Ultrathin breathable electronic skin as well as preparation method and application thereof

Abstract

The invention relates to ultrathin breathable electronic skin and a preparation method and application thereof.The electronic skin comprises a flexible substrate layer which is a TPU / SF core-shell structure nanofiber membrane prepared through coaxial electrostatic spinning, TPU forms a fiber core layer, and SF forms a fiber shell layer; and the conductive composite layer covers the surface of the flexible substrate layer and is composed of a continuous conductive network formed by compounding PEDOT: PSS and MXene. Compared with the prior art, the invention has the advantages of high dynamic adaptability, long-term air permeability, non-inductive attachment and the like.

Description

Technical Field

[0001] This invention relates to the field of electronic skin materials technology, and in particular to an ultra-thin, breathable electronic skin, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid development of wearable medical devices, remote rehabilitation and human-computer interaction technologies, surface electromyography (sEMG), as a non-invasive biosignal that dynamically captures the potential of human muscle activity, has been increasingly widely used in clinical rehabilitation, oral function assessment, speech training, motor control and neural engineering, and is especially valuable in the early diagnosis and functional rehabilitation of masticatory system diseases.

[0003] Most commonly used sEMG acquisition devices rely on silver / silver chloride (Ag / AgCl) wet electrodes, which achieve the conductive interface between the electrode and the skin by coating the surface of the Ag / AgCl electrode with an electrolyte-containing gel. Although the signal quality is good in the short term and the application is relatively mature, there are still the following significant shortcomings in long-term use in high dynamic areas such as the face or jaw: (1) Poor comfort and strong irritation: Ag / AgCl electrodes are usually about 1 to 2 mm thick, which will cause a foreign body sensation when worn, especially when used in sensitive areas such as the face or neck, which can easily cause pressure marks or even skin inflammation. The electrolyte in the gel may penetrate into the stratum corneum after long-term contact, causing adverse reactions such as skin irritation, itching or erythema. (2) High mechanical rigidity and poor anti-interference: Traditional wet electrode materials have high rigidity and are difficult to adapt to skin deformation. During movement, displacement, slippage, wrinkles and other problems are easy to occur, forming obvious motion artifacts, which are more prominent in violent dynamic processes such as speaking, chewing and facial expression changes. (3) Strong sealing, affecting skin water vapor metabolism: The heavy electrodes and sealed structure restrict normal skin respiration. The accumulated heat and sweat not only cause discomfort and eczema risk, but also affect the stability of electrode performance.

[0004] To improve biocompatibility, some current research has shifted towards natural materials. For example, patent publication number CN109183274A discloses an electronic skin substrate composed of a silk fibroin / chitosan blended nanofiber membrane and silicone. While this technology performs well under static conditions, the nanofiber membrane is prone to structural fatigue under drastic deformation (such as chewing or facial expressions), leading to signal drift and insufficient dynamic adaptability. Although the silicone coating improves adhesion, it exacerbates skin permeability issues, potentially inducing eczema with prolonged wear, and presents interface sealing problems. Furthermore, the composite membrane lacks optimized ultrathin properties, failing to eliminate the foreign body sensation on the face, and suffers from insufficient thickness and lightweight design. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art, such as insufficient dynamic adaptability, interface sealing, and insufficient thickness and lightweight, and to provide an ultra-thin breathable electronic skin, its preparation method and application, so as to achieve high dynamic adaptability, long-term breathability and imperceptible adhesion.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide an ultra-thin, breathable electronic skin, comprising:

[0008] The flexible substrate is a thermoplastic polyurethane / silk fibroin (TPU / SF) core-shell structured nanofiber membrane prepared by coaxial electrospinning, wherein polyurethane (TPU) constitutes the fiber core layer and silk fibroin (SF) constitutes the fiber shell layer.

[0009] The conductive composite layer covering the surface of the flexible substrate is composed of a continuous conductive network formed by poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and MXene, referred to as the MP conductive composite layer.

[0010] Furthermore, the mass ratio of TPU to SF in the TPU / SF core-shell structured nanofiber membrane is 2 to 8:1, preferably 2 to 5, and more preferably 4 to 5.

[0011] Furthermore, the specific process of the coaxial electrospinning is as follows: TPU solution and SF solution are electrospinned at different rates through a dual-syringe input system, with TPU as the inner core and SF as the outer shell; the spinning voltage is 14-18kV, preferably 15-17kV, and the collection distance is 15-25cm, preferably 18-22cm. The collection distance refers to the distance from the needle tip to the collecting electrode. The coaxial structure ensures that the fiber has high mechanical compliance, with an elongation of over 250%, adapting to dynamic deformation of facial muscles.

[0012] Furthermore, the concentration of TPU in the TPU solution is 10wt% to 20wt%, preferably 12wt% to 18wt%; the solvent is an organic solvent, including N,N-dimethylformamide (DMF) and tetrahydrofuran (THF).

[0013] Furthermore, the concentration of SF in the SF solution is 10wt% to 20wt%, preferably 10wt% to 14wt%; the solvent is formic acid.

[0014] Furthermore, the SF solution also includes water-soluble polymers for improving spinning performance, including polyethylene oxide (PEO) at a concentration of 0.1 wt% to 0.5 wt%.

[0015] Furthermore, the preparation process of the SF solution is as follows: degummed silk is dissolved in 8-12M lithium bromide (LiBr) solution at 50-70℃ for 1-10h, dialyzed with deionized water for 45-84h (water replacement time points: 1, 4, 8, 24, 36, 48, 60, 72h), centrifuged 1-3 times at 8000-10000rpm×10-30min to remove impurities, and freeze-dried to obtain pure silk fibroin powder; the pure silk fibroin powder is dissolved in 98% formic acid, the SF concentration is 12wt%, and 0.1wt%-0.5wt% of water-soluble polymer is added to improve spinnability to prepare a spinning solution.

[0016] Furthermore, the environmental conditions for coaxial electrospinning are: temperature 22-25℃, relative humidity 30%-50%.

[0017] Furthermore, the electrospinning time in the coaxial electrospinning is 3 to 10 minutes, preferably 4 to 6 minutes.

[0018] Furthermore, the general formula of MXene is M n+ 1X n T x Where: M represents an early transition metal, including titanium (Ti), molybdenum (Mo), vanadium (V), niobium (Nb), tantalum (Ta), and chromium (Cr); X represents carbon (C) or nitrogen (N); T x It is a surface terminating group, such as -OH, -O, -F; n is 1 to 4.

[0019] Furthermore, the mass ratio of PEDOT:PSS to MXene is 1:1 to 20, preferably 1:1 to 10, and even more preferably 1:1 to 5, which can ensure conductivity while avoiding MXene agglomeration.

[0020] Furthermore, the preparation process of the conductive composite layer is as follows: PEDOT:PSS solution is mixed with MXene powder, and after ultrasonic dispersion, a uniform MP conductive composite liquid is obtained. This liquid is then uniformly coated onto the surface of a flexible substrate layer and dried to obtain the MP conductive composite layer.

[0021] Furthermore, the concentration of the PEDOT:PSS solution is 1wt% to 5wt%, and the solvent is water.

[0022] Furthermore, the ultrasonic dispersion power is 30–50 kHz and the time is 10–20 min, which helps to form a stable and uniformly distributed conductive network.

[0023] Furthermore, the coating method is dip coating, the dip coating time is 10-20 minutes, and drying at room temperature can obtain a more uniform layer. After complete drying, it is placed in an oven at 50-70℃ for annealing for 10-60 minutes to prevent PEDOT chain segment breakage or MXene oxidation, thereby improving the stability of the conductive composite layer.

[0024] Furthermore, in the TPU / SF core-shell nanofiber membrane, the mass ratio of PEDOT:PSS in the TPU and MP conductive composite layer is 1:0.1 to 0.5.

[0025] Furthermore, the thickness of the electronic skin is 1–5 μm, and the thickness ratio of the TPU / SF core-shell nanofiber membrane is 1:1–5.

[0026] Furthermore, the water vapor permeability of this electronic skin is ≥300 g·m -2 ·h⁻¹, preferably 350–400 g·m⁻¹ -2 •h-1, meets the skin's need for thermal and moisture balance during prolonged use.

[0027] The second technical solution of the present invention provides a method for preparing ultra-thin, breathable electronic skin, comprising the following steps:

[0028] A flexible substrate layer was obtained by preparing a TPU / SF core-shell structured nanofiber membrane through coaxial electrospinning.

[0029] Preparation of MP conductive composite liquid;

[0030] The MP conductive composite liquid is uniformly coated on the surface of the TPU / SF core-shell structured nanofiber membrane, and after drying, a conductive composite layer is obtained, thus completing the preparation of electronic skin.

[0031] The third technical solution of the present invention is to provide an application of ultra-thin breathable electronic skin in the field of sEMG acquisition technology.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] (1) Traditional electronic skin often uses homogeneous polymer membranes (such as PDMS and PU membranes), which make it difficult to balance mechanical properties and skin adhesion. The electronic skin of this invention uses a TPU / SF core-shell structured nanofiber membrane as a flexible base layer. The fiber layer structure design is achieved through coaxial electrospinning. The TPU core provides excellent tensile strength and tensile strength; the SF shell provides good skin affinity and hydrogen bonding functional groups; the porous structure obtained by coaxial electrospinning significantly improves the membrane's breathability. The electronic skin has higher flexibility and compliance, and can deform with dynamic skin deformation (such as changes in facial expressions), exhibiting high dynamic adaptability; it also significantly improves wearing comfort and long-term breathability, avoiding skin irritation and erythema problems.

[0034] (2) Traditional electronic skin often uses a single conductive material, such as metal nanowires, carbon nanotubes, or PEDOT:PSS, which has shortcomings in conductivity stability, mechanical adhesion, and adaptability to humid and hot environments. This invention uses PEDOT:PSS and MXene to obtain a conductive composite coating, constructs a synergistic conductive network, and forms a stable coating layer through ultrasonic homogenization. PEDOT:PSS and MXene form a stable three-dimensional interconnected network through hydrogen bonding and electrostatic interaction; it can still maintain low interfacial impedance (<20kΩ) and high signal-to-noise ratio electromyography signal acquisition capability under high humidity and high strain conditions.

[0035] (3) Traditional electrodes are generally 1–2 mm thick, which causes a significant “foreign body sensation” and affects natural facial expressions, especially when worn on the face. The electronic skin of this invention has an overall thickness of 1–5 μm, with high structural fit, and is almost integrated with the skin. It can significantly reduce the user’s foreign body sensation, improve the freedom of facial movement, and is suitable for sensitive groups such as children and the elderly. At the same time, it improves the aesthetics of wearing and user acceptance. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the electronic skin bonding skin layer shown in Example 1;

[0037] Figure 2 This is a schematic diagram of the electronic skin shown in Example 1;

[0038] Figure 3 The images shown are scanning electron microscope images (a) and energy dispersive spectroscopy (EDS) diagrams (b) of the electronic skin shown in Example 1.

[0039] Figure 4 Contact angle testing for pure TPU, STPU fiber membrane, and MPST electronic skin;

[0040] Figure 5 The high dynamic adaptability test diagrams shown in Example 1 are: (a) Ag / AgCl wet electrode group and (b) MPST group.

[0041] Figure 6 The following are electromyographic waveforms of different facial movements during the process of wearing the electronic skin shown in Example 1 to the jaw angle: (a) smiling to laughing, (b) clenching tightly for 10 seconds, (c) chewing on the right side, and (d) chewing on the left side.

[0042] Figure 7 The diagram shows (a) of the process of wearing the electronic skin shown in Example 1 onto the cheek area, and (b) and (c) facial diagrams in the states of stretching (b), compressing (c), twisting (d), and pressing (e).

[0043] Figure 8Comparison of erythema reaction before (a) and after (b) wearing the electronic skin shown in Example 1 on the cheek area;

[0044] Figure 9 The graphs show the comparison of membrane thickness, mechanical properties, and air permeability at different spinning times: (a) spinning for 1 minute, (b) spinning for 3 minutes, (c) spinning for 5 minutes, (d) spinning for 10 minutes, (e) stress-strain curves of fiber membranes made at different spinning times, and (f) water vapor permeability of fiber membranes made at different spinning times.

[0045] Figure 10 To test the cell viability of MPST in the CCK8 assay;

[0046] Figure 11 For the live-dead staining experiment after co-culturing MPST with cells, the control group was cells without intervention, (a) co-cultured for 24h, (b) co-cultured for 48h, (c) co-cultured for 72h;

[0047] Figure 12 Two weeks after MPST was implanted subcutaneously into rats, rat viscera were harvested for HE staining experiments.

[0048] Figure 13 The stress-strain curve is obtained by repeatedly stretching the electronic skin membrane prepared in Example 1 10 times at 60% strain.

[0049] Explanation of markings in the diagram:

[0050] 1-Electronic skin, 11-Flexible base layer, 111-Fiber core layer, 112-Fiber shell layer, 12-Conductive composite layer, 2-Skin layer. Detailed Implementation

[0051] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. All other embodiments obtained by those skilled in the art based on the given embodiments without creative effort are within the scope of protection of this application.

[0052] Unless otherwise specified, the reagents, methods, instruments and equipment used in this invention are conventional reagents, methods, instruments and equipment in the art.

[0053] An ultra-thin, breathable electronic skin, comprising:

[0054] The flexible substrate is a TPU / SF core-shell structured nanofiber membrane prepared by coaxial electrospinning, wherein TPU constitutes the fiber core layer and SF constitutes the fiber shell layer.

[0055] The conductive composite layer covering the surface of the flexible substrate is composed of a continuous conductive network formed by PEDOT:PSS and MXene, referred to as the MP conductive composite layer.

[0056] In some specific embodiments, the mass ratio of TPU to SF in the TPU / SF core-shell nanofiber membrane is 2 to 8:1, preferably 2 to 5, and more preferably 4 to 5.

[0057] In some specific embodiments, the coaxial electrospinning process is as follows: TPU solution and SF solution are electrospinned at different rates through a dual-syringe input system, with TPU as the inner core and SF as the outer shell; the spinning voltage is 14–18 kV, preferably 15–17 kV, and the collection distance is 15–25 cm, preferably 18–22 cm. The collection distance refers to the distance from the needle tip to the collecting electrode. The coaxial structure ensures that the fiber has high mechanical compliance, with an elongation of over 250%, adapting to dynamic deformation of facial muscles.

[0058] In some specific embodiments, the concentration of TPU in the TPU solution is 10wt% to 20wt%, preferably 12wt% to 18wt%; the solvent is an organic solvent, including DMF and THF.

[0059] In some specific embodiments, the concentration of SF in the SF solution is 10wt% to 20wt%, preferably 10wt% to 14wt%; the solvent is formic acid.

[0060] In some specific embodiments, the SF solution also includes a water-soluble polymer for improving spinning performance, including PEO at a concentration of 0.1 wt% to 0.5 wt%.

[0061] In some specific embodiments, the preparation process of the SF solution is as follows: degummed silk is dissolved in 8-12M LiBr solution at 50-70℃ and reacted for 1-10 hours, dialyzed with deionized water for 45-84 hours (water replacement time points: 1, 4, 8, 24, 36, 48, 60, 72 hours), centrifuged 1-3 times at 8000-10000 rpm × 10-30 min to remove impurities, and freeze-dried to obtain pure silk fibroin powder; the pure silk fibroin powder is dissolved in 98% formic acid, the SF concentration is 12wt%, and 0.1wt%-0.5wt% of water-soluble polymer is added to improve spinnability to prepare a spinning solution.

[0062] In some specific embodiments, the environmental conditions during coaxial electrospinning are: temperature 22-25°C, relative humidity 30%-50%.

[0063] In some specific embodiments, the electrospinning time in the coaxial electrospinning is 3 to 10 minutes, preferably 4 to 6 minutes.

[0064] In some specific embodiments, the general formula of the MXene is M n+ 1X n T x Where: M is an early transition metal, including Ti, Mo, V, Nb, Ta, and Cr; X is C or N; T x It is a surface terminating group, such as -OH, -O, -F; n is 1 to 4.

[0065] In some specific embodiments, the mass ratio of PEDOT:PSS to MXene is 1:1 to 20, preferably 1:1 to 10, and more preferably 1:1 to 5, which can ensure conductivity while avoiding MXene agglomeration.

[0066] In some specific embodiments, the preparation process of the conductive composite layer is as follows: PEDOT:PSS solution is mixed with MXene powder, and after ultrasonic dispersion, a uniform MP conductive composite liquid is obtained. This liquid is then uniformly coated onto the surface of a flexible substrate and dried to obtain the MP conductive composite layer.

[0067] In some specific embodiments, the concentration of the PEDOT:PSS solution is 1wt% to 5wt%, and the solvent is water.

[0068] In some specific embodiments, the ultrasonic dispersion power is 30–50 kHz and the time is 10–20 min, which helps to form a stable and uniformly distributed conductive network.

[0069] In some specific embodiments, the coating method is dip coating, the dip coating time is 10 to 20 minutes, and drying at room temperature can obtain a more uniform layer. After complete drying, it is placed in an oven at 50 to 70 degrees Celsius for annealing for 10 to 60 minutes to prevent PEDOT chain segment breakage or MXene oxidation and improve the stability of the conductive composite layer.

[0070] In some specific embodiments, the mass ratio of PEDOT to PSS in the TPU and MP conductive composite layer of the TPU / SF core-shell nanofiber membrane is 1:0.1 to 0.5.

[0071] In some specific embodiments, the thickness of the electronic skin is 1 to 5 μm, and the thickness ratio of the TPU / SF core-shell nanofiber membrane is 1:1 to 5.

[0072] In some specific embodiments, the water vapor permeability of the electronic skin is ≥300 g·m -2 ·h⁻¹, preferably 350–400 g·m⁻¹-2 •h-1, meets the skin's need for thermal and moisture balance during prolonged use.

[0073] A method for preparing an ultrathin, breathable electronic skin includes the following steps:

[0074] A flexible substrate layer was obtained by preparing a TPU / SF core-shell structured nanofiber membrane through coaxial electrospinning.

[0075] Preparation of MP conductive composite liquid;

[0076] The MP conductive composite liquid is uniformly coated on the surface of the TPU / SF core-shell structured nanofiber membrane, and after drying, a conductive composite layer is obtained, thus completing the preparation of electronic skin.

[0077] Application of an ultra-thin, breathable electronic skin in the field of sEMG data acquisition technology.

[0078] Each of the above embodiments can be implemented individually or in any combination of two or more.

[0079] The following description uses specific examples to illustrate the point.

[0080] Example 1

[0081] A method for preparing an ultrathin, breathable electronic skin includes the following steps:

[0082] (1) Preparation of TPU solution:

[0083] TPU particles (1185A, BASF, Germany) were dissolved in a mixed solvent of DMF and THF (mass ratio 1:1) to prepare a TPU solution with a concentration of 15 wt%. The solution was then magnetically stirred at 80°C for 2 hours to obtain the TPU solution.

[0084] (2) Preparation of SF solution:

[0085] Degummed silk (pure mulberry silk, finely dried cocoons, brand: Sangyi Tianxia) was dissolved in 9.3M LiBr solution at 60℃ for 4 hours, and then dialyzed with deionized water for 72 hours (water was changed at 1, 4, 8, 24, 36, 48, and 60 hours). The mixture was then centrifuged twice at 9000 rpm for 20 minutes to remove impurities, and then freeze-dried to obtain pure silk fibroin powder. The pure silk fibroin powder was dissolved in 98% formic acid to prepare a 12wt% SF solution, and 0.24wt% PEO was added and mixed evenly to obtain the SF solution.

[0086] (3) Preparation of TPU / SF core-shell structured nanofiber membranes:

[0087] Coaxial electrospinning technology was employed, with TPU solution as the inner core and SF solution as the outer shell. The voltage was set at 16kV, the TPU injection rate at 0.5mL / h, the SF injection rate at 1.5mL / h, the distance between the nozzle and the receiving plate at 20cm, the temperature at 22–25℃, and the relative humidity at 35%. The spinning time was 5 minutes, resulting in a TPU / SF core-shell structured nanofiber membrane with a thickness of approximately 3μm, namely the flexible substrate layer 1. TPU constitutes the fiber core layer 111, and SF constitutes the fiber shell layer 112.

[0088] (4) Preparation of MXene powder

[0089] Using Ti3AlC2 (MAX phase) as a precursor, 2g of lithium fluoride (LiF) powder (Sigma-Aldrich; CAS: 7789-24-4) was first dissolved in 20ml of 9mmol / L hydrochloric acid (HCl) solution. Then, 1g of Ti3AlC2 powder (Jilin Yiyi Technology Co., Ltd.; CAS: 196506-01-01) was added, and the mixture was stirred at 50℃ for 30 hours. The resulting solution was removed, washed repeatedly with water 5 times, and then sonicated for 1 hour. After centrifugation, deionized water was added to the resulting solid, and the concentration of the MXene solution was measured. MXene (Ti3C2T) was obtained by lyophilization. x )powder.

[0090] (5) Preparation of MP conductive composite layer

[0091] MXene powder and PEDOT:PSS solution (Clevios PH 1000) were weighed and mixed at a mass ratio of 3:1. The mixture was then ultrasonically dispersed at 40 kHz for 20 min to form a uniform MP conductive composite liquid. The TPU / SF core-shell nanofiber membrane was placed in a petri dish containing the MP conductive composite liquid and immersed for 20 min. The MP conductive composite liquid was then coated onto its surface using a dip-coating method. After drying at room temperature for 20 min, it was annealed in an oven at 60 °C for 30 min to obtain conductive composite layer 12. The electronic skin 1 was thus prepared and named MPST electronic skin membrane. The obtained MPST electronic skin membrane has a complete structure, uniform surface, resistance below 20 Ω / sq, and good flexibility and water vapor permeability. Figures 1-3 As shown, the flexible substrate and conductive composite layer structure of the ultrathin breathable electronic skin has been confirmed.

[0092] Example 2

[0093] Compared with Example 1, most of them are the same, except that in step (3) the spinning time of the TPU / SF core-shell nanofiber membrane is adjusted to 3 minutes.

[0094] Example 3

[0095] Compared with Example 1, most of them are the same, except that in step (3) the spinning time of the TPU / SF core-shell nanofiber membrane is adjusted to 10 minutes.

[0096] Comparative Example 1

[0097] Compared with Example 1, most of them are the same, except that in step (3) the spinning time of the TPU / SF core-shell nanofiber membrane is adjusted to 1 minute.

[0098] Comparative Example 2

[0099] Compared to Example 1, most aspects are the same, except that the flexible substrate 1 is not coaxially electrospun, but instead uses pure TPU electrospun. The specific preparation process is as follows: TPU particles are dissolved in a mixed solvent of DMF and THF (mass ratio 1:1) to prepare a 15wt% TPU solution, which is then magnetically stirred at 80°C for 2 hours to obtain the TPU solution. The solution is assembled onto a single spinning needle, and electrospun using the same spinning parameters as in Example 1. The spinning time is 5 minutes, resulting in a pure TPU fiber membrane. Finally, an electronic skin of pure TPU fiber membrane is prepared.

[0100] TPU is a synthetic polymer material. Although its biocompatibility is acceptable, it is far inferior to that of natural SF. Its surface chemistry is unfavorable for cell adhesion and growth, and long-term contact with the skin may cause mild discomfort or inflammatory reactions, making it less than ideal as a biointerface layer for electronic skin. Pure TPU fiber membranes for electronic skin lack the specific biological functions provided by SF. If electronic skin requires close biointegration with the human body, pure TPU fiber membranes are unsuitable.

[0101] Comparative Example 3

[0102] Compared to Example 1, most aspects are the same, except that the flexible substrate 1 is not coaxially electrospun, but rather pure SF electrospun. Specifically, the preparation process involves dissolving pure silk fibroin powder in 98% formic acid to prepare a 12wt% SF solution, and then adding 0.24wt% PEO and mixing thoroughly to obtain the SF solution. Electrospun is performed using the same spinning parameters as in Example 1. The spinning time is 5 minutes, resulting in a pure SF fiber membrane. Finally, an electronic skin made of pure SF fiber membrane is prepared.

[0103] The inherent drawbacks of SF materials are their high brittleness and poor toughness. Electronic skin made of pure SF fiber membranes typically has low mechanical strength, making it prone to cracking and breakage, and exhibiting poor durability and fatigue resistance. It cannot withstand the repeated stretching, bending, and friction that are unavoidable in daily use, leading to low reliability and easy failure. Furthermore, the performance of SF is sensitive to environmental humidity and temperature, which may affect the long-term stability of the electronic skin's performance.

[0104] Performance testing:

[0105] (1) Contact angle

[0106] Contact angle tests were performed on the electronic skin (MPST group) in Example 1, the TPU / SF core-shell nanofiber membrane (sTPU), and the pure TPU fiber membrane in Comparative Example 2.

[0107] Figure 4 Contact angle test data indicate that a TPU / SF core-shell nanofiber membrane with TPU as the core layer and SF as the shell layer has been successfully prepared. Specifically, the electronic skin surface of the pure TPU fiber membrane exhibits hydrophobic properties, with a water contact angle greater than 100°. Figure 4 According to research, SF surface exhibits hydrophilic properties, with a water contact angle of less than 50°. The core-shell structure fiber described in this invention benefits from the outer SF shell, which provides an excellent hydrophilic surface. This property significantly improves the wettability and adhesion of PEDOT:PSS on the fiber surface, allowing PEDOT:PSS to bond more uniformly and firmly to the fiber surface, forming a conductive composite interface with excellent conductivity and stability.

[0108] (2) High dynamic adaptability

[0109] MPST Group: The MPST electronic skin 1 membrane prepared in Example 1 was cut into 20mm × 20mm pieces and attached to the subject's skin layer 2 (in this case, the right mandibular angle). A data acquisition circuit was connected to record actions such as chewing, smiling, and opening the mouth. Figure 5 As shown.

[0110] Ag / AgCl wet electrode group: Ag / AgCl wet electrodes (X-1, Hangzhou Xunda Wireless Equipment) were used as a control. Specifically, commercial electrodes were attached to the left masseter muscle of the volunteers, while MPST electrodes were attached to the right masseter muscle. All electrodes were connected to the signal recording system through a 10Hz to 10kHz bandpass filter. Data acquisition was performed using the BCIduino system developed by HANGYI BCI Network. When the subjects performed clenching movements, the system recorded the corresponding electromyographic signals, such as... Figure 5 As shown.

[0111] The results showed that, Figure 6 Clear potential fluctuations were observed within 100-150ms after the action was initiated, indicating stable signal and good repeatability. This demonstrates that the product of this invention can stably adhere to the face and acquire sEMG signals with high quality.

[0112] (3) Long-term breathability

[0113] MPST group: The MPST electronic skin membrane prepared in Example 1 was cut into 20mm × 20mm pieces and applied to the facial skin layer 2 (cheek area) of the subject. After 3 hours, the skin condition was observed and photographs were taken to assess the erythema area. Figure 7 As shown.

[0114] Ag / AgCl wet electrode group: Ag / AgCl wet electrode was used as a control.

[0115] The results showed that Figure 7 This demonstrates that it does not delaminate under dynamic deformations such as tension (b), compression (c), torsion (d), and pressing (e). Figure 8 The MPST group showed no obvious erythema and almost no irritation after 3 hours of application, compared with the Ag / AgCl wet electrode group.

[0116] (4) Effect of electrospinning time on film thickness and properties

[0117] Comparative Examples 1-3 and Comparative Example 1 evaluated the effect of electrospinning time on film thickness and performance. Spinning times were set to 1, 3, 5, and 10 min, respectively, while keeping other parameters consistent. Figure 9 As shown, the results indicate that the film thickness gradually increases with increasing spinning time. Figure 9 (a~d), mechanical strength is enhanced ( Figure 9 e), but water vapor transmission rate decreases ( Figure 9 f). The sample prepared in 5 minutes achieved a good balance between conductivity, flexibility, and breathability, making it suitable for use as a practical electronic skin.

[0118] (5) Biosafety and feasibility of long-term wear

[0119] MPST Group: The MPST electronic skin membrane prepared in Example 1 was validated by 72-hour NIH-3T3 cell culture (SCC-220911, Solarbio). Specifically, cells were seeded at a density of 1×10^3 in three 96-well cell culture plates. After cell adhesion, the electronic skin prepared in Example 1 was added to the MPST group, and co-cultured for 24h, 48h, and 72h, respectively. CCK8 and cell viability staining tests were performed using CCK8 reagent (C0037, Beyotime, Shanghai). 10 μL of CCK8 solution was added to each well, and the cells were incubated at 37℃ for 3h. The absorbance was then measured at 450nm using a microplate reader.

[0120] STPU group: Compared with MPST group, the electronic skin is modified to be a TPU / SF core-shell nanofiber membrane, and all other aspects are the same.

[0121] Con (control) group: Compared with the MPST group, the electronic skin prepared in Example 1 was not added, and everything else was the same.

[0122] Experimental results showed that the relative proliferation rate of the MPST group was greater than 90%, demonstrating its good biocompatibility. Figure 10 ).

[0123] Cells treated with the same method were stained using a live-dead cell staining kit (C2015M, Beyotime, Shanghai) to perform live-dead cell staining experiments (Calcein AM, Propidium Iodide (PI), and superposition), and images were taken using a fluorescence microscope (Leica). The results showed that the electronic skin was non-toxic to cells. Figure 11 .

[0124] MPST was implanted subcutaneously into the back of rats. Two weeks later, their internal organs (heart, liver, spleen, lung, and kidney) were removed and stained with hematoxylin and eosin (HE) to observe the in vivo biocompatibility of the electronic skin. Figure 12 The study included MPST (MPST group) and blank (con group). Combining cell and animal experimental data, the study demonstrated the excellent biocompatibility and long-term wear feasibility of the MPST electronic skin membrane.

[0125] (6) Mechanical properties

[0126] The MPST electronic skin membrane prepared in Example 1 was subjected to mechanical property testing using a universal mechanical testing machine (ESM303, Mark-10, USA). All samples were transferred to a 20 mm x 10 mm suspended polyimide frame and placed vertically on a tensile testing machine. The samples were then separated from the left and right sides of the polyimide frame, and the left and right sides of the polyimide frame were cut off with a sharp knife before tensile testing. The results showed that the electronic skin membrane could withstand 10 cycles at 60% strain without significant mechanical fatigue, and no surface cracks or delamination were observed. Figure 13 .

[0127] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. An ultra-thin, breathable electronic skin, characterized in that, include: The flexible substrate is a TPU / SF core-shell structured nanofiber membrane prepared by coaxial electrospinning, wherein TPU constitutes the fiber core layer and SF constitutes the fiber shell layer. The conductive composite layer covering the surface of the flexible substrate is composed of a continuous conductive network formed by combining PEDOT:PSS and MXene.

2. The ultra-thin breathable electronic skin according to claim 1, characterized in that, The mass ratio of TPU to SF in the TPU / SF core-shell structured nanofiber membrane is 2 to 8:

1.

3. The ultra-thin breathable electronic skin according to claim 1, characterized in that, The specific process of coaxial electrospinning is as follows: TPU solution and SF solution are electrospinned at different rates through a dual-syringe input system, with TPU as the inner core and SF as the outer shell. The spinning voltage is 14–18 kV, and the collection distance is 15–25 cm.

4. The ultra-thin breathable electronic skin according to claim 1, characterized in that, The mass ratio of PEDOT:PSS to MXene is 1:1 to 20.

5. The ultra-thin breathable electronic skin according to claim 1, characterized in that, The preparation process of the MP conductive composite layer is as follows: PEDOT:PSS solution is mixed with MXene powder, and after ultrasonic dispersion, a uniform MP composite liquid is obtained. This liquid is then uniformly coated onto the surface of a flexible substrate and dried to obtain the MP conductive composite layer.

6. The ultra-thin breathable electronic skin according to claim 1, characterized in that, In the TPU / SF core-shell nanofiber membrane, the mass ratio of PEDOT to PSS in the TPU and MP conductive composite layer is 1:0.1 to 0.

5.

7. The ultra-thin breathable electronic skin according to claim 1, characterized in that, The thickness of the electronic skin is 1–5 μm, and the thickness ratio of the TPU / SF core-shell nanofiber membrane is 1:1–5.

8. The ultra-thin breathable electronic skin according to claim 1, characterized in that, The water vapor permeability of this electronic skin is ≥300 g·m -2 ·h-1.

9. A method for preparing an ultrathin, breathable electronic skin as described in any one of claims 1 to 8, characterized in that, Includes the following steps: A flexible substrate layer was obtained by preparing a TPU / SF core-shell structured nanofiber membrane through coaxial electrospinning. Preparation of conductive composite liquid; The conductive composite liquid is uniformly coated on the surface of the TPU / SF core-shell nanofiber membrane, and after drying, a conductive composite layer is obtained, thus completing the preparation of electronic skin.

10. The application of an ultrathin, breathable electronic skin as described in any one of claims 1 to 8 in the field of sEMG acquisition technology.

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