Gelled ionic liquid and preparation method and application thereof, gelled ionic liquid electronic skin and preparation method and application thereof

Abstract

The present application belongs to the technical field of electronic skin, and particularly relates to a gelled ionic liquid, a preparation method and application thereof, and a gelled ionic liquid electronic skin, a preparation method and application thereof. The gelled ionic liquid is obtained by mixing 1-butyl-3-methyl imidazole tetrafluoroborate and N,N'-di(2-hydroxyethyl)oxamide for gelling. The gelled ionic liquid obtained by the present application retains the wide temperature range characteristics of 1-butyl-3-methyl imidazole tetrafluoroborate, and significantly improves the viscosity and resistance stability thereof. The gelled product is used as a conductive material for preparing stretchable electronic skin, and the electronic skin obtained has high-performance wide temperature range detection capability, and can be flexibly assembled in an array to realize recognition of the number, position and contour of objects placed, recognition of the speed, trajectory and number of objects sliding, and precise recognition of single numbers and complete sentence hand gestures.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic skin, and specifically relates to gelled ionic liquid and a preparation method and application thereof, and gelled ionic liquid electronic skin and a preparation method and application thereof. Background Art

[0002] As the largest organ in the human body, the skin has the ability to sense complex external environmental stimuli such as pressure and temperature, and is an important way for the human brain to collect external information. Simulating the perceptual ability of the skin is of great significance and has broad applications in fields such as robotics, artificial intelligence, the Internet of Things, and life and health, which has also promoted the birth and development of electronic skin. Based on different sensing mechanisms and structural designs, people have prepared flexible electronic skin with multimodal perception (distributed pressure, temperature, proximity, chemical composition, etc.). It can convert external stimuli such as temperature, humidity, and mechanical deformation into electrical signals or other forms of signals according to certain rules. It can be used to detect human movement and monitor vital signs such as heart rate, respiration, body temperature and blood sugar. It can also support the object operation of robotics and prosthetics.

[0003] Conductive materials significantly influence the performance of electronic skin. Currently, commonly used conductive materials for electronic skin include liquid metals, ionic liquids, and hydrogels. Liquid metals, especially gallium-based alloys (gallium-indium alloys and gallium-indium-tin alloys), are gaining attention due to their low toxicity and high electrical conductivity. However, they solidify below 16°C and break when deformed, leading to open-circuit failures in electronic skin. In contrast, ionic liquids have a lower melting point, making them suitable for harsh low-temperature environments. They also offer many unique advantages, such as low vapor pressure, excellent thermal stability, high conductivity, and a wide electrochemical window. However, ionic liquids inherently suffer from resistance drift and are highly fluid and prone to leakage, making it difficult to create electronic skin with stable and reliable detection performance. Hydrogels, as conductive materials, offer excellent stretchability and biocompatibility, and their internal cross-linked network reduces fluidity, thus addressing the leakage issue. However, hydrogels' poor conductivity and instability in complex temperature environments significantly limit their development and application in the electronic skin field.

[0004] In summary, the currently commonly used electronic skin conductive materials have the disadvantages of poor low-temperature performance, easy leakage and poor resistance stability. Summary of the Invention

[0005] The present invention aims to provide a gelled ionic liquid, a preparation method and application thereof, and a gelled ionic liquid electronic skin, a preparation method and application thereof. The gelled ionic liquid provided by the present invention significantly improves its viscosity and resistance stability while retaining its wide temperature range properties. Using this gel as a conductive material to prepare stretchable electronic skin, the resulting electronic skin has wide temperature range detection capabilities and can be flexibly assembled in arrays. It can recognize the number, position, and contour of placed objects, as well as the speed, trajectory, and number of sliding objects. It also achieves accurate recognition of sign language gestures, including single digits and complete sentences.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a gelled ionic liquid, comprising the following steps:

[0008] 1-Butyl-3-methylimidazolium tetrafluoroborate and N,N'-bis(2-hydroxyethyl)oxalamide are mixed and gelled to obtain a gelled ionic liquid.

[0009] Preferably, the mass percentage of the N,N'-bis(2-hydroxyethyl)oxamide to the mass percentage of the 1-butyl-3-methylimidazolium tetrafluoroborate is 1 to 10 wt%;

[0010] The gelation temperature is 90-150° C., and the gelation time is 28-32 minutes.

[0011] The present invention provides a gelled ionic liquid prepared by the preparation method described in the above technical solution.

[0012] The present invention provides the use of the gelled ionic liquid described in the above technical solution as a conductive material in the preparation of electronic skin.

[0013] The present invention provides a gelled ionic liquid electronic skin, comprising a stacked flexible upper packaging layer and a flexible lower packaging layer, wherein the inner surface of the flexible upper packaging layer is provided with a plurality of circuit channel units, each of which is formed by circuit channels, and the flexible lower packaging layer encapsulates the circuit channels;

[0014] The gelled ionic liquid electronic skin further includes a conductive material filled in the circuit channel, and the conductive material is the gelled ionic liquid described in the above technical solution.

[0015] Preferably, the material of the flexible upper packaging layer is platinum-catalyzed silica gel; the thickness of the flexible upper packaging layer is 0.05 to 0.25 cm;

[0016] The cross section of the line channel is square, and the side length of the cross section of the line channel is 0.1 to 0.4 cm.

[0017] Preferably, the line channels forming the line channel unit form a circular spiral pattern, the radius of the circular spiral pattern is 1.5 cm; and the area percentage of the line channels in the circular spiral pattern is 17.6-29.3%.

[0018] Preferably, the number of the line channel units is ≥2, the line channel units are arranged in an array, and the distance between two adjacent line channel units is ≥1.4 cm.

[0019] The present invention provides a method for preparing the gelled ionic liquid electronic skin described in the above technical solution, comprising the following steps:

[0020] The upper packaging layer template and the lower packaging layer template are obtained by 3D printing;

[0021] Using a template method, the upper packaging layer template and the lower packaging layer template are used to prepare a flexible upper packaging layer and a flexible lower packaging layer in an uncured state respectively;

[0022] Laying the flexible upper packaging layer and the flexible lower packaging layer in an uncured state on top of each other and bonding them to obtain a semi-finished product;

[0023] Conductive material is injected into the circuit channel of the semi-finished product to obtain the gelled ionic liquid electronic skin.

[0024] The present invention provides the application of the gelled ionic liquid electronic skin described in the above technical solution or the gelled ionic liquid electronic skin prepared by the preparation method described in the above technical solution in wearable sensors for human-computer interaction, motion recognition or non-therapeutic and non-diagnostic purposes.

[0025] The present invention provides a method for preparing a gelled ionic liquid, comprising the following steps: mixing 1-butyl-3-methylimidazolium tetrafluoroborate and N,N'-bis(2-hydroxyethyl)oxamide for gelation to obtain a gelled ionic liquid. The present invention selects N,N'-bis(2-hydroxyethyl)oxamide (Diethanolamide ofmalonic acid, referred to as DEA) as a crosslinking agent for the 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) ionic liquid. DEA is an organic molecule containing an amide group, such as Figure 1The gelation mechanism shown mainly involves the following aspects: (1) DEA and [BMIM][BF4] molecules can interact through hydrogen bonds and van der Waals forces. Although hydrogen bonds are weak non-covalent interactions, in sufficient numbers, they can form a stable network structure and promote the formation of gel. At the same time, DEA molecules contain hydroxyl groups, which can form hydrogen bonds with the charged fluoroborate ions in [BMIM][BF4], and the intermolecular van der Waals forces also contribute to the mutual attraction of molecules. (2) Ionic interaction: The cations and anions in DEA molecules and [BMIM][BF4] ionic liquids all have certain polarity. The interaction between these polar parts can bring the molecules together to form a gel. The charge carried by the polar part also has a charge effect, which can also enhance the attraction between molecules and promote the formation of gel. The above interactions ultimately lead to cross-linking between molecules, forming a three-dimensional network structure. This network structure has a certain stability, making the gel exhibit solid-like properties. In summary, the present invention uses the cross-linking agent N,N'-bis(2-hydroxyethyl)oxamide and 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid ([BMIM][BF4]) to prepare a gelled ionic liquid, which significantly improves its viscosity and resistance stability while retaining the wide temperature range characteristics (-71°C to 300°C) of 1-butyl-3-methylimidazolium tetrafluoroborate. The gel is used as a conductive material to prepare stretchable electronic skin. The electronic skin has high-performance wide temperature range detection capabilities and can be flexibly assembled in an array, realizing the recognition of the number, position, and contour of objects placed, as well as the speed, trajectory, and number of sliding objects of objects. It also realizes the accurate recognition of sign language gestures of single numbers and complete sentences.

[0026] The present invention provides a gelled ionic liquid electronic skin comprising a stacked flexible upper encapsulation layer and a flexible lower encapsulation layer. The inner surface of the flexible upper encapsulation layer is provided with a plurality of circuit channel units, each formed by circuit channels, and the flexible lower encapsulation layer encapsulates the circuit channels. The gelled ionic liquid electronic skin also includes a conductive material filling the circuit channels, wherein the conductive material is the gelled ionic liquid described in the above technical solution. The present invention uses gelled ionic liquid as the conductive material for the electronic skin, ensuring stable detection performance even in ultra-low temperature environments, and addressing the issues of resistance drift and leakage inherent in the conductive material of the electronic skin. At the same time, because the sensing units (circuit channel units and the conductive material filling the circuit channels) have the characteristics of flexible assembly, integrating them into a large-scale electronic skin achieves accurate recognition of static load and dynamic load (0-8cm / s) information in ultra-low temperature environments (-50°C). In addition, the present invention also has a certain degree of damage redundancy detection function. Even in the case of damage, the sensing units of the electronic skin provided by the present invention maintain 95% of the pressure response within 4800Pa, and after exceeding 4800Pa, it can still retain about 60% of the pressure response. In addition, the pressure response of the damaged skin is environmentally weatherable and is not affected by low temperatures and vacuum environments. The gelled [BMIM][BF4] electronic skin provided by the present invention can maintain highly sensitive pressure detection under harsh temperature conditions. Combined with its damage redundancy detection function, it has great potential in deep space exploration, polar expeditions and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a mechanism diagram of the gelation reaction in the present invention;

[0028] Figure 2 A flow chart for preparing the gelled ionic liquid electronic skin provided by the present invention;

[0029] Figure 3 The results of characterization of the effect of heating temperature on the preparation of gelled ionic liquids are shown in Figure 2. Figure 3 a)-c) are ionic liquids with a DEA concentration of 5 wt% after heating at 90°C, 120°C, and 150°C, respectively. Figure 3 d)-f) are the products after heating and cooling at 90°C, 120°C, and 150°C respectively;

[0030] Figure 4 The effect of cross-linking agent DEA concentration on the gelation process of ionic liquids;

[0031] Figure 5 The curves of dynamic viscosity of gelled ionic liquids with different DEA concentrations versus shear rate are shown;

[0032] Figure 6is the resistance drift result of [BMIM][BF4] ionic liquid before and after gelation, Figure 6 a) Resistance drift rate of ionic liquid electronic skin with different cross-sectional sizes; Figure 6 b) is the resistance drift rate of gelled ionic liquid electronic skin with different cross-sectional sizes;

[0033] Figure 7 The data comparison of drift resistivity and drift time of the two devices when the resistance is close to a fixed value is shown in the figure. Figure 7 a) is a comparison of the drift time of gelled ionic liquid electronic skin and ionic liquid electronic skin; Figure 7 b) is a comparison of the resistance drift rate of gelled ionic liquid electronic skin and ionic liquid electronic skin;

[0034] Figure 8 The resistance change curve of the electronic skin with different channel inner diameters when adding weights;

[0035] Figure 9 The resistance change curve of the electronic skin with different thickness of the Ecoflex upper packaging layer;

[0036] Figure 10 This is an enlarged diagram of the resistance change curve of the Ecoflex electronic skin with a thickness of 0.15 cm when weights are added;

[0037] Figure 11 Schematic diagram of circuit channels with different area ratios;

[0038] Figure 12 is the resistance change of the electronic skin device with different number of channels, Figure 12 a) is the resistance change curve of the electronic skin with different graphic area ratios; Figure 12 b) is the fitting curve of the resistance change of the electronic skin with different pattern area ratios versus the weight mass;

[0039] Figure 13 The detection limit of the five-channel electronic skin for external pressure;

[0040] Figure 14 The resistance change of the electronic skin obtained by gelling ionic liquid with different DEA concentrations, Figure 14 a) is the resistance change curve of the electronic skin with different cross-linking agent concentrations. Figure 14 b) is the fitting curve of the resistance change of the electronic skin with different cross-linking agent concentrations versus the weight mass;

[0041] Figure 15 The resistance change curve of the electronic skin after being stretched 1000 times at 50% strain;

[0042] Figure 16 This is the research result of the stability performance of gelled ionic liquid electronic skin on curved surface detection. Figure 16 a)-d) in the figure are schematic diagrams of different surface environments. Figure 16 e) is the resistance change curve of the electronic skin with accumulated weights in different curved surface environments. Figure 16 f) is the fitting curve of the resistance change of the electronic skin in different curved surface environments versus the mass of the weight;

[0043] Figure 17 The wide temperature range detection performance of gelled ionic liquid electronic skin, Figure 17 a) is the resistance change of the electronic skin when different pressures are applied at different temperatures. Figure 17 b) is the fitting curve of the resistance change of the electronic skin under different temperatures and pressures;

[0044] Figure 18 The results of the resistance response time study of gelled ionic liquid electronic skin when different loads are added at different temperatures are shown. Figure 18 a) is the fitting curve of the electronic skin's resistance response time when different pressures are applied at different temperatures; Figure 18 b) is a schematic diagram of the resistance response of the electronic skin under different pressures at different temperatures;

[0045] Figure 19 This is the research result of low-frequency deformation response performance of gelled ionic liquid electronic skin. Figure 19 a) shows the response of the electronic skin to triangular waveform signals of different frequencies; Figure 19 b) shows the response of the electronic skin to sinusoidal waveform signals of different frequencies;

[0046] Figure 20 This is a physical picture of the damaged gelled ionic liquid unit;

[0047] Figure 21 Redundant detection results of damage of gelled ionic liquid electronic skin. Figure 21 a) is a comparison of the resistance response of applying weights at room temperature and pressure. Figure 21 b) is a comparison of the resistance response when a weight is applied at -50°C; Figure 21 c) is a comparison chart of the resistance response when a weight is applied in a vacuum environment; Figure 21 d) is a comparison of the resistance response when a weight is applied in a -10°C vacuum environment;

[0048] Figure 22 This is the Morse code resistance response diagram of the gelled ionic liquid electronic skin. Figure 22 a)-h) are letter signal response diagrams; Figure 22 i) in FIG. 1 is an SOS signal response diagram; Figure 22j) in FIG. 1 is the HELLO HITER signal response diagram;

[0049] Figure 23 The critical spacing test and response results of the electronic skin unit;

[0050] Figure 24 This is the research result of static load detection performance of gelled ionic liquid electronic skin 4×3 array. Figure 24 a)-c) are the test results of gelled ionic liquid electronic skin under four-point load, eight-point load and twelve-point load at -50℃ respectively. Figure 24 d)-f) Visualization of the resistance response of the HIT letter model;

[0051] Figure 25 The test results of the responsiveness of the 4×3 array of gelled ionic liquid electronic skin to sliding speed are shown below. Figure 25 a) is the resistance response result at different load positions when the metal ball slides on the gelled ionic liquid electronic skin. Figure 25 b) is the relationship between the sliding load of the metal ball on the gelled ionic liquid electronic skin and the rolling speed of the metal ball;

[0052] Figure 26 This is the 3D histogram response result of the dynamic single-point sliding of the gelled ionic liquid electronic skin 4×3 array. Figure 26 a)-i) The resistance response diagram of the gelled ionic liquid electronic skin during SOS sliding trajectory in a -50℃ environment;

[0053] Figure 27 This is the research result of multi-point simultaneous sliding detection of gelled ionic liquid electronic skin 4×3 array. Figure 27 Figures a)-d) are the pressure load response results at different positions of the ionic liquid flexible sensor array when the finger slides at three points under a -50°C environment;

[0054] Figure 28 The results of the simultaneous sliding resistance change of multiple points of the gelled ionic liquid electronic skin 4×3 array are shown. Figure 28 Figures a)-c) are the pressure load response results at different positions of the ionic liquid flexible sensor array when the finger slides at four points under a -50°C environment;

[0055] Figure 29 The resistance responses of the three electronic skin units corresponding to different finger bending angles;

[0056] Figure 30 This is the research result of the application of sign language gesture recognition in gelled ionic liquid electronic skin aerospace gloves. Figure 30 a) is a physical picture of the space glove and the location distribution of the sensor units. Figure 30 b) is the resistance response of T1 unit in the gesture number "1". Figure 30 c) is the resistance response of the M1 unit in the gesture number "1";

[0057] Figure 31 This is the resistance change curve of the 12 electronic skin units of the space glove during digital sign language movements;

[0058] Figure 32 This is the resistance change curve of the 12 electronic skin units of the space glove during complex and continuous sign language movements. DETAILED DESCRIPTION

[0059] The present invention provides a method for preparing a gelled ionic liquid, comprising the following steps:

[0060] 1-Butyl-3-methylimidazolium tetrafluoroborate and N,N'-bis(2-hydroxyethyl)oxalamide are mixed and gelled to obtain a gelled ionic liquid.

[0061] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0062] In the present invention, the mass percentage of the N,N'-bis(2-hydroxyethyl)oxamide to the mass percentage of the 1-butyl-3-methylimidazolium tetrafluoroborate is preferably 1-10wt%, more preferably 3-10wt%, and specifically preferably 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 7wt%, or 10wt%. The gelation is carried out under oil bath conditions, and the gelation temperature is preferably 90-150°C, specifically preferably 90°C, 120°C, or 150°C; the holding time is preferably 28-32 minutes, specifically preferably 30 minutes. After the gelation is completed, the present invention preferably allows the gelled product to stand and cool to room temperature to obtain the gelled ionic liquid.

[0063] The present invention provides a gelled ionic liquid prepared by the preparation method described in the above technical solution.

[0064] The present invention provides the use of the gelled ionic liquid described in the above technical solution as a conductive material in the preparation of electronic skin.

[0065] The present invention provides a gelled ionic liquid electronic skin, comprising a stacked flexible upper packaging layer and a flexible lower packaging layer, wherein the inner surface of the flexible upper packaging layer is provided with a plurality of circuit channel units, each of which is formed by circuit channels, and the flexible lower packaging layer encapsulates the circuit channels;

[0066] The gelled ionic liquid electronic skin further includes a conductive material filled in the circuit channel, and the conductive material is the gelled ionic liquid described in the above technical solution.

[0067] The gelled ionic liquid electronic skin provided by the present invention comprises a flexible upper encapsulation layer and a flexible lower encapsulation layer arranged in a stacked manner. In the present invention, the flexible upper encapsulation layer and the flexible lower encapsulation layer are stacked to form an encapsulation body. The material of the flexible upper encapsulation layer is preferably platinum-catalyzed silica gel (Ecoflex); the thickness of the flexible upper encapsulation layer is preferably 0.05 to 0.25 cm, preferably 0.15 to 0.25 cm. Specifically, 0.05 cm, 0.1 cm, 0.15 cm, 0.2 cm, or 0.25 cm are preferred. The material of the flexible lower encapsulation layer is preferably polydimethylsiloxane (PDMS), and the present invention has no special requirements for the thickness of the flexible lower encapsulation layer. The inner surface of the flexible upper encapsulation layer is provided with a plurality of line channel units, each of which is formed by line channels, and the flexible lower encapsulation layer encapsulates the line channels. The thickness of the flexible upper encapsulation layer is the thickness of the line channel portion of the flexible upper encapsulation layer, that is, the remaining thickness after subtracting the depth of the line channels from the overall thickness of the flexible upper encapsulation layer. The inner surface of the flexible upper encapsulation layer is the surface where the flexible upper encapsulation layer contacts the flexible lower encapsulation layer.

[0068] In the present invention, the cross-section of the circuit channel is preferably square, and the cross-sectional side length of the circuit channel is preferably 0.1 to 0.4 cm, and specifically preferably 0.1 cm, 0.15 cm, 0.2 cm, 0.3 cm or 0.4 cm. The cross-sectional dimensions of the circuit channel are specifically preferably 0.1×0.1, 0.15×0.15, 0.2×0.2, 0.3×0.3, 0.4×0.4 cm. In the present invention, the circuit channel forming the circuit channel unit forms a circular spiral pattern, and the radius of the circular spiral pattern is preferably 1.5 cm; the area percentage of the circuit channel in the circular spiral pattern is preferably 17.6 to 29.3%, and more preferably 29.3% (such as Figure 11 The number of spiral turns of the circuit channel in the circular spiral pattern is preferably 5 (as shown in the rightmost circular spiral pattern in FIG. Figure 11 The area percentage of the circuit channel in the circular spiral pattern is the projected area of ​​the circuit channel in the circular spiral pattern divided by the total area of ​​the circular spiral pattern.

[0069] In the present invention, the number of the line channel units is preferably ≥2, and in the embodiment, preferably 12. When the number of the line channel units is ≥2, the line channel units are arranged in an array, and in the embodiment, they are arranged in a 3×4 rectangular array. The spacing between two adjacent line channel units is ≥1.4cm. The spacing between two adjacent line channel units is the straight-line spacing between the coaxial edges of the centers of the two adjacent line channel units (such as Figure 23 (as shown in the illustration in ).

[0070] The present invention provides a method for preparing the gelled ionic liquid electronic skin described in the above technical solution, comprising the following steps:

[0071] The upper packaging layer template and the lower packaging layer template are obtained by 3D printing;

[0072] Using a template method, the upper packaging layer template and the lower packaging layer template are used to prepare a flexible upper packaging layer and a flexible lower packaging layer in an uncured state respectively;

[0073] Laying the flexible upper packaging layer and the flexible lower packaging layer in an uncured state on top of each other and bonding them to obtain a semi-finished product;

[0074] Conductive material is injected into the circuit channel of the semi-finished product to obtain the gelled ionic liquid electronic skin.

[0075] The present invention uses a 3D printing method to obtain the upper encapsulation layer template and the lower encapsulation layer template. The present invention has no special requirements for the specific implementation of the 3D printing. In the present invention, the raw material used for the 3D printing is preferably a photosensitive resin.

[0076] After obtaining the upper encapsulation layer template and the lower encapsulation layer template, the present invention adopts a template method to prepare a flexible upper encapsulation layer and a flexible lower encapsulation layer in an uncured state respectively using the upper encapsulation layer template and the encapsulation layer template.

[0077] In the present invention, the template method for preparing the flexible upper encapsulation layer preferably includes the following steps: mixing components A and B of platinum-catalyzed silicone rubber, applying the mixture to the upper encapsulation layer template, and then thermally curing and demolding to obtain the flexible upper encapsulation layer. In the present invention, the mass ratio of components A to B is preferably 1:1. The thermal curing temperature is preferably 60°C, and the curing time is preferably 15 minutes.

[0078] In the present invention, the template method for preparing an uncured flexible lower encapsulation layer preferably includes the following steps: mixing a base component of polydimethylsiloxane with a curing agent, applying the mixture to a lower encapsulation layer template, and then thermally curing and demolding to obtain an uncured flexible lower encapsulation layer. In the present invention, the mass ratio of the base component to the curing agent is preferably 10:1. The thermal curing temperature is preferably 60°C, and the curing time is preferably 45 minutes. The surface of the uncured flexible lower encapsulation layer has a certain degree of stickiness.

[0079] After obtaining the flexible upper encapsulation layer and the uncured flexible lower encapsulation layer, the present invention stacks the flexible upper encapsulation layer and the uncured flexible lower encapsulation layer and then bonds them to obtain a semi-finished product. In the present invention, the bonding temperature is preferably 60°C and the bonding time is preferably 25 minutes.

[0080] A semi-finished product is obtained. The present invention injects a conductive material into the circuit channels of the semi-finished product to obtain the gelled ionic liquid electronic skin. In the present invention, the injection is preferably performed using a medical syringe. After the conductive material is injected, the present invention preferably uses copper wire as an electrode, which is embedded in the gelled ionic liquid from the channel opening and then led out. The product is then sealed with a sealant and dried to obtain the gelled ionic liquid electronic skin. The sealant is specifically epoxy resin AB glue. The product is dried naturally in a well-ventilated area. The drying time is preferably 6 hours.

[0081] The present invention provides the application of the gelled ionic liquid electronic skin described in the above technical solution or the gelled ionic liquid electronic skin prepared by the preparation method described in the above technical solution in wearable sensors for human-computer interaction, motion recognition or non-therapeutic and non-diagnostic purposes.

[0082] In the present invention, the gelled ionic liquid electronic skin is specifically applied to Morse code information transmission and sign language gesture recognition in an ultra-low temperature environment, wherein the application environment temperature of the sign language gesture recognition in the ultra-low temperature environment is preferably -50°C. The sign language gesture recognition in the ultra-low temperature environment is specifically applied to aerospace glove gesture recognition.

[0083] The gelled ionic liquid electronic skin provided by the present invention is a high-performance, stretchable electronic skin with a wide temperature detection range and low leakage resistance. When the number of sensing units in the gelled ionic liquid electronic skin is one (single-unit gelled ionic liquid electronic skin), it can be used for Morse code information transmission. When the number of sensing units in the gelled ionic liquid electronic skin is two or more (array-unit gelled ionic liquid electronic skin), it can be used for sign language gesture recognition in ultra-low temperature environments.

[0084] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0085] The preparation process of gelled ionic liquid electronic skin in the following examples is as follows: Figure 2 The experimental materials and equipment used in the following examples include:

[0086] This invention primarily utilizes 3D printing technology and a template removal method to prepare a flexible polymer substrate with an embedded hollow circuit channel. This substrate is then infused with a gelled ionic liquid to produce a high-performance flexible electronic skin with wide-temperature detection capabilities. The main materials used in the actual preparation process are 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid ([BMIM]BF4), N,N'-bis(2-hydroxyethyl)oxamide, polydimethylsiloxane (PDMS), platinum-catalyzed silicone rubber (Ecoflex-0030), PLA (Polylactic acid), 0.05 cm diameter copper wire, anhydrous ethanol, ultrapure water, and ABS (Acrylonitr Butadiene Styrene). The relevant materials involved in the experiment, their purity, and manufacturer information are shown in Table 1.

[0087] Table 1 Main materials required for the experiment

[0088]

[0089] The template removal method for preparing the upper and lower encapsulation layers of gelled ionic liquid electronic skin primarily utilizes a melt extrusion 3D printer, a vacuum drying oven, a UV curing chamber, an electronic analytical balance, a water purifier, and a syringe. The gelled ionic liquid is primarily prepared using an oil bath and an electronic analytical balance. The sensitivity and other performance characterization of the gelled ionic liquid electronic skin are primarily performed using a DCM6510 pattern sampling multimeter, an optical microscope, an ultra-low temperature freezer, a function signal generator, a power amplifier, an oscillator, a stepping and stretching platform, and a vacuum glove box. The application performance characterization of gelled ionic liquid integrated arrays (including static and dynamic load detection performance studies of a 4×3 array of gelled ionic liquid electronic skin and gesture recognition applications in aerospace gloves) primarily utilizes an ultra-low temperature freezer and a pattern sampling multimeter. Table 2 lists the instruments used in the experiments.

[0090] Table 2 Main equipment and instruments required for the experiment

[0091]

[0092] Example 1

[0093] 3g of [BMIM][BF4] ionic liquid was thoroughly mixed with DEA, where the mass percentage of DEA to the mass of [BMIM][BF4] ionic liquid was 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 7wt%, and 10wt% respectively. The mixture was then heated in an oil bath at 90°C, 120°C, and 150°C for 30 min, respectively. After heating, the mixture was removed from the oil bath and allowed to cool for 1 h. The mixture was then allowed to cool to room temperature and observed to determine whether gelation of the ionic liquid had occurred. The gelation temperature and time were recorded using a handheld infrared temperature detector and a timer.

[0094] During the preparation of the gelled ionic liquid described in Example 1, two process parameters critically influence the final gel formation: heating temperature and crosslinker concentration. The present invention investigates these two influencing factors. The present invention mixes the crosslinker and ionic liquid and heats the mixture in an oil bath until the crosslinker dissolves, resulting in a clear, colorless, and transparent liquid. The mixture is then cooled to room temperature to yield a translucent gel. Inverting the test tube indicates that no flow occurs, indicating the gelled ionic liquid has been prepared.

[0095] (1) Study on the influence of oil bath temperature on the preparation of gelled ionic liquid conductive materials

[0096] First, Example 1 investigated the effect of heating temperature on the preparation of gelled ionic liquids. A 5 wt% crosslinker was added to 3 g of ionic liquid and thoroughly mixed. The mixture was then heated in an oil bath at 90°C, 120°C, and 150°C for 30 min. After heating, the mixture was removed from the oil bath and allowed to stand at room temperature for 1 h. Figure 3 a)-c) are ionic liquids with a DEA concentration of 5 wt% after heating at 90°C, 120°C, and 150°C, respectively. Figure 3 d)-f) in the above are the products after heating and cooling at 90℃, 120℃ and 150℃ respectively. Figure 3 As can be seen from a) in the figure, when heated at 90°C, the mixture separated into two phases and after standing for 1 hour, all the added cross-linking agent precipitated, indicating that gelation could not be completed under the heating condition of 90°C. Figure 3 As shown in b), under heating conditions at 120°C, the cross-linking agent was partially dissolved and the mixture was in an opaque liquid state. After standing for two hours, there was no obvious change, the fluidity was reduced, but the gelation was not sufficient. Figure 3 As can be seen in c), under the heating condition of 150°C, bis-hydroxyethyl-oxalamide is completely dissolved in the ionic liquid, and the mixture is a colorless and transparent liquid. After standing for a period of time at room temperature and then inverted, it can be seen that the mixture completely loses its fluidity, that is, forms a gel.

[0097] It can be seen from the examples that the DEA crosslinker can be completely dissolved and form a gel at 150°C, but the [BMIM][BF4] ionic liquid gel cannot be prepared at low temperatures. Therefore, the product used in Example 2 is the product in Example 1 with the heating conditions set to 150°C oil bath heating for 30 minutes.

[0098] (2) Study on the influence of DEA concentration on the preparation of gelled ionic liquid conductive materials

[0099] DEA was added to 3g of ionic liquid at concentrations of 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 7wt%, and 10wt%, respectively. After thorough mixing, the mixture was heated in an oil bath at 150°C for 30 minutes and allowed to stand at room temperature for 1 hour to cool sufficiently. During the experiment in Example 1, the present invention recorded the time of gelation onset and the temperature using a handheld infrared temperature detector. The data were summarized to obtain Figure 4 .

[0100] from Figure 4 It can be seen that although the temperature conditions have been met, no gel formation was observed when the cross-linker concentration was 1 wt% and 2 wt%. Gel was formed only when the cross-linker concentration reached 3 wt% or above. Therefore, Example 1 determined that the critical minimum concentration of the cross-linker was 3 wt%. As the cross-linker content increased, the time required for gelation decreased inversely, while the critical temperature at which gel began to form increased in direct proportion.

[0101] This embodiment improves the leakage problem of the ionic liquid itself due to its strong fluidity by gelling the ionic liquid. Dynamic viscosity refers to the measurement of the internal friction generated between molecules when the liquid moves under the action of external force. It can be used to characterize the anti-flow ability of a substance. The greater the dynamic viscosity, the stronger the anti-flow ability. The present invention uses a rheometer to test the dynamic viscosity of gelled [BMIM][BF4] ionic liquids and [BMIM][BF4] ionic liquids with different crosslinker concentrations of 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 7wt%, 10wt%. The test results are as follows Figure 5 . Figure 5 Different DEA concentrations are the percentage of DEA mass to the mass of [BMIM][BF4] ionic liquid.

[0102] As the shear rate increases, the dynamic viscosity of the [BMIM][BF4] ionic liquid remains essentially unchanged at approximately 63 mPa·s. After gelation, the dynamic viscosity at low shear rates increases by four orders of magnitude, from 101 to 105, and the crosslinker concentration is proportional to the dynamic viscosity. As the conductive material for electronic skin, the gelled ionic liquid is encapsulated within the device housing within the channel, experiencing a low shear stress rate and high dynamic viscosity. Therefore, injecting the gelled ionic liquid into the channel can significantly alleviate the leakage issues that ionic liquids, often associated with high-flow fluids, often experience. At the same time, the dynamic viscosity of the gelled ionic liquid gradually decreases with increasing shear rate, ultimately approaching a stable value, exhibiting shear-thinning fluid properties. This characteristic makes injection and filling with gelled ionic liquids a convenient and effective method for electronic skin preparation.

[0103] (3) Study on the resistance stability of gelled ionic liquids

[0104] Resistance drift (ΔR / R0) refers to the unwanted resistance change in the output that is unrelated to the input under the interference of the external environment, which has a significant impact on the detection performance of the electronic skin. As a conductive material for electronic skin, gelled ionic liquids are required to have stable electrical properties. The present invention studies the resistance drift of [BMIM][BF4] ionic liquids before and after gelation. The present invention prepares straight channel electronic skin devices with inner diameters of circuit channels of 0.1×0.1, 0.15×0.15, 0.2×0.2, 0.3×0.3, and 0.4×0.4 cm, respectively. Pure ionic liquid and gelled ionic liquid with a concentration of 3wt% DEA are respectively perfused into the circuit channels and packaged. The wires are connected to a Keithley DCM6510 graphic sampling multimeter, and the resistance change under the action of an external electric field and no pressure load is tested using a four-wire resistance method. The specific experimental results are as follows. Figure 6 shown.

[0105] from Figure 6 As can be seen from the graph, the resistance of both gelled ionic liquid electronic skin and ionic liquid electronic skin continuously rises from the lowest point, with the upward trend gradually decreasing from fast to slow. The resistance drift rate of electronic skin with a small circuit channel inner diameter changes more slowly. As the circuit channel inner diameter gradually increases, the corresponding electronic skin's resistance drift rate changes more rapidly at the extreme value. The resistance of gelled ionic liquid electronic skin tends to be fixed under different circuit channel inner diameters, while the resistance of ionic liquid electronic skin continues to climb when the channel inner diameter is large.

[0106] The drift resistivity and drift time data of the two devices when the resistance is close to a fixed value are extracted and compared, and the results are obtained. Figure 7 .from Figure 7As can be seen from a) in the figure, the resistance drift time of the gelled ionic liquid is reduced compared to the ionic liquid itself at different channel inner diameters. When the channel inner diameter is 0.1 cm, the resistance drift time decreases by up to 3 orders of magnitude from 111s to 0.28s. Figure 7 As can be seen in b), when comparing the two conductive materials, the resistance drift rate of the gelled ionic liquid also decreases, from 0.115 to 0.001 at a channel inner diameter of 0.1 cm, a decrease of up to 2 orders of magnitude. Overall, the performance after gelation is greatly improved compared to the electrical properties of the ionic liquid itself. The reason for this phenomenon is that after gelation, the gel network restricts the free flow of the ionic liquid, so the resistance drift phenomenon is effectively suppressed, improving the stability of the electronic skin device. Gelated ionic liquids exhibit more excellent electrical properties as conductive materials and have broad application prospects in the preparation of electronic skin.

[0107] In summary, temperature and crosslinker concentration have a key influence on the formation of gelled ionic liquids. While gel formation was not observed at a relatively low temperature of 90°C and 120°C, gel formation was achieved at an oil bath temperature of 150°C. 3 wt% is the critical gel concentration, and a crosslinker concentration greater than 3 wt% results in a stable gelled ionic liquid. In Example 2, a gelled ionic liquid was obtained using a crosslinker concentration of 3 wt% and heating conditions at 150°C in an oil bath for 30 minutes.

[0108] Example 2

[0109] Electronic skin can fit tightly to the surface of the human body, and it still needs to maintain close conformal contact when the human body moves, so there are high requirements for the stretchability of the packaging substrate material. In this embodiment, Ecoflex is selected to make the upper packaging layer of the electronic skin. Ecoflex has an elongation at break of up to 900%, is easy to demold, and can maintain a good circuit pattern integrity rate. PDMS is selected to make the lower packaging layer of the skin. PDMS has good biocompatibility and an elongation at break of 160%. It can be directly covered on the surface of the human body and has good deformation ability. Figure 2 The preparation of gelled ionic liquid electronic skin is mainly divided into the following steps:

[0110] Step 1): First, use a Hongrui X400 3D printer to print a mold with the desired pattern (the circuit channel unit formed by the circuit channels) and dimensions. Then, thoroughly mix Ecoflex components A and B in a 1:1 ratio and apply them to the mold. Place the mixture in a 60°C oven for approximately 15 minutes to fully cure. Remove the Ecoflex layer from the mold using a demolding method and set aside for later use. By varying the mass of the mixed Ecoflex components A and B, Ecoflex top encapsulation layers of varying thickness can be prepared.

[0111] Step 2): The lower encapsulation layer is also prepared using a 3D-printed removable template. A rectangular mold of pre-set specifications is printed using a 3D printer. PDMS is thoroughly mixed in a 10:1 ratio of base components to curing agent, then coated onto the mold. The mold is then placed horizontally in a 60°C oven and dried for approximately 45 minutes until the PDMS is semi-cured and has a certain degree of surface tack.

[0112] Step 3): Spread the previously prepared Ecoflex upper packaging layer completely on the PDMS lower packaging layer, press gently to make the upper and lower packaging layers fully fit together, and then place it horizontally in a 60°C oven to dry for about 25 minutes to allow the upper and lower layers of the device to fully solidify and bond, thereby obtaining an electronic skin packaging substrate (semi-finished product) with a hollow pipe (i.e., a circuit channel) inside.

[0113] Step 4): Use a medical syringe to inject the gelled ionic liquid prepared in Example 1 into the hollow channel reserved inside the electronic skin until it overflows to ensure that the entire circuit channel is completely filled. Use copper wire as an electrode to bury it in the gelled ionic liquid from the channel mouth and lead it out. Then use epoxy resin AB glue to seal it and naturally dry it in a ventilated place for 6 hours to obtain an electronic skin device with a certain circuit channel shape and filled with gelled ionic liquid.

[0114] In this embodiment, the cross-sectional dimensions of the circuit channels are 0.1×0.1, 0.15×0.15, 0.2×0.2, 0.3×0.3, and 0.4×0.4 cm, respectively. The thicknesses of the upper encapsulation layer are 0.05, 0.1, 0.15, 0.2, and 0.25 cm, respectively. The circuit channel unit is a circular spiral with a radius of 1.5 cm. The circuit channel area accounts for 7.9%, 13.7%, 17.6%, 23.4%, and 29.3% of the circular spiral, respectively. The number of circuit channel units is 1.

[0115] Detection sensitivity is one of the key indicators for measuring the detection performance of electronic skin. This example studies the factors that affect the detection sensitivity of gelled ionic liquid electronic skin, namely the inner diameter of the circuit channel, the thickness of the upper encapsulation layer, the area ratio of the circuit channel, and the crosslinker concentration.

[0116] (1) Study on the influence of circuit channel inner diameter on detection sensitivity

[0117] A Hongrui X400 3D printer was used to produce linear circuit channels with cross-sectional dimensions of 0.1×0.1, 0.15×0.15, 0.2×0.2, 0.3×0.3, 0.4×0.4 cm and a length of 4 cm. After infusing a gelled ionic liquid with a cross-linker concentration of 3wt%, copper wires of the same length were encapsulated and naturally cured and dried to produce an electronic skin device. In this embodiment, a gasket is placed on the electronic skin to ensure uniform force, and then weights are accumulated to simulate the scene when human skin is under pressure. In the preliminary experiment, when the weight exceeded 1000g, the surface pressure of the electronic skin was too large, and the difference in tensile properties between PDMS and Ecoflex caused deformation mismatch, which eventually damaged the device. The gasket area was about 3.1cm 2 According to the pressure calculation formula P=F / A, the upper limit of the detection pressure of the gelled electronic skin is 32000Pa.

[0118] In this embodiment, weights of 1000g, 500g, 200g, 100g, 50g, 20g, 10g, 5g, and 1g were added to the surface of the pad in sequence, with an interval of 1 minute. Then, a Keithley DCM6510 graphic sampling multimeter was used to record the change in the electronic skin resistance. The results are shown in Figure 2. Figure 8 Show.

[0119] from Figure 8 It can be seen that when the electronic skin is subjected to external force, a significant increase in resistance will occur. When weights of different masses are added, there are different resistance changes. The larger the weight, the greater the resistance change, which is consistent with the law of tactile response of human skin. The reason for this phenomenon is that when the electronic skin device is subjected to external force, the internal circuit channel will correspondingly deform, the inner diameter of the channel will shrink, and the gelled ionic liquid inside the channel will be squeezed, causing the resistance value to increase. As the inner diameter of the internal circuit channel of the electronic skin decreases, the resistance change caused by the accumulation of weights of the same mass increases. The 0.1×0.1cm electronic skin device has the largest resistance change when the same mass weights are added, that is, it has the highest sensitivity. At the same time, in the previous comparative experiments, the present invention found that the resistance drift rate of the channel inner diameter of 0.1×0.1cm is the smallest and the resistance drift time is the shortest. Therefore, in subsequent experiments, the present invention uses 0.1×0.1cm as the channel inner diameter size.

[0120] (2) Study on the influence of the thickness of the upper packaging layer on the detection sensitivity

[0121] Based on previous experimental results, when investigating the effect of the thickness of the Ecoflex upper encapsulation layer on the electronic skin's detection sensitivity, a mold with a circuit channel cross-section of 1 × 1 cm was used. By varying the mass of the mixed Ecoflex components A and B, Ecoflex upper encapsulation layers of varying thicknesses could be produced. Specific parameters are shown in Table 3.

[0122] Table 3 Main parameters of Ecoflex thickness of upper encapsulation layer

[0123] Thickness of upper packaging layer (cm) 0.05 0.1 0.15 0.2 0.25 Ecoflex mass (g) 2.9 3.9 4.9 5.9 6.9

[0124] After fabricating electronic skin devices with internal channels of 4 cm in length, cross-sectional dimensions of 1 × 1 cm, and varying encapsulation layer thicknesses, a gelled ionic liquid with a crosslinker concentration of 3 wt% was poured into the channels and copper wires of equal length were encapsulated. The devices were then cured and dried naturally to obtain the devices. After placing a gasket on the electronic skin to ensure uniform force, weights were added (weights were added sequentially from 1000 g, 500 g, 200 g, 100 g, 50 g, 20 g, 10 g, 5 g, and 2 g, with a 1-minute interval between weight additions). The resistance changes of the electronic skin were then recorded using a Keithley DCM6510 graphic sampling multimeter. The resistance change curve is shown in Figure 2. Figure 9 shown.

[0125] from Figure 9 The experimental results show that as the weights were added, electronic skins with different top encapsulation layer thicknesses all produced an electrical response to the applied pressure. Specifically, electronic skin with a top encapsulation layer thickness of 0.15 cm produced the largest resistance signal response compared to other thicknesses when subjected to the same pressure. This is because electronic skin thicker than 0.15 cm is more resistant to deformation and therefore experiences less deformation. In contrast, electronic skin with an overly thin top encapsulation layer exhibits primarily lateral deformation when squeezed, with minimal vertical deformation.

[0126] Figure 10 This is an enlarged schematic diagram of the resistance change curve of the Ecoflex electronic skin with a thickness of 0.15 cm when the weight is accumulated. Figure 10 The curve in the second half of a) is enlarged. The electronic skin with a 0.15cm thick upper encapsulation layer can detect the pressure of a 2g weight. The pad area is about 3.1cm. 2 According to the pressure calculation formula P=F / A, the pressure is 64Pa, and the enlarged diagram of the resistance change curve is as follows Figure 10 Therefore, in the subsequent experiments, the present invention selected a flexible sensor device with a circuit microchannel cross-section size of 0.1×0.1 cm and an upper packaging layer Ecoflex thickness of 0.15 cm for subsequent experimental research.

[0127] (3) Study on the impact of circuit channel area ratio on detection sensitivity

[0128] When exploring the influence of the circuit channel area ratio on the electronic skin detection sensitivity, the present invention designed and printed five circuit microchannels with different numbers of circles. The area ratio of the graphic channel was increased by increasing the number of circles. The specific parameters are shown in Table 4. The circuit channel schematic diagram is shown in Figure 11 shown.

[0129] Table 4 Main parameters of circuit channels with different area ratios

[0130] Number of laps 1 2 3 4 5 Channel area (%) 7.9 13.7 17.6 23.4 29.3

[0131] The electronic skin devices, with a circuit channel cross-section of 0.1 × 0.1 cm and an encapsulation layer thickness of 0.15 cm and different numbers of channels, were filled with gelled ionic liquid and encapsulated. Copper wires of equal length were placed, and spacers were placed to ensure uniform force. The resistance changes of these devices were characterized using a Keithley DCM6510 graphic sampling multimeter when weights were added (the weights were added in sequence from 100 g, 50 g, 25 g, 10 g, 5 g, 2 g, and 1 g, with an interval of 1 minute between weight additions). The specific resistance change results are shown in the figure below. Figure 12 As shown. The present invention can be seen that the resistance change of the electronic skin with five different pattern area ratios increases linearly with the increase of the weight mass. When the same mass weight is loaded, the resistance change of the electronic skin increases with the increase of the pattern area ratio, and the sensitivity is highest when the area ratio is 29.3%. Next, a linear fit is performed on the relationship between the resistance change and the weight of the weight, and the fitting results are shown as follows: Figure 12 As shown in (b), the fitting results are excellent, with R² values ​​of 0.993, 0.975, 0.982, 0.991, and 0.991, respectively, close to 1, indicating a good linear relationship. Furthermore, the slope of the fitting curve increases with the number of loops, from 0.612 to 0.741. This suggests that a higher pattern area percentage indicates a higher sensitivity. Therefore, in subsequent experiments, a five-loop channel with a pattern area percentage of 29.3% was used to fabricate the electronic skin device.

[0132] Subsequently, the present invention uses an electronic skin with a channel cross-sectional size of 0.1×0.1 cm, an upper encapsulation layer Ecoflex thickness of 0.15 cm, and a pattern area ratio of 29.3% to test its detection limit when applying external pressure. The specific experimental results are as follows: Figure 13The electronic skin encapsulating the gelled ionic liquid was connected to a Keithley DCM6510 graphic sampling multimeter with a wire, and the resistance change of the electronic skin when the weights were added (the weights were added in succession from 200g, 100g, 50g, 25g, 10g, 5g, 2g, 1g, 500mg, with an interval of 1min between weight additions) was detected using a four-wire resistance method. Figure 13 It can be seen that as the weight of the weight increases, the degree of resistance change gradually increases, and the detection limit of the gelled ionic liquid electronic skin for the weight is 500 mg, the gasket area is about 1.1 cm2, and according to the pressure calculation formula P=F / A, the electronic skin detection limit pressure is 48 Pa.

[0133] (4) Study on the effect of DEA concentration on detection sensitivity

[0134] The concentration of DEA has a key influence on the electrical properties of the gelled ionic liquid. According to the previous experimental results, the present invention has produced an electronic skin with an inner diameter of 0.1×0.1cm in the channel, a thickness of 0.15cm in the upper encapsulation layer Ecoflex, and a graphic area accounting for 29.3%. The gelled ionic liquids with DEA ​​concentrations of 3wt%, 4wt%, 5wt%, 7wt%, and 10wt% were respectively poured into the channel. The electronic skin was connected to a Keithley DCM6510 graphic sampling multimeter with a wire, and the four-wire resistance method was used to detect the resistance change of the electronic skin when weights were accumulated (the weights were added successively from 200g, 100g, 50g, 20g, 10g, 5g, 2g, 1g, and 500mg, and the interval time for adding weights was 1min). As Figure 14 As shown in a).

[0135] As DEA concentration increases, the electronic skin's resistance response decreases when loaded with the same weight, indicating a decrease in sensitivity. A crosslinker concentration of 3wt% exhibits the highest sensitivity, while a concentration of 10wt% exhibits the lowest. The lower pressure detection limit calculated using the pressure formula is 9600 Pa. The present inventors believe this phenomenon occurs because the gel network becomes denser and more resistant to deformation as DEA concentration increases, resulting in a smaller change in resistance. Furthermore, the high dynamic viscosity of the gel network restricts the flow of anions and cations in the ionic liquid, spatially confining them and hindering their free propagation. This can also affect their transmission between the electrode and the gel, thereby reducing the change in resistance.

[0136] The present invention performs a linear fitting on the relationship between the resistance change and the weight of the weight, such as Figure 14As shown in (b), the linear fit between the tissue change and the weight is good, with R² values ​​of 0.991, 0.997, 0.985, and 0.920, respectively, close to 1, indicating a good linear relationship. Furthermore, the slope of the fitting curve decreases with increasing crosslinker concentration, again demonstrating that sensitivity decreases with increasing crosslinker concentration, reaching peak sensitivity at 3 wt%. In subsequent experiments, a gelled ionic liquid with a DEA concentration of 3 wt% will be used as the conductive material.

[0137] (5) Study on the cyclic tensile mechanical properties of gelled ionic liquid electronic skin

[0138] Figure 15 The resistance change curve of the electronic skin after being stretched 1000 times under 50% strain. As a wearable device, electronic skin needs to be stretched repeatedly in application. In order to verify the cyclic stretching mechanical properties of gelled ionic liquid electronic skin, the present invention prepared a gelled ionic liquid electronic skin with a circuit channel inner diameter of 0.1×0.1cm, an upper packaging layer thickness of 0.15cm, a graphic area ratio of 29.3%, and a cross-linking agent concentration of 3wt%. The electronic skin was subjected to a 1000-cycle stretching test using a stepper machine under 50% strain and the resistance change curve was measured using a four-wire resistance method. The test results are shown as follows: Figure 15 As shown, the relative resistance of the electronic skin changes by less than 3% during 1000 cycles of stretching, which indicates that the electronic skin will not experience mechanical fatigue in a certain usage cycle, has good durability, and can meet application requirements.

[0139] (6) Research on the stability performance of gelled ionic liquid electronic skin in curved surface detection

[0140] Human skin is a curved surface environment, so the electronic skin needs to be able to maintain detection stability in the curved surface environment. Figure 16 As shown in a)-d) in the figure, the present invention studies the stability of gelled ionic liquid in curved surface environment detection, sets four curved surface environments of 0°, 30°, 60° and 90°, with the curved surface radius being infinite, 5.7cm, 2.9cm and 1.9cm respectively, and makes upper and lower gaskets, and clamps the gelled ionic liquid electronic skin inside when accumulating weights to ensure the degree of curvature. Figure 16 As shown in Figure e), the resistance response of the gelled ionic liquid electronic skin after the weight is applied under different curved surface environments is basically the same. The different initial resistances are because different curved surface environments give the electronic skin a certain initial deformation. The higher the degree of bending, the greater the deformation, and therefore the higher the initial resistance. The present invention further extracts the specific value of the response when pressure is loaded and fits it to obtain Figure 16The results in (f) above show that the overall resistance response to pressure loading under different curved surfaces follows a linear relationship, with R² = 0.965. These results indicate that the sensing performance of gelled ionic liquid electronic skin under different curved surfaces remains essentially the same as that under flat conditions, and that this performance is not significantly affected in practical curved surface applications.

[0141] (7) Study on the wide temperature range detection performance of gelled ionic liquid electronic skin

[0142] [BMIM][BF4] ionic liquid has the physical properties of wide temperature range and low melting point, which gives the gelled [BMIM][BF4] ionic liquid electronic skin good wide temperature range detection performance. The present invention uses an ultra-low temperature experimental refrigerator to build a low-temperature environment, and places the electronic skin connected to the multimeter through a wire on the experimental platform in the refrigerator and keeps it at a constant temperature for 45 minutes to ensure that the device temperature is consistent with the refrigerator refrigeration temperature. An electrically controlled heating platform is used to build an environment above room temperature of 50°C, and it is placed for 45 minutes to ensure that the temperature is consistent with the platform. Then, at different temperatures (-50°C, -30°C, -10°C, 10°C, 30°C, 50°C), the electronic skin is tested for changes in resistance during the process of successively adding weights (50g, 20g, 10g, 5g, 2g, 1g, and the interval time for adding weights is 1 minute). The experimental results are as follows: Figure 17 As shown in a).

[0143] When the same pressure is applied to the electronic skin at different temperatures, its electrical resistance response is different. The lower the temperature, the greater the resistance change. The resistance change corresponding to the electronic skin at different temperatures when different weights are applied is linearly fitted, and the results are as follows: Figure 17 As shown in b). Figure 17 Figure b) shows that the electronic skin's resistance change increases linearly with increasing weight at all five temperatures. The resulting R2 from 30°C to -50°C is 0.987, 0.999, 0.995, 0.977, and 0.995, close to 1, indicating a good fit. Furthermore, the slope of the linear fitting curve of resistance change versus applied pressure increases from 0.783 to 0.973 as temperature decreases. This indicates that the flexible pressure sensor exhibits improved electrical response characteristics at ultra-low temperatures. This is because at low temperatures, the movement of anions and cations is slow, increasing resistance, resulting in a greater resistance change for the same deformation.

[0144] The present invention studies the resistance response time of gelled ionic liquid electronic skin when different loads are added at different temperatures. The low temperature environment is built using an ultra-low temperature experimental refrigerator, and the high temperature environment is built using an electrically controlled heating platform. At different temperatures (-50℃, -30℃, -10℃, 30℃, 50℃), the resistance change of the electronic skin when weights (100g, 50g, 20g, 10g, 5g, 1g) are added is tested. The experimental results are as follows: Figure 18 As shown. When the same pressure load is applied, the lower the external ambient temperature, the longer the electronic skin's response time. This is because the thermal motion of anions and cations in ionic liquids is slow at low temperatures, and it takes more time to reach a stable state. After 30°C, the response time does not continue to shorten, and when the temperature rises to a certain level, it will far exceed the melting point. At this time, the anions and cations are already very active. In addition, at the same external ambient temperature, the greater the applied pressure load, the longer the electronic skin's resistance response time. Among them, the minimum resistance response time of the electronic skin when a 1g mass weight is applied at 30°C is 0.07s.

[0145] (8) Study on the low-frequency deformation response performance of gelled ionic liquid electronic skin

[0146] Electronic skin is widely used in the detection of physiological signals of living organisms, and is of great significance to the prevention and early diagnosis of diseases of living organisms. Therefore, the electronic skin of the present invention needs to have the ability to detect signals of different waveforms and different frequencies. A waveform generator, an oscillator and a signal generator are used to output and amplify low-frequency vibrations with frequencies of 0.5Hz, 1Hz, 2Hz, 3Hz and 4Hz, an amplitude of 2vpp, and waveforms of triangular waves and sine waves to simulate the corresponding deformations produced by the physiological signals of living organisms. The Keithley DCM6510 graphic sampling multimeter was used to test the resistance changes of the gelled ionic liquid electronic skin when sine waves and triangular waves of different frequencies were applied. The test results are as follows: Figure 19 As shown. Figure 19 It can be seen that the electronic skin device has a good response to both triangular wave and sine wave signals from 0.5Hz to 4Hz, and the curve is smooth and distortion-free, indicating that the electronic skin can detect vibration signals of different frequencies and waveforms.

[0147] (9) Damage redundancy detection performance of gelled ionic liquid electronic skin

[0148] As a wearable device, gelled ionic liquid electronic skin is directly attached to the surface of human skin. Just as human skin can be injured and damaged, electronic skin also needs to have a certain degree of damage redundancy detection capability. The present invention makes two holes with a diameter of about 0.05 cm on the surface of the circuit channel of the upper packaging layer of the gelled ionic liquid electronic skin to simulate human skin injuries and damage. Figure 20 shown.

[0149] The present invention first studies the detection performance of gelled ionic liquid electronic skin after damage in a normal temperature and pressure environment (temperature 25°C, air pressure 100kPa). Two pieces of electronic skin made in the same way are used for a control experiment. One piece is sealed intact, and two holes are dug in the packaging layer of the other piece to simulate damage. Weights of the same mass are placed on the two pieces of electronic skin, in order of 2g, 5g, 10g, 20g, 50g, 100g, and 200g, and the four-wire resistance method is used to measure the resistance change. Figure 21 In a) of the present invention, the resistance change of the damaged electronic skin when placed with weights of 2g, 5g, 10g, 20g, and 50g was consistent with that of the intact electronic skin, maintaining accurate detection capabilities. When a 100g weight was placed, the resistance of the damaged electronic skin increased by approximately 80.6% of that of the intact electronic skin, a significant deviation. When the weight was increased to 200g, the resistance increase was 63.7% of that of the intact electronic skin, with an even greater resistance deviation. Under normal temperature and pressure, the gelled ionic liquid electronic skin, even in a damaged state with two holes, maintained a certain level of redundant detection capability, with a detection limit of 50g. The pressure calculated using the formula P = F / A is 4800Pa.

[0150] The gelled ionic liquid electronic skin has low-temperature detection capabilities. The present invention conducted a control test on intact electronic skin and damaged electronic skin by placing weights at -50°C and measuring their resistance changes. The measurement results are as follows: Figure 21 As shown in Figure b), when the weight is less than 50g, the resistance response of the damaged electronic skin is consistent with that of the intact electronic skin, demonstrating accurate detection of damaged electronic skin. When the weight is 100g and 200g, the resistance change of the damaged electronic skin is 75.0% and 56.7% of that of the intact electronic skin, respectively, representing significant deviations. Experimental results show that under a -50°C ambient pressure environment, the redundant detection capability of the damaged electronic skin is 50g. Using the formula P = F / A, the pressure is calculated to be 4800Pa, indicating no significant impact from the low temperature environment.

[0151] The vacuum environment has a low pressure. When the electronic skin is damaged, a large pressure difference will be generated inside and outside the hole, which puts higher requirements on the redundancy detection capability of the electronic skin. The air pressure in the vacuum glove box can reach as low as 10Pa, which is a low vacuum environment. The present invention conducts a weight placement comparison test on two pieces of electronic skin in the box and records the resistance change. The experimental results are as follows: Figure 21 As shown in Figure c), the detection limit of the damaged electronic skin is 50g, and the pressure calculated using the formula P = F / A is 4800 Pa. When weights of 100g and 200g are placed, the resistance changes of the damaged electronic skin are 86.2% and 64.8% of that of the intact electronic skin, respectively.

[0152] In the glove box, two pieces of electronic skin were placed in a -10℃ ice salt bath and then subjected to a low-temperature vacuum environment simulation. A weight placement experiment was conducted and the resistance change was recorded. The results are as follows: Figure 21 In (d) above, the detection limit for the damaged electronic skin remains at 50g, and using the formula P = F / A, the pressure is calculated to be 4800 Pa. When the weights are 100g and 200g, the resistance changes of the damaged electronic skin are 63% and 60% of that of the intact electronic skin, respectively.

[0153] Through experiments, we can know that gelled ionic liquid electronic skin is similar to human skin. Even after having two damages, it can still accurately detect the pressure load within a certain range. The detection limit is 4800Pa, and the vacuum environment and low temperature have no obvious effect on the redundant detection capability of damage.

[0154] (10) Research on the application performance of gelled ionic liquid electronic skin Morse code

[0155] Morse code is a widely used means of communication and information encryption technology. Its core information is transmitted by waveform signals of varying lengths and a certain frequency. Electronic skin responds well to touch signals of different waveforms and frequencies. As a wearable device, it can transmit signals by applying pressure to the surface of the device. An electronic skin with a channel cross-sectional size of 0.1 cm, an upper packaging layer of 0.15 cm, a graphic area of ​​29.3%, and a DEA concentration of 3 wt% is prepared. Copper wires are used to lead out and then connected to a multimeter to measure the change in resistance after pressure is applied. A short press on the electronic skin to apply sudden pressure can obtain a short peak signal. A long press on the electronic skin to keep it still and apply static pressure for 3s can obtain a 3s stable long signal. The present invention controls the signal interval frequency to 1s, and inputs signals to the electronic skin according to the Morse code table. The resistance change of the electronic skin is measured as follows: Figure 22 As shown, in Figure 22 In a)-h), the electronic skin can accurately respond to small-scale text information of single letters such as H, L, T, I, R, S, O, and E. Taking the relatively complex L as an example, its Morse code is "·-···", that is, the present invention needs to apply sudden change pressure to the electronic skin once, then apply static pressure for 3s, and finally apply sudden change pressure three times again with an interval of 1s. Figure 22 As can be seen from b) of the present invention, the short peak signal responds quickly and can accurately detect the application and removal of the pressure load. At the same time, the response to the long signal is also smooth and stable, and the input of small-scale text signals can be accurately recognized.

[0156] Later, the present invention studied the response of gelled ionic liquid electronic skin to large-scale text signals such as letter combinations and long sentences, inputting the corresponding pressure load according to the Morse code, and measuring the resistance waveform change using the four-wire resistance method, such as Figure 22 i) and Figure 22 As shown in j), the gelled ionic liquid electronic skin can accurately recognize and respond to text messages such as "SOS" and "HELLOHITER".

[0157] The gelled ionic liquid electronic skin has the ability to respond sensitively and stably to pressure loads of different frequencies, showing application potential in the field of Morse code. It is expected to be used in the future for information exchange and communication in emergency and special scenarios such as underwater and extreme cold.

[0158] Example 3

[0159] The preparation method is basically the same as that of Example 2, except that: the number of line channel units is 12, forming a 4×3 rectangular array, the distance d between two adjacent line channel units is 1.4 cm, and the distance between the center points of two adjacent units is d=4.4 cm.

[0160] This example integrates gelled ionic liquid electronic skin units into a large-scale 3×4 integrated array and studies their detection performance, specifically characterizing multi-point static touch and multi-point sliding touch. The small-scale integration capabilities of the gelled ionic liquid electronic skin were then investigated and applied to gesture recognition in aerospace gloves.

[0161] (1) Research on the critical spacing of gelled ionic liquid electronic skin sensor arrays

[0162] The present invention integrates gelled ionic liquid electronic skin units into an arrayed electronic skin. It is necessary to determine the critical distance between two adjacent sensor units to ensure that there is no signal interference between them when pressure is applied. To this end, the present invention prepares Figure 23 For the sample shown, a pressure load of 32000Pa is applied to the gelled ion unit on one side, and the resistance signal response of the unit on the right side is measured. Figure 23As shown, when a pressure load is applied when the spacing d is 0.2cm-1.2cm, due to the continuous passivation layer on the Ecoflex, the right unit is also subjected to the transmitted stress and the circuit channel is deformed, thereby showing a phenomenon of increased resistance. In this case, the two units have a mutual influence, that is, crosstalk occurs. When the spacing d reaches 1.4cm, the distance is large enough so that the right unit is almost not deformed by the pressure load of the left unit, so the resistance signal of the unit always maintains a relatively stable state, and no crosstalk occurs. Therefore, the present invention determines that the critical spacing d of the electronic skin sensing unit is 1.4cm. In this case, the different units of the arrayed electronic skin prepared can achieve independent sensing without crosstalk.

[0163] The gelled ionic liquid electronic skin prepared in Example 2 has the advantages of high sensitivity, high stability, and adaptability to various temperature environments. However, it still has disadvantages such as a small sensing area and a small number of signals, making it unable to accurately identify large objects or moving objects. Therefore, in Example 3, the gelled ionic liquid units were integrated into an arrayed electronic skin and its static and dynamic detection performance was studied.

[0164] (2) Study on the static load detection performance of gelled ionic liquid electronic skin 4×3 array

[0165] In Example 3, a 4×3 array of gelled ionic liquid electronic skin was prepared using a template removal method. Static pressure loading experiments were performed to characterize its multi-touch sensing capability. A -50°C ultra-low temperature environment was established using an ultra-low temperature freezer. Four-point, eight-point, and twelve-point pressure loading were performed on the electronic skin using weights of 1g, 5g, 10g, 20g, 40g, 60g, 80g, 100g, 120g, 140g, 160g, and 180g, respectively. The resistance change was measured in real time using a Keithley DCM6510 graphic sampling multimeter.

[0166] exist Figure 24 In a), the present invention loads weights of 1g, 10g, 60g and 100g on the four units of the electronic skin, respectively, and obtains the four-point pressure loading response results; Figure 24 In b), the present invention loads weights of 1g, 5g, 10g, 40g, 60g, 100g, 140g and 180g on the eight sensing units of the electronic skin, and obtains eight-point pressure loading response results; Figure 24In c), the present invention simultaneously loads weights of 1g, 5g, 10g, 20g, 40g, 60g, 80g, 100g, 120g, 140g, 160g and 180g on the twelve flexible sensing units of the electronic skin array, and finally obtains the response results of all twelve units being loaded at the same time.

[0167] In addition, by sorting out the data, it was found that there is a good linear relationship between the resistance increment of the electronic skin and the loaded weight: y = 49.5x, where y is the resistance increment in kilo-ohms (KΩ), x is the mass of the loaded weight in grams (g), and the area of ​​the weight pad is 1.04 cm 2 , gravitational acceleration g = 9.80 m / s 2 According to the pressure calculation formula P = F / A, the linear relationship between the resistance increment of the electronic skin and the loading pressure is y = 0.05p, where p is the pressure in Pascal (Pa). Therefore, the directly obtained resistance increment can be converted into the measured value of the pressure applied to the unit through the above linear relationship. Finally, we get Figure 24 Histograms of multi-point loading responses shown in d)-f). Figure 24 The test results in Figures d)-f) show that the ionic liquid sensor array can generate a corresponding pressure load response under different pressure loads. The experimental results show that the ionic liquid flexible pressure sensor array can accurately identify the load position and load weight, and has good responsiveness to multi-touch.

[0168] The 4×3 gelled ionic liquid electronic skin array has excellent multi-point simultaneous static load detection capabilities and can be used for the recognition of graphic shape contours. The present invention uses a 3D printer to prepare three letter models in the shape of "H", "I" and "T". The letter models are placed on the surface of the gelled ionic liquid electronic skin and the resistance change of each unit is recorded with a multimeter. The data is organized as follows Figure 24 As shown in d)-f), after the resistance response is visualized using a three-dimensional bar graph, the resistance response bar graph is consistent with the shape of the letter model prepared by the present invention.

[0169] (3) Study on the dynamic load detection performance of gelled ionic liquid electronic skin 4×3 array

[0170] The present invention first tests the response ability of the gelled ionic liquid electronic skin array to the sliding speed. A weight with a mass of 20g is slid on the surface of the electronic skin. The sliding diagram is shown in FIG. Figure 25 As shown in a). As mentioned above, the radius of a single circular unit is 1.5 cm, and the distance between two adjacent units is d = 1.4 cm. Therefore, the distance between the center points of two adjacent units is d = 4.4 cm. In the experiment, the present invention pulled the weight to give it different initial velocities, and finally obtained the following Figure 25 In the resistance response curve shown in a), when the weight slides across the skin cell, it applies a certain pressure load, resulting in a peak in the resistance curve. The present invention records the time of the peak and calculates the average time interval between adjacent resistance peaks, thus obtaining an average speed of 4.4 cm / s. In experiments, the present invention successfully detected a sliding speed of 4.4 cm / s. Therefore, the flexible electronic sensor array of the present invention can accurately detect sliding speed.

[0171] In addition to speed information, the present invention can also calculate the actual external pressure at different sliding speeds by changing the average resistance value. When recording the different speeds of the metal ball, four changing resistance values ​​R1, R2, R3 and R4 can be obtained on the four electronic skin units. After averaging the resistances, the average resistance change is obtained. Substituting the resistance R into y = 0.05p, the actual external pressure load corresponding to different rolling speeds can be obtained. The results are as follows: Figure 25 As shown in b). Figure 25 The results in b) show that when the speed is in the range of 1 to 8 cm / s, the greater the sliding speed, the smaller the deformation of the electronic skin unit, the smaller the change in the average resistance value of the electronic skin unit, and the smaller the actual external pressure load calculated.

[0172] For a 4×3 gelled ionic liquid electronic skin array, the present invention studies its single-point sliding trajectory recognition capability. A 100g weight is dragged across the array surface along a fixed trajectory, and the "SOS" array is plotted to obtain a 3D histogram response of a single-point sliding, as shown in the following figure. Figure 26 As shown in Figure 2 , the corresponding electronic skin units sequentially generate response resistance during the sliding process, and the response results clearly reflect the pre-set "SOS" sliding trajectory of the present invention. Furthermore, the response results can also be used to assess the magnitude of external loads during the sliding process. Therefore, the gelled ionic liquid electronic skin of the present invention has excellent responsiveness to single-point sliding.

[0173] The present invention previously studied the ability of gelled ionic liquid electronic skin to detect single-point dynamic loads, including sliding speed detection and sliding trajectory detection. Based on this, the present invention further studies multi-point simultaneous sliding detection. Three fingers are used to apply dynamic pressure loads to the electronic skin array. The sliding experiment can obtain the resistance change value of the finger on different sensor units, and after conversion, the following is obtained: Figure 27 The experimental results are shown.

[0174] from Figure 27It can be seen from the present invention that the fingers respond in units 1, 4, 7, 10, 2, 5, 8, 11, 3, 6, 9, and 12 respectively. According to the response results, it can be found that during the sliding process, the middle electronic skin unit is subjected to a larger pressure, while the pressure of the units on both sides is relatively small. Therefore, the gelled ionic liquid electronic skin unit can respond accurately when three fingers slide. According to the same method, the present invention also studied the detection ability of applying dynamic loads to four points of the side unit at the same time. A dynamic pressure load sliding experiment was applied to the electronic skin array with four fingers to obtain the resistance change value on different sensing units and converted by P=F / A to obtain the following Figure 28 The experimental results shown. Figure 28 It can be seen from the present invention that the fingers respond in units 1, 2, 3, and 4, units 5, 6, 7, and 8, and units 9, 10, 11, and 12 respectively. Figure 28 As shown, the gelled ionic liquid electronic skin unit can also respond accurately when four fingers slide. This further proves that the ionic liquid flexible electronic sensor array of the present invention has good response capability to simultaneous sliding of multiple points at low temperatures and can achieve accurate detection of multi-point sliding.

[0175] The present invention combines gelled ionic liquid electronic skin units into a 4×3 electronic skin array and studies its static load and dynamic load detection capabilities, solving the problem of small electronic skin unit area and small number of signals. This section of the present invention splits large-size electronic skin units into more flexible small-size electronic skin arrays, and combines the performance advantages of gelled electronic skin, such as sensitive detection in extremely low temperature environments and minimal damage affected by vacuum environments, to successfully apply it to aerospace gloves and realize sign language gesture recognition.

[0176] (4) Research on the application of finger bending recognition in gelled ionic liquid electronic skin aerospace gloves

[0177] The present invention firstly produced a three-array gelled ionic liquid electronic skin, which was tightly attached to the surface of the index finger of the glove and a -50°C ultra-low temperature environment was created using an ultra-low temperature refrigerator. The finger with the three-array electronic skin was bent at 30°, 60°, and 90° respectively, and the resistance response curves of the three units were recorded using a multimeter. The experimental test results are shown as follows: Figure 29 shown.

[0178] from Figure 29As can be seen in the figure, when the finger is bent at 30°, 60°, and 90°, the originally flat resistance curve shows a spike response, and the resistance change increases with the degree of bending. Furthermore, the electronic skin units at different locations show different resistance increases at the same bending angle. Unit 2 has the largest resistance increase, while units 1 and 3 have similar resistance increases. This is because when the finger is bent, it squeezes the gelled ionic liquid electronic skin, causing the internal flexible circuit channel to deform, resulting in an increase in the resistance curve. The greater the finger bending angle, the greater the channel deformation and the higher the resistance increase. When the finger bending angle is the same, the channel deformation of electronic skin units at different knuckles is also different, resulting in different resistance increases between electronic skin units.

[0179] From the experimental results, the present invention can know that the three-array electronic skin can sensitively detect finger bending gestures, and can accurately judge the degree of finger bending and the specific bending position by the size of the increase in the resistance of the electronic skin units at different positions, showing its broad application potential in gesture recognition.

[0180] (5) Research on the application of sign language gesture recognition in gelled ionic liquid electronic skin aerospace gloves

[0181] In this paper, the present invention successfully realizes the recognition application of three-array gelled ionic liquid electronic skin for finger bending gestures. On this basis, the present invention studies and realizes the gesture recognition application of aerospace gloves. Sign language is used as an alternative communication method for people with speech disorders. Its gestures are characterized by high complexity and high flexibility, and gesture recognition is difficult. The present invention uses the template removal method to prepare two three-array electronic skins and three two-array electronic skins. The three-array electronic skin is tightly fitted to the surface of the index finger (Index) and middle finger (Middle) gloves, and the two-array electronic skin is tightly fitted to the thumb (Thumb), ring finger (Ring), and little finger (Little), to prepare the glove model as shown in the figure. Figure 30 As shown in a), a simple sign language gesture of the number "1" is performed using a glove. The present invention selects T1 and M1 from 12 units as an example of the resistance response curve, as shown in FIG. Figure 30 b) and Figure 30 c) in the above example.

[0182] The present invention first studies the recognition ability of the gelled ionic liquid electronic skin glove model for single semantic gestures. Numbers are the most commonly used single semantic gestures in daily life. The present invention uses an ultra-low temperature refrigerator to create an ultra-low temperature environment of -50 degrees Celsius to simulate the cold environment of space. Then, the corresponding gestures of "1, 2, 3, 4, 5, 6, 7, 8, 9" are made in the refrigerator and held for 1 second. After that, the five fingers are restored to their natural state. A multimeter is used to record and obtain the resistance change curve of 12 skin units of the five fingers. The present invention organizes it to obtain Figure 31 .

[0183] from Figure 31 In the present invention, it can be seen that the resistance curve of the gelled ionic liquid electronic skin unit is stable without obvious fluctuations when the finger is naturally stretched. When the finger is bent, the corresponding skin unit produces deformation of the circuit channel, resulting in an increase in resistance. Taking the number "6" gesture as an example, when maintaining it, the thumb and little finger need to be bent during the gesture. The T1, T2, L1, and L2 electronic skin units produce a certain resistance change corresponding to the finger bending action, which is maintained for a period of time. After the finger is released, the channel deformation disappears, and the resistance value drops rapidly and returns to the initial value. Overall, the resistance curve is basically stable. The curve fluctuates slightly during the bending process of some fingers. This may be caused by the small movements of the human finger itself during the gesture. Overall, this does not affect the resistance change curve, and it indirectly illustrates that the gelled ionic liquid electronic skin has high sensitivity.

[0184] After completing the recognition experiment of single gesture semantics, the present invention studied the recognition performance of the gelled ionic liquid electronic skin glove model in complex continuous sentence gestures. The present invention selected several commonly used sign sentences in life, namely "How are you?", "I'm fine", "Nice to meet you", and "I need help", and used the glove model to perform sign language demonstration in an ultra-low temperature refrigerator. The movements are shown in the schematic diagram. A multimeter was used to detect the resistance curve of the 12 electronic skin units on the five fingers, and the data was sorted to obtain Figure 32 .

[0185] The electronic skin, even in low-temperature environments, successfully recognized complex, continuous motions in sign language sentences. For example, the sign language sentence "I need help" consists of four decomposed movements, and the 12 electronic skin units across five fingers responded well to these movements. When the corresponding position of the unit remained unchanged, the resistance curve remained stable. When the corresponding position changed from its initial state to a bent state, the resistance rapidly increased, and when the bent state returned to its initial state, the resistance decreased from a high value, resulting in a downward curve. For example, electronic skin unit L2, located in the middle of the index finger, exhibited a relatively complex motion. During movement one, the middle of the index finger was initially straight, and the L2 resistance curve remained stable. During movement two, the middle of the index finger transitioned from its initial straight state to a bent state, and the L2 resistance curve showed an increase in resistance. Movement three, as the four fingers clenched, the angle of the middle index finger's bend increased, causing the L2 resistance curve to rise further. In movement four, as the middle of the index finger stretched, the resistance decreased back to its initial state.

[0186] In Example 3, the present invention flexibly combines gelled ionic liquid electronic skin units and applies them to aerospace gloves, successfully achieving finger bending angle recognition and more difficult sign language semantic action recognition, demonstrating the high flexibility of gelled ionic liquid electronic skin. Unitizing and combining them can provide a broader application space.

[0187] As shown in the above examples, the present invention uses 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid ([BMIM][BF4]) and the crosslinker N,N'-bis(2-hydroxyethyl)oxamide to prepare a new gelled ionic liquid. This liquid is used as a conductive material to develop an electronic skin with high-performance sensing capabilities over a wide temperature range. The present invention studies its sensing performance and applications, and integrates and arrays the electronic skin units to expand its application scenarios. The research results are as follows:

[0188] (1) The crosslinker N,N'-bis(2-hydroxyethyl)oxalamide can form a physically crosslinked gel in the ionic liquid ([BMIM][BF4]). The minimum concentration of the crosslinker is 3 wt% and the heating temperature is 150°C.

[0189] (2) After gelation, the dynamic viscosity of the ionic liquid increases from 10 1 to 10 5 This increase of four orders of magnitude reduces the risk of leakage. It also exhibits shear-thinning properties, with a dynamic viscosity of less than 300 mPa·s at a shear rate greater than 70 / s, making it injectable. The resistance drift time decreases by up to three orders of magnitude, from 111s to 0.28s. The resistance drift rate also decreases by up to one order of magnitude, from 0.115 to 0.001. This makes the resistance more stable and more suitable for the preparation of electronic skin.

[0190] (3) The gelled ionic liquid electronic skin has the highest detection sensitivity when the inner diameter of the circuit channel is 0.1 cm, the thickness of the upper packaging layer is 0.15 cm, the circuit pattern area accounts for 29.3%, and the cross-linking agent concentration is 3wt%. The detection range is 48-32000Pa and the response speed is 0.07s.

[0191] (4) The electronic skin was stretched 1000 times at 50% strain, and the relative resistance change was less than 3%; the curved surface environment sensing performance was basically consistent with that in the flat state, and it was stable; it could respond to low-frequency deformations of different waveforms in the range of 0.5Hz-4Hz at low temperatures; it had a damage redundancy detection capability of 4800Pa; finally, the electronic skin was applied to the information transmission of Morse code.

[0192] (5) The gelled ionic liquid electronic skin as a sensing unit can be flexibly integrated into an array according to functional requirements, with a minimum array pitch of 1.4 cm. Using this sensing unit, a large-scale 4×3 array of electronic skin was prepared, which has excellent ultra-low temperature (-50°C) static and dynamic load detection capabilities.

[0193] (6) Three-array and two-array electronic skins were prepared, and finger angle recognition was achieved in ultra-low temperature (-50°C) environments. They were applied to aerospace glove models and achieved accurate recognition of simple and continuous complex sign language gestures. They can be applied to human motion recognition in special environments such as space.

[0194] The present invention uses gelled ionic liquid to prepare high-performance electronic skin and applies it to realize human motion recognition in ultra-low temperature environment, which is expected to provide assistance for the development of new conductive materials and the expansion of electronic skin application scenarios.

[0195] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A gelled ionic liquid electronic skin, characterized in that: The flexible upper packaging layer and the flexible lower packaging layer are stacked, wherein the inner surface of the flexible upper packaging layer is provided with a plurality of circuit channel units, the circuit channel units are formed by circuit channels, and the flexible lower packaging layer encapsulates the circuit channels; The thickness of the flexible upper encapsulation layer is 0.15 cm, the cross-section of the circuit channel is square, the side length of the cross-section of the circuit channel is 0.1 cm, the circuit channels forming the circuit channel units form a circular spiral pattern, the radius of the circular spiral pattern is 1.5 cm; the area percentage of the circuit channels in the circular spiral pattern is 29.3%, the number of the circuit channel units is ≥ 2, and the circuit channel units are arranged in an array, with a spacing between two adjacent circuit channel units ≥ 1.4 cm; The gelled ionic liquid electronic skin also includes a conductive material filled in the circuit channel, and the conductive material is a gelled ionic liquid. The preparation method of the gelled ionic liquid includes the following steps: 1-butyl-3-methylimidazolium tetrafluoroborate and N,N'-bis(2-hydroxyethyl)oxamide are mixed and gelled to obtain a gelled ionic liquid, the mass of the N,N'-bis(2-hydroxyethyl)oxamide accounts for 3wt% of the mass of the 1-butyl-3-methylimidazolium tetrafluoroborate, the gelling temperature is 150°C, and the insulation time is 30 minutes.

2. The gelled ionic liquid electronic skin according to claim 1, characterized in that: The material of the flexible upper packaging layer is platinum-catalyzed silica gel.

3. The method for preparing the gelled ionic liquid electronic skin according to claim 1 or 2, characterized in that: The following steps are involved: The upper packaging layer template and the lower packaging layer template are obtained by 3D printing; Using a template method, the upper packaging layer template and the lower packaging layer template are used to prepare a flexible upper packaging layer and a flexible lower packaging layer in an uncured state respectively; Laying the flexible upper packaging layer and the flexible lower packaging layer in an uncured state on top of each other and bonding them to obtain a semi-finished product; Conductive material is injected into the circuit channel of the semi-finished product to obtain the gelled ionic liquid electronic skin.

4. Application of the gelled ionic liquid electronic skin according to claim 1 or 2, or the gelled ionic liquid electronic skin prepared by the preparation method according to claim 3, in wearable sensors for human-computer interaction, motion recognition, or non-therapeutic and non-diagnostic purposes.

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