Skin-friendly leather for electronic skin and preparation method thereof

Abstract

The invention relates to the technical field of electronic skin, in particular to skin-friendly leather for electronic skin and a preparation method thereof.The preparation method of the skin-friendly leather for electronic skin comprises the steps that (1) natural leather is sequentially subjected to deliming liquid soaking, softening enzyme liquid softening treatment and ionic liquid tanning liquid tanning, then washed to be neutral, freeze-dried and then ground to remove an epidermal layer, and the skin-friendly leather for electronic skin is obtained; a collagenous fiber net-shaped substrate is obtained; (2) adding a skin-friendly modifier into deionized water, carrying out ultrasonic dispersion, then adding a conductive component, and continuously carrying out ultrasonic dispersion to obtain a modified solution; and (3) immersing the collagenous fiber net-shaped substrate into the modification liquid, carrying out immersion treatment, draining water, carrying out hot-pressing shaping, and cooling to obtain the skin-friendly leather for the electronic skin. The skin-friendly leather for the electronic skin is excellent in comprehensive performance and has excellent skin-friendly softness, ventilation comfort, stable conductivity and long-acting antibacterial property, and reliable material support is provided for application of the electronic skin in the fields of medical monitoring, intelligent wearing and the like.

Description

Technical Field

[0001] This application relates to the field of electronic skin technology, and more specifically, it relates to a skin-friendly leather for electronic skin and a method for preparing the same. Background Technology

[0002] Electronic skin, as an artificial intelligence interface that mimics the functions of human skin, has broad application prospects in fields such as intelligent robots, medical and health monitoring, bionic prostheses, and wearable devices. An ideal electronic skin must simultaneously possess excellent flexibility, tactile sensing capabilities, biocompatibility, and long-term wearing comfort. Among these, skin-friendliness is one of the key indicators determining the user experience of wearable devices and their compatibility with medical devices.

[0003] Currently, most mainstream electronic skins use synthetic polymers (such as polydimethylsiloxane PDMS, polyimide PI, and polyethylene terephthalate PET) as base materials. Although these materials can achieve certain flexibility and sensing performance, they have significant drawbacks: PDMS and other materials have poor breathability, which can lead to sweat accumulation during long-term wear, reducing wearing comfort and potentially corroding sensing elements and affecting detection stability; PI materials are expensive, and their biocompatibility differs significantly from the natural composition of human skin; PET, due to insufficient elasticity, is difficult to adapt to the deformation requirements of dynamic parts such as joints. In addition, the integration of multimodal sensors in existing electronic skins requires complex microfabrication processes, resulting in high manufacturing costs and hindering large-scale production, thus limiting their industrial application.

[0004] Leather, a natural collagen material derived from animal hides, possesses a collagen composition similar to human skin, exhibiting natural biocompatibility, good breathability, and excellent flexibility. It also retains a hierarchical fiber network structure ranging from nanoscale to macroscale, providing an ideal platform for constructing highly sensitive sensing units. While existing technologies have attempted to combine leather with nano-conductive materials to prepare electronic skin, these techniques still have shortcomings: firstly, the dispersion uniformity of conductive materials within the leather fiber network is poor, leading to large fluctuations in sensing sensitivity and poor response consistency; secondly, no specific modification has been made to enhance the skin-friendliness of electronic skin, and residual tanning agents on the leather surface may cause skin irritation. Furthermore, there is a lack of optimization for adaptability to actual wearing environments such as sweat and friction, making it difficult to meet the requirements for long-term skin-friendly wear. Therefore, addressing the technical problems of poor skin-friendliness, insufficient breathability, limited sensing performance, and complex manufacturing processes in existing electronic skin substrate materials, developing a skin-friendly leather for electronic skin that combines high skin-friendliness, excellent breathability, and ease of large-scale production has significant technological value and application prospects. Summary of the Invention

[0005] To address the technical problems mentioned in the background section, this application provides a skin-friendly leather for electronic skin and a method for preparing the same.

[0006] This application provides a method for preparing skin-friendly leather for electronic skin, using the following technical solution: A method for preparing skin-friendly leather for electronic skin includes the following preparation steps: (1) The natural leather is soaked in deliming solution, softened by softening enzyme solution, tanned by ionic liquid tanning solution, washed until neutral, freeze-dried and then polished to remove the epidermis to obtain a collagen fiber network base. (2) Add the skin-friendly modifier to deionized water, ultrasonically disperse for 10-20 min, then add the conductive component, and continue ultrasonically disperse for 20-30 min to obtain the modified solution; (3) The collagen fiber mesh substrate is immersed in the modification liquid for impregnation treatment. After draining the water, it is hot-pressed and shaped. After cooling, the skin-friendly leather for electronic skin is obtained.

[0007] Preferably, the natural leather in step (1) is one of pigskin, cowhide, or sheepskin.

[0008] Preferably, the deashing solution in step (1) is an ammonium chloride aqueous solution with a mass concentration of 3-5% and a soaking temperature of 25-35℃.

[0009] Preferably, the softening enzyme solution in step (1) is composed of neutral protease, elastase, keratinase and deionized water in a mass ratio of 5-8:2-3:1-2:30-50.

[0010] Preferably, the pH value of the softening enzyme solution in step (1) is 6.0-7.0.

[0011] Preferably, the softening treatment temperature in step (1) is 28-38℃ and the treatment time is 4-6h.

[0012] Preferably, in step (1), the ionic liquid tanning liquor is composed of 1-butyl-3-methylimidazolium chloride, citric acid, glycerol and deionized water in a mass ratio of 4-6:0.3-0.5:1-2:100; and the tanning temperature is 35-40℃.

[0013] Preferably, the preparation method of the skin-friendly modifier in step (2) includes the following preparation steps: Hydroxypropyltrimethylammonium chloride chitosan was dispersed in deionized water, the pH was adjusted to 7.2-7.5, and the mixture was stirred evenly. Polyγ-glutamic acid was added, the temperature was raised to 50-55℃, and the mixture was stirred for 20-30 minutes. Citric acid was added, and the mixture was stirred for another 10-20 minutes. The temperature was raised to 60-65℃, and a skin-friendly nonionic surfactant was added. The mixture was kept at this temperature for 3-4 hours. After the reaction was completed, the mixture was dialyzed with deionized water, freeze-dried, and pulverized to obtain a skin-friendly modifier.

[0014] Preferably, the mass ratio of the hydroxypropyltrimethylammonium chloride chitosan, polyγ-glutamic acid, and skin-friendly nonionic surfactant is 4-6:2-3:1-1.5.

[0015] Preferably, the skin-friendly nonionic surfactant is composed of polyglycerol-3 dioleate and polyglycerol-10 stearate in a mass ratio of 5-8:2-4.

[0016] Preferably, the conductive component in step (2) is composed of graphene and polyaniline in a mass ratio of 1-2:3-5.

[0017] Preferably, the amount of conductive component added in step (2) is 8-12% of the mass of the skin-friendly modifier.

[0018] Preferably, in step (3), the hot pressing temperature is 50-60℃, the hot pressing pressure is 0.3-0.5MPa, and the hot pressing time is 15-20min.

[0019] A skin-friendly leather for electronic skin is prepared by the above-described preparation method.

[0020] In summary, this application has the following beneficial effects: This application prepares a softening enzyme solution by combining neutral protease, elastase, and keratinase. This solution works synergistically on sheepskin raw materials, fully degrading the adhesive substances between collagen fibers and forming a loose and uniform collagen fiber network substrate. This preserves the natural biocompatibility of collagen fibers and provides ample channels for the loading of subsequent modifying components, effectively improving the softness and breathability of the substrate. It solves the problems of uneven fiber degradation, brittle substrate, or poor breathability caused by single-enzyme softening. Through precise compounding of hydroxypropyltrimethylammonium chloride chitosan and polyγ-glutamic acid, combined with citric acid crosslinking modification and modification with a nonionic surfactant compounded in a specific ratio of polyglycerol-3 dioleate and polyglycerol-10 stearate, the prepared skin-friendly modifier possesses excellent hydrophilicity, biocompatibility, and interfacial compatibility. It not only forms a stable skin-friendly coating on the surface of the collagen fiber network substrate, reducing irritation when the leather comes into contact with the skin, but also enhances the substrate's affinity for skin secretions, improving the comfort of long-term skin contact. By adjusting the ratio of skin-friendly modifier to conductive component and using ultrasonic dispersion technology, the conductive component can be uniformly dispersed in the modification liquid and stably loaded onto the collagen fiber network substrate. This ensures that the leather has excellent conductivity while avoiding the agglomeration of conductive component that could lead to decreased skin-friendliness or damage to mechanical properties. Combined with subsequent precise impregnation and hot pressing processes, the modified component is firmly bonded to the collagen fiber, further enhancing the structural stability of the leather.

[0021] In summary, this application, through the synergistic compounding of enzymes and the precise preparation and process optimization of skin-friendly modifiers, enables the final electronic skin-friendly leather to possess excellent skin-friendliness, softness and breathability, stable conductivity and antibacterial properties. Even after being soaked in artificial sweat, it can still maintain good antibacterial efficacy, fully meeting the core requirement of long-term skin contact for electronic skin, and solving the technical pain points of insufficient skin-friendliness and poor performance stability of existing electronic skin substrates. Detailed Implementation

[0022] The present application will be further described in detail below with reference to the embodiments.

[0023] The neutral protease used in the embodiments and comparative examples of this application was purchased from Weifang Ruichen Biotechnology Co., Ltd.; the elastase was purchased from Wuhan Jiangxin Biotechnology Co., Ltd.; the keratinase was purchased from Hebei Jiuyu Biotechnology Co., Ltd.; the graphene (model: LG-1402) was purchased from Henan Wanying Refractory Materials Technology Co., Ltd.; the polyaniline was purchased from Hubei Jiufenglong Chemical Co., Ltd.; the hydroxypropyltrimethylammonium chloride chitosan was purchased from Jiangsu Caiwei Biotechnology Co., Ltd.; the polyγ-glutamic acid was purchased from Hebei Chuangzhiyuan Biotechnology Co., Ltd.; the polyglycerol-3 dioleate was purchased from Qingdao Tengyun Chemical Technology Co., Ltd.; and the polyglycerol-10 stearate was purchased from Shandong Binzhou Jinsheng New Material Technology Co., Ltd.

[0024] Examples 1-3 provide a skin-friendly leather for electronic skin and a method for preparing the same.

[0025] Example 1 A method for preparing skin-friendly leather for electronic skin includes the following preparation steps: (1) The sheepskin was soaked in a 3% ammonium chloride aqueous solution at 25°C for 30 min, softened in a softening enzyme solution with a pH of 6.0 at 28°C for 4 h, tanned in an ionic liquid tanning liquor for 4 h at a tanning temperature of 35°C, washed with deionized water until neutral, and freeze-dried at -20°C for 5 h. The epidermal layer was removed by polishing to obtain a collagen fiber network base. The softening enzyme solution was composed of neutral protease, elastase, keratinase and deionized water in a mass ratio of 5:2:1:30. The ionic liquid tanning liquor was composed of 1-butyl-3-methylimidazolium chloride, citric acid, glycerol and deionized water in a mass ratio of 4:0.3:1:100. (2) Add the skin-friendly modifier to deionized water, and control the mass ratio of the skin-friendly modifier to deionized water to be 1:10. Use an ultrasonic power of 100W and an ultrasonic frequency of 40kHz to ultrasonically disperse for 10 minutes. Then add the conductive component and continue ultrasonic dispersion for 20 minutes to obtain the modified liquid. The conductive component is composed of graphene and polyaniline in a mass ratio of 1:3. The amount of conductive component added is 8% of the mass of the skin-friendly modifier. The preparation method of the skin-friendly modifier includes the following preparation steps: Hydroxypropyltrimethylammonium chloride chitosan was dispersed in deionized water, with the mass ratio of hydroxypropyltrimethylammonium chloride chitosan to deionized water controlled at 2:10. The pH was adjusted to 7.2, and the mixture was stirred at 200 rpm until homogeneous. Polyγ-glutamic acid was added, and the mixture was heated to 50°C and stirred for 20 min to obtain a mixed solution. Citric acid (2% of the total mass of the mixed solution) was added, and the mixture was stirred for another 10 min. The temperature was raised to 60°C, and a skin-friendly nonionic surfactant was added. The mixture was kept at this temperature for 3 h. After the reaction was completed, the mixture was transferred to a dialysis bag with a molecular weight cutoff of 20 kDa. After dialysis with deionized water for 24 h, the mixture was freeze-dried at -30°C for 10 h, pulverized, and passed through a 100-mesh sieve to obtain a skin-friendly modifier. The mass ratio of hydroxypropyltrimethylammonium chloride chitosan, polyγ-glutamic acid, and the skin-friendly nonionic surfactant was 4:2:1. The skin-friendly nonionic surfactant was composed of polyglycerol-3 dioleate and polyglycerol-10 stearate in a mass ratio of 5:2. (3) The collagen fiber mesh substrate is immersed in the modification solution, and the mass ratio of the collagen fiber mesh substrate to the modification solution is controlled to be 1:5. The immersion treatment is carried out for 10 hours at an immersion temperature of 40°C. After draining the water, the substrate is hot-pressed at a temperature of 50°C and a pressure of 0.3MPa for 15 minutes. After cooling, the skin-friendly leather for electronic skin is obtained.

[0026] Example 2 A method for preparing skin-friendly leather for electronic skin includes the following preparation steps: (1) The sheepskin was soaked in a 4% ammonium chloride aqueous solution at 30°C for 45 min, softened in a softening enzyme solution with a pH of 6.5 at 33°C for 5 h, tanned in an ionic liquid tanning liquor for 5 h at a tanning temperature of 38°C, washed with deionized water until neutral, and freeze-dried at -25°C for 7 h. The epidermal layer was removed by polishing to obtain a collagen fiber network base. The softening enzyme solution was composed of neutral protease, elastase, keratinase and deionized water in a mass ratio of 7:2.5:1.5:40. The ionic liquid tanning liquor was composed of 1-butyl-3-methylimidazolium chloride, citric acid, glycerol and deionized water in a mass ratio of 5:0.4:1.5:100. (2) Add the skin-friendly modifier to deionized water, and control the mass ratio of the skin-friendly modifier to deionized water to be 2:11. Use an ultrasonic power of 110W and an ultrasonic frequency of 50kHz to ultrasonically disperse for 15 minutes. Then add the conductive component and continue ultrasonic dispersion for 25 minutes to obtain the modified liquid. The conductive component is composed of graphene and polyaniline in a mass ratio of 1.5:4. The amount of conductive component added is 10% of the mass of the skin-friendly modifier. The preparation method of the skin-friendly modifier includes the following preparation steps: Hydroxypropyltrimethylammonium chloride chitosan was dispersed in deionized water at a mass ratio of 2.5:10, and the pH was adjusted to 7.4. The mixture was stirred at 250 rpm until homogeneous. Polyγ-glutamic acid was added, and the mixture was heated to 53°C and stirred for 25 minutes to obtain a final solution. Citric acid (2.5% of the total mass of the final solution) was added, and the mixture was stirred for another 15 minutes. The temperature was then raised to 62°C, and a skin-friendly nonionic surfactant was added. The reaction was maintained at this temperature. After 3.5 hours of reaction, the mixture was transferred to a dialysis bag with a molecular weight cutoff of 20 kDa. After dialysis with deionized water for 24 hours, it was freeze-dried at -35°C for 11 hours and then pulverized through a 150-mesh sieve to obtain a skin-friendly modifier. The mass ratio of hydroxypropyltrimethylammonium chloride chitosan, polyγ-glutamic acid, and skin-friendly nonionic surfactant was 5:2.5:1.2. The skin-friendly nonionic surfactant was composed of polyglycerol-3 dioleate and polyglycerol-10 stearate in a mass ratio of 7:3. (3) The collagen fiber mesh substrate is immersed in the modification solution, and the mass ratio of the collagen fiber mesh substrate to the modification solution is controlled to be 2:7. The immersion treatment is carried out for 11 hours at an immersion temperature of 48°C. After draining the water, the substrate is hot-pressed at a temperature of 55°C and a pressure of 0.4MPa for 18 minutes. After cooling, the skin-friendly leather for electronic skin is obtained.

[0027] Example 3 A method for preparing skin-friendly leather for electronic skin includes the following preparation steps: (1) The sheepskin was soaked in a 5% ammonium chloride aqueous solution at 35°C for 60 min, softened in a softening enzyme solution with a pH of 7.0 at 38°C for 6 h, tanned in an ionic liquid tanning liquor for 6 h at a tanning temperature of 40°C, washed with deionized water until neutral, and freeze-dried at -30°C for 8 h. The epidermis was then removed by polishing to obtain a collagen fiber network base. The softening enzyme solution consisted of neutral protease, elastase, keratinase and deionized water in a mass ratio of 8:3:2:50. The ionic liquid tanning liquor consisted of 1-butyl-3-methylimidazolium chloride, citric acid, glycerol and deionized water in a mass ratio of 6:0.5:2:100. (2) Add the skin-friendly modifier to deionized water, and control the mass ratio of the skin-friendly modifier to deionized water to be 3:12. Use an ultrasonic power of 120W and an ultrasonic frequency of 60kHz to ultrasonically disperse for 20 minutes. Then add the conductive component and continue ultrasonic dispersion for 30 minutes to obtain the modified liquid. The conductive component is composed of graphene and polyaniline in a mass ratio of 2:5. The amount of conductive component added is 12% of the mass of the skin-friendly modifier. The preparation method of the skin-friendly modifier includes the following preparation steps: Hydroxypropyltrimethylammonium chloride chitosan was dispersed in deionized water, with the mass ratio of hydroxypropyltrimethylammonium chloride chitosan to deionized water controlled at 3:10. The pH was adjusted to 7.5, and the mixture was stirred at 300 rpm until homogeneous. Polyγ-glutamic acid was added, and the mixture was heated to 55°C and stirred for 30 min to obtain a mixed solution. Citric acid (3% of the total mass of the mixed solution) was added, and the mixture was stirred for another 20 min. The temperature was raised to 65°C, and a skin-friendly nonionic surfactant was added. The mixture was kept at this temperature for 4 h. After the reaction was completed, the mixture was transferred to a dialysis bag with a molecular weight cutoff of 20 kDa. After dialysis with deionized water for 24 h, the mixture was freeze-dried at -40°C for 12 h, pulverized, and passed through a 200-mesh sieve to obtain a skin-friendly modifier. The mass ratio of hydroxypropyltrimethylammonium chloride chitosan, polyγ-glutamic acid, and the skin-friendly nonionic surfactant was 6:3:1.5. The skin-friendly nonionic surfactant was composed of polyglycerol-3 dioleate and polyglycerol-10 stearate in a mass ratio of 8:4. (3) The collagen fiber mesh substrate is immersed in the modification solution, and the mass ratio of the collagen fiber mesh substrate to the modification solution is controlled to be 3:8. The immersion treatment is carried out for 12 hours at a temperature of 55°C. After draining the water, the substrate is hot-pressed at a temperature of 60°C and a pressure of 0.5MPa for 20 minutes. After cooling, the skin-friendly leather for electronic skin is obtained.

[0028] Comparative Example 1 A method for preparing skin-friendly leather for electronic skin includes the following preparation steps: (1) The sheepskin was soaked in a 3% ammonium chloride aqueous solution at 25°C for 30 min, softened in a softening enzyme solution with a pH of 6.0 at 28°C for 4 h, tanned in an ionic liquid tanning liquor for 4 h at a tanning temperature of 35°C, washed with deionized water until neutral, and freeze-dried at -20°C for 5 h. The epidermis was then removed by polishing to obtain a collagen fiber network base. The softening enzyme solution consisted of neutral protease, keratinase and deionized water in a mass ratio of 5:3:30. The ionic liquid tanning liquor consisted of 1-butyl-3-methylimidazolium chloride, citric acid, glycerol and deionized water in a mass ratio of 4:0.3:1:100. (2) Add the skin-friendly modifier to deionized water, and control the mass ratio of the skin-friendly modifier to deionized water to be 1:10. Use an ultrasonic power of 100W and an ultrasonic frequency of 40kHz to ultrasonically disperse for 10 minutes. Then add the conductive component and continue ultrasonic dispersion for 20 minutes to obtain the modified liquid. The conductive component is composed of graphene and polyaniline in a mass ratio of 1:3. The amount of conductive component added is 8% of the mass of the skin-friendly modifier. The preparation method of the skin-friendly modifier includes the following preparation steps: Hydroxypropyltrimethylammonium chloride chitosan was dispersed in deionized water, with the mass ratio of hydroxypropyltrimethylammonium chloride chitosan to deionized water controlled at 2:10. The pH was adjusted to 7.2, and the mixture was stirred at 200 rpm until homogeneous. Polyγ-glutamic acid was added, and the mixture was heated to 50°C and stirred for 20 min to obtain a mixed solution. Citric acid (2% of the total mass of the mixed solution) was added, and the mixture was stirred for another 10 min. The temperature was raised to 60°C, and a skin-friendly nonionic surfactant was added. The mixture was kept at this temperature for 3 h. After the reaction was completed, the mixture was transferred to a dialysis bag with a molecular weight cutoff of 20 kDa. After dialysis with deionized water for 24 h, the mixture was freeze-dried at -30°C for 10 h, pulverized, and passed through a 100-mesh sieve to obtain a skin-friendly modifier. The mass ratio of hydroxypropyltrimethylammonium chloride chitosan, polyγ-glutamic acid, and the skin-friendly nonionic surfactant was 4:2:1. The skin-friendly nonionic surfactant was composed of polyglycerol-3 dioleate and polyglycerol-10 stearate in a mass ratio of 5:2. (3) The collagen fiber mesh substrate is immersed in the modification solution, and the mass ratio of the collagen fiber mesh substrate to the modification solution is controlled to be 1:5. The immersion treatment is carried out for 10 hours at an immersion temperature of 40°C. After draining the water, the substrate is hot-pressed at a temperature of 50°C and a pressure of 0.3MPa for 15 minutes. After cooling, the skin-friendly leather for electronic skin is obtained.

[0029] Comparative Example 2 A method for preparing skin-friendly leather for electronic skin includes the following preparation steps: (1) The sheepskin was soaked in a 3% ammonium chloride aqueous solution at 25°C for 30 min, softened in a softening enzyme solution with a pH of 6.0 at 28°C for 4 h, tanned in an ionic liquid tanning liquor for 4 h at a tanning temperature of 35°C, washed with deionized water until neutral, and freeze-dried at -20°C for 5 h. The epidermal layer was removed by polishing to obtain a collagen fiber network base. The softening enzyme solution was composed of neutral protease, elastase and deionized water in a mass ratio of 5:3:30. The ionic liquid tanning liquor was composed of 1-butyl-3-methylimidazolium chloride, citric acid, glycerol and deionized water in a mass ratio of 4:0.3:1:100. (2) Add the skin-friendly modifier to deionized water, and control the mass ratio of the skin-friendly modifier to deionized water to be 1:10. Use an ultrasonic power of 100W and an ultrasonic frequency of 40kHz to ultrasonically disperse for 10 minutes. Then add the conductive component and continue ultrasonic dispersion for 20 minutes to obtain the modified liquid. The conductive component is composed of graphene and polyaniline in a mass ratio of 1:3. The amount of conductive component added is 8% of the mass of the skin-friendly modifier. The preparation method of the skin-friendly modifier includes the following preparation steps: Hydroxypropyltrimethylammonium chloride chitosan was dispersed in deionized water, with the mass ratio of hydroxypropyltrimethylammonium chloride chitosan to deionized water controlled at 2:10. The pH was adjusted to 7.2, and the mixture was stirred at 200 rpm until homogeneous. Polyγ-glutamic acid was added, and the mixture was heated to 50°C and stirred for 20 min to obtain a mixed solution. Citric acid (2% of the total mass of the mixed solution) was added, and the mixture was stirred for another 10 min. The temperature was raised to 60°C, and a skin-friendly nonionic surfactant was added. The mixture was kept at this temperature for 3 h. After the reaction was completed, the mixture was transferred to a dialysis bag with a molecular weight cutoff of 20 kDa. After dialysis with deionized water for 24 h, the mixture was freeze-dried at -30°C for 10 h, pulverized, and passed through a 100-mesh sieve to obtain a skin-friendly modifier. The mass ratio of hydroxypropyltrimethylammonium chloride chitosan, polyγ-glutamic acid, and the skin-friendly nonionic surfactant was 4:2:1. The skin-friendly nonionic surfactant was composed of polyglycerol-3 dioleate and polyglycerol-10 stearate in a mass ratio of 5:2. (3) The collagen fiber mesh substrate is immersed in the modification solution, and the mass ratio of the collagen fiber mesh substrate to the modification solution is controlled to be 1:5. The immersion treatment is carried out for 10 hours at an immersion temperature of 40°C. After draining the water, the substrate is hot-pressed at a temperature of 50°C and a pressure of 0.3MPa for 15 minutes. After cooling, the skin-friendly leather for electronic skin is obtained.

[0030] Comparative Example 3 A method for preparing skin-friendly leather for electronic skin includes the following preparation steps: (1) The sheepskin was soaked in a 3% ammonium chloride aqueous solution at 25°C for 30 min, softened in a softening enzyme solution with a pH of 6.0 at 28°C for 4 h, tanned in an ionic liquid tanning liquor for 4 h at a tanning temperature of 35°C, washed with deionized water until neutral, and freeze-dried at -20°C for 5 h. The epidermal layer was removed by polishing to obtain a collagen fiber network base. The softening enzyme solution was composed of neutral protease, elastase, keratinase and deionized water in a mass ratio of 5:2:1:30. The ionic liquid tanning liquor was composed of 1-butyl-3-methylimidazolium chloride, citric acid, glycerol and deionized water in a mass ratio of 4:0.3:1:100. (2) Add the skin-friendly modifier to deionized water, and control the mass ratio of the skin-friendly modifier to deionized water to be 1:10. Use an ultrasonic power of 100W and an ultrasonic frequency of 40kHz to ultrasonically disperse for 10 minutes. Then add the conductive component and continue ultrasonic dispersion for 20 minutes to obtain the modified liquid. The conductive component is composed of graphene and polyaniline in a mass ratio of 1:3. The amount of conductive component added is 8% of the mass of the skin-friendly modifier. The preparation method of the skin-friendly modifier includes the following preparation steps: Hydroxypropyltrimethylammonium chloride chitosan was dispersed in deionized water, with the mass ratio of hydroxypropyltrimethylammonium chloride chitosan to deionized water controlled at 2:10. The pH was adjusted to 7.2, and the mixture was stirred at 200 rpm until homogeneous. Polyγ-glutamic acid was added, and the mixture was heated to 50°C and stirred for 20 min to obtain a mixed solution. Citric acid (2% of the total mass of the mixed solution) was added, and the mixture was stirred for another 10 min. The temperature was raised to 60°C, and a skin-friendly nonionic surfactant was added. The mixture was kept at this temperature for 3 h. After the reaction was completed, the mixture was transferred to a dialysis bag with a molecular weight cutoff of 20 kDa. After dialysis with deionized water for 24 h, the mixture was freeze-dried at -30°C for 10 h, pulverized, and passed through a 100-mesh sieve to obtain a skin-friendly modifier. The mass ratio of hydroxypropyltrimethylammonium chloride chitosan, polyγ-glutamic acid, and the skin-friendly nonionic surfactant was 4:2:1. The skin-friendly nonionic surfactant was polyglycerol-3 dioleate. (3) The collagen fiber mesh substrate is immersed in the modification solution, and the mass ratio of the collagen fiber mesh substrate to the modification solution is controlled to be 1:5. The immersion treatment is carried out for 10 hours at an immersion temperature of 40°C. After draining the water, the substrate is hot-pressed at a temperature of 50°C and a pressure of 0.3MPa for 15 minutes. After cooling, the skin-friendly leather for electronic skin is obtained.

[0031] Comparative Example 4 A method for preparing skin-friendly leather for electronic skin includes the following preparation steps: (1) The sheepskin was soaked in a 3% ammonium chloride aqueous solution at 25°C for 30 min, softened in a softening enzyme solution with a pH of 6.0 at 28°C for 4 h, tanned in an ionic liquid tanning liquor for 4 h at a tanning temperature of 35°C, washed with deionized water until neutral, and freeze-dried at -20°C for 5 h. The epidermal layer was removed by polishing to obtain a collagen fiber network base. The softening enzyme solution was composed of neutral protease, elastase, keratinase and deionized water in a mass ratio of 5:2:1:30. The ionic liquid tanning liquor was composed of 1-butyl-3-methylimidazolium chloride, citric acid, glycerol and deionized water in a mass ratio of 4:0.3:1:100. (2) Add the skin-friendly modifier to deionized water, and control the mass ratio of the skin-friendly modifier to deionized water to be 1:10. Use an ultrasonic power of 100W and an ultrasonic frequency of 40kHz to ultrasonically disperse for 10 minutes. Then add the conductive component and continue ultrasonic dispersion for 20 minutes to obtain the modified liquid. The conductive component is composed of graphene and polyaniline in a mass ratio of 1:3. The amount of conductive component added is 8% of the mass of the skin-friendly modifier. The preparation method of the skin-friendly modifier includes the following preparation steps: Hydroxypropyltrimethylammonium chloride chitosan was dispersed in deionized water, with the mass ratio of hydroxypropyltrimethylammonium chloride chitosan to deionized water controlled at 2:10. The pH was adjusted to 7.2, and the mixture was stirred at 200 rpm until homogeneous. Polyγ-glutamic acid was added, and the mixture was heated to 50°C and stirred for 20 min to obtain a mixed solution. Citric acid (2% of the total mass of the mixed solution) was added, and the mixture was stirred for another 10 min. The temperature was raised to 60°C, and a skin-friendly nonionic surfactant was added. The mixture was kept at this temperature for 3 h. After the reaction was completed, the mixture was transferred to a dialysis bag with a molecular weight cutoff of 20 kDa. After dialysis with deionized water for 24 h, the mixture was freeze-dried at -30°C for 10 h, pulverized, and passed through a 100-mesh sieve to obtain a skin-friendly modifier. The mass ratio of hydroxypropyltrimethylammonium chloride chitosan, polyγ-glutamic acid, and the skin-friendly nonionic surfactant was 4:2:1. The skin-friendly nonionic surfactant was polyglycerol-10 stearate. (3) The collagen fiber mesh substrate is immersed in the modification solution, and the mass ratio of the collagen fiber mesh substrate to the modification solution is controlled to be 1:5. The immersion treatment is carried out for 10 hours at an immersion temperature of 40°C. After draining the water, the substrate is hot-pressed at a temperature of 50°C and a pressure of 0.3MPa for 15 minutes. After cooling, the skin-friendly leather for electronic skin is obtained.

[0032] Comparative Example 5 A method for preparing skin-friendly leather for electronic skin includes the following preparation steps: (1) The sheepskin was soaked in a 3% ammonium chloride aqueous solution at 25°C for 30 min, softened in a softening enzyme solution with a pH of 6.0 at 28°C for 4 h, tanned in an ionic liquid tanning liquor for 4 h at a tanning temperature of 35°C, washed with deionized water until neutral, and freeze-dried at -20°C for 5 h. The epidermal layer was removed by polishing to obtain a collagen fiber network base. The softening enzyme solution was composed of neutral protease, elastase, keratinase and deionized water in a mass ratio of 5:2:1:30. The ionic liquid tanning liquor was composed of 1-butyl-3-methylimidazolium chloride, citric acid, glycerol and deionized water in a mass ratio of 4:0.3:1:100. (2) Add the skin-friendly modifier to deionized water, and control the mass ratio of the skin-friendly modifier to deionized water to be 1:10. Use an ultrasonic power of 100W and an ultrasonic frequency of 40kHz to ultrasonically disperse for 10 minutes. Then add the conductive component and continue ultrasonic dispersion for 20 minutes to obtain the modified liquid. The conductive component is composed of graphene and polyaniline in a mass ratio of 1:3. The amount of conductive component added is 20% of the mass of the skin-friendly modifier. The preparation method of the skin-friendly modifier includes the following preparation steps: Hydroxypropyltrimethylammonium chloride chitosan was dispersed in deionized water, with the mass ratio of hydroxypropyltrimethylammonium chloride chitosan to deionized water controlled at 2:10. The pH was adjusted to 7.2, and the mixture was stirred at 200 rpm until homogeneous. Polyγ-glutamic acid was added, and the mixture was heated to 50°C and stirred for 20 min to obtain a mixed solution. Citric acid (2% of the total mass of the mixed solution) was added, and the mixture was stirred for another 10 min. The temperature was raised to 60°C, and a skin-friendly nonionic surfactant was added. The mixture was kept at this temperature for 3 h. After the reaction was completed, the mixture was transferred to a dialysis bag with a molecular weight cutoff of 20 kDa. After dialysis with deionized water for 24 h, the mixture was freeze-dried at -30°C for 10 h, pulverized, and passed through a 100-mesh sieve to obtain a skin-friendly modifier. The mass ratio of hydroxypropyltrimethylammonium chloride chitosan, polyγ-glutamic acid, and the skin-friendly nonionic surfactant was 4:2:1. The skin-friendly nonionic surfactant was composed of polyglycerol-3 dioleate and polyglycerol-10 stearate in a mass ratio of 5:2. (3) The collagen fiber mesh substrate is immersed in the modification solution, and the mass ratio of the collagen fiber mesh substrate to the modification solution is controlled to be 1:5. The immersion treatment is carried out for 10 hours at an immersion temperature of 40°C. After draining the water, the substrate is hot-pressed at a temperature of 50°C and a pressure of 0.3MPa for 15 minutes. After cooling, the skin-friendly leather for electronic skin is obtained.

[0033] Performance testing The comprehensive performance of the skin-friendly leather for electronic skin prepared in Examples 1-3 and Comparative Examples 1-5 of this application was tested as follows: Air permeability: The test was conducted in accordance with the national standard GB / T 1037-2021 "Determination of water vapor permeability of plastic films and sheets - cup weight gain and weight loss method". The test environment temperature was controlled at 38℃ and the relative humidity at 90%. The water vapor permeability of the test sample was measured in g / (m²・24h). Softness: Using a professional hand feel scoring method, 5 experienced leather performance evaluators were selected to score the softness of the samples from Examples 1-3 and Comparative Examples 1-5 on a 5-point scale (scoring criteria: 5 points: extremely soft, fits the skin without any feeling of restriction; 4 points: soft, fits the skin without any obvious feeling of restriction; 3 points: relatively soft, slight feeling of restriction; 2 points: slightly stiff, with obvious feeling of restriction; 1 point: too stiff, cannot fit the skin). The average score of the 5 evaluators was taken as the final softness score of the sample. Surface resistivity: Tested in accordance with national standard GB / T 1410-2006 "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials"; Antibacterial properties: In accordance with the national standard GB / T 20944.3-2008 "Evaluation of antibacterial properties of textiles - Part 3: Shaking method", Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 6538) were selected as test strains for antibacterial testing. First, the 24-hour inhibition rate of the samples against the two strains was determined. Then, the samples were immersed in artificial sweat at 37°C for 7 days to simulate the skin-contact environment, and the 72-hour inhibition rate of the samples against Escherichia coli after immersion was determined. The specific test results are shown in Table 1.

[0034] Table 1 Performance parameters of skin-friendly leather for electronic skin prepared in Examples 1-3 and Comparative Examples 1-5 As shown in Table 1, the skin-friendly leather for electronic skin prepared in this application exhibits excellent comprehensive performance, combining outstanding skin-friendly softness, breathability, comfort, stable conductivity, and long-lasting antibacterial properties. This leather, relying on the loose structure of the collagen fiber network matrix and the synergistic effect of the skin-friendly modifier, has a soft touch and conforms well to human skin without significant restriction. The evenly distributed breathable channels allow for rapid conduction and dissipation of sweat, avoiding the stuffy and uncomfortable feeling caused by prolonged skin contact. The uniformly dispersed conductive components form a continuous conductive pathway, ensuring stable and controllable conductivity, meeting the electrical signal transmission requirements of electronic skin. It also demonstrates outstanding resistance to sweat erosion and long-lasting and stable antibacterial effects, providing reliable material support for the application of electronic skin in medical monitoring, smart wearables, and other fields.

[0035] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing skin-friendly leather for electronic skin, characterized in that, The preparation steps include the following: (1) The natural leather is soaked in deliming solution, softened by softening enzyme solution, tanned by ionic liquid tanning solution, washed until neutral, freeze-dried and then polished to remove the epidermis to obtain a collagen fiber network base. (2) Add the skin-friendly modifier to deionized water, ultrasonically disperse for 10-20 min, then add the conductive component, and continue ultrasonically disperse for 20-30 min to obtain the modified solution; (3) The collagen fiber mesh substrate is immersed in the modification liquid for impregnation treatment. After draining the water, it is hot-pressed and shaped. After cooling, the skin-friendly leather for electronic skin is obtained.

2. The method for preparing skin-friendly leather for electronic skin according to claim 1, characterized in that, In step (1), the deashing solution is an ammonium chloride aqueous solution with a mass concentration of 3-5% and a soaking temperature of 25-35℃.

3. The method for preparing skin-friendly leather for electronic skin according to claim 1, characterized in that, In step (1), the softening enzyme solution is composed of neutral protease, elastase, keratinase and deionized water in a mass ratio of 5-8:2-3:1-2:30-50; the pH value of the softening enzyme solution is 6.0-7.0; the softening treatment temperature is 28-38℃ and the treatment time is 4-6h.

4. The method for preparing skin-friendly leather for electronic skin according to claim 1, characterized in that, In step (1), the ionic liquid tanning liquor is composed of 1-butyl-3-methylimidazolium chloride, citric acid, glycerol and deionized water in a mass ratio of 4-6:0.3-0.5:1-2:100; the tanning temperature is 35-40℃.

5. The method for preparing skin-friendly leather for electronic skin according to claim 1, characterized in that, The preparation method of the skin-friendly modifier in step (2) includes the following preparation steps: Hydroxypropyltrimethylammonium chloride chitosan was dispersed in deionized water, the pH was adjusted to 7.2-7.5, and the mixture was stirred evenly. Polyγ-glutamic acid was added, the temperature was raised to 50-55℃, and the mixture was stirred for 20-30 minutes. Citric acid was added, and the mixture was stirred for another 10-20 minutes. The temperature was raised to 60-65℃, and a skin-friendly nonionic surfactant was added. The mixture was kept at this temperature for 3-4 hours. After the reaction was completed, the mixture was dialyzed with deionized water, freeze-dried, and pulverized to obtain a skin-friendly modifier.

6. The method for preparing skin-friendly leather for electronic skin according to claim 5, characterized in that, The mass ratio of the hydroxypropyltrimethylammonium chloride chitosan, polyγ-glutamic acid, and skin-friendly nonionic surfactant is 4-6:2-3:1-1.

5.

7. The method for preparing skin-friendly leather for electronic skin according to claim 5, characterized in that, The skin-friendly nonionic surfactant is composed of polyglycerol-3 dioleate and polyglycerol-10 stearate in a mass ratio of 5-8:2-4.

8. The method for preparing skin-friendly leather for electronic skin according to claim 1, characterized in that, In step (2), the conductive component is composed of graphene and polyaniline in a mass ratio of 1-2:3-5; the amount of the conductive component added is 8-12% of the mass of the skin-friendly modifier.

9. The method for preparing skin-friendly leather for electronic skin according to claim 1, characterized in that, In step (3), the hot pressing temperature is 50-60℃, the hot pressing pressure is 0.3-0.5MPa, and the hot pressing time is 15-20min.

10. A method for preparing skin-friendly leather for electronic skin according to any one of claims 1-9.

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