A self-powered sensor based on a mechanical metamaterial structure design and a preparation method and application thereof

Abstract

This invention discloses a self-powered sensor based on a mechanical metamaterial structure, its fabrication method, and its applications, specifically relating to the fields of flexible electronics and new energy technologies. Its core is a "sandwich" integrated structure. From bottom to top, it consists of a lower PTFE layer, a middle functional polymer electrode layer, and an upper PTFE layer. Through the strong adhesion of the electrode layers, the three layers form a conformally bonded elastic composite. This invention uses an oriented PTFE fiber membrane, a mechanical metamaterial, as the core functional layer, integrating it with a stretchable electrode. This solves the bottleneck problem of traditional sensors struggling to operate stably under dynamic deformation, and is applied to wearable devices, energy harvesting, and self-powered sensing systems. The aim is to provide a flexible sensing device that combines high electrical output performance, excellent mechanical tensile resilience, and environmental adaptability.

Description

Technical Field

[0001] This invention relates to the fields of flexible electronics and new energy technology, and in particular to a self-powered sensor based on a mechanical metamaterial structure design, its fabrication method, and its application. Background Technology

[0002] Self-powered sensing devices directly output the electrical signals generated by relative motion or contact separation between contact layers as sensing signals, enabling effective monitoring of human movement without an external power source. Flexible sensors, due to their ability to withstand complex deformations such as stretching and torsion, and their conformability to the human body, are ideal for powering wearable devices or serving as self-driven sensors. Polytetrafluoroethylene (PTFE) is the most electronegative material among common materials, capable of generating high output voltages. However, its dense, rigid form is hard and almost inextensible. Existing solutions, such as doping PTFE fragments into elastomers, disrupt its continuous charge storage capacity, leading to a significant decrease in output performance; directly using other intrinsically stretchable but less electronegative materials makes it difficult to achieve high electrical output.

[0003] 1. The limited selection of stretchable negatively charged materials restricts the strength of the sensing signal. To achieve intrinsic stretchability, most studies tend to use elastomers such as Ecoflex and PDMS as the negative charge layer of sensors. Although these materials have good flexibility, their electronegativity in the electrical sequence is much weaker than that of polytetrafluoroethylene (PTFE), resulting in lower surface charge density and output voltage of the device. This limits the signal generation capability of the sensor and makes it difficult to meet the requirements of high-sensitivity sensing.

[0004] 2. The superior sensing performance of PTFE contradicts its inherent instretchability. PTFE is one of the most electronegative and ideal negative layer materials, capable of generating high surface charge density, providing a basis for high signal-to-noise ratio in sensors. However, PTFE films themselves have poor mechanical resilience. Existing strategies involve doping PTFE in powder or fragment form into elastomers to form composite layers, but the PTFE phase is isolated, failing to form a continuous charge interface, severely compromising its charge retention capability. This results in attenuated and unstable sensor output signals, affecting the accuracy of monitoring data.

[0005] 3. Design difficulties of integrated stretchable electrodes An ideal stretchable electrode needs to possess high conductivity, high strain tolerance, and strong adhesion to PTFE to ensure stable transmission of sensing signals. However, existing electrodes all have shortcomings: metal-based electrodes are prone to cracking under strain, leading to sensor signal interruption; carbon-based composite electrode electrodes have high initial resistance and large signal loss; and for various conductive polymer materials, if they are only bonded to the low surface energy PTFE through simple physical lamination, the interfacial adhesion is usually weak, which seriously affects the stability and reliability of sensor signals.

[0006] 4. Insufficient resistance to complex deformation limits the long-term reliability of the sensor. Wearable sensors need to withstand complex stresses such as repeated stretching and bending. Existing stretchable sensor structures (such as "rigid island-elastic connection" or simple lamination) are prone to stress concentration or interface delamination after multiple deformations, leading to mechanical fatigue and signal attenuation, which poses a serious challenge to the stability and reliability of sensors in long-term dynamic monitoring.

[0007] Chinese patent application CN112414294A discloses a method for preparing a highly sensitive sandwich-type strain sensor based on hydrogel and carbon materials. The method involves ultrasonically dispersing carbon materials in a dispersant solution, pouring the dispersion into a mold made of polymethyl methacrylate and silicone rubber, and allowing it to air dry at room temperature to prepare a carbon material deposition layer. Polyvinyl alcohol is dissolved in a mixed solution of glycerol and deionized water, and then polymerizable monomers, crosslinking agents, and an initiator, ammonium persulfate, are added while continuously stirring. Finally, the mixed prepolymer solution is injected between two layers of carbon material deposited in the mold, heated, and polymerized. The mold is then placed in a low-temperature freeze for a period of time. After thawing, a composite material with a carbon / hydrogel / carbon sandwich structure is obtained. Wires are connected to both ends to obtain the highly sensitive strain sensor. However, this patent does not mention improvements to the stable operation of the electrical sensor under dynamic deformation, therefore further improvements are needed. Summary of the Invention

[0008] The technical problem to be solved by this invention is how to overcome the bottleneck problem that traditional sensor devices are difficult to operate stably under dynamic deformation.

[0009] The present invention solves the above-mentioned technical problems through the following technical means: The first aspect of the present invention provides a self-powered sensor with a stacked structure, comprising, from bottom to top: a first PTFE layer, an intermediate functional polymer electrode layer, and a second PTFE layer. The first PTFE layer and the second PTFE layer are both obtained by plasma treatment of PTFE thin films. The intermediate functional polymer electrode layer comprises SBMA, PEGDA, glycerol, PEDOT:PSS, and a photoinitiator. The thickness ratio of the first PTFE layer, the intermediate functional polymer electrode layer, and the second PTFE layer is (0.2-0.4):(0.9-1.0):(0.2-0.4).

[0010] Preferably, the plasma treatment is performed in a plasma cleaner by introducing oxygen or air and treating for 1-3 minutes at a power of 100-300 W.

[0011] Preferably, the intermediate functional polymer electrode layer is composed of SBMA, PEGDA, glycerol, PEDOT:PSS and a photoinitiator; the mass ratio of SBMA, PEGDA, glycerol, PEDOT:PSS and the photoinitiator is 0.3-0.9:0.005-0.02:0.3-0.7:1:0.001-0.01, more preferably 0.7:0.01:0.5:1:0.005.

[0012] Further preferably, the photoinitiator is an ultraviolet photoinitiator, specifically one or more of Irgacure 2959, Irgacure 369, and Irgacure 651.

[0013] Irgacure 2959, with CAS number 106797-53-9, is a further preferred option.

[0014] Preferably, the thickness ratio of the first PTFE layer, the intermediate functional polymer electrode layer, and the second PTFE layer is 0.3:1.0:0.3. More preferably, the thicknesses are 0.3 mm, 1.0 mm, and 0.3 mm, respectively.

[0015] The thickness of each layer directly affects the electric field distribution and charge collection efficiency of the device. There is an optimal thickness for the functional polymer layer (approximately 1.0 mm), at which both voltage and current outputs reach their peak values, reflecting a balance between charge storage capacity and device flexibility. When the PTFE layer thickness is 0.3 mm, the device achieves the highest and most stable voltage output (peak value > 40 V). If the layer is too thin (0.1 mm), the conductive network is incomplete, resulting in a weak signal; if it is too thick (0.5 mm), it may weaken the induced electric field and is not conducive to flexible bonding.

[0016] A second aspect of this invention provides a method for fabricating a self-powered sensor, comprising the following steps: (1) Preparation of PTFE (polytetrafluoroethylene) mechanical metamaterials: After cleaning the PTFE raw material, it is subjected to uniaxial stretching under heating; heat treatment is then performed to obtain a PTFE film. (2) PTFE film surface pretreatment: The PTFE film obtained in step (1) is cleaned and dried; then subjected to plasma treatment. (3) Preparation of intermediate functional polymer electrode layer precursor solution: Weigh out SBMA, PEGDA, glycerol, and PEDOT:PSS solution, add photoinitiator, stir, and obtain precursor solution; (4) Assembly of integrated devices and in-situ molding of functional layers: Fix the PTFE film obtained in step (2), then coat the precursor solution obtained in step (3) onto the surface of the PTFE film; then cover it with another layer of PTFE film; apply pressure; irradiate with ultraviolet light; and you will get the product.

[0017] Preferably, in step (1), the heating temperature is set to 250℃-300℃.

[0018] Preferably, in step (1), the unidirectional stretching rate is 10% / min-200% / min, and the total stretching ratio is 3-10:1.

[0019] This process causes the PTFE molecular chains to be highly oriented along the stretching direction and form a microporous-fiber network.

[0020] Preferably, in step (1), the heat treatment method is to treat at 200℃-250℃ for 5-30 min.

[0021] To eliminate internal stress and stabilize the microstructure, a stable PTFE oriented fiber membrane (i.e., PTFE mechanical metamaterial) is obtained. This step transforms the intrinsically rigid PTFE into a mechanical metamaterial with a microfiber-porous network, enabling it to achieve stretchability on a macroscopic scale, thus resolving the fundamental contradiction between the intrinsic properties of the material and application requirements.

[0022] Preferably, in step (2), the cleaning method is ultrasonic cleaning with anhydrous ethanol.

[0023] Preferably, in step (2), the drying method is to dry with nitrogen gas.

[0024] Preferably, in step (2), the plasma treatment method is to introduce oxygen or air into a plasma cleaner and treat it for 1-3 minutes at a power of 100-300 W.

[0025] Introducing polar groups (hydroxyl, carboxyl) into the surface enhances its adhesion to the polymer layer; plasma treatment introduces active groups into the PTFE surface, enabling it to form a strong conformal interface with the functional layer, rather than simple lamination. This is the key process to ensure that the layers work together, the interface does not separate, and the signal does not attenuate under dynamic deformation.

[0026] Preferably, in step (3), the mass ratio of SBMA, PEGDA, glycerol, PEDOT:PSS, and photoinitiator is 0.3-0.9:0.005-0.02:0.3-0.7:1:0.001-0.01.

[0027] Preferably, in step (3), the PEDOT:PSS solution is a PEDOT:PSS aqueous dispersion solution, wherein the mass fraction of PEDOT:PSS is 1%.

[0028] Preferably, in step (3), the CAS number of SBMA is 3637-26-1; the CAS number of PEGDA is 26570-48-9; and the CAS number of PEDOT:PSS is 155090-83-8.

[0029] Preferably, in step (3), the stirring method is to stir at room temperature with a speed of 500-1000 rpm / min in the dark for 5-10 min.

[0030] Preferably, in step (4), the pressure is applied by applying a pressure of 0.01-0.05 MPa to remove air bubbles.

[0031] Preferably, in step (4), the ultraviolet treatment method is to irradiate with 365 nm ultraviolet light at an intensity of 50-100 mW / cm² for 3-5 minutes.

[0032] Two pretreated PTFE films (upper and lower layers) are integrated with a functional polymer precursor solution and then cured using a photocuring process. Specifically, the lower PTFE film is first fixed, and the prepared precursor solution is uniformly coated onto its surface, with the wet film thickness optimized to 0.5-1.5 mm by controlling the coating amount. Then, the upper PTFE film is applied, and a uniform pressure of 0.01-0.05 MPa is applied to ensure tight interlayer contact and eliminate air bubbles. Finally, the film is irradiated with ultraviolet light at a wavelength of 365 nm and an intensity of 50-100 mW / cm² for 3-5 minutes. This photocuring process induces in-situ polymerization of the precursor solution, forming a functional layer with conductivity, elasticity, and strong interfacial adhesion. This layer forms a strong chemical and physical bond with the activated PTFE surface, ultimately resulting in a structurally complete, integrated stretchable sensor.

[0033] The third aspect of this invention proposes the application of a self-powered sensor based on a mechanical metamaterial structure designed by the above-described preparation method in wearable devices, energy harvesting, and self-powered sensing.

[0034] The beneficial effects of this invention are as follows: 1. Solving the core contradiction of high sensitivity and stretchability: Through structural innovation of mechanical metamaterials, the intrinsically non-stretchable PTFE film participates in large deformation as a continuous phase. It directly utilizes its strong electronegativity to provide high surface charge density, ensuring that the sensor can still generate a high output signal (open circuit voltage >40V) far exceeding that of traditional flexible materials (such as Ecoflex and PDMS) under stretching conditions.

[0035] 2. Achieving stable interface integration and reliable sensing performance through integrated structural design. Employing an integrated structural design, the interfacial stability of the sensing electrodes and the overall reliability of the device under complex deformation are simultaneously optimized. A functional material with high conductivity, intrinsic stretchability, and strong interfacial adhesion is used as the intermediate layer, forming a robust conformal interface with the activated PTFE friction layer. This design effectively suppresses signal attenuation caused by interlayer slippage or separation during dynamic deformation. Thanks to this integrated configuration, the functional layers maintain coordinated deformation when subjected to complex stresses such as repeated stretching, bending, and torsion. This ensures resistance fluctuations of less than 10% under strain exceeding 100% and performance degradation of less than 5% after thousands of cycles, significantly improving the mechanical durability and long-term operational stability necessary for wearable sensors.

[0036] 3. Practical applications of the device in motion sensing and self-powered fields: The device is developed into a self-powered flexible sensing unit that can monitor physiological signals such as joint movement in real time without the need for an external power source, and can directly drive low-power electronic devices, providing miniaturized solutions for fields such as health monitoring.

[0037] 4. When external mechanical force is applied to the sensor, the functional polymer layer undergoes elastic deformation, which in turn causes the PTFE mechanical metamaterial layer to deform in tandem. In the contact-separation working mode, charges are generated and collected, forming an electrical signal output.

[0038] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0039] Figure 1 This is a shear adhesion force diagram of the electrode layer in Embodiment 1 of the present invention; Figure 2 This is a diagram showing the electrode layer conductivity at different SBMA concentrations in Example 1 of the present invention. Figure 3This is a characterization diagram of the electrical properties of the electrode layer in Embodiment 1 of the present invention; Figure 4 This is the electrical output diagram of the sensor in Embodiment 1 of the present invention; Figure 5 This is a stress cycle diagram of the sensor in Embodiment 1 of the present invention; Figure 6 The output diagrams are shown for the sensor under different deformations in Embodiment 1 of the present invention. Figure 7 This is a cyclic stability diagram during the stretching process of Embodiment 1 of the present invention; Figure 8 The charging curve of the sensor capacitor in Embodiment 1 of the present invention; Figure 9 This is a diagram of a small electronic device driven by a self-powered sensor, as shown in Embodiment 1 of the present invention. Figure 10 This is a diagram of the sensor used for motion monitoring in Embodiment 1 of the present invention; Figure 11 This is a schematic diagram of the working principle of the sensor in Embodiment 1 of the present invention; Figure 12 This is a schematic diagram of the basic structure of the sensor in Embodiment 1 of the present invention; Figure 13 This is a flowchart of the electrode fabrication process in Embodiment 1 of the present invention; Figure 14 This is a microscopic morphology diagram of the PTFE layer mechanical metamaterial in Embodiment 1 of the present invention; Figure 15 The diagram shows the electric field distribution and charge collection efficiency of sensors fabricated with PTFE layers of different thicknesses in Example 1 of this invention. Figure 16 The diagram shows the electric field distribution and charge collection efficiency of the sensors prepared with intermediate functional polymer layers of different thicknesses in Example 1 of this invention. Figure 17 The sensor sensitivity test diagram prepared in Example 1 of this invention; Figure 18 The output power characteristic diagram of the sensor prepared in Embodiment 1 of the present invention; Figure 19 The image shows the cyclic stability test results of the sensor prepared in Example 1 of this invention. Figure 20 This is a comparison diagram of the output of the PTFE layer prepared in Example 1 of the present invention with other types of negative electrode materials; Figure 21 This is a comparison diagram of the output stability of the PTFE layer and silicone rubber prepared in Example 1 of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art.

[0041] Unless otherwise specified, the test materials and reagents used in the following examples are commercially available or prepared by known methods.

[0042] Unless otherwise specified, all techniques or conditions described in the embodiments can be performed in accordance with the techniques or conditions described in the literature in this field or in the product manual. Unless otherwise specified, the quantitative experiments in the following embodiments are all repeated three times or more, and the results are averaged.

[0043] Material and equipment preparation in this embodiment of the invention: Main materials: Unstretched PTFE blank: 1 mm thick.

[0044] PEDOT:PSS aqueous solution: concentration 1.3 wt%.

[0045] SBMA (sulfobetaine methacrylate): Purity >98%.

[0046] PEGDA (polyethylene glycol diacrylate, Mn = 700): used as a crosslinking agent.

[0047] Glycerin: analytical grade.

[0048] Photoinitiator: Irgacure 2959.

[0049] Equipment: Plasma cleaner, planetary mixer, ultraviolet curing chamber (wavelength 365 nm, light intensity 80 mW / cm²) 2 ), drying oven, precision electronic balance, coating equipment.

[0050] Example 1: This embodiment provides a method for fabricating a self-powered sensor based on a mechanical metamaterial structure design, including the following steps: Step 1: Preparation of PTFE mechanical metamaterial thin films Unstretched PTFE preforms with a thickness of 1.0 mm were cut to the required size. The preforms were preheated in an oven at 290℃ for 10 minutes. They were then stretched in a single direction at 285℃ at a rate of 50% / min, with a total stretch ratio controlled at 5:1. The stretched film was then heat-set at 230℃ for 15 minutes. After cooling, a self-made PTFE metamaterial film with a uniform microfiber structure and a thickness of approximately 0.3 mm was obtained. This film exhibited excellent flexibility and stretchability, providing an ideal substrate for subsequent sensor fabrication.

[0051] Step 2: PTFE film surface pretreatment The PTFE metamaterial film obtained in step one was ultrasonically cleaned with anhydrous ethanol and dried with nitrogen. Then, the cut PTFE film (2cm × 2cm) was placed in the plasma cleaning chamber, and oxygen was introduced as the treatment gas. The film was treated at 150 W for 2 minutes. After treatment, the hydrophilicity of the PTFE film surface was significantly improved, and the next step should be performed as soon as possible to prevent surface energy decay.

[0052] Step 3: Preparation of Functional Polymer Electrode Precursor Solution Weigh each component precisely according to the following mass ratio: PEDOT:PSS, SBMA, PEGDA, glycerol, and photoinitiator (Irgacure 2959) in a mass ratio of 1:0.7:0.01:0.5:0.005. Mix them together, and place the mixture in a planetary mixer. Stir at 800 rpm in the dark for 5 minutes at room temperature until a homogeneous, viscous, light blue precursor solution is formed. The solvent addition process is as follows. Figure 13 As shown.

[0053] Step 4: Assembly and UV curing of the integrated device A plasma-treated PTFE film (as the lower layer) is fixed onto a clean glass plate. Using a pipette, an appropriate amount of precursor solution is drawn and evenly coated onto the surface of the lower PTFE film. A doctor blade is used to control the wet film thickness to approximately 1.2 mm (target dry film thickness approximately 1.0 mm). Another plasma-treated PTFE film (as the upper layer) is quickly placed over the coated solution. A pressure of approximately 0.02 MPa is gently applied, and the upper PTFE film is slowly pushed to remove interlayer air bubbles and ensure tight contact between the three layers.

[0054] The entire assembly was transferred to a UV curing chamber and irradiated for 4 minutes at a wavelength of 365 nm and a light intensity of 80 mW / cm². The UV light initiated a polymerization reaction, solidifying the precursor solution into a hydrogel, forming an integrated sandwich structure device firmly bonded to the upper and lower PTFE films (see schematic diagram). Figure 12 (As shown).

[0055] This invention also proposes a self-powered sensor based on a mechanical metamaterial structure designed using the above-described preparation method. From bottom to top, the structure comprises: a PTFE layer, an intermediate functional polymer electrode layer, and another PTFE layer. The intermediate functional polymer electrode layer and the PTFE layer are prepared using the above-described method. The thickness of the PTFE layer is 0.3 mm, and the thickness of the intermediate functional polymer electrode layer is 1.0 mm. The microstructure of the PTFE layer is shown in the figure below. Figure 14 As shown.

[0056] The working principle of the self-powered sensor based on the mechanical metamaterial structure design prepared in this invention is as follows: Figure 11 As shown.

[0057] Example 2: The difference between this embodiment and Embodiment 1 is that in step one, the film is stretched in a single direction at a rate of 10% / min under an environment of 250°C, with the total stretch ratio controlled at 3:1. The stretched film is then heat-set at 200°C for 30 minutes.

[0058] The sensor prepared in this embodiment has similar performance to that in Example 1.

[0059] Example 3: The difference between this embodiment and Embodiment 1 is that in step one, the film is stretched in a single direction at a rate of 200% / min under an environment of 300°C, with the total stretch ratio controlled at 10:1. The stretched film is then heat-set at 300°C for 5 minutes.

[0060] The sensor prepared in this embodiment has similar performance to that in Example 1.

[0061] Example 4: The difference between this embodiment and Embodiment 1 is that in step three, the mass ratio of PEDOT:PSS, SBMA, PEGDA, glycerol, and photoinitiator is 1:0.3:0.005:0.3:0.001.

[0062] The sensor prepared in this embodiment has similar performance to that in Example 1.

[0063] Example 5: The difference between this embodiment and Embodiment 1 is that in step three, the mass ratio of PEDOT:PSS, SBMA, PEGDA, glycerol, and photoinitiator is 1:0.9:0.02:0.7:0.01.

[0064] The sensor prepared in this embodiment has similar performance to that in Example 1.

[0065] Example 6: The difference between this embodiment and Embodiment 1 is that in step two, the plasma treatment method is to introduce air into a plasma cleaner and treat it for 3 minutes at a power of 100 W.

[0066] The sensor prepared in this embodiment has similar performance to that in Example 1.

[0067] Example 7: The difference between this embodiment and Embodiment 1 is that in step two, the plasma treatment method is to introduce oxygen into a plasma cleaner and treat it for 1 minute at a power of 300 W.

[0068] The sensor prepared in this embodiment has similar performance to that in Example 1.

[0069] Performance Tests and Results 1. Electrical output performance test A linear motor was used to drive the device in a periodic contact-separation motion (frequency 1 Hz, spacing 2 cm). The open-circuit voltage and short-circuit current of the device were measured using an electrometer and a multimeter.

[0070] The results are as follows Figure 4 As shown: The device prepared in Example 1 exhibits stable electrical output performance, with a peak open-circuit voltage of 44 V and a peak short-circuit current of approximately 0.5 μA.

[0071] 2. Tensile stability test The device was clamped at both ends on a universal tensile testing machine and subjected to a 50% cyclic tensile test (frequency 0.5 Hz), while its voltage output was monitored in real time.

[0072] The results are as follows Figure 7 As shown: During 600 cycles of tensile testing, the output voltage waveform of the device prepared in Example 1 remained stable, and the peak voltage decay rate was less than 2%, demonstrating its excellent mechanical durability.

[0073] 3. Practical Application Demonstration Energy harvesting: The AC power generated by the self-powered sensor based on the mechanical metamaterial structure design prepared in Example 1 was converted into DC power through a rectifier bridge circuit to charge a 22μF commercial capacitor. The results are as follows: Figure 8 , 9 As shown, after manually tapping the device for about 30 seconds, the electrical energy stored in the capacitor can power an LCD electronic watch to work normally for more than 10 seconds.

[0074] Motion monitoring: The self-powered sensor based on a mechanical metamaterial structure designed in Example 1 was attached to the joint of the test subject. Results are as follows: Figure 10As shown, when the test subject performs repetitive joint movements such as knee flexion (90°) and knee extension, the device can generate regular and repeatable electrical signals, clearly distinguishing different movement states.

[0075] like Figure 1 The functional polymer layer prepared in Example 1 of this invention exhibits excellent adhesion properties to various substrates. Specifically, the peak adhesion force to PTFE is close to 4 N, and it also shows good adhesion to common materials such as copper and glass. This demonstrates that the functional polymer material can form a very strong interfacial bond with PTFE, effectively solving the interfacial bonding problem between stretchable electrodes and high-performance PTFE.

[0076] like Figure 2 The functional polymer electrode material prepared in Example 1 of this invention exhibits excellent conductivity. Its conductivity remains consistently high, ranging from 50 mS / m to 95 mS / m, across a wide range of SBMA concentrations from 30% to 90%. This significant conductivity ensures that the electrode, when used as a sensor, can achieve efficient charge collection and low-loss signal transmission.

[0077] like Figure 3 The functional polymer electrode prepared in Example 1 of this invention exhibits a consistently low relative rate of change in resistance (ΔR / R) during 1000 stretch-release cycles. Locally, ΔR / R shows only minor fluctuations (<0.5%). This demonstrates that the electrode possesses excellent electrical stability and fatigue resistance under repeated large deformations, and its conductive network remains intact during cyclic stretching.

[0078] like Figure 4 The sensor shown in Embodiment 1 of this invention is constructed based on a PTFE oriented fiber membrane (mechanical metamaterial), successfully combining PTFE's inherently strong electronegativity with its stretchable mechanical properties. This mechanical metamaterial structure, through directional stretching of PTFE, forms a highly oriented microfiber-porous network internally, enabling it to possess macroscopic elasticity while retaining the inherent high surface charge density of PTFE, thus generating a high signal-to-noise ratio electrical signal under external mechanical stimulation. Within the low-frequency operating range of 0.5 Hz to 2.5 Hz, the sensor consistently maintains an open-circuit voltage peak exceeding 40 V and a stable short-circuit current output. Figure 20 , 21 As shown, its electrical output performance and flexibility are superior to sensors that rely on traditional stretchable materials such as Ecoflex. Figure 17 The results demonstrate that it possesses sufficient sensitivity as a sensor; as shown... Figure 18 The diagram illustrates that, as a self-powered sensor, it has sufficient output power; as shown... Figure 19The diagram illustrates that it can operate stably for a long time as a self-powered sensor.

[0079] like Figure 5 The PTFE oriented fiber membrane shown in Embodiment 1 of the present invention achieves basic stretchability through a microfiber-porous structure, while the strong adhesion of the functional polymer electrode layer firmly binds the upper and lower PTFE layers into a whole. This design ensures uniform stress distribution in the composite structure, and the elastic restoring force of the polymer layer effectively drives the synergistic deformation and rebound of the PTFE metamaterial, significantly improving the material's fatigue resistance. Thanks to this integrated configuration, when the sensor undergoes multiple cyclic stretching within the strain range of 0-100%, its stress-strain curves exhibit high overlap and stability, proving that the metamaterial-based structural design simultaneously solves the problems of non-stretchability and non-reboundability, thereby achieving flexible sensing functionality.

[0080] like Figure 6 The sensor prepared in Example 1 of this invention exhibits high strain tolerance and signal stability. Within a tensile strain range of 0% to 100%, the sensor's output voltage remains consistently high with minimal fluctuations. Even under 100% ultimate tensile stress, its voltage signal strength remains essentially unchanged from the initial state, with no significant attenuation observed. After complete strain release (Recover state), the sensor's output voltage rapidly recovers to its initial level, fully demonstrating its excellent elastic recovery capability and signal repeatability.

[0081] like Figure 7 The sensor prepared according to Embodiment 1 of the present invention exhibits long-term mechanical durability and signal stability. After undergoing up to 600 severe tensile cycles with 80% strain, its output voltage waveform (blue curve) completely coincides with the initial state (green curve), the peak voltage is stable at about 60V, and the waveform period and amplitude do not decrease or become distorted.

[0082] like Figure 8 , 9 The sensor device prepared in Embodiment 1 of the present invention generates electrical energy that, after rectification, can successfully charge capacitors of different capacitance values, ranging from 22μF to 1000μF, and is used to drive commercial low-power devices such as electronic timers, demonstrating its practical power supply capability as a micro-energy source.

[0083] like Figure 10 The sensor prepared in Embodiment 1 of this invention demonstrates excellent motion angle recognition capability and signal linearity in human elbow joint motion monitoring. For example... Figure 10 The data shows that when the elbow joint is bent at 30°, 60° and 90° respectively, the voltage signal generated by the sensor exhibits a clear, stable and repeatable stepped response.

[0084] like Figure 15 The figure shows the charge collection efficiency of PTFE layers of different thicknesses prepared according to the present invention. Figure 15 Data shows that there is an optimal PTFE thickness (approximately 0.3 mm), at which both voltage and current outputs reach their peak values. This demonstrates the balance between "charge storage capacity" and "device flexibility".

[0085] like Figure 16 The figure shows the charge collection efficiency of functional polymer layers of different thicknesses prepared in this invention. For example... Figure 16 Data shows that when the functional polymer layer thickness is 1.0 mm, the device achieves the highest and most stable voltage output (peak value > 40V). If it is too thin (0.5 mm), the conductive network is incomplete and the signal is weak; if it is too thick (1.5 mm), it may weaken the induced electric field and is not conducive to flexible bonding.

[0086] Comparative Example 1: The difference between this comparative example and Example 1 is as follows: In step three, accurately weigh each component according to the following mass ratio: SBMA (20%), PEGDA (0.1%), glycerol (78.8%) and PEDOT:PSS solution (1% of the total), and add photoinitiator (0.1%).

[0087] Comparative Example 2: The difference between this comparative example and Example 1 is as follows: In step three, accurately weigh each component according to the following mass ratio: SBMA (95%), PEGDA (3%), glycerol (10%) and PEDOT:PSS solution (1% of the total), and add photoinitiator (0.1%).

[0088] The sensors prepared in Comparative Examples 1 and 2 exhibited poor performance because: insufficient SBMA resulted in a weak network and poor conductivity, while excessive SBMA made the material brittle; insufficient PEGDA led to a loose structure, while excessive PEGDA caused hardening; insufficient glycerol resulted in easy water loss, while excessive glycerol resulted in poor conductivity; insufficient PEDOT:PSS resulted in low conductivity, while excessive PEDOT:PSS caused brittleness. The formulation in Example 1 (70% SBMA / 1% PEGDA / 50% glycerol) achieved excellent stretchability, adhesion, and stable conductivity through a synergistic effect.

[0089] Comparative Example 3: The difference between this comparative example and Example 1 is as follows: In step two, the cut PTFE film (2cm×2cm) is placed in the plasma cleaner reaction chamber, oxygen is introduced as the treatment gas, and the process is carried out at a power of 50W for 30 seconds.

[0090] The PTFE and functional polymer electrode layers of the sensor prepared in this comparative example have poor adhesion, which is not conducive to the formation of an integrated structure. During the deformation process, delamination may occur, leading to a decrease in output or even device failure.

[0091] Comparative Example 4: The difference between this comparative example and Example 1 is as follows: In step one, the stretching is performed in a single direction at a rate of 250% / min, with the total stretching ratio controlled at 20:1.

[0092] Excessive uniaxial stretching rate and total stretching ratio result in an excessively thin PTFE layer, making it difficult to form a stable microporous fiber network.

[0093] Comparative Example 5: The difference between this comparative example and Example 1 is as follows: The sensor prepared in this comparative example consists of, from bottom to top: a PTFE layer, an intermediate functional polymer electrode layer, and another PTFE layer; the thickness of the PTFE layer is 0.15 mm, and the thickness of the intermediate functional polymer electrode layer is 0.8 mm.

[0094] Comparative Example 6: The difference between this comparative example and Example 1 is as follows: The sensor prepared in this comparative example consists of, from bottom to top: a PTFE layer, an intermediate functional polymer electrode layer, and another PTFE layer; the thickness of the PTFE layer is 0.1 mm, and the thickness of the intermediate functional polymer electrode layer is 0.5 mm.

[0095] Comparative Example 7: The difference between this comparative example and Example 1 is as follows: The sensor prepared in this comparative example consists of, from bottom to top: a PTFE layer, an intermediate functional polymer electrode layer, and another PTFE layer; the thickness of the PTFE layer is 0.5 mm, and the thickness of the intermediate functional polymer electrode layer is 1.5 mm.

[0096] like Figure 15 , 16 As shown, both excessively thin and excessively thick PTFE layers and intermediate functional polymer electrode layers will affect the sensor's output.

[0097] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A self-powered sensor, characterized in that, It has a multilayer structure, consisting of, from bottom to top: a first PTFE layer, an intermediate functional polymer electrode layer, and a second PTFE layer. The first and second PTFE layers are obtained by plasma treatment of PTFE films. The intermediate functional polymer electrode layer is composed of SBMA, PEGDA, glycerol, PEDOT:PSS, and a photoinitiator. The thickness ratio of the first PTFE layer, the intermediate functional polymer electrode layer, and the second PTFE layer is (0.2-0.4):(0.9-1.0):(0.2-0.4).

2. The self-powered sensor according to claim 1, characterized in that, The plasma treatment is performed in a plasma cleaner by introducing oxygen or air and treating for 1-3 minutes at a power of 100-300 W; the mass ratio of SBMA, PEGDA, glycerol, PEDOT:PSS and photoinitiator is 0.3-0.9:0.005-0.02:0.3-0.7:1:0.001-0.

01.

3. A method for fabricating a self-powered sensor based on a mechanical metamaterial structure design, characterized in that, Includes the following steps: (1) Preparation of PTFE mechanical metamaterials: After cleaning the PTFE raw material, it is subjected to uniaxial stretching under heating. Heat treatment; to obtain a PTFE film; (2) PTFE film surface pretreatment: The PTFE film obtained in step (1) is cleaned and dried; then subjected to plasma treatment. (3) Preparation of intermediate functional polymer electrode layer precursor solution: Weigh out SBMA, PEGDA, glycerol, and PEDOT:PSS solution, add photoinitiator, stir, and obtain precursor solution; (4) Assembly of integrated devices and in-situ molding of functional layers: Fix the PTFE film obtained in step (2), then coat the precursor liquid obtained in step (3) onto the surface of the PTFE film; then cover it with another layer of PTFE film; apply pressure; irradiate with ultraviolet light; and you will get the product.

4. The preparation method according to claim 3, characterized in that, In step (1), the heating temperature is set to 250℃-300℃; the uniaxial stretching rate is 10% / min-200% / min; the total stretching ratio is 3-10:1; and the heat treatment method is to treat at 200℃-250℃ for 5-30 min.

5. The preparation method according to claim 3, characterized in that, In step (2), the cleaning method is ultrasonic cleaning with anhydrous ethanol; the drying method is drying with nitrogen gas.

6. The preparation method according to claim 3, characterized in that, In step (2), the plasma treatment method is to introduce oxygen or air into a plasma cleaner and treat it for 1-3 minutes at a power of 100-300 W.

7. The preparation method according to claim 3, characterized in that, In step (3), the mass ratio of SBMA, PEGDA, glycerol, PEDOT:PSS and photoinitiator is 0.3-0.9:0.005-0.02:0.3-0.7:1:0.001-0.01; the mass fraction of PEDOT:PSS in the PEDOT:PSS solution is 1%.

8. The preparation method according to claim 3, characterized in that, In step (3), the stirring method is to stir at room temperature at a speed of 500-1000 rpm / min for 5-10 min in the dark.

9. The preparation method according to claim 3, characterized in that, In step (4), the pressure application method is to apply 0.01-0.05 MPa pressure to remove bubbles; the ultraviolet treatment method is to irradiate with 365 nm ultraviolet light at an intensity of 50-100 mW / cm² for 3-5 minutes.

10. The self-powered sensor prepared by the preparation method according to any one of claims 3-9 is used in wearable devices, energy harvesting and self-powered sensing.

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