Electronic skin capable of realizing non-inductive, continuous and sensitive motion monitoring

Abstract

The invention discloses an electronic skin capable of realizing non-inductive, continuous and sensitive motion monitoring, and belongs to the field of flexible electronics and biomedical engineering. The electronic skin is mainly prepared from sodium alginate and acrylamide to form porous network gel, and the porous network gel is cross-linked to prepare the original porous base electronic skin; preparing solid-like coating paint from silicon dioxide nanoparticles, silicone oil and epoxy resin; the solid-like coating paint is uniformly sprayed on the surface of the original porous-based electronic skin through a spraying technology, and is cured to form the solid-like coating modified electronic skin. The electronic skin with the specific formula and thickness is prepared, and personalized, low-cost, portable, wireless, non-inductive, continuous and sensitive motion monitoring can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flexible electronics and biomedical engineering, and particularly to an electronic skin capable of realizing non-inductive, continuous and sensitive motion monitoring. BACKGROUND

[0002] In the whole life cycle health management, with the health port moving forward, it is essential to realize continuous and accurate monitoring of human motion function for disease prevention and progress evaluation. In particular, affected by the decline or even loss of individual motion function level, real-time monitoring of joint range of motion or gait can effectively reduce the occurrence of situations such as falls of the elderly and injuries of athletes during training. In addition, continuous and accurate monitoring of joint range of motion plays a crucial role in the whole chain from establishment of joint range of motion health baseline of specific groups (such as athletes and patients after joint surgery), symptom tracing of joint dysfunction to functional recovery evaluation at different stages and development of individualized rehabilitation programs.

[0003] Conventional methods, such as protractor or smart analog goniometer, often lack accuracy, and at the same time, require consistent distance between joints and devices. The developed intelligent sensing devices such as three-dimensional dynamic capture system are considered as the gold standard for gait or joint activity analysis. Although high-precision data acquisition, motion capture systems are usually complex and expensive, require skilled operators, and can only be performed in specialized environments and intermittently. In addition, wearable mobile monitoring systems based on accelerometers / inertial measurement units (IMUs) can be disturbed by external environmental factors, but the gait monitoring devices equipped with IMUs are bulky and inflexible, and the sensing system is usually composed of rigid materials (such as carbon-based, silicon-based), which can easily cause physiological or psychological discomfort to the wearer. Flexible and stretchable electronic devices, by adapting to various mechanical deformations and converting them into detectable electrical signals, show great potential in the fields of motion monitoring, gesture recognition, physiological signal monitoring, human-computer interaction, etc. In recent years, various conductive materials such as metal fibers, carbon-based materials, polymer nanofibers, and nanomesh have been widely used in the design and construction of stretchable electronic skin. However, the limited stretchability of these materials and the corresponding manufacturing equipment is difficult to meet the actual clinical needs of human motion (large human motion ~ 50%). Hydrogel electronic skin shows excellent softness, intrinsic high stretchability, air permeability and biocompatibility in human-computer interface use, and has great potential as an ideal joint activity monitoring electronic skin. When electrically functionalized, hydrogel sensors (such as strain sensors) can sensitively, safely and reversibly measure the changes of various joints of the human body. However, during long-term monitoring, sweat is easily adhered to the surface of the electronic device, affecting its stability, reliability and the accuracy of monitoring. These challenges highlight a key, unmet clinical need for continuous, accurate and non-invasive joint range of motion assessment to enable timely prevention and efficient treatment of sports injuries. In order to prevent sports injuries, falls and other accidents in people with abnormal joint activity, it is essential to develop electronic skin with excellent anti-biofouling properties, biocompatibility and the ability to monitor motion behavior in real time and durably.

[0004] For most of the currently developed wearable devices, including hydrogel-based electronic skin, sweat often accumulates between the electronic skin and the surface of the human skin during long-term wearing and monitoring, and complex components such as non-specific proteins and possibly growing bacteria easily cause unnecessary signal noise, leading to sensing failure. The latest progress in encapsulation and modification technology has led to the development of a new type of hydrogel electronic skin, which combines self-cleaning or antibacterial technology to not only inhibit the non-specific adhesion of proteins or bacteria but also avoid direct contact with sweat. However, there are still several key limitations in the continuous and precise non-invasive monitoring of joint activities: first, existing encapsulation technologies usually have a certain thickness and are not adhesive to hydrogels (such as polyimide PI, PDMS), which not only affects the sensitivity of the hydrogel sensor but also easily causes the device to misalign or slip, leading to incorrect or lost sensing signals. In addition, the weak air permeability of the introduced film may cause additional biocompatibility damage. Second, existing modified antibacterial hydrogel electronic skin is usually synthesized by incorporating silver nanoparticles, ionic liquids, or natural antibacterial ingredients, but the high toxicity, limited antibacterial performance, and durability of these substances limit the long-term accuracy and safety monitoring of hydrogel electronic skin. Or rely on complex microfabrication processes to modify hydrogels, as an extreme modification technology, in addition to high cost, labor-intensive and dependence on complex equipment, complex micro-nano structures are extremely easy to wear and collapse during repeated reversible movement of the human body. Third, in terms of biological safety verification, most current work mainly focuses on in vitro cell level or visual observation of skin allergic reactions, which is not enough to feedback the comprehensive visual and somatosensory damage such as redness, swelling, heat, and pain that conductive electronic skin may cause during long-term wearing and monitoring. Fourth, in terms of accuracy, it is unknown whether the various types of hydrogel electronic skin developed so far can meet the actual clinical needs. These factors greatly hinder the process of medical and clinical transformation of electronic skin such as hydrogel. Therefore, it is still a great challenge to prepare hydrogel electronic skin with excellent anti-biological contamination performance, biocompatibility, and durability to achieve continuous, non-invasive, and precise monitoring of joint movement. SUMMARY

[0005] In view of the above problems existing in the prior art, the present application provides an electronic skin capable of realizing non-invasive, continuous, and sensitive motion monitoring.

[0006] The technical scheme of the present application is as follows: The first object of the present application is to provide an electronic skin capable of realizing non-invasive, continuous, and sensitive motion monitoring, and the preparation method thereof comprises the following steps: (1) Synthesis of original porous-based electronic skin: sodium alginate, acrylamide, crosslinking agent, and initiator are added to deionized water in proportion, stirred at room temperature for 4-6 h to form a precursor solution; The precursor solution is poured into a mold and heated to initially form a porous network hydrogel. The porous mesh hydrogel is removed from the mold and immersed in calcium chloride solution to complete the ionic cross-linking process. After being removed, it is immersed in lithium bromide solution to obtain the original porous electronic skin. (2) Preparation of solid coatings Mix liquid A and liquid B in a certain proportion and stir evenly to obtain a solid-like coating material. Solution A is prepared by dissolving nano-silica particles, silicone oil, and silane coupling agent in ethyl acetate solution; Solution B is prepared by dissolving epoxy resin in ethyl acetate; (3) Preparation of electronic skin The solid-like coating obtained in step (2) is sprayed onto the surface of the original porous electronic skin obtained in step (2), and then cured at room temperature to obtain the solid-like coating modified electronic skin.

[0007] In one embodiment of the present invention, in step (1), the mass ratio of sodium alginate to acrylamide is 0.1~0.5:1~3; the mass ratio of acrylamide, initiator and crosslinking agent is 1~3:0.005~0.02:0.0005~0.02.

[0008] In one embodiment of the present invention, in step (1), the crosslinking agent is one or more of N,N'-methylenebisacrylamide, N,N'-(1,2-dihydroxyethylidene)bisacrylamide, polyethylene glycol diacrylate, pentaerythritol triacrylate, and divinylbenzene; the initiator is one or more of ammonium persulfate, potassium persulfate, azobisisobutyronitrile, azobisisoheptanenitrile, and benzoyl peroxide.

[0009] In one embodiment of the present invention, in step (1), the precursor solution is poured into the mold and heated to a temperature of 60~80°C for 1.5~3 h; the mold depth is 1~2 mm. The concentration of calcium chloride solution is 1~1.5 mol / L, and the soaking time is 15~30 min; The concentration of lithium bromide solution is 0.5~2 g / mL, and the soaking time is 15~30 min.

[0010] In one embodiment of the present invention, in step (2), the mass ratio of liquid A to liquid B is 2~3:0.5~1; the stirring speed is 400~600 rpm, and the time is 1~4 h.

[0011] In one embodiment of the present invention, in step (2), the mass ratio of silicone oil to nano-silica particles in liquid A is 0.5~1:0.03~0.05; the mass ratio of silicone oil to silane coupling agent is 1~2:0.5~1; and the mass ratio of silicone oil to ethyl acetate is 1~2:0.5~1.

[0012] The diameter of the nano-silica particles in solution A is 50~100 nm.

[0013] The stirring speed for mixing liquid A is 400~600 rpm, and the stirring time is 12~16 h.

[0014] In one embodiment of the present invention, in step (2), the mass ratio of epoxy resin to ethyl acetate in solution B is 0.5~1:1~4.

[0015] In one embodiment of the present invention, in step (3), the thickness of the solid-like coating sprayed is 4~6 μm.

[0016] In one embodiment of the present invention, in step (3), a solid-like coating is sprayed onto each surface of the gel to form a coating.

[0017] In one embodiment of the present invention, in step (3), the room temperature curing time is 24~48 h.

[0018] The beneficial technical effects of this invention are as follows: This invention introduces a novel nano-adhesive-based smooth coating design on the surface of a hydrogel system via covalent coupling. This coating is formed by functionalized nanoparticles capturing silicone oil and embedding it into a smooth polymer surface—epoxy resin—and exhibits excellent "solid-like" and "lubricating" properties. The nanoparticles within the coating adhere to each other, forming a dense skeletal structure, thereby inducing excellent wear resistance while maintaining the breathability of the porous network hydrogel. Furthermore, this allows the smooth, solid-like modified hydrogel to efficiently inhibit biosorption under various challenges such as stretching, friction, and sweat erosion.

[0019] This invention solves the problem of continuous, accurate, and imperceptible monitoring of joint movement. By introducing a smooth, "solid-like" coating with nanoparticle adhesive bases onto a porous network strain hydrogel electronic skin, the solid-like coating not only exhibits excellent wear resistance but also endows the porous network hydrogel with mechanically stable "lubricating" properties while maintaining good breathability. This allows the modified hydrogel to effectively inhibit bioadsorption under various challenges such as stretching, friction, and sweat erosion. The solid-like coating-modified electronic skin does not cause redness, swelling, heat, or pain during local joint movement monitoring and exhibits excellent "imperceptible" biocompatibility at both the in vivo and cellular levels. The "solid-like" coating does not significantly affect the tensile properties and strain monitoring sensitivity of the hydrogel, maintaining stable strain sensitivity even after 24 hours of exposure to sweat, protein solutions, and bacteria. Furthermore, due to the inhibition of bioadsorption, the solid-like coating-modified electronic skin can continuously monitor strain response and joint flexion with a stable signal throughout the day in complex biological environments. In addition, the solid-like coating-modified electronic skin demonstrates precise sensing capabilities for human movement, with performance comparable to clinical motion capture systems.

[0020] This invention utilizes functionalized nanoparticles to capture lubricating silicone oil, synergistically forming a dense skeletal structure through the cross-linking of rigid nanoparticles to create a near-solid coating. The coating is formed by amino-functionalized nanoparticles capturing hydroxyl silicone oil via hydrogen bonding and using epoxy resin as a coupling agent, covalently modifying the surface of a porous network hydrogel, thus creating a solid lubricating surface. The dense skeletal structure formed by the adhesion between nanoparticles within the coating not only exhibits excellent wear resistance but also promotes the breathability of the porous network hydrogel. This near-solid coating-modified electronic skin efficiently and safely inhibits biosorption under various challenges such as stretching, friction, and sweat erosion. During local joint motion monitoring, the modified hydrogel does not cause redness, swelling, heat, or pain, and demonstrates sensing accuracy comparable to clinical dynamic capture systems. Furthermore, benefiting from biosorption inhibition, the near-solid coating-modified electronic skin achieves durable, stable strain sensing (>24h) and all-day joint flexion motion monitoring applications in complex biological environments. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the electronic skin preparation process of the present invention; Figure 2 The results are FTIR spectroscopic analyses of the raw materials and the prepared solid-like coating modified electronic skin in Example 1. Figure 3 XPS results for the solid-like coating modified electronic skin and the original porous network-based gel electronic skin in Example 1; Figure 4The weight change curves of the original porous network-based gel electronic skin in Example 1 and Comparative Example 2, whether or not it was treated with 1 g / mL lithium bromide solution, were observed over 20 days at 25°C and 60% relative humidity. Figure 5 Differential scanning calorimetry (DSC) spectra of the original porous network-based gel electronic skin in Example 1 and Comparative Example 2, regardless of whether it was treated with 1 g / mL lithium bromide solution. Figure 6 The effect of different types of solid coating thickness on the breathability of electronic skin; Figure 7 The images show the cross-section (a) and surface morphology (b) of the solid-like coating modified electronic skin after adjusting the ratio of nanoparticles to silicone oil in Example 1 and Comparative Example 5, and the original porous network-based gel electronic skin. Figure 8 The adhesion strength between the solid-like coating after adjusting the ratio of nanoparticles to silicone oil in Example 1 and Comparative Example 5 and the original porous network-based gel electronic skin; Figure 9 The mechanical properties of the original porous network-based gel electronic skin in Example 1 and Comparative Example 1 before and after modification with a solid-like coating are shown. Figure 10 The comparison shows the electrical properties (resistance change rate, ΔR / R0) and sensitivity of the original porous network-based gel electronic skin and the solid-like coating modified electronic skin in Example 1 and Comparative Example 1 under different strain conditions. Figure 11 This is a comparison of the macroscopic antifouling advantages of the original porous network-based gel electronic skin and the electronic skin modified with a solid-like coating in Example 1 and Comparative Example 1. Figure 12 This is a comparison of the microscopic anti-adsorption advantages of the original porous network-based gel electronic skin and the electronic skin modified with a solid-like coating in Example 1 and Comparative Example 1. Figure 13 The results compare the effects of solid-like coating modified electronic skin with resting state (blank control group), nano acupoint magnetic therapy patch (positive control group), and commercial conductive gel patch on brain activation (a), changes in hemoglobin oxygenation concentration (b), and average functional connectivity strength (c) in a wide area of ​​the cerebral cortex. Figure 14 The skin reaction and changes in skin surface temperature were observed in different treatment groups after wearing the product for 30 minutes. Figure 15Representative fluorescence images (a) and (b) of the original porous network-based gel electronic skin and the solid-like coating-modified electronic skin after 24 hours of co-culture with Raw264.7 and NIH 3T3 cells, respectively; and quantitative statistical graphs of cell number (c) and cell viability (d) after 24 hours of co-culture and sealed culture. Figure 16 The changes in ΔR / R0 during 1000 cycles of stretching (20%) were observed when the original porous network-based gel electronic skin and the solid-like coating-modified electronic skin were co-incubated with sweat (concentration approximately 100%). Figure 17 The study investigated the changes in ΔR / R0 during repeated knee flexion and extension at different time points after subjects wore the original porous network-based gel electronic skin and the solid-like coating-modified electronic skin throughout the day. Figure 18 The curves (a) showing the rate of change of electrical data (ΔR / R0) of the ankle and knee joints during a single step cycle in monitoring normal walking for electronic skin modified with a solid-like coating, with the shaded area representing the 95% confidence interval. The curves (b) showing the change of ankle and knee joint motion angles during a single step cycle in monitoring normal walking using a 3D motion capture system, with the shaded area representing the 95% confidence interval. The distribution of the six cameras in the 3D motion capture system is shown (c). Optimal model fitting and correlation analysis were performed on the electrical signal data and joint angle data of the ankle and knee joints, respectively (d). Detailed Implementation The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] Figure 1 This is a schematic diagram of the electronic skin preparation process of the present invention, which includes three steps: synthesizing a porous network gel (porous-based electronic skin), a solid-like coating, and the preparation of electronic skin modified with a solid-like coating; Example 1 An electronic skin capable of achieving seamless, continuous, and sensitive motion monitoring, the preparation method of which includes the following steps ( Figure 2 ): (1) Synthesis of primitive porous electronic skin 1.2 g sodium alginate (viscosity 300 mPa·s, Qingdao Haizhilin Company, China), 9.68 g acrylamide (Aladdin), 0.008 g crosslinking agent (N,N'-methylenebisacrylamide, 99%, Aladdin) and 0.08 g initiator (ammonium persulfate, Aladdin) were added to 56 mL of deionized water and stirred at room temperature for 4 h to form a precursor solution. The precursor solution was poured into a mold and heated at 65°C for 2 hours to initially form a porous network hydrogel. The porous network hydrogel was removed from the mold and immersed in a 1 mol / L calcium chloride solution for 15 min to complete the ionic cross-linking process. After removal, it was immersed in a 1 g / mL lithium bromide solution for 30 min to obtain the original porous electronic skin. (2) Preparation of solid coatings Mix liquid A and liquid B in a certain proportion and stir evenly to obtain a solid-like coating material. Solution A is prepared by dissolving 0.6 g of nano-silica particles (99.5%, 50±5 nm), 20 g of silicone oil (10 cst, Sigma), 10 g of silane coupling agent (Shandong Yousuo) in 30 g of ethyl acetate solution (analytical grade). Solution B was prepared by dissolving 10 g of epoxy resin (Shandong Yousuo) in 10 g of ethyl acetate; (3) Preparation of solid-like coatings to modify electronic skin The solid-like coating obtained in step (2) was sprayed (20 cm distance, 3 seconds) onto the surface of the original porous electronic skin obtained in step (2), with a thickness of about 5 μm. After curing at room temperature, the solid-like coating modified electronic skin was obtained.

[0023] Example 2 Same as Example 1, except that in step (1), the heating conditions for synthesizing the original porous electronic skin are changed to 1.5 hours at 80°C.

[0024] Example 3 Same as Example 1, except that in step (1), the ionic crosslinking conditions of the original porous electronic skin are changed to soaking in a 2 g / mL lithium bromide solution for 15 min.

[0025] Example 4 Same as Example 1, except that the particle size of the nanoparticles in the solid-like coating solution is changed to 100 nm, while other conditions or parameters are the same as in Example 1.

[0026] Comparative Example 1 Same as Example 1, except that steps (2) and (3) are omitted.

[0027] Comparative Example 2 Same as Example 1, except that the lithium bromide immersion treatment and steps (2) and (3) in step (1) are omitted.

[0028] Comparative Example 3 Same as Example 1, except that in step (3), when spraying, under the premise of ensuring the same spraying distance, the original spraying time of 3 seconds is extended to 6 and 9 seconds respectively to cover the gel surface, and the thickness of the solid-like coating is 10 and 15 μm respectively.

[0029] Comparative Example 4 Same as Example 1, except that steps (2) and (3) are omitted, and the gel is encapsulated with a polydimethylsiloxane (PDMS) film with the same thickness as the solid-like coating.

[0030] Comparative Example 5 Same as Example 1, except that in step (2), the mass ratio of nanoparticles to silicone oil in liquid A is adjusted from the original 3:100 to 0.03:100, 0.3:100, 30:100, and 300:100 respectively.

[0031] Comparative Example 6 Same as Example 1, except that steps (2) and (3) are omitted, and a polyethylene terephthalate (PET) film with the same thickness as the solid-like coating is used to encapsulate the gel.

[0032] Comparative Example 7 Nano-acupoint magnetic therapy patches, commercially available conductive gel patches.

[0033] Test Example 1: Characterization of Surface Groups Fourier transform infrared spectroscopy (Spectrum TWO) was used to characterize the characteristic functional groups on the surfaces of the nanoparticles, silicone oil, epoxy resin, solid-like coating solution, solid-like coating modified electronic skin, and original porous electronic skin in Example 1. Figure 2 As can be seen, the solid-like coating forms hydrogen bonds after capturing silicone oil through a covalent cross-linking reaction between amino nanoparticles and epoxy resin. Simultaneously, a covalent cross-linking reaction occurs between the solid-like coating-modified electronic skin and the original porous electronic skin, thus forming a covalent cross-linked network at the interface, rather than simple physical adsorption and anchoring.

[0034] The surface elemental composition of the solid-like coating modified electronic skin prepared in Example 1 and the original porous electronic skin prepared in Comparative Example 1 were characterized by X-ray photoelectron spectroscopy (Thermo Scientific K-Alpha) to determine whether the solid-like coating was successfully modified on the surface of the original porous electronic skin. Figure 3 As can be seen, the solid-like coating was successfully applied to the surface of the original porous electronic skin.

[0035] 2. Moisturizing and antifreeze properties The original porous electronic skin prepared in Example 1 (1) and the original porous electronic skin prepared in Comparative Example 2 were subjected to water retention performance tests. The weight was measured periodically and the mass loss was recorded. Figure 4 As can be seen, electronic skin immersed in a 1 g / mL lithium bromide solution has excellent water retention properties, which can prevent moisture evaporation during long-term wear and maintain its flexibility and functional properties.

[0036] The antifreeze properties of the original porous electronic skin prepared in Example 1 (1) and the original porous electronic skin prepared in Comparative Example 2 were characterized. Differential scanning calorimetry (Discovery DSC 25) was used, with a cooling rate of 5℃ / min, a temperature range of 20 to 120℃, a nitrogen flow rate of 60 ml / min, and a sampling frequency of 50 Hz. Figure 5 As can be seen, the introduction of lithium bromide significantly reduced the freezing point of the electronic skin. The antifreeze properties of the original porous network-based gel electronic skin treated with 1 g / mL lithium bromide solution were significantly improved, indicating its application potential in extreme environments.

[0037] 3. Air permeability analysis The electronic skin (5 μm) modified with a solid-like coating obtained in Example 1, the original porous electronic skin obtained in Comparative Example 1, the electronic skin modified with a solid-like coating obtained in Comparative Example 3 (10 μm, 15 μm), and the electronic skin obtained in Comparative Example 4 were all characterized for air permeability. The water vapor permeability of different films was determined by placing a sealed beaker containing 20 mL of deionized water in a controlled environment (25°C, 60% relative humidity) and periodically recording the change in total mass. Figure 6 As can be seen, the original porous network-based gel electronic skin has excellent breathability, while the micron-level thickness of the solid-like coating does not affect its breathability.

[0038] 4. Surface morphology The surface morphology and internal microstructure of the electronic skin modified with a solid-like coating obtained in Example 1 and the electronic skins with different proportions of solid-like coatings obtained in Comparative Example 5 were analyzed. Figure 7 As can be seen, when the ratio increases from 0.03:100 to 3:100, the rigid nanoparticles and silicone oil gradually cross-link, forming a dense skeletal structure in the solid-like coating. This skeletal structure ensures a porous morphology (indicated by the red dashed circle), which is the fundamental reason for maintaining the excellent breathability of electronic skin.

[0039] 5. Mechanical properties The electronic skin modified with a solid-like coating obtained in Example 1 and electronic skins with different solid-like coating ratios obtained in Comparative Example 5 were subjected to tape peel tests according to ASTM D3359-17. Solid-like coatings with different mass ratios of nanoparticles to silicone oil were used to modify the original porous electronic skin. During the test, 3MTM VHB tape (approximately 2 cm wide, with an adhesion force of approximately 3000 N / m) was applied to the surface, followed by rolling pressure with a copper rod (approximately 4 kg). The tape was then peeled 180 mm from the SSC-coated hydrogel surface at a constant rate (approximately 100 mm / min), and the peel force was recorded using a universal tensile testing machine (HZ-1007C). Figure 8 As can be seen, when the ratio is increased to 3:100 or 30:100, the coating adhesion strength exceeds 9 MPa, but the strength drops sharply at 300:100.

[0040] Tensile tests were conducted on the solid-like coating modified electronic skin prepared in Example 1 and the original porous electronic skin prepared in Comparative Example 1. The maximum elongation of the two electronic skins was determined using a universal tensile testing machine (HZ-1007C). Figure 9 As can be seen, the tensile strain borne by the solid-like coating modified electronic skin before fracture is comparable to that of the original porous network-based gel electronic skin. This indicates that the SSC electronic skin possesses good mechanical properties, and that the SSC has almost no effect on the mechanical properties of the substrate electronic skin.

[0041] 6. Electrical properties The solid-like coating-modified electronic skin prepared in Example 1 and the original porous electronic skin prepared in Comparative Example 1 were subjected to cyclic tensile tests under different strains. Recording was performed using a Keithley 2450 source meter, and a motion controller (ZC300-3B) was used for control. Figure 10 As can be seen, the rate of change of resistance of both the original porous network-based gel electronic skin and the solid-like coating-modified electronic skin is linearly positively correlated with the applied strain. Notably, the sensitivity of both types of electronic skin is exactly the same.

[0042] 7. Macroscopic antifouling performance The solid-like coating modified electronic skin prepared in Example 1 and the original porous electronic skin prepared in Comparative Example 1 were subjected to macroscopic antifouling performance tests. The contact angle (2 μL) and sliding angle (10 μL) of the two electronic skin surfaces to different types of droplets (deionized water, sweat, cell culture medium, and sodium chloride) were measured using a contact angle meter, and the contact angle hysteresis (CAH) (CAH = θ) was calculated. adv -θ rec () Figure 11As can be seen, the solid-like coating modified on the surface of electronic skin exhibits excellent "slippery" properties. The SA and CAH values ​​of all tested liquids are consistently below 10°, which theoretically plays a key role in resisting bioadhesion and adsorption.

[0043] 8. Microscopic antifouling properties The microscopic antifouling performance of the electronic skin modified with a solid-like coating prepared in Example 1 and the original porous electronic skin prepared in Comparative Example 1 were tested.

[0044] Anti-protein adsorption assay: Fluorescein isothiocyanate bovine serum albumin (FITC-BSA, protein concentration approximately 0.1 mg / mL, molecular weight approximately 68 kDa, Solarbio) and fluorescent fibrinogen (Fg, protein concentration approximately 0.1 mg / mL, Solarbio) were selected as representative proteins. Different samples (solid-like coating modified electronic skin and original porous electronic skin) were placed in 96-well plates with the above two proteins and statically incubated for 24 hours in the dark at 37 °C. After incubation, the samples were cut open and washed once with PBS buffer (0.01 M, pH=7.2) to remove residual protein solution. After the above treatment, the protein molecule adsorption of different samples at the same exposure time was recorded using a fluorescence microscope (Ti2-E, Nikon), and quantitative statistical analysis was performed using ImageJ software to evaluate the relative fluorescence intensity of the attached proteins.

[0045] Antibacterial adsorption experiment: Escherichia coli (E. coli) was selected E. coli ATCC25922) and Staphylococcus aureus ( S. aureus ATCC6538 (both purchased from Shanghai Luwei Microbial Technology Co., Ltd.) were used as representative bacterial strains. Different samples (solid-coated modified electronic skin and original porous electronic skin) were respectively mixed with 100 μL of Escherichia coli or Staphylococcus aureus (concentration 1×(10⁻⁶)). 7 -10 8 The samples were incubated in 96-well plates at 37°C for 24 hours with 10 μg / mL PBS. After incubation, the samples were cut open and stained with 10 μg / mL green fluorescent dye (SYTO-9, Thermo Fisher Scientific). After staining, the samples were washed once with PBS (0.01 M, pH=7.4). The adsorption of protein molecules on different samples at the same exposure time was recorded using a fluorescence microscope, and the relative fluorescence intensity of bacteria adhering to and adsorbing on the surfaces of the two samples was quantified using ImageJ software. Figure 12 As can be seen, a large number of proteins and bacteria have eroded the interior of the original porous network-based gel electronic skin. The quantitative fluorescence intensity of protein and bacterial erosion inside the electronic skin modified with a solid-like coating is much lower than that of the original porous network-based gel electronic skin.

[0046] 9. Biocompatibility The solid-like coating modified electronic skin prepared in Example 1, the original porous electronic skin prepared in Comparative Example 1, and Comparative Example 7 were subjected to biocompatibility tests.

[0047] This study employed functional near-infrared spectroscopy (fNIRs) technology (instrument model: Nirsmart-6000A, Danyang Huichuang Medical Devices Co., Ltd., China) to record the activation state of the cerebral cortex using 24 light sources and 16 probes. The system consisted of near-infrared light sources (light-emitting diodes) and avalanche photodiodes, employing wavelengths of 730 nm and 850 nm, respectively, with a sampling frequency of 11 Hz. We focused on three regions of the brain: the primary somatosensory cortex, the secondary somatosensory cortex, and the prefrontal cortex, all of which are closely related to human sensory function. Furthermore, we used oxyhemoglobin concentration as a biomarker for cortical activation, an indicator that sensitively and reliably reflects the metabolic level of local cortical areas. Higher metabolic levels correlated with more significant cortical activation. Under conditions of quiet and undisturbed environment, all test materials (solid-like coating modified electronic skin, nano-acupoint magnetic therapy patches, and commercially available conductive gel patches) were applied to the same anatomical site for each subject. Figure 13 The comparison results of solid-like coating modified electronic skin with resting state (blank control group), nano acupoint magnetic therapy patch (positive control group) and commercial conductive gel patch on brain activation level (a), changes in hemoglobin oxygenation concentration (b) and average functional connectivity strength of a wide area of ​​the cerebral cortex (c) show that the wearing process of solid-like coating modified electronic skin did not cause any changes in human sensation and did not promote the activation of the cerebral cortex network.

[0048] In addition, changes in skin and surface temperature were recorded 30 minutes after the above materials were applied. Figure 14 As can be seen, solid-like coatings modifying electronic skin have no impact on human skin and sensation. The near-imperceptible nature of solid-like coatings during use highlights the comfort and safety of wearing electronic skin, providing strong support for its clinical application in biomedical practice.

[0049] The solid-like coating modified electronic skin prepared in Example 1 and the original porous electronic skin prepared in Comparative Example 1 were cut into small pieces and subjected to alcohol and ultraviolet disinfection treatments in sequence. Subsequently, an appropriate amount of cell culture medium (3 cm³) was added to them. 2 / mL). After filtration, extracts of the electronic skin were obtained separately. Meanwhile, the untreated group served as a control. Two aliquots of cells (1×(10⁻⁶)) were used. 5 -10 6Cells were cultured for 24 hours in 90% DEME, 9% FBS, and 1% antibiotic medium (cells / mL) at 37°C, 95% humidity, and 5% carbon dioxide. After incubation with extracts of electronic skin modified with a solid-like coating and the original porous electronic skin, cell proliferation was observed using 10 μg / mL green fluorescent dye (Calcein AM labeling live cells) and 10 μg / mL red fluorescent dye (propidium iodide labeling dead cells). The number of live and dead cells at the same exposure time was recorded using fluorescence microscopy, and the number of live and dead cells on the surface of the two groups of samples was quantified using ImageJ software. Furthermore, after incubation with CCK8 (wavelength 450 nm), absorbance was measured to observe cell viability. Figure 15 These results further demonstrate that solid-like coatings modifying electronic skin and its components exhibit excellent biocompatibility, thanks to their good breathability and high non-toxicity.

[0050] 10. Accuracy The accuracy of joint motion monitoring was tested using the solid-like coating modified electronic skin prepared in Example 1 and the original porous electronic skin prepared in Comparative Example 1.

[0051] Before different solution treatments, the two types of electronic skin were subjected to 1000 cycles of tensile testing at 20% strain. Subsequently, the electronic skins with solid-like coatings were placed in a sweat environment for 1000 cycles of tensile testing, and the resistance change was converted into ΔR / R0 values. Figure 16 The solid-like coating-modified electronic skin maintains a stable resistance baseline during cyclic stretching, ensuring signal fidelity. In contrast, the original porous network-based gel electronic skin without the solid-like coating exhibits significant signal drift / disorder during continuous monitoring.

[0052] Two types of skin were applied separately to the knee joint surface for no more than 24 hours, during which other normal daily activities could be performed. Every 3 hours, a standing (knee extended to 0 degrees) - sitting (knee bent to 90 degrees) repetition was performed for 5 minutes to obtain resistance change data, which was then converted into ΔR / R0 values. Before performing the repetitive standing-sitting test, participants were asked to run at a constant speed for half an hour and ensure they sweated. Figure 17 Complex biomolecules in sweat can erode and interfere with the ΔR / R0 signal of the original porous network-based gel electronic skin, leading to an inability to detect knee movement. In contrast, the solid-like modified electronic skin exhibited stable baseline and consistent strain sensing performance during continuous, all-day motion monitoring, remaining reliable even under sweat challenges.

[0053] Electro-skin modified with a solid-like coating was applied to the Achilles tendon and knee joint surfaces of the subjects. Electrical data changes in the ankle and knee joints during normal walking were acquired by repeatedly stretching the hydrogel and altering joint motion resistance. These data were then compared with kinematic data directly acquired by a 3D motion capture system. Figure 18 Angle curves (b) showing the changes in ankle and knee joint motion angles during a single step cycle of normal walking, with the shaded area representing the 95% confidence interval. Distribution of the six cameras in the 3D motion capture system (c). Optimal model fitting and correlation analysis were performed on the electrical signal data and joint angle data of the ankle and knee joints (d). Solid-like coatings modifying electronic skin can accurately capture the range of motion of human joints and other tissues, and are expected to be used for health monitoring and sports performance evaluation during sports rehabilitation, providing scientific and precise guidance for training.

[0054] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. An electronic skin capable of achieving seamless, continuous, and sensitive motion monitoring, characterized in that, Its preparation method includes the following steps: (1) Synthesis of primitive porous electronic skin Sodium alginate, acrylamide, crosslinking agent and initiator were added to deionized water in proportion and stirred at room temperature for 4-6 h to form a precursor solution. The precursor solution is poured into a mold and heated to initially form a porous network hydrogel. The porous mesh hydrogel is removed from the mold and immersed in calcium chloride solution to complete the ionic cross-linking process. After being removed, it is immersed in lithium bromide solution to obtain the original porous electronic skin. (2) Preparation of solid coatings Mix liquid A and liquid B in a certain proportion and stir evenly to obtain a solid-like coating material. Solution A is prepared by dissolving nano-silica particles, silicone oil, and silane coupling agent in ethyl acetate solution; Solution B is prepared by dissolving epoxy resin in ethyl acetate; (3) Preparation of electronic skin The solid-like coating obtained in step (2) is sprayed onto the surface of the original porous electronic skin obtained in step (2), and then cured at room temperature to obtain the solid-like coating modified electronic skin.

2. The electronic skin according to claim 1, characterized in that, In step (1), the mass ratio of sodium alginate to acrylamide is 0.1~0.5:1~3; the mass ratio of acrylamide, initiator and crosslinking agent is 1~3:0.005~0.02:0.0005~0.

02.

3. The electronic skin according to claim 1, characterized in that, In step (1), the crosslinking agent is one or more of N,N'-methylenebisacrylamide, N,N'-(1,2-dihydroxyethylidene)bisacrylamide, polyethylene glycol diacrylate, pentaerythritol triacrylate, and divinylbenzene; the initiator is one or more of ammonium persulfate, potassium persulfate, azobisisobutyronitrile, azobisisoheptanenitrile, and benzoyl peroxide.

4. The electronic skin according to claim 1, characterized in that, In step (1), the precursor solution is poured into the mold and heated to a temperature of 60~80 ℃ for 1.5~3 h; the mold depth is 1~2 mm. The concentration of calcium chloride solution is 1~1.5 mol / L, and the soaking time is 15~30 min; The concentration of lithium bromide solution is 0.5~2 g / mL, and the soaking time is 15~30 min.

5. The electronic skin according to claim 1, characterized in that, In step (2), the mass ratio of liquid A to liquid B is 2~3:0.5~1; the stirring speed is 400~600 rpm, and the time is 1~4 h.

6. The electronic skin according to claim 1, characterized in that, In step (2), the mass ratio of silicone oil to nano-silica particles in solution A is 0.5~1:0.03~0.05; the mass ratio of silicone oil to silane coupling agent is 1~2:0.5~1; and the mass ratio of silicone oil to ethyl acetate is 1~2:0.5~1. The diameter of the nano-silica particles in solution A is 50~100 nm. The stirring speed for mixing liquid A is 400~600 rpm, and the stirring time is 12~16 h.

7. The electronic skin according to claim 1, characterized in that, In step (2), the mass ratio of epoxy resin to ethyl acetate in solution B is 0.5~1:1~4.

8. The electronic skin according to claim 1, characterized in that, In step (3), the thickness of the solid-like coating is 4~6 μm.

9. The electronic skin according to claim 1, characterized in that, In step (3), a solid-like coating is sprayed onto each surface of the gel to form a coating.

10. The electronic skin according to claim 1, characterized in that, In step (3), the room temperature curing time is 24~48h.

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