Silk fibroin conductive film material and its thermal temperature assisted peeling process

Abstract

This invention relates to a silk fibroin conductive thin film material and its heat-assisted peeling process. The silk fibroin conductive thin film material is mainly composed of a substrate layer and a conductive layer. The substrate layer is made of silk fibroin film material, and the conductive layer is made of PEDOT or its derivatives. The substrate layer and the conductive layer are bonded together through intermolecular entanglement. The heat-assisted peeling process for the silk fibroin conductive thin film material is as follows: a silk fibroin solution is poured onto a substrate with the conductive material attached, and the solution is dried at a constant temperature. Then, the film composed of silk fibroin and conductive material is peeled off from the substrate to obtain the silk fibroin conductive thin film material. The conductive layer and the substrate layer of the silk fibroin conductive thin film material of this invention are firmly bonded, and the conductivity is good. The heat-assisted peeling process of this invention is simple and time-saving.

Description

Technical Field

[0001] This invention belongs to the field of polymer material processing and molding technology, and relates to a silk fibroin conductive film material and its heat-assisted peeling process. Background Technology

[0002] Silk fibroin, derived from silkworm silk fibers, possesses excellent biocompatibility and mechanical flexibility, making it a potential natural polymer for manufacturing bioelectronic devices and biomedical materials. However, due to its inherently poor conductivity, silk fibroin typically needs to be compounded with other metal ions or conductive polymers to improve its electrical signal conduction or sensing performance. Silk fibroin materials with good conductivity can serve as interface materials between neural tissue and external devices, enabling electrical signals between tissues and external devices. They show promising applications in constructing neural interfaces, neural stimulation electrodes, bioelectrically active interfaces, and neural tissue repair scaffolds for neurophysiological research.

[0003] To date, modification methods to improve the conductivity of silk fibroin materials mainly include composite inorganic materials (such as graphene and carbon nanotubes), metallic materials (such as gold nanoparticles and silver nanowires), and conductive polymer materials (such as polypyrrole, polyaniline, and PEDOT). Compared with traditional composite inorganic and metallic materials, conductive polymer materials have superior biocompatibility and mechanical flexibility. The silk fibroin films prepared from these materials are more suitable for long-term implantable bioelectronic devices and tissue repair scaffolds. Therefore, the modification of silk fibroin with conductive polymer materials has attracted widespread attention, provided that the conductivity can be effectively improved without excessively compromising its biocompatibility and mechanical flexibility.

[0004] Patent CN109912824A discloses a transparent conductive silk fibroin material and its preparation method. The method involves placing an insoluble transparent silk fibroin material in an aqueous solution of EDOT or an EDOT derivative containing SDS colloid, and then oxidizing and polymerizing it under the action of ferric chloride and ammonium persulfate to obtain the transparent conductive silk fibroin material. This method mainly utilizes the electrostatic adsorption between silk fibroin and PEDOT to deposit PEDOT in situ onto the surface of the silk fibroin film. However, the preparation process is relatively complex, which is not conducive to the subsequent preparation of multi-channel silk fibroin-based electrode materials. Furthermore, the preparation process involves multiple oxidizing agents, which will negatively impact the biocompatibility and mechanical flexibility of the silk fibroin itself.

[0005] Reference 1 (Materials Reports, 2019, 33(10), 1734-1737, 1761) reported a PEDOT:PSS-doped silk fibroin composite film. The silk fibroin solution was slowly added dropwise to a neutral pH PEDOT:PSS solution and cured into a film by spin coating and in a constant temperature and humidity chamber. The results showed that, under the influence of silk fibroin, the resonance structure of the PEDOT molecular chain changed from benzoquinone type to quinone type structure. The addition of PEDOT:PSS was conducive to the transformation of the secondary structure of silk fibroin to β-sheet. However, due to different application requirements, this paper did not provide relevant data on the conductivity of the silk fibroin conductive film.

[0006] Reference 2 (ACS Appl. Mater. Interfaces, 2022, 14, 123-137) reports a one-step method for preparing silk fibroin / PEDOT conductive films. This method involves casting a PEDOT dispersion onto a nascent, untreated silk fibroin film. The PEDOT is then locked onto the silk fibroin film surface by relying on the interpenetration between PEDOT and silk fibroin molecules, followed by ethanol-induced structural transformation of the silk fibroin. However, this method has limitations. The interpenetration between PEDOT and silk fibroin molecules is an uncontrollable process, resulting in unsatisfactory uniformity and continuity of PEDOT distribution on the silk fibroin film surface.

[0007] Reference 3 (ACS Appl. Energy Mater. 2023, 6, 2602-2610) describes the fabrication of a wearable thermoelectric generator by spraying a layer of polythiophene / carbon nanotubes onto a silk fibroin substrate. The conductivity of this silk fibroin conductive material is 170 ± 52.8 S·cm. -1 The Seebeck coefficient is 41.8 ± 0.9 μV·K. -1 However, the bonding mechanism between the conductive coating and the silk fibroin substrate has not been fully demonstrated, and its bonding strength still needs further investigation.

[0008] Although some progress has been made in the preparation process and conductivity of the aforementioned silk fibroin conductive thin film materials, the uniformity and continuity of the conductive layer, as well as the strong bonding between the conductive layer and the silk fibroin film, still require further investigation. Therefore, it is of great significance to study a silk fibroin conductive thin film with stable interfacial bonding and excellent conductivity that can be prepared under relatively simple conditions. Summary of the Invention

[0009] To address the problems existing in the prior art, the present invention provides a silk fibroin conductive thin film material and its heat-assisted peeling process.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows:

[0011] A silk fibroin conductive thin film material is composed of a substrate layer and a conductive layer. The substrate layer is made of silk fibroin thin film material, and the conductive layer is made of PEDOT or its derivatives. The substrate layer and the conductive layer are bonded together by intermolecular entanglement, resulting in strong interlayer bonding and uniform dispersion of the conductive layer. The material exhibits low electrochemical impedance under alternating current.

[0012] As a preferred technical solution:

[0013] The conductive thin film material of silk fibroin described above is wherein the substrate is made of pure silk fibroin or silk fibroin containing metal ions, wherein the metal ions are calcium ions, sodium ions or lithium ions (metal ions can be removed by dialysis); the substrate is in the form of a thin film with a thickness of 20 to 500 μm.

[0014] The conductive thin film material of silk fibroin described above has a conductive layer in the form of a thin film with a thickness of 500 nm to 1 μm; the PEDOT derivative is PEDOT-OH, PEDOT-COOH, or PEDOT-NH2; and the conductive material in the substrate to which the conductive material is attached is PEDOT:PSS, PEDOT-OH:PSS, PEDOT-COOH:PSS, PEDOT-NH2:PSS, PEDOT:DBSA, PEDOT-OH:DBSA, PEDOT-COOH:DBSA, or PEDOT-NH2:DBSA.

[0015] The silk fibroin conductive thin film material described above was subjected to ultrasonic treatment for 30 minutes in an ultrasonic cleaner at a frequency of 50 kHz and a power of 1 W / cm². 2 The electrochemical impedance of the silk fibroin conductive film material before and after ultrasound differs by no more than 10%, which can be used to characterize the bonding strength between the conductive layer and the silk fibroin film, indicating that the bonding strength is relatively high; the conductivity of the silk fibroin conductive film material is 9.77~38.61S / cm.

[0016] This invention also provides a heat-assisted peeling process for silk fibroin conductive film material. A silk fibroin solution is poured onto a substrate with an attached conductive material, and dried at a constant temperature to obtain a film composite of silk fibroin and conductive material. Then, the film composite of silk fibroin and conductive material is peeled off from the substrate to obtain the silk fibroin conductive film material.

[0017] As a preferred technical solution:

[0018] The thermally assisted peeling process for a silk fibroin conductive film material as described above, wherein the conductive material in the substrate to which the conductive material is attached is PEDOT:PSS, PEDOT-OH:PSS, PEDOT-COOH:PSS, PEDOT-NH2:PSS, PEDOT:DBSA, PEDOT-OH:DBSA, PEDOT-COOH:DBSA, or PEDOT-NH2:DBSA; and the substrate material in the substrate to which the conductive material is attached is polyethylene terephthalate, polystyrene, or polydimethylsiloxane treated with plasma hydrophilicity.

[0019] The thermally assisted peeling process for a silk fibroin conductive thin film material, as described above, involves preparing the substrate with the attached conductive material by casting or inkjet printing.

[0020] The above-described heat-assisted peeling process for a silk fibroin conductive film material involves casting a conductive material aqueous dispersion with a concentration of 3-12 mg / mL onto a substrate and drying it in an oven.

[0021] The above-described thermal-assisted peeling process for a conductive silk fibroin film material includes an inkjet printing process as follows: a piezoelectric on-demand inkjet printing technology is used to print an aqueous dispersion of the conductive material onto a substrate as ink; the piezoelectric on-demand inkjet printing technology uses sinusoidal piezoelectric pulses with a vibration frequency of 250Hz, an amplitude of 20-40V, and a pulse period of 20-40μs; the printhead diameter is 30-120μm, and the droplet spacing is 25μm.

[0022] The above-described heat-assisted peeling process for a conductive silk fibroin film material, wherein the silk fibroin solution is prepared by dissolving silk fibers in a formic acid system or a lithium bromide system, and the dry weight ratio of silk fibroin to conductive material is 5-50:1.

[0023] The above-described heat-assisted peeling process for a conductive silk fibroin film material involves preparing a silk fibroin solution by dissolving silk fibers in a formic acid system. First, silkworm cocoons are degummed by boiling in a 0.5% sodium bicarbonate solution. Then, the degummed silk fibers are dissolved using a formic acid / calcium chloride mixed solution. The formic acid / calcium chloride mixture contains 4.5% calcium chloride by mass, and the volume ratio of the formic acid / calcium chloride mixture to the mass of the degummed silk fibers is 5–20 mL:1 g, yielding a silk fibroin solution containing calcium ions. Alternatively, a saturated sodium sulfate solution is added to the calcium fibroin solution to precipitate calcium ions. After centrifugation and filtration to remove the calcium sulfate precipitate, a silk fibroin solution containing sodium ions is obtained.

[0024] The above-described heat-assisted peeling process for a conductive silk fibroin film material involves preparing a silk fibroin solution by dissolving silk fibers in a lithium bromide system. First, silkworm cocoons are boiled and degummed using a 0.5% sodium bicarbonate solution. Then, the degummed silk fibers are dissolved using a 9.0M lithium bromide solution, with a lithium bromide solution volume to degummed silk fiber mass ratio of 5–20 mL:1 g, to obtain a silk fibroin solution containing lithium ions. Alternatively, the lithium-ion-containing silk fibroin solution is dialyzed in deionized water using a regenerated cellulose dialysis bag to obtain a silk fibroin solution free of metal ions.

[0025] In the above-described heat-assisted peeling process for a silk fibroin conductive thin film material, the constant temperature heating and drying temperature is 20–80°C, and the time is 10–120 minutes.

[0026] The above-described thermally assisted exfoliation process for a conductive silk fibroin film material involves demolding the silk fibroin film, which is composited with conductive material, from the substrate. Silk fibroin molecules and conductive material molecules are bonded through intermolecular entanglement, a bonding force far greater than that between PEDOT and the substrate. Therefore, PEDOT can be transferred from the substrate to the silk fibroin layer, thus preparing a conductive silk fibroin film material with silk fibroin as the substrate and PEDOT as the conductive layer. The intermolecular entanglement occurs because after the silk fibroin solution is poured onto the conductive material, the silk fibroin molecules are loosely arranged, facilitating the insertion of some conductive material molecular chains into the silk fibroin molecules. After the silk fibroin solution dries, the inserted portions are firmly locked within the silk fibroin, while the remaining conductive material forms the conductive layer of the composite film.

[0027] Invention principle:

[0028] There are generally three existing methods for preparing silk fibroin / PEDOT composite thin film materials:

[0029] (1) Silk fibroin and PEDOT are mixed and then cast and dried to form a film; however, in the silk fibroin / PEDOT composite film prepared by this method, PEDOT molecules are dispersed inside the silk fibroin film and on the shallow surface. Therefore, the PEDOT on the surface of the composite film is unevenly dispersed and has poor conductivity. Moreover, the film prepared by this method has a certain conductivity on both sides, which is not conducive to the subsequent preparation of multi-channel electrodes.

[0030] (2) The silk fibroin film is immersed in EDOT monomer, and then PEDOT is polymerized in situ on the surface of the silk fibroin film using an oxidant (e.g., ferric chloride) to obtain silk fibroin / PEDOT composite film material. This method deposits PEDOT molecules on the surface of the silk fibroin film by polymerization. However, the PEDOT and silk fibroin molecules are only bound by a relatively weak electrostatic interaction, which makes PEDOT easy to fall off. Moreover, the uniformity of PEDOT deposition on the surface of the silk fibroin film is not good. The film prepared by this method has conductive PEDOT material on both sides, which is not conducive to the subsequent preparation of multi-channel electrodes.

[0031] (3) PEDOT solution is poured onto the silk fibroin film and then dried to form a film. This method is a common method for preparing single-sided conductive films. However, the molecular structure of silk fibroin film is relatively dense, and PEDOT molecules are difficult to embed into the film. As a result, the interface bonding between the PEDOT conductive layer and the silk fibroin film is not strong after film formation.

[0032] This invention involves casting a silk fibroin solution onto a substrate coated with PEDOT conductive material. In this process, the silk fibroin molecular structure is relatively loose, facilitating the insertion of PEDOT molecules into the silk fibroin molecules. Furthermore, heating accelerates the evaporation of the silk fibroin solution. After solvent evaporation, the silk fibroin transforms from a solution into a thin film, and the silk fibroin molecules become denser, thus fixing the inserted PEDOT molecules within the silk fibroin film. This results in a strong bond between the conductive layer and the silk fibroin film. The heating method in this invention allows for the control of the silk fibroin molecular structure, effectively preventing excessive PEDOT insertion into the silk fibroin molecules. Therefore, the prepared silk fibroin conductive film material exhibits good uniformity, continuity, and conductivity of the conductive layer.

[0033] In this invention, a silk fibroin solution containing metal salt ions is used for casting. During the process of PEDOT molecules inserting into silk fibroin molecules, metal salt ions can enter the PEDOT molecules to play a doping role and improve the hole transport capability of PEDOT. Therefore, the prepared silk fibroin conductive film material has good conductivity.

[0034] This invention utilizes a heating method in the preparation of conductive silk fibroin thin film materials, which improves the demolding efficiency of the silk fibroin film incorporating conductive materials from the substrate. This is because, to ensure uniform spreading and adhesion of the conductive material on the substrate, the substrate is pre-treated with plasma hydrophilicity. The plasma-treated substrate surface has hydrophilic groups (e.g., hydroxyl groups), which can interact with the hydrophilic ends of the conductive material. Heating can induce the flipping of hydrophilic groups on the substrate surface or the reversal of chemical reactions (e.g., dehydroxylation), thus effectively weakening the interaction forces between the conductive material and the substrate, thereby promoting the peeling of the conductive material from the substrate.

[0035] Beneficial effects

[0036] (1) In the silk fibroin conductive film material of the present invention, the conductive layer has relatively ideal uniformity and continuity, and the conductive layer and the silk fibroin film are firmly and stably bonded. The conductive film has excellent conductivity and stability;

[0037] (2) The hot-temperature assisted peeling process of the silk fibroin conductive film material of the present invention is simple and the film preparation time is short. Attached Figure Description

[0038] Figure 1 Electrochemical impedance spectroscopy diagrams of the silk fibroin conductive film prepared in Example 9 and the silk fibroin conductive film prepared in Comparative Example 1 at different test frequencies.

[0039] Figure 2 The pattern and dimensions of the printed 6-channel electrodes;

[0040] Figure 3 This is a schematic diagram of a thermally assisted peeling process for a silk fibroin conductive thin film material according to the present invention. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0042] The raw material manufacturers and brands involved in the examples are as follows:

[0043] Silkworm cocoons: purchased from Tongxiang, Zhejiang;

[0044] PEDOT:DBSA: Manufacturer is Sigma-Aldrich, CAS: 126213-51-2;

[0045] PEDOT:PSS: Manufacturer is Clevios, brand name PH1000;

[0046] PEDOT-OH:PSS, PEDOT-COOH:PSS and PEDOT-NH2:PSS: synthesized according to the method in patent CN109912824B;

[0047] PEDOT-OH:DBSA, PEDOT-COOH:DBSA and PEDOT-NH2:DBSA: synthesized according to the method in patent CN109912824B.

[0048] The test methods involved in the embodiments are as follows:

[0049] Thickness of conductive layer: The thickness H (cm) of the conductive layer was measured by scanning electron microscopy.

[0050] Electrical conductivity: The sheet resistance Rs of the silk fibroin conductive film material was tested using a high-resistivity meter and a four-probe method. The high-resistivity meter mainly consisted of a Keithley 236 precision digital multimeter and a custom-made four-probe stage. The silk fibroin conductive film material from the examples or comparative examples was cut into 2cm × 0.5cm pieces and placed on the four-probe stage, with the four probes contacting the film surface and arranged in a straight line, with a distance of 0.5cm between adjacent probes. The test was performed using a Keithley 236 precision digital multimeter, and the sheet resistance value Rs was read by the software. The conductivity σ (S / cm) of the conductive layer of the film was calculated using the following formula:

[0051] σ = 1 / (H × Rs)

[0052] Electrochemical impedance spectroscopy (EIS) of the silk fibroin conductive film material before or after ultrasound: The silk fibroin conductive film material was cut into 2cm × 0.5cm pieces, fixed with stainless steel electrode clamps, and immersed in PBS (Gibco, 1X) buffer. A platinum sheet electrode was used as the counter electrode, and a silver chloride electrode was used as the reference electrode, both immersed in PBS buffer to form a typical three-electrode system. The three electrodes were connected to an electrochemical workstation (PGSTAT 204), and the electrochemical impedance spectroscopy was used to test the electrochemical impedance of the material. The test frequency range was 0.1Hz to 1000Hz, and the amplitude was 50mV.

[0053] Example 1

[0054] A method for preparing a silk fibroin solution by dissolving silk fibroin fibers using a formic acid system is as follows: First, silkworm cocoons are boiled and degummed using a 0.5% sodium bicarbonate aqueous solution; then, the degummed silk fibroin fibers are dissolved using a formic acid / calcium chloride mixed solution to obtain a silk fibroin protein solution containing calcium ions with a silk fibroin protein mass fraction of 10%; wherein, the mass percentage of calcium chloride in the formic acid / calcium chloride mixed solution is 4.5%, and the volume ratio of the formic acid / calcium chloride mixed solution to the mass ratio of the degummed silk fibroin fibers is 10 mL: 1 g.

[0055] Example 2

[0056] A method for preparing a silk fibroin solution by dissolving silk fibroin fibers using a formic acid system is as follows: First, silkworm cocoons are boiled and degummed using a 0.5% sodium bicarbonate aqueous solution. Then, the degummed silk fibroin fibers are dissolved using a formic acid / calcium chloride mixed solution to obtain a silk fibroin protein solution containing calcium ions with a silk fibroin protein mass fraction of 20%. In the formic acid / calcium chloride mixed solution, the mass percentage of calcium chloride is 4.5%, and the volume ratio of the formic acid / calcium chloride mixed solution to the mass ratio of the degummed silk fibroin fibers is 5 mL: 1 g.

[0057] Example 3

[0058] A method for preparing a silk fibroin solution by dissolving silk fibroin fibers using a formic acid system is as follows: First, silkworm cocoons are boiled and degummed using a 0.5% sodium bicarbonate aqueous solution. Then, the degummed silk fibroin fibers are dissolved using a formic acid / calcium chloride mixed solution. A saturated sodium sulfate solution is then added to precipitate calcium ions. After centrifugation and filtration to remove the calcium sulfate precipitate, a silk fibroin solution containing sodium ions with a silk fibroin protein content of 6.67% is obtained. In the formic acid / calcium chloride mixed solution, the mass percentage of calcium chloride is 4.5%, and the volume ratio of the formic acid / calcium chloride mixed solution to the mass ratio of the degummed silk fibroin fibers is 15 mL: 1 g.

[0059] Example 4

[0060] A method for preparing a silk fibroin solution by dissolving silk fibroin fibers using a formic acid system is as follows: First, silkworm cocoons are boiled and degummed using a 0.5% sodium bicarbonate aqueous solution. Then, the degummed silk fibroin fibers are dissolved using a formic acid / calcium chloride mixed solution. A saturated sodium sulfate solution is then added to precipitate calcium ions. After centrifugation and filtration to remove the calcium sulfate precipitate, a silk fibroin solution containing sodium ions with a silk fibroin protein content of 5% is obtained. In the formic acid / calcium chloride mixed solution, the mass percentage of calcium chloride is 4.5%, and the volume ratio of the formic acid / calcium chloride mixed solution to the mass of the degummed silk fibroin fibers is 20 mL: 1 g.

[0061] Example 5

[0062] A method for preparing a silk fibroin solution by dissolving silk fibroin fibers using a lithium bromide system is as follows: First, silkworm cocoons are boiled and degummed using a 0.5% sodium bicarbonate aqueous solution; then, the degummed silk fibroin fibers are dissolved using a 9.0M lithium bromide solution to obtain a lithium fibroin solution containing 10% silk fibroin protein; wherein the volume of lithium bromide solution: the mass of degummed silk fibroin fibers is 10 mL: 1 g.

[0063] Example 6

[0064] A method for preparing a silk fibroin solution by dissolving silk fibroin fibers using a lithium bromide system is as follows: First, silkworm cocoons are boiled and degummed using a 0.5% sodium bicarbonate aqueous solution; then, the degummed silk fibroin fibers are dissolved using a 9.0M lithium bromide solution to obtain a lithium fibroin solution containing 20% ​​silk fibroin protein; wherein the volume of lithium bromide solution: the mass of degummed silk fibroin fibers is 5 mL: 1 g.

[0065] Example 7

[0066] A method for preparing a silk fibroin solution by dissolving silk fibroin fibers using a lithium bromide system is as follows: First, silkworm cocoons are boiled and degummed using a 0.5% sodium bicarbonate aqueous solution. Then, the degummed silk fibroin fibers are dissolved using a 9.0M lithium bromide solution to obtain a silk fibroin solution containing lithium ions. The lithium fibroin solution containing lithium ions is then dialyzed in deionized water using a regenerated cellulose dialysis bag to obtain a silk fibroin solution with a mass fraction of 6.67%. The ratio of lithium bromide solution volume to degummed silk fibroin fiber mass is 15 mL: 1 g.

[0067] Example 8

[0068] A method for preparing a silk fibroin solution by dissolving silk fibroin fibers using a lithium bromide system is as follows: First, silkworm cocoons are boiled and degummed using a 0.5% sodium bicarbonate aqueous solution. Then, the degummed silk fibroin fibers are dissolved using a 9.0M lithium bromide solution to obtain a silk fibroin solution containing lithium ions. The lithium fibroin solution containing lithium ions is then dialyzed in deionized water using a regenerated cellulose dialysis bag to obtain a 5% silk fibroin solution. The ratio of lithium bromide solution volume to degummed silk fibroin fiber mass is 20 mL: 1 g.

[0069] Example 9

[0070] A heat-assisted peeling process for conductive silk fibroin thin film materials, such as Figure 3 As shown, the specific steps are as follows:

[0071] (1) Preparation of raw materials;

[0072] Conductive material: PEDOT:PSS;

[0073] Substrate: Polyethylene terephthalate;

[0074] Silk fibroin solution: The silk fibroin solution prepared in Example 1;

[0075] (2) Disperse the conductive material in water to prepare a conductive material aqueous dispersion with a concentration of 12 mg / mL. Use the casting method to cast the conductive material aqueous dispersion onto the substrate and dry it in an oven at 60°C for 30 min to obtain a substrate with conductive material attached.

[0076] (3) A silk fibroin solution is poured onto a substrate with a conductive material attached, and then heated and dried at 60°C for 30 minutes. Then, the film composited with the conductive material after the silk fibroin solution is dried and molded is demolded from the substrate to obtain a silk fibroin conductive film material. The dry weight ratio of the product after the silk fibroin solution is dried and molded to the conductive material is 5:1.

[0077] The prepared silk fibroin conductive film material is composed of a substrate layer and a conductive layer, which are bonded together by intermolecular entanglement. The substrate layer is the product of silk fibroin solution after drying and molding, and its morphology is a thin film with a thickness of 20 μm. The conductive layer is made of conductive material and its morphology is a thin film with a thickness of 1 μm. The conductivity of the silk fibroin conductive film material is 38.61 S / cm. The silk fibroin conductive film material was subjected to ultrasonic treatment for 30 minutes at a frequency of 50 kHz and a power of 1 W / cm. 2 Before ultrasound, the electrochemical impedance of the silk fibroin conductive film material was 1100Ω (1Hz), and after ultrasound, the electrochemical impedance of the silk fibroin conductive film material increased by 7%.

[0078] Comparative Example 1

[0079] A heat-assisted peeling process for a silk fibroin conductive film material is basically the same as in Example 9, except that step (2) of Comparative Example 1 is as follows: the silk fibroin solution is poured onto the substrate and dried in an oven at 60°C for 30 minutes to obtain a substrate with the product formed after the silk fibroin solution is dried; step (3) is as follows: the conductive material is dispersed in water to obtain a conductive material aqueous dispersion with a concentration of 12 mg / mL, and the conductive material aqueous dispersion is poured onto the substrate with the product formed after the silk fibroin solution is dried using a casting method, and heated and dried at 60°C for 30 minutes. Then, the film formed by the dried silk fibroin solution and the conductive material is demolded from the substrate to obtain the silk fibroin conductive film material; wherein, the dry weight ratio of the product formed by the dried silk fibroin solution to the conductive material is 5:1.

[0080] The prepared silk fibroin conductive film material is composed of a substrate layer and a conductive layer, which are bonded together by intermolecular entanglement. The substrate layer is the product of silk fibroin solution drying and molding, and its morphology is a thin film with a thickness of 20 μm. The conductive layer is made of conductive material and its morphology is a thin film with a thickness of 1 μm. The conductivity of the silk fibroin conductive film material is 3.14 S / cm. The silk fibroin conductive film material was subjected to ultrasonic treatment for 30 minutes at a frequency of 50 kHz and a power of 1 W / cm. 2 Before ultrasound, the electrochemical impedance of the silk fibroin conductive film material was 13750Ω (1Hz), and after ultrasound, the electrochemical impedance of the silk fibroin conductive film material increased by 650%.

[0081] like Figure 1 The figure shows the electrochemical impedance spectroscopy (EIR) diagrams of the silk fibroin conductive film prepared in Example 9 and the silk fibroin conductive film prepared in Comparative Example 1 at different test frequencies. Compared with Example 9, the silk fibroin film material in Comparative Example 1 has lower conductivity and higher EIR at the same frequency. After ultrasonic treatment, the EIR increases significantly, indicating that the silk fibroin film material in Comparative Example 1 has poor conductivity and poor bonding between the conductive layer and the substrate layer. This is because when the conductive material is cast onto the silk fibroin substrate, the molecular structure of the silk fibroin substrate is tightly arranged, making it difficult for the conductive material to insert into the silk fibroin molecules. The intermolecular entanglement between the substrate and the conductive layer is poor, which leads to the conductive layer easily detaching from the substrate layer, resulting in poor conductivity. After ultrasonic treatment, a large amount of the conductive layer detaches from the substrate layer, leading to a significant increase in EIR.

[0082] Example 10

[0083] A thermally assisted exfoliation process for a silk fibroin conductive thin film material, comprising the following specific steps:

[0084] (1) Preparation of raw materials;

[0085] Conductive material: PEDOT:DBSA;

[0086] Substrate: Polystyrene;

[0087] Silk fibroin solution: The silk fibroin solution prepared in Example 2;

[0088] (2) Disperse the conductive material in water to prepare a conductive material aqueous dispersion with a concentration of 3 mg / mL. Use the casting method to cast the conductive material aqueous dispersion onto the substrate and dry it in an oven at 60°C for 10 min to obtain a substrate with conductive material attached.

[0089] (3) A silk fibroin solution is poured onto a substrate with a conductive material attached, and then heated and dried at 20°C for 10 minutes. Then, the product after drying and molding of the silk fibroin solution and the film after being combined with the conductive material are demolded from the substrate to obtain a silk fibroin conductive film material. The dry weight ratio of the product after drying and molding of the silk fibroin solution to the conductive material is 10:1.

[0090] The prepared silk fibroin conductive thin film material is composed of a substrate layer and a conductive layer, which are bonded together by intermolecular entanglement. The substrate layer is the product of silk fibroin solution drying and molding, and its morphology is a thin film with a thickness of 90 μm. The conductive layer is made of conductive material, and its morphology is also a thin film with a thickness of 730 nm. The conductivity of the silk fibroin conductive thin film material is 34.86 S / cm. The silk fibroin conductive thin film material was subjected to ultrasonic treatment for 30 minutes at a frequency of 50 kHz and a power of 1 W / cm. 2 Before ultrasound, the electrochemical impedance of the silk fibroin conductive film material was 1203Ω (1Hz), and after ultrasound, the electrochemical impedance of the silk fibroin conductive film material increased by 7.8%.

[0091] Example 11

[0092] A thermally assisted exfoliation process for a silk fibroin conductive thin film material, comprising the following specific steps:

[0093] (1) Preparation of raw materials;

[0094] Conductive material: PEDOT-OH:PSS;

[0095] Substrate: Polydimethylsiloxane;

[0096] Silk fibroin solution: The silk fibroin solution prepared in Example 5;

[0097] (2) A conductive material aqueous dispersion with a concentration of 6 mg / mL was prepared by dispersing the conductive material in water. The conductive material aqueous dispersion was cast onto the substrate by casting method and dried in an oven at 60°C for 60 min to obtain a substrate with conductive material attached.

[0098] (3) A silk fibroin solution is poured onto a substrate with a conductive material attached, and then heated and dried at 30°C for 60 minutes. Then, the product after drying and molding of the silk fibroin solution and the film after being combined with the conductive material are demolded from the substrate to obtain a silk fibroin conductive film material. The dry weight ratio of the product after drying and molding of the silk fibroin solution to the conductive material is 25:1.

[0099] The prepared silk fibroin conductive thin film material is composed of a substrate layer and a conductive layer, which are bonded together by intermolecular entanglement. The substrate layer is the product of silk fibroin solution after drying and molding, and its morphology is a thin film with a thickness of 245 μm. The conductive layer is made of conductive material, and its morphology is also a thin film with a thickness of 660 nm. The conductivity of the silk fibroin conductive thin film material is 32.04 S / cm. The silk fibroin conductive thin film material was subjected to ultrasonic treatment for 30 minutes at a frequency of 50 kHz and a power of 1 W / cm. 2 Before ultrasound, the electrochemical impedance of the silk fibroin conductive film material was 1322 Ω (1 Hz), and after ultrasound, the electrochemical impedance of the silk fibroin conductive film material increased by 7.4%.

[0100] Example 12

[0101] A thermally assisted exfoliation process for a silk fibroin conductive thin film material, comprising the following specific steps:

[0102] (1) Preparation of raw materials;

[0103] Conductive material: PEDOT-OH:DBSA;

[0104] Substrate: Polystyrene;

[0105] Silk fibroin solution: The silk fibroin solution prepared in Example 6;

[0106] (2) Disperse the conductive material in water to prepare a conductive material aqueous dispersion with a concentration of 12 mg / mL. Use the casting method to cast the conductive material aqueous dispersion onto the substrate and dry it in an oven at 60°C for 120 min to obtain a substrate with conductive material attached.

[0107] (3) A silk fibroin solution is poured onto a substrate with a conductive material attached, and then heated and dried at 40°C for 120 minutes. Then, the product after drying and molding of the silk fibroin solution and the film after being combined with the conductive material are demolded from the substrate to obtain a silk fibroin conductive film material. The dry weight ratio of the product after drying and molding of the silk fibroin solution to the conductive material is 50:1.

[0108] The prepared silk fibroin conductive thin film material is composed of a substrate layer and a conductive layer, which are bonded together by intermolecular entanglement. The substrate layer is the product of silk fibroin solution after drying and molding, and its morphology is a thin film with a thickness of 500 μm. The conductive layer is made of conductive material and its morphology is also a thin film with a thickness of 500 nm. The conductivity of the silk fibroin conductive thin film material is 20.11 S / cm. The silk fibroin conductive thin film material was subjected to ultrasonic treatment for 30 minutes at a frequency of 50 kHz and a power of 1 W / cm. 2Before ultrasound, the electrochemical impedance of the silk fibroin conductive film material was 1898Ω (1Hz), and after ultrasound, the electrochemical impedance of the silk fibroin conductive film material increased by 7.5%.

[0109] Example 13

[0110] A thermally assisted exfoliation process for a silk fibroin conductive thin film material, comprising the following specific steps:

[0111] (1) Preparation of raw materials;

[0112] Conductive material: PEDOT-COOH:PSS;

[0113] Substrate: Polyethylene terephthalate;

[0114] Silk fibroin solution: The silk fibroin solution prepared in Example 3;

[0115] (2) A conductive material aqueous dispersion with a concentration of 3 mg / mL was prepared by dispersing the conductive material in water. The conductive material aqueous dispersion was then printed onto a substrate using piezoelectric on-demand inkjet printing technology to obtain a substrate with conductive material attached. The printed pattern and specific dimensions are shown in [reference needed]. Figure 2 Among them, the piezoelectric on-demand inkjet printing technology uses sinusoidal piezoelectric pulses with a vibration frequency of 250Hz, an amplitude of 35V, and a pulse period of 30μs; the printhead diameter is 60μm, and the droplet spacing is 25μm.

[0116] (3) A silk fibroin solution is poured onto a substrate with a conductive material attached, and then heated and dried at 60°C for 30 minutes. Then, the film composited with the conductive material after the silk fibroin solution is dried and molded is demolded from the substrate to obtain a silk fibroin conductive film material. The dry weight ratio of the product after the silk fibroin solution is dried and molded to the conductive material is 5:1.

[0117] The prepared silk fibroin conductive film material is composed of a substrate layer and a conductive layer, which are bonded together by intermolecular entanglement. The substrate layer is the product of silk fibroin solution after drying and molding, and its morphology is a thin film with a thickness of 20 μm. The conductive layer is made of conductive material and its morphology is a thin film with a thickness of 1 μm. The conductivity of the silk fibroin conductive film material is 35.39 S / cm. The silk fibroin conductive film material was subjected to ultrasonic treatment for 30 minutes at a frequency of 50 kHz and a power of 1 W / cm. 2 Before ultrasound, the electrochemical impedance of the silk fibroin conductive film material was 1200Ω (1Hz), and after ultrasound, the electrochemical impedance of the silk fibroin conductive film material increased by 6.8%.

[0118] Example 14

[0119] A thermally assisted exfoliation process for a silk fibroin conductive thin film material, comprising the following specific steps:

[0120] (1) Preparation of raw materials;

[0121] Conductive material: PEDOT-COOH:DBSA;

[0122] Substrate: Polydimethylsiloxane;

[0123] Silk fibroin solution: The silk fibroin solution prepared in Example 4;

[0124] (2) A conductive material aqueous dispersion with a concentration of 6 mg / mL was prepared by dispersing the conductive material in water. The conductive material aqueous dispersion was then printed onto a substrate using piezoelectric on-demand inkjet printing technology to obtain a substrate with the conductive material attached. The piezoelectric on-demand inkjet printing technology used a sinusoidal piezoelectric pulse with a vibration frequency of 250 Hz, an amplitude of 20 V, and a pulse period of 20 μs. The printhead diameter was 80 μm and the droplet spacing was 25 μm.

[0125] (3) A silk fibroin solution is poured onto a substrate with a conductive material attached, and then heated and dried at 50°C for 10 minutes. Then, the film after the silk fibroin solution is dried and formed and combined with the conductive material is demolded from the substrate to obtain a silk fibroin conductive film material. The dry weight ratio of the product after the silk fibroin solution is dried and formed to the dry weight of the conductive material is 10:1.

[0126] The prepared silk fibroin conductive film material is composed of a substrate layer and a conductive layer, which are bonded together by intermolecular entanglement. The substrate layer is the product of silk fibroin solution drying and molding, and its morphology is a thin film with a thickness of 90 μm. The conductive layer is made of conductive material, and its morphology is also a thin film with a thickness of 730 nm. The conductivity of the silk fibroin conductive film material is 29.29 S / cm. The silk fibroin conductive film material was subjected to ultrasonic treatment for 30 minutes at a frequency of 50 kHz and a power of 1 W / cm. 2 Before ultrasound, the electrochemical impedance of the silk fibroin conductive film material was 1450Ω (1Hz), and after ultrasound, the electrochemical impedance of the silk fibroin conductive film material increased by 7.7%.

[0127] Example 15

[0128] A thermally assisted exfoliation process for a silk fibroin conductive thin film material, comprising the following specific steps:

[0129] (1) Preparation of raw materials;

[0130] Conductive material: PEDOT-NH2:PSS;

[0131] Substrate: Polystyrene;

[0132] Silk fibroin solution: The silk fibroin solution prepared in Example 7;

[0133] (2) A conductive material aqueous dispersion with a concentration of 9 mg / mL was prepared by dispersing the conductive material in water. The conductive material aqueous dispersion was then printed onto a substrate using piezoelectric on-demand inkjet printing technology to obtain a substrate with the conductive material attached. The piezoelectric on-demand inkjet printing technology used a sinusoidal piezoelectric pulse with a vibration frequency of 250 Hz, an amplitude of 25 V, and a pulse period of 30 μs. The printhead diameter was 30 μm and the droplet spacing was 25 μm.

[0134] (3) A silk fibroin solution is poured onto a substrate with a conductive material attached, and then heated and dried at 70°C for 60 minutes. Then, the product after drying and molding of the silk fibroin solution and the film after being combined with the conductive material are demolded from the substrate to obtain a silk fibroin conductive film material. The dry weight ratio of the product after drying and molding of the silk fibroin solution to the conductive material is 25:1.

[0135] The prepared silk fibroin conductive thin film material is composed of a substrate layer and a conductive layer, which are bonded together by intermolecular entanglement. The substrate layer is the product of silk fibroin solution drying and molding, and its morphology is a thin film with a thickness of 245 μm. The conductive layer is made of conductive material and its morphology is also a thin film with a thickness of 660 nm. The conductivity of the silk fibroin conductive thin film material is 27.52 S / cm. The silk fibroin conductive thin film material was subjected to ultrasonic treatment for 30 minutes at a frequency of 50 kHz and a power of 1 W / cm. 2 Before ultrasound, the electrochemical impedance of the silk fibroin conductive film material was 1543Ω (1Hz), and after ultrasound, the electrochemical impedance of the silk fibroin conductive film material increased by 7.9%.

[0136] Example 16

[0137] A thermally assisted exfoliation process for a silk fibroin conductive thin film material, comprising the following specific steps:

[0138] (1) Preparation of raw materials;

[0139] Conductive material: PEDOT-NH2:DBSA;

[0140] Substrate: Polydimethylsiloxane;

[0141] Silk fibroin solution: The silk fibroin solution prepared in Example 8;

[0142] (2) A conductive material aqueous dispersion with a concentration of 12 mg / mL was prepared by dispersing the conductive material in water. The conductive material aqueous dispersion was then printed onto a substrate using piezoelectric on-demand inkjet printing technology to obtain a substrate with the conductive material attached. The piezoelectric on-demand inkjet printing technology used a sinusoidal piezoelectric pulse with a vibration frequency of 250 Hz, an amplitude of 40 V, and a pulse period of 40 μs. The printhead diameter was 120 μm and the droplet spacing was 25 μm.

[0143] (3) A silk fibroin solution is poured onto a substrate with a conductive material attached, and then heated and dried at 80°C for 120 minutes. Then, the product after drying and molding of the silk fibroin solution and the film after being combined with the conductive material are demolded from the substrate to obtain a silk fibroin conductive film material. The dry weight ratio of the product after drying and molding of the silk fibroin solution to the conductive material is 50:1.

[0144] The prepared silk fibroin conductive thin film material is composed of a substrate layer and a conductive layer, which are bonded together by intermolecular entanglement. The substrate layer is the product of silk fibroin solution drying and molding, and its morphology is a thin film with a thickness of 950 μm. The conductive layer is made of conductive material, and its morphology is also a thin film with a thickness of 500 nm. The conductivity of the silk fibroin conductive thin film material is 9.77 S / cm. The silk fibroin conductive thin film material was subjected to ultrasonic treatment for 30 minutes at a frequency of 50 kHz and a power of 1 W / cm. 2 Before ultrasound, the electrochemical impedance of the silk fibroin conductive film material was 2044Ω (1Hz), and after ultrasound, the electrochemical impedance of the silk fibroin conductive film material increased by 9.4%.

Claims

1. A heat-assisted peeling process for conductive silk fibroin thin film materials, characterized in that: in A silk fibroin solution is poured onto a substrate with a conductive material attached, and then dried at a constant temperature. Finally, the film composed of silk fibroin and conductive material is peeled off from the substrate to obtain a silk fibroin conductive film material. The conductive material in the substrate with the attached conductive material is PEDOT:PSS, PEDOT-OH:PSS, PEDOT-COOH:PSS, PEDOT-NH2:PSS, PEDOT:DBSA, PEDOT-OH:DBSA, PEDOT-COOH:DBSA or PEDOT-NH2:DBSA; The substrate material of the substrate with the attached conductive material is polyethylene terephthalate, polystyrene, or polydimethylsiloxane that has been treated with plasma hydrophilicity. The peeling refers to removing the silk fibroin film with conductive material composite from the substrate. The silk fibroin molecules and conductive material molecules are bonded together through intermolecular entanglement. The conductive silk fibroin film material was subjected to ultrasonic treatment for 30 minutes at a frequency of 50 kHz and a power of 1 W / cm². The difference in electrochemical impedance of the conductive silk fibroin film material before and after ultrasonic treatment did not exceed 10%. The conductivity of the conductive silk fibroin film material was 9.77~38.61 S / cm.

2. The heat-assisted peeling process for a silk fibroin conductive thin film material according to claim 1, characterized in that, The substrate with the attached conductive material is prepared by either casting or inkjet printing.

3. The heat-assisted peeling process for a silk fibroin conductive thin film material according to claim 2, characterized in that, The process of the casting method is as follows: a conductive material aqueous dispersion with a concentration of 3~12mg / mL is cast onto a substrate using the casting method, and then dried in an oven.

4. The heat-assisted peeling process for a silk fibroin conductive thin film material according to claim 2, characterized in that, The inkjet printing process is as follows: a piezoelectric on-demand inkjet printing technology is used to print a conductive material aqueous dispersion as ink onto a substrate; the piezoelectric on-demand inkjet printing technology uses sinusoidal piezoelectric pulses with a vibration frequency of 250Hz, an amplitude of 20~40V, and a pulse period of 20~40μs; the printhead diameter is 30~120μm, and the droplet spacing is 25μm.

5. The heat-assisted peeling process for a silk fibroin conductive thin film material according to claim 1, characterized in that, The cast silk fibroin solution refers to the silk fibroin solution prepared by dissolving silk fibers in a formic acid system or a lithium bromide system, wherein the dry weight ratio of silk fibroin to conductive material is 5~50:

1.

6. The heat-assisted peeling process for a silk fibroin conductive thin film material according to claim 5, characterized in that, The method for preparing silk fibroin solution by dissolving silk fibroin fibers using a formic acid system is as follows: First, degumming silkworm cocoons is achieved by boiling them in a 0.5% sodium bicarbonate solution. Then, the degummed silk fibroin fibers are dissolved using a formic acid / calcium chloride mixed solution, where the calcium chloride mass percentage is 4.5% and the volume ratio of the formic acid / calcium chloride mixed solution to the mass of the degummed silk fibroin fibers is 5~20mL:1g, thus obtaining a silk fibroin solution containing calcium ions. Alternatively, saturated sodium sulfate solution is added to the silk fibroin solution containing calcium ions to precipitate the calcium ions. After centrifugation and filtration to remove the calcium sulfate precipitate, a silk fibroin solution containing sodium ions is obtained.

7. The heat-assisted peeling process for a silk fibroin conductive thin film material according to claim 5, characterized in that, The method for preparing silk fibroin solution by dissolving silk fibroin fibers using a lithium bromide system is as follows: First, silkworm cocoons are boiled and degummed using a 0.5% sodium bicarbonate solution. Then, the degummed silk fibroin fibers are dissolved using a 9.0M lithium bromide solution, with a lithium bromide solution volume: 5~20 mL: 1 g degummed silk fibroin fiber mass ratio, to obtain a silk fibroin solution containing lithium ions. Alternatively, the lithium ion-containing silk fibroin solution is dialyzed in deionized water using a regenerated cellulose dialysis bag to obtain a silk fibroin solution free of metal ions.

8. The heat-assisted peeling process for a silk fibroin conductive thin film material according to claim 1, characterized in that, The constant temperature heating and drying temperature is 20~80℃, and the time is 10~120 minutes.

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