Flexible triboelectric sensor, braided structure and manufacturing method of braided structure

Abstract

The invention discloses a flexible triboelectric sensor, a braided structure and a manufacturing method of the braided structure, and relates to the field of motion monitoring, and the flexible triboelectric sensor comprises a top electrode, a middle friction layer and a bottom electrode which are sequentially arranged from top to bottom in a vertical contact separation mode; the top electrode is made of silver fabric; the middle friction layer is a polymer formed by silica gel and PVDF powder; when an external force is applied, the top electrode is in complete contact with the middle friction layer, and free electrons are transferred to the middle friction layer based on a triboelectrification principle; along with release of external force, free electrons of the middle friction layer are transferred to the bottom electrode; and when the top electrode and the middle friction layer are in complete contact again, the bottom electrode transfers the free electrons to the top electrode based on the action of the electric field. The output voltage, the energy conversion efficiency and the quality factor of the friction sensor can be improved, and the friction sensor is tightly attached to the knee of the human body.

Description

Technical Field

[0001] This application relates to the field of motion monitoring, and in particular to a flexible triboelectric sensor, a braided structure, and a method for manufacturing the braided structure. Background Technology

[0002] Powering miniature wearable electronics has long been a challenge. Currently, the most advanced wearable electronics rely on electrochemical energy storage devices, especially lithium-ion batteries. However, as wearable electronics become increasingly intelligent, the demand for higher energy output and smaller size is growing, rendering current power supply methods inadequate. Therefore, efforts are underway to develop wearable energy harvesting devices as sustainable power sources, and to design wearable self-powered sensors to effectively harvest mechanical energy generated in daily life, aiming to power wearable electronics and enable human communication via mechanical signals.

[0003] In recent years, researchers have developed a variety of novel structures and materials with excellent energy harvesting and sensing properties to meet the needs of wearable devices. Among them, wearable textile electronics based on woven structures have attracted much attention due to their good flexibility, ultra-sensitive sensing performance, and extremely high electrical output performance. However, the electrical output performance of friction sensors is not high due to their frictional structure.

[0004] Therefore, in order to solve the above technical problems, there is an urgent need to provide a new flexible friction sensor that can improve the output voltage, energy conversion efficiency and quality factor of the friction sensor, so that the friction sensor can fit closely to the human knee. Summary of the Invention

[0005] The purpose of this application is to provide a flexible friction sensor, a braided structure, and a method for manufacturing the braided structure, which can improve the output voltage, energy conversion efficiency, and quality factor of the friction sensor, and enable the friction sensor to fit closely to the human knee.

[0006] To achieve the above objectives, this application provides the following solution:

[0007] In a first aspect, this application provides a flexible triboelectric sensor, comprising: a top electrode, a middle friction layer, and a bottom electrode; the top electrode, the middle friction layer, and the bottom electrode are arranged sequentially from top to bottom in a vertical contact separation mode.

[0008] The top electrode is made of silver fabric; the intermediate friction layer is a polymer formed of silicone and PVDF powder.

[0009] When an external force is applied, the top electrode and the middle friction layer are in complete contact. Based on the principle of triboelectric charging, the top electrode transfers free electrons to the middle friction layer. As the external force is released, the free electrons in the middle friction layer are transferred to the bottom electrode. And when the top electrode and the middle friction layer are in complete contact again, the bottom electrode transfers free electrons to the top electrode based on the effect of the electric field.

[0010] Optionally, the bottom electrode is an aluminum tape.

[0011] Secondly, this application provides a braided structure, which includes a flexible triboelectric sensor.

[0012] Optionally, the braided structure has a length of 0.1m, a width of 0.1m, and a thickness of 0.0018m.

[0013] Thirdly, this application provides a method for manufacturing a braided structure, applied to the aforementioned braided structure, the method comprising:

[0014] Silver powder, epoxy resin and diluent are mixed to obtain conductive paint coating;

[0015] The conductive coating is evenly sprayed onto the nylon fabric; and the sprayed nylon fabric is ventilated and dried for a preset time to obtain silver fabric.

[0016] The silicone is mixed according to a preset ratio to obtain the prepared silicone.

[0017] Printing patterned molds using 3D printing technology;

[0018] Different concentrations of PVDF powder were added to the prepared silica gel and stirred continuously to obtain a polymer formed by silica gel and PVDF powder.

[0019] The polymer formed by silicone and PVDF powder is poured into a patterned mold, cured under vacuum, and then demolded to obtain a surface protrusion structure.

[0020] The surface protrusion structure is cut into strips of a preset size to obtain the intermediate friction layer;

[0021] Aluminum tape is attached to the bottom surface of the middle friction layer to obtain the bottom electrode;

[0022] A woven structure is obtained based on silver fabric, an intermediate friction layer, and a bottom electrode.

[0023] Optionally, the mixing of silver powder, epoxy resin, and diluent to obtain a conductive paint coating specifically includes:

[0024] Mix silver powder, epoxy resin and diluent;

[0025] The mixed silver powder, epoxy resin and diluent are stirred at preset intervals to obtain conductive paint coating.

[0026] Optionally, the step of attaching aluminum tape to the bottom surface of the intermediate friction layer to obtain the bottom electrode further includes:

[0027] Wipe the surface of the aluminum tape with deionized water and anhydrous ethanol, and then allow it to air dry.

[0028] Optionally, the braided structure, based on silver fabric, an intermediate friction layer, and a bottom electrode, specifically includes:

[0029] The thickness of both the silver fabric and the bottom electrode is set to 0.0001m; and the gap between the silver fabric and the bottom electrode is set to 0.0007m.

[0030] Optionally, the braided structure, based on silver fabric, an intermediate friction layer, and a bottom electrode, further includes:

[0031] The woven structure is encapsulated using PDMS film.

[0032] Optionally, the braided structure, based on silver fabric, an intermediate friction layer, and a bottom electrode, further includes:

[0033] Finite element simulations of the transverse and longitudinal minimum elements of the braided structure were performed using COMSOL software.

[0034] According to the specific embodiments provided in this application, this application has the following technical effects:

[0035] This application provides a flexible triboelectric sensor, a braided structure, and a method for fabricating the braided structure. By employing a vertical contact separation mode, a top electrode, a middle friction layer, and a bottom electrode are sequentially arranged from top to bottom. This unique vertical separation structure offers advantages such as high output voltage, high energy conversion efficiency, and high quality factor. Using silver fabric as the top electrode allows for excellent contact with the human knee and improves the conductivity of the flexible triboelectric sensor. A polymer formed from silicone and polyvinylidene fluoride (PVDF) powder is used as the middle friction layer. Incorporating PVDF powder into the middle triboelectric layer significantly improves its dielectric constant. When subjected to external force, the top electrode and the middle friction layer are in complete contact, transferring free electrons to the middle friction layer based on the principle of triboelectric charging. As the external force is released, free electrons from the middle friction layer transfer to the bottom electrode. When the top electrode and the middle friction layer are in complete contact again, the bottom electrode transfers free electrons to the top electrode based on the electric field, thereby collecting the motion signal of the human knee. This application improves the output voltage, energy conversion efficiency, and quality factor of the triboelectric sensor, ensuring a close fit between the sensor and the human knee. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram illustrating the working mechanism of a flexible triboelectric sensor provided in one embodiment of this application under a pressing cycle;

[0038] Figure 2 This is a schematic diagram of a braided structure provided in one embodiment of this application;

[0039] Figure 3 This is a schematic diagram illustrating the fabrication process of a weaving structure according to an embodiment of this application;

[0040] Figure 4 A schematic diagram illustrating material selection for one embodiment of this application;

[0041] Figure 5 This is a dimensional schematic diagram of a weaving structure provided in one embodiment of this application;

[0042] Figure 6 This is a schematic diagram of an infinite circular region provided in an embodiment of this application;

[0043] Figure 7This is a schematic diagram illustrating the setting of mesh size parameters according to an embodiment of this application;

[0044] Figure 8 This is a schematic diagram illustrating the effect of mesh division according to an embodiment of this application;

[0045] Figure 9 This is a schematic diagram of the electromotive force distribution provided in one embodiment of this application. Figure 9 Part (a) is a schematic diagram of the electromotive force distribution under the pressing state. Figure 9 Part (b) is a schematic diagram of the electromotive force distribution in the released state. Detailed Implementation

[0046] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] like Figure 1 As shown, this application provides a flexible triboelectric sensor, comprising: a top electrode, a middle friction layer, and a bottom electrode; the top electrode, the middle friction layer, and the bottom electrode are arranged sequentially from top to bottom in a vertical contact separation mode. The bottom electrode is an aluminum tape.

[0049] The top electrode is made of silver fabric; the intermediate friction layer is a polymer formed from silicone and PVDF powder.

[0050] When an external force is applied, the top electrode and the middle friction layer are in complete contact. Based on the principle of triboelectric charging, the top electrode transfers free electrons to the middle friction layer. As the external force is released, the free electrons in the middle friction layer are transferred to the bottom electrode. And when the top electrode and the middle friction layer are in complete contact again, the bottom electrode transfers free electrons to the top electrode based on the effect of the electric field.

[0051] In an exemplary embodiment, this application employs a vertical contact separation mode of a flexible triboelectric sensor. When an external force is applied to bring the silver fabric into complete contact with the polymer formed by silicone and PVDF powder, according to the principle of triboelectricity, the free electrons of the silver fabric are transferred to the polymer formed by silicone and PVDF powder, forming equivalent positive and negative triboelectric charges. As the external force is released, the balance between the top electrode and the middle triboelectric layer is broken. Under the action of the electric field, the triboelectric charge gradually transfers to the bottom electrode. When the external force is completely released, almost all the free electrons are concentrated on the bottom electrode. At this time, a new balance is established between the middle triboelectric layer and the bottom electrode. When the top electrode approaches the middle triboelectric layer again, under the action of the electric field, the free electrons on the bottom electrode gradually transfer to the top electrode.

[0052] In another exemplary embodiment of this application, a braided structure is provided, such as... Figure 2 As shown, the woven structure includes the flexible triboelectric sensor. The flexible triboelectric sensor of the woven structure can fit closely to the human knee, better capturing body motion signals and providing an excellent dataset for motion monitoring, thus laying a solid foundation for subsequent algorithm analysis. The fabricated 3D woven triboelectric nanogenerator (TENG) has a length of 0.1 m, a width of 0.1 m, and a thickness of 0.0018 m.

[0053] The braided structure allows the flexible triboelectric sensor to fit more closely to the human knee and has good flexibility, making it very durable. In addition, compared to a solid flat material, the braided structure makes it easier to ensure that the upper and lower electrodes can generate greater displacement during movement, which can effectively improve its electrical output performance.

[0054] like Figure 3 As shown, this application also provides a method for manufacturing a braided structure, the method comprising:

[0055] S1, mix silver powder, epoxy resin and diluent to obtain conductive paint coating.

[0056] S2, the conductive coating is evenly sprayed onto the nylon fabric; and the sprayed nylon fabric is ventilated and dried for a preset time to obtain the silver fabric.

[0057] S3, mix the silicone according to the preset ratio to obtain the prepared silicone.

[0058] S4 is a patterned mold printed using 3D printing technology.

[0059] S5, PVDF powder of different concentrations is added to the prepared silica gel and stirred continuously to obtain a polymer formed by silica gel and PVDF powder.

[0060] S6. The polymer formed by silicone and PVDF powder is poured into a patterned mold, and after vacuum curing, it is demolded to obtain a surface raised structure.

[0061] S7, cut the surface protrusion structure into strips of a preset size to obtain the intermediate friction layer.

[0062] S8. Apply aluminum tape to the bottom surface of the intermediate friction layer to obtain the bottom electrode.

[0063] S9, based on silver fabric, intermediate friction layer and bottom electrode, has a woven structure.

[0064] In one exemplary embodiment, the woven structure uses silver fabric and aluminum tape as the top and bottom electrodes, respectively, with a mixture of silicone and PVDF powder as the intermediate friction layer. On the side near the knee, silver fabric and conductive tape are used as the top electrode, and the device is finally encapsulated with a polydimethylsiloxane (PDMS) film to reduce the foreign body sensation and discomfort associated with wearing the device. PVDF powder is a highly reactive polymer with strong piezoelectric response and low acoustic impedance, exhibiting excellent electroactivity and considered one of the most popular polymers in energy harvesting technology. Researchers are also attempting to optimize the friction layer structure of triboelectric sensors to achieve higher electrical output performance. Adding PVDF powder to the friction layer is a convenient method to obtain high power density output; therefore, doping PVDF powder into the triboelectric layer can significantly improve the dielectric constant of the friction layer. Silver powder is mixed with epoxy resin and thinner to create a sprayable conductive paint coating. Before use, the coating is thoroughly stirred in the paint can (evenly stirred silver particles ensure good conductivity of the sprayed paint film). The coating is then sprayed onto nylon fabric to form a silver fabric. During this process, the coating should be stirred every 5 minutes to achieve optimal conductivity. It is then placed in a dry, well-ventilated environment to allow the solvent to evaporate. The surface drying time is generally 15 minutes; if a thicker layer is applied, the evaporation time should be extended. When creating the dielectric layer, a specific pattern structure is formed on its surface to increase friction. A pattern structure mold is created using 3D printing technology. Silicone is then mixed in a specific ratio, and different concentrations of PVDF powder are added to the mixed silicone. The mixture is stirred with a glass rod for about 5 minutes, and finally poured into the pre-made mold. After vacuum degassing, it is cured at 50°C for 30 minutes. After demolding, a raised surface structure is formed. The prepared pattern structure is then cut into 2×10cm pieces. 2The strips are prepared for the next step; finally, the surface of the aluminum tape is wiped with deionized water and anhydrous ethanol, placed in a fume hood to dry, and the aluminum tape is attached to the back of the dielectric layer as the bottom electrode.

[0065] Because the geometric structure of the braided structure is symmetrical, only a portion of the braided structure needs to be modeled. To more clearly explain the changes in surface potential, finite element simulations of the transverse and longitudinal minimum elements of the 3D braided structure TENG were performed using COMSOL software. The simulation process specifically includes the following steps:

[0066] The first step is to select materials: such as Figure 4 As shown, taking a minimum unit of the braided structure as an example, the material of the top electrode is silver (Ag), the triboelectric material in the middle is polytetrafluoroethylene (PTFE) with the same triboelectric parameters as the polymer formed by silicone and PVDF powder, and the material of the bottom electrode is aluminum (Al).

[0067] The second step is to construct the geometric shape: such as Figure 5 As shown, the thickness of the silver fabric and aluminum tape is set to 0.0001m, and the gap in the middle is 0.0007m. Finally, an infinite circle with a radius of 5m is drawn around the entire woven structure, and the thickness of the infinite circle is 10m. -2 m, the infinite circular region drawn as Figure 6 As shown.

[0068] The third step is to construct the electrostatic field: Within the outer infinite circular domain, regions a, b, c, and d are designated as grounded, and electrodes are set using the "terminal" characteristic of the domain. The entire electrostatic field follows the law of conservation of charge, using the formula... Determine the steady-state equation, where ∫ denotes the integral over an infinite circular domain. Let Ω denote the integration domain of the infinite circular domain, D denote the boundary of the infinite circular domain, S denote the area of ​​the infinite circular domain, n denote the unit normal vector, dS denote an infinitesimal area element on the infinite circular domain, and Q0 denote the charge of a point charge. The charge of the transverse silver (Ag) electrode is set to -bnd2 C, the charge of the remaining terminals is set to -bnd1 C, and the charge density of the last four surfaces is set to -QC / m. 2 The specific value of Q is 10. -5 C.

[0069] Step 4: Mesh generation: This application uses a free triangular mesh, such as... Figure 7As shown, the element size is set to coarse. Among the element size parameters, the maximum element size is 1m, the minimum element size is 0.02m, the maximum element growth rate is 1.4, the curvature factor is 0.4, and the narrow region resolution is 1. The final partitioning effect is shown below. Figure 8 As shown.

[0070] Step 5: Perform parametric scanning: The range of parametric scanning is 10. -4 m~0.005m, step size 10 -4 Then the calculation begins, and finally the output electromotive force under simulated pressing conditions can be seen as follows: Figure 9 As shown in part (a), the output electromotive force in the released state is as follows: Figure 9 As shown in section (b), it is consistent with the subsequent measurement results.

[0071] This application discloses a flexible triboelectric sensor that can be worn on the human knee, which can fit well with the human knee and collect knee motion signals, thus making a greater contribution to the fields of motion monitoring and knee health protection.

[0072] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] This application uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. In summary, the content of this specification should not be construed as a limitation of this application.

Claims

1. A flexible triboelectric sensor, characterized in that, The flexible triboelectric sensor includes a top electrode, a middle friction layer, and a bottom electrode; the top electrode, the middle friction layer, and the bottom electrode are arranged sequentially from top to bottom in a vertical contact separation mode. The top electrode is made of silver fabric; the intermediate friction layer is a polymer formed of silicone and PVDF powder. When an external force is applied, the top electrode and the middle friction layer are in complete contact. Based on the principle of triboelectric charging, the top electrode transfers free electrons to the middle friction layer. As the external force is released, the free electrons in the middle friction layer are transferred to the bottom electrode. And when the top electrode and the middle friction layer are in complete contact again, the bottom electrode transfers free electrons to the top electrode based on the effect of the electric field.

2. The design method for a flexible triboelectric sensor according to claim 1, characterized in that, The bottom electrode is made of aluminum tape.

3. A braided structure, characterized in that, The braided structure includes the flexible triboelectric sensor as described in any one of claims 1-2.

4. The braided structure according to claim 3, characterized in that, The woven structure has a length of 0.1m, a width of 0.1m, and a thickness of 0.0018m.

5. A method for manufacturing a woven structure, characterized in that, Applied to the braided structure according to any one of claims 3-4, the method for manufacturing the braided structure includes: Silver powder, epoxy resin and diluent are mixed to obtain conductive paint coating; The conductive coating is evenly sprayed onto the nylon fabric; and the sprayed nylon fabric is ventilated and dried for a preset time to obtain silver fabric. Mix the silicone according to the preset ratio to obtain the prepared silicone; Printing patterned molds using 3D printing technology; Different concentrations of PVDF powder were added to the prepared silica gel and stirred continuously to obtain a polymer formed by silica gel and PVDF powder. The polymer formed by silicone and PVDF powder is poured into a patterned mold, cured under vacuum, and then demolded to obtain a surface protrusion structure. The surface protrusion structure is cut into strips of a preset size to obtain the intermediate friction layer; Aluminum tape is attached to the bottom surface of the middle friction layer to obtain the bottom electrode; A woven structure is obtained based on silver fabric, an intermediate friction layer, and a bottom electrode.

6. The method for manufacturing the braided structure according to claim 5, characterized in that, The process of mixing silver powder, epoxy resin, and diluent to obtain a conductive paint coating specifically includes: Mix silver powder, epoxy resin and diluent; The mixed silver powder, epoxy resin and diluent are stirred at preset intervals to obtain conductive paint coating.

7. The method for manufacturing the braided structure according to claim 5, characterized in that, The step of attaching aluminum tape to the bottom surface of the intermediate friction layer to obtain the bottom electrode also includes: Wipe the surface of the aluminum tape with deionized water and anhydrous ethanol, and then allow it to air dry.

8. The method for manufacturing the braided structure according to claim 5, characterized in that, The braided structure, based on silver fabric, an intermediate friction layer, and a bottom electrode, specifically includes: The thickness of both the silver fabric and the bottom electrode is set to 0.0001m; and the gap between the silver fabric and the bottom electrode is set to 0.0007m.

9. The method for manufacturing the braided structure according to claim 5, characterized in that, The structure, based on silver fabric, an intermediate friction layer, and a bottom electrode, is then further comprising: The woven structure is encapsulated using PDMS film.

10. The method for manufacturing the braided structure according to claim 5, characterized in that, The process involves obtaining a braided structure based on silver fabric, an intermediate friction layer, and a bottom electrode. The process further includes using COMSOL software to perform finite element simulations on the transverse and longitudinal minimum units of the braided structure.

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