A deformation couple for a flexible strain sensor, and a manufacturing method and application thereof

Abstract

The present application belongs to the field of flexible strain sensing, and particularly relates to a deformation couple for a flexible strain sensor, a manufacturing method thereof and an application thereof. The deformation couple for the flexible strain sensor comprises two polymer films adhered to each other face to face. Both of the polymer films have good ductility and flexibility. The two polymer films have different adsorption capacities for electrons during deformation. The manufacturing method of the deformation couple comprises preparing two polymer films, applying a liquid form of one of the polymer films on one of the films to adhere the two films. The application of the deformation couple for the flexible strain sensor comprises sensing the movement of a joint or a muscle, or sensing the writing of a finger or a pen point thereon. The present application has excellent flexibility and stretchability, can adapt to various complex movements and deformations, and meanwhile maintains stable performance. The present application has a self-power supply characteristic, and does not need an external power supply.

Description

Technical Field

[0001] This invention belongs to the field of flexible strain sensing technology, specifically relating to the structural design of a deformation couple for flexible strain sensors and its application in the field of self-powered sensing. Background Technology

[0002] Flexible sensors have significant applications in fields such as human health monitoring, electronic skin, human-computer interaction, and voice recognition. However, most current sensors rely on external power sources, which severely limits their flexibility and portability in practical applications. Therefore, self-powered sensors capable of harvesting energy from human movement are considered an ideal choice for the next generation of flexible sensors.

[0003] Triboelectric nanogenerators (TENGs), as an emerging low-frequency energy harvesting device, can continuously convert mechanical energy (such as wind energy, sound energy, and human movement) in the environment into electrical energy. Therefore, TENGs can be applied to self-powered sensors. However, traditional TENGs require a metal foil as a conductive layer, resulting in poor flexibility and almost no stretchability. For flexible sensors, especially in applications requiring large deformations, high flexibility and stretchability are essential characteristics. Therefore, there is an urgent need for a new sensor structure with good flexibility and ductility, while also being able to stably and spontaneously output electrical signals during deformation. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art by providing a flexible strain sensor, its preparation method and application. The preparation process is simple, universal, and low in cost, and it has excellent flexibility and tensile properties.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A deformation coupler for a flexible strain sensor includes two polymer films adhered face-to-face; both polymer films have good ductility and flexibility; the two polymer films have different electron adsorption capacities during deformation; at least one polymer film is connected to a wire for outputting an electrical signal generated during deformation.

[0007] Furthermore, the flexible polymer film has an elongation of over 100% and remains intact at a bending angle of 180°, and can naturally recover after being stretched and folded.

[0008] Furthermore, the polymer film is made of one of the following materials: Ecoflex 00-50 silicone rubber film, polydimethylsiloxane (PDMS) film, thermoplastic polyurethane (TPU) film, nitrile rubber (NBR) film, polyacrylamide (PAM) hydrogel, polyvinyl alcohol (PVA) hydrogel, MXene / silicone composite film, MXene / PDMS composite film, MXene / TPU composite film, MXene / NBR composite film, MXene / PAM hydrogel composite film, and MXene / PVA hydrogel composite film.

[0009] Furthermore, the two polymer films have the same thickness, with one polymer film having a thickness of 0.3 mm to 0.8 mm; the total thickness of the deformation coupler used for the flexible strain sensor is 0.6 mm to 1.6 mm.

[0010] Furthermore, the flexible strain sensor prepared by combining the two polymer films can generate a voltage signal of at least 0.6V when stretched or folded, due to the different adsorption capacities for electrons, allowing electrons to migrate from one film to another.

[0011] This invention also proposes a method for preparing the aforementioned deformation couple for flexible strain sensors, comprising the following steps:

[0012] Step 1: Identify the two types of polymers to be used in the preparation of polymer films;

[0013] Step 2: Take two polymers and make polymer films of a specified shape, denoted as film A and film B respectively; take one of the polymers in liquid form and apply it to the opposite surfaces of film A or film B, with the coating thickness controlled between 0.05mm and 0.2mm; then firmly bond film A and film B face to face.

[0014] Step 3: Take at least one wire and fix one end of the wire to the outer surface of one of the polymer films.

[0015] Furthermore, both film A and film B are rectangular in shape, with a length of 30mm-60mm and a width of 10mm-30mm.

[0016] Furthermore, in step two, after firmly bonding film A and film B face to face, heat at 50℃-80℃ for 3-30 minutes to ensure effective bonding between the two, and then allow them to cool naturally.

[0017] Furthermore, the step in step one of determining the two types of polymers used to prepare the polymer film is as follows:

[0018] Step 1: Prepare Ecoflex 00-50 silicone rubber film, polydimethylsiloxane (PDMS) film, thermoplastic polyurethane (TPU) film, nitrile rubber (NBR) film, polyacrylamide (PAM) hydrogel, polyvinyl alcohol (PVA) hydrogel, MXene / silicone composite film, MXene / PDMS composite film, MXene / TPU composite film, MXene / NBR composite film, MXene / PAM hydrogel composite film, and MXene / PVA hydrogel composite film respectively;

[0019] Step 2: Combine any two of the prepared films to prepare a flexible strain sensor;

[0020] Step 3: Apply 200% tensile deformation and 150° folding to each combination of flexible strain sensors; if the voltage signal generated by the two film combinations under tensile or folding deformation is greater than 0.6V, then the two film combinations are considered to meet the performance requirements and can be used to prepare flexible strain sensors.

[0021] The present invention also proposes the application of a deformation coupler for a flexible strain sensor, wherein the end of the wire of the deformation coupler is connected to a digital multimeter, the deformation coupler is fixed to the surface of a human joint or muscle to sense the movement of the joint or muscle, or the deformation coupler is laid flat and fixed on a working plane to sense the writing of a finger or pen tip on it.

[0022] This invention provides a deformation coupler with good flexibility and ductility that does not require an external power source. Its working principle is as follows:

[0023] Two different polymer films, both possessing good flexibility and ductility, are adhered together. During stretching or bending deformation, the two polymer films exhibit different electron adsorption capacities, leading to electron transfer between them and generating an electrical signal. A wire connected to the polymer films outputs this signal. The magnitude of the electrical signal is determined by the amount of deformation of the polymer film, thus allowing the sensing of strain in both the polymer film and the object it adheres to.

[0024] Existing flexible strain sensors mainly include resistive, capacitive, triboelectric, and piezoelectric types. Triboelectric sensors, based on the principle of triboelectric nanogenerators (TENGs), utilize the coupling effect of contact electrification and electrostatic induction between two different triboelectric materials during contact and separation to generate induced charges between electrodes and output an electrical signal. Piezoelectric sensors are similar in principle to this invention, but there are differences. Piezoelectric flexible strain sensors utilize the charge separation that occurs during deformation, outputting an instantaneous voltage signal. While charge separation occurs within a single material, in this invention, two types of polymer films adhere together. Due to deformation, electrons transfer between the two materials, generating an electrical signal and sensing deformation. This principle is somewhat similar to a thermocouple, where a temperature difference causes electrons to transfer between materials, generating an electromotive force (voltage) in the circuit, thus forming a current and producing an electrical signal. This invention utilizes the different electron adsorption capacities of the two thin film materials during deformation, prompting electron transfer between the two materials and generating an electrical signal.

[0025] The beneficial effects of this invention are:

[0026] This invention not only enriches the structural design of wearable sensors but also provides a novel design approach for self-powered sensors, overcoming the shortcomings of poor flexibility and insufficient tensile strength in conventional self-powered sensors. Compared with traditional wearable sensors, the self-powered deformation coupler sensor prepared in this invention has the following significant advantages:

[0027] 1. Excellent flexibility and stretchability: Thanks to the use of polymer films with good stretchability, the sensor can adapt to various complex movements and deformations while maintaining stable performance.

[0028] 2. Self-powered characteristics: No external power supply is required. The sensor can generate electrical signals through its own deformation, realizing true self-powered sensing characteristics.

[0029] 3. The process is simple and efficient. It only requires bonding two triboelectric layers with tensile properties together to form a self-powered sensor, without the need for a metal conductive layer.

[0030] 4. Stable and reliable: Unlike flexible sensors based on triboelectric nanogenerators, deformation couplers do not have electrode friction or contact-separation processes during testing, so they will not wear out and are stable and reliable.

[0031] 5. It can output continuously changing signals: Unlike flexible sensors based on triboelectric nanogenerators, deformation couplers do not output electrical signals at the instant of contact separation, but continuously output signals related to deformation, which can accurately measure the magnitude of deformation. Attached Figure Description

[0032] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0033] Figure 1 This invention describes the mechanism by which the deformation coupler generates electrical signals during deformation.

[0034] Figure 2 The voltage signal generated by stretching or folding the deformation coupler of Embodiment 1 of the present invention; wherein (a) is the voltage signal generated by stretching, (b) is the linear relationship between voltage and elongation, (c) is the voltage signal generated by folding, and (d) is the linear relationship between voltage and folding angle.

[0035] Figure 3 The voltage signal generated by stretching or folding the deformation coupler of Embodiment 2 of the present invention; wherein (a) is the voltage signal generated by stretching, (b) is the linear relationship between voltage and elongation, (c) is the voltage signal generated by folding, and (d) is the linear relationship between voltage and folding angle.

[0036] Figure 4 The voltage signal generated by stretching or folding the deformation coupler of Embodiment 3 of the present invention; wherein (a) is the voltage signal generated by stretching, (b) is the linear relationship between voltage and elongation, (c) is the voltage signal generated by folding, and (d) is the linear relationship between voltage and folding angle.

[0037] Figure 5 The voltage signal generated by stretching or folding the flexible varistor of Embodiment 4 of the present invention; wherein (a) is the voltage signal generated by stretching, (b) is the linear relationship between voltage and elongation, (c) is the voltage signal generated by folding, and (d) is the linear relationship between voltage and folding angle.

[0038] Figure 6 The image shows the XRD pattern of the MXene / silicone composite membrane in Example 5 of this invention.

[0039] Figure 7 The images shown are scanning electron microscope images and corresponding elemental distribution maps of the fractured surface of the MXene / silicone composite film in Embodiment 5 of the present invention; where (a) is a scanning electron microscope image, (b) is an elemental distribution map of Si, and (c) is an elemental distribution map of Ti.

[0040] Figure 8 The voltage signal generated by stretching or folding the deformable coupler in Embodiment 5 of the present invention is shown in (a) and (b) respectively.

[0041] Figure 9The voltage signal generated by stretching or folding the deformable coupler in Comparative Example 1 of the present invention is shown in (a) as the voltage signal generated by stretching and (b) as the voltage signal generated by folding.

[0042] Figure 10 The voltage signal generated by stretching or folding the deformable coupler in Comparative Example 2 of the present invention is shown in (a) as the voltage signal generated by stretching and (b) as the voltage signal generated by folding.

[0043] Figure 11 In Example 1 of this invention, the deformation coupler is used to monitor the voltage signal generated by human movement.

[0044] Figure 12 In Example 2 of this invention, the deformation coupler is used to identify the voltage signal generated during writing. Detailed Implementation

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art are within the scope of protection of the present invention.

[0046] like Figure 1 As shown, a deformation coupler for a flexible strain sensor includes two polymer films adhered face-to-face; the polymer films are flexible films; both polymer films have good extensibility and flexibility, and the two polymer films have different electron adsorption capacities during deformation; at least one polymer film is connected to a wire for outputting the electrical signal generated during deformation; good extensibility and flexibility means that the elongation of the polymer film is above 100%, and it remains intact at a bending angle of 180°, and can naturally recover after being stretched and folded.

[0047] A flexible strain sensor prepared by combining two polymer films can generate a voltage signal of at least 0.6V when stretched or folded, as electrons migrate from one film to the other due to their different adsorption capacities.

[0048] The two polymer films in a flexible strain sensor have the same thickness, with one polymer film having a thickness of 0.3 mm to 0.8 mm; the total thickness of the deformation couple used in the flexible strain sensor is 0.6 mm to 1.6 mm. Film A and film B are rectangular in shape, each with a length of 30 mm to 60 mm and a width of 10 mm to 30 mm.

[0049] The polymer films selected in this invention are made of Ecoflex 00-50 silicone rubber film, polydimethylsiloxane (PDMS) film, thermoplastic polyurethane (TPU) film, nitrile rubber (NBR) film, polyacrylamide (PAM) hydrogel, polyvinyl alcohol (PVA) hydrogel, MXene / silicone composite film, MXene / PDMS composite film, MXene / TPU composite film, MXene / NBR composite film, MXene / PAM hydrogel composite film, and MXene / PVA hydrogel composite film; the conductors are generally silver wires. The manufacturing methods for MXene / silicone composite film, MXene / PDMS composite film, MXene / TPU composite film, MXene / NBR composite film, MXene / PAM hydrogel composite film, and MXene / PVA hydrogel composite film are similar, all involving mixing two raw materials in a certain proportion, pouring the mixture into a mold, and then heating and curing.

[0050] The above-mentioned method for preparing a deformation couple for a flexible strain sensor includes the following steps:

[0051] Step 1: Identify the two types of polymers to be used in the preparation of polymer films;

[0052] Step 2: Prepare polymer films of specified shapes from two polymers, denoted as Film A and Film B. Take the liquid form of one of the polymers and apply it to the opposite surfaces of Film A or Film B, controlling the thickness to be between 0.05mm and 0.2mm. Then, firmly bond Film A and Film B face to face and heat at 50℃-80℃ for 3-30 minutes to ensure effective adhesion. Afterward, allow them to cool naturally. The specific heating temperature and time can be adjusted according to the characteristics of different materials, or a uniform heating condition of 80℃ for 30 minutes can be used. Taking the liquid form of Film A as an example, after application and curing, the total thickness of Film A should be controlled within 0.3mm-0.8mm. Preliminary experiments showed that this coating thickness is very thin, usually around 0.1mm, and this thickness variation has no impact on the performance of the deformation coupler.

[0053] Step 3: Take at least one wire and fix one end of the wire to the outer surface of one of the polymer films.

[0054] This invention bonds two polymer films together. Utilizing the difference in their electron adsorption capabilities, electrons transfer between the two polymer films during stretching or bending deformation, forming an electrical signal. The magnitude of this signal is determined by the deformation of the polymer films, thus it can be used as a strain sensor. The deformation coupler for flexible strain sensors and its preparation method of this invention are applicable not only to the twelve films mentioned in this invention but also to all film materials with certain tensile properties, showing broad application prospects. Examples and comparative examples of different polymer films are given below.

[0055] Example 1

[0056] In Example 1, the two polymer films used in the deformation coupler of the flexible strain sensor are an Ecoflex 00-50 silicone rubber film and a TPU film, respectively. The preparation process is as follows:

[0057] Step 1: Cut the Ecoflex 00-50 silicone rubber film and TPU film into rectangles of 47mm × 22mm, then firmly bond the Ecoflex 00-50 silicone rubber film and TPU film together; when stacking, align all edges of the two polymer films; the thickness of the Ecoflex 00-50 silicone rubber film and TPU film are 0.5mm respectively;

[0058] Step 2: Use a silver wire and fix one end of it to the TPU film to transmit the electrical signals generated during the deformation process.

[0059] Test steps:

[0060] The other end of the silver wire of the deformation coupler used in this embodiment for the flexible strain sensor is connected to a digital multimeter for real-time voltage signal transmission. Different degrees of stretching or folding deformation are applied to the deformation coupler used in the flexible strain sensor, and the resulting voltage signals are recorded by the digital multimeter.

[0061] This invention is the first to propose bonding two triboelectric layers together for use as a self-powered sensor. Therefore, previous research on the use of triboelectric nanogenerators in self-powered sensors or flexible sensors lacked direct metrics to describe the performance of the deformation coupler of this invention. Thus, in this invention, to characterize its sensitivity, we use the relationship between the voltage output value and the measured deformation. In all embodiments, we plotted the relationship between different degrees of stretching or folding and the output voltage, performed linear fitting, and calculated and presented the sensitivity accordingly.

[0062] Test results:

[0063] like Figure 2As shown, the deformation coupler for flexible strain sensors prepared in this embodiment can generate voltage signals of 4.3V and 9.07V under 200% tension and 150° folding conditions, respectively. Furthermore, within the range of 100%-200% tension and 0-150° folding, there is a good linear relationship between the output value and the measured deformation (R0). 2 =0.9931 and 0.98722). The sensitivities were 0.03406 V / strain and 0.06917 V / °, respectively. Furthermore, under 200% tensile conditions, a corresponding voltage signal was also generated when the silver wire was fixed to an Ecoflex 00-50 silicone rubber film. This indicates that the fixing position of the silver wire has no significant effect on the output voltage signal of the deformation coupler used in the flexible strain sensor.

[0064] It should be noted that when using this invention as a sensor, it can be folded at any angle. However, during testing, the clamps of the testing instrument need to fix both ends of the deformation couple. If folded to 180°, the two clamps fixing the film will be squeezed together, causing damage to the instrument. Therefore, in all embodiments of this invention, only 150° was tested.

[0065] Example 2

[0066] In Example 2, the two polymer films used to fabricate the deformation couple are a thermoplastic polyurethane (TPU) film and a polydimethylsiloxane (PDMS) film, respectively. The dimensions and thicknesses of the two polymer films, as well as the fabrication and testing methods for the deformation couple, are the same as in Example 1.

[0067] Test results: such as Figure 3 As shown, the deformation coupler prepared in this embodiment can generate voltage signals of 2.43V and 9.28V under 200% stretching and 150° folding conditions, respectively. Furthermore, within the range of 100%-200% stretching and 0-150° folding, there is a good linear relationship between the output value and the measured deformation (R0). 2 =0.99907 and 0.99779). The sensitivities were 0.02868 V / strain and 0.068 V / °, respectively. Furthermore, under 200% tensile conditions, a corresponding voltage signal was also generated when the silver wire was fixed to the PDMS film. This indicates that the fixing position of the silver wire has no significant effect on the output voltage signal of the deformation coupler.

[0068] Example 3

[0069] In Example 3, the two polymer films used to fabricate the deformation couple are a thermoplastic polyurethane (TPU) film and an nitrile rubber (NBR) film, respectively. The dimensions and thicknesses of the two polymer films, as well as the fabrication and testing methods for the deformation couple, are the same as in Example 1.

[0070] Test results: such as Figure 4 As shown, the deformation coupler prepared in this embodiment can generate voltage signals of 1.4V and 1.7V under 200% stretching and 150° folding conditions, respectively. Furthermore, within the range of 100%-200% stretching and 0-150° folding, there is a good linear relationship between the output value and the measured deformation (R0). 2 =0.98538 and 0.99189). The sensitivities were 0.01511 V / strain and 0.01272 V / °, respectively. Furthermore, under 200% tensile conditions, a corresponding voltage signal was also generated when the silver wire was fixed to the NBR film. This indicates that the fixing position of the silver wire has no significant effect on the output voltage signal of the deformation coupler.

[0071] Example 4

[0072] In Comparative Example 4, the two polymer films used to fabricate the deformation couple were an nitrile rubber (NBR) film and a polydimethylsiloxane (PDMS) film, respectively. The dimensions and thicknesses of the two polymer films, as well as the fabrication and testing methods for the deformation couple, were the same as in Example 1.

[0073] Test results: such as Figure 5 As shown, the deformation coupler prepared in this embodiment can generate voltage signals of 0.56V and 5.2V under 200% stretching and 150° folding conditions, respectively. Furthermore, within the range of 100%-200% stretching and 0-150° folding, there is a good linear relationship between the output value and the measured deformation (R0). 2 =0.98454 and 0.99363). The sensitivities were 0.00679 V / strain and 0.03508 V / °, respectively. Furthermore, under 200% tensile conditions, a corresponding voltage signal was also generated when the silver wire was fixed to the PDMS film. This indicates that the fixing position of the silver wire has no significant effect on the output voltage signal of the deformation coupler.

[0074] Example 5

[0075] In Example 5, the two polymer films used in the fabricated deformation coupler sensor are a silicone film and an MXene / silicone composite film. The MXene / silicone composite film is prepared by combining a novel two-dimensional material—Ti3C2Tx MXene—with an Ecoflex00-50 silicone rubber film. The dimensions and thicknesses of the two polymer films, as well as the fabrication and testing methods for the deformation coupler sensor, are the same as in Example 1.

[0076] The preparation method of the MXene / silicone composite film is as follows:

[0077] Components A and B of Ecoflex 00-50 silicone rubber liquid were placed in a beaker at a 1:1 weight ratio and stirred thoroughly until completely mixed. Then, 6% (by weight of Ecoflex 00-50 silicone rubber) of monolayer MXene powder was added, and the mixture was stirred vigorously until the liquid silicone and MXene powder were completely and evenly mixed. Next, the mixed MXene liquid silicone was placed in a vacuum environment and vacuumed to remove air bubbles. Then, the bubble-free MXene liquid silicone was poured into a mold consisting of two glass plates and a 0.5mm thick silicone gasket. Finally, the mold was placed on a heating plate at 80°C and heated for 30 minutes to polymerize and solidify the MXene liquid silicone.

[0078] The XRD pattern of the MXene / silicone composite film is as follows: Figure 6 As shown, the scanning electron microscope image of the fractured surface of the MXene / silicone composite film (MXene:TPU mass ratio = 6%) and the corresponding EDS spectrum are as follows: Figure 7 As shown in (a) and (b), the XRD patterns of the MXene / silicone composite film indicate that MXene was successfully embedded in the silicone matrix, forming a uniform composite structure. SEM images reveal the microstructure of the composite film, while EDS spectroscopy further confirms the uniform distribution of MXene within the film. These results demonstrate the successful preparation of the MXene / silicone composite film.

[0079] Test results: such as Figure 8 As shown, the deformation coupler prepared in this embodiment can output maximum voltage signals of 0.65V and 1.63V under conditions of 200% stretching and 150° folding, respectively.

[0080] Comparative Example 1

[0081] In Comparative Example 1, both polymer films used in the fabricated deformation coupler were Ecoflex 00-50 silicone rubber films. The dimensions and thicknesses of the two polymer films, as well as the fabrication and testing methods for the deformation coupler, were the same as in Example 1.

[0082] Test results: such as Figure 9 As shown, the fabricated strain gauge can generate voltage signals of 0.03V and 0.21V under 200% stretching and 150° folding conditions, respectively. Since the voltage signals generated by both thin film combinations under tensile or folding deformation are less than 0.6V, these two thin film combinations are considered to fail to meet the performance requirements and cannot be used to fabricate flexible strain sensors.

[0083] The sensor in Comparative Example 1 has significantly weaker electrical output performance. This is because the two polymer films are made of the same material and have the same triboelectric polarity. During deformation, there is almost no electron transfer between them, resulting in poor electrical output performance.

[0084] Comparing Example 5 and Comparative Example 1, it is evident that the addition of MXene significantly improves the output performance of the deformation coupler, demonstrating the effectiveness of MXene in enhancing the electrical output performance of deformation couplers. The addition of MXene significantly enhances the voltage output capability of the deformation coupler under tensile and folding deformation, providing a new approach for the design of high-performance flexible strain sensors.

[0085] Comparative Example 2

[0086] In Comparative Example 2, the two polymer films used to fabricate the deformation couple were an Ecoflex 00-50 silicone rubber film and a polydimethylsiloxane (PDMS) film, respectively. The dimensions and thicknesses of the two polymer films, as well as the fabrication and testing methods for the deformation couple, were the same as in Example 1.

[0087] Test results: such as Figure 10 As shown, the deformation coupler sensor prepared in Example 2 can generate voltage signals of 0.16V and 0.24V under 200% stretching and 150° folding conditions, respectively. Since the voltage signals generated by both thin film combinations under tensile or folding deformation are less than 0.6V, it is considered that these two thin film combinations do not meet the performance requirements and cannot be used to prepare flexible strain sensors.

[0088] in conclusion:

[0089] The test results from the above embodiments and comparative examples demonstrate that the deformation coupler can generate corresponding voltage signals based on different degrees of applied tensile or folding deformation, and the signal values ​​exhibit good responsiveness and repeatability. The fixed position of the silver wire is independent of the output voltage signal, further proving the simplicity of the sensor fabrication method and the accuracy and reliability of the sensing signal.

[0090] Meanwhile, the electrical output performance of deformation couples made from combinations of different types of polymer films varies. When there is only a small amount of electron transfer between the two materials, the output performance will be poor (e.g., Comparative Example 1, Comparative Example 2). To obtain easily observable results, we consider that when the voltage signal generated by the combination of two polymer films under tensile or folding deformation is greater than 0.6V, the combination of these two films is considered to meet the performance requirements and can be used to prepare flexible strain sensors. This invention does not list all the deformation couples that can be composed of the twelve materials given. Whether a deformation couple made from a specific pair of materials can be used as a flexible strain sensor requires actual fabrication of the deformation couple and measurement of the output voltage. We present a novel technical concept for fabricating wearable flexible sensors and provide a sensor with a novel structure. If any material not listed in this invention, or any new material that may emerge in the future, can be used to fabricate the deformation coupler described in this invention, and if a 200% tensile deformation and a 150° fold are applied to this deformation coupler, and if the voltage signal generated by the combination of the two thin films under tensile or folding deformation is greater than 0.6V, then the combination of the two thin films is considered to meet the performance requirements and can be used to fabricate a flexible strain sensor. Therefore, it should be considered to conform to the technical concept of this invention, and the material should also fall within the scope of protection of the pending claims of this invention. Application Example 1

[0091] Application Example 1 provides a practical application of a deformation coupler prepared from the Ecoflex 00-50 silicone rubber film and MXene / silicone composite film of Example 5 in human motion monitoring. The deformation coupler undergoes varying degrees of deformation due to the movement of human joints or muscles, thereby generating electrical signals to achieve real-time monitoring of human motion status.

[0092] like Figure 11 As shown, the prepared deformation coupler is used as a flexible strain sensor and fixed to a human joint (such as a finger). Figure 11 a) Fist ( Figure 11 b) Wrist ( Figure 11 c) the Adam's apple (Fig. 111e) or muscles (such as the arm) Figure 11 d) Face ( Figure 11 f) Surface. When the human body performs movements such as joint bending or muscle contraction, the sensor deforms accordingly. This deformation triggers charge transfer within the sensor, generating corresponding electrical signals. By monitoring these electrical signals in real time, the dynamic changes in human movement can be accurately captured and analyzed.

[0093] This flexible strain sensor has significant advantages in human motion monitoring:

[0094] (1) High sensitivity: Deformation couplers can respond quickly to small deformations and output clear electrical signals even in low-amplitude joint movements or small muscle contractions.

[0095] (2) Real-time monitoring: The electrical signal output of the deformation coupler is synchronized with the human body movement, which can reflect the movement status in real time and is suitable for dynamic monitoring and real-time feedback.

[0096] (3) Wide applicability: This deformation coupler can be used in a variety of human motion monitoring scenarios, such as rehabilitation training, motion analysis, and health monitoring.

[0097] In summary, this deformation-coupled sensor can accurately monitor deformations caused by joint bending and muscle movement, and convert them into electrical signals. The intensity and frequency of these electrical signals are highly correlated with the amplitude and frequency of human movement, thus providing reliable data support for the quantitative analysis of human movement.

[0098] Application Example 2

[0099] This embodiment provides a deformation coupler prepared using the Ecoflex 00-50 silicone rubber film and MXene / silicone composite film from Example 5, and applies it to a practical writing recognition scenario. This deformation coupler achieves accurate recognition of written content by detecting the pressure and speed of the pen tip during writing. In the application scenario of this Example 2, the deformation coupler can be larger.

[0100] Application process:

[0101] First, use Kapton tape to secure the deformation coupler to the tabletop, ensuring the surface is flat and firmly attached. Then, write the letter combinations "MXene" and "HPU" on the surface of the deformation coupler, respectively. For example... Figure 11 As shown in (a) and (b), a dot (·) represents gentle writing, double short lines (--) represent quick and continuous rewriting, and a single short line (-) represents quick single rewriting.

[0102] During writing, the pressure applied by the pen tip and the speed of its movement directly affect the degree of deformation of the varistor. These factors cause the varistor to deform to varying degrees. Because the Ecoflex 00-50 silicone rubber film and the MXene / silicone composite film have different triboelectric properties, deformation promotes the redistribution and transfer of charge between their surfaces. Therefore, when the pen tip acts on the surface of the varistor, the varistor can output a voltage peak with a specific shape and size depending on the intensity and frequency of the deformation.

[0103] When the letter combinations "MXene" and "HPU" were written on the surface of the deformation sensor, respectively, they formed the following patterns: Figure 11The voltage signals shown in (a) and (b) can be further analyzed and processed to identify the content being written or the writer's writing habits.

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

Claims

1. A deformation coupler for use in flexible strain sensors, characterized in that: The invention comprises two polymer films adhered face-to-face; both polymer films have good extensibility and flexibility; the two polymer films have different electron adsorption capacities during deformation; at least one polymer film is connected to a wire for outputting electrical signals generated during deformation; the polymer films have an elongation of over 100% and remain intact at a bending angle of 180°, and can naturally recover after being stretched and folded. The flexible strain sensor prepared by combining two polymer films can generate a voltage signal of at least 0.6V during stretching or folding because of the different adsorption capacities for electrons, allowing electrons to migrate from one film to another. Furthermore, there is a good linear relationship between the output value and the measured deformation within the 100%-200% stretching range, and a good linear relationship between the output value and the measured deformation within the 0-150° folding range. The polymer film material and its pairing combination are one of the following two: Combination 1: The two polymer films are made of Ecoflex 00-50 silicone rubber and polyacrylamide (PAM), respectively. Combination 2: The two polymer films are made of polydimethylsiloxane (PDMS) and nitrile rubber (NBR), respectively.

2. The deformation coupler for a flexible strain sensor according to claim 1, characterized in that: The two polymer films have the same thickness, and the thickness of one polymer film is 0.3mm-0.8mm; the total thickness of the deformation coupler used for the flexible strain sensor is 0.6mm-1.6mm.

3. A method for preparing a deformation couple for a flexible strain sensor as described in any one of claims 1 to 2, characterized in that, Includes the following steps: Step 1: Identify the two types of polymers to be used in the preparation of polymer films; Step 2: Take two polymers and make polymer films of a specified shape, denoted as film A and film B respectively; take one of the polymers in liquid form and apply it to the opposite surfaces of film A or film B, with the coating thickness controlled between 0.05mm and 0.2mm; then firmly bond film A and film B face to face. Step 3: Take at least one wire and fix one end of the wire to the outer surface of one of the polymer films.

4. The method for preparing a deformation couple for a flexible strain sensor according to claim 3, characterized in that: Both film A and film B are rectangular in shape, with a length of 30mm-60mm and a width of 10mm-30mm.

5. The method for preparing a deformation couple for a flexible strain sensor according to claim 3, characterized in that: In step two, after bonding film A and film B tightly face to face, heat at 50℃-80℃ for 3-30 minutes to ensure effective bonding between the two, and then allow them to cool naturally.

6. The method for preparing a deformation couple for a flexible strain sensor according to claim 3, characterized in that: Step one includes the following steps: Step A: Prepare Ecoflex 00-50 silicone rubber film, polyacrylamide (PAM) film, polydimethylsiloxane (PDMS) film, and nitrile rubber (NBR) film respectively; Step B: Fabricate a flexible strain sensor using the thin films prepared above in the following combination: Combination 1: Ecoflex 00-50 silicone rubber, polyacrylamide (PAM); Combination 2: Polydimethylsiloxane (PDMS), Nitrile butadiene rubber (NBR); Step C: Apply 200% tensile deformation and 150° folding to each combination of flexible strain sensors; if the voltage signal generated by the two film combinations under tensile or folding deformation is greater than 0.6V, then the two film combinations are considered to meet the performance requirements and can be used to prepare flexible strain sensors.

7. An application of a deformation coupler for a flexible strain sensor as described in any one of claims 1 to 2, characterized in that: Connect the end of the wire of the deformation coupler to a digital multimeter, fix the deformation coupler to the surface of a human joint or muscle to sense the movement of the joint or muscle, or lay the deformation coupler flat on a working surface and use the deformation coupler to sense the writing of a finger or pen tip on it.

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