Preparation Method of Bionic Gradient Gel Ionization Sensor and the Sensor

Abstract

The present invention relates to a preparation method of a bionic gradient gel ionoelectric sensor, comprising the following steps: (1) designing a hierarchical pyramid microstructure mold drawing using 3D max software; (2) importing the designed pyramid microstructure pattern into 3D printing software to obtain a hierarchical pyramid microstructure mold; (3) pouring PDMS on the hierarchical pyramid microstructure mold; (4) obtaining a hierarchical pyramid microstructure Au-PDMS electrode; (5) preparing a sol solution of ATMP-PVA hydrogel; (6) obtaining hydrogels with different moduli; (7) cutting and constructing a gradient gel structure from the hydrogels with different moduli; (8) forming a sandwich structure with the hierarchical pyramid microstructure Au-PDMS electrode and the gradient gel dielectric layer to constitute a gradient gel ionoelectric sensor, and encapsulating it with PI tape. The advantages of the present invention are that an electric double layer (EDL) is formed at the interface between the micro-pyramid structure and the gradient gel, showing excellent capacitance characteristics and significant capacitance response.

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) Import the designed pyramid micro-structure pattern into 3D printing software. Use photosensitive resin as the 3D printing material. The photosensitive resin melts when heated and flows out of the nozzle, and forms into the designed shape to obtain a hierarchical pyramid micro-structure mold.

[0010] (3) Pour PDMS on the hierarchical pyramid micro-structure mold and spin-coat it with a spin coater to make the PDMS spread evenly. Then, use a vacuum plasma cleaner to treat the PET-ITO conductive film to increase its affinity, and then cover the PET-ITO conductive film on the hierarchical pyramid micro-structure mold, cure it and demold it.

[0011] (4) Evaporate an Au layer on the surface of the hierarchical pyramid micro-structure PDMS electrode to obtain a hierarchical pyramid micro-structure Au-PDMS electrode.

[0012] (5) Prepare the sol solution of ATMP-PVA hydrogel by the one-pot method, drop the sol solution onto the gel mold, and freeze it to obtain ATMP-PVA gel.

[0013] (6) Quickly soak the ATMP-PVA gel in a salt solution to cause the Hofmeister effect in the salt solution, thereby obtaining hydrogels with different moduli.

[0014] (7) Cut and construct a gradient gel structure from the hydrogels with different moduli.

[0015] (8) Combine the hierarchical pyramid micro-structure Au-PDMS electrode and the gradient gel dielectric layer to form a sandwich structure, constituting a gradient gel ion sensor, and encapsulate it with PI tape.

[0016] In the step (1), the overall size of the hierarchical pyramid micro-structure mold drawing is 32.4 mm * 32.4 mm, and the size of each hierarchical pyramid micro-structure electrode is 13.2 mm * 13.2 mm. In the hierarchical pyramid micro-structure mold, there are three types of pyramid micro-structures with different heights, with sizes of 1 mm, 0.8 mm, and 0.6 mm respectively, and the bottom edge lengths are all 1 mm, arranged periodically.

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

[0018] In the step (3), the PDMS is prepared through the following steps: Mix the PDMS stock solution and the curing agent in a mass ratio of 10:1, stir well, and then put it into a vacuum pump to evacuate for 50 min to obtain it. The size of the PET-ITO conductive film is 1.5 cm × 3 cm. When curing and demolding, cure it at room temperature for 1 h, and then heat it at 50 °C in a forced-air drying oven for 5 h and then demold it.

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

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

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

[0022] In the step (7), gels with different moduli are cut into a size of 1.5 cm × 1.5 cm, and 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 with different combinations.

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

[0024] The advantages of the present invention are:

[0025] 1. An electric double layer (EDL) is formed at the interface between the micro-pyramid structure and the gradient gel, showing excellent capacitance characteristics and significant capacitance response;

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

[0027] 3. The gradient gel combines the advantages of the softest and hardest gel layers, has the advantage of high sensitivity of the softest hydrogel, and also combines the advantage of wide-range detection of the hardest hydrogel layer.

[0028] The present invention is applicable to future electronic skins for health monitoring and tactile perception. Description of the Drawings

[0029] Figure 1 It is a schematic diagram of the bionic gradient gel iontronic pressure sensor (BGGITS) in Example 1.

[0030] Figure 2 It is a schematic diagram of the manufacturing process of BGGITS in Example 1.

[0031] Figure 3 It is a high-definition picture of BGGITS in Example 1 taken from different angles.

[0032] Figure 4 Micrograph of the hierarchical pyramid microstructure in Example 1.

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

[0034] Figure 6 Device schematic diagram and circuit diagram of BGGITS in Example 1.

[0035] Figure 7 Schematic diagram for comparing the sensitivities of Example 1 and the comparative example.

[0036] Figure 8 Process diagram of the compression strain simulation of the gradient gel ionoelectric sensor in Example 1. Detailed implementation manners

[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 with the description. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. Those skilled in the art should understand that the details and forms of the technical solutions of the present invention can be modified or replaced without departing from the spirit and scope of the present invention, but such modifications and replacements all fall within the protection scope of the present invention.

[0038] To make the purpose, technical solution and effects of the present invention clearer and more definite, the technical solution of the present invention will be further described in detail below in conjunction with the specific implementation manners.

[0039] To verify that the ionoelectric sensor formed by the gradient gel combination and the hierarchical pyramid microstructure electrode has the best sensitivity and the ability of wide-range linear detection, the sensing performance of a sensor is measured by sensitivity (S). The calculation formula of S is as follows:

[0040]

[0041] Among them, in the absence of external pressure stimulation, the capacitance value is defined as the initial capacitance C0. After applying pressure stimulation, 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 drop the evacuated PDMS into the hierarchical microstructure mold, and use a spin coater to spin coat the mold so that the PDMS spreads evenly on the mold. Then cover the mold with a PET-ITO conductive film (1.5 cm × 3 cm) treated by a vacuum plasma cleaner. After curing at room temperature for 1 h, heat it at 50 °C in a blast drying oven for 5 h and then demold. Finally, put the hierarchical pyramid microstructure PDMS electrode into a high-vacuum resistance evaporation coating equipment, and evaporate a 100-nm-thick Au layer on the electrode surface to obtain a hierarchical pyramid microstructure Au-PDMS electrode.

[0043] Step (2), prepare the hydrogel ATMP-PVA by a one-pot method. Immerse the prepared hydrogel in sodium sulfate, disodium hydrogen phosphate, sodium acetate, sodium chloride, and sodium iodide solutions with the same concentration for 12 h to make the gel produce the Hofmeister effect in the salt solution. Next, cut the soaked gel into a size of 1.5 cm × 1.5 cm. First, select the hardest hydrogel soaked in the sodium sulfate solution and the softest hydrogel soaked in the sodium iodide solution as the upper and lower layers of the gradient gel, and the relatively soft hydrogel soaked in the sodium acetate solution as the middle layer, so as to construct a gradient modulus gel structure.

[0044] Step (3), form a sandwich structure composed of two hierarchical pyramid microstructure Au-PDMS electrodes and a gradient gel dielectric layer to construct a gradient gel ion sensor, and finally encapsulate it with PI tape.

[0045] Step (4), during the process of testing the sensor sensitivity, apply pressure to the sensor using a universal testing machine, and at the same time use an LCR tester to record the capacitance values under different pressure conditions.

[0046] Example 2: Step (1), use 3D max software to design a same-level pyramid microstructure mold. Slowly drop the evacuated PDMS into the same-level microstructure mold, and use a spin coater to spin coat the mold so that the PDMS spreads evenly on the mold. Then cover the mold with a PET-ITO conductive film (1.5 cm × 3 cm) treated by a vacuum plasma cleaner. After curing at room temperature for 1 h, heat it at 50 °C in a blast drying oven for 5 h and then demold. Finally, put the same-level pyramid microstructure PDMS electrode into a high-vacuum resistance evaporation coating equipment, and evaporate a 100-nm-thick Au layer on the electrode surface to obtain a same-level pyramid microstructure Au-PDMS electrode.

[0047] Step (2), preparing hydrogel ATMP-PVA by one-pot method. Immerse the prepared hydrogel in solutions of sodium sulfate, disodium hydrogen phosphate, sodium acetate, sodium chloride, and sodium iodide with the same concentration for 12 h to cause the Hofmeister effect in the gel in the salt solution. Next, cut the soaked gel into pieces of 1.5 cm × 1.5 cm. First, select the hardest hydrogel soaked in the sodium sulfate solution and the softest hydrogel soaked in the sodium iodide solution as the upper and lower layers of the gradient gel, and the relatively soft hydrogel soaked in the sodium acetate solution as the middle layer, so as to construct a gradient modulus gel structure.

[0048] Step (3), a sandwich structure is composed of a hierarchical pyramid microstructure Au-PDMS electrode on the top, a gradient gel dielectric layer, and a parallel plate electrode to form a gradient gel iontophoretic sensor, and finally it is encapsulated with PI tape.

[0049] Step (4), during the process of testing the sensor sensitivity, apply pressure to the sensor using a universal testing machine, and at the same time record the capacitance values under different pressure conditions using an LCR tester.

[0050] In this Example 2, to compare the performance differences between the hierarchical pyramid microstructure and the hierarchical pyramid microstructure, it is illustrated that compared with Example 1, the hierarchical pyramid microstructure does not endow the sensor with the ability of high sensitivity.

[0051] Example 3: Step (1), use 3D max software to design a hierarchical pyramid microstructure mold. Slowly drop the evacuated PDMS into the hierarchical microstructure mold, and use a spin coater to spin coat the mold so that the PDMS spreads evenly on the mold. Then cover the mold with a PET-ITO conductive film (1.5 cm × 3 cm) treated by a vacuum plasma cleaner. After curing at room temperature for 1 h, heat it in a blast drying oven at 50 °C for 5 h and then demold. Finally, put the hierarchical pyramid microstructure PDMS electrode into a high-vacuum resistance evaporation coating equipment and evaporate a 100-nm-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 one-pot method. Immerse the prepared hydrogel in solutions of sodium sulfate, disodium hydrogen phosphate, sodium acetate, sodium chloride, and sodium iodide with the same concentration for 12 h to cause the Hofmeister effect in the gel in the salt solution. Next, cut the soaked gel into pieces of 1.5 cm × 1.5 cm. First, select the hardest hydrogel soaked in the sodium sulfate solution and the softest hydrogel soaked in the sodium iodide solution as the upper and lower layers of the gradient gel, and the relatively soft hydrogel soaked in the sodium acetate solution as the middle layer, so as to construct a gradient modulus gel structure.

[0053] Step (3): A sandwich structure is formed by a hierarchical pyramid microstructured Au-PDMS electrode on top, and a gradient gel dielectric layer and parallel plate electrodes, constituting a gradient gel triboelectric sensor. Finally, it is encapsulated with PI tape.

[0054] Step (4): During the process of testing the sensor sensitivity, 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] In this embodiment, to compare the performance differences between a single hierarchical micro-pyramid electrode and hierarchical micro-pyramid electrodes for both the upper and lower electrodes, it is shown that, compared with Example 1, a single hierarchical micro-pyramid electrode does not endow the sensor with the ability of linear wide-range response.

[0056] Example 4: Step (1): Use 3D max software to design a hierarchical pyramid microstructured mold. Slowly drop the evacuated PDMS into the hierarchical microstructured mold, and use a spin coater to spin coat the mold so that the PDMS spreads evenly on the mold. Then cover the mold with a PET-ITO conductive film (1.5 cm × 3 cm) treated by a vacuum plasma cleaner. After curing at room temperature for 1 h, heat it at 50 °C in a forced-air drying oven for 5 h and then demold. Finally, put the hierarchical pyramid microstructured PDMS electrode into a high-vacuum resistance evaporation coating equipment, and evaporate a 100-nm-thick Au layer on the electrode surface to obtain a hierarchical pyramid microstructured Au-PDMS electrode.

[0057] Step (2): Prepare the hydrogel ATMP-PVA by a one-pot method. Immerse the prepared hydrogel in solutions of sodium sulfate, disodium hydrogen phosphate, sodium acetate, sodium chloride, and sodium iodide with the same concentration for 12 h to make the gel produce the Hofmeister effect in the salt solution. Next, cut the soaked gel into pieces of 1.5 cm × 1.5 cm. First, select the hardest hydrogel soaked in the sodium sulfate solution as the middle layer, the softest hydrogel soaked in the sodium iodide solution as the top layer of the gradient gel, and the relatively soft hydrogel soaked in the sodium acetate solution as the bottom layer, so as to construct a gradient modulus gel structure.

[0058] Step (3): A sandwich structure is formed by two hierarchical pyramid microstructured Au-PDMS electrodes and a gradient gel dielectric layer, constituting a gradient gel triboelectric sensor. Finally, it is encapsulated with PI tape.

[0059] Step (4): During the process of testing the sensor sensitivity, 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 is to compare the performance differences of the placement order of gradient gels. It shows that compared with Example 1, when the softest hydrogel is placed on the top layer and the relatively soft hydrogel is placed on the bottom layer, although the initial sensitivity is extremely high, as the pressure increases, their contact area will decrease significantly, and the sensor is not endowed with the ability of linear wide-range response.

[0061] Example 5: Step (1), Use 3D max software to design a hierarchical pyramid microstructure mold. Slowly drop the degassed PDMS into the hierarchical microstructure mold, and use a spin coater to spin coat the mold so that the PDMS spreads evenly on the mold. Then cover the PET-ITO conductive film (1.5 cm × 3 cm) treated by a vacuum plasma cleaner on the mold. After curing at room temperature for 1 h, heat it at 50 °C in a forced air drying oven for 5 h and then demold. Finally, put the hierarchical pyramid microstructure PDMS electrode into a high-vacuum resistance evaporation coating equipment and evaporate a 100-nm-thick Au layer on the surface of the electrode to obtain the hierarchical pyramid microstructure Au-PDMS electrode.

[0062] Step (2), Prepare the hydrogel ATMP-PVA by the one-pot method. Immerse the prepared hydrogel in the solutions of sodium sulfate, disodium hydrogen phosphate, sodium acetate, sodium chloride, and sodium iodide with the same concentration for 12 h to make the gel produce the Hofmeister effect in the salt solution. Next, cut the soaked gel into a size of 1.5 cm × 1.5 cm. First, select the hardest hydrogel soaked in the sodium sulfate solution as the bottom layer, the softest hydrogel soaked in the sodium iodide solution as the middle layer of the gradient gel, and the relatively soft hydrogel soaked in the sodium acetate solution as the top layer, so as to construct a gradient modulus gel structure.

[0063] Step (3), Consist of a sandwich structure composed of two hierarchical pyramid microstructure Au-PDMS electrodes and a gradient gel dielectric layer to form a gradient gel triboelectric sensor, and finally encapsulate it with PI tape.

[0064] Step (4), During the process of testing the sensitivity of the sensor, apply pressure to the sensor using a universal testing machine, and at the same time use an LCR tester to record the capacitance values under different pressure conditions.

[0065] This example is to compare the performance differences of the placement order of gradient gels. It shows that compared with Example 1, when the relatively soft hydrogel is placed on the top layer and the softest hydrogel is placed on the bottom layer, since the initial hierarchical micro-pyramid electrode contacts the softer layer, the sensitivity will decrease relatively, and the sensor is not endowed with the ability of high sensitivity.

[0066] The Hofmeister effect in the present invention was first proposed by Franz Hofmeister in 1888, which elucidates the effects of different salt ions on protein denaturation and reveals the different precipitation abilities of proteins in aqueous solutions. The Hofmeister series based on the ion solvation ability was established, and the effects of ion solvation on protein behavior were summarized. "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. The ATMP-PVA hydrogel was prepared by rapid freeze-thaw treatment. PVA constructs the hydrogel framework, while ATMP participates in the hydrogen bond network for electron or ion migration. The oxygen-containing functional groups of ATMP molecules can form rich hydrogen bonds with PVA chains or interact with various hydrated co-solvents. The Hofmeister effect provides a general and convenient method to adjust the mechanical properties of hydrogels. It provides a fast and accurate method for fabricating skin-mimicking gradient modulus gels. Schematic diagram and equivalent circuit of BGGITS( Figure 6 ). A large number of positive and negative ions are distributed in the ATMP-PVA hydrogel. When the gradient hydrogel contacts the electrode in the triboelectric sensor, an electric double layer (EDL) is formed at the triboelectric interface, and its capacitance is proportional to the interface contact area. Therefore, in the triboelectric sensor, the adjustment of linearity is straightforward - 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 the linear Ac-P relationship of the gradient hydrogel and the micro-pyramid, 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 triboelectric interface endow BGGITS with a combination of high sensitivity, linear response, and wide sensing ability.

[0067] Benefiting from the skin-mimicking gradient modulus gel layer regulated by the Hofmeister effect, the gradient gel combines the advantages of the softest and the hardest gel layers, has the high sensitivity advantage of the softest hydrogel, and also combines the wide-range detection advantage of the hardest hydrogel layer. The interface between the micro-pyramid structure and the gradient gel forms an electric double layer (EDL), which exhibits excellent capacitance characteristics and significant capacitance response under specific pressure conditions. The linear response is mainly attributed to the gradient micro-pyramids with different heights. As the external pressure increases, the pyramids with different heights contact the gel in sequence, ensuring a stable increase in the electrode-gel interface contact area.

[0068] As mentioned above, it is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within 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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