Lead-free piezoelectric ceramic fiber passive pressure heating electronic skin material and preparation method thereof

Abstract

The invention discloses a leadless piezoelectric ceramic fiber passive pressure heating electronic skin material and a preparation method thereof, and relates to the technical field of medical flexible electronics. The specific preparation method comprises the following steps: preparing a heating-sensor film from a chitosan solution A through a tape casting process; the upper surface of the heating-sensor film is coated with the chitosan solution B, the lower surface of the heating-sensor film is coated with the chitosan solution C, drying curing and sterilization treatment are conducted, and the electronic skin material is obtained; the material has high biocompatibility, the conductivity is improved to 10 <-3 > S / cm, the piezoelectric coefficient d33 is equal to 35 pC / N, the heating temperature is controlled to be 38-42 DEG C, the error is + / -0.4 DEG C, meanwhile, the degradation period is controlled to be adaptive to the wound healing period, and the material is good in skin friendliness and free of stimulation.

Description

Technical Field

[0001] This invention relates to the field of flexible electronic technology for medical applications, specifically to a lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material and its preparation method. Background Technology

[0002] With the development of bioelectronics and regenerative medicine, implantable or patch-like flexible electronic skin has shown great application potential in medical monitoring, wound healing, and postoperative hyperthermia. Among these, passive pressure-thermal electronic skin, which generates localized heat solely through mechanical pressure without requiring an external power source, is considered an ideal smart medical dressing due to its convenience and functionality. Such materials need to meet requirements of biocompatibility, biodegradability, and precise heating; however, current technologies still have the following challenges: Insufficient biocompatibility: Mainstream piezoelectric materials (such as PZT) contain lead and cannot be used for human implantation, and polymer substrates (such as PDMS) are non-degradable, requiring a second surgery for removal; Imbalance between conductivity and piezoelectric properties: Although bio-based materials (such as silk and starch) are degradable, their conductivity is less than 10. -5 S / cm, piezoelectric coefficient d 33 <10 pC / N, unable to support effective heating; low heating accuracy: medical application scenarios require local heat output of 38~42℃, and the temperature error of existing bio-based systems is more than ±1℃, which can easily lead to burns or ineffective heat therapy.

[0003] In existing technologies, bio-based electronic skin (such as silk / AgNWs system) has solved some compatibility issues, but AgNWs is expensive and non-degradable, while polylactic acid-based materials usually have a degradation cycle of several months or even years in the human body, which has problems such as long degradation time and difficulty in matching.

[0004] In summary, solving the above problems and developing a method for preparing lead-free piezoelectric ceramic fiber passive pressure-heated electronic skin material is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: The preparation method of lead-free piezoelectric ceramic fiber passive pressure-heated electronic skin material includes the following steps: preparing a heating-sensor film by casting a chitosan solution A; coating the upper surface of the heating-sensor film with chitosan solution B and the lower surface with chitosan solution C; drying and curing; sterilization treatment to obtain the electronic skin material. The chitosan solution A has a solid content of 5-8 wt% and includes the following raw materials, by mass: 60-70 parts chitosan, 5-10 parts carbon-based conductive modifier, 20-30 parts lead-free piezoelectric ceramic nanofibers; the solvent is a 0.5-2 wt% aqueous solution of acetic acid. The chitosan solution B has a solid content of 1-5 wt% and includes the following raw materials: chitosan; the solvent is a 0.5-2 wt% aqueous acetic acid solution; The chitosan solution C has a solid content of 3-5 wt% and includes the following raw materials, by mass: 60-70 parts chitosan, 30-40 parts starch; the solvent is a 0.5-2 wt% aqueous solution of acetic acid.

[0007] Preferably, the lead-free piezoelectric ceramic nanofibers are prepared by electrospinning; the raw materials for the lead-free piezoelectric ceramic nanofibers include polylactic acid, polylactic acid-polyethylene glycol block copolymer, and barium titanate nanoparticles in a mass ratio of 80:20~25:7~9.

[0008] More preferably, the polylactic acid-polyethylene glycol block copolymer comprises mPEG-b-PLLA and mPEG-b-PDLA in a mass ratio of 0.6 to 1:1; The mPEG-b-PLLA was obtained by ring-opening polymerization of methoxy polyethylene glycol A and L-lactide. The mPEG-b-PDLA was obtained by ring-opening polymerization of methoxy polyethylene glycol B and D-lactide.

[0009] Preferably, the raw materials for mPEG-b-PLLA include methoxy polyethylene glycol A and L-lactide in a mass ratio of 1:0.45~0.55; the molecular weight of methoxy polyethylene glycol A is 2000. The raw materials for mPEG-b-PDLA include methoxy polyethylene glycol B and D-lactide in a mass ratio of 1:0.43~0.53; the molecular weight of methoxy polyethylene glycol B is 3000.

[0010] Preferably, the particle size of the nano-barium titanate is 30~50nm.

[0011] Preferred lead-free piezoelectric ceramic nanofibers have an aspect ratio of 20-35:1 and a diameter of 100-300 nm.

[0012] Preferably, the carbon-based conductive modifier is obtained by modifying carbon nanofibers with dopamine; the mass ratio of carbon nanofibers to dopamine is 1:0.05~0.1.

[0013] Preferably, the degree of deacetylation of the chitosan is 85-90%.

[0014] Preferably, the sterilization process uses gamma rays at a dose of 20-25 kGy.

[0015] The adhesive layer uses a pure chitosan film with a thickness controlled at 5~8μm, which has good skin affinity and a fit to human tissue of ≥95%. The degradation cycle can be controlled by the degree of deacetylation of chitosan. In the thermal-sensing layer, chitosan serves as the matrix, lead-free piezoelectric ceramic nanofibers provide piezoelectric properties, and carbon-based conductive modifiers form a conductive network to improve conductivity. The substrate support layer uses a chitosan-starch composite film with a thickness of 10~15μm to improve the flexibility of the substrate.

[0016] After all layers are bonded, they are sterilized with gamma rays (dose 20~25kGy). During the sterilization process, although gamma rays mainly act on microorganisms, they also slightly promote the cross-linking between chitosan molecules, further enhancing the interlayer bonding strength, while ensuring the sterility of the material and meeting the requirements for medical implantation / application.

[0017] The working principle of this invention is as follows: the pressure generated by human activities (such as gait and wound pressing) deforms the lead-free piezoelectric ceramic nanofibers, generating a piezoelectric potential; a carbon-based conductive modifier forms a conductive network, converting electrical energy into Joule heat to achieve passive pressure heating; and the chitosan and starch used are naturally degraded into small molecules, eliminating the need for secondary removal; the electronic skin prepared by this invention has passed ISO10993 biocompatibility certification, is lead-free and non-irritating, and is suitable for medical implantation / application scenarios such as wound healing and prosthetic rehabilitation, as well as pressure-heated toys, cushions, and other scenarios suitable for pressure heating and warmth preservation.

[0018] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: This invention uses a pure chitosan film as the application layer, and prepares a thermal-sensing layer using chitosan, lead-free piezoelectric ceramic nanofibers, and a carbon-based conductive modifier; a substrate support layer is prepared using a composite of chitosan and starch, thereby obtaining a lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material with high biocompatibility and improved conductivity to 10. -3 S / cm, piezoelectric coefficient d 33 =35 pC / N, heating temperature controlled at 38~42℃ with an error of ±0.4℃, while controlling the degradation cycle to match the wound healing cycle, good skin-friendliness and no irritation.

[0019] Lead-free piezoelectric ceramic nanofibers were prepared via electrospinning. The spinning solution used polylactic acid (PLA) as the main matrix, polyethylene glycol (PEG)-PLA block copolymer as a modifier, and barium titanate nanofibers as the piezoelectric material. PEG possesses excellent biocompatibility, which can improve the flexibility and spinnability of PLA-based lead-free piezoelectric ceramic nanofibers. It can also enhance interfacial compatibility and degradation controllability with chitosan. By preparing them as block copolymers, hydrophilic PEG can be introduced into the hydrophobic segments of PLA, strengthening the interfacial bonding with barium titanate nanofibers. Simultaneously, the hydrophilic groups regulate the fiber degradation rate to match the wound healing cycle.

[0020] This invention utilizes mPEG-b-PLLA and mPEG-b-PDLA as a compound of polyethylene glycol polylactic acid block copolymers. mPEG-b-PLLA, with a molecular weight of 2000 and PLLA blocks with a DP of 12-15, exhibits a faster degradation rate, preferentially hydrolyzing within the fiber to form nanoscale channels and guiding initial material degradation. Meanwhile, mPEG-b-PDLA, with a molecular weight of 3000 and PDLA blocks with a DP of 18-22, increases chain entanglement. The PDLA blocks can form stereocomposite microcrystalline regions with the PLLA blocks, providing moderate support and compensating for the initial integrity of the fiber's mechanical properties. This provides a stable stress transfer basis for the piezoelectric effect and improves the accuracy of heating. By compounding the two at a specific mass ratio of 0.6-1:1, a good synergistic effect is achieved, maintaining excellent piezoelectric properties (d... 33 While maintaining a thermal accuracy of 35 pC / N and a thermal precision of ±0.4℃, it can ensure that the overall degradation cycle is precisely controlled within an ideal window, matching the wound healing cycle, without the need for secondary removal. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the following quantities are by weight. There are no special restrictions on the manufacturers of the raw materials involved in this invention. Exemplary components include: chitosan, with a molecular weight of 15 kDa; carbon nanofibers: with a diameter of 200 nm and a length of 5-10 μm; polylactic acid (PLAA), with a molecular weight of 28,000; barium titanate nanoparticles, with a particle size of 50 nm; L-lactide CAS number: 4511-42-6; D-lactide CAS number: 13076-17-0. In the following examples, parts are by weight, and all raw materials mentioned above and others not mentioned are commercially available; wherein the acetic acid concentration in the chitosan acetic acid aqueous solution is 1 wt%.

[0024] Pre-preparation: Preparation of mPEG-b-PLLA: Under an argon atmosphere, L-lactide, anhydrous toluene, methoxy polyethylene glycol A, and stannous octoate were mixed evenly and stirred at 120°C for 24 h. Dichloromethane was added and mixed evenly. The mixture was precipitated with anhydrous diethyl ether, washed, filtered, and dried to obtain mPEG-b-PLLA. The raw materials for mPEG-b-PLLA included methoxy polyethylene glycol A and L-lactide in a mass ratio of 1:0.5. The molecular weight of the methoxy polyethylene glycol A was 2000.

[0025] Preparation of mPEG-b-PDLA: Under an argon atmosphere, D-lactide, anhydrous toluene, methoxy polyethylene glycol A, and stannous octoate were mixed evenly and stirred at 120°C for 24 h. Dichloromethane was added and mixed evenly. The mixture was precipitated with anhydrous diethyl ether, washed, filtered, and dried to obtain mPEG-b-PDLA. The raw materials for mPEG-b-PDLA included methoxy polyethylene glycol B and D-lactide in a mass ratio of 1:0.48. The molecular weight of methoxy polyethylene glycol B was 3000.

[0026] Preparation of lead-free piezoelectric ceramic nanofibers: mPEG-b-PLLA and mPEG-b-PDLA were uniformly mixed to obtain a polylactic acid-polyethylene glycol block copolymer; polylactic acid, polyethylene glycol, barium titanate, and the polylactic acid-polyethylene glycol block copolymer were added to dimethylformamide and ultrasonically dispersed to obtain an electrospinning solution. Lead-free piezoelectric ceramic nanofibers were prepared by electrospinning. During the electrospinning process, the solvent of the spinning solution was a dichloromethane / dimethylformamide mixed solvent with a volume ratio of 4:1, the flow rate of the spinning solution was 15 mL / h, and the electric field was 1 kV / cm. After obtaining the product, it was homogenized to obtain the product with the corresponding aspect ratio. The raw materials of the lead-free piezoelectric ceramic nanofibers included polylactic acid, polylactic acid-polyethylene glycol block copolymer, and nano-barium titanate in a mass ratio of 80:22:8; the polylactic acid-polyethylene glycol block copolymer included mPEG-b-PLLA and mPEG-b-PDLA in a mass ratio of 0.8:1.

[0027] Preparation of carbon-based conductive modifier: Prepare a 2 g / L dopamine-Tris buffer solution (pH 8.5), remove surface impurities from carbon fibers with acetone, add them to the dopamine-Tris buffer solution, stir at 25°C for 16 h, wash, and dry to obtain the carbon-based conductive modifier; wherein, the mass ratio of nano-carbon fibers to dopamine is 1:0.05.

[0028] Example 1: The preparation method of lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material includes the following steps: S1: A thermal-sensor film was prepared by casting chitosan solution A and vacuum-dried at 60℃ for 1 hour to obtain electronic skin material A with a thickness of 35μm. The solid content of chitosan solution A was 8wt%, and it included the following raw materials by mass: 65 parts chitosan, 8 parts carbon-based conductive modifier, and 27 parts lead-free piezoelectric ceramic nanofibers; the solvent was a 1wt% aqueous solution of acetic acid (diameter 200nm, aspect ratio 25:1). S2: Coat one side of electronic skin material A with chitosan solution B, dry at 50°C for 30 min to form an 8 μm thick adhesive layer, thus obtaining electronic skin material B; wherein, the solid content of chitosan solution B is 5 wt%, including the following raw materials: chitosan; the solvent is 1 wt% aqueous acetic acid solution; S3: Chitosan solution C is coated onto one side of the electronic skin material B, which is then dried and cured at 60°C to form a 12μm thick base support layer. The layer is then sterilized with gamma rays (dose 25kGy) to obtain the electronic skin material. The chitosan solution C has a solid content of 5wt% and comprises the following raw materials by mass: 65 parts chitosan, 35 parts starch; the solvent is a 1wt% aqueous solution of acetic acid. The degree of deacetylation of chitosan is 88%.

[0029] Comparative Example 1: Based on Example 1, mPEG-b-PLLA modification was used alone, with the other processes remaining unchanged, as follows: S1: A thermal-sensor film was prepared by casting chitosan solution A and vacuum-dried at 60℃ for 1 hour to obtain electronic skin material A with a thickness of 35μm. The solid content of chitosan solution A was 8wt%, and it included the following raw materials by mass: 65 parts chitosan, 8 parts carbon-based conductive modifier, and 27 parts lead-free piezoelectric ceramic nanofibers; the solvent was a 1wt% aqueous solution of acetic acid (diameter 200nm, aspect ratio 25:1). S2: Coat one side of electronic skin material A with chitosan solution B, dry at 50°C for 30 min to form an 8 μm thick adhesive layer, thus obtaining electronic skin material B; wherein, the solid content of chitosan solution B is 5 wt%, including the following raw materials: chitosan; the solvent is 1 wt% aqueous acetic acid solution; S3: Chitosan solution C is coated onto one side of the electronic skin material B, which is then dried and cured at 60°C to form a 12μm thick base support layer. The layer is then sterilized with gamma rays (dose 25kGy) to obtain the electronic skin material. The chitosan solution C has a solid content of 5wt% and comprises the following raw materials by mass: 65 parts chitosan, 35 parts starch; the solvent is a 1wt% aqueous solution of acetic acid. The degree of deacetylation of chitosan is 88%.

[0030] The preparation method of lead-free piezoelectric ceramic nanofibers is as follows: mPEG-b-PLLA is used as a polylactic acid-polyethylene glycol block copolymer; polylactic acid, polyethylene glycol, barium titanate, and polylactic acid-polyethylene glycol block copolymer are added to dimethylformamide and ultrasonically dispersed evenly to obtain an electrospinning solution. Lead-free piezoelectric ceramic nanofibers are prepared by electrospinning. During the electrospinning process, the solvent of the spinning solution is a dichloromethane / dimethylformamide mixed solvent with a volume ratio of 4:1, the flow rate of the spinning solution is 15 mL / h, and the electric field is 1 kV / cm. After obtaining the product, it is homogenized to obtain the product with the corresponding aspect ratio. The raw materials of lead-free piezoelectric ceramic nanofibers include polylactic acid, polylactic acid-polyethylene glycol block copolymer, and nano-barium titanate in a mass ratio of 80:22:8; the polylactic acid-polyethylene glycol block copolymer includes mPEG-b-PLLA.

[0031] Comparative Example 2: Based on Example 1, mPEG-b-PDLA modification was used alone, with the other processes remaining unchanged, as follows: S1: A thermal-sensor film was prepared by casting chitosan solution A and vacuum-dried at 60℃ for 1 hour to obtain electronic skin material A with a thickness of 35μm. The solid content of chitosan solution A was 8wt%, and it included the following raw materials by mass: 65 parts chitosan, 8 parts carbon-based conductive modifier, and 27 parts lead-free piezoelectric ceramic nanofibers; the solvent was a 1wt% aqueous solution of acetic acid (diameter 200nm, aspect ratio 25:1). S2: Coat one side of electronic skin material A with chitosan solution B, dry at 50°C for 30 min to form an 8 μm thick adhesive layer, thus obtaining electronic skin material B; wherein, the solid content of chitosan solution B is 5 wt%, including the following raw materials: chitosan; the solvent is 1 wt% aqueous acetic acid solution; S3: Chitosan solution C is coated onto one side of the electronic skin material B, which is then dried and cured at 60°C to form a 12μm thick base support layer. The layer is then sterilized with gamma rays (dose 25kGy) to obtain the electronic skin material. The chitosan solution C has a solid content of 5wt% and comprises the following raw materials by mass: 65 parts chitosan, 35 parts starch; the solvent is a 1wt% aqueous solution of acetic acid. The degree of deacetylation of chitosan is 88%.

[0032] The preparation method of lead-free piezoelectric ceramic nanofibers is as follows: mPEG-b-PDLA is used as a polylactic acid-polyethylene glycol block copolymer; polylactic acid, polyethylene glycol, barium titanate, and polylactic acid-polyethylene glycol block copolymer are added to dimethylformamide and ultrasonically dispersed evenly to obtain an electrospinning solution. Lead-free piezoelectric ceramic nanofibers are prepared by electrospinning. During the electrospinning process, the solvent of the spinning solution is a dichloromethane / dimethylformamide mixed solvent with a volume ratio of 4:1, the flow rate of the spinning solution is 15 mL / h, and the electric field is 1 kV / cm. After obtaining the product, it is homogenized to obtain the product with the corresponding aspect ratio. The raw materials of lead-free piezoelectric ceramic nanofibers include polylactic acid, polylactic acid-polyethylene glycol block copolymer, and nano-barium titanate in a mass ratio of 80:22:8; the polylactic acid-polyethylene glycol block copolymer includes mPEG-b-PDLA.

[0033] Comparative Example 3: Based on Example 1, the mass ratio of mPEG-b-PLLA and mPEG-b-PDLA was exchanged. The remaining processes remained unchanged, as follows: S1: A thermal-sensor film was prepared by casting chitosan solution A and vacuum-dried at 60℃ for 1 hour to obtain electronic skin material A with a thickness of 35μm. The solid content of chitosan solution A was 8wt%, and it included the following raw materials by mass: 65 parts chitosan, 8 parts carbon-based conductive modifier, and 27 parts lead-free piezoelectric ceramic nanofibers; the solvent was a 1wt% aqueous solution of acetic acid (diameter 200nm, aspect ratio 25:1). S2: Coat one side of electronic skin material A with chitosan solution B, dry at 50°C for 30 min to form an 8 μm thick adhesive layer, thus obtaining electronic skin material B; wherein, the solid content of chitosan solution B is 5 wt%, including the following raw materials: chitosan; the solvent is 1 wt% aqueous acetic acid solution; S3: Chitosan solution C is coated onto one side of the electronic skin material B, which is then dried and cured at 60°C to form a 12μm thick base support layer. The layer is then sterilized with gamma rays (dose 25kGy) to obtain the electronic skin material. The chitosan solution C has a solid content of 5wt% and comprises the following raw materials by mass: 65 parts chitosan, 35 parts starch; the solvent is a 1wt% aqueous solution of acetic acid. The degree of deacetylation of chitosan is 88%.

[0034] The preparation method of lead-free piezoelectric ceramic nanofibers is as follows: mPEG-b-PLLA and mPEG-b-PDLA are mixed evenly to obtain polylactic acid-polyethylene glycol block copolymer; polylactic acid, polyethylene glycol, barium titanate, and polylactic acid-polyethylene glycol block copolymer are added to dimethylformamide and ultrasonically dispersed evenly to obtain an electrospinning solution; lead-free piezoelectric ceramic nanofibers are prepared by electrospinning process. During the electrospinning process, the solvent of the spinning solution is a dichloromethane / dimethylformamide mixed solvent with a volume ratio of 4:1, the flow rate of the spinning solution is 15mL / h, the electric field is 1kV / cm, and the product is homogenized to obtain the product with the corresponding aspect ratio; the raw materials of lead-free piezoelectric ceramic nanofibers include polylactic acid, polylactic acid-polyethylene glycol block copolymer, and nano-barium titanate in a mass ratio of 80:22:8; the polylactic acid-polyethylene glycol block copolymer includes mPEG-b-PLLA and mPEG-b-PDLA in a mass ratio of 1:0.8.

[0035] Performance testing: (1) The heating temperature generated by each example and comparative sample under a working pressure of 0.5 kPa was measured; (2) The samples prepared in Example 1 and each comparative sample were implanted under the skin of rats to test the degradation time. The sample size was 20×20 mm and the test period was 2 weeks; (3) The elongation at break of each example and comparative sample was measured. The stretching rate was 20 mm / min; The experimental data are shown in Table 1.

[0036] Table 1

[0037] As shown in Table 1, Comparative Example 1, using only mPEG-b-PLLA modification, lacks the mechanical support of the PDLA stereocomposite crystal region, resulting in unstable stress transmission in the piezoelectric fiber network, decreased heating temperature and accuracy, and shorter PLLA block DP values, making ester bonds more prone to hydrolysis and increasing degradation rate. Comparative Example 2, using only mPEG-b-PDLA modification, forms overly stable stereocrystals and chain entanglements, significantly decreasing the degradation rate, reducing pressure response sensitivity, and causing unstable heating temperature. Comparative Example 3, by exchanging the mass ratio of mPEG-b-PLLA to mPEG-b-PDLA, increases the PLLA proportion, reduces the optimal density of the PDLA stereocomposite crystal region, and decreases heating stability.

[0038] Application Example 1: Basic Wound Healing Type: The preparation method of lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material includes the following steps: S1: A thermal-sensor film was prepared by casting chitosan solution A and vacuum-dried at 60℃ for 1 hour to obtain electronic skin material A with a thickness of 35μm. The solid content of chitosan solution A was 8wt%, and it included the following raw materials by mass: 65 parts chitosan, 8 parts carbon-based conductive modifier, and 27 parts lead-free piezoelectric ceramic nanofibers; the solvent was a 1wt% aqueous solution of acetic acid (diameter 200nm, aspect ratio 25:1). S2: Coat one side of electronic skin material A with chitosan solution B, dry at 50°C for 30 min to form an 8 μm thick adhesive layer, thus obtaining electronic skin material B; wherein, the solid content of chitosan solution B is 5 wt%, including the following raw materials: chitosan; the solvent is 1 wt% aqueous acetic acid solution; S3: Chitosan solution C is coated onto one side of the electronic skin material B, which is then dried and cured at 60°C to form a 12μm thick base support layer. The layer is then sterilized with gamma rays (dose 25kGy) to obtain the electronic skin material. The chitosan solution C has a solid content of 5wt% and comprises the following raw materials by mass: 65 parts chitosan, 35 parts starch; the solvent is a 1wt% aqueous solution of acetic acid. The degree of deacetylation of chitosan is 88%.

[0039] Application Example 2: Long-lasting chronic wound treatment: The preparation method of a lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material includes the following steps: S1: A thermal-sensor film was prepared by casting chitosan solution A and vacuum dried at 60℃ for 1 h to obtain electronic skin material A with a thickness of 35 μm; wherein, the solid content of chitosan solution A is 8 wt%, including the following raw materials by mass parts: 70 parts chitosan, 5 parts carbon-based conductive modifier, 25 parts lead-free piezoelectric ceramic nanofibers (diameter of 200 nm, aspect ratio of 30:1); the solvent is 1 wt% aqueous acetic acid solution; S2: Coat one side of electronic skin material A with chitosan solution B, dry at 50°C for 30 min to form an 8 μm thick adhesive layer, thus obtaining electronic skin material B; wherein, the solid content of chitosan solution B is 5 wt%, including the following raw materials: chitosan; the solvent is 1 wt% aqueous acetic acid solution; S3: Chitosan solution C is coated onto one side of the electronic skin material B, which is then dried and cured at 60°C to form a 15μm thick base support layer. The layer is then sterilized with gamma rays (dose 25kGy) to obtain the electronic skin material. The chitosan solution C has a solid content of 5wt% and includes the following raw materials by mass: 68 parts chitosan, 30 parts starch; the solvent is a 1wt% aqueous acetic acid solution. The degree of deacetylation of chitosan is 90%; 2 wt% glycerol also needs to be added to chitosan solution C.

[0040] Application Example 3: Prosthetic Rehabilitation Type (High Conductivity): The preparation method of lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material includes the following steps: S1: A thermal-sensor film was prepared by casting chitosan solution A and vacuum dried at 60℃ for 1 h to obtain electronic skin material A with a thickness of 35 μm; wherein, the solid content of chitosan solution A is 8 wt%, including the following raw materials, by mass parts: 60 parts chitosan, 10 parts carbon-based conductive modifier, 30 parts lead-free piezoelectric ceramic nanofibers (diameter of 250 nm, aspect ratio of 20:1); the solvent is 1 wt% aqueous acetic acid solution; S2: Coat one side of electronic skin material A with chitosan solution B, dry at 50°C for 30 min to form an adhesive layer with a thickness of 5 μm, and obtain electronic skin material B; wherein, the solid content of chitosan solution B is 5 wt%, including the following raw materials: chitosan; the solvent is 1 wt% aqueous acetic acid solution; S3: Chitosan solution C is coated onto one side of the electronic skin material B, which is then dried and cured at 60°C to form a 10μm thick base support layer. The layer is then sterilized with gamma rays (dose 25kGy) to obtain the electronic skin material. The chitosan solution C has a solid content of 5wt% and includes the following raw materials by mass: 60 parts chitosan, 40 parts starch; the solvent is a 1wt% aqueous solution of acetic acid. The degree of deacetylation of chitosan is 85%; 1 wt% hyaluronic acid also needs to be added to chitosan solution B.

[0041] Application Example 4: High Voltage Type (Low Pressure): The preparation method of lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material includes the following steps: S1: A thermal-sensor film was prepared by casting chitosan solution A and then freeze-dried at -40℃ for 24 h to obtain electronic skin material A with a thickness of 35 μm. The solid content of chitosan solution A was 8 wt%, and it included the following raw materials by mass: 65 parts chitosan, 7 parts carbon-based conductive modifier, 28 parts lead-free piezoelectric ceramic nanofibers (diameter 200 nm, aspect ratio 35:1); the solvent was 1 wt% aqueous acetic acid solution. S2: Coat one side of electronic skin material A with chitosan solution B, dry at 50°C for 30 min to form an adhesive layer with a thickness of 6 μm, and obtain electronic skin material B; wherein, the solid content of chitosan solution B is 5 wt%, including the following raw materials: chitosan; the solvent is 1 wt% aqueous acetic acid solution; S3: Chitosan solution C is coated onto one side of the electronic skin material B, which is then dried and cured at 60°C to form a 12μm thick base support layer. The layer is then sterilized with gamma rays (dose 25kGy) to obtain the electronic skin material. The chitosan solution C has a solid content of 5wt% and comprises the following raw materials by mass: 65 parts chitosan, 35 parts starch; the solvent is a 1wt% aqueous solution of acetic acid. The degree of deacetylation of chitosan is 88%.

[0042] Application Example 5: Joint Adaptive Type (High Flexibility): The preparation method of lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material includes the following steps: S1: A thermal-sensor film was prepared by casting chitosan solution A and vacuum dried at 60℃ for 1 h to obtain electronic skin material A with a thickness of 35 μm; wherein, the solid content of chitosan solution A is 8 wt%, including the following raw materials by mass parts: 62 parts chitosan, 8 parts carbon-based conductive modifier, 30 parts lead-free piezoelectric ceramic nanofibers (diameter of 150 nm, aspect ratio of 25:1); the solvent is 1 wt% aqueous acetic acid solution; S2: Coat one side of electronic skin material A with chitosan solution B, dry at 50°C for 30 min to form an adhesive layer with a thickness of 5 μm, and obtain electronic skin material B; wherein, the solid content of chitosan solution B is 5 wt%, including the following raw materials: chitosan; the solvent is 1 wt% aqueous acetic acid solution; S3: Chitosan solution C is coated onto one side of the electronic skin material B, which is then dried and cured at 60°C to form a 12μm thick base support layer. The layer is then subjected to 0.2MPa roller pressing for 30 minutes and sterilized with γ-rays (dose 25kGy) to obtain the electronic skin material. The chitosan solution C has a solid content of 5wt% and includes the following raw materials by mass: 60 parts chitosan, 40 parts starch; the solvent is a 1wt% aqueous solution of acetic acid. The degree of deacetylation of chitosan is 85%; 3wt% PEG-400 needs to be added to chitosan solution B; 5wt% elastin (extracted from fish skin) needs to be added to chitosan solution C.

[0043] Application Example 6: Minimally Invasive Surgical Type (Ultra-Thin): The preparation method of lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material includes the following steps: S1: A thermal-sensor film was prepared by casting chitosan solution A and vacuum dried at 60℃ for 1 h to obtain electronic skin material A with a thickness of 35 μm; wherein, the solid content of chitosan solution A is 8 wt%, including the following raw materials, by mass parts: 68 parts chitosan, 7 parts carbon-based conductive modifier, 25 parts lead-free piezoelectric ceramic nanofibers (diameter of 100 nm, aspect ratio of 25:1); the solvent is 1 wt% aqueous acetic acid solution; S2: Chitosan solution B is coated onto one slit of electronic skin material A and dried at 50°C for 30 min to form an adhesive layer with a thickness of 3 μm, thus obtaining electronic skin material B; wherein, the solid content of chitosan solution B is 5 wt%, and it includes the following raw materials: chitosan; the solvent is 1 wt% aqueous acetic acid solution; S3: Chitosan solution C is coated on one side of the adhesive layer of electronic skin material B, and freeze-dried at -50℃ for 36 hours to form a base support layer with a thickness of 8μm. The layer is then sterilized with γ-rays (dose 25kGy) to obtain the electronic skin material. The chitosan solution C has a solid content of 5wt% and includes the following raw materials by mass: 65 parts chitosan, 35 parts starch; the solvent is a 1wt% aqueous solution of acetic acid. The degree of deacetylation of chitosan is 90%.

[0044] Performance Testing: The performance tests for each application example are shown in Table 2 below: Table 2

[0045] As shown in Table 2, Application Example 2 extends the degradation cycle by increasing the degree of deacetylation of chitosan and reduces the degradation of chitosan by lowering the drying temperature of the heat-sensing layer. Glycerin is added to the base support layer to improve flexibility and meet the long-term effect of chronic wounds. Application Example 3 uses lead-free piezoelectric ceramic nanofibers with larger diameters and increases the starch content in the base support layer. Hyaluronic acid is added to the patch layer to increase elasticity and meet the requirement of high conductivity. Application Example 4 uses lead-free piezoelectric ceramic nanofibers with high aspect ratio and uses freeze-drying instead of conventional drying to retain the porous structure, thus adapting to low-pressure scenarios. Application Example 5 adds PEG-400 to the patch layer to improve flexibility, adds elastin (extracted from fish skin) to the base layer, and adds a rolling process to enhance interfacial bonding to meet the characteristics of high flexibility and non-delamination. Application Example 6 reduces the thickness of each layer, uses lead-free piezoelectric ceramic nanofibers with low diameters, and uses vacuum freeze-drying to ensure the integrity of the thin-layer structure to meet the requirements of ultra-thinness. Conclusion: The lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material prepared in this invention has high biocompatibility and its conductivity is improved to 10. -3 S / cm, piezoelectric coefficient d 33=35 pC / N, heating temperature controlled at 38~42℃ with an error of ±0.4℃, while controlling the degradation cycle to match the wound healing cycle, good skin-friendliness and no irritation.

[0046] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material, characterized in that: Includes the following steps: A thermal-sensor film was prepared by casting a chitosan solution A; chitosan solution B was coated on the upper surface of the thermal-sensor film and chitosan solution C was coated on the lower surface; the film was dried, cured, and sterilized to obtain an electronic skin material. The chitosan solution A has a solid content of 5-8 wt% and includes the following raw materials, by mass: 60-70 parts chitosan, 5-10 parts carbon-based conductive modifier, 20-30 parts lead-free piezoelectric ceramic nanofibers; the solvent is a 0.5-2 wt% aqueous solution of acetic acid. The solid content of the chitosan solution B is 1~5wt%, and it includes the following raw material: chitosan; The solvent is an aqueous solution of acetic acid with a concentration of 0.5~2wt%; The chitosan solution C has a solid content of 3-5 wt% and includes the following raw materials, by mass: 60-70 parts chitosan, 30-40 parts starch; the solvent is a 0.5-2 wt% aqueous solution of acetic acid.

2. The method for preparing the lead-free piezoelectric ceramic fiber passive pressure-heated electronic skin material according to claim 1, characterized in that: The lead-free piezoelectric ceramic nanofibers are prepared by electrospinning. The raw materials for the lead-free piezoelectric ceramic nanofibers include polylactic acid, polylactic acid-polyethylene glycol block copolymer, and barium titanate nanoparticles in a mass ratio of 80:20~25:7~9.

3. The method for preparing the lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material according to claim 2, characterized in that: The polylactic acid-polyethylene glycol block copolymer comprises mPEG-b-PLLA and mPEG-b-PDLA in a mass ratio of 0.6 to 1:1; The mPEG-b-PLLA was obtained by ring-opening polymerization of methoxy polyethylene glycol A and L-lactide. The mPEG-b-PDLA was obtained by ring-opening polymerization of methoxy polyethylene glycol B and D-lactide.

4. The method for preparing the lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material according to claim 3, characterized in that: The raw materials for mPEG-b-PLLA include methoxy polyethylene glycol A and L-lactide in a mass ratio of 1:0.45~0.55; the molecular weight of methoxy polyethylene glycol A is 2000. The raw materials for mPEG-b-PDLA include methoxy polyethylene glycol B and D-lactide in a mass ratio of 1:0.43~0.53; the molecular weight of methoxy polyethylene glycol B is 3000.

5. The method for preparing the lead-free piezoelectric ceramic fiber passive pressure-heated electronic skin material according to claim 2, characterized in that: The particle size of the nano-barium titanate is 30~50nm.

6. The method for preparing the lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material according to claim 1, characterized in that: The lead-free piezoelectric ceramic nanofibers have an aspect ratio of 20~35:1 and a diameter of 100~300nm.

7. The method for preparing the lead-free piezoelectric ceramic fiber passive pressure-thermal electronic skin material according to claim 1, characterized in that: The carbon-based conductive modifier is obtained by modifying carbon nanofibers with dopamine; The mass ratio of carbon nanofibers to dopamine is 1:0.05~0.

1.

8. The method for preparing the lead-free piezoelectric ceramic fiber passive pressure-heated electronic skin material according to claim 1, characterized in that: The degree of deacetylation of the chitosan is 85-90%.

9. The method for preparing the lead-free piezoelectric ceramic fiber passive pressure-heated electronic skin material according to claim 1, characterized in that: During the sterilization process, gamma rays are used at a dose of 20-25 kGy.

10. The electronic skin material prepared by the method for preparing lead-free piezoelectric ceramic fiber passive pressure-heated electronic skin material according to any one of claims 1 to 9.

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