Multilayer silver nanowire composite flexible motion sensor and preparation method and application thereof

Abstract

The application provides a multilevel silver nanowire composite flexible motion sensor and a preparation method and application thereof. The method comprises the following steps: dropping silver nanowire ink on a glass substrate after plasma surface treatment to form a conductive silver nanowire coating; then dropping an emulsion polymer on the silver nanowire coating on the glass substrate, and then curing at 60-80 degrees to obtain a cured polymer film; and finally peeling the cured polymer film from the glass substrate to obtain a multilevel silver nanowire composite flexible motion sensor. The silver nanowires of the flexible sensor are more uniformly distributed on the surface, can be deeply fused with the polymer substrate, and the robustness is effectively improved. Further, by adjusting the density of the three-dimensional space conductive network of the silver nanowires, multilevel detection of muscle, skin, joint and other motion behaviors can be realized, self-adhesion and other functions can be realized by adjusting the network structure of the polymer, and the advantages are obvious.

Description

Technical Field

[0001] This invention relates to the field of flexible sensing technology, specifically to a multi-layered silver nanowire composite flexible motion sensor, its preparation method, and its application. Background Technology

[0002] In recent years, advanced motion sensors have been widely used in wearable devices, human-computer interaction, human health monitoring, and flexible robots. Efficient perception of motion behavior in complex environments is a major challenge for the development of human-machine collaboration. Current depth-sensing technology and rigid inertial devices face numerous bottlenecks, urgently requiring next-generation flexible motion sensing hardware technology for complex environments to promote human-machine integration. Silver nanowires, as a novel nanoconductive material, possess excellent permeability, conductivity, light transmittance, tensile strength, and bending resistance, making them highly suitable as sensitive electronic materials. Flexible motion sensors can be fabricated by combining them with elastic polymers with high elongation at break. Furthermore, the functionality of flexible motion sensors is also crucial. The cumbersome structures and systems resulting from single-function sensors are no longer sufficient to meet the complex application scenarios of modern wearable devices. Therefore, achieving multimodal flexible sensing by adjusting the sensor's composition and structural design is the future development direction for advanced flexible motion sensors.

[0003] Currently, some progress has been made in polymer-based silver nanowire composite materials, for example:

[0004] CN107502017A discloses a silver nanowire-reinforced conductive composite coating of polyacrylate and its preparation method. This invention uses a conventional physical blending method to disperse pre-prepared silver nanowires into a photocurable polyacrylate matrix to prepare the conductive coating. However, this simple blending method requires dispersing a large amount of silver nanowires to obtain a highly conductive material, which is wasteful. Furthermore, the uneven dispersion in this simple physical blending method leads to inconsistent surface resistance, affecting the material's performance. This silver nanowire composite material can only achieve conductivity and cannot realize multi-level flexible motion sensing or human electrophysiological information detection.

[0005] CN107655598B discloses a flexible stress sensor based on a composite conductive film of carbon nanotubes and silver nanowires. The invention uses a spraying method to transfer synthesized carbon nanotubes and silver nanowires onto a flexible PDMS substrate, and then covers the conductive material with another layer of PDMS film. The conductive layer of the flexible sensor prepared by this method is in the middle of the insulating material and cannot come into contact with the human body, so it cannot acquire human electromyographic signals and electrophysiological signals.

[0006] CN111765910A discloses a flexible capacitive sensor with silver nanowires embedded in PDMS. This invention uses rod coating or blade coating to apply a silver nanowire solution onto the PDMS surface to form the upper and lower stages of the capacitive sensor, with PDMS having a micropillar structure serving as the dielectric layer in between, thus constructing a simple capacitive sensor. However, due to its structure, this sensor can only achieve a single flexible sensing function.

[0007] CN110864828A discloses a method for fabricating a silver nanowire / Mxene flexible stress sensor. This invention simply encapsulates conductive materials inside PDMS to fabricate a flexible sensor. This type of sensor can only achieve simple flexible stress and strain sensing, but cannot achieve multi-level stress and strain sensing or detection of human electrophysiological information.

[0008] Currently, depth-of-field camera technology and MEMS inertial devices are the main methods for acquiring motion behavior. However, the former requires the construction of a high-definition camera platform, which limits the application scenarios and is costly; the latter's rigid appearance and the significant difference in modulus between flexible human tissue make it difficult to acquire human motion information accurately and in real time. In addition, the cumbersome structures and systems of flexible stress and strain sensors introduced in recent years, due to their single function, cannot simultaneously achieve the detection of human electrophysiological information and multi-level flexible stress and strain sensing, thus making it difficult to meet the complex application scenarios of today's wearable devices. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a multi-layered silver nanowire composite flexible motion sensor, its fabrication method, and its applications.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] This invention provides a method for fabricating a multilayer silver nanowire composite flexible motion sensor. The method includes drop-casting silver nanowire ink onto a glass substrate after plasma surface treatment to form a conductive silver nanowire coating; then drop-casting an emulsion polymer onto the silver nanowire coating on the glass substrate, followed by curing at 60-80 degrees Celsius to obtain a cured polymer film; finally, peeling the cured polymer film off the glass substrate to obtain the multilayer silver nanowire composite flexible motion sensor.

[0012] Furthermore, the method specifically includes the following steps:

[0013] (1) Prepare a glass plate. After cleaning the glass plate with acetone, ethanol and deionized water, place it in a plasma surface treatment machine and perform plasma surface treatment for 5 min to 10 min to obtain a glass substrate with excellent hydrophilic properties.

[0014] (2) After ultrasonically dispersing the silver nanowire ink for 20 min, 1 mL was dropped onto the glass substrate. After the silver nanowire aqueous dispersion was fully spread on the glass substrate, it was transferred to an oven and dried at 70 degrees for 30 min. Then, a silver nanowire coating was obtained on the glass substrate.

[0015] (3) The emulsion polymer is drop-cast onto the silver nanowire coating. After the emulsion polymer is fully spread on the silver nanowire coating, it is transferred to an oven and cured at 80 degrees for 3 hours. The polymer film is then removed from the glass substrate to obtain a multilayer silver nanowire composite flexible motion sensor.

[0016] Furthermore, the silver nanowire coating has a surface density of 0.5 mg / cm³ on the glass substrate. 2 ~2.5mg / cm 2 .

[0017] Furthermore, the silver nanowire ink is obtained by dispersing silver nanowire powder with a diameter of 30nm to 90nm and a length of 2μm to 20μm in an aqueous solution.

[0018] Furthermore, the components in the emulsion polymer include polyacrylic acid, acrylate polymers, epoxy resins, polyurethanes, or polydimethylsiloxane.

[0019] The present invention also provides a multi-level silver nanowire composite flexible motion sensor prepared by the above-described method for preparing a multi-level silver nanowire composite flexible motion sensor.

[0020] This invention also provides the application of the multi-level silver nanowire composite flexible motion sensor described above in the field of metaverse consumer electronics, which features gesture recognition and follow-up control.

[0021] This invention also provides the application of the multi-layered silver nanowire composite flexible motion sensor described above in the field of medical electronics for acquiring human electrophysiological information.

[0022] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0023] This invention provides a multi-level silver nanowire composite flexible motion sensor, its preparation method, and its applications. The silver nanowires in this flexible sensor are more uniformly distributed on the surface, allowing for deep integration with the polymer substrate and effectively improving robustness. Furthermore, by adjusting the density of the three-dimensional conductive network of the silver nanowires, multi-level detection of muscle, skin, and joint movements can be achieved. Self-adhesion and other features can be achieved by adjusting the network structure of the polymer, gradually enhancing its capabilities and demonstrating significant advantages. Electrodes with ultra-high near-surface three-dimensional conductive network density of silver nanowires can detect human electromyography (EMG) information; electrodes with relatively high near-surface three-dimensional conductive network density of silver nanowires can sense stress and strain in human joint deformation; and electrodes with low near-surface three-dimensional conductive network density of silver nanowires can sense stress and strain in human skin. Attached Figure Description

[0024] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0025] Figure 1 This invention provides a flowchart and design concept for the fabrication of a multi-level silver nanowire composite flexible motion sensor.

[0026] Figure 2 This is a test image of human electrophysiological signals based on an ultra-high density silver nanowire composite flexible motion sensor;

[0027] Figure 3 This is a flexible stress-strain sensing attempt based on a silver nanowire composite flexible motion sensor;

[0028] Figure 4 It is a typical multi-level silver nanowire composite flexible motion sensor. In the figure, (a) is a scanning electron microscope image of the sensor cross section, (b) is a scanning electron microscope image of the sensor surface, (c) is a physical image of the flexible sensor in the bending state, and (d) is a physical image of the flexible sensor in the stretching state.

[0029] Figure 5 This is based on the resistance change of a high-density silver nanowire composite flexible motion sensor under different bending strains, which was repeatedly tested three times under the same conditions.

[0030] Figure 6 This is the response curve of a high-density silver nanowire composite flexible motion sensor to bending motion at different frequencies. Detailed Implementation

[0031] As the background technology shows, the cumbersome structures and systems of flexible stress and strain sensors introduced in recent years, due to their limited functionality, are no longer sufficient to meet the complex application scenarios of modern wearable devices. To address these issues, this invention utilizes casting and transfer processes to uniformly distribute silver nanowires on the near-surface of a polymer film to form a continuous and uniform conductive network. Then, by controlling the three-dimensional network density of the silver nanowires, multi-level flexible motion sensing of muscles, skin, and joints is achieved. This establishes a logical mapping relationship between motion behaviors such as speed, acceleration, and direction and electrical signals, demonstrating broad application prospects in the fields of consumer electronics (gesture recognition, motion control, etc.) and medical electronics (human electrophysiological information acquisition).

[0032] This invention provides a method for fabricating a multilayer silver nanowire composite flexible motion sensor, such as... Figure 1 As shown, the method includes drop-casting a silver nanowire dispersion onto a plasma-treated glass substrate to form a conductive silver nanowire coating; then drop-casting an emulsion polymer onto the silver nanowire coating on the glass substrate, wherein the main component of the emulsion polymer is an acrylate polymer; subsequently curing at 60–80 degrees Celsius to obtain a cured polymer film; finally, peeling the cured polymer film off the glass substrate to obtain a multilayer silver nanowire composite flexible motion sensor.

[0033] This is because the glass substrate treated with plasma has strong hydrophilicity, allowing silver nanowires to be effectively dispersed on the surface to form a three-dimensional conductive network. Since acrylate is a highly polar polymer, after being cast onto the silver nanowire coating, it penetrates into the conductive network. Upon curing, it firmly fixes the silver nanowires to the acrylate surface, forming a conductive network on the surface. Figure 4 As shown, a three-dimensional conductive network formed by silver nanowires can be seen on the polymer surface. Peeling off the cured polymer film yields the silver nanowire polymer composite film electrode, which is the multilayer silver nanowire composite flexible motion sensor of this invention.

[0034] Furthermore, by controlling the density of silver nanowires, ultra-high density (1.5 mg / cm³) nanowires can be prepared. 2 ~2.5mg / cm 2 Silver nanowire flexible motion sensor, high density (1 mg / cm³) 2 ~1.5mg / cm 2 Silver nanowire flexible motion sensor and low density (0.5 mg / cm³) 2 ~1mg / cm 2Silver nanowire flexible motion sensors. Different silver nanowire densities correspond to different surface impedances in flexible motion sensors, thus allowing these membrane electrodes to be applied in various scenarios. Flexible electrodes with low surface impedance can sense muscle electrophysiological information and joint deformation information. Electrodes with high surface impedance can sense micro-deformation information of the skin.

[0035] The present invention will now be described in detail with reference to specific embodiments.

[0036] I. Fabrication scheme of silver nanowire composite flexible motion sensor: The present invention utilizes assisted casting transfer technology to uniformly disperse a silver nanowire conductive network on the surface of a polymer film to prepare a silver nanowire polymer composite film electrode, namely the multi-level silver nanowire composite flexible motion sensor of the present invention.

[0037] A method for fabricating a multilayer silver nanowire composite flexible motion sensor includes the following steps:

[0038] Step (1) Prepare a glass plate. After cleaning the glass plate with acetone, ethanol and deionized water, place it in a plasma surface treatment machine and perform plasma surface treatment for 5 min to 10 min to obtain a glass substrate with excellent hydrophilic properties.

[0039] Step (2) After ultrasonically dispersing the silver nanowire ink for 20 minutes, take 1 mL and drop it onto the glass substrate. After the silver nanowire ink is fully spread on the glass substrate, transfer it to an oven and dry it at 70 degrees for 30 minutes. Then, a silver nanowire coating is obtained on the glass substrate.

[0040] Step (3) The emulsion polymer is drop-cast onto the silver nanowire coating. After the emulsion polymer is fully spread on the silver nanowire coating, it is transferred to an oven and cured at 80 degrees for 3 hours. The polymer film is then removed from the glass substrate and peeled off to obtain a multilayer silver nanowire composite flexible motion sensor.

[0041] II. Electromyographic Information and Multimodal Stress-Strain Information Testing

[0042] 1) Electromyography (EMG)

[0043] The principle of electromuscular signal acquisition is to monitor the electrophysiological signals generated by nerve cells in the muscle system during movement using electrodes attached to the body surface. In this invention, electromuscular signal acquisition is performed by a high-performance and high-density neuromuscular electrophysiological signal acquisition system (NES-64B01, Center for Neural Engineering Research, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences), which is capable of performing multi-channel biosignal acquisition. For example... Figure 2The diagram shows the connection between the sensor and the data acquisition system. When the sensor is attached to the skin of a person's arm, the muscle cells generate electrical signals as the arm moves, which are recorded by the system. By monitoring changes in muscle electrical information during exercise, early warnings of muscle fatigue can be issued.

[0044] 2) Multi-level flexible stress-strain sensing test experiment

[0045] This invention achieves multi-level stress-strain sensing by adjusting the concentration of silver nanowires on the surface of a flexible sensor. When testing minute deformations of the skin, high sensitivity is required, thus necessitating a flexible sensor with a low concentration of surface silver nanowires. When testing joint deformation, where the deformation is greater, the flexible sensor easily yields a stress-strain sensing curve, requiring a flexible sensor with a higher concentration of surface silver nanowires. The specific testing method involves attaching the sensor to the joint and skin, then connecting it to a multimeter. When the body moves, the sensor deforms, causing a change in resistance, which is then displayed on the testing interface as a curve of resistance changing with movement.

[0046] like Figure 3 As shown, due to its high flexibility, repeatability, and sensitivity, the silver nanowire composite flexible motion sensor can be used as a wearable device to monitor various body movements. Composite flexible motion sensors with different silver nanowire densities can detect different motion states. High-density silver nanowire composite flexible motion sensors can respond to joint deformation. Low-density silver nanowire composite flexible motion sensors are more sensitive and can respond to micro-deformations of the skin.

[0047] like Figure 5 and Figure 6 As shown, to test the performance of the silver nanowire composite flexible motion sensor in practical applications, its response state under different strains and motion frequencies was measured. From Figure 5 As can be seen, the relative resistance increases with increasing strain, indicating that the sensor can monitor different amplitudes of motion. From... Figure 6As can be seen, the response curve changes with the motion frequency, indicating that the sensor can respond to the motion frequency in real time. The above test results demonstrate that this sensor has excellent performance in motion monitoring. In summary, this invention belongs to the field of flexible sensing technology, and more specifically, relates to a design and fabrication method of a multi-level silver nanowire composite flexible motion sensor. The silver nanowires in this flexible sensor are more uniformly distributed on the surface and can be deeply integrated with the polymer substrate, effectively improving robustness. Furthermore, by adjusting the three-dimensional conductive network density of the silver nanowires, multi-level detection of muscle, skin, joint, and other motion behaviors can be achieved. Self-adhesion and other features can be achieved by adjusting the network structure of the polymer, gradually enhancing its capabilities and demonstrating significant advantages. This invention provides a multi-mode flexible motion sensor hardware that utilizes the three-dimensional spatial network structure of silver nanowires, aided by casting and transfer techniques, to fabricate stretchable stress-strain sensors with high permeability, wide strain range, and flexible electrodes with low interfacial impedance. This hardware enables precise, efficient, and safe multi-level monitoring of human muscle electrophysiological information, skin micro-deformation information, joint deformation information, and other motion behavior information. It also assists in neural information decoding and machine learning, establishing logical mapping relationships between motion speed, acceleration, direction, and electrical signals. This technology has broad application prospects in consumer electronics fields such as gesture recognition and servo control, as well as in medical electronics fields such as human electrophysiological information acquisition.

[0048] Those skilled in the art will understand that the above-described embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of this application. Any person skilled in the art can make their own modifications and alterations without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A method for fabricating a multi-layered silver nanowire composite flexible motion sensor, characterized in that, The method includes drop-casting silver nanowire ink onto a plasma-treated glass substrate to form a conductive silver nanowire coating; then drop-casting an emulsion polymer onto the silver nanowire coating on the glass substrate, followed by curing at 60-80 degrees Celsius to obtain a cured polymer film; wherein, the silver nanowires in the silver nanowire coating form a three-dimensional conductive network on the polymer surface; finally, the cured polymer film is peeled off from the glass substrate to obtain a multilayer silver nanowire composite flexible motion sensor. Multilevel motion detection is achieved by controlling the surface density of the silver nanowire coating. Among them, a multilevel silver nanowire composite flexible motion sensor with an ultra-high density silver nanowire coating is used for detecting human electromyography (EMG) information. The silver nanowire density of this multilevel silver nanowire composite flexible motion sensor is 1.5 mg / cm³. 2 ~2.5 mg / cm 2 A multi-level silver nanowire composite flexible motion sensor with a high-density silver nanowire coating is used for stress-strain sensing of human joint deformation. The silver nanowire density of the multi-level silver nanowire composite flexible motion sensor with a high-density silver nanowire coating is 1 mg / cm³. 2 ~1.5 mg / cm 2 A multi-layered silver nanowire composite flexible motion sensor with a low-density silver nanowire coating is used for stress and strain sensing on human skin. The silver nanowire density of the multi-layered silver nanowire composite flexible motion sensor with a low-density silver nanowire coating is 0.5 mg / cm³. 2 ~1 mg / cm 2 .

2. The method for fabricating the multilayer silver nanowire composite flexible motion sensor according to claim 1, characterized in that, The method specifically includes the following steps: (1) Prepare a glass plate. After cleaning the glass plate with acetone, ethanol and deionized water, place it in a plasma surface treatment machine and perform plasma surface treatment for 5 min to 10 min to obtain a glass substrate with excellent hydrophilic properties. (2) After ultrasonically dispersing the silver nanowire ink for 20 min, 1 mL was dropped onto the glass substrate. After the silver nanowire ink was fully spread on the glass substrate, it was transferred to an oven and dried at 70 degrees for 30 min. Then, a silver nanowire coating was obtained on the glass substrate. (3) The emulsion polymer is drop-cast onto the silver nanowire coating. After the emulsion polymer is fully spread on the silver nanowire coating, it is transferred to an oven and cured at 80 degrees for 3 hours. The polymer film is then removed from the glass substrate and peeled off to obtain a multilayer silver nanowire composite flexible motion sensor.

3. The method for fabricating a multi-layered silver nanowire composite flexible motion sensor according to claim 2, characterized in that, The silver nanowire coating has a surface density of 0.5 mg / cm³ on the glass substrate. 2 ~2.5 mg / cm 2 .

4. The method for fabricating a multi-layered silver nanowire composite flexible motion sensor according to claim 2, characterized in that, The silver nanowire ink is obtained by dispersing silver nanowire powder with a diameter of 30 nm to 90 nm and a length of 2 μm to 20 μm in an aqueous solution.

5. The method for fabricating a multi-layered silver nanowire composite flexible motion sensor according to claim 2, characterized in that, The components of the emulsion polymer include polyacrylic acid, acrylate polymers, epoxy resins, polyurethanes, or polydimethylsiloxane.

6. The multi-level silver nanowire composite flexible motion sensor prepared by the method described in any one of claims 1 to 5.

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