure to the sensor, and an LCR tester is used to record the capacitance values ​​under different pressure conditions.

[0060] This comparative example compares the performance differences of the gradient gel placement order, and shows that compared with Example 1, when the softest hydrogel is placed on the top layer and the softer hydrogel is placed on the bottom layer, although the sensitivity will be particularly high initially, as the pressure increases, their contact area will be greatly reduced, and the sensor will not be given the ability to respond linearly over a wide range.

[0061] Example 5: Step (1), use 3D max software to design a hierarchical pyramid microstructure mold, slowly drip the vacuumized PDMS into the hierarchical microstructure mold, use a glue spreader to spin coat the mold, and spread the PDMS evenly on the mold. Then, cover the mold with a PET-ITO conductive film (1.5cm×3cm) treated by a vacuum plasma cleaner, cure it at room temperature for 1 hour, and then demold it after heating at 50°C in a forced air drying oven for 5 hours. Finally, place the hierarchical pyramid microstructure PDMS electrode in a high vacuum resistance evaporation coating equipment, and evaporate a 100nm thick Au layer on the surface of the electrode to obtain a hierarchical pyramid microstructure Au-PDMS electrode.

[0062] Step (2), preparing hydrogel ATMP-PVA by a one-pot method, soaking the prepared hydrogel in sodium sulfate, disodium hydrogen phosphate, sodium acetate, sodium chloride, and sodium iodide solutions of the same concentration for 12 hours, so that the gel produces a Hofmeister effect in the salt solution. Next, the soaked gel is cut into a size of 1.5 cm×1.5 cm. First, the hardest hydrogel soaked in the sodium sulfate solution is selected as the bottom layer, the softest hydrogel soaked in the sodium iodide solution is selected as the middle layer of the gradient gel, and the top layer is the softer hydrogel soaked in the sodium acetate solution, so that a gradient modulus gel structure can be constructed.

[0063] Step (3), a sandwich structure is formed by two hierarchical pyramid microstructure Au-PDMS electrodes and a gradient gel dielectric layer to form a gradient gel ionization sensor, which is finally packaged with PI tape.

[0064] Step (4), in the process of testing the sensitivity of the sensor, a universal testing machine is used to apply pressure to the sensor, and an LCR tester is used to record the capacitance values ​​under different pressure conditions.

[0065] This example compares the performance differences of the gradient gel placement order, and illustrates that compared with Example 1, when the softer hydrogel is placed on the top layer and the softest hydrogel is placed on the bottom layer, because the initial graded micro-pyramid electrode contacts the softer layer, the sensitivity will be relatively reduced, and the sensor will not be given the ability to have high sensitivity.

[0066] The Hofmeister effect in the present invention was first proposed by Franz Hofmeister in 1888, which clarified the effects of different salt ions on protein denaturation and revealed the different precipitation abilities of proteins in aqueous solutions. The Hofmeister series based on ion solvation ability was established, summarizing the effects of ion solvation on protein behavior. "Kosmotropes" with rich hydration ability enhance the mechanical strength of the hydrogel network, while "Chaotropes" with limited hydration ability weaken the mechanical strength of the hydrogel network. ATMP-PVA hydrogel was prepared by rapid freeze-thaw treatment, PVA constructed the hydrogel framework, and ATMP participated in the hydrogen bond network for electron or ion migration. The oxygen-containing functional groups of ATMP molecules can form abundant hydrogen bonds with PVA chains, or interact with various hydration cosolvents. The Hofmeister effect provides a general and convenient method to adjust the mechanical properties of hydrogels. It provides a fast and accurate method for making gradient modulus gels that mimic skin. BGGITS working principle diagram and equivalent circuit ( Figure 6 ). A large number of positive and negative ions are distributed in the ATMP-PVA hydrogel. When the gradient hydrogel contacts the electrodes in an ionotropic sensor, an electric double layer (EDL) is formed at the ionotropic interface, and its capacitance is proportional to the interfacial contact area. Therefore, in ionotropic sensors, the adjustment of linearity is direct - only one parameter (Ac) needs to be considered. In this case, the EDL interface of the gradient hydrogel has a variable contact area determined by the applied pressure. Finite element analysis (FEA) simulations show a linear Ac-P relationship for the gradient hydrogel and micropyramids, indicating that sensors with this structure are expected to exhibit a linear response to the applied pressure. In summary, the synergistic effect of the designed structure and the signal enhancement provided by the ionotropic interface endow BGGITS with a combination of high sensitivity, linear response, and wide sensing capabilities.

[0067] Thanks to the skin-like gradient modulus gel layer regulated by the Hofmeister effect, the gradient gel combines the advantages of the softest and hardest gel layers, with the advantages of high sensitivity of the softest hydrogel and wide range detection of the hardest hydrogel layer. The interface between the micro-pyramid structure and the gradient gel forms an electrical double layer (EDL), which exhibits excellent capacitive properties and significant capacitive response under specific pressure conditions. The linear response is mainly attributed to the gradient micro-pyramids of different heights. As the external pressure increases, the pyramids of different heights contact the gel in turn, ensuring a steady increase in the contact area of ​​the electrode-gel interface.

[0068] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a biomimetic gradient gel ionization sensor, characterized in that: The following steps are involved: (1) Using 3D max software to design a hierarchical pyramid microstructure mold diagram, four hierarchical pyramid microstructure electrodes are prepared on each mold at the same time, and three pyramid microstructure molds of different heights are distributed in each mold; (2) importing the designed pyramid microstructure pattern into 3D printing software, using photosensitive resin as the 3D printing material, the photosensitive resin is heated and melted and flows out of the nozzle, and is formed according to the designed shape to obtain a graded pyramid microstructure mold; (3) pouring PDMS on the hierarchical pyramid microstructure mold, and using a glue machine to spin coat to make the PDMS evenly spread; then using a vacuum plasma cleaning machine to treat the PET-ITO conductive film to increase its affinity, and then covering the hierarchical pyramid microstructure mold with the PET-ITO conductive film, curing and demolding; (4) evaporating an Au layer on the surface of the hierarchical pyramid microstructure PDMS electrode to obtain a hierarchical pyramid microstructure Au-PDMS electrode; (5) preparing a sol of ATMP-PVA hydrogel by a one-pot method, dripping the sol onto a gel mold, and freezing to obtain an ATMP-PVA gel; (6) Rapidly immersing the ATMP-PVA gel in a salt solution to cause the gel to produce a Hofmeister effect in the salt solution, thereby obtaining hydrogels with different moduli; (7) Cutting hydrogels with different moduli and constructing gradient gel structures; (8) The hierarchical pyramid microstructured Au-PDMS electrode and the gradient gel dielectric layer are combined into a sandwich structure to form a gradient gel ionization sensor, which is then encapsulated with PI tape.

2. The method for preparing the biomimetic gradient gel ionization sensor according to claim 1, characterized in that: In the step (1), the overall size of the graded pyramid microstructure mold is 32.4mm*32.4mm, and the size of each graded pyramid microstructure electrode is 13.2mm*13.2mm; three pyramid microstructures of different heights are distributed in the graded pyramid microstructure mold, with sizes of 1mm, 0.8mm, and 0.6mm respectively, and the bottom edge length is 1mm, which is arranged periodically.

3. The method for preparing the biomimetic gradient gel ionization sensor according to claim 1 or 2, characterized in that: In the step (2), the nozzle temperature is set to 270°C.

4. The method for preparing the biomimetic gradient gel ionization sensor according to claim 1 or 2, characterized in that: In the step (3), the PDMS is prepared by the following steps: mixing the PDMS stock solution and the curing agent in a mass ratio of 10:1, and fully stirring, and then placing the mixture in a vacuum pump and evacuating for 50 minutes; the size of the PET-ITO conductive film is 1.5 cm×3 cm; during curing and demolding, after curing at room temperature for 1 hour, the film is heated at 50°C in a forced air drying oven for 5 hours and then demolded.

5. The method for preparing the biomimetic gradient gel ionization sensor according to claim 1 or 2, characterized in that: In the step (4), the layered pyramid microstructure PDMS electrode is placed in a high vacuum resistance evaporation coating device, and a 100 nm thick Au layer is evaporated on the surface of the electrode.

6. The method for preparing the biomimetic gradient gel ionization sensor according to claim 1 or 2, characterized in that: In the step (5), PVA, ATMP and H2O are mixed in a volume ratio of 4:10:30 and placed in a 105°C oil bath for reaction for 2 hours to form a sol solution; when freezing, it is frozen at -18°C for 24 hours to obtain ATMP-PVA gel.

7. The method for preparing the biomimetic gradient gel ionization sensor according to claim 1 or 2, characterized in that: In the step (6), the ATMP-PVA gel is rapidly immersed in various salt solutions for 12 hours.

8. The method for preparing the biomimetic gradient gel ionization sensor according to claim 1 or 2, characterized in that: In the step (7), gels of different moduli are cut into a size of 1.5 cm×1.5 cm, the hardest and softest hydrogels are selected as the upper and lower layers of the gradient gel, and the middle layer is selected according to actual needs to construct gradient gel structures of different combinations.

9. A bionic gradient gel ionization sensor, characterized in that: The bionic gradient gel ionization sensor is prepared by the preparation method of any one of claims 1 to 8.

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