Fast-degradation high-strength fatigue-resistant nano-cellulose-based flexible electronic skin basement membrane as well as preparation method and application thereof

Abstract

The invention discloses a fast-degradation high-strength fatigue-resistant nano-cellulose-based flexible electronic skin basement membrane as well as a preparation method and application thereof. The flexible electronic skin basement membrane is obtained by the following method: adding CNC subjected to mixed acid hydrolysis into a formic acid solution for grafting modification, and reacting under the protection of nitrogen to obtain modified cellulose nanocrystals (F-CNC). Then, chloroform (CHCl3) is used as a solvent, polylactic acid (PLA) and F-CNC are dissolved respectively, and finally, a film coating device is adopted for preparing the composite film. The flexible electronic skin basement membrane has good mechanical properties and rapid degradation performance, and effectively solves the problems of short service life, poor wearable performance and the like of traditional sensing electronic skin, and the problems of white pollution and the like caused by the fact that the traditional sensing electronic skin is difficult to degrade after being discarded after being used.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible electronic sensors, and specifically relates to a fast-degrading, high-strength, and fatigue-resistant nanocellulose-based flexible electronic skin basement membrane, as well as a preparation method and application thereof. Background Art

[0002] Polylactic acid (PLA), a renewable biomaterial, demonstrates potential for application as a basement membrane for flexible electronic skin due to its biocompatibility and biodegradability. However, PLA suffers from insufficient toughness, slow degradation, and poor overall performance. This is due to its lack of reactive functional groups in its molecular chains and its highly hydrophobic surface, which hinders performance optimization. Despite various proposed modification methods, PLA's slow degradation continues to severely limit its practical application. Therefore, simultaneously improving PLA's degradation efficiency and overall performance is crucial for technological breakthroughs.

[0003] Natural cellulose nanocrystals (CNCs), due to their high strength and unique cellulose structure, can be used as reinforcing fillers to enhance the intermolecular forces of PLA, thereby improving mechanical properties, enhancing toughness, and accelerating degradation. However, the extremely strong hydrophilicity of CNCs and the intermolecular hydrogen bonding network formed by surface hydroxyl groups result in poor dispersibility and insufficient interfacial compatibility in non-polar polymer matrices, severely restricting their application in high-performance hydrophobic composites.

[0004] Patent document CN 118620258A discloses a method for preparing a composite membrane by hydrophobizing CNC with magnesium stearate. Although this method can enhance the compatibility of CNC with polymers and improve the mechanical properties of the composite membrane to a certain extent, the enhanced hydrophobicity of the composite membrane hinders the entry of water molecules and microorganisms into the PLA molecular chains, slowing the degradation rate of the composite membrane.

[0005] Inspired by the above conclusions, this paper proposes for the first time the use of formic anhydride in situ esterification to modify the surface of CNC with formyl groups. We found that formic acid, a green, low-cost weak acid, can be used to modify the surface of CNC with formyl groups by in situ esterification with formic anhydride, forming a controllable formyl functional layer that effectively enhances the interfacial bonding between CNC and polylactic acid (PLA). By forming polar chains with PLA, CNC improves the mechanical properties, toughness, and fatigue resistance of the flexible electronic skin basement membrane, thereby enhancing its durability as an electronic skin. Formyl groups (-CHO) replace surface hydroxyl groups, while retaining weak polarity without significantly reducing the hydrophilicity of the flexible electronic skin basement membrane, making the modified CNC both dispersible and interfacially compatible. Compared with hydrophobic modification, formic acid modification is more conducive to the entry of water molecules and microorganisms into the molecular chain, accelerating its environmental degradation rate as a discarded sensing electronic skin basement membrane. This modification method makes full use of the non-toxic and degradable properties of formic acid and CNC, conforms to the concept of sustainable development, not only optimizes the comprehensive performance of PLA-based composite materials, but also provides a feasible technical path for the large-scale application of flexible sensing electronic skin base membranes. It has important research value and industrialization prospects in promoting the green transformation of flexible sensors. Summary of the Invention

[0006] Based on the above-mentioned shortcomings and deficiencies in the prior art, and in order to overcome the problems of poor toughness, weak fatigue resistance, slow degradation rate, and poor filler dispersion of PLA materials, the present invention provides a fast-degrading, high-strength, and fatigue-resistant nanocellulose-based flexible electronic skin substrate membrane, as well as its preparation method and application.

[0007] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions: A method for preparing a fast-degrading, high-strength, and fatigue-resistant nanocellulose-based (CNC) flexible electronic skin basement membrane comprises the following steps: (1) Microcrystalline cellulose (MCC) was added to a mixed solution of citric acid and hydrochloric acid, stirred at 70-90°C for a predetermined time, and then taken out, dialyzed with deionized water until neutral, and freeze-dried to obtain cellulose nanocrystal CNC powder; (2) adding dried cellulose nanocrystals (CNC) to a formic anhydride reaction system generated by the reaction of formic acid (FA) and acetic anhydride; stirring the reaction at 60-70°C for 2-4 hours under inert gas protection; after the reaction, pouring the mixture into ice acetone to quench the reaction and separating the precipitate; washing the precipitate with acetone by centrifugation 2-3 times, and finally dialyzing it with deionized water to neutrality, and freeze-drying the formyl-grafted cellulose nanocrystals (F-CNC); (3) dissolving polylactic acid (PLA) in a chloroform (CHCl3) solution to obtain a mixed solution; dispersing F-CNC in the chloroform solution to obtain a dispersion; and stirring the mixed solution and the dispersion to obtain a film-forming solution; (4) The film-forming liquid is coated by a cast film process, and after drying, a fast-degradable flexible electronic skin base film is obtained.

[0008] As a preferred embodiment, in step (1), the volume ratio of citric acid to hydrochloric acid is 9:1, and the dosage ratio of microcrystalline cellulose, citric acid solution and hydrochloric acid solution is (1-1.2) g:54 mL:6 mL, wherein the concentrations of citric acid solution and hydrochloric acid solution are 3 mol / L and 6 mol / L, respectively.

[0009] As a preferred solution, in step (1), the predetermined duration is 3-5 hours.

[0010] As a preferred embodiment, in step (2), formic acid and acetic anhydride are mixed in a volume ratio of (3:1) to (5:1) in an ice bath at 0°C and stirred for 10-30 minutes to generate formic anhydride. The mass volume ratio of CNC to formic acid is 1 g: (15-25) mL. The formic acid concentration is ≥95%, and the acetic anhydride concentration is ≥98%.

[0011] As a preferred embodiment, in step (2), the preparation method according to claim 1 is characterized in that, in step (2), the amount of glacial acetone is 8-12 times the volume of the reaction mixture.

[0012] As a preferred embodiment, in the step (3), the solid-liquid mass ratio of PLA to chloroform solution in the mixed solution is (18-19.8) g:120 g, and the mixture is stirred and dissolved at 60-65°C; the solid-liquid ratio of F-CNC to chloroform solution in the membrane-forming solution is (0.2-2) g:60 g.

[0013] The present invention further provides a fast-degrading, high-strength, fatigue-resistant flexible electronic skin base film prepared by the above preparation method.

[0014] As a preferred solution, the mass fraction of the modified cellulose nanocrystals F-CNC in the fast-degrading, high-strength, and fatigue-resistant flexible electronic skin basement membrane is 1-7%.

[0015] The present invention further provides the application of the fast-degrading, high-strength, and fatigue-resistant flexible electronic skin basement membrane as an agricultural flexible electronic skin basement membrane in protecting plant growth and development.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. Interface modification and dispersion optimization: By grafting CNC with formic acid, formyl groups (-CHO) replace surface hydroxyl groups, maintaining weak polarity without significantly reducing the hydrophilicity of the flexible electronic skin basement membrane. This allows the modified CNC to have both dispersibility and interfacial compatibility. Reducing the hydroxyl content on the CNC surface and the formation of hydrogen bonds between CNCs significantly improves the dispersion of CNC in the hydrophobic PLA matrix and avoids agglomeration, thereby achieving a uniform blend of CNC and PLA, thereby improving the overall performance of the flexible electronic skin basement membrane. 2. Accelerated degradation to address white pollution: The flexible electronic skin basement membrane incorporating F-CNC still retains some hydrophilicity. When discarded, this allows water molecules carrying microorganisms to enter the material, increasing the contact area between microorganisms and PLA and accelerating degradation. The weight loss rate for soil degradation reached 31.9% within 140 days, while the weight loss rate for environmental degradation increased by 226.7% within 90 days and by 115.4% within 30 days of UV degradation. This rapid degradation rate and good biodegradability effectively prevent white pollution. 3. Process universality and environmental friendliness: The solution blending and cast film forming process is simple to operate and suitable for scaled film production. Formic acid and CNC raw materials are low-cost, non-toxic, and biodegradable, meeting the needs of green industries. Formic anhydride, generated from formic acid / acetic anhydride, is used as the esterification agent under mild reaction conditions, avoiding CNC degradation caused by strong acids and high temperatures. The byproduct is acetic acid, which is much less toxic than traditional acylating agents (such as acetyl chloride). Quenching with glacial acetone in one step achieves reaction termination and product precipitation, simplifying the purification process. The cost of the raw formic acid is only one-fifth of that of acetic anhydride, significantly reducing industrial costs. 4. Comprehensive performance balance: The formyl groups grafted on F-CNC have strong polarity, strengthening the intermolecular forces. In addition, F-CNC can act as a nucleating agent in the PLA matrix, accelerating PLA crystallization, which can improve the mechanical properties of the flexible electronic skin base membrane. According to experimental tests, the toughness of the flexible electronic skin base membrane is increased to 2.47 MJ / m 3 The maximum tensile strength is increased to 36.9MPa, the crystallization rate is increased by 24%, the crystallinity is as high as 30.2%, and the tensile strength is still retained at 79.9% after rubbing 100 times. This makes the flexible electronic skin base membrane have both high mechanical properties and fatigue resistance, which can effectively solve the shortcomings of flexible sensor flexible electronic skin base membrane such as poor wearability and short service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The following are Fourier transform infrared (FT-IR) spectra of CNC and F-CNC of Example 1 of the present invention and a comparison of their dispersion in PLA / chloroform solution; Figure 2Field emission scanning electron microscopy (FE-SEM) test images of the cross-section of the fast-degrading, high-strength, fatigue-resistant flexible electronic skin substrate membranes of Examples 1-4 of the present invention and Comparative Example 1; Figure 3 Graphs showing the tensile mechanical properties test results, crystallinity, and crystallization rate test results of the fast-degrading, high-strength, and fatigue-resistant flexible electronic skin base films of Examples 1-4 of the present invention and Comparative Examples 1-3; Figure 4 This is a comparison chart of the soil, environmental, and UV degradation rates of the fast-degrading, high-strength, and fatigue-resistant flexible electronic skin base film and pure PLA film according to Example 1 of the present invention; Figure 5 This is a comparison chart of the tensile strength of the fast-degrading, high-strength, fatigue-resistant flexible electronic skin base film of Example 1 of the present invention and the pure PLA film after rubbing them 50 times and 100 times. DETAILED DESCRIPTION

[0018] In order to make the technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] Example 1

[0020] The method for preparing the fast-degradable flexible electronic skin basement membrane of this embodiment comprises the following steps: (1) MCC is hydrolyzed with mixed acid to obtain cellulose nanocrystals CNC. The specific process is as follows: 5 g of MCC was added to a mixture of 30 mL of hydrochloric acid (HCl) aqueous solution and 270 mL of citric acid (CA) aqueous solution, where the concentrations of the HCl aqueous solution and the CA aqueous solution were 6 mol / L and 3 mol / L, respectively. The mixture was stirred at 80°C for 4 hours and finally dialyzed with deionized water to thoroughly wash away residual citric acid to obtain CNC.

[0021] (2) Using formic acid to modify cellulose nanocrystals CNC, the specific process is as follows: CNC powder was dried in a vacuum oven at 60°C for 24 hours to completely remove moisture. In an ice bath, 20 mL of formic acid (concentration ≥95%) and 5 mL of acetic anhydride (concentration ≥98%) were mixed in a three-necked flask and stirred for 10 minutes. 1 g of dried CNC was slowly added to the mixture. A condenser was installed, the temperature was raised to 65°C, and the reaction was stirred under nitrogen for 3 hours. The reaction solution was quickly poured into 200 mL of icy acetone and stirred for 10 minutes to precipitate the product. The precipitate was washed with acetone by centrifugation 2-3 times and finally dialyzed against deionized water until neutral. The formyl-grafted cellulose nanocrystals (F-CNC) were freeze-dried.

[0022] (3) PLA was dissolved in a CHCl₃ solution at a solid-liquid ratio of 19 g:120 g to obtain a mixed solution. 1 g of F-CNC was dispersed in 60 g of CHCl₃ solution to obtain a dispersion. The mixed solution and the dispersion were stirred to obtain a film-forming solution. Subsequently, a film was cast and dried to obtain a rapidly degradable flexible electronic skin base film, PLA-5%.

[0023] Among them, the mass of F-CNC accounts for 5% of the total mass of the flexible electronic skin basement membrane.

[0024] Example 2

[0025] The method for preparing the fast-degradable flexible electronic skin basement membrane of this embodiment comprises the following steps: (1) MCC is hydrolyzed with mixed acid to obtain cellulose nanocrystals CNC. The specific process is as follows: 5 g of MCC was added to a mixture of 30 mL of hydrochloric acid (HCl) aqueous solution and 270 mL of citric acid (CA) aqueous solution, where the concentrations of the HCl aqueous solution and the CA aqueous solution were 6 mol / L and 3 mol / L, respectively. The mixture was stirred at 80°C for 4 hours and finally dialyzed with deionized water to thoroughly wash away residual citric acid to obtain CNC.

[0026] (2) Using formic acid to modify cellulose nanocrystals CNC, the specific process is as follows: CNC powder was dried in a vacuum oven at 60°C for 24 hours to completely remove moisture. In an ice bath, 20 mL of formic acid (concentration ≥ 95%) and 5 mL of acetic anhydride (concentration ≥ 98%) were stirred for 10 minutes. 1 g of dried CNC was slowly added to the mixture. A condenser was installed, the temperature was raised to 65°C, and the reaction was stirred under nitrogen for 3 hours. The reaction solution was quickly poured into 200 mL of icy acetone and stirred for 10 minutes to precipitate the product. The precipitate was washed with acetone by centrifugation 2-3 times and finally dialyzed with deionized water until neutral. The formyl-grafted cellulose nanocrystals (F-CNC) were freeze-dried.

[0027] (3) PLA was dissolved in a CHCl₃ solution at a solid-liquid ratio of 19.8 g:120 g to obtain a mixed solution. 0.2 g of F-CNC was dispersed in 60 g of CHCl₃ solution to obtain a dispersion. The mixed solution and the dispersion were stirred to obtain a film-forming solution. Subsequently, a film was cast and dried to obtain a rapidly degradable flexible electronic skin base film, PLA-1%.

[0028] Among them, the mass of F-CNC accounts for 1% of the total mass of the flexible electronic skin basement membrane.

[0029] Example 3

[0030] The method for preparing the fast-degradable flexible electronic skin basement membrane of this embodiment comprises the following steps: (1) MCC is hydrolyzed with mixed acid to obtain cellulose nanocrystals CNC. The specific process is as follows: 5 g of MCC was added to a mixture of 30 mL of hydrochloric acid (HCl) aqueous solution and 270 mL of citric acid (CA) aqueous solution, where the concentrations of the HCl aqueous solution and the CA aqueous solution were 6 mol / L and 3 mol / L, respectively. The mixture was stirred at 80°C for 4 hours and finally dialyzed with deionized water to thoroughly wash away residual citric acid to obtain CNC.

[0031] (2) Using formic acid to modify cellulose nanocrystals CNC, the specific process is as follows: CNC powder was dried in a vacuum oven at 60°C for 24 hours to completely remove moisture. In an ice bath, 20 mL of formic acid (concentration ≥ 95%) and 5 mL of acetic anhydride (concentration ≥ 98%) were stirred for 10 minutes. 1 g of dried CNC was slowly added to the mixture. A condenser was installed, the temperature was raised to 65°C, and the reaction was stirred under nitrogen for 3 hours. The reaction solution was quickly poured into 200 mL of icy acetone and stirred for 10 minutes to precipitate the product. The precipitate was washed with acetone by centrifugation 2-3 times and finally dialyzed with deionized water until neutral. The formyl-grafted cellulose nanocrystals (F-CNC) were freeze-dried.

[0032] (3) PLA was dissolved in a CHCl₃ solution at a solid-liquid ratio of 19.4 g:120 g to obtain a mixed solution. 0.6 g of F-CNC was dispersed in 60 g of CHCl₃ solution to obtain a dispersion. The mixed solution and the dispersion were stirred to obtain a film-forming solution. Subsequently, a film was cast and dried to obtain a rapidly degradable flexible electronic skin base film, PLA-3%.

[0033] Among them, the mass of F-CNC accounts for 3% of the total mass of the flexible electronic skin basement membrane.

[0034] Example 4

[0035] The method for preparing the fast-degradable flexible electronic skin basement membrane of this embodiment comprises the following steps: (1) MCC is hydrolyzed with mixed acid to obtain cellulose nanocrystals CNC. The specific process is as follows: 5 g of MCC was added to a mixture of 30 mL of hydrochloric acid (HCl) aqueous solution and 270 mL of citric acid (CA) aqueous solution, where the concentrations of the HCl aqueous solution and the CA aqueous solution were 6 mol / L and 3 mol / L, respectively. The mixture was stirred at 80°C for 4 hours and finally dialyzed with deionized water to thoroughly wash away residual citric acid to obtain CNC.

[0036] (2) Using formic acid to modify cellulose nanocrystals CNC, the specific process is as follows: CNC powder was dried in a vacuum oven at 60°C for 24 hours to completely remove moisture. In an ice bath, 20 mL of formic acid (concentration ≥ 95%) and 5 mL of acetic anhydride (concentration ≥ 98%) were stirred for 10 minutes. 1 g of dried CNC was slowly added to the mixture. A condenser was installed, the temperature was raised to 65°C, and the reaction was stirred under nitrogen for 3 hours. The reaction solution was quickly poured into 200 mL of icy acetone and stirred for 10 minutes to precipitate the product. The precipitate was washed with acetone by centrifugation 2-3 times and finally dialyzed with deionized water until neutral. The formyl-grafted cellulose nanocrystals (F-CNC) were freeze-dried.

[0037] (3) PLA was dissolved in a CHCl₃ solution at a solid-liquid ratio of 18.6 g:120 g to obtain a mixed solution. 1.4 g of F-CNC was dispersed in 60 g of CHCl₃ solution to obtain a dispersion. The mixed solution and the dispersion were stirred to obtain a film-forming solution. Subsequently, a film was cast and dried to obtain a rapidly degradable flexible electronic skin base film, PLA-7%.

[0038] Among them, the mass of F-CNC accounts for 7% of the total mass of the flexible electronic skin basement membrane.

[0039] Comparative Example 1

[0040] The preparation method of the flexible electronic skin basement membrane of this comparative example is different from that of Example 1 in that: Without adding F-CNC to strengthen the modification of polylactic acid (PLA), PLA was directly and evenly dissolved in CHCl3 solution. The other steps were the same as those in Example 1. The prepared composite film was marked as PLA.

[0041] Comparative Example 2

[0042] The preparation method of the flexible electronic skin basement membrane of this comparative example is different from that of Example 1 in that: Without using formic acid to perform surface grafting modification on cellulose nanocrystals CNC, CNC powder was directly dispersed evenly in PLA solution. Other steps were the same as those in Example 1. The prepared composite membrane was labeled PLA-CNC (5).

[0043] Comparative Example 3

[0044] The preparation method of the flexible electronic skin basement membrane of this comparative example is different from that of Example 1 in that: The mass of the added F-CNC powder accounted for 10% of the total mass of the flexible electronic skin basement membrane. The other steps were the same as in Example 1. The prepared composite membrane was marked as PLA-10%.

[0045] like Figure 1As shown, compared with the characteristic spectrum of CNC, the modified F-CNC spectrum has a peak at 1735 cm -1 A new absorption peak appeared at . This peak is attributed to the increased content of ester groups on the F-CNC surface, indicating the successful introduction of formyl groups (-OCHO). Furthermore, compared to CNC, the modified F-CNC exhibited superior dispersion in PLA chloroform compared to unmodified CNC, laying the foundation for improving the overall performance of flexible electronic skin substrate membranes.

[0046] like Figure 2 As shown in Example 1, a fast-degrading, high-strength, and fatigue-resistant nanocellulose-based (CNC) flexible electronic skin base membrane was successfully prepared. It can be seen that with the increase of the F-CNC load, regular wavy patterns gradually appeared on the cross-section of the flexible electronic skin base membrane. The F-CNC was evenly dispersed in PLA, which helped to improve the mechanical properties of the flexible electronic skin base membrane. However, when the load reached 10% (Comparative Example 3), due to the increase in concentration, the F-CNC inevitably agglomerated, resulting in the rupture of the flexible electronic skin base membrane. Therefore, it can be seen that the higher the content of F-CNC is, the better, but there is an optimal feed ratio - PLA5% (Example 1).

[0047] like Figure 3 As shown, PLA is a brittle plastic. Compared with PLA, the maximum tensile strength of the flexible electronic skin base membrane in Example 1 increased by 32.3% and the toughness increased by 154.6%. This is because the heterogeneous nucleation effect of F-CNC plays a role, and the interlocking adhesion between CNC and PLA plays an important role. The stable contoured thread interlocking and entanglement formed between F-CNC and PLA may hinder the initiation of cracks and resist crack propagation, which makes Example 1 have more excellent mechanical properties. However, with increasing concentration, the maximum tensile strength and toughness of Comparative Example 3 decreased significantly. Excessive surface content of F-CNC may cause problems such as phase separation or stress concentration, thereby reducing impact toughness. In Comparative Example 2, the unmodified CNC surface contains a large number of hydroxyl groups that easily form hydrogen bonds, making it difficult to disperse evenly in PLA, resulting in phase separation or stress concentration, thereby reducing impact toughness. In addition, F-CNC can also act as a nucleating agent in the PLA matrix, accelerating the crystallization of PLA and increasing its crystallinity, thereby comprehensively improving the overall performance of the flexible electronic skin base membrane.

[0048] like Figure 4As shown, the weight loss of Example 1 increased by 456.8% compared to the weight loss of Comparative Example 1 due to soil degradation, 226.7% due to environmental degradation, and 115.4% due to UV degradation, demonstrating a rapid degradation rate. Good biodegradability is essential for addressing white pollution from discarded plastic film materials, such as flexible electronic skin substrates for flexible sensing.

[0049] like Figure 5 As shown in the figure, after 100 rubbings, the flexible electronic skin base membrane of Example 1 can still maintain 79.9% of the tensile strength, has high anti-fatigue ability, can effectively improve its service life as a flexible electronic skin base membrane, and effectively solves the problem of poor wearability of flexible electronic skin.

[0050] The above description is only a detailed description of the preferred embodiments and principles of the present invention. For ordinary technicians in this field, based on the ideas provided by the present invention, there may be changes in the specific implementation methods, and these changes should also be considered as the scope of protection of the present invention.

Claims

1. A method for preparing a fast-degrading, high-strength, fatigue-resistant nanocellulose-based (CNC) flexible electronic skin basement membrane, characterized in that: The following steps are involved: (1) Microcrystalline cellulose (MCC) was added to a mixed solution of citric acid and hydrochloric acid, stirred at 70-90°C for a predetermined time, and then taken out, dialyzed with deionized water until neutral, and freeze-dried to obtain cellulose nanocrystal CNC powder; (2) Adding dried cellulose nanocrystals (CNC) to a formic anhydride reaction system generated by the reaction of formic acid (FA) and acetic anhydride; stirring the reaction at 60-70°C for 2-4 hours under inert gas protection; after the reaction, pouring the mixture into ice acetone to quench the reaction and separating the precipitate; washing the precipitate with acetone by centrifugation 2-3 times, and finally dialyzing it with deionized water to neutrality, and freeze-drying the formyl-grafted cellulose nanocrystals (F-CNC); (3) dissolving polylactic acid (PLA) in a chloroform (CHCl3) solution to obtain a mixed solution; dispersing F-CNC in the chloroform solution to obtain a dispersion; and stirring the mixed solution and the dispersion to obtain a film-forming solution; (4) The film-forming liquid is coated by a cast film coating process, and after drying, a fast-degradable flexible electronic skin base film is obtained.

2. The preparation method according to claim 1, characterized in that In the step (1), the volume ratio of citric acid to hydrochloric acid is 9:1, and the dosage ratio of microcrystalline cellulose, citric acid solution and hydrochloric acid solution is (1-1.2) g:54 mL:6 mL, wherein the concentrations of citric acid solution and hydrochloric acid solution are 3 mol / L and 6 mol / L, respectively.

3. The preparation method according to claim 1, characterized in that In the step (1), the predetermined duration is 3-5 hours.

4. The preparation method according to claim 1, characterized in that In step (2), formic acid and acetic anhydride are mixed in a volume ratio of (3:1) to (5:1) in an ice bath at 0°C and stirred for 10-30 minutes to generate formic anhydride. The mass volume ratio of CNC to formic acid is 1 g: (15-25) mL. The formic acid concentration is ≥95%, and the acetic anhydride concentration is ≥98%.

5. The preparation method according to claim 1, characterized in that In the step (2), the amount of glacial acetone used is 8-12 times the volume of the reaction mixture.

6. The preparation method according to claim 1, characterized in that In the step (3), the solid-liquid mass ratio of PLA to chloroform solution in the mixed solution is (18-19.8) g:120 g, and the mixture is stirred and dissolved at 60-65°C; the solid-liquid ratio of F-CNC to chloroform solution in the membrane-forming solution is (0.2-2) g:60 g.

7. A fast-degrading, high-strength, fatigue-resistant flexible electronic skin base film prepared by the preparation method according to any one of claims 1 to 6.

8. The fast-degrading, high-strength, fatigue-resistant flexible electronic skin base film according to claim 1, characterized in that: The mass fraction of the modified cellulose nanocrystals F-CNC in the fast-degrading, high-strength, and fatigue-resistant flexible electronic skin basement membrane is 1-7%.

9. An application of the fast-degrading, high-strength, and fatigue-resistant flexible electronic skin basement membrane as described in claims 1-6 as an agricultural flexible electronic skin basement membrane in protecting plant growth and development.

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