Stretchable transparent electrode based on flexible welding and preparation method thereof

Abstract

The invention provides a stretchable transparent electrode based on flexible welding and a preparation method thereof, and belongs to the technical field of transparent electrodes. The preparation method comprises the steps that liquid metal is taken and put into a dispersing agent for ultrasonication, and dispersion liquid A is obtained; adding a silane coupling agent, uniformly dispersing, centrifuging, adding a liquid-phase medium, and carrying out centrifugal washing to obtain a dispersion liquid B; spin-coating the metal nanowire dispersion liquid on a substrate to form a conductive film; sucking the dispersion liquid B, and spin-coating the dispersion liquid B on a conductive thin film; and applying pressure to perform mechanical crushing treatment, and crushing the liquid metal particles so as to wrap the metal nanowire, thereby obtaining the stretchable transparent electrode. According to the stretchable transparent electrode and the preparation method thereof, the liquid metal material is welded at a metal nanowire node by utilizing good and strong effects among the silane coupling agent, the liquid metal and the nano active material, so that the stretchable transparent electrode which is low in square resistance, large in stretching range, good in cycle performance, excellent in working curve linear relation and good in stretching repeatability is prepared.

Description

Technical Field

[0001] This invention belongs to the field of transparent electrode technology, and specifically relates to a stretchable transparent electrode based on flexible welding and its preparation method. Background Technology

[0002] Metal nanowires, as highly promising one-dimensional nanomaterials, possess excellent electrical and thermal conductivity, low surface resistivity, extremely high transparency, flexibility, antibacterial properties, and good biocompatibility. Their fabrication process is also relatively simple. Metal nanowires are finding unique value in fields such as flexible conductive films, sensors, solar cells, and supercapacitors. However, due to the nanoscale gaps between metal nanowires, the junction resistance of the electrodes is detrimental to their conductivity, hindering charge transfer in organic optoelectronic devices and thus reducing device performance.

[0003] Non-patent literature 1 (ACS Appl. Mater. Interfaces, 2017, 9, 34093-34100) reduces junction resistance by providing thermal energy to melt the overlapping metal wires. Localized plasmon resonance at the nanowire junction generates heat, enabling the welding of nanowires and improving their conductivity; however, the welding requires high temperatures. Non-patent literature 2 (ACS Appl. Mater. Interfaces, 2020, 12, 6169-6175) uses Ag foil and AgNW network as counter and working electrodes, respectively, with silver cyanide as a precursor. Electrochemical deposition of the AgNW network is performed at a constant current density; however, the substrate must be corrosion-resistant and heat-resistant. Chinese patent publication CN115798792A discloses a method for preparing a flexible, stretchable, transparent silver nanowire electrode. This invention utilizes seed-induced secondary growth of silver nanowires on the surface of silver nanowires to obtain dendritic silver nanowires. These dendritic silver nanowires can improve the inter-welding and interconnection between the intersections of silver wires, but require an ultraviolet lamp as a light-driven heat source, making the fabrication process complex.

[0004] Therefore, it is challenging to find a method that requires low temperature, has a wide range of substrate requirements, and is easy to manufacture. Summary of the Invention

[0005] Therefore, the present invention aims to provide a stretchable transparent electrode based on flexible welding and a method for preparing the same, in order to solve at least one technical problem in the prior art.

[0006] This invention is implemented as follows: The first aspect of this invention provides a method for fabricating a stretchable transparent electrode based on flexible welding, the method comprising the following steps: S1, take liquid metal and put it into a dispersant and ultrasonically break it to obtain dispersion A. The liquid metal is a metal alloy that maintains a liquid state at room temperature. S2, add silane coupling agent to dispersion A, disperse evenly, centrifuge, then add liquid medium for centrifugation and washing to obtain dispersion B; S3, using a metal nanowire dispersion as dispersion liquid C, spin-coating it onto a substrate to form a conductive film; S4, take out dispersion B, spin coat it onto the conductive film, and flexibly weld the liquid metal to the intersection of the metal nanowires; S5, apply pressure for mechanical crushing, break up the liquid metal particles and then wrap the metal nanowires to obtain a stretchable transparent electrode.

[0007] Preferably, the liquid metal is selected from at least one of gallium-indium alloy, gallium-tin alloy, bismuth-lead alloy, and gallium-indium-tin alloy; According to the mass ratio, in the gallium-indium alloy, gallium:indium = 2~8:1; in the gallium-tin alloy, gallium:tin = 2~8:1; in the bismuth-lead alloy, bismuth:lead = 2~8:1; in the gallium-indium-tin alloy, gallium:indium:tin = (2~8):1:1; In the dispersion A, the concentration of liquid metal ranges from 1 mg / ml to 10 mg / ml, and the dispersant is ethanol, isopropanol, or N-dimethylformamide.

[0008] Preferably, in S1, the ultrasonic fragmentation time is 10 min to 30 min.

[0009] Preferably, in S2, the silane coupling agent is selected from at least one of γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, bis-(γ-triethoxysilylpropyl)tetrasulfide, and bis-[3-(triethoxysilyl)propyl]-disulfide; the amount of the silane coupling agent is 1wt% to 10wt% of the liquid metal.

[0010] Preferably, in step S2, the centrifugal washing rate is 100 rpm to 10,000 rpm and the time is 5 min to 200 min.

[0011] Preferably, in S3 and S4, the spin coating speed is 100rpm~10000rpm and the spin coating time is 5s~300s.

[0012] Preferably, the metal nanowires are selected from at least one of silver nanowires, copper nanowires, iron nanowires, magnesium nanowires, and zinc nanowires, and their aspect ratio is 100 to 4000.

[0013] Preferably, in step S5, the mechanical crushing pressure is 30 Pa to 3000 Pa.

[0014] Preferably, the substrate is made of polydimethylsiloxane, thermoplastic polyurethane, polyvinyl alcohol, polyetheretherketone, polyetherurethane, or polymethyl methacrylate.

[0015] The second aspect of the present invention provides a stretchable transparent electrode prepared by the above-described method for preparing a stretchable transparent electrode based on flexible welding.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes the good and strong interaction between silane coupling agent and liquid metal, and nano-active materials to weld liquid metal materials to metal nanowire nodes, thereby producing a stretchable transparent electrode with low sheet resistance, large stretching range, good cycle performance, excellent linearity of electrode working curve, and good stretching repeatability.

[0017] 2. The liquid metal particles modified with silane coupling agent of this invention accumulate at the intersection of metal nanowires during spin coating, and can form coordination with the metal elements in the metal nanowires, ensuring good contact between the metal nanowires.

[0018] 3. In this invention, after welding liquid metal to the intersection of metal nanowires, a certain pressure needs to be applied. The liquid metal particles break down and wrap around the metal nanowires, achieving a welding effect and reducing the contact resistance of the metal nanowire junctions. Because liquid metal has good liquid properties and high surface tension, it can maintain good connection of the metal nanowires during the stretching process.

[0019] 4. Unlike traditional rigid welding which requires high temperatures, the flexible welding of this invention has low temperature requirements, a wide range of substrate requirements, and a simple manufacturing method.

[0020] 5. The stretchable transparent electrode of the present invention can measure human electrocardiogram and electromyography signals. Attached Figure Description

[0021] Figure 1 This is a physical image of the stretchable transparent electrode prepared in Embodiment 1 of the present invention.

[0022] Figure 2 This is a comparison of the resistance change rate-strain working curves of the stretchable transparent electrode and the silver nanowire electrode prepared in Example 1 of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] Example 1 The method for fabricating a stretchable transparent electrode based on flexible welding includes the following steps: S1, take gallium-indium alloy (gallium:indium = 2:1) and put it into ethanol for ultrasonic disruption for 10 min to obtain dispersion A with a concentration of 1 mg / ml; S2, add 1% γ-mercaptopropyltrimethoxysilane to dispersion A, disperse evenly, centrifuge at 100 rpm for 5 min, then add ethanol and centrifuge and wash to obtain dispersion B; S3, using silver nanowire dispersion (aspect ratio of 100) as dispersion C, spin-coated onto polydimethylsiloxane substrate, and after the solvent has completely evaporated, a conductive film is formed; S4, take dispersion B and spin-coat it (100 rpm spin-coat for 5 s) onto the conductive film, and flexibly weld the liquid metal gallium indium alloy to the intersection of the metal nanowires; the liquid metal particles modified by silane coupling agent accumulate at the intersection of the metal nanowires during the spin-coating process, and can form coordination with the metal elements in the metal nanowires to ensure good contact between the metal nanowires. S5, mechanically crushed for 30 seconds under 30 Pa pressure, yields the following result: Figure 1 The stretchable transparent electrode is shown. Liquid metal welding requires applying pressure after the metal nanowires intersect; the liquid metal particles break down, encapsulating the metal nanowires and achieving a welding effect, thereby reducing the contact resistance of the metal nanowire junctions. Due to the excellent liquid properties and high surface tension of liquid metal, good connectivity of the metal nanowires can be maintained during the stretching process.

[0025] The resistance change rate-strain relationship of the stretchable transparent electrode (SLM-AgNWs) prepared in this embodiment was detected, and compared with that of conventional silver nanowire electrodes (AgNWs). Figure 2 As shown, it can be seen that the resistance of the stretchable transparent electrode (SLM-AgNWs) changes very little under a wide range of stretching, while the resistance of the silver nanowire electrode (AgNWs) changes dramatically when stretched to a strain of 20%~30%, and the rate of resistance change increases significantly.

[0026] Example 2 The method for fabricating a stretchable transparent electrode based on flexible welding includes the following steps: S1, take gallium-tin alloy (gallium:tin = 3:1) and put it into isopropanol and sonicate for 20 min to obtain dispersion A with a concentration of 5 mg / ml; S2, add 5% γ-mercaptopropyltriethoxysilane to dispersion A, disperse evenly, centrifuge at 800 rpm for 15 min, then add isopropanol and centrifuge and wash to obtain dispersion B; S3, using zinc nanowire dispersion (aspect ratio of 2000) as dispersion C, spin-coated onto polyether urethane substrate, and after the solvent has completely evaporated, a conductive film is formed; S4, take dispersion B and spin-coat it (900 rpm spin-coat for 20 s) onto the conductive film, and flexibly weld the liquid metal gallium-tin alloy to the intersection of the metal nanowires; S5, using 225 Pa pressure for mechanical crushing for 60 s, yields a stretchable transparent electrode.

[0027] Example 3 The method for fabricating a stretchable transparent electrode based on flexible welding includes the following steps: S1, take a bismuth-lead alloy (bismuth:lead = 8:1) and put it into nitrogen-nitrogen dimethylformamide and sonicate for 30 min to obtain a dispersion A with a concentration of 8 mg / ml; S2, add 8% bis-(γ-triethoxysilylpropyl)tetrasulfide to dispersion A, disperse evenly, centrifuge at 10000 rpm for 200 min, then add nitrogen-nitrogen dimethylformamide for centrifugation and washing to obtain dispersion B; S3, using copper nanowire dispersion (aspect ratio of 4000) as dispersion C, spin-coated onto polydimethylsiloxane substrate, and after the solvent has completely evaporated, a conductive film is formed; S4, take dispersion B and spin-coat it (10000 rpm spin-coat for 300 s) onto the conductive film, and flexibly weld the liquid metal bismuth-lead alloy to the intersection of the metal nanowires; S5, using 3000 Pa pressure to mechanically crush for 300 s, obtains a stretchable transparent electrode.

[0028] Example 4 The method for fabricating a stretchable transparent electrode based on flexible welding includes the following steps: S1, take gallium indium tin alloy (gallium:indium:tin = 5:1:1) and put it into nitrogen dimethylformamide and sonicate for 15 min to obtain dispersion A with a concentration of 10 mg / ml; S2, add 10% bis-(γ-triethoxysilylpropyl)tetrasulfide to dispersion A, disperse evenly, centrifuge at 1500 rpm for 20 min, then add nitrogen-nitrogen dimethylformamide for centrifugation and washing to obtain dispersion B; S3, using iron nanowire dispersion (aspect ratio of 1000) as dispersion C, spin-coated onto polydimethylsiloxane substrate, and after the solvent has completely evaporated, a conductive film is formed; S4, take dispersion B and spin coat it (1000 rpm spin coat for 50 s) onto the conductive film, and flexibly weld the liquid metal gallium indium tin alloy to the intersection of the metal nanowires; S5, using 1000 Pa pressure to mechanically crush for 100 s, obtains a stretchable transparent electrode.

[0029] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that step S2 is omitted, i.e., the liquid metal is not modified by the silane coupling agent, and S4 is directly spin-coated using dispersion A. All other steps and conditions are the same as in Example 1.

[0030] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that step S5 is omitted, i.e., mechanical crushing under pressure is not performed. All other steps and conditions are the same as in Example 1.

[0031] The sheet resistance, stretchable range, and number of cycles of the stretchable transparent electrodes prepared in Examples 1 to 4, Comparative Examples 1 and 2 are shown in Table 1.

[0032] Table 1

[0033] The stretchable transparent electrode produced by this invention at a low welding temperature (<120 ℃) ​​has low sheet resistance (<50Ω), large stretching range (>90%), good cycle performance (>2000 times), excellent linearity of the electrode's working curve, good stretching repeatability, and can measure human electrocardiogram and electromyography signals.

[0034] Comparing Comparative Example 1 with Example 1, it can be seen that the transparent electrode prepared by liquid metal without modification by silane coupling agent has a significantly increased sheet resistance, a significantly reduced stretching range, and a sharp drop in the number of cycles.

[0035] Comparing Comparative Example 2 with Example 1, it can be seen that without mechanical crushing treatment, the sheet resistance of the transparent electrode increases slightly, the stretching range decreases, and the number of cycles is significantly reduced.

[0036] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for fabricating a stretchable transparent electrode based on flexible welding, characterized in that, The preparation method includes the following steps: S1, take liquid metal and put it into a dispersant and ultrasonically break it to obtain dispersion A. The liquid metal is a metal alloy that maintains a liquid state at room temperature. S2, add silane coupling agent to dispersion A, disperse evenly, centrifuge, then add liquid medium for centrifugation and washing to obtain dispersion B; S3, using a metal nanowire dispersion as dispersion liquid C, spin-coating it onto a substrate to form a conductive film; S4, take out dispersion B, spin coat it onto the conductive film, and flexibly weld the liquid metal to the intersection of the metal nanowires; S5, apply pressure for mechanical crushing, break up the liquid metal particles and then wrap the metal nanowires to obtain a stretchable transparent electrode.

2. The method for preparing a stretchable transparent electrode based on flexible welding according to claim 1, characterized in that, The liquid metal is selected from at least one of gallium-indium alloy, gallium-tin alloy, bismuth-lead alloy, and gallium-indium-tin alloy; According to the mass ratio, in the gallium-indium alloy, gallium:indium = 2~8:1; in the gallium-tin alloy, gallium:tin = 2~8:1; in the bismuth-lead alloy, bismuth:lead = 2~8:1; in the gallium-indium-tin alloy, gallium:indium:tin = (2~8):1:1; In the dispersion A, the concentration of liquid metal ranges from 1 mg / ml to 10 mg / ml, and the dispersant is ethanol, isopropanol, or N-dimethylformamide.

3. The method for preparing a stretchable transparent electrode based on flexible welding according to claim 1, characterized in that, In S1, the ultrasonic fragmentation time is 10 min to 30 min.

4. The method for preparing a stretchable transparent electrode based on flexible welding according to claim 1, characterized in that, In S2, the silane coupling agent is selected from at least one of γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, bis-(γ-triethoxysilylpropyl)tetrasulfide, and bis-[3-(triethoxysilyl)propyl]-disulfide; the amount of the silane coupling agent is 1 wt% to 10 wt% of the liquid metal.

5. The method for preparing a stretchable transparent electrode based on flexible welding according to claim 1, characterized in that, In step S2, the centrifugal washing rate is 100 rpm to 10,000 rpm and the time is 5 min to 200 min.

6. The method for preparing a stretchable transparent electrode based on flexible welding according to claim 1, characterized in that, In S3 and S4, the spin coating speed is 100rpm~10000rpm, and the spin coating time is 5s~300s.

7. The method for preparing a stretchable transparent electrode based on flexible welding according to claim 1, characterized in that, The metal nanowires are selected from at least one of silver nanowires, copper nanowires, iron nanowires, magnesium nanowires, and zinc nanowires, and their aspect ratio is 100 to 4000.

8. The method for preparing a stretchable transparent electrode based on flexible welding according to claim 1, characterized in that, In S5, the mechanical crushing pressure is 30 Pa to 3000 Pa.

9. The method for preparing a stretchable transparent electrode based on flexible welding according to claim 1, characterized in that, The substrate material is polydimethylsiloxane, thermoplastic polyurethane, polyvinyl alcohol, polyetheretherketone, polyetherurethane, or polymethyl methacrylate.

10. The stretchable transparent electrode prepared by the method for preparing a stretchable transparent electrode based on flexible welding according to any one of claims 1 to 9.

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