Flexible electrode for electronic skin and preparation method thereof

Abstract

The invention relates to a flexible electrode for electronic skin and a preparation method thereof, and belongs to the field of electronic skin. The flexible electrode for the electronic skin disclosed by the invention is prepared from polybenzodifuran diketone, nano metal powder and maleimide modified polyurethane. The flexible electrode disclosed by the invention still keeps excellent conductivity after being repeatedly stretched; meanwhile, the self-repairing performance is achieved, the initial performance of the material can be recovered when the material is damaged, the service cycle of the electronic skin can be prolonged, and the maintenance cost is reduced.

Description

Technical Field

[0001] This invention relates to the fields of electronic skin and electrode technology, and in particular to a flexible electrode for electronic skin and its preparation method. Background Technology

[0002] The conductive electrodes in electronic skin are the core components for tactile sensing and signal transmission, and their design and material selection directly affect the sensor's sensitivity, flexibility, and reliability. Traditional electrodes are generally made of metal, which is inherently inflexible. Flexibility is often achieved by thinning the metal film or designing special structures, which significantly increases costs and complicates the manufacturing process. Furthermore, electronic skin inevitably suffers accidental mechanical damage during use. Electrode damage reduces the lifespan of the electronic skin and decreases its long-term stability and reliability. Summary of the Invention

[0003] Based on the need for flexible and self-healing electrodes in electronic skin, this invention provides a flexible electrode for electronic skin and its preparation method. The flexible electrode of this invention maintains excellent conductivity even after repeated stretching; it also possesses self-healing properties, restoring the material's initial properties upon damage, thus extending the service life of the electronic skin and reducing maintenance costs.

[0004] This invention is achieved through the following technical solution:

[0005] The first objective of this invention is to provide a flexible electrode for electronic skin, the flexible electrode being composed of polybenzodifurandione (PBFDO), nano-metal powder, and maleimide-modified polyurethane.

[0006] In one embodiment of the present invention, the maleimide-modified polyurethane is prepared by the following steps:

[0007] Maleimide-modified oligomeric polyols are obtained by reacting amino-containing oligomeric polyols with maleic anhydride.

[0008] The obtained maleimide-modified oligomer polyol was reacted with diisocyanate to obtain maleimide-modified polyurethane prepolymer;

[0009] The obtained polyurethane prepolymer is reacted with a chain extender to obtain the maleimide-modified polyurethane.

[0010] In one embodiment of the present invention, the diisocyanate is selected from isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), polymethylene polyphenyl isocyanate (PAPI), naphthalene diisocyanate (NDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), or tetramethylisophthalene diisocyanate (TMXDI), etc.

[0011] In one embodiment of the present invention, the chain extender is selected from one or more of alcohols, amines, and alkanolamines; specifically, it is ethylenediamine (EDA), 1,4-butanediamine (BDA), m-phenylenediamine (MPDA), 4,4'-diaminodiphenylmethane (MDA), 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), diethyltoluenediamine (DETDA), ethylene glycol (EG), 1,4-butanediol (BDO), diethylene glycol (DEG), 1,6-hexanediol (HDO), neopentyl glycol (NPG), dihydroxyethylphosphonate (DEHP), dimethylolpropionic acid (DMPA), N-methyldiethanolamine (MDEA), aminopropyltriethoxysilane (APTES), hydrazine hydrate, or oxalohydrazide, etc.

[0012] In one embodiment of the present invention, the metal component in the nano-metal powder is selected from one or more of silver, copper, gold, nickel, tin, aluminum, platinum, chromium, zinc, titanium and tungsten.

[0013] In one embodiment of the present invention, the structure of the nano-metal powder includes single metal powder, mixture of multiple metal powders, or composite metal powder.

[0014] In one embodiment of the present invention, the shape of the nano-metal powder includes spherical, rod-shaped, sheet-shaped, or irregular shapes.

[0015] In one embodiment of the present invention, the mass ratio of the polybenzodifuran diketone to the nano-metal powder is 1~5:3~7.

[0016] In one embodiment of the present invention, the mass ratio of the polybenzodifuran dione to the maleimide-modified polyurethane is 1~5:2~6.

[0017] A second objective of this invention is to provide a method for preparing the flexible electrode for electronic skin, comprising the following steps:

[0018] (1) Dissolve polybenzodifuran dione in an organic solvent to obtain mixture 1;

[0019] (2) Disperse the nano-metal powder in the mixture 1 obtained in step (1) to obtain mixture 2;

[0020] (3) Prepare maleimide-modified polyurethane, add the obtained maleimide-modified polyurethane to the mixture 2 obtained in step (2) for reaction, dry, and obtain the flexible electrode of electronic skin.

[0021] In one embodiment of the present invention, in step (1), the organic solvent is one or more of dimethyl sulfoxide, N,N-dimethylformamide and N-methylpyrrolidone.

[0022] In one embodiment of the present invention, in step (3), the reaction conditions are: stirring at 50~70°C for 1~24 hours.

[0023] In one embodiment of the present invention, in step (3), the drying conditions are: drying at 40~80℃ for 2~24 h.

[0024] A third objective of this invention is to provide the application of the aforementioned flexible electrode in electronic skin.

[0025] The technical solution of the present invention has the following advantages compared with the prior art:

[0026] This invention provides a flexible electrode for electronic skin and its preparation method. The flexible electrode of this invention is composed of polybenzodifuran dione, nano-metal powder, and maleimide-modified polyurethane. A triple synergistic conductive self-healing network is formed within the flexible electrode system of this invention, maintaining excellent conductivity even after repeated stretching, while also possessing rapid self-healing properties, thus meeting the requirements of electronic skin for flexible and self-healing electrodes.

[0027] The surface of the nano-metal powder is modified in situ with polybenzodifuran diketone to form an organic protective film, which can inhibit the oxidation and aggregation of the nano-metal powder and improve its intrinsic conductivity. Multiple bonding interactions (covalent bonding, charge bonding, and hydrogen bonding) enhance the interfacial forces between the nano-metal powder and polyurethane. The high specific surface area of ​​the nano-metal powder allows the polyurethane matrix to better dissipate energy during plastic deformation, improving the matrix flexibility and ensuring that the polyurethane matrix maintains excellent conductivity during deformation.

[0028] Maleimide-modified polyurethane forms dynamic DA (Diels-Alder) reversible covalent bonds and multiple hydrogen bonds with polybenzodifurandione (e.g., Figure 1 It can repair itself after being damaged, achieving self-adaptation and self-repair. The nanoscale size of the nano metal powder also matches the movement of polymer chain segments, assisting in rapid dynamic damage repair. Attached Figure Description

[0029] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0030] Figure 1 This is a schematic diagram of the flexible electrode-coordinated conductive self-healing network for electronic skin according to the present invention;

[0031] Figure 2 This refers to the resistance change during tensile deformation in the embodiments and comparative examples of the present invention. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0033] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0034] Polybenzodifuran diketone was purchased from Poly-Rong Optoelectronics (Guangzhou) New Materials Technology Co., Ltd.; Model: HP-H110;

[0035] The nano powder was purchased from Zhongke Keyou.

[0036] Example 1:

[0037] This embodiment provides a method for fabricating a flexible electrode for electronic skin, the specific steps of which are as follows:

[0038] (1) Dissolve 3 g of polybenzodifurandione (PBFDO) in 20 mL of dimethyl sulfoxide (DMSO) to obtain mixture 1;

[0039] (2) Add 5 g of nano silver powder (D50=200 nm) to mixture 1, disperse ultrasonically for 10 min, and stir to obtain mixture 2;

[0040] (3) 4 g of amino-containing oligomeric polyol (manufacturer: PCC Rokita SA, model: Rokopol®RF170) was reacted with 0.78 g of maleic anhydride at 140℃ for 6 h to obtain maleimide-modified oligomeric polyol; 2 g of the obtained maleimide-modified oligomeric polyol was reacted with 1.78 g of isophorone diisocyanate (Shanghai Maclean Biochemical Technology Co., Ltd.) at 70℃ for 2 h to obtain polyurethane prepolymer; 5 g of the obtained polyurethane prepolymer was reacted with 0.72 g of 1,4-butanediol at 80℃ for 2 h to obtain maleimide-modified polyurethane.

[0041] Add 5 g of maleimide-modified polyurethane to mixture 2, stir and react at 60℃ for 12 h to obtain mixture 3;

[0042] (4) Pour the mixture 3 into the mold and dry it in a vacuum oven at 40°C for 12 h to obtain a flexible electrode for electronic skin.

[0043] Example 2:

[0044] This embodiment provides a method for fabricating a flexible electrode for electronic skin, the specific steps of which are as follows:

[0045] (1) Dissolve 3 g of polybenzodifuran dione in 20 mL of DMSO to obtain mixture 1;

[0046] (2) Add 5 g of silver-coated copper nanoparticles (D50=200 nm) to mixture 1, ultrasonically disperse for 10 min, and stir to obtain mixture 2;

[0047] (3) 4 g of amino-containing oligomeric polyol (manufacturer: PCC Rokita SA, model: Rokopol®RF170) was reacted with 0.78 g of maleic anhydride at 140℃ for 6 h to obtain maleimide-modified oligomeric polyol; 2 g of the obtained maleimide-modified oligomeric polyol was reacted with 1.78 g of isophorone diisocyanate (Shanghai Maclean Biochemical Technology Co., Ltd.) at 70℃ for 2 h to obtain polyurethane prepolymer; 5 g of the obtained polyurethane prepolymer was reacted with 0.72 g of 1,4-butanediol at 80℃ for 2 h to obtain maleimide-modified polyurethane.

[0048] Add 5 g of maleimide-modified polyurethane to mixture 2 and stir at 60°C for 12 h to obtain mixture 3;

[0049] (4) Pour the mixture 3 into the mold and dry it in a vacuum oven at 40°C for 12 h to obtain a flexible electrode for electronic skin.

[0050] Example 3:

[0051] This embodiment provides a method for fabricating a flexible electrode for electronic skin, the specific steps of which are as follows:

[0052] (1) Dissolve 4 g of polybenzodifuran dione in 20 mL of DMSO to obtain mixture 1;

[0053] (2) Add 3 g of silver nanoparticles (D50=200 nm) to mixture 1, disperse ultrasonically for 10 min, and stir to obtain mixture 2;

[0054] (3) 4 g of amino-containing oligomeric polyol (manufacturer: PCC Rokita SA, model: Rokopol®RF170) was reacted with 0.78 g of maleic anhydride at 140℃ for 6 h to obtain maleimide-modified oligomeric polyol; 2 g of the obtained maleimide-modified oligomeric polyol was reacted with 1.78 g of isophorone diisocyanate (Shanghai Maclean Biochemical Technology Co., Ltd.) at 70℃ for 2 h to obtain polyurethane prepolymer; 5 g of the obtained polyurethane prepolymer was reacted with 0.72 g of 1,4-butanediol at 80℃ for 2 h to obtain maleimide-modified polyurethane.

[0055] Add 6 g of maleimide-modified polyurethane to mixture 2 and stir at 60°C for 12 h to obtain mixture 3;

[0056] (4) Pour the mixture 3 into the mold and dry it in a vacuum oven at 40°C for 12 h to obtain a flexible electrode for electronic skin.

[0057] Comparative Example 1

[0058] This comparative example provides a method for preparing a conductive film, which is similar to Example 1, except that polybenzodifurandione is not added, while the remaining steps are the same as in Example 1.

[0059] Comparative Example 2

[0060] This comparative example provides a method for preparing a conductive film, which is similar to Example 1, except that no nano-metal powder is added, while the remaining steps are the same as in Example 1.

[0061] Comparative Example 3

[0062] This comparative example provides a method for preparing a conductive film, which is similar to Example 1, except that the maleimide-modified polyurethane is replaced with polyurethane, and the remaining steps are the same as in Example 1.

[0063] Comparative Example 4

[0064] This comparative example provides a method for preparing a conductive film, similar to Example 1, except that: polybenzodifuran dione is replaced with poly(3,4-ethylenedioxythiophene)-poly(sodium styrene sulfonate) (PEDOT:PSS) (purchased from Yake Co., Ltd., model J0066).

[0065] Comparative Example 5

[0066] This comparative example provides a method for preparing a flexible electrode for electronic skin, which is similar to Example 1, except that 0.1 g of polybenzodifuran dione is added, and the remaining steps are the same as in Example 1.

[0067] Performance characterization:

[0068] 1. The change in resistance of the material under tension was tested using a digital precision multimeter in conjunction with a tensile testing machine. The results are as follows: Figure 2 As shown, ΔR / R is the ratio of the difference between the material's resistance and its initial resistance under different strains to the initial resistance.

[0069] 2. The conductivity of the flexible electrode and the conductivity after repeated stretching and shrinking 5000 times (with a fixed stretching deformation of 100%) were tested using a conductivity meter, and the rate of change of conductivity before and after stretching were calculated. The conductivity recovery rate of the film was compared after the cut surfaces were pieced together and placed in a 60℃ oven for 4 h and 24 h.

[0070] The results are shown in Table 1 below:

[0071] Table 1. Conductivity of the Examples and Comparative Examples, rate of change of conductivity after 5000 stretching cycles, and conductivity recovery rate after 4 h and 24 h of piecing the cut surfaces together.

[0072]

[0073] pass Figure 2 As can be seen from Table 1, compared with Examples 1-3, Comparative Examples 1, 4, and 5 have low conductivity, and their conductivity did not recover after 24 hours of piecing the cut surfaces together, indicating a lack of self-healing ability. This is because the system cannot form a synergistic conductive self-healing network when PBFDO is not added, PBFDO is replaced with PEDOT:PSS, or the PBFDO content is low; it relies solely on the random dispersion of nano-metal powder in the modified polyurethane, resulting in low conductivity. Furthermore, the conductivity decreases significantly after repeated stretching, and the resistance increases sharply even with small strain after stretching. Comparative Examples 1, 4, and 5 lack self-healing ability because the system lacks self-healing dynamic DA reversible covalent bonds and multiple hydrogen bonds, making repair impossible.

[0074] Compared with Examples 1-3, Comparative Example 2 exhibits poor conductivity. This is because the lack of nano-metal powder results in a lack of efficient electrical transport medium and interface within the conductive network, leading to reduced conductivity. Furthermore, without the addition of nano-metal powder, energy dissipation is inadequate during stretching, making the conductive network more susceptible to damage. Consequently, Comparative Example 2 shows a significant decrease in conductivity after repeated stretching, and even with relatively small strain after stretching, it exhibits a sharp increase in resistance. Additionally, while Comparative Example 2 possesses self-healing capabilities, the lack of nano-metal powder to match the movement of polymer chain segments significantly reduces the self-healing rate.

[0075] Compared with Examples 1-3, in Comparative Example 3, the unmodified polyurethane used in the system struggles to form a synergistic conductive self-healing network. In this case, the unmodified polyurethane cannot form dynamic DA reversible covalent bonds with PBFDO, the hydrogen bond content is lower than in Example 1, and the self-healing ability is reduced. The unmodified polyurethane cannot form covalent bonds with PBFDO, which reduces the dispersibility of the PBFDO-modified nano-metal powder, making the conductivity worse than in Examples 1-3. The resistance increases sharply even at a lower strain, and the conductivity decreases significantly after repeated stretching compared to Examples 1-3.

[0076] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A flexible electrode for an electronic skin, characterized by, The flexible electrode is composed of polybenzodifuranedione, nano metal powder and maleimide modified polyurethane.

2. The flexible electrode of claim 1, wherein, The maleimide modified polyurethane is prepared by the following steps: reacting an oligomer polyol containing amino group in side chain with maleic anhydride to obtain maleimide modified oligomer polyol; reacting the obtained maleimide modified oligomer polyol with diisocyanate to obtain maleimide modified polyurethane prepolymer; reacting the obtained polyurethane prepolymer with chain extender to obtain the maleimide modified polyurethane.

3. The flexible electrode of claim 2, wherein, The diisocyanate is selected from one or more of isophorone diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, polymethylene polyphenyl isocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and tetramethyl m-xylylene diisocyanate; and / or, the chain extender is selected from one or more of alcohol, amine and alcohol amine.

4. The flexible electrode of claim 1, wherein, The metal component in the nano metal powder is selected from one or more of silver, copper, gold, nickel, tin, aluminum, platinum, chromium, zinc, titanium and tungsten.

5. The flexible electrode of claim 1, wherein The shape of the nano metal powder includes spherical, rod-shaped, flaky or irregular shape.

6. The flexible electrode of claim 1, wherein, The mass ratio of the polybenzodifuranedione to the nano metal powder is 1-5:3-7.

7. The flexible electrode of claim 1, wherein, The mass ratio of the polybenzodifuranedione to the maleimide modified polyurethane is 1-5:2-6.

8. The method of claim 1-7 for the preparation of flexible electrodes for e-skin, characterized in that, comprising the following steps: (1) dissolving polybenzodifuranedione in an organic solvent to obtain mixed solution 1; (2) dispersing nano metal powder in the mixed solution 1 obtained in step (1) to obtain mixed solution 2; (3) preparing maleimide modified polyurethane, adding the obtained maleimide modified polyurethane into the mixed solution 2 obtained in step (2) for reaction, drying to obtain the flexible electrode of electronic skin.

9. The production method according to claim 8, characterized by, In step (1), the organic solvent is one or more of dimethyl sulfoxide, N,N-dimethylformamide and N-methyl pyrrolidone.

10. Use of the flexible electrode of any one of claims 1-7 in electronic skin.

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