Polyvinylidene fluoride-trifluoroethylene piezoelectric sensor and preparation method thereof
By using electrospinning and heat treatment to dope PVDF-TrFE fiber membranes with liquid metal EGaIn nanodroplets, the mechanical mismatch and insufficient piezoelectric performance of traditional flexible piezoelectric sensors were solved, enabling high-sensitivity physiological signal detection and large strain monitoring.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-03-13
AI Technical Summary
Existing flexible piezoelectric sensors suffer from mechanical mismatch between electrodes and piezoelectric layers during device assembly and structural design. Furthermore, traditional piezoelectric materials such as PVDF-TrFE have relatively weak piezoelectric responses, making it difficult to meet the requirements for high-sensitivity detection. In addition, the liquid metal doping process presents problems of agglomeration and interface delamination.
By employing liquid metal EGaIn nanodroplets doped with PVDF-TrFE fiber membranes and constructing oriented alignment structures through electrospinning, combined with heat treatment to regulate β-phase crystal growth, stretchable conductive electrodes and flexible encapsulation layers were designed to achieve synergistic optimization of the mechanical flexibility and piezoelectric performance of flexible piezoelectric sensors.
It significantly improves the piezoelectric response and mechanical flexibility of piezoelectric sensors, ensuring structural integrity and performance stability under high strain conditions, and is suitable for human physiological signal monitoring and motion analysis.
Smart Images
Figure CN121655671A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of flexible electronics and sensor technology, specifically relating to a polyvinylidene fluoride-trifluorovinyl piezoelectric sensor and its preparation method. Background Technology
[0002] With the rapid development of the Internet of Things and flexible wearable electronics, flexible sensors capable of human-computer interaction, health monitoring, and motion analysis have become a research hotspot [Bhadwal N, Ben Mrad R, Behdinan K, Nanomaterials, 2023, 13 (24):3170]. Among them, piezoelectric sensors have irreplaceable advantages in wearable devices due to their self-powered characteristic of directly converting mechanical energy into electrical signals without the need for an external power source.
[0003] Existing flexible piezoelectric sensors typically employ a "sandwich" stacked assembly structure, consisting of a central piezoelectric active layer, upper and lower conductive electrode layers, and an outer insulating encapsulation layer. However, this field still faces significant challenges in both device structure assembly and the performance of core materials. Firstly, in terms of device assembly and structural design, the mechanical mismatch between the electrodes and the piezoelectric layer is a key factor restricting the flexibility of sensors. Traditional piezoelectric sensors often use thin films of metals such as gold, copper, and aluminum, or indium tin oxide (ITO) as electrode materials [Zhou T, Wang S, Ao Y, et al., Nano Energy, 2023, 138:110910]. Although these materials have good conductivity, they are inherently rigid or brittle with extremely low elongation at break. When the sensor is attached to areas of high deformation, such as human joints, the rigid electrodes are prone to breakage or interfacial peeling from the flexible piezoelectric layer, leading to signal interruption or a sharp decrease in sensitivity. Therefore, developing a fully flexible integrated structure that uses stretchable electrodes to form a stable interface with the piezoelectric layer is a prerequisite for achieving long-term stable monitoring.
[0004] Secondly, in terms of core piezoelectric materials, both traditional inorganic ceramics and existing polymers have limitations. Although inorganic piezoelectric ceramics such as lead zirconate titanate (PZT) have high piezoelectric coefficients, they are brittle, dense, and contain the toxic element lead, making them difficult to process into flexible films and unsuitable for direct application to human skin. Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), as a typical ferroelectric polymer, has good flexibility, easy processing, and biocompatibility, making it an ideal matrix material for flexible sensors. However, the piezoelectric response of pure PVDF-TrFE is relatively weak, making it difficult to meet the high-sensitivity detection requirements of weak physiological signals [Bhadwal N, Ben Mrad R, Behdinan K, Nanomaterials, 2023, 13 (24):3170].
[0005] To improve the piezoelectric properties of PVDF-TrFE, the current mainstream strategy is to dope it with inorganic rigid fillers (such as BaTiO3 nanoparticles, carbon nanotubes, zinc oxide, etc.). Although these fillers can enhance piezoelectricity through stress concentration effects or by strengthening the local electric field, the introduction of rigid fillers inevitably disrupts the continuity of the polymer matrix. At high filler levels, rigid particles are prone to agglomeration, leading to brittleness and a significant reduction in elongation at break. This causes the modified composite material to lose the original flexibility of PVDF-TrFE, and instead exacerbates the risk of mechanical failure of the sensor during tensile testing.
[0006] In recent years, room-temperature liquid metal gallium-indium eutectic synthesis has attracted attention as a novel "soft filler." Liquid metals combine the infinite deformability of fluids with the high conductivity of metals [Lin Y, Genzer J, Dickey MD, Advanced Science, 2020, 7:2000192 (1-16)]. In existing technologies, liquid metal modification of PVDF-TrFE is mostly achieved through physical blending. In these methods, liquid metals are prone to agglomeration. β The limited PVDF-TrFE content results in less than ideal material properties. Furthermore, the additional polarization required for physical blending increases processing costs and equipment dependence, and can easily lead to matrix interface delamination and reduced material stability. Designing liquid metal-doped PVDF-TrFE composite systems with superior piezoelectric performance, and synergistically achieving mechanical flexibility in piezoelectric devices, remains a pressing issue. Summary of the Invention
[0007] To address the issue that existing flexible piezoelectric sensors rely on rigid fillers, which easily lead to stress concentration and piezoelectric activity... βTo address the technical shortcomings of low phase crystallinity and the difficulty in simultaneously achieving mechanical flexibility and piezoelectric properties, this invention provides a polyvinylidene fluoride-trifluoroethylene piezoelectric sensor and its preparation method. Using a liquid metal-doped PVDF-TrFE fiber membrane as the core sensing material, the assembled flexible piezoelectric sensor achieves synergistic optimization of enhanced piezoelectric response and mechanical flexibility.
[0008] The core design concept of this invention lies in using the fluid properties of liquid metal to replace traditional rigid fillers. This avoids stress concentration from damaging the device's flexibility, and uses liquid metal nanoscale regions as nucleation sites. Combined with the stretching orientation during spinning and the crystal structure control during subsequent heat treatment, this promotes the piezoelectric activity in PVDF-TrFE. β The process involves the directional growth of phase crystals; simultaneously, the directional alignment of fibers is achieved through the coordinated control of parameters in the electrospinning process to enhance structural support; at the assembly design level, an interface modification and integration of stretchable conductive elastomer electrodes and composite fiber membranes is adopted, along with a layered elastic encapsulation structure. The flexible substrate supports the fiber membrane-electrode assembly, and the outer layer uses a viscoelastic encapsulation layer to disperse external forces. Through the synergistic effect of "directional fiber network support + component mechanical matching + encapsulation stress buffering", the structural integrity and piezoelectric performance stability of the device under large strain scenarios are achieved, ultimately achieving a balance between mechanical flexibility and piezoelectric function.
[0009] The technical solution adopted in this invention is as follows: I. A polyvinylidene fluoride-trifluorovinyl piezoelectric sensor The sensor, from the inside out, comprises a piezoelectric thin film layer, stretchable conductive electrode layers on both sides of the piezoelectric thin film layer, and an outermost flexible encapsulation layer. The piezoelectric thin film layer consists of a polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) fiber membrane matrix and gallium-indium eutectic liquid metal (EGaIn) nanodroplets dispersed within the fibers; the PVDF-TrFE... β The crystallinity of the phase is 60%~85% (achieved by controlling the fiber orientation and annealing time and temperature); the fibers have a directional arrangement structure with an average diameter of 150~200 nm; the diameter of the liquid metal is 10 nm-100 nm.
[0010] II. A method for preparing a polyvinylidene fluoride-trifluorovinyl piezoelectric sensor, the steps of which are as follows: (1) The preparation of the piezoelectric thin film layer includes the following steps: (1.1) Dissolve PVDF-TrFE in N,N-dimethylformamide (DMF) at a concentration of 15.3-19.4 wt%; add liquid metal EGaIn at a concentration of 2.9 wt% to 6.5 wt% of the mass of PVDF-TrFE; finally add dispersant polyvinylpyrrolidone (PVP) at a concentration of 3 wt%, and after ultrasonic treatment for 30 minutes and stirring for 2 hours, obtain a uniform spinning solution; In PVDF-TrFE, the molar ratio of PVDF to TrFE is 7:3; (1.2) The spinning solution obtained in step (1.1) is used to prepare a fiber membrane with an oriented structure by electrospinning. (1.3) The fiber membrane obtained in step (1.2) is annealed at a temperature of 120~130℃ for 2~3 hours. (2) Sensor assembly: The fiber membrane obtained in step (1) is cut, and stretchable conductive electrodes are attached to both sides of it and encapsulated with flexible encapsulation material.
[0011] The positive voltage of the electrospinning is 20 kV and the negative voltage is -5 kV; the distance between the needle and the receiving device is 15 cm; the ambient temperature is controlled at 25℃ and the relative humidity is controlled at 40%; the spinning solution is received by a high-speed rotating device, which is a roller with a rotation speed of 1000 rpm.
[0012] The stretchable conductive electrode is a conductive silicone rubber film with an elongation at break of 300%-500%; the flexible encapsulation material is VHB double-sided tape.
[0013] III. Application of a Flexible Piezoelectric Sensor Based on Liquid Metal Doping of PVDF-TrFE The sensor is used in the fields of flexible wearable electronic devices, human physiological signal monitoring, or motion state analysis. Specifically, these sensors are used to monitor vocal cord vibration signals, limb movement gait signals, or joint flexion signals, with a sensitivity of up to 0.424VN. -1 .
[0014] The beneficial effects of this invention are: This invention innovatively employs a composite structure of "directionally arranged PVDF-TrFE fiber matrix + gallium-indium eutectic liquid metal nanodroplets." Uniform dispersion of the liquid metal within the fiber matrix is achieved through dispersant assistance and ultrasonic treatment. The fluid properties of the liquid metal replace traditional rigid fillers, fundamentally avoiding the technical defects of rigid fillers, such as easy agglomeration and stress concentration. The liquid metal nanodroplets can serve as piezoelectric active agents for PVDF-TrFE. βThe nucleation sites of the phase, combined with the subsequent heat treatment process's effect on crystal form regulation, promote... β The efficient generation and directional growth of the phase fundamentally enhance the piezoelectric activity of the material. This structural design achieves synergistic optimization of "dispersion-nucleation effect-piezoelectric activity", solving the core problems of uneven component dispersion and low piezoelectric phase induction efficiency in existing physical mixing modification technologies, and significantly enhancing the correlation between material structure and piezoelectric properties.
[0015] This invention utilizes electrospinning technology to construct a core process system. Through the directional stretching effect during spinning, it achieves the ordered arrangement and microstructure control of PVDF-TrFE fibers, providing stable spatial constraints for the dispersion of liquid metal nanodroplets. Simultaneously, it induces the orientation of polymer molecular chains, laying the structural foundation for the formation of the piezoelectric active phase. The electrospinning process synergistically complements subsequent heat treatment, achieving efficient self-polarization without the need for additional high-voltage polarization steps. This simplifies the preparation process, reduces equipment dependence and energy consumption, and avoids problems such as material interface delamination and decreased stability caused by traditional polarization processes. This process system overcomes the limitations of existing physical blending and additional polarization techniques, constructing a closed loop of "structure control - crystal form optimization - performance enhancement," significantly improving the controllability and consistency of material preparation.
[0016] This invention achieves functional integration of flexible devices through a layered assembly design consisting of a piezoelectric thin film layer, a stretchable conductive electrode layer, and a flexible encapsulation layer. Each layer adheres to the principle of mechanical performance matching, ensuring excellent overall flexibility and structural integrity. The oriented fiber matrix provides strong mechanical support, while the adaptability design of the stretchable conductive electrode and flexible encapsulation layer ensures stable structural connection and performance output even under large deformation scenarios, effectively dispersing external impacts and preventing electrode detachment or encapsulation cracking during stretching. This assembly process overcomes the shortcomings of traditional flexible sensors, such as the imbalance between mechanical and piezoelectric properties after assembly and insufficient long-cycle stability. This allows the device to adapt to large-strain monitoring scenarios like human motion while ensuring reliable performance during long-term use, thus expanding the practical application range of piezoelectric sensors. Attached Figure Description
[0017] Figure 1 This is an electron microscope image of the product obtained in Comparative Example 1.
[0018] Figure 2 This is the XRD pattern of the product obtained in Comparative Example 1.
[0019] Figure 3 These are electron microscope images of the product obtained in Example 1.
[0020] Figure 4 This is a transmission image of the product obtained in Example 1.
[0021] Figure 5 This is the XRD pattern of the product obtained in Example 1.
[0022] Figure 6 This is a stress-strain curve of the product obtained under different amounts of liquid metal addition.
[0023] Figure 7 This is a piezoelectric output voltage diagram of the products obtained under different amounts of liquid metal addition.
[0024] Figure 8 This is the XRD pattern of the product obtained in Example 2.
[0025] Figure 9 This is the XRD pattern of the product obtained in Example 3.
[0026] Figure 10 This is the XRD pattern of the product obtained in Example 4.
[0027] Figure 11 These are electron microscope images of the product obtained in Example 5.
[0028] Figure 12 This is the XRD pattern of the product obtained in Example 5.
[0029] Figure 13 The image shows the signal waveform of the sensor prepared in Example 1 for monitoring human vocalization, movement, and joint activity. Detailed Implementation
[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0031] Example 1 A polyvinylidene fluoride-trifluorovinyl piezoelectric sensor comprises, from the inside out, a piezoelectric thin film layer, stretchable conductive electrode layers located on both sides of the piezoelectric thin film layer, and an outermost flexible encapsulation layer. The piezoelectric thin film layer is composed of a PVDF-TrFE fiber membrane matrix and liquid metal EGaIn nanodroplets dispersed within the fibers; the PVDF-TrFE... β The phase crystallinity is 80.0%; the fibers have a directional arrangement structure with an average diameter of 181 nm; the diameter of the liquid metal is 10~100 nm.
[0032] The preparation method of the polyvinylidene fluoride-trifluorovinyl piezoelectric sensor includes the following steps: (1) Preparation of piezoelectric thin film layer: (1.1) Weigh 2.1 g of PVDF-TrFE particles with a PVDF to TrFE molar ratio of 7:3 and dissolve PVDF-TrFE in 10 mL of DMF. The concentration of PVDF-TrFE is about 17.3 wt%. Add liquid metal EGaIn. The amount of liquid metal EGaIn added is 4.8 wt% of the mass of PVDF-TrFE. Finally, add dispersant PVP. The concentration of PVP is 3 wt% (relative to the mass of PVDF-TrFE). After ultrasonic treatment for 30 minutes and stirring treatment for 2 hours, a uniform spinning solution is obtained. (1.2) Use electrospinning to prepare the spinning solution obtained in step (1.1) into a fiber membrane with an oriented arrangement structure. The positive voltage of electrospinning is 20 kV and the negative voltage is -5 kV. The distance between the needle and the receiving device is 15 kV. cm; the ambient temperature is controlled at 25℃ and the relative humidity is controlled at 40%; the spinning solution is received by a high-speed rotating device, which is a roller with a rotation speed of 1000 rpm; (1.3) the fiber membrane obtained in step (1.2) is annealed at a temperature of 120℃ for 3 hours; (2) sensor assembly: the fiber membrane obtained in step (1) is cut, and stretchable conductive electrodes are attached to both sides of the membrane and encapsulated with flexible encapsulation material; wherein the stretchable conductive electrode is a conductive silicone rubber film and the flexible encapsulation material is VHB double-sided tape.
[0033] Test results: Microstructure (SEM): such as Figure 3 As shown, the fibers prepared by high-speed electrospinning exhibit a highly oriented structure, which is beneficial for the axial orientation of molecular chains; simultaneously, the liquid metal is uniformly distributed in the form of nanodroplets inside and on the surface of the fibers, without obvious large-size agglomerations. Further observation using transmission electron microscopy (TEM) (e.g.) Figure 4 As shown in the figure, the composite fiber surface is smooth and the diameter is uniform, with a measured diameter of approximately 181 nm, confirming the precision of the preparation process of this invention. Crystal structure (XRD): as shown in the figure. Figure 5 As shown, it exhibits extremely strong [property] at θ=21°. β Phase characteristic diffraction peaks, calculated by β The phase content is as high as 80.0%. Piezoelectric properties: such as Figure 7 As shown, under the same pressure, this sample exhibits the highest piezoelectric output voltage compared to other liquid metal addition amounts. Force sensitivity testing reveals a sensitivity of 0.424 VN. -1 Mechanical properties: such as Figure 6 As shown, the material exhibits excellent toughness, with an elongation at break exceeding 150% and a tensile strength reaching 15 MPa.
[0034] Example 2 The preparation method of the polyvinylidene fluoride-trifluorovinyl piezoelectric sensor includes the following steps: (1) Preparation of piezoelectric thin film layer: (1.1) Weigh 2.4 g of PVDF-TrFE particles with a PVDF to TrFE molar ratio of 7:3 and dissolve PVDF-TrFE in 10 mL of DMF. The concentration of PVDF-TrFE is about 19.4 wt%. Add liquid metal EGaIn. The amount of liquid metal EGaIn added is 4.8 wt% of the mass of PVDF-TrFE. Finally, add dispersant PVP. The concentration of PVP is 3 wt% (relative to the mass of PVDF-TrFE). After ultrasonic treatment for 30 minutes and stirring treatment for 2 hours, a uniform spinning solution is obtained. (1.2) Use electrospinning to prepare the spinning solution obtained in step (1.1) into a fiber membrane with an oriented arrangement structure. The positive voltage of electrospinning is 20 kV and the negative voltage is -5 kV. The distance between the needle and the receiving device is 15 kV. cm; the ambient temperature is controlled at 25℃ and the relative humidity is controlled at 40%; the spinning solution is received by a high-speed rotating device, which is a roller with a rotation speed of 1000 rpm; (1.3) the fiber membrane obtained in step (1.2) is annealed at a temperature of 130℃ for 3 hours; (2) sensor assembly: the fiber membrane obtained in step (1) is cut, and stretchable conductive electrodes are attached to both sides of the membrane and encapsulated with flexible encapsulation material; wherein the stretchable conductive electrode is a conductive silicone rubber film and the flexible encapsulation material is VHB double-sided tape.
[0035] Test results: Figure 8 This is the XRD pattern of the product in this embodiment. Figure 5 Compared to the sample annealed at 130℃, β Although the phase diffraction peak intensity was higher than that of the unannealed sample, it was slightly lower than that of Example 1, indicating that the lower temperature resulted in insufficient molecular chain rearrangement. The piezoelectric output voltage was approximately 85% of that of Example 1.
[0036] Example 3 The preparation method of the polyvinylidene fluoride-trifluorovinyl piezoelectric sensor includes the following steps: (1) Preparation of piezoelectric thin film layer: (1.1) Weigh 1.8 g of PVDF-TrFE particles with a PVDF to TrFE molar ratio of 7:3 and dissolve PVDF-TrFE in 10 mL of DMF. The concentration of PVDF-TrFE is about 15.3 wt%. Add liquid metal EGaIn. The amount of liquid metal EGaIn added is 4.8 wt% of the mass of PVDF-TrFE. Finally, add dispersant PVP. The concentration of PVP is 3 wt% (relative to the mass of PVDF-TrFE). After ultrasonic treatment for 30 minutes and stirring treatment for 2 hours, a uniform spinning solution is obtained. (1.2) Use electrospinning to prepare the spinning solution obtained in step (1.1) into a fiber membrane with an oriented arrangement structure. The positive voltage of electrospinning is 20 kV and the negative voltage is -5 kV. The distance between the needle and the receiving device is 15 kV. cm; the ambient temperature is controlled at 25℃ and the relative humidity is controlled at 40%; the spinning solution is received by a high-speed rotating device, which is a roller with a rotation speed of 1000 rpm; (1.3) the fiber membrane obtained in step (1.2) is annealed at a temperature of 120℃ for 2 hours; (2) sensor assembly: the fiber membrane obtained in step (1) is cut, and stretchable conductive electrodes are attached to both sides of the membrane and encapsulated with flexible encapsulation material; wherein the stretchable conductive electrode is a conductive silicone rubber film and the flexible encapsulation material is VHB double-sided tape.
[0037] Test Results Figure 9 The image shows the XRD pattern of the product from this embodiment. Data shows that the characteristic peak intensity of the sample annealed for 2 hours is lower than that of the sample annealed for 3 hours. Figure 5 This indicates that at 120℃, a holding time of 2 hours is insufficient for crystal growth to reach its optimal state.
[0038] Example 4 Compared with Example 1, the only difference is the amount of liquid metal EGaIn added in step (1.1). In this example, the amount of liquid metal EGaIn added is 2.9 wt% of the mass of PVDF-TrFE, and the other steps and parameters remain unchanged.
[0039] Test results: Figure 10 The XRD pattern of the product in this embodiment is shown. The intensity of the β-phase diffraction peak under low doping content is significantly lower than that in Example 1, and calculations show that its... β The phase content is approximately 65%. This indicates that the lower concentration of liquid metal provides fewer nucleation sites and has a limited inducing effect on crystallization.
[0040] Example 5 Compared with Example 1, the only difference is the amount of liquid metal EGaIn added in step (1.1). In this example, the amount of liquid metal EGaIn added is 6.5 wt% of the mass of PVDF-TrFE, and the other steps and parameters remain unchanged.
[0041] Test results: Figure 11 The SEM image of the product in this embodiment clearly shows that the liquid metal droplets exhibited significant aggregation. Figure 12 The XRD pattern of the product in this embodiment shows a decrease in diffraction peak intensity. β The phase content decreased to approximately 40%. This is because excessive liquid metal aggregates hindered the orderly arrangement of molecular chains and suppressed [the process / function]. β Phase formation.
[0042] Comparative Example 1 Compared with Example 1, the only difference is that liquid metal EGaIn is not added in step (1.1) (the amount added is 0), and only pure PVDF-TrFE nanofiber membrane is prepared. The other steps and parameters remain unchanged.
[0043] Test results: Figure 1 The SEM image of the comparative product shows that the surface of the pure PVDF-TrFE fiber is smooth and free of particles. Figure 2 The XRD pattern for this comparative example is shown. β The phase diffraction peak intensity is the weakest among all samples, and calculations show that its... β The phase content is only 36.4%. Piezoelectric performance tests show that it has the lowest output voltage and low elongation at break, proving that the introduction of liquid metal plays a key role in improving piezoelectric performance and flexibility.
[0044] Application Example 1 To verify the comprehensive sensing performance of the flexible piezoelectric sensor prepared in this invention under different force modes (micro-vibration, vertical pressure, and large-strain tension), the following three application scenarios were constructed for testing (see attached specification). Figure 13 ): 1. Vocal cord vibration monitoring (verifying high sensitivity): A sensor was attached to the skin surface of the volunteer's throat. When the volunteer pronounced different words such as "Hello" and "Thanks," the throat muscles produced micron-level weak vibrations. Figure 13 b). Test results: The sensor can accurately capture the minute mechanical vibration and output a voltage signal with a clear waveform and distinguishable characteristics. Moreover, the waveforms corresponding to different words have unique fingerprint characteristics.
[0045] Experimental conclusion: This demonstrates that the sensor has extremely high voltage sensitivity and is capable of detecting weak physiological signals and performing speech recognition.
[0046] 2. Plantar Pressure Monitoring (Verifying Impact Resistance and Wide Measurement Range): The sensor was placed at the heel of the volunteer's athletic shoe insole to monitor plantar pressure signals during "walking" and "running" activities. Test Results: The sensor output periodic voltage pulse signals. During running, due to the increased vertical impact force of the foot on the sensor, the output voltage amplitude was significantly higher than during walking (approximately 2-3 times that during walking), and the signal remained stable during prolonged exercise without structural damage. Figure 13 c).
[0047] Experimental conclusion: This demonstrates that the sensor has a robust structure, excellent shock resistance, and a wide pressure response range, making it suitable for gait analysis.
[0048] 3. Joint Bending Monitoring (Verifying High Flexibility and Large Strain Capacity): The sensor was tightly attached to the volunteer's wrist joint using VHB tape, and the tensile response of the wrist at different bending angles (70°, 50°, 30°) was monitored. Test Results: When the wrist was bent downwards, the sensor underwent tensile deformation along with the skin, outputting a negative voltage peak. Experimental data showed a significant positive correlation between the output voltage amplitude and the wrist bending angle: the larger the bending angle, the greater the tensile strain on the sensor, and the stronger the generated electrical signal. Figure 13 e).
[0049] Experimental conclusion: This demonstrates that the sensor of the present invention (especially the PVDF-TrFE / liquid metal composite layer and conductive silicone rubber electrode) has excellent mechanical flexibility and can still function normally under large strain, making it very suitable for human joint range of motion monitoring and human-computer interaction control.
Claims
1. A polyvinylidene fluoride-trifluorovinyl piezoelectric sensor, characterized in that: The sensor comprises, from the inside out, a piezoelectric thin film layer, stretchable conductive electrode layers located on both sides of the piezoelectric thin film layer, and an outermost flexible encapsulation layer. The piezoelectric thin film layer consists of a polyvinylidene fluoride-trifluoroethylene fiber membrane matrix and gallium indium eutectic liquid metal nanodroplets dispersed in the fibers.
2. The polyvinylidene fluoride-trifluorovinyl piezoelectric sensor according to claim 1, characterized in that: The polyvinylidene fluoride-trifluoroethylene, i.e., PVDF-TrFE β The crystallinity of the phase is 60%~85%; The fiber membrane has an oriented structure and an average diameter of 150-200 nm. The liquid metal has a diameter of 10 nm to 100 nm.
3. The method for preparing the polyvinylidene fluoride-trifluorovinyl piezoelectric sensor according to claim 1, characterized in that, Includes the following steps: 1) Fabrication of piezoelectric thin film layer: 1.1) Polyvinylidene fluoride-trifluoroethylene was dissolved in N,N-dimethylformamide, and gallium indium eutectic liquid metal and polyvinylpyrrolidone dispersant at a concentration of 3 wt% were added respectively. After ultrasonic treatment for 30 minutes and stirring treatment for 2 hours, a uniform spinning solution was obtained. 1.2) Using electrospinning, the spinning solution obtained in step 1.1) is prepared into a pre-treated fiber membrane with an oriented structure; 1.3) The fiber membrane obtained in step 1.2) is annealed to obtain the final fiber membrane; 2) Sensor assembly: The fiber membrane obtained in step 1) is cut into a piezoelectric thin film layer, stretchable conductive electrodes are attached to both sides of the piezoelectric thin film layer, and the outer layer is encapsulated with a flexible encapsulation material.
4. The method for preparing the polyvinylidene fluoride-trifluorovinyl piezoelectric sensor according to claim 3, characterized in that: In step 1.1), the molar ratio of polyvinylidene fluoride to trifluoroethylene in polyvinylidene fluoride-trifluoroethylene is 7:3, and the concentration of polyvinylidene fluoride-trifluoroethylene is 15.3-19.4 wt%.
5. The method for preparing the polyvinylidene fluoride-trifluorovinyl piezoelectric sensor according to claim 3, characterized in that: In step 1.1), the amount of gallium-indium eutectic liquid metal added is 2.9 wt% to 6.5 wt% of the mass of polyvinylidene fluoride-trifluoroethylene.
6. The method for preparing the polyvinylidene fluoride-trifluorovinyl piezoelectric sensor according to claim 3, characterized in that: In step 1.3), the annealing temperature is 120-130℃ and the annealing time is 2-3 hours.
7. The method for preparing the polyvinylidene fluoride-trifluorovinyl piezoelectric sensor according to claim 3, characterized in that: In step 1.2), the positive voltage of electrospinning is 20 kV and the negative voltage is -5 kV; the ambient temperature is controlled at 25℃ and the relative humidity is controlled at 40%. The spinning solution is received by a high-speed rotating device. The distance between the needle and the receiving device is 15 cm. The high-speed rotating receiving device is a roller with a rotation speed of 1000 rpm.
8. The method for preparing the polyvinylidene fluoride-trifluorovinyl piezoelectric sensor according to claim 3, characterized in that: In step 2), the stretchable conductive electrode is a conductive silicone rubber film with an elongation at break of 300%-500%; the flexible encapsulation material is VHB double-sided tape.
9. The application of the polyvinylidene fluoride-trifluorovinyl piezoelectric sensor according to claim 1, characterized in that: The sensor is applied in flexible wearable electronic devices, human physiological signal monitoring, or motion state analysis; specifically, it includes sensors for monitoring vocal cord vibration signals, limb movement gait signals, or joint flexion signals, with a sensitivity of up to 0.424 VN. -1 .