A moisture-resistant cellulose triboelectric material for motion sensing and its preparation method

Abstract

This invention discloses a moisture-resistant cellulose triboelectric material for motion sensing and its preparation method. Cellulose and tert-butanol are mixed uniformly to obtain a cellulose mixed solution. Methyltrimethoxysiloxane is added to the cellulose mixed solution as a hydrophobic modifier. Then, using sandpaper as a mold, the modified cellulose is poured into the mold and dried to obtain a hydrophobic and moisture-resistant cellulose film. The cellulose film is then adhered to an acrylic plate using conductive adhesive to obtain a hydrophobic and moisture-resistant cellulose triboelectric material. The moisture-resistant cellulose triboelectric material of this invention maintains stable triboelectric output and sensing signals even in high humidity environments, solving the problem of insufficient moisture resistance in existing cellulose triboelectric materials. This invention employs a combination of chemical modification and surface structure engineering, which has advantages such as stable hydrophobic effect, strong moisture resistance, and simple production process, making it easy to achieve industrial production.

Description

[Technical Field]

[0001] This invention relates to the field of cellulose functional materials and triboelectric nanogenerators, specifically to a moisture-resistant cellulose triboelectric material for motion sensing and its preparation method. [Background Technology]

[0002] In recent years, triboelectric nanogenerators based on the triboelectric effect and electrostatic induction have shown great application potential in energy harvesting and self-powered sensing, leading to widespread interest in the development of advanced triboelectric materials. Cellulose, the most abundant natural polymer on Earth, boasts advantages such as wide availability, renewability, and biodegradability, making it a crucial raw material for replacing petrochemical materials. Different functional groups (such as fluorine, amino, and methyl groups) can be introduced into cellulose to enhance its charge generation ability, and numerous studies have demonstrated its potential to be processed into high-performance triboelectric materials.

[0003] High-performance green triboelectric nanogenerators using cellulose as the friction layer possess excellent biocompatibility, portability, and sensing sensitivity, thus finding widespread application in motion detection and sensing. Current research includes, for example, Chinese Patent No. 201910509336.3, which discloses the fabrication of a flexible pressure sensor for monitoring motion signals and human pulse signals. The invention involves preparing triboelectric positive polymer spinning solutions and triboelectric negative polymer spinning solutions (containing nanowires), wherein the triboelectric negative polymer spinning solution contains nanowires; electrospinning is performed separately to obtain triboelectric positive fiber films and triboelectric negative fiber films; a solution containing a polymer and a curing agent is prepared, poured onto a mold, and cured to obtain a flexible support substrate with grooves formed on its upper surface; electrodes are formed on the back sides of the triboelectric positive and triboelectric negative fiber films, respectively, and the flexible pressure sensor for monitoring motion signals and human pulse signals is assembled. This invention has broad application prospects in smart wearables, personal fitness and health, and physiological signal monitoring.

[0004] For example, Chinese Patent No. 201910163866.7 discloses a method for preparing a cellulose-based flexible pressure sensor material. The method involves mixing fibers, surfactants, Mxene conductive material, and water to obtain a slurry; stirring the slurry until it becomes foamy to obtain foam fibers; vacuum filtering the foam fibers until no water lines are visible to the naked eye; and then drying them to a moisture content of less than 10%. This invention uses natural cellulose fibers as raw materials, introduces Mxene two-dimensional conductive material, and employs a one-step mechanical stirring molding technology at room temperature and pressure to prepare a novel cellulose-based flexible pressure sensor material. The raw materials are widely available, the cost is relatively low, the production process is simple, and the product has low density, high sensitivity, high flexibility, and strong adaptability. It has great application potential in smart wearable devices such as electronic skin, virtual reality, and health monitoring.

[0005] Existing research also has some limitations. For example, environmental factors pose a significant challenge to cellulose materials during motion sensing. Besides potential wear and deformation, moisture is a serious threat. Notably, the abundant hydroxyl functional groups in the natural cellulose structure give the material strong hydrophilicity. In high-humidity environments, cellulose readily absorbs moisture, forming a water film at the friction interface. This hinders charge transfer and causes charge dissipation, resulting in highly unstable triboelectric properties. Therefore, improving the moisture resistance of cellulose-based triboelectric materials is a key factor in realizing their application in motion sensing. [Summary of the Invention]

[0006] To address the problem of insufficient moisture resistance of cellulose in existing technologies, this invention provides a cellulose triboelectric material for moisture-resistant motion sensing and its preparation method, which enables stable monitoring of human motion status in high humidity environments. This cellulose triboelectric material for moisture-resistant motion sensing has advantages such as stable sensing electrical signals, high response sensitivity, strong hydrophobicity, and stable moisture-resistant response, and can effectively solve the problem of insufficient moisture resistance of cellulose-based triboelectric materials in existing technologies.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a moisture-resistant cellulose triboelectric material for motion sensing includes the following steps:

[0009] 1) Mix cellulose and tert-butanol at a mass ratio of 6:4 and stir until homogeneous to obtain a cellulose mixed solution;

[0010] 2) Add methyltrimethoxysiloxane to deionized water with pH 4, stir well, and prepare a 0.5-10 wt% silane hydrolysate;

[0011] 3) The silane hydrolysate obtained in step 2) is added to the cellulose mixed solution obtained in step 1) at a ratio of 1% wt, and a chemical modification reaction is carried out under stirring conditions. After the chemical modification reaction is completed, the mixture is homogenized by ultrasound to obtain a modified cellulose suspension.

[0012] 4) Pour the homogenized modified cellulose suspension from step 3) into a sandpaper mold and allow it to dry naturally to form a cellulose film with hydrophobic and moisture-resistant properties.

[0013] 5) The cellulose film obtained in step 4) is attached to the acrylic plate with conductive adhesive, and wires are connected to obtain a moisture-resistant cellulose triboelectric material for motion sensing.

[0014] In this invention:

[0015] Step 1) involves stirring the mixture evenly using magnetic stirring at a speed of 1000 r / min for 10 min.

[0016] Step 2) The pH of the deionized water is 4, which is adjusted to 4 using hydrochloric acid solution or sodium hydroxide solution; the stirring is done by magnetic stirring at a speed of 1000 r / min for 10 min.

[0017] Step 3) The stirring is magnetic stirring, the stirring speed is 1000 r / min, and the time is 2 h; the homogenization is performed by ultrasound, the ultrasound power is 100 W, and the ultrasound time is 10 min.

[0018] Step 4) The sandpaper used in the sandpaper mold is 800 grit sandpaper, the length and width of the mold are both 5cm, and the height is 1cm; the natural drying molding is carried out at a drying temperature of 25℃ and an air humidity of 60%RH.

[0019] The conductor mentioned in step 5) is selected from any one of copper wire, silver wire, tin foil wire, and carbon fiber wire.

[0020] This invention also relates to a moisture-resistant cellulose triboelectric material for motion sensing, obtained using the aforementioned preparation method. This cellulose triboelectric material possesses advantages such as stable sensing signal, high response sensitivity, strong hydrophobicity, and stable moisture resistance. Its water contact angle is 119.7°-144.4°, and its surface energy is 1.08 mJ / m². 2 -1.31mJ / m 2 The open-circuit voltage density of the moisture-resistant cellulose triboelectric material is 1.31 × 10⁻⁶. 4 V / m 2 -1.63×10 4 V / m 2The short-circuit current density is 0.43 mA / m. 2 -0.89mA / m 2 The transferred charge density is 3.56 μC / m. 2 -4.56μC / m 2 .

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. The present invention discloses a method for preparing a moisture-resistant cellulose triboelectric material for motion sensing. This method utilizes methyltrimethoxysiloxane to chemically modify cellulose and employs sandpaper as a mold to improve the surface roughness of the cellulose material, thus addressing the problem of insufficient moisture resistance in existing cellulose triboelectric materials. Under the same conditions, the water vapor permeability of the modified cellulose is lower than that of the unmodified cellulose film, indicating that the modified cellulose has excellent moisture barrier properties. In high humidity environments, the open-circuit voltage of the moisture-resistant cellulose triboelectric material for motion sensing reaches 92V and remains stable, while the rate of change of open-circuit voltage under the influence of humidity is small, indicating that the moisture-resistant cellulose triboelectric material for motion sensing has good sensing stability. Therefore, the moisture-resistant cellulose triboelectric material prepared by this invention can be applied to motion sensing in high humidity environments, such as in the development of smart insoles and smart protective clothing.

[0023] 2. The moisture-resistant cellulose triboelectric material for motion sensing described in this invention has the advantages of simple method and strong hydrophobicity. Through the method of this invention, the cellulose water static contact angle is 119.7°-144.4°, and the surface free energy of the moisture-resistant cellulose triboelectric material for motion sensing is 1.08 mJ / m². 2 -1.31mJ / m 2 Liquids exhibit low adhesion to moisture-resistant cellulose triboelectric materials used for motion sensing, resulting in a self-cleaning effect. [Attached Image Description]

[0024] Figure 1 This is a schematic diagram of the moisture-resistant cellulose triboelectric material for motion sensing obtained in Embodiment 1 of the present invention;

[0025] Figure 2 This is a flow chart of the preparation process of the moisture-resistant cellulose triboelectric material described in this invention;

[0026] Figure 3 This is a comparison chart of the water vapor transmission rate of cellulose before and after modification as described in Example 1 of the present invention;

[0027] Figure 4 This is a comparison diagram of the open-circuit voltage of the moisture-resistant cellulose triboelectric material for motion sensing described in Embodiment 1 of the present invention under different humidity environments.

[0028] Figure 5 This is a water contact angle data diagram of the moisture-resistant cellulose triboelectric material for motion sensing described in Embodiment 1 of the present invention.

Detailed Implementation Methods

[0029] The specific embodiments of the present invention will be further described below with reference to examples.

[0030] Example 1:

[0031] A method for preparing a moisture-resistant cellulose triboelectric material for motion sensing includes the following steps:

[0032] Step 1) Mix 60 wt% cellulose with 40 wt% tert-butanol using magnetic stirring at a speed of 1000 r / min for 10 min to obtain a cellulose mixed solution.

[0033] Step 2): Adjust the pH of deionized water to 4 using hydrochloric acid solution and sodium hydroxide solution, add 0.5 wt% methyltrimethoxysiloxane, and stir evenly under magnetic stirring speed of 1000 r / min and time of 10 min to prepare silane hydrolysate.

[0034] Step 3) The silane hydrolysate obtained in step 2) is added to the cellulose mixed solution obtained in step 1) at a ratio of 1% wt. The chemical modification reaction is completed under magnetic stirring conditions (stirring speed of 1000 r / min, stirring time of 2 h). Then, the modified cellulose suspension is obtained by ultrasonication (ultrasonic power of 100 W, ultrasonic time of 10 min).

[0035] Step 4), the homogenized modified cellulose suspension from step 3) is poured into a sandpaper mold (sandpaper mesh size is 800 mesh, mold length and width are both 5cm, height is 1cm) and naturally dried (drying temperature is 25℃, air humidity is 60%RH) to form a cellulose film with hydrophobic and moisture-resistant properties.

[0036] Step 5): The cellulose film obtained in Step 4) is attached to the acrylic plate with conductive adhesive, and copper wires are connected at the same time to obtain a moisture-resistant cellulose triboelectric material that can be used for motion sensing.

[0037] Figure 1 This is a schematic diagram of the moisture-resistant cellulose triboelectric material for motion sensing obtained in Embodiment 1 of the present invention;

[0038] Figure 2 This is a flow chart of the preparation process of the moisture-resistant cellulose triboelectric material described in this invention;

[0039] Figure 3This is a comparison chart of the water vapor transmission rate of cellulose before and after modification as described in Example 1 of the present invention;

[0040] Figure 4 This is a comparison diagram of the open-circuit voltage of the moisture-resistant cellulose triboelectric material for motion sensing described in Embodiment 1 of the present invention under different humidity environments.

[0041] Figure 5 This is a water contact angle data diagram of the moisture-resistant cellulose triboelectric material for motion sensing described in Embodiment 1 of the present invention.

[0042] result:

[0043] The moisture-resistant cellulose triboelectric material for motion sensing obtained in Example 1 has a water contact angle of 119.7° and a surface energy of 1.08 mJ / m². 2 The open-circuit voltage density of the moisture-resistant cellulose triboelectric material reaches 1.63 × 10⁻⁶. 4 V / m 2 The short-circuit current density reaches 0.89 mA / m 2 The transferred charge density reaches 4.56 μC / m 2 .

[0044] Under the same conditions, the water vapor transmission rate of modified cellulose film was lower than that of unmodified cellulose film, with a difference of 110.77 g / (m²). 2 ·d)(e.g. Figure 3 As shown in the figure, this indicates that modified cellulose has good moisture barrier properties. In a high humidity environment, the open-circuit voltage of the modified cellulose triboelectric material can reach 92V and remain stable, while the open-circuit voltage change rate under the influence of humidity is less than 0.098% (e.g., ...). Figure 4 As shown in the figure, the modified cellulose triboelectric material exhibits good sensing stability.

[0045] Example 2:

[0046] A method for preparing a moisture-resistant cellulose triboelectric material for motion sensing includes the following steps:

[0047] The conductor mentioned in step 5) is selected from silver wire, and the rest is the same as in Example 1.

[0048] The moisture-resistant cellulose triboelectric material obtained in Example 2 for motion sensing has a water contact angle of 131.2° and a surface energy of 1.24 mJ / m². 2 The open-circuit voltage density of the moisture-resistant cellulose triboelectric material reaches 1.53 × 10⁻⁶. 4 V / m 2 The short-circuit current density reaches 0.68 mA / m 2 The transferred charge density reaches 4.33 μC / m 2 .

[0049] Example 3:

[0050] A method for preparing a moisture-resistant cellulose triboelectric material for motion sensing includes the following steps:

[0051] The conductor mentioned in step 5) is selected from carbon fiber wire, and the rest is the same as in Example 1.

[0052] The moisture-resistant cellulose triboelectric material obtained in Example 3 for motion sensing has a water contact angle of 144.4° and a surface energy of 1.31 mJ / m². 2 The open-circuit voltage density of the moisture-resistant cellulose triboelectric material reaches 1.32 × 10⁻⁶. 4 V / m 2 The short-circuit current density reaches 0.50 mA / m 2 The transferred charge density reaches 3.89 μC / m 2 .

[0053] Example 4:

[0054] A method for preparing a moisture-resistant cellulose triboelectric material for motion sensing includes the following steps:

[0055] The wire described in step 5) is selected from tin foil wire, and the rest is the same as in Example 1.

[0056] The moisture-resistant cellulose triboelectric material obtained in Example 4 for motion sensing has a water contact angle of 130.4° and a surface energy of 1.23 mJ / m². 2 The open-circuit voltage density of the fiber triboelectric material reaches 1.31 × 10⁻⁶. 4 V / m 2 The short-circuit current density reaches 0.43 mA / m 2 The transferred charge density reaches 3.56 μC / m 2 .

[0057] Comparative Example 1:

[0058] CN111647181B discloses a highly transparent flexible porous triboelectric material and its preparation method. The preparation method involves dissolving cellulose acetate powder in a mixed solvent of acetone and water to obtain transparent cellulose acetate solutions with different mass fractions; mixing the above transparent cellulose solutions with a preheated polyethyleneimine solution under certain treatment conditions to obtain a uniform casting liquid; then coating the above casting liquid onto a self-made template to form a film, and after the pre-formed film is left to stand, it is placed in an oven for drying. The transparent film obtained after the solvent has completely evaporated is the highly transparent flexible porous triboelectric material.

[0059] This method differs from the present invention in the following ways:

[0060] 1. The objective of this invention is to solve the moisture resistance problem of cellulose triboelectric materials, which is different from the objective of this method;

[0061] 2. The present invention uses chemical modification and surface structure engineering to hydrophobically modify cellulose, which is different from the method described above.

[0062] Comparative Example 2:

[0063] CN111355400A discloses an all-cellulose-based triboelectric nanogenerator. This invention uses a cation-modified cellulose nanofiber-based aerogel membrane as a triboelectric negative material and a cellulose nanofiber-based aerogel membrane as a triboelectric positive material. A cellulose conductive composite electrode material is provided on the back side of both the cation-modified cellulose nanofiber-based aerogel membrane and the cellulose nanofiber-based aerogel membrane, forming a gap between the two aerogel membranes. The all-cellulose-based triboelectric nanogenerator of this invention has a 10-500% increase in surface charge, a 20-500% increase in short-circuit current, and a 50-500% increase in open-circuit voltage.

[0064] This invention differs from the present invention in the following ways:

[0065] 1. The objective of this invention is to solve the moisture resistance problem of cellulose triboelectric materials, which is different from the objective of this method;

[0066] 2. The present invention uses chemical modification and surface structure engineering to hydrophobically modify cellulose, which is different from the method described above.

[0067] Comparative Example 3:

[0068] CN113463438A discloses a superhydrophobic paper-based bifunctional flexible sensing material, its preparation method, and its application. The method includes the following steps: Step 1, pulping fibers, reinforcing agents, and graphene dispersions to the required papermaking consistency, wherein the mass ratio of graphene to reinforcing agents in the fiber and graphene dispersions is (60-85):(15-40):(1-10), to obtain a mixed pulp; Step 2, preparing graphene paper from the mixed pulp, immersing it in a papermaking sizing agent, and then drying it to obtain the superhydrophobic paper-based bifunctional flexible sensing material.

[0069] This method differs from the present invention in the following ways:

[0070] 1. This invention relates to the field of triboelectric nanogenerator technology, specifically to the development and application of triboelectric sensing materials, which differs from the resistive sensing materials of this method in the field of technology;

[0071] 2. This method focuses on solving the moisture resistance problem of cellulose, which has a different objective than this method;

[0072] 3. The present invention uses chemical modification and surface structure engineering to hydrophobically modify cellulose, which is different from the method described above.

[0073] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a moisture-resistant cellulose triboelectric material for motion sensing, characterized in that: Includes the following steps: 1) Mix cellulose and tert-butanol at a mass ratio of 6:4 and stir until homogeneous to obtain a cellulose mixed solution; 2) Add methyltrimethoxysiloxane to deionized water with pH 4, stir evenly, and prepare a 0.5-10 wt% silane hydrolysate; the pH 4 deionized water is prepared by adjusting the pH of the deionized water to 4 using hydrochloric acid solution or sodium hydroxide solution; the stirring evenly is carried out by magnetic stirring at a speed of 1000 r / min for 10 min. 3) The silane hydrolysate obtained in step 2) is added to the cellulose mixed solution obtained in step 1) at a ratio of 1%wt. A chemical modification reaction is carried out under stirring conditions. After the chemical modification reaction is completed, the modified cellulose suspension is obtained by ultrasonic homogenization. The stirring is magnetic stirring at a speed of 1000 r / min for 2 h. The ultrasonic homogenization is performed at a power of 100 W for 10 min. 4) Pour the homogenized modified cellulose suspension from step 3) into a sandpaper mold and allow it to air dry to form a cellulose film with hydrophobic and moisture-resistant properties; the sandpaper used in the sandpaper mold is 800 mesh, and the length and width of the mold are both 5cm, and the height is 1cm; the air drying process is carried out at a drying temperature of 25℃ and an air humidity of 60%RH. 5) The cellulose film obtained in step 4) is attached to the acrylic plate with conductive adhesive, and wires are connected to obtain a moisture-resistant cellulose triboelectric material for motion sensing.

2. The method for preparing a moisture-resistant cellulose triboelectric material for motion sensing according to claim 1, characterized in that: Step 1) The mixing process is carried out using magnetic stirring at a speed of 1000 r / min for 10 min.

3. The method for preparing a moisture-resistant cellulose triboelectric material for motion sensing according to claim 1, characterized in that: The conductor mentioned in step 5) is selected from any one of copper wire, silver wire, tin foil wire, and carbon fiber wire.

4. A moisture-resistant cellulose triboelectric material for motion sensing, characterized in that: The material is prepared using the method described in any one of claims 1-3 for a moisture-resistant cellulose triboelectric material for motion sensing, exhibiting a water contact angle of 119.7°-144.4° and a surface energy of 1.08 mJ / m². 2 -1.31 mJ / m 2 The open-circuit voltage density of the moisture-resistant cellulose triboelectric material reaches 1.31 × 10⁻⁶. 4 V / m 2 -1.63×10 4 V / m 2 The short-circuit current density reaches 0.43 mA / m 2 -0.89 mA / m 2 The transferred charge density reaches 3.56 μC / m 2 -4.56 μC / m 2 .

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