Liquid metal reinforced triboelectric material with biomimetic surface and preparation method thereof

Abstract

The application discloses a liquid metal reinforced triboelectric material with a biomimetic surface and a preparation method thereof, and belongs to the technical field of triboelectric materials. The liquid metal reinforced triboelectric material is prepared by mixing an interface stabilizer TEMPO oxidized nanocellulose and a liquid metal gallium-indium alloy, obtaining TOCNF@LM liquid metal-based micro-nano droplets, mixing the obtained TOCNF@LM liquid metal-based micro-nano droplets into a water-based polyurethane of a base material, and adopting a template method to construct a biomimetic rose petal micro-papilla structure, so as to obtain the liquid metal reinforced triboelectric material with the biomimetic surface. The composite material with the rose petal micro-nano structure is prepared through biomimetic design, the micro-papilla structure of the rose petal is successfully copied, and the water-based polyurethane is significantly improved in triboelectric performance by using the TOCNF@LM liquid metal-based micro-nano droplets, so that the open-circuit voltage of the prepared composite material reaches 250 V, the short-circuit current reaches 8.19 mu A, and the short-circuit transfer charge reaches 95 nC. The application provides theoretical and practical guidance for the design of high-performance triboelectric materials.

Description

Technical Field

[0001] This invention belongs to the field of triboelectric materials technology, specifically relating to a liquid metal-reinforced triboelectric material with a biomimetic surface and its preparation method. Background Technology

[0002] The core working mechanism of triboelectric materials is based on the synergistic effect between triboelectric charging and electrostatic induction. When two different materials rub against each other, due to the difference in their atomic nuclei's ability to bind electrons, the material with weaker binding ability loses electrons and becomes positively charged, while the material with stronger binding ability gains electrons and becomes negatively charged. Based on this principle, triboelectric nanogenerators (TENGs) are designed as devices that can convert mechanical energy into electrical energy. They achieve charge separation and transfer through the periodic contact and separation process of materials, and convert mechanical energy into electrical energy through electrostatic induction.

[0003] Triboelectric generators (TENGs) typically consist of a triboelectric layer and an electrode layer, exhibiting a relatively simple yet powerful structure. The triboelectric layer, as the key component for triboelectric generation, directly impacts power generation efficiency through its material selection. The electrode layer is responsible for collecting and conducting the generated charge, enabling efficient energy output. Factors influencing the triboelectric performance of TENGs primarily include the inherent properties of the materials, surface conditions, and environmental factors. Specifically, the electronegativity, surface energy, polarity, and the ability of atomic nuclei to bind electrons in different materials affect triboelectric performance. Furthermore, the chemical composition and microstructure of the materials also influence the triboelectric effect. For example, surface modification (such as introducing specific functional groups or roughening treatment) can modulate the triboelectric properties of materials. Notably, even with the same chemical composition, differences in microstructure can lead to different triboelectric behaviors. Increased surface roughness helps increase the effective contact area, enhancing the triboelectric effect and influencing the local electric field distribution, thereby improving the TENG's electrical output performance. Therefore, selecting appropriate material combinations and designing electrodes with specific surface roughness and pattern structures can significantly improve the energy conversion efficiency of TENGs.

[0004] Liquid metals (LMs), such as gallium-indium alloys (GaIn), exhibit significant potential in the fabrication of LM-based triboelectric materials due to their excellent conductivity, fluidity, and flexibility. These materials not only possess good flexibility and tensile properties but also high stability and multifunctionality, enabling superior electrical output and multifunctional integration. Unlike traditional metals, gallium-based LMs can exude droplets and form a continuous conductive network under strain. Their resistance decreases exponentially with mechanical deformation (such as stretching, bending, and compression), exhibiting unique strain-enhanced conductivity. This characteristic makes gallium-based LMs ideal conductive fillers or additives, significantly improving the flexibility, tensile properties, and electrical output performance of triboelectric materials.

[0005] With the rapid development of the Internet of Things (IoT), wearable devices, and intelligent systems, TENG-based self-powered sensors have attracted widespread attention due to their ability to operate without an external power source. However, traditional triboelectric materials still face challenges in practical applications regarding sensitivity, response speed, and output stability. By compositing liquid metal with TEMPO oxidized cellulose nanofiber (TOCNF), the dispersion and stability of the liquid metal in the composite triboelectric material can be effectively improved, thereby enhancing the material's mechanical and electrical properties. Furthermore, combining this with biomimetic structural design will help develop higher-performance self-powered triboelectric sensors to address current technological bottlenecks. Summary of the Invention

[0006] To address the above problems, this invention provides a liquid metal-reinforced triboelectric material with a biomimetic surface and its preparation method. By using TEMPO-oxidized cellulose nanoparticles as an interface stabilizer between a liquid gallium-indium alloy and a waterborne polyurethane substrate, and combining this with a template method to construct a biomimetic rose petal micropapillary structure, a liquid metal-reinforced triboelectric material with a biomimetic surface is obtained. This composite material exhibits high triboelectric output performance and sensing sensitivity.

[0007] This invention is achieved through the following technical solution:

[0008] A biomimetic liquid metal-reinforced triboelectric material is obtained by mixing the interface stabilizer TEMPO oxidized cellulose nanoparticles with liquid metal gallium indium alloy to obtain TOCNF@LM liquid metal-based micro / nano droplets; the obtained TOCNF@LM liquid metal-based micro / nano droplets are incorporated into an aqueous polyurethane substrate, and a biomimetic rose petal micro-papillary structure is constructed using a template method to obtain a biomimetic liquid metal-reinforced triboelectric material with a biomimetic surface.

[0009] Furthermore, the open-circuit voltage of the liquid metal-reinforced triboelectric material with a biomimetic surface is 240–250 V, the short-circuit current is 8.0–8.19 μA, and the short-circuit transferred charge is 90–95 nC.

[0010] Furthermore, the zeta potential of the TOCNF@LM liquid metal-based micro / nano droplet is -38.0 to -39.6 mV, and no precipitation occurs after standing for 40 days.

[0011] A method for preparing a liquid metal-reinforced triboelectric material with a biomimetic surface as described above includes the following steps:

[0012] (1) Liquid metal gallium indium alloy was added to the TEMPO oxidized nanocellulose suspension and then ultrasonically pulverized in an ultrasonic cell disruptor to obtain TOCNF@LM liquid metal-based micro-nano droplets;

[0013] (2) TOCNF@LM liquid metal-based micro / nano liquid was added to aqueous polyurethane and magnetically stirred at room temperature to obtain a uniform suspension of TOCNF@LM-WPU;

[0014] (3) Select fresh rose petals, rinse them with water, blow them dry with nitrogen, and then dry them to obtain dried petals; take liquid polydimethylsiloxane, defoam it under vacuum, place the dried petals flat on the liquid polydimethylsiloxane, and then place them in a forced-air drying oven for a first curing. After curing, remove the petals to obtain a polydimethylsiloxane inverse template; pour a uniform suspension of TOCNF@LM-WPU onto the polydimethylsiloxane inverse template, defoam it under vacuum, and then place it in a forced-air drying oven for a second curing. After curing, peel off the polydimethylsiloxane inverse template to obtain a liquid metal reinforced triboelectric material with a biomimetic surface.

[0015] Further, in step (1), the mass ratio of the TEMPO oxidized cellulose nanoparticle suspension to the gallium indium alloy is 1:(0.002~0.02); the mass fraction of the TEMPO oxidized cellulose nanoparticle suspension is 0.5~2wt%.

[0016] Further, in step (1), the conditions for ultrasonic pulverization are: ultrasonic time 5-15 min, ultrasonic interval (1-2) s / 1s, and ultrasonic power 65-455 W.

[0017] Further, in step (2), the mass ratio of the TOCNF@LM liquid metal-based micro / nano droplets to the aqueous polyurethane is 1:(0.5-2); the mass fraction of gallium-indium alloy in the TOCNF@LM-WPU uniform suspension is 0.1-1wt%.

[0018] Furthermore, in step (2), the magnetic stirring time is 0.5 to 1 hour.

[0019] Furthermore, in step (3), the temperature of the first curing is 60-70°C and the time is 2-3 hours.

[0020] Furthermore, in step (3), the temperature of the secondary curing is 40-50°C and the time is 10-12 hours.

[0021] The preparation principle of the biomimetic surface-reinforced liquid metal triboelectric material of the present invention:

[0022] (1) TEMPO oxidized nanocellulose and liquid metal gallium indium alloy are mixed. The surface of TEMPO oxidized nanocellulose is rich in functional groups such as carboxyl groups. By ultrasonic crushing, the carboxyl groups on the surface of TEMPO oxidized nanocellulose are physically adsorbed with the surface of gallium indium alloy and form coordination bonds to construct a stable adsorption layer, thereby improving the dispersibility and stability of gallium indium alloy in composite material and obtaining TOCNF@LM liquid metal-based micro-nano droplets with core-shell structure.

[0023] (2) When TOCNF@LM liquid metal-based micro / nanodroplets are added to aqueous polyurethane, hydrogen bonds are formed between the carboxyl hydrogen atoms on the surface of the TOCNF@LM liquid metal-based micro / nanodroplets and the nitrogen atoms on the urethane groups in the aqueous polyurethane, causing a redistribution of electron cloud density. The formation of these hydrogen bonds significantly enhances the interfacial interaction between TEMPO oxidized nanocellulose and aqueous polyurethane, effectively improving the dispersibility of TOCNF@LM liquid metal-based micro / nanodroplets in the aqueous polyurethane matrix. The uniform dispersion of TOCNF@LM liquid metal-based micro / nanodroplets not only promotes efficient charge transfer and accumulation during friction but also reduces charge leakage caused by material defects or structural inhomogeneities, thereby improving the triboelectric output performance of the composite material.

[0024] (3) The microstructure of rose petals was transferred using polydimethylsiloxane. The resulting polydimethylsiloxane inverse template surface and pit sidewalls showed a large number of wrinkles. Using this polydimethylsiloxane inverse template, a liquid metal-reinforced triboelectric material with a biomimetic surface was prepared. The micro-nano structure of this material surface was highly similar to the micro-papillary structure of rose petals in size and morphology, successfully simulating the typical micro-nano structure characteristics in nature. This micro-nano structure enhances the triboelectric properties of the material in two ways: on the one hand, the micro-papillary structure significantly increases the effective contact area, promotes more intermolecular interactions, and improves charge transfer efficiency; on the other hand, during the contact separation process, the multi-level micro-papillary structure can provide more charge polarization paths, which is conducive to the accumulation and separation of charges at the interface, thereby more effectively inducing charge polarization.

[0025] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0026] 1. This invention utilizes biomimetic design to fabricate a composite material with a rose petal-like micro / nano structure, successfully replicating the micro-papillary structure of a rose petal. Furthermore, the use of TOCNF@LM liquid metal-based micro / nano droplets significantly enhances the triboelectric properties of waterborne polyurethane, resulting in an open-circuit voltage of 250V, a short-circuit current of 8.19μA, and a short-circuit charge transfer of 95nC for the prepared composite material. The sensor fabricated based on this material achieves a peak power density of 1100.3 mW / m². 2Furthermore, it exhibits excellent stability and rapid response capabilities in 1000-cycle testing, with a response time of 30ms and a recovery time of 15ms. Simultaneously, the material possesses low dielectric loss and excellent tensile properties. This invention provides theoretical and practical guidance for the design of high-performance triboelectric materials, promoting their application in the field of flexible electronics.

[0027] 2. This invention prepared uniformly dispersed TOCNF@LM liquid metal-based micro / nanodroplets that maintained dispersion stability. By using an ultrasonic process, TEMPO-oxidized cellulose nanoparticles rich in carboxyl groups were introduced onto the surface of liquid metal, successfully preparing core-shell structured TOCNF@LM liquid metal-based micro / nanodroplets. The two components were formed through physical adsorption and coordination bonds. The TOCNF@LM liquid metal-based micro / nanodroplets exhibited a Zeta potential of -39.6 mV, demonstrating good dispersibility and stability, and showed no significant precipitation after standing for 40 days.

[0028] 3. This invention mixes TOCNF@LM liquid metal-based micro / nano droplets with aqueous polyurethane and uses a template method to design a liquid metal-reinforced triboelectric material with a biomimetic surface, solving the problem of balancing flexibility and triboelectric properties in existing elastomer materials. Based on the excellent triboelectric properties of this biomimetic liquid metal-reinforced triboelectric material, a highly sensitive self-powered triboelectric sensor was developed, enabling precise sensing of changes in the sensor's state. Attached Figure Description

[0029] Figure 1 The image shows the Zeta potential diagrams of liquid metal and TOCNF@LM liquid metal-based micro / nano droplets in Example 2.

[0030] Figure 2 The images show optical images of the sedimentation experiment of liquid metal and TOCNF@LM liquid metal-based micro / nano droplets in Example 2. The upper image shows the optical image of liquid metal at different times, and the lower image shows the optical image of TOCNF@LM liquid metal-based micro / nano droplets at different times.

[0031] Figure 3 The images shown are cross-sectional SEM images of TLW-0, TLW-0.1, TLW-0.5, and TLW-1 in Comparative Example 2 and Examples 1-3, where (a) is the SEM image of TLW-0, (b) is the SEM image of TLW-0.1, (c) is the SEM image of TLW-0.5, and (d) is the SEM image of TLW-1.

[0032] Figure 4 The FT-IR spectra of TLW-0, TLW-0.1, TLW-0.5, and TLW-1 in Comparative Example 2 and Examples 1-3 are shown, where (a) is the FT-IR spectrum in the wavenumber range of 500–4000 cm⁻¹.-1 (b) shows the FT-IR spectra in the wavenumber range of 1400–1800 cm⁻¹. -1 FT-IR spectra.

[0033] Figure 5 The UV-Vis spectra of TLW-0, TLW-0.1, TLW-0.5, and TLW-1 in Comparative Example 2 and Examples 1-3 are shown.

[0034] Figure 6 The diagrams show the open-circuit voltage, short-circuit current, and short-circuit transferred charge of TLW-flat and TLW-0.5 in Comparative Example 1 and Example 2, where (a) is the open-circuit voltage diagram, (b) is the short-circuit current diagram, and (c) is the short-circuit transferred charge diagram.

[0035] Figure 7 The open-circuit voltage, short-circuit voltage, and output power density diagrams are obtained for preparing the TLW-0.5 in Example 2 as a self-powered sensor based on TLW-TENG.

[0036] Figure 8 The sensitivity and output stability diagrams of the TLW-0.5 in Example 2 were prepared as a self-powered sensor based on TLW-TENG, where (a) is the response and recovery time test diagram and (b) is the output stability test diagram.

[0037] Figure 9 The dielectric constant and dielectric loss diagrams for TLW-0, TLW-0.1, TLW-0.5, and TLW-1 in Comparative Example 2 and Examples 1-3 are shown, where (a) is the dielectric constant diagram and (b) is the dielectric loss diagram.

[0038] Figure 10 The stress-strain curves, Young's modulus and toughness diagrams of TLW-0, TLW-0.1, TLW-0.5 and TLW-1 in Comparative Example 2 and Examples 1-3 are shown, where (a) is the stress-strain curve and (b) is the Young's modulus and toughness diagram. Detailed Implementation

[0039] The present invention will be further described in detail below through embodiments. These embodiments are only used to illustrate the present invention and do not limit the scope of protection of the present invention.

[0040] Example 1

[0041] Preparation of liquid metal-reinforced triboelectric materials with biomimetic surfaces:

[0042] (1) Take 19.8g of TEMPO oxidized nanocellulose (TOCNF) suspension with a mass fraction of 1wt% (using water as solvent), add 0.04g of liquid metal (LM) gallium indium alloy, and then place it in an ultrasonic cell disruptor (setting parameters: ultrasonic interval time 1s / 1s, ultrasonic power 195W, ultrasonic duration 10min) to allow TEMPO oxidized nanocellulose and gallium indium alloy to generate ultrasonic cavitation in an ice-water bath to obtain TOCNF@LM liquid metal-based micro-nano droplets.

[0043] (2) 19.84g of TOCNF@LM liquid metal-based micro-nano liquid was added to 19.84g of waterborne polyurethane (WPU) and magnetically stirred for 1h at room temperature to obtain a uniform suspension of TOCNF@LM-WPU (the mass fraction of gallium indium alloy is 0.1wt%).

[0044] (3) Select 4 fresh rose petals, rinse the surface of the petals to remove impurities, blow dry with nitrogen, and then put them into a forced-air drying oven to dry at 40℃ for 12h to remove moisture, thus obtaining dried petals. Take 48g of liquid polydimethylsiloxane, defoam under vacuum for 30min, place the dried petals flat on the liquid polydimethylsiloxane, and then place them in a forced-air drying oven to cure at 70℃ for 2h. After curing, remove the petals and clean the residual petal fragments on the surface with anhydrous ethanol and deionized water for 15min respectively, thus obtaining a polydimethylsiloxane inverse template. Pour a uniform suspension of TOCNF@LM-WPU onto the polydimethylsiloxane inverse template, defoam under vacuum for 30min, and then place it in a forced-air drying oven to cure at 50℃ for 10h. After curing, peel off the polydimethylsiloxane inverse template to obtain a liquid metal-reinforced triboelectric material with a biomimetic surface (denoted as TLW-0.1).

[0045] Example 2

[0046] Preparation of liquid metal-reinforced triboelectric materials with biomimetic surfaces:

[0047] (1) Take 19.8g of TEMPO oxidized nanocellulose (TOCNF) suspension with a mass fraction of 1wt% (using water as solvent), add 0.2g of liquid metal (LM) gallium indium alloy, and then place it in an ultrasonic cell disruptor (setting parameters: ultrasonic interval time 1s / 1s, ultrasonic power 195W, ultrasonic duration 10min) to allow TEMPO oxidized nanocellulose and gallium indium alloy to generate ultrasonic cavitation in an ice-water bath to obtain TOCNF@LM liquid metal-based micro-nano droplets.

[0048] (2) 20g of TOCNF@LM liquid metal-based micro-nano liquid was added to 20g of waterborne polyurethane (WPU) and magnetically stirred for 1h at room temperature to obtain a uniform suspension of TOCNF@LM-WPU (the mass fraction of gallium indium alloy is 0.5wt%).

[0049] (3) Select 4 fresh rose petals, rinse the surface of the petals to remove impurities, blow dry with nitrogen, and then put them into a forced-air drying oven to dry at 40℃ for 12h to remove moisture, thus obtaining dried petals. Take 48g of liquid polydimethylsiloxane, defoam under vacuum for 30min, place the dried petals flat on the liquid polydimethylsiloxane, and then place them in a forced-air drying oven to cure at 70℃ for 2h. After curing, remove the petals and clean the residual petal fragments on the surface with anhydrous ethanol and deionized water for 15min respectively, thus obtaining a polydimethylsiloxane inverse template. Pour a uniform suspension of TOCNF@LM-WPU onto the polydimethylsiloxane inverse template, defoam under vacuum for 30min, and then place it in a forced-air drying oven to cure at 50℃ for 10h. After curing, peel off the polydimethylsiloxane inverse template to obtain a liquid metal-reinforced triboelectric material with a biomimetic surface (denoted as TLW-0.5).

[0050] Example 3

[0051] Preparation of liquid metal-reinforced triboelectric materials with biomimetic surfaces:

[0052] (1) Take 19.8g of TEMPO oxidized nanocellulose (TOCNF) suspension with a mass fraction of 1wt% (using water as solvent), add 0.4g of liquid metal (LM) gallium indium alloy, and then place it in an ultrasonic cell disruptor (setting parameters: ultrasonic interval time 1s / 1s, ultrasonic power 195W, ultrasonic duration 10min) to allow TEMPO oxidized nanocellulose and gallium indium alloy to generate ultrasonic cavitation in an ice-water bath to obtain TOCNF@LM liquid metal-based micro-nano droplets.

[0053] (2) 20.2g of TOCNF@LM liquid metal-based micro-nano liquid was added to 19.8g of waterborne polyurethane (WPU) and magnetically stirred for 1h at room temperature to obtain a uniform suspension of TOCNF@LM-WPU (the mass fraction of gallium indium alloy is 1wt%).

[0054] (3) Select 4 fresh rose petals, rinse the surface of the petals to remove impurities, blow dry with nitrogen, and then place them in a forced-air drying oven at 40℃ for 12 hours to remove moisture, thus obtaining dried petals. Take 48g of liquid polydimethylsiloxane, defoam under vacuum for 30 minutes, place the dried petals flat on the liquid polydimethylsiloxane, and then place them in a forced-air drying oven at 70℃ for 2 hours to cure. After curing, remove the petals and clean the residual petal fragments on the surface with anhydrous ethanol and deionized water for 15 minutes respectively, thus obtaining a polydimethylsiloxane inverse template. Pour a uniform suspension of TOCNF@LM-WPU onto the polydimethylsiloxane inverse template, defoam under vacuum for 30 minutes, and then place it in a forced-air drying oven at 50℃ for 10 hours to cure. After curing, peel off the polydimethylsiloxane inverse template to obtain a liquid metal-reinforced triboelectric material with a biomimetic surface (denoted as TLW-1).

[0055] Example 4

[0056] Preparation of liquid metal-reinforced triboelectric materials with biomimetic surfaces:

[0057] (1) Take 19.8g of TEMPO oxidized nanocellulose (TOCNF) suspension with a mass fraction of 0.5wt% (using water as solvent), add 0.04g of liquid metal (LM) gallium indium alloy, and then place it in an ultrasonic cell disruptor (setting parameters: ultrasonic interval time 1s / 1s, ultrasonic power 65W, ultrasonic duration 5min) to generate ultrasonic cavitation between TEMPO oxidized nanocellulose and gallium indium alloy in an ice-water bath to obtain TOCNF@LM liquid metal-based micro-nano droplets.

[0058] (2) 19.84g of TOCNF@LM liquid metal-based micro-nano liquid was added to 9.92g of waterborne polyurethane (WPU) and magnetically stirred at room temperature for 0.5h to obtain a uniform suspension of TOCNF@LM-WPU (the mass fraction of gallium indium alloy is 0.134wt%).

[0059] (3) Select 4 fresh rose petals, rinse the surface of the petals to remove impurities, blow dry with nitrogen, and then put them into a forced-air drying oven to dry at 40℃ for 12h to remove moisture, thus obtaining dried petals. Take 48g of liquid polydimethylsiloxane, vacuum defoam for 30min, place the dried petals flat on the liquid polydimethylsiloxane, and then place them in a forced-air drying oven to cure at 60℃ for 2h. After curing, remove the petals, and ultrasonically clean the residual petal fragments on the surface with anhydrous ethanol and deionized water for 15min respectively, thus obtaining a polydimethylsiloxane inverse template. Pour TOCNF@LM-WPU uniform suspension onto the polydimethylsiloxane inverse template, vacuum defoam for 30min, and then place it in a forced-air drying oven to cure at 40℃ for 10h. After curing, peel off the polydimethylsiloxane inverse template to obtain a liquid metal reinforced triboelectric material with a biomimetic surface (denoted as TLW-0.134).

[0060] Example 5

[0061] Preparation of liquid metal-reinforced triboelectric materials with biomimetic surfaces:

[0062] (1) Take 19.8g of TEMPO oxidized nanocellulose (TOCNF) suspension with a mass fraction of 2wt% (using water as solvent), add 0.4g of liquid metal (LM) gallium indium alloy, and then place it in an ultrasonic cell disruptor (setting parameters: ultrasonic interval time 2s / 1s, ultrasonic power 455W, ultrasonic duration 15min) to allow TEMPO oxidized nanocellulose and gallium indium alloy to generate ultrasonic cavitation in an ice-water bath to obtain TOCNF@LM liquid metal-based micro-nano droplets.

[0063] (2) 20.2g of TOCNF@LM liquid metal-based micro-nano liquid was added to 40.4g of waterborne polyurethane (WPU) and magnetically stirred for 1h at room temperature to obtain a uniform suspension of TOCNF@LM-WPU (the mass fraction of gallium indium alloy is 0.66wt%).

[0064] (3) Select 4 fresh rose petals, rinse the surface of the petals to remove impurities, blow dry with nitrogen, and then put them into a forced-air drying oven to dry at 40℃ for 12h to remove moisture, thus obtaining dried petals. Take 48g of liquid polydimethylsiloxane, defoam under vacuum for 30min, place the dried petals flat on the liquid polydimethylsiloxane, and then place them in a forced-air drying oven to cure at 70℃ for 3h. After curing, remove the petals and clean the residual petal fragments on the surface with anhydrous ethanol and deionized water for 15min respectively, thus obtaining a polydimethylsiloxane inverse template. Pour a uniform suspension of TOCNF@LM-WPU onto the polydimethylsiloxane inverse template, defoam under vacuum for 30min, and then place it in a forced-air drying oven to cure at 50℃ for 12h. After curing, peel off the polydimethylsiloxane inverse template to obtain a liquid metal-reinforced triboelectric material with a biomimetic surface (denoted as TLW-0.66).

[0065] Comparative Example 1

[0066] Preparation of smooth surface liquid metal reinforced triboelectric materials:

[0067] (1) Take 19.8g of TEMPO oxidized nanocellulose (TOCNF) suspension with a mass fraction of 1wt% (using water as solvent), add 0.2g of liquid metal (LM) gallium indium alloy, and then place it in an ultrasonic cell disruptor (setting parameters: ultrasonic interval time 1s / 1s, ultrasonic power 195W, ultrasonic duration 10min) to allow TEMPO oxidized nanocellulose and gallium indium alloy to generate ultrasonic cavitation in an ice-water bath to obtain TOCNF@LM liquid metal-based micro-nano droplets.

[0068] (2) 20g of TOCNF@LM liquid metal-based micro-nano liquid was added to 20g of waterborne polyurethane (WPU) and magnetically stirred for 1h at room temperature to obtain a uniform suspension of TOCNF@LM-WPU (the mass fraction of gallium indium alloy is 0.5wt%).

[0069] (3) Pour TOCNF@LM-WPU uniform suspension into the polytetrafluoroethylene mold, defoam under vacuum for 30 min, and then place it in a forced-air drying oven to cure at 50°C for 10 h. After curing, remove the polytetrafluoroethylene mold to obtain a smooth surface liquid metal reinforced triboelectric material (denoted as TLW-flat).

[0070] Comparative Example 2

[0071] Preparation of common triboelectric materials with biomimetic surfaces:

[0072] (1) Take 20g of TEMPO oxidized nanocellulose (TOCNF) suspension with a mass fraction of 1wt% (using water as solvent) and place it in an ultrasonic cell disruptor (setting parameters: ultrasonic interval time 1s / 1s, ultrasonic power 195W, ultrasonic duration 10min) to obtain the ultrasonically prepared TOCNF suspension.

[0073] (2) Add 20g of the ultrasonically treated TOCNF suspension to 20g of waterborne polyurethane (WPU) and stir magnetically for 1h at room temperature to obtain a uniform TOCNF-WPU suspension.

[0074] (3) Select 4 fresh rose petals, rinse the surface of the petals to remove impurities, blow dry with nitrogen, and then place them in a forced-air drying oven at 40℃ for 12 hours to remove moisture, thus obtaining dried petals. Take 48g of liquid polydimethylsiloxane, defoam under vacuum for 30 minutes, place the dried petals flat on the liquid polydimethylsiloxane, and then place them in a forced-air drying oven at 70℃ for 2 hours to cure. After curing, remove the petals and clean the residual petal fragments on the surface with anhydrous ethanol and deionized water for 15 minutes respectively, thus obtaining a polydimethylsiloxane inverse template. Pour a uniform suspension of TOCNF@LM-WPU onto the polydimethylsiloxane inverse template, defoam under vacuum for 30 minutes, and then place it in a forced-air drying oven at 50℃ for 10 hours to cure. After curing, peel off the polydimethylsiloxane inverse template to obtain a common triboelectric material with a biomimetic surface (denoted as TLW-0).

[0075] Material characterization analysis

[0076] (I) Analysis of Zeta potential and optical images

[0077] Zeta potential is an important indicator for evaluating the dispersion stability of suspensions. The Zeta potentials of the liquid metal and TOCNF@LM liquid metal-based micro / nano droplets in Example 2 were analyzed, and the results are as follows: Figure 1 As shown.

[0078] Depend on Figure 1 It is known that the Zeta potential of liquid metal is 5.6 mV, while that of TOCNF@LM liquid metal-based micro / nanodroplets is -39.6 mV. A higher absolute value of the Zeta potential indicates a greater surface charge and stronger electrostatic repulsion between particles, resulting in a more stable system. Therefore, the higher absolute value of the Zeta potential in TOCNF@LM liquid metal-based micro / nanodroplets suggests that the introduction of TEMPO-oxidized nanocellulose significantly enhances the electrostatic repulsion of the system, thereby improving its dispersion stability.

[0079] The stability of the liquid metal and TOCNF@LM liquid metal-based micro / nanodroplets in Example 2 was investigated through sedimentation experiments. In the experiments, deionized water was added to the liquid metal, and then both the liquid metal and the TOCNF@LM liquid metal-based micro / nanodroplets were placed in sealed glass bottles and stored at room temperature for an extended period to simulate their stability under real-world application conditions. The results are as follows: Figure 2 As shown. Figure 2 The top image shows optical images of liquid metal at different times, while the bottom image shows optical images of TOCNF@LM liquid metal-based micro / nano droplets at different times.

[0080] Depend on Figure 2 It was observed that precipitation began to occur 6 hours after the addition of deionized water to the liquid metal, and the precipitation rate was relatively fast. After one day, the gallium-indium alloy in the system almost completely sank to the bottom of the bottle, indicating poor stability and unfavorable conditions for subsequent composite dispersion with the polymer matrix. In contrast, the TOCNF@LM liquid metal-based micro / nanodroplets exhibited a significant stability advantage. Even after 40 days of static storage, the suspension did not show obvious precipitation, and the uniformity of its dispersion system was maintained for a long period. This result indicates that the introduction of TEMPO-oxidized nanocellulose significantly enhances the stability of the gallium-indium alloy, effectively suppresses droplet sedimentation behavior, and provides strong experimental evidence for its long-term stability in practical applications.

[0081] (II) SEM Analysis

[0082] Scanning electron microscopy (SEM) was used to characterize and analyze TLW-0, TLW-0.1, TLW-0.5, and TLW-1 in Comparative Example 2 and Examples 1-3. The results are as follows: Figure 3 As shown. Figure 3 In the image, (a), (b), (c), and (d) are SEM images of TLW-0, TLW-0.1, TLW-0.5, and TLW-1, respectively.

[0083] Depend on Figure 3 It can be seen that the distribution of TOCNF@LM liquid metal-based micro / nano droplets differs depending on the gallium-indium alloy content. In the figure, the black area represents the aqueous polyurethane matrix, while the white dots represent TOCNF@LM liquid metal-based micro / nano droplets. Figure 3 (b) It can be seen that the number of TOCNF@LM liquid metal-based micro / nano droplets in TLW-0.1 is relatively small and the distribution is sparse; Figure 3 (c) It can be seen that the TOCNF@LM liquid metal-based micro / nano droplets in TLW-0.5 are densely distributed and relatively uniformly dispersed; Figure 3(d) It can be seen that the number of TOCNF@LM liquid metal-based micro-nano droplets in TLW-1 is dense, but some agglomeration occurs. This distribution difference can have a significant impact on the performance of the composite material.

[0084] (III) FT-IR spectral analysis

[0085] Fourier transform infrared spectroscopy (FT-IR) was used to characterize and analyze TLW-0, TLW-0.1, TLW-0.5, and TLW-1 in Comparative Example 2 and Examples 1-3. The results are as follows: Figure 4 As shown. Figure 4 In the figure, (a) and (b) show the wavenumbers of the materials in the range of 500–4000 cm⁻¹, respectively. -1 1400-1800cm -1 FT-IR spectra.

[0086] Since the characteristic peaks of each material are located in the range of 1400–1800 cm⁻¹ -1 Within the wavenumber range, the focus is on Figure 4 (b) Conduct the analysis. From Figure 4 (b) It can be seen that at 3337cm -1 The absorption peak at 1683 cm⁻¹ corresponds to the stretching vibration of the NH bond in the urethane ester in waterborne polyurethane. -1 The absorption peak at [location] corresponds to the C=O stretching vibration. The results indicate that hydrogen bonds are formed between the hydrogen atoms of the carboxyl groups on the surface of the TOCNF@LM liquid metal-based micro / nanodroplets and the nitrogen atoms of the urethane groups in the aqueous polyurethane. The formation of hydrogen bonds typically shifts the stretching vibration frequency to lower wavenumbers. This hydrogen bond formation significantly enhances the interfacial interaction between TEMPO oxidized nanocellulose and the aqueous polyurethane. This improved interfacial interaction helps improve the dispersibility of the TOCNF@LM liquid metal-based micro / nanodroplets in the aqueous polyurethane matrix. When the TOCNF@LM liquid metal-based micro / nanodroplets are better dispersed in the aqueous polyurethane matrix, the overall performance of the composite material is also improved.

[0087] (iv) Ultraviolet-Visible Spectroscopy Analysis

[0088] The TLW-0, TLW-0.1, TLW-0.5, and TLW-1 samples from Comparative Example 2 and Examples 1-3 were characterized and analyzed using ultraviolet-visible spectroscopy. The results are as follows: Figure 5 As shown. By Figure 5It can be seen that the maximum absorption peak of TLW-0 is at 288 nm, while the maximum absorption peak of TLW-0.1, TLW-0.5, and TLW-1, which contain TOCNF@LM liquid metal-based micro / nanodroplets, is at 287 nm, indicating a shift in absorption peaks. Simultaneously, the absorption intensity decreases with increasing amounts of TOCNF@LM liquid metal-based micro / nanodroplets. The shift in absorption peaks is generally related to the strength of intermolecular interactions, while the change in absorption intensity is related to the range and extent of these interactions. Both the shift in absorption peaks and the decrease in absorption intensity indicate that intermolecular forces are generated between the TOCNF@LM liquid metal-based micro / nanodroplets and the aqueous polyurethane, and hydrogen bonds are formed between urethane or urea groups and carboxyl groups, leading to a redistribution of electron cloud density. This spectral shift provides strong evidence for the formation of the composite structure.

[0089] Material performance testing and analysis

[0090] (I) Triboelectric Performance Testing and Analysis

[0091] The triboelectric properties of TLW-flat and TLW-0.5 in Comparative Example 1 and Example 2 were tested and analyzed, and the results are as follows: Figure 6 As shown. Figure 6 In the diagram, (a), (b), and (c) represent the open-circuit voltage, short-circuit current, and short-circuit transferred charge, respectively.

[0092] Depend on Figure 6 As shown in Figures (a), (b), and (c), the open-circuit voltage, short-circuit current, and short-circuit transferred charge of TLW-0.5 are 250V, 8.19μA, and 95nC, respectively. Compared with TLW-flat, these values ​​represent increases of 19.05%, 37.42%, and 35.71%, respectively. This demonstrates that the transfer of a rose petal-like micro-papillary structure onto the composite material surface was successfully achieved through the use of a polydimethylsiloxane inverse template. This unique micro / nano structure on the petal surface not only imparts hydrophobicity to the material but also significantly enhances its triboelectric properties.

[0093] The TLW-0.5 from Example 2 was fabricated into a self-powered sensor based on TLW-TENG. The open-circuit voltage and short-circuit current were tested under different load resistance conditions, and the output power density was calculated using a formula. The results are as follows: Figure 7 As shown. By Figure 7 It can be seen that the sensor has a low output power density under low resistance load, while the output power density gradually increases under high resistance load; at 10 8 At a load resistance of Ω, 1100.3mW / m was obtained. 2 The peak power density indicates that TENGs sensors can efficiently convert mechanical energy into electrical energy, achieving self-powered operation without the need for an external power source.

[0094] The TLW-0.5 from Example 2 was fabricated into a self-powered sensor based on TLW-TENG. A high-speed data acquisition system was used to accurately measure the response time and recovery time. The results are as follows: Figure 8 As shown. Figure 8 In the figure, (a) is the response and recovery time test graph of the TLW-TENG sensor, and (b) is the output stability test graph of the TLW-TENG sensor.

[0095] Figure 8 In (a), the TLW-TENG sensor was placed in a controlled mechanical excitation environment, and periodic pressure changes were applied to simulate dynamic stimulation in a real-world application scenario. By recording the changes in the sensor's electrical signal during pressure loading and unloading, the response time from the start of the pressure change to the sensor's output signal reaching a steady state, and the recovery time from the signal peak to the baseline level were measured. The test results show that the TLW-TENG sensor has a response time of 30 ms and a recovery time of 15 ms. This excellent response speed makes it valuable for applications in real-time monitoring and high-precision detection. Furthermore, output stability is a key indicator for evaluating energy harvesting devices. Therefore, the TLW-TENG sensor underwent 1000 working cycle tests at a fixed frequency of 2 Hz, and the results are as follows: Figure 8 As shown in (b), the voltage output of the TLW-TENG sensor remained almost constant over 1000 contact-separation cycles, with only a 1.29% difference in output signal between the initial and final detection periods, demonstrating excellent stability and reliability. This indicates that TLW-0.5 material is an ideal choice for constructing self-powered sensors.

[0096] (II) Dielectric property testing and analysis

[0097] The liquid metal content has a significant impact on the dielectric properties of composite materials. The dielectric constant reflects the degree of polarization of a material under the influence of an electric field, i.e., the material's ability to redistribute charges. Materials with high dielectric constants are more easily polarized in an electric field, thus storing more electrical energy. Dielectric property tests and analyses were performed on TLW-0, TLW-0.1, TLW-0.5, and TLW-1 from Comparative Example 2 and Examples 1-3. The results are as follows: Figure 9 As shown. Figure 9 In the diagram, (a) is the dielectric constant diagram and (b) is the dielectric loss diagram.

[0098] Depend on Figure 9(a) It is evident that TLW-0.5 exhibits the best dielectric constant. Insufficient or excessive liquid metal content will decrease the dielectric constant of the composite material. TLW-0.1 suffers from insufficient polarization capability, reducing the effective polarization components in the material and lowering the overall polarization degree; uneven charge distribution means that a small amount of liquid metal may not be able to form an effective polarization network, resulting in insufficient constraint force during charge redistribution within the film, leading to poor polarization and a low dielectric constant. TLW-1 produces a charge shielding effect; excessive liquid metal content leads to the formation of too many conductive channels or localized charge accumulation regions within the composite material. These regions shield the effect of the applied electric field, reducing the overall polarization degree of the material; microstructural defects exist; excessive liquid metal may disrupt the uniformity of the composite material, leading to defects or discontinuities in the microstructure, affecting the normal charge distribution and polarization process, resulting in a decrease in the overall dielectric constant.

[0099] Depend on Figure 9 (b) It is evident that the dielectric loss of the composite material gradually decreases with increasing liquid metal content. This is mainly because the high conductivity of the liquid metal may reduce the conductivity loss of the composite material, thereby indirectly reducing the dielectric loss. When the liquid metal content is low, the increase in conductivity loss can partially offset the dielectric loss, resulting in a reduction in overall loss. Furthermore, TEMPO oxidized cellulose nanoparticles possess excellent dispersibility and nanoscale size, enabling the formation of a uniform network structure in the composite material. This network structure effectively disperses stress, reduces local electric field concentration, and thus lowers dielectric loss. With further increases in liquid metal content, the dispersibility of TEMPO oxidized cellulose nanoparticles is further improved, and the network structure becomes more uniform, further reducing dielectric loss.

[0100] (III) Tensile property testing and analysis

[0101] To more intuitively demonstrate the mechanical properties of the composite, tensile property tests were conducted on TLW-0, TLW-0.1, TLW-0.5, and TLW-1 from Comparative Example 2 and Examples 1-3. The results... Figure 10 As shown. Figure 10 In the figure, (a) is the stress-strain curve and (b) is the Young's modulus and toughness graph.

[0102] Depend on Figure 10(a) As can be seen, the tensile strength of the composite material increases from 11.3 MPa to 16.8 MPa with the increase of liquid metal content. When TOCNF@LM liquid metal-based micro-nano droplets are uniformly dispersed in the aqueous polyurethane matrix, they can act as a bridge for stress transfer, dispersing external forces more effectively into the matrix, thereby improving the overall strength of the composite material. However, its elongation at break decreases from 1718% to 1511%. This is because during the tensile process, stress is more likely to concentrate around the liquid metal, resulting in local stress much higher than the average stress. This stress concentration will trigger the material to fracture prematurely, thereby reducing the elongation at break. At the same time, the hydrogen bond interaction between the TOCNF@LM liquid metal-based micro-nano droplets and the aqueous polyurethane molecular chains restricts the mobility of the molecular chains, reducing the deformation capacity of the composite material during the tensile process, thereby reducing the elongation at break.

[0103] Young's modulus is an important parameter for measuring a material's resistance to tension or compression during the elastic deformation stage; toughness refers to the total amount of energy a material can absorb before fracture, usually calculated by the area under the stress-strain curve. Figure 10 (b) As can be seen, the Young's modulus of the composite material shows a significant upward trend with the increase of liquid metal content, rising from 0.63 MPa to 1.12 MPa. This is mainly attributed to the strong interfacial interaction (such as hydrogen bonding) between the carboxyl groups on the surface of TEMPO oxidized cellulose nanoparticles and the aqueous polyurethane matrix, which allows stress to be transferred more effectively from the matrix to the TOCNF@LM liquid metal-based micro / nano-droplet reinforcing phase, thereby improving the Young's modulus of the composite material. Simultaneously, the nanoscale dispersion of TEMPO oxidized cellulose nanoparticles allows for uniform distribution within the composite material, forming a good nano-network structure, further optimizing the mechanical properties of the composite material. The toughness of the composite material shows a trend of first increasing and then decreasing, with TLW-0.5 reaching a maximum toughness of 140.2 MJ / cm. 3 This indicates that an appropriate amount of liquid metal can effectively improve the plastic deformation capacity of composite materials, enabling them to absorb more energy before fracture. A suitable amount of liquid metal can be uniformly dispersed in the matrix, enhancing the interfacial bonding between the matrix and fibers, thereby improving the toughness of the composite material. However, when the liquid metal content is too high, it may lead to fiber aggregation, reducing the interfacial bonding effect and thus weakening the toughness of the composite material. This result provides an important theoretical basis for optimizing the mechanical properties of composite materials.

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A liquid metal-reinforced triboelectric material with a biomimetic surface, characterized in that, TEMPO oxidized cellulose nanoparticles were mixed with liquid metal gallium indium alloy to obtain TOCNF@LM liquid metal-based micro / nano droplets; the obtained TOCNF@LM liquid metal-based micro / nano droplets were incorporated into a substrate aqueous polyurethane, and a biomimetic rose petal micro-papillary structure was constructed using a template method to obtain a liquid metal-enhanced triboelectric material with a biomimetic surface. The method for preparing the liquid metal-reinforced triboelectric material with a biomimetic surface includes the following steps: (1) Liquid metal gallium indium alloy was added to the TEMPO oxidized nanocellulose suspension and then ultrasonically pulverized in an ultrasonic cell disruptor to obtain TOCNF@LM liquid metal-based micro-nano droplets; (2) TOCNF@LM liquid metal-based micro / nano droplets were added to aqueous polyurethane and magnetically stirred at room temperature to obtain a uniform suspension of TOCNF@LM-WPU; the mass ratio of the TOCNF@LM liquid metal-based micro / nano droplets to the aqueous polyurethane was 1:(0.5~2); the mass fraction of gallium-indium alloy in the uniform suspension of TOCNF@LM-WPU was 0.5wt%. (3) Select fresh rose petals, rinse them with water, blow them dry with nitrogen, and then dry them to obtain dried petals; take liquid polydimethylsiloxane, defoam it under vacuum, place the dried petals flat on the liquid polydimethylsiloxane, and then place them in a forced-air drying oven for a first curing. After curing, remove the petals to obtain a polydimethylsiloxane inverse template; pour a uniform suspension of TOCNF@LM-WPU onto the polydimethylsiloxane inverse template, defoam it under vacuum, and then place it in a forced-air drying oven for a second curing. After curing, peel off the polydimethylsiloxane inverse template to obtain a liquid metal reinforced triboelectric material with a biomimetic surface.

2. The liquid metal-reinforced triboelectric material with a biomimetic surface according to claim 1, characterized in that, The open-circuit voltage of the liquid metal-reinforced triboelectric material with a biomimetic surface is 240–250 V, the short-circuit current is 8.0–8.19 μA, and the short-circuit transferred charge is 90–95 nC.

3. The liquid metal-reinforced triboelectric material with a biomimetic surface according to claim 1, characterized in that, The zeta potential of the TOCNF@LM liquid metal-based micro / nano droplets is -38.0 to -39.6 mV, and no precipitation occurs after standing for 40 days.

4. A method for preparing a liquid metal-reinforced triboelectric material with a biomimetic surface as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Liquid metal gallium indium alloy was added to the TEMPO oxidized nanocellulose suspension and then ultrasonically pulverized in an ultrasonic cell disruptor to obtain TOCNF@LM liquid metal-based micro-nano droplets; (2) TOCNF@LM liquid metal-based micro / nano droplets were added to aqueous polyurethane and magnetically stirred at room temperature to obtain a uniform suspension of TOCNF@LM-WPU; the mass ratio of the TOCNF@LM liquid metal-based micro / nano droplets to the aqueous polyurethane was 1:(0.5~2); the mass fraction of gallium-indium alloy in the uniform suspension of TOCNF@LM-WPU was 0.5wt%. (3) Select fresh rose petals, rinse them with water, blow them dry with nitrogen, and then dry them to obtain dried petals; take liquid polydimethylsiloxane, defoam it under vacuum, place the dried petals flat on the liquid polydimethylsiloxane, and then place them in a forced-air drying oven for a first curing. After curing, remove the petals to obtain a polydimethylsiloxane inverse template; pour a uniform suspension of TOCNF@LM-WPU onto the polydimethylsiloxane inverse template, defoam it under vacuum, and then place it in a forced-air drying oven for a second curing. After curing, peel off the polydimethylsiloxane inverse template to obtain a liquid metal reinforced triboelectric material with a biomimetic surface.

5. The method for preparing the liquid metal-reinforced triboelectric material with a biomimetic surface according to claim 4, characterized in that, In step (1), the mass ratio of the TEMPO oxidized cellulose nanoparticle suspension to the gallium indium alloy is 1:(0.002~0.02); the mass fraction of the TEMPO oxidized cellulose nanoparticle suspension is 0.5~2wt%.

6. The method for preparing a liquid metal-reinforced triboelectric material with a biomimetic surface according to claim 4, characterized in that, In step (1), the conditions for ultrasonic pulverization are: ultrasonic time 5-15 min, ultrasonic interval (1-2) s / 1s, and ultrasonic power 65-455 W.

7. The method for preparing the liquid metal-reinforced triboelectric material with a biomimetic surface according to claim 4, characterized in that, In step (2), the magnetic stirring time is 0.5 to 1 hour.

8. The method for preparing the liquid metal-reinforced triboelectric material with a biomimetic surface according to claim 4, characterized in that, In step (3), the temperature of the first curing is 60-70℃ and the time is 2-3h.

9. The method for preparing the liquid metal-reinforced triboelectric material with a biomimetic surface according to claim 4, characterized in that, In step (3), the temperature of the secondary curing is 40-50℃ and the time is 10-12h.

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