Hydrogel-based wearable sensor and preparation and application method thereof

Abstract

The invention provides a hydrogel-based wearable sensor and a preparation and application method thereof, and relates to the technical field of nano power generation. The sensor comprises a hydrogel electrode assembly with a sandwich structure and a doped silica gel layer coated outside the hydrogel electrode assembly, the hydrogel electrode assembly is composed of a conductive composite hydrogel electrode layer in the middle and non-conductive hydrogel friction layers on the two sides, and a friction layer hydrogel-electrode layer hydrogel-friction layer hydrogel and elastomer packaging sandwich structure is prepared. The preparation method is simple, the storage and transfer efficiency of charges is improved by optimizing the hydrogel cross-linked structure and the components of the friction layer, and compared with a traditional sensor, the sensor has more sensing functions and has wide application prospects in the field of miniature signal transmission and sensing.

Description

Technical Field

[0001] This invention relates to the field of flexible wearable devices, and in particular to a hydrogel-based wearable sensor and its preparation and application methods. Background Technology

[0002] Flexible sensors convert mechanical energy into electrical energy based on the triboelectric effect and electrostatic induction principle. They offer advantages such as simple structure, low manufacturing cost, and high energy conversion efficiency, making them valuable for applications in power supply for microelectronic devices and self-driven sensing. The core of triboelectric technology's energy conversion efficiency depends on the charge storage capacity of the triboelectric layer material and the conductivity of the electrode layer.

[0003] Existing single-electrode triboelectric sensors mostly use traditional polymer materials (such as PTFE and PDMS) as the friction layer and metal foils (such as copper and aluminum foil) as the electrode layer. However, these methods have the following drawbacks: First, the dielectric properties of traditional polymer friction layers are limited, resulting in low surface charge density and consequently, relatively low output voltage and current. Second, the metal electrode layer lacks flexibility, making it difficult to adapt to the application scenarios of flexible electronic devices. Third, the devices are sensitive to environmental humidity; in high-humidity environments, the surface charge is easily consumed by water molecules, leading to a significant decrease in output performance. Therefore, there is an urgent need to develop a single-electrode triboelectric sensor that combines high output performance, flexibility, and environmental stability. Summary of the Invention

[0004] To address the problems of existing technologies, this invention provides a hydrogel-based wearable sensor and its preparation and application methods. By optimizing the hydrogel electrode structure and the composition of the friction layer, the power generation performance and environmental adaptability of the device can be improved, while expanding its application in the fields of object recognition and weighing.

[0005] To achieve the above-mentioned technical features, the present invention aims to provide a hydrogel-based wearable sensor, comprising a first friction layer, a second friction layer attached to the inner sidewall of the first friction layer, and an electrode layer attached to the middle of the second friction layer; copper wires are connected to both sides of the electrode layer, and the copper wires penetrate the sidewall of the first friction layer.

[0006] Preferably, the first friction layer and the second friction layer are non-conductive layers; the thickness of the first friction layer is 0.5~1.5mm, and the material is an elastomer material with a certain elastic modulus; the thickness of the second friction layer is 1~5mm, and the material is chitosan-polyvinyl alcohol hydrogel.

[0007] Preferably, the first friction layer is a coating layer or a reinforcement layer, wherein the reinforcement layer is doped with conductive particles, metal oxide particles, or particulate materials with high dielectric constant.

[0008] Preferably, the conductive particles are carbon or graphite particles; the metal oxide particles are titanium dioxide; and the high dielectric constant particle material is polytetrafluoroethylene or barium titanate.

[0009] Preferably, the method for preparing the hydrogel-based wearable sensor includes the following steps: S1. Mix chitosan aqueous solution and polyvinyl alcohol aqueous solution, heat and stir to obtain second friction layer hydrogel solution; S2. Heat and stir chitosan-phosphate aqueous solution and polyvinyl alcohol-phosphate-glycerol aqueous solution to obtain electrode layer hydrogel solution; S3. After placing wires at both ends of the second friction layer hydrogel solution from step S1 and the electrode layer hydrogel solution from step S2, freeze and thaw them repeatedly to obtain the friction layer hydrogel and the electrode layer hydrogel. S4. Place the friction layer hydrogel from step S3 on the upper and lower sides of the electrode layer hydrogel in step S3 to form a "sandwich" structure, and freeze and thaw it multiple times. S5. A layer of liquid AB silicone containing titanium dioxide powder is coated on the entire exterior of the "sandwich" using a spin coating method to form a first friction layer. After the silicone of the first friction layer has completely solidified, a hydrogel-based wearable sensor is obtained.

[0010] Preferably, in step S1, the chitosan aqueous solution: polyvinyl alcohol aqueous solution = 1:1 by volume, the heating temperature is 35~40℃, the stirring time is 40~60min, and the stirring rate is 10~30rpm / s; Alternatively, in step S1, the chitosan:water ratio in the chitosan aqueous solution is 0.1:1 by mass. In step S1, the polyvinyl alcohol to water ratio in the polyvinyl alcohol aqueous solution is 0.1:1 by mass.

[0011] Preferably, in step S2, the volume ratio of phosphate-chitosan aqueous solution to phosphate-glycerol-polyvinyl alcohol aqueous solution is 1:1, the heating temperature is 90~95℃, the stirring time is 20~40min, and the stirring speed is 10~30rpm / s. In step S2, the chitosan-phosphoric acid aqueous solution has a mass ratio of chitosan:phosphoric acid:water = 0.2:0.1:2. In step S2, the polyvinyl alcohol-phosphate-glycerol aqueous solution has a mass ratio of polyvinyl alcohol:phosphate:glycerol:water = 0.2:0.1:0.2:2.

[0012] Preferably, in step S3, freezing is carried out in an environment below -20°C for 10-12 hours, and thawing is carried out in a room temperature environment for 2-3 hours; the multiple cycles in step S3 are 6-8 cycles.

[0013] Preferably, in step S4, freezing is carried out in an environment below -20°C for 1 to 2 hours, and thawing is carried out in a room temperature environment for 2 to 3 hours; the multiple cycles in step S4 are 2 to 4 cycles. In step S5, 1-10 ml of liquid AB silicone containing titanium dioxide powder is taken as the coating liquid, and the spin coating speed is 500-800 rpm / min, which is continued for 5-20 seconds to make the coating liquid uniformly coated on the device surface.

[0014] Preferably, a method for applying a hydrogel-based wearable sensor is provided, wherein the sensor is used for weighing lightweight items in a laboratory; by monitoring the resistance change generated by the force applied to the sensor, the wearable device can detect human movement; and in conjunction with a robotic gripper, it generates electrical signals with different peak shapes or amplitudes for different materials to identify and grasp specific materials.

[0015] More preferably, the preparation process of the polyvinyl alcohol-chitosan hydrogel includes: 1. Preparation of polyvinyl alcohol precursor solution: Polyvinyl alcohol (model 1799, degree of alcoholysis 98%) is mixed with deionized water at a mass ratio of 0.1:1, placed in a water bath, and heated and stirred at 80~95℃ until the polyvinyl alcohol is completely dissolved to obtain polyvinyl alcohol precursor solution. 2. Preparation of chitosan precursor solution: Chitosan (95% degree of deacetylation) is mixed with deionized water at a mass ratio of 0.1:1, placed in a water bath, and heated and stirred at 30~35℃ for 40~60 min until the chitosan is completely dissolved to obtain chitosan precursor solution. 3. Preparation of hydrogel by freezing cycle: Polyvinyl alcohol precursor solution and chitosan precursor solution were mixed at a volume ratio of 1:1, poured into a petri dish, and frozen at a low temperature of -20℃ for 10h. Then, the mixture was thawed at room temperature for 2h. The above freezing-thawing cycle was repeated 6 times to obtain polyvinyl alcohol-chitosan hydrogel.

[0016] More preferably, the preparation process of the polyvinyl alcohol-chitosan-phosphate-glycerol composite hydrogel electrode layer includes: 1. Preparation of polyvinyl alcohol-phosphate-glycerol precursor solution: Polyvinyl alcohol, phosphoric acid (analytical grade), glycerol (analytical grade) and deionized water were mixed in a mass ratio of 0.2:0.1:0.2:2 and placed in a water bath. The mixture was heated and stirred at 80~95℃ for 40~60 min until the polyvinyl alcohol was completely dissolved to obtain the polyvinyl alcohol-phosphate-glycerol precursor solution. 2. Preparation of chitosan-phosphoric acid precursor solution: Chitosan, phosphoric acid and deionized water were mixed at a mass ratio of 0.2:0.1:2 and placed in a water bath. The mixture was heated and stirred at 30~35℃ for 40~60 min until the chitosan was completely dissolved to obtain the chitosan-phosphoric acid precursor solution. 3. Preparation of composite hydrogel by freezing cycle: Polyvinyl alcohol-phosphoric acid-glycerol precursor solution and polysaccharide-phosphoric acid precursor solution were mixed at a volume ratio of 1:1, poured into a petri dish, and frozen at -20℃ or below for 10 h after solidification. Then, it was thawed at room temperature for 2 h. The above freezing-thawing cycle was repeated 6 times to obtain polyvinyl alcohol-chitosan-phosphoric acid-glycerol composite hydrogel, which is the electrode layer.

[0017] More preferably, the preparation process of the first friction layer includes: 1. Material preparation: At room temperature, the A phase and B phase of AB phase silica gel and titanium dioxide powder (particle size 10μm) were added to a container at a mass ratio of 1:1:0.01. The mixture was stirred with a magnetic stirrer for 30~50min to ensure uniform mixing and obtain a liquid first friction layer. 2. Coating and curing: Using the spin coating method, take an appropriate amount of the first friction layer solution according to the thickness of the first friction layer, and continuously apply the solution evenly to the outside of the hydrogel electrode assembly at a speed of 800 rpm / min for 5~20s. The coating thickness is controlled at 0.5~1.5mm. Let it stand at room temperature or use an oven to accelerate curing until the outside is completely cured.

[0018] More preferably, in the preparation process of the hydrogel electrode assembly, both polyvinyl alcohol-chitosan hydrogel and polyvinyl alcohol-chitosan-phosphate-glycerol composite hydrogel are laid flat in a 10cm×10cm square culture dish, with the liquid level controlled at 5mm. After freezing cycles, they are cut into 4cm×3cm rectangles, and then the polyvinyl alcohol-chitosan-phosphate-glycerol composite hydrogel is placed between the polyvinyl alcohol-chitosan hydrogel to form a "sandwich" structure hydrogel electrode assembly.

[0019] More preferably, the sensor further includes a flexible substrate, which may be made of PET, PDMS, etc. The size of the flexible substrate matches the sensor, and the sensor is fixed on the substrate with epoxy resin adhesive, which facilitates the installation and testing of the device.

[0020] Working principle of the invention: The present invention discloses a hydrogel-based wearable sensor that operates based on the principles of triboelectric effect and electrostatic induction: when external pressure is applied, the friction layer comes into contact with the opposing friction layer (such as nitrile or skin). Due to the difference in electronegativity between the two materials, charge accumulates on the surface of the friction layer. When the pressure is removed, the friction layer separates from the opposing friction layer, and the electrode layer (polyvinyl alcohol-chitosan-phosphate-glycerol composite hydrogel) generates induced charge due to electrostatic induction. The charge forms a current through the external circuit. As the contact-separation process cycles, a continuous electrical signal output is achieved.

[0021] In the polyvinyl alcohol-chitosan-phosphate-glycerol composite hydrogel electrode layer, phosphoric acid protonates the -NH2 group of chitosan and makes the hydrogel conductive. Glycerol disrupts the internal molecular chain crystallization of chitosan and forms intermolecular hydrogen bonds with polyvinyl alcohol and chitosan through hydroxyl groups, thereby increasing the crosslinking density of the hydrogel. Doping 10μm titanium dioxide powder into silica gel at a mass ratio of 0.01:1 can increase the dielectric properties and surface charge density of the first friction layer, reduce charge leakage, and thus improve the output performance of the device.

[0022] The present invention has the following beneficial effects: 1. High output performance: In a low humidity environment, when using nitrile as the friction layer, the sensor of this invention has a forward output voltage of 430V, a current of 3.9μA, and a maximum instantaneous power of 0.81mW. At a contact frequency of 2Hz, it can simultaneously power 84 commercial LED lights, which can meet the power supply requirements of micro electronic devices.

[0023] 2. Flexibility and stability: The use of hydrogel as the electrode layer provides excellent flexibility and stretchability, making it suitable for flexible electronic device applications. At the same time, the first friction layer reduces the impact of water molecules on the electrode layer, improving the stability of the device under different humidity environments.

[0024] Using hydrogel as the main material of the device ensures the flexibility of the device. The first friction layer (doped with silicone) can delay the loss of water or aging of the internal hydrogel due to environmental factors (temperature, humidity, etc.), while also ensuring the stability of the device structure and improving the working life of the device.

[0025] 3. Multifunctional applications: In addition to power supply, this device can clamp specific materials based on the difference in electrical signals when objects of different materials come into contact; by detecting the rate of change of resistance of the hydrogel electrode layer under different masses, it can weigh the mass of objects, thus expanding the application field of triboelectricity.

[0026] 4. Simple preparation process: The present invention uses the sol method and the freeze-cycle method to prepare hydrogels. The preparation process does not require complicated equipment, has low cost, and is easy to scale up. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Figure 1 This is a resistance test diagram of the electrode layer hydrogel in the stretching state in Example 1; Figure 2 The images shown are physical photos and SEM images of the hydrogels for the second friction layer and electrode layer in Example 1, respectively. Figure 3 This is a structural diagram of a hydrogel-based wearable sensor reinforcement layer for Example 1; Figure 4 This is a comparison diagram of the current and voltage of the pure silicone layer and the reinforcement layer of a hydrogel-based wearable sensor in Example 1; Figure 5 This is a three-dimensional model diagram of a hydrogel-based wearable sensor according to Example 2; Figure 6 This is a comparison of the voltage and current of the pure silicone layer and the coating layer at different frequencies for a hydrogel-based wearable sensor in Example 2. Figure 7 This is a voltage and current fitting graph of a hydrogel-based wearable sensor under different humidity levels, as shown in Example 2. Figure 8 The charging time diagram for a hydrogel-based wearable sensor with different capacitors is shown in Example 2. Figure 9 This is a test image of a hydrogel-based wearable sensor illuminating an LED in Example 2; Figure 10 Example 3 illustrates the effect of different titanium dioxide particle sizes on the voltage and current of a hydrogel-based wearable sensor. Figure 11 This is Example 3, showing the effect of different mass ratios of titanium dioxide and silicone on voltage and current in a hydrogel-based wearable sensor. Figure 12 This is a schematic diagram of a hydrogel-based wearable sensor mechanical gripper according to Example 4; Figure 13 Example 4 illustrates the voltage change of a hydrogel-based wearable sensor when gripping different materials of different masses. Figure 14 This is a resistance variation graph for a hydrogel-based wearable sensor of Example 4, showing the same material but different masses. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0030] Unless otherwise specified in the following embodiments, in the prepared hydrogel-based wearable sensor, the initial length of each hydrogel layer (electrode layer and second friction layer) is fixed at 4 cm, and the initial width is fixed at 3 cm; the thickness of the electrode layer and friction layer is based on the data recorded in the examples.

[0031] Preferably, titanium dioxide AB silicone is used as the first friction layer, with a thickness of 0.5-1.5mm.

[0032] Unless otherwise specified, the following implementations are thawed at room temperature of 25~30℃. The room temperature in the following examples is 25℃.

[0033] Unless otherwise specified, the thickness of the titanium dioxide AB phase silicone friction layer in the following implementation examples is 1 mm.

[0034] The data in the following examples were tested using conventional methods with the corresponding instruments.

[0035] Example 1: Materials preparation: Chitosan (CS, degree of deacetylation 95%); polyvinyl alcohol (PVA, model 1799, degree of alcoholysis 98%); glycerol (GL, analytical grade); phosphoric acid (H3PO4); AB phase silica gel; titanium dioxide powder (particle size 10 μm); deionized water (laboratory preparation).

[0036] Preparation of polyvinyl alcohol-chitosan hydrogel: Polyvinyl alcohol (model 1799, degree of hydrolysis 98%) was mixed with deionized water at a mass ratio of 0.1:1 and placed in a water bath. The mixture was heated and stirred at 80-95℃ for 40-60 min until the polyvinyl alcohol was completely dissolved, yielding a polyvinyl alcohol precursor solution. Chitosan (degree of deacetylation 95%) was mixed with deionized water at a mass ratio of 0.1:1 and placed in a water bath. The mixture was heated and stirred at 30-35℃ for 40-60 min until the chitosan was completely dissolved, yielding a chitosan precursor solution. The polyvinyl alcohol precursor solution and the chitosan precursor solution were then mixed at a volume ratio of 1:1, poured into a petri dish, and frozen at -20℃ or below for 10 h. The mixture was then thawed at room temperature for 2 h. This freeze-thaw cycle was repeated 6 times to obtain a polyvinyl alcohol-chitosan hydrogel.

[0037] Preparation of polyvinyl alcohol-chitosan-phosphate-glycerol composite hydrogel: Polyvinyl alcohol phosphoric acid (analytical grade), glycerol (analytical grade), and deionized water were mixed in a mass ratio of 0.2:0.1:0.2:2 and placed in a water bath. The mixture was heated and stirred at 80-95°C for 40-60 minutes until the polyvinyl alcohol was completely dissolved, yielding a polyvinyl alcohol-phosphate-glycerol precursor solution. Chitosan, phosphoric acid, and deionized water were mixed in a mass ratio of 0.2:0.1:2 and placed in a water bath. The mixture was heated and stirred at 30-35°C for 40-60 minutes until the chitosan was completely dissolved, yielding a chitosan-phosphate precursor solution. The polyvinyl alcohol-phosphate-glycerol precursor solution and the chitosan-phosphate precursor solution were mixed in a volume ratio of 1:1 and poured into a petri dish. After solidification, the mixture was frozen at -20°C for 10 hours and then thawed at room temperature (25°C) for 2 hours. This freeze-thaw cycle was repeated 6 times to obtain a polyvinyl alcohol-chitosan-phosphate-glycerol composite hydrogel.

[0038] Fabrication of hydrogel electrode assembly: Polyvinyl alcohol-chitosan hydrogel and polyvinyl alcohol-chitosan-phosphate-glycerol composite hydrogel were laid flat in a 10cm×10cm square culture dish, with the liquid level controlled at 5mm. After freezing cycles, the mixture was cut into 4cm×3cm rectangles. The polyvinyl alcohol-chitosan-phosphate-glycerol composite hydrogel was then attached between the polyvinyl alcohol-chitosan hydrogel. After two freeze-thaw cycles, a "sandwich" structure hydrogel electrode assembly was formed.

[0039] Preparation of the reinforcement layer: Preparation of the lower layer of pure silica gel: At room temperature (10°C), phase A silica gel and phase B silica gel are placed in a stirring container at a mass ratio of 1:1. The mixture is stirred with a magnetic stirrer at a speed of 500 r / min for 10-20 min until there are no obvious particles or stratification, thus obtaining liquid pure silica gel. The liquid pure silica gel is then poured into a petri dish, and the liquid surface thickness is controlled to be 0.5 mm to 2 mm. The mixture is then left to stand at room temperature until the liquid pure silica gel is completely cured, forming the lower layer of pure silica gel structure of the reinforcing layer.

[0040] Preparation of the upper silicone-titanium dioxide composite layer: According to the mass ratio of titanium dioxide powder to silica gel (A phase + B phase) of 0.01:1, weigh out titanium dioxide powder, A phase silica gel and B phase silica gel (A phase: B phase = 1:1) and add them together to a stirring container; use a magnetic stirrer to stir continuously at a speed of 600 r / min for 20~30 min to avoid agglomeration, and finally obtain liquid silica gel-TiO2 composite system; The above composite layer is placed on the surface of the cured lower pure silicone layer, and the thickness is controlled to be the same as that of the lower pure silicone layer. It is left to stand at room temperature or accelerated by an oven. After it is completely cured, a double-layer reinforced structure of "lower pure silicone layer-upper silicone layer-TiO2" is obtained.

[0041] Fixing and encapsulation: The reinforcing layer is aligned so that the "lower pure silicone surface" faces the electrode assembly, ensuring complete adhesion to both sides of the assembly. Two freeze cycles are performed to achieve complete fixation. Wires are connected to the electrode layer and penetrate the reinforcing layer. Device fabrication is now complete, with the structure as shown below. Figure 3 As shown.

[0042] Output signal test: like Figure 4 As shown, when the contact frequency is 2Hz, the device outputs a peak positive voltage of 176V, a peak negative voltage of -120V, and a peak output current of 3.9μA. Compared with the device without the reinforcement layer (only the pure silicone friction layer), both the voltage and current are significantly improved.

[0043] Example 2: Coating preparation: At room temperature, phases A and B of AB-phase silica gel and titanium dioxide powder (particle size 10 μm) were added to a container at a mass ratio of 1:1:0.01. The mixture was stirred with a magnetic stirrer for 20–30 min until homogeneous, yielding liquid-doped silica gel. Then, 1–10 ml of the solution was spin-coated onto the exterior of the hydrogel electrode assembly using a spin-coating method, with a coating thickness controlled at 0.5–1.5 mm, forming an encapsulation structure. The assembly was then placed on a flexible substrate and allowed to cure at room temperature or in an oven until the liquid-doped silica gel was completely cured, forming the first friction layer. The device fabrication was completed, and the structure is as follows. Figure 5 As shown, the first friction layer is bonded to the second friction layer, and the electrode layer is bonded to the middle of the second friction layer. Two wires are connected to the other two sides of the electrode layer, and the wires penetrate the sidewall of the first friction layer.

[0044] Electrical signal output test: The device prepared in Example 2 was fixed on an experimental platform, and contact-separation tests were conducted at different contact frequencies using skin as the friction layer. The results are as follows: Figure 6 The results show that, compared with the pure silicone friction layer, the voltage and current of the coating layer are significantly improved at all frequencies.

[0045] Humidity sensor test: The sensor was placed in a sealed environment, and the humidity was increased from 50% to 85%, and the change in the electrical signal output was measured. The results are as follows: Figure 7 The linear fitting relationship between voltage and humidity is shown to be: goodness of fit The relationship between current and humidity is as follows: goodness of fit Humidity is negatively correlated with voltage and current. Output performance is better at low humidity, and at high humidity, the voltage drops to 17.5V and the current to 0.25μA, but it still maintains good output performance and humidity monitoring capability.

[0046] Application testing: The AC output from the sensor is converted to DC by a rectifier bridge, enabling the charging of commercial capacitors of varying capacities (0.47μF, 2.2μF, 4.7μF, 10μF). At a 2Hz contact frequency, the capacitors can be charged to 3.3V in just 120 seconds. Simultaneously, it can power 84 commercial LEDs, demonstrating the device's excellent power supply capabilities for low-power electronic devices. Figure 8 , Figure 9 .

[0047] Example 3: Influence of titanium dioxide particle size: Compared with Example 2, the difference lies in maintaining a fixed mass ratio of titanium dioxide to AB phase silica of 0.01:1, and using titanium dioxide with particle sizes of 1μm, 5μm, and 10μm to prepare coating layers, respectively, and testing the sensor output voltage; the results are as follows. Figure 10 The output voltage is highest when the particle size is 10μm. The voltage drops when the particle size is 5μm due to agglomeration, and the voltage drops when the particle size is 1μm due to the decrease in surface charge density. This proves that 10μm is the optimal particle size.

[0048] Effect of titanium dioxide mass ratio: Compared to Example 2, the difference lies in that the coating layers were prepared using mass ratios of 0.01:1, 0.02:1, 0.03:1, and 0.04:1, respectively, and the output voltage was tested; the results are as follows. Figure 11 The data shows that the voltage and current are highest at a ratio of 0.01:1, proving that 0.01:1 is the optimal quality ratio.

[0049] Example 4: Electrical signal testing on the surfaces of different materials: Four thin film materials (PTFE, Cu, Ni, and Paper) were respectively attached to the surface of a 3.8cm×2.9cm×2.2cm acrylic box. Identical counterweights were added inside the box, and the electrical signal was tested. The results are as follows: Figure 13 The display shows that when the robotic gripper performs a gripping operation, it can make a preliminary judgment on the material to be gripped based on the differences in electrical signals generated by different materials, thus achieving the gripping of specific materials.

[0050] Object weighing test: Using boxes of the four materials mentioned above with different masses as test objects, and controlling the masses to be 9.5g, 18.5g, and 27.5g respectively, the resistance change rate of the hydrogel electrode layer was tested. R / R0. For example... Figure 14 The resistance change rate is positively correlated with the mass. During the clamping process, the weight of the clamped object can be controlled to a certain extent. It can quickly classify and verify the weight of packages and goods, and has application functions such as weighing lightweight items and quickly sorting different materials.

[0051] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Without departing from the principles of the present invention, those skilled in the art can make various modifications and improvements, and all such modifications and improvements should fall within the protection scope of the present invention.

[0052] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many specific modifications under the guidance of the present invention without departing from the spirit of the invention and the scope of protection of the claims, and these modifications all fall within the scope of protection of the present invention.

Claims

1. A hydrogel-based wearable sensor, characterized in that, It includes a first friction layer (1), a second friction layer (2) is attached to the inner sidewall of the first friction layer (1), and an electrode layer (3) is attached to the middle of the second friction layer (2); copper wires (4) are connected to both sides of the electrode layer (3), and the copper wires (4) penetrate the sidewall of the first friction layer (1).

2. The hydrogel-based wearable sensor according to claim 1, characterized in that, The first friction layer (1) and the second friction layer (2) are non-conductive layers; the first friction layer (1) has a thickness of 0.5~1.5mm and is made of an elastomer material with a certain elastic modulus; the second friction layer (2) has a thickness of 1~5mm and is made of chitosan-polyvinyl alcohol hydrogel.

3. The hydrogel-based wearable sensor according to claim 1, characterized in that, The first friction layer (1) is a coating layer or a reinforcement layer, and the reinforcement layer is doped with conductive particles, metal oxide particles or particulate materials with high dielectric constant.

4. The hydrogel-based wearable sensor according to claim 3, characterized in that, The conductive particles are carbon or graphite particles; the metal oxide particles are titanium dioxide; and the high dielectric constant particle material is polytetrafluoroethylene or barium titanate.

5. A method for preparing a hydrogel-based wearable sensor according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Mix chitosan aqueous solution and polyvinyl alcohol aqueous solution, heat and stir to obtain second friction layer hydrogel solution; S2. Heat and stir chitosan-phosphate aqueous solution and polyvinyl alcohol-phosphate-glycerol aqueous solution to obtain electrode layer hydrogel solution; S3. After placing wires at both ends of the second friction layer hydrogel solution from step S1 and the electrode layer hydrogel solution from step S2, freeze and thaw them repeatedly to obtain the friction layer hydrogel and the electrode layer hydrogel. S4. Place the friction layer hydrogel from step S3 on the upper and lower sides of the electrode layer hydrogel in step S3 to form a "sandwich" structure, and freeze and thaw it multiple times. S5. A layer of liquid AB silicone containing titanium dioxide powder is coated on the entire exterior of the "sandwich" using a spin coating method to form a first friction layer. After the silicone of the first friction layer has completely solidified, a hydrogel-based wearable sensor is obtained.

6. The method for preparing a hydrogel-based wearable sensor according to claim 5, characterized in that, In step S1, the chitosan aqueous solution and polyvinyl alcohol aqueous solution are in a volume ratio of 1:1, the heating temperature is 35~40℃, the stirring time is 40~60min, and the stirring speed is 10~30rpm / s. Alternatively, in step S1, the chitosan:water ratio in the chitosan aqueous solution is 0.1:1 by mass. In step S1, the polyvinyl alcohol to water ratio in the polyvinyl alcohol aqueous solution is 0.1:1 by mass.

7. The method for preparing a hydrogel-based wearable sensor according to claim 5, characterized in that, In step S2, the volume ratio of phosphate-chitosan aqueous solution to phosphate-glycerol-polyvinyl alcohol aqueous solution is 1:1; the heating temperature is 90-95℃; the stirring time is 20-40 min; and the stirring speed is 10-30 rpm / s. In step S2, the chitosan-phosphoric acid aqueous solution has a mass ratio of chitosan:phosphoric acid:water = 0.2:0.1:

2. In step S2, the polyvinyl alcohol-phosphate-glycerol aqueous solution has a mass ratio of polyvinyl alcohol:phosphate:glycerol:water = 0.2:0.1:0.2:

2.

8. The method for preparing a hydrogel-based wearable sensor according to claim 5, characterized in that, In step S3, freezing is carried out in an environment below -20°C for 10-12 hours, and thawing is carried out in a room temperature environment for 2-3 hours; the cycle in step S3 is repeated 6-8 times.

9. The method for preparing a hydrogel-based wearable sensor according to claim 5, characterized in that, In step S4, freezing is carried out in an environment below -20°C for 1 to 2 hours, and thawing is carried out in a room temperature environment for 2 to 3 hours; the cycle in step S4 is repeated 2 to 4 times. In step S5, 1-10 ml of liquid AB silicone containing titanium dioxide powder is taken as the coating liquid, and the spin coating speed is 500-800 rpm / min, which is continued for 5-20 seconds to make the coating liquid uniformly coated on the device surface.

10. The method of applying a hydrogel-based wearable sensor according to any one of claims 1-4, characterized in that, The sensor is used for weighing lightweight items in the laboratory; by monitoring the resistance change generated by the force applied to the sensor, it can be used as a wearable device to detect human movement; and in conjunction with a robotic gripper, it can generate electrical signals with different peak shapes or amplitudes for different materials to identify and grasp specific materials.

Images