Anisotropic electronic skin and a method of manufacturing the same

Abstract

The application provides an anisotropic electronic skin and a preparation method thereof. The preparation method provided by the application comprises the following steps: first, preparing a modified polydimethylsiloxane film; then, using a mask plate to prepare a silver nanowire network with a coexisting structure of folds and cracks by a spraying method; then, preparing an anisotropic resistance response film by permeating a thermoplastic polyurethane gel into the silver nanowire network; and finally, coating a TPU gel on the surface of the anisotropic resistance response film, and waiting for the TPU to solidify into a transparent elastic film to realize seamless combination with the anisotropic resistance response film, so as to obtain an anisotropic electronic skin with excellent anti-interference capability. The anisotropic electronic skin prepared by the application has excellent anisotropic sensing performance and excellent anti-interference capability.

Description

Technical Field

[0001] This invention relates to the field of functional device fabrication, and in particular to an anisotropic electronic skin and its fabrication method. Background Technology

[0002] With the rapid development of wearable electronics, electronic skin has been widely used in health monitoring, biomedical engineering, virtual reality (VR), human-computer interaction, and various other applications. Typically, most electronic skins can respond to various external stimuli, including strain, pressure, bending, temperature, and humidity. Among these developments, anisotropic strain electronic skin has attracted significant attention due to its selective response to strain from different directions, simplifying the wiring and integration required for omnidirectional detection. The German journal *Advanced Materials* (2018, Vol. 39) reported an anisotropic strain electronic skin fabricated using nanofiber / polydimethylsiloxane composite materials. The ordered arrangement of the nanofibers endows it with excellent properties such as significant anisotropy, high sensitivity, and rapid response. The British journal *Nature Communications* (2022, Vol. 13) reported an anisotropic strain electronic skin fabricated using tellurium nanowires, exhibiting good strain response performance.

[0003] However, most reports on anisotropic strain electronic skins focus on improving sensitivity and operating range, rarely considering the many difficulties they face in practical applications. In real-world applications, anisotropic electronic skins are typically subjected to various disturbances beyond tensile strain, including different stimuli (pressure, bending, torsion, and temperature) and extreme conditions (low temperature, high temperature, underwater environments). This significantly reduces their accuracy and selectivity in signal sensing, ultimately limiting their service life and application range. Currently, traditional strain electronic skins almost entirely lack the ability to resist other irrelevant stimuli and operate in extreme environments. For example, at temperatures as high as 50°C, the resistance of the materials used in many strain electronic skins is greatly affected by temperature, significantly impacting the accuracy of their signal detection; in underwater environments, most strain electronic skins cannot function properly.

[0004] Therefore, how to avoid the effects of other stimuli and extreme environments on electronic skin and maintain its high sensitivity in various strain response performances is an urgent problem to be solved today. Summary of the Invention

[0005] In view of this, the present invention provides an anisotropic electronic skin and a method for preparing the same. The anisotropic electronic skin provided by the present invention has excellent anisotropic sensing performance and superior anti-interference capability.

[0006] This invention provides a method for preparing anisotropic electronic skin, comprising the following steps:

[0007] A) Preparation of modified polydimethylsiloxane thin films:

[0008] A1) Mix polydimethylsiloxane, curing agent and Triton to obtain a mixture;

[0009] A2) The mixture is coated onto a substrate, cured into a film, and then the cured film is peeled off to obtain a modified polydimethylsiloxane film;

[0010] B) Fabrication of nanowire networks:

[0011] B1) The modified polydimethylsiloxane film is pre-stretched to obtain a pre-stretched film;

[0012] B2) Silver nanowires are sprayed onto the surface of the pre-stretched film using a grating mask, and then the pre-stretched film is released to its original strain state to form a silver nanowire network with wrinkled and cracked structures on the film surface.

[0013] C) Preparation of anisotropic resistive responsive thin films:

[0014] Thermoplastic polyurethane gel is applied to the side of the film with silver nanowire network obtained in step B), then cured to form a cured layer, and then the cured layer is peeled off to obtain an anisotropic resistivity response film.

[0015] D) Fabrication of anisotropic electronic skin:

[0016] The anisotropic resistive response film obtained in step C) is coated with thermoplastic polyurethane gel and then cured to obtain anisotropic electronic skin.

[0017] Preferably, in step A1), the mass ratio of polydimethylsiloxane, curing agent and Triton is (8-12):(0.5-1.5):(0.05-0.15).

[0018] Preferably, in step A2), the curing temperature is 40–80°C and the time is 4–8 hours.

[0019] Preferably, in step B1), the pre-stretch strain is 20% to 140%.

[0020] Preferably, in step B2), the spraying pressure is 100-500 kPa.

[0021] Preferably, in step C), the thermoplastic polyurethane gel is prepared by the following method: mixing thermoplastic polyurethane with a solvent and allowing it to stand to obtain the thermoplastic polyurethane gel.

[0022] Preferably, in step C), the curing temperature is 20–100°C and the time is 1–5 hours.

[0023] Preferably, in step D):

[0024] The coating amount of the thermoplastic polyurethane gel is 0.142–0.236 g / cm³. 2 ;

[0025] The coating method is spin coating;

[0026] The spin coating speed is 600-1200 rpm.

[0027] Preferably, in step D), the curing temperature is 40–80°C and the time is 20–40 min.

[0028] The present invention also provides an anisotropic electronic skin prepared by the preparation method described in the above technical solution.

[0029] The preparation method provided by this invention involves first preparing a modified polydimethylsiloxane film, then using a mask to prepare a silver nanowire network with a structure exhibiting both wrinkles and cracks through a spraying method. Next, thermoplastic polyurethane gel is infiltrated into the silver nanowire network to prepare an anisotropic resistive response film. Finally, TPU gel is coated onto the surface of the anisotropic resistive response film, and after the TPU cures into a transparent elastic film, it achieves seamless bonding with the anisotropic resistive response film (i.e., the anisotropic resistive response film and the transparent elastic film are seamlessly bonded together), resulting in an anisotropic electronic skin with excellent anti-interference capabilities. Compared with existing technologies, this invention provides a simpler and lower-cost preparation method, and the resulting anisotropic electronic skin exhibits excellent anti-interference capabilities, demonstrating superior anti-interference performance under high pressure, torsion, bending, temperature changes, and extreme conditions (such as impact, flooding, and extreme temperatures). Experimental results show that, due to its unique structure with both wrinkles and cracks, the electronic skin exhibits strain sensitivities of 2825 and 0.69 in two perpendicular directions, a difference exceeding 4000 times. Its response and recovery times are 7.5 ms, and its performance remains stable after 3000 cycles. Furthermore, the introduction of a transparent elastic film demonstrates excellent anti-interference capabilities; its resistance changes by less than 6% when subjected to high voltage (663 kPa), torsion (540°), or bending (180°). Even exposure to harsh environments (hot, cold, and underwater) has negligible impact on its performance, indicating broad application prospects. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0031] Figure 1 This is an optical image of the grating mask used in the fabrication process of this invention;

[0032] Figure 2 This is a SEM image of the Ag NWs network formed on the M-PDMS film in step B) of Example 1;

[0033] Figure 3 The image shows the surface SEM image of the TPU-coated Ag NWs network obtained in step C) of Example 1.

[0034] Figure 4 The image shows a cross-sectional SEM image of the TPU-coated Ag NWs network obtained in step C) of Example 1.

[0035] Figure 5 An optical image of the electronic skin obtained in Example 1;

[0036] Figure 6 An optical image of the electronic skin obtained in Example 1 adhering to the skin;

[0037] Figure 7 The graph shows the relationship between the resistance of the electronic skin obtained in Example 1 and strain in the "0" and "90" directions.

[0038] Figure 8 The graph shows the resistance response of the electronic skin obtained in Example 1 in the "0" and "90" directions under different strains.

[0039] Figure 9 The graph shows the resistance response of the electronic skin obtained in Example 1 under temperature cycling from -40°C to 60°C.

[0040] Figure 10 The graph shows the resistance response of the electronic skin obtained in Example 1 under different torsion angles (left) and pressures (right).

[0041] Figure 11 The graph shows the resistance response of the electronic skin obtained in Example 1 at different bending angles. Detailed Implementation

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0043] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0044] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0045] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0046] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it means that the units for the left and right endpoints are the same. For example, 40~80℃ means that the units for the left endpoint "40" and the right endpoint "80" are both in degrees Celsius.

[0047] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0048] This invention provides a method for preparing anisotropic electronic skin, comprising the following steps:

[0049] A) Preparation of modified polydimethylsiloxane thin films:

[0050] A1) Mix polydimethylsiloxane, curing agent and Triton to obtain a mixture;

[0051] A2) The mixture is coated onto a substrate, cured into a film, and then the cured film is peeled off to obtain a modified polydimethylsiloxane film;

[0052] B) Fabrication of nanowire networks:

[0053] B1) The modified polydimethylsiloxane film is pre-stretched to obtain a pre-stretched film;

[0054] B2) Silver nanowires are sprayed onto the surface of the pre-stretched film using a grating mask, and then the pre-stretched film is released to its original strain state to form a silver nanowire network with wrinkled and cracked structures on the film surface.

[0055] C) Preparation of anisotropic resistive responsive thin films:

[0056] Thermoplastic polyurethane gel is applied to the side of the film with silver nanowire network obtained in step B), then cured to form a cured layer, and then the cured layer is peeled off to obtain an anisotropic resistivity response film.

[0057] D) Fabrication of anisotropic electronic skin:

[0058] The anisotropic resistive response film obtained in step C) is coated with thermoplastic polyurethane gel and then cured to obtain anisotropic electronic skin.

[0059] The anisotropic electronic skin prepared by this invention possesses a unique structure: a metal nanowire-polymer anisotropic resistive response film with both wrinkles and cracks. It also exhibits high transparency and demonstrates excellent anisotropic sensing performance. Furthermore, the transparent elastic film protects the structure, enabling the electronic skin to exhibit outstanding anti-interference capabilities under high pressure, torsion, bending, temperature changes, and extreme conditions (such as impact, flooding, and extreme temperatures). This significantly improves signal fidelity, broadens the operating environment, and thus has broad application prospects.

[0060] Regarding step A) Preparation of modified polydimethylsiloxane thin films

[0061] A1) Mix polydimethylsiloxane, curing agent and Triton to obtain a mixture;

[0062] A2) The mixture is coated onto a substrate, cured into a film, and then the cured film is peeled off to obtain a modified polydimethylsiloxane film.

[0063] [Regarding step A1]:

[0064] A1) Mix polydimethylsiloxane, curing agent and Triton to obtain a mixture.

[0065] In this invention, the source of the polydimethylsiloxane (PDMS) is not particularly limited; it can be any commercially available product.

[0066] In this invention, the curing agent is preferably at least one of Sylgard 184 (Dow Corning), vinyltriamine, and diethylaminopropylamine; in some embodiments of this invention, the curing agent is Sylgard 184 (Dow Corning).

[0067] In this invention, the Triton is not subject to any special restrictions on its source; it can be any commercially available product.

[0068] In this invention, the preferred mass ratio of polydimethylsiloxane, curing agent and Triton is (8-12):(0.5-1.5):(0.05-0.15), more preferably (9-11):(0.75-1.25):(0.075-0.125), and most preferably 10:1:0.1.

[0069] In this invention, there are no particular restrictions on the method of mixing polydimethylsiloxane, curing agent, and Triton, as long as the materials are mixed evenly, such as by stirring. After mixing, a mixture is obtained.

[0070] [Regarding step A2]:

[0071] A2) The mixture is coated onto a substrate, cured into a film, and then the cured film is peeled off to obtain a modified polydimethylsiloxane film.

[0072] In this invention, the type of substrate is not particularly limited; any conventional substrate for coating is acceptable. After coating the mixture obtained in step A1) onto the substrate, the mixture is cured to form a film. The curing temperature is preferably 40–80°C, specifically 40°C, 50°C, 60°C, 70°C, or 80°C. The curing time is preferably 4–8 hours, specifically 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours. After curing, the cured film is peeled off to obtain a modified polydimethylsiloxane film. The thickness of the obtained modified polydimethylsiloxane film is preferably 0.5–0.8 mm.

[0073] Regarding step B) Fabrication of nanowire networks

[0074] B1) The modified polydimethylsiloxane film is pre-stretched to obtain a pre-stretched film;

[0075] B2) Silver nanowires are sprayed onto the surface of the pre-stretched film using a grating mask, and then the pre-stretched film is released to its original strain state, forming a silver nanowire network with wrinkled and cracked structures on the film surface.

[0076] [Regarding step B1]:

[0077] B1) The modified polydimethylsiloxane film is pre-stretched to obtain a pre-stretched film.

[0078] In this invention, after obtaining the modified polydimethylsiloxane film in step A), the modified polydimethylsiloxane film is first subjected to a pre-stretching treatment. In this invention, the pre-stretching strain is preferably 20%–140%, more preferably 40%–120%, further preferably 60%–100%, and most preferably 82%. After the above pre-stretching treatment, a pre-stretched film is obtained.

[0079] [Regarding step B2]:

[0080] B2) Silver nanowires are sprayed onto the surface of the pre-stretched film using a grating mask, and then the pre-stretched film is released to its original strain state, forming a silver nanowire network with wrinkled and cracked structures on the film surface.

[0081] In this invention, the grating mask can be fabricated using laser cutting technology, and its optical image is as follows: Figure 1 As shown. In this invention, the preferred shape and size specifications of the grating mask are as follows: the grating mask is a rectangle with a fixed gap and period, arranged horizontally; the gap is preferably 150-200μm, more preferably 160-180μm, and most preferably 170μm; the period is preferably 250-350μm, more preferably 280-320μm, and most preferably 300μm.

[0082] This invention utilizes a grating mask to spray silver nanowires onto the surface of the pre-stretched film obtained in step B1). Specifically, a grating mask is laid on the surface of the pre-stretched film obtained in step B1), and then silver nanowires are sprayed onto the surface of the pre-stretched film through the grating mask, thereby forming silver nanowires with a certain structural morphology on the surface of the pre-stretched film. In this invention, the silver nanowire raw material can be loaded into a spray gun for spraying. The spraying pressure (spray gun pressure) is preferably 100-500 kPa, more preferably 200-400 kPa, further preferably 250-350 kPa, and most preferably 300 kPa.

[0083] In this invention, after the above-mentioned spraying, the grating mask is removed, and the pre-stretched film is slowly released to its original strain state (i.e., the pre-stretch strain is restored to 0%). Due to the Poisson's ratio of the modified polydimethylsiloxane film obtained in step A) and the release of the pre-stretch strain, the structure of the sprayed silver nanowires (Ag NWs) is affected, causing the formation of wrinkles and cracks (i.e., the silver nanowires (Ag NWs) are arranged to achieve multi-scale stress modulation), thereby forming a silver nanowire network with wrinkled and cracked structures on the film surface, thus obtaining a composite of film-silver nanowire network layer. In this invention, the thickness of the silver nanowire network is preferably 0.5–2.5 μm, more preferably 1–2 μm, and most preferably 1.5 μm.

[0084] Regarding step C) Preparation of anisotropic resistive responsive thin films

[0085] Thermoplastic polyurethane gel is applied to the side of the film with the silver nanowire network obtained in step B), then cured to form a cured layer, and then the cured layer is peeled off to obtain an anisotropic resistivity response film.

[0086] In this invention, the thermoplastic polyurethane gel is preferably prepared by the following method: thermoplastic polyurethane (TPU) is stirred and mixed with a solvent, and then allowed to stand to obtain the thermoplastic polyurethane gel. The solvent is preferably at least one selected from DMF, dimethyl sulfoxide, acetone, butanone, and toluene, more preferably DMF. In this invention, the ratio of the thermoplastic polyurethane gel to the solvent is preferably (2-8) g:(5-20) mL, more preferably (3-7) g:(7-15) mL, further preferably (4-6) g:(9-12) mL, and most preferably 4.8 g:10 mL. In this invention, the stirring speed is preferably 500-1000 rpm, specifically 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, and 1000 rpm. The stirring time is preferably 1-3 hours, specifically 1 hour, 2 hours, and 3 hours. After the above stirring and mixing, the TPU is completely dissolved, and then allowed to stand for a period of time. The settling time is preferably 20-28 hours, more preferably 21-27 hours, further preferably 22-26 hours, and most preferably 24 hours. After the above treatment, a thermoplastic polyurethane gel is obtained.

[0087] In this invention, thermoplastic polyurethane gel is applied to the film obtained in step B), specifically to the surface of the film having the silver nanowire network. The preferred method of application is dropwise addition. The preferred amount of thermoplastic polyurethane gel applied is 0.05–0.08 g / cm³. 2 More preferably, it is 0.067 g / cm³. 2 After the thermoplastic polyurethane gel is applied, it penetrates into the silver nanowire network by capillary force and then cures to form a cured layer. The curing temperature is preferably 20-100℃, more preferably 40-80℃, and most preferably 60℃. The curing time is preferably 1-5 hours, more preferably 3 hours. After curing, a cured TPU layer containing an Ag NWs network is formed. This cured layer is then peeled off. Because the bonding force between Ag NWs and TPU is stronger, the cured TPU layer containing the Ag NWs network can be easily peeled off from the modified polydimethylsiloxane film, thereby obtaining an anisotropic resistivity responsive film.

[0088] Regarding step D) Fabrication of anisotropic electronic skin

[0089] The anisotropic resistive response film obtained in step C) is coated with thermoplastic polyurethane gel and then cured to obtain anisotropic electronic skin.

[0090] In this invention, the preparation method of the thermoplastic polyurethane gel is the same as that described in the previous technical solution, and will not be repeated here.

[0091] In this invention, the coating method is preferably spin coating. The coating amount of the thermoplastic polyurethane gel is preferably 0.142–0.236 g / cm³. 2 The spin coating speed is preferably 600-1200 rpm, more preferably 900-1100 rpm, and most preferably 1000 rpm.

[0092] In this invention, after the above coating, curing is performed. The curing temperature is preferably 20-100℃, more preferably 40-80℃, and most preferably 60℃. The curing time is preferably 10-50 min, more preferably 20-40 min, and most preferably 30 min. In step C), after peeling off the cured TPU layer containing the Ag NWs network, a layer of TPU gel is coated on its surface and cured as an encapsulation layer to protect the internal structure, thereby obtaining anisotropic electronic skin.

[0093] This invention also provides an anisotropic electronic skin prepared by the method described in the above-mentioned technical solution. The anisotropic electronic skin obtained by this invention comprises: an anisotropic resistive response film with a wrinkled and cracked structure and a transparent elastic film. By introducing a silver nanowire-thermoplastic polyurethane film with a wrinkled and cracked structure, this invention successfully solves the problem of insignificant anisotropy in traditional strain-sensitive electronic skins, resulting in greater differences in strain sensitivity in different directions. Simultaneously, due to the encapsulation of the transparent elastic film, the electronic skin exhibits excellent anti-interference capabilities under high pressure, torsion, bending, temperature changes, and extreme conditions (such as impact, flooding, and extreme temperatures), which greatly improves signal fidelity, broadens the operating environment, and therefore has broad application prospects.

[0094] The preparation method provided by this invention involves first preparing a modified polydimethylsiloxane film, then using a mask to prepare a silver nanowire network with a structure exhibiting both wrinkles and cracks through a spraying method. Next, thermoplastic polyurethane gel is infiltrated into the silver nanowire network to prepare an anisotropic resistive response film. Finally, TPU gel is coated onto the surface of the anisotropic resistive response film, and after the TPU cures into a transparent elastic film, it achieves seamless bonding with the anisotropic resistive response film (i.e., the anisotropic resistive response film and the transparent elastic film are seamlessly bonded together), resulting in an anisotropic electronic skin with excellent anti-interference capabilities. Compared with existing technologies, this invention provides a simpler and lower-cost preparation method, and the resulting anisotropic electronic skin exhibits excellent anti-interference capabilities, demonstrating superior anti-interference performance under high pressure, torsion, bending, temperature changes, and extreme conditions (such as impact, flooding, and extreme temperatures). Experimental results show that, due to its unique structure with both wrinkles and cracks, the electronic skin exhibits strain sensitivities of 2825 and 0.69 in two perpendicular directions, a difference exceeding 4000 times. Its response and recovery times are 7.5 ms, and its performance remains stable after 3000 cycles. Furthermore, the introduction of a transparent elastic film demonstrates excellent anti-interference capabilities; its resistance changes by less than 6% when subjected to high voltage (663 kPa), torsion (540°), or bending (180°). Even exposure to harsh environments (hot, cold, and underwater) has negligible impact on its performance, indicating broad application prospects.

[0095] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0096] Example 1

[0097] A) Preparation of modified polydimethylsiloxane thin films:

[0098] A1) Polydimethylsiloxane (PDMS), curing agent Sylgard 184 (Dow Corning), and Triton were mixed evenly at a mass ratio of 10:1:0.1 to obtain a mixture.

[0099] A2) The mixture is coated on a substrate and cured at 60°C for 5 hours to form a film. The cured film is then peeled off to obtain a modified polydimethylsiloxane film (denoted as M-PDMS film).

[0100] B) Fabrication of nanowire networks:

[0101] B1) Apply a pre-stretch of 82% strain to the M-PDMS film obtained in step A) to obtain a pre-stretched film.

[0102] B2) Place a grating mask on the surface of the pre-stretched film, and then spray AgNWs (purchased from XF Nano) with a spray gun at a pressure of 300 kPa. Then, remove the grating mask and slowly release the pre-stretched film to its original strain state (i.e., restore the pre-stretched strain to 0%), causing the formation of wrinkles and crack structures, thereby forming an AgNWs network with wrinkled and cracked structures (1.5 μm thick) on the film surface.

[0103] See Figure 2 , Figure 2 This is a SEM image of the Ag NWs network formed on the M-PDMS film in step B) of Example 1. It can be seen that an Ag NWs network with wrinkled and cracked structures was formed on the film.

[0104] C) Preparation of anisotropic resistive responsive thin films:

[0105] Weigh 4.8g of TPU (Bayer, Desmopan, DP9370A), dissolve it completely in 10mL of DMF solvent with stirring, and let it stand for 24h to obtain TPU gel.

[0106] Take 1.42g of TPU gel and drop it onto the surface of the film obtained in step B) that has the Ag NWs network (dropping amount is 0.067g / cm). 2 The TPU gel penetrates into the Ag NWs network through capillary action. Then, it is cured at 60°C for 3 hours to form a cured TPU layer containing the Ag NWs network (i.e., TPU coated with Ag NWs network). The cured layer is then peeled off to obtain an anisotropic resistivity response film.

[0107] See Figure 3-4 ,in, Figure 3 This is a surface SEM image of the TPU-coated Ag NWs network obtained in step C) of Example 1. Figure 4 The image shown is a cross-sectional SEM image of the TPU-coated Ag NWs network obtained in step C) of Example 1. It can be seen that the Ag NWs network is encapsulated within the TPU layer.

[0108] D) Fabrication of anisotropic electronic skin:

[0109] TPU gel was spin-coated onto the surface of the anisotropic resistivity-responsive film obtained in step C) at a spin speed of 1000 rpm and a coating amount of 0.150 g / cm³. 2 An anisotropic resistive response film was encapsulated and then cured at 60°C for 30 min to obtain anisotropic electronic skin.

[0110] See Figure 5 , Figure 5An optical image of the electronic skin obtained in Example 1;

[0111] See Figure 6 , Figure 6 This is an optical image of the electronic skin obtained in Example 1 adhering to the skin.

[0112] Product performance testing :

[0113] 1. Strain sensitivity test:

[0114] The testing process is as follows: Different strains were applied to the electronic skin using an Instron 5565A tensile testing machine, and the changes in its resistance response in the "0" and "90" directions within the strain range of 0 to 20% were tested.

[0115] See test results Figure 7 , Figure 7 The graph shows the relationship between the resistance of the electronic skin obtained in Example 1 and strain in the "0" and "90" directions. It can be seen that the strain sensitivity of the electronic skin in the two vertical directions is 2825 and 0.69, respectively, with a difference of more than 4000 times, indicating excellent strain sensitivity and anisotropy.

[0116] 2. Stability Test:

[0117] The testing process is as follows: Different strains were applied to the electronic skin using an Instron 5565A tensile testing machine, and the changes in its resistance response in the "0" and "90" directions were tested at strains of 1%, 3%, 5%, and 7%.

[0118] See test results Figure 8 , Figure 8 This shows the resistance response changes of the electronic skin in Example 1 of the present invention in the "0" and "90" directions under different strains. It can be seen that the electronic skin has good stability.

[0119] 3. Anti-interference capability test:

[0120] The testing process is as follows: Under different interference conditions, such as extreme temperature, high pressure, torsion, and bending, the resistance response of the electronic skin was tested.

[0121] See test results Figure 9 , Figure 9 The graph shows the resistance response of the electronic skin obtained in Example 1 under temperature cycling from -40°C to 60°C. It can be seen that the performance of the electronic skin did not decrease after being repeatedly heated and frozen 10 times between -40°C and 60°C.

[0122] See test results Figure 10-11 . Figure 10The graph shows the resistance response of the electronic skin obtained in Example 1 under different torsion angles (left) and pressures (right). Figure 11 The graph shows the resistance response of the electronic skin obtained in Example 1 under different bending angles. It can be seen that when subjected to high voltage (663 kPa), torsion (540°), or bending (180°), its resistance change is less than 6%, demonstrating excellent anti-interference ability.

[0123] This invention provides an anisotropic electronic skin with excellent anti-interference ability and its preparation method. This method is economical and simple, providing a foundation for subsequent large-scale industrial production. The preparation process provided by this invention is simple and can obtain large-scale ordered high-performance anisotropic electronic skin.

[0124] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing anisotropic electronic skin, characterized in that, Includes the following steps: A) Preparation of modified polydimethylsiloxane thin films: A1) Mix polydimethylsiloxane, curing agent and Triton to obtain a mixture; A2) The mixture is coated onto a substrate, cured into a film, and then the cured film is peeled off to obtain a modified polydimethylsiloxane film; B) Fabrication of nanowire networks: B1) The modified polydimethylsiloxane film is pre-stretched to obtain a pre-stretched film; B2) Silver nanowires are sprayed onto the surface of the pre-stretched film using a grating mask, and then the pre-stretched film is released to its original strain state to form a silver nanowire network with wrinkled and cracked structures on the film surface. C) Preparation of anisotropic resistive responsive thin films: Thermoplastic polyurethane gel is applied to the side of the film with silver nanowire network obtained in step B), then cured to form a cured layer, and then the cured layer is peeled off to obtain an anisotropic resistivity response film. D) Fabrication of anisotropic electronic skin: The anisotropic resistive response film obtained in step C) is coated with thermoplastic polyurethane gel and then cured to obtain anisotropic electronic skin.

2. The preparation method according to claim 1, characterized in that, In step A1), the mass ratio of polydimethylsiloxane, curing agent and Triton is (8-12):(0.5-1.5):(0.05-0.15).

3. The preparation method according to claim 1, characterized in that, In step A2), the curing temperature is 40–80°C and the time is 4–8 hours.

4. The preparation method according to claim 1, characterized in that, In step B1), the strain of the pre-stretch is 20% to 140%.

5. The preparation method according to claim 1, characterized in that, In step B2), the spraying pressure is 100-500 kPa.

6. The preparation method according to claim 1, characterized in that, In step C), the thermoplastic polyurethane gel is prepared by the following method: thermoplastic polyurethane is stirred and mixed with a solvent, and then allowed to stand to obtain thermoplastic polyurethane gel.

7. The preparation method according to claim 1, characterized in that, In step C), the curing temperature is 20–100°C and the time is 1–5 hours.

8. The preparation method according to claim 1, characterized in that, In step D): The coating amount of the thermoplastic polyurethane gel is 0.142–0.236 g / cm³. 2 ; The coating method is spin coating; The spin coating speed is 600-1200 rpm.

9. The preparation method according to claim 1, characterized in that, In step D), the curing temperature is 40–80°C and the time is 20–40 min.

10. An anisotropic electronic skin prepared by any one of claims 1 to 9.

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