Flexible self-powered triboelectric sensor and application thereof

Abstract

The invention discloses a flexible self-powered triboelectric sensor, and belongs to the technical field of sensors, the flexible self-powered triboelectric sensor comprises a first silicone rubber layer, a hydrogel layer, a conductive silica gel electrode layer and a second silicone rubber layer which are sequentially arranged from top to bottom, the hydrogel layer is prepared from N-isopropylacrylamide (NIPAM), N, N-dimethylacrylamide (DMAA), N, N-dimethylacrylamide (DMAA), N, N-dimethylacrylamide (DMAA) and N, N-dimethylacrylamide (DMAA); n, N '-methylene bisacrylamide (MBA) and sodium alginate (SA) are copolymerized to form a three-dimensional network, in-situ embedding of biological source orange juice carbon dots is initiated through ultraviolet light, and the first silicone rubber layer, the hydrogel layer, the conductive silica gel electrode layer and the second silicone rubber layer are bonded and fixed on the periphery through silica gel. The invention discloses a green, safe and high-performance flexible triboelectric sensor, which realizes excellent electrical output through a simple process and is combined with an advanced signal processing technology to realize accurate recognition of multiple key physiological signals by a single sensor.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a flexible self-powered triboelectric sensor and its applications. Background Technology

[0002] With the rapid development of flexible electronics and wearable health monitoring technology, flexible sensors capable of real-time, non-invasive, and continuous acquisition of human physiological signals (such as pulse, respiration, and heart rate) have become a research hotspot. Traditional physiological signal monitoring devices mostly rely on rigid electrodes, wired connections, and external power supplies, which have problems such as discomfort when worn, significant motion interference, and limited application scenarios, making it difficult to meet the needs of daily long-term monitoring.

[0003] In recent years, triboelectric nanogenerators (TENGs) have been widely used in flexible self-powered sensors due to their advantages such as simple structure, low cost, no need for external power supply, and ability to convert weak mechanical energy into electrical signals. Hydrogels, as three-dimensional polymer network materials rich in water, soft, skin-friendly, and with excellent biocompatibility, are naturally suitable as dielectric or triboelectric layers for TENGs. However, traditional pure polymer hydrogels generally suffer from low surface charge density, weak charge retention capacity, and weak output signals, limiting their application in highly sensitive physiological signal detection.

[0004] To improve the performance of hydrogels, researchers have attempted to introduce nanofillers to enhance their conductivity or surface polarity. However, these fillers suffer from high cost, questionable biosafety, and poor dispersibility. While fluorescent carbon dots (CDs) possess excellent properties, their application in triboelectric sensing is still in its early stages, lacking systematic research on green sources, structure-performance relationships, and microscopic morphology regulation mechanisms. Furthermore, existing wearable sensors require multiple sensing units or complex circuits to monitor different physiological signals, making it difficult to achieve simultaneous sensing and effective decoupling of multimodal signals from a single device.

[0005] Therefore, there is an urgent need to develop a green, safe, and high-performance flexible triboelectric sensing material that can achieve excellent electrical output through simple processes and can be combined with advanced signal processing technology to enable a single sensor to accurately identify multiple key physiological signals, thereby promoting the development of wearable health monitoring devices towards lightweight, intelligent, and practical applications. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the technical problem to be solved by the present invention is to propose a green, safe, high-performance flexible self-powered triboelectric sensor.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a flexible self-powered triboelectric sensor, comprising, from top to bottom, a first silicone rubber layer, a hydrogel layer, a conductive silicone electrode layer, and a second silicone rubber layer. The first silicone rubber layer has a cavity structure, and the surface of the second silicone rubber layer is provided with papillary microstructures. The hydrogel layer is an ultraviolet light-crosslinked hydrogel doped with orange juice carbon dots. The hydrogel layer is a three-dimensional network formed by copolymerization of N-isopropylacrylamide (NIPAM), N,N-dimethylacrylamide (DMAA), N,N'-methylenebisacrylamide (MBA), and sodium alginate (SA), and the bio-derived orange juice carbon dots are in situ embedded by ultraviolet light. The first silicone rubber layer, the hydrogel layer, the conductive silicone electrode layer, and the second silicone rubber layer are bonded and fixed together around the perimeter by silicone adhesive, which is Giant Sword 988A silicone adhesive.

[0009] A preferred embodiment of the present invention is that the first silicone rubber layer and the second silicone rubber layer are made of Ecoflex 00-30 silicone rubber. During preparation, the silicone rubber A component and B component are mixed in a weight ratio of 1:1 and then cast into shape. The size of the first silicone rubber layer is 26mm × 16mm × 2mm, and the size of the second silicone rubber layer is 26mm × 16mm × 1mm.

[0010] A preferred embodiment of the present invention is that the conductive silicone electrode is a JX-3350 with a size of 20mm × 10mm, and a wire for signal transmission is connected to the conductive silicone electrode.

[0011] A method for fabricating a flexible self-powered triboelectric sensor includes the following steps:

[0012] Step 1, Preparation of orange juice fluorescent carbon dot solution: Take 20 mL of fresh orange juice, add 10 mL of ethanol and 0.05 g of urea, disperse evenly by ultrasonication, transfer to a hydrothermal reactor lined with polytetrafluoroethylene, place in an oven, and react at 190 °C for 6 h to obtain a transparent brown solution. Purify by dialysis to obtain orange juice carbon dot solution.

[0013] Step 2, preparation of hydrogels doped with fluorescent carbon dots: N-isopropylacrylamide (NIPAM), N,N-dimethylacrylamide (DMAA), and N,N'-methylenebisacrylamide (MBA) were added to a beaker and dissolved by sonication with deionized water. Sodium alginate (SA) was then added, and the mixture was continuously stirred with a magnetic stirrer to form a homogeneous solution. The solution was divided into five equal portions, and different amounts of orange juice fluorescent carbon dot solution were added to each portion. A photoinitiator was then added, and the mixture was quickly stirred with a glass rod until homogeneous. The mixture was then irradiated under a UV lamp at a distance of 20 cm for 5 min to obtain a UV-crosslinked hydrogel.

[0014] Step 3, Silicone rubber component preparation: Mold A and mold B are printed using a 3D printer and polylactic acid (PLA, Esun) respectively. The thickness of the mold shell is 2mm. The mixed Ecoflex 00-30 silicone rubber is poured into the mold. After standing at room temperature for 1 hour, the mold is demolded to obtain a first silicone rubber layer with a cavity structure and a second silicone rubber layer with a papillary structure.

[0015] Step 4, sensor assembly: Silicone rubber with a cavity structure, hydrogel layer, conductive silicone electrode, and silicone rubber with a papillary structure are stacked from top to bottom, coated with silicone adhesive around the edges for bonding, and cooled and cured for 6 hours to obtain a flexible self-powered triboelectric sensor.

[0016] A preferred embodiment of the present invention is that, in step one, the amount of orange juice carbon dots added is 15. In step two, the corresponding hydrogel preparation system contains 1.6975 g of N-isopropylacrylamide, 1.487 g of N,N-dimethylacrylamide, 0.046 g of N,N-methylbisacrylamide, 0.60 g of sodium alginate, and 30 mL of deionized water.

[0017] A preferred embodiment of the present invention is that, in step two, the photoinitiator is a solution formed by dissolving 200 mg of 2,2-dimethoxy-phenylacetophenone in 1 mL of N-vinylpyrrolidone, and the amount of solution added is 30 mg / mL. .

[0018] An application of a flexible, self-powered triboelectric sensor is disclosed. The sensor is attached to the human wrist, and the high signal-to-noise ratio triboelectric current signal output by the sensor in real time can simultaneously monitor physiological signals such as pulse (1-2Hz) and respiration (0.2-0.4Hz). The triboelectric current signal output by the sensor is converted to the frequency domain for processing using a Fast Fourier Transform (FFT) algorithm, and independent pulse and respiration signals can be separated from the single signal.

[0019] A preferred embodiment of the present invention is that the sensor has a minimum monitoring pressure of 57.5 Pa, which can cover the range of pulse pressure variation at the wrist (5.33-20 kPa) and the range of blood vessel wall impact force fluctuation caused by respiration (7.5-15 kPa).

[0020] The preferred technical solution of the present invention is that the sensor is applied in the fields of intelligent health monitoring, telemedicine or flexible wearable electronic devices, and is suitable for real-time monitoring of the pulse and respiratory physiological signals of athletes during exercise. The wearing process of the sensor does not interfere with the athletes' competitive activities.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention uses bio-derived orange juice carbon dots as fillers, which are green, sustainable, and biocompatible. This solves the problems of high cost and questionable biosafety of traditional nanofillers. Furthermore, the graphite-like sp² carbon core structure and abundant oxygen-containing functional groups of the carbon dots can significantly enhance the surface polarity and charge trapping ability of the hydrogel.

[0023] The carbon dots of this invention can regulate the formation of a loose network structure with high porosity and high flexibility in hydrogels. Combined with the hydrophobic design of the sensor's papillae, this improves the sensor's wearing comfort and environmental adaptability, and avoids interference from sweat.

[0024] The sensor of this invention has a simple structure, simple manufacturing process, and low cost. It can achieve self-powered operation without external power supply. It can simultaneously monitor pulse and respiratory signals when attached to the wrist, solving the problems of traditional devices requiring multiple sensing units and being uncomfortable to wear.

[0025] The sensor of this invention has a high signal-to-noise ratio output signal, and when combined with the FFT algorithm, it can effectively separate two physiological signals, resulting in high detection accuracy. It is suitable for various scenarios such as intelligent health monitoring, telemedicine, and athlete physiological monitoring, and has broad application prospects. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the fabrication process of the sensor.

[0027] Figure 2 The images show the XRD patterns of the hydrogel materials (top image shows hydrogel without carbon dots; bottom image shows hydrogel with carbon dots).

[0028] Figure 3 The infrared spectra of the hydrogel materials are shown below (top image: hydrogel without carbon dots; bottom image: hydrogel with carbon dots).

[0029] Figure 4 The images show the Raman spectra of hydrogel materials (top image: hydrogel without carbon dots; bottom image: hydrogel with carbon dots).

[0030] Figure 5 SEM images of hydrogel materials (top image: hydrogel without carbon dots; bottom image: hydrogel with carbon dots).

[0031] Figure 6 Response current diagrams of sensors prepared by adding hydrogels with different carbon dot contents under the same external force;

[0032] Figure 7 A graph of electrical signals monitored at the wrist by a sensor prepared with hydrogels of optimal carbon dot content;

[0033] Figure 8 The image shows the respiratory and pulse signals after FFT filtering.

[0034] The attached diagram lists the components represented by each number as follows: Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1

[0037] See attached document Figure 1 A method for fabricating a flexible self-powered triboelectric sensor includes the following steps:

[0038] Step 1, Preparation of orange juice fluorescent carbon dot solution: Take 20 mL of fresh orange juice, 10 mL of ethanol and 0.05 g of urea, put them into a beaker and ultrasonically disperse them evenly. Then transfer them to a hydrothermal reactor with a polytetrafluoroethylene liner, put them in an oven and react at 190 °C for 6 h to obtain a transparent brown solution. Use dialysis to purify the solution to obtain orange juice fluorescent carbon dot solution.

[0039] Step 2, Preparation of hydrogels doped with fluorescent carbon dots: Weigh 1.6975g of N-isopropylacrylamide (NIPAM), 1.487g of N,N-dimethylacrylamide (DMAA), and 0.046g of N,N'-methylenebisacrylamide (MBA) into a 50mL beaker. Add 30mL of deionized water and sonicate to dissolve. Then add 0.60g of sodium alginate (SA) to the beaker and stir continuously with a magnetic stirrer until a homogeneous solution is formed. Divide the solution into 5 equal portions and place them into rectangular molds. Add 0.60g of sodium alginate to each of the 5 portions in turn. 5 10 15 20 The orange juice fluorescent carbon dot solution was then added to each solution with 30... A photoinitiator prepared by dissolving 200 mg of 2,2-dimethoxy-phenylacetophenone in 1 mL of N-vinylpyrrolidone was rapidly stirred with a glass rod and then irradiated under a UV lamp at 20 cm for 5 min to obtain 5 groups of UV-crosslinked hydrogels with different fluorescent carbon dopants.

[0040] Step 3, Silicone Rubber Part Fabrication: Mold A and Mold B were designed using 3D modeling software. Both mold shells were 2mm thick. Mold A measures 30mm × 20mm × 4mm, with an internal cuboid dimension of 16mm × 6mm × 1mm. The contact surface features a hydrophobic papillary microstructure. Mold B measures 30mm × 20mm × 4mm, with an internal microstructure consisting of unevenly distributed hemispherical papillae with a radius of 0.1mm. Mold A and Mold B were printed using 3D printers (P1S, Bambu) and polylactic acid (PLA, Esun), respectively. Ecoflex 00-30 silicone rubber was mixed evenly at a weight ratio of 1A:1B and poured into molds A and B until flush with the top surface. The mixtures were allowed to stand at room temperature for 1 hour before demolding to obtain silicone rubber with a cavity structure and silicone rubber with a papillary structure.

[0041] Step 4, sensor assembly: Using conductive silicone rubber as the electrode material, cut it into rectangles of 20mm×10mm and fix them to the wires; align and stack the silicone rubber with cavity structure, the hydrogel prepared in step 2, the conductive silicone electrode, and the silicone rubber with papillary structure from top to bottom, coat each layer with silicone glue, and cool and cure at room temperature for 6 hours to obtain a flexible self-powered triboelectric sensor.

[0042] By using orange juice carbon dots as functional fillers, the problems of high cost and questionable biosafety of traditional nanofillers are avoided, meeting the needs of safety, green and sustainable development. Through the combination of mold design and 3D printing, the size and papillary morphology of silicone rubber components are precisely controlled. The papillary structure mimics the hydrophobic properties of lotus leaves, structurally solving the problem of sweat penetration and corrosion during athletes' exercise. Each component is assembled by curing silicone glue at room temperature for 6 hours. The process is simple and does not require complex equipment. Moreover, the high degree of matching of each layer structure lays the structural foundation for the flexibility and stability of the sensor, while reducing the threshold for large-scale production.

[0043] Example 2

[0044] See attached document Figure 2-5 Sensor performance characterization includes:

[0045] (1) XRD characterization: X-ray diffraction was used to test the hydrogel samples with and without carbon dots. The test range was [missing information]. See attached Figure 2 The XRD patterns showed that both samples were... The presence of broad and diffuse diffraction peaks is typical of amorphous polymer networks, indicating that the hydrogel matrix is ​​composed of randomly cross-linked poly(NIPAM-co-DMAA) chains and lacks a long-range ordered crystal structure; while the carbon-doped sample shows... A distinct sharp diffraction peak appeared at the position corresponding to the graphitic carbon (002) crystal plane, indicating that the orange juice carbon dots have a graphitized sp² carbon core structure. At the same time, weak diffraction signals were observed at the positions of 18°, 34°, and 43°, further confirming the existence of microcrystalline regions inside the carbon dots. The above characteristic peaks were not detected in the hydrogel sample without carbon dots. Based on the above results, it is clear that the orange juice carbon dots have been successfully embedded in the hydrogel network and have maintained their inherent crystallization characteristics during the crosslinking process without destroying the amorphous structure of the polymer matrix.

[0046] (2) FTIR characterization: The two hydrogel samples were tested using a Fourier transform infrared spectroscopy (FTIR) instrument. The test range was [missing information]. See attached Figure 3 The FTIR spectra of the two groups of samples showed a high degree of similarity, indicating that the introduction of carbon dots did not cause significant changes in the chemical structure of the polymer backbone. The broad and strong absorption peaks are attributed to the N–H and O–H stretching vibrations; and The absorption peaks at these locations correspond to the amide I band (C=O stretching) and the amide I band (N–H bending), respectively, confirming the successful construction of the poly(NIPAM-co-DMAA) network. The presence of C–H stretching vibrations further confirms the existence of the organic framework; after doping with carbon dots, The absorption peak at this point is significantly broadened. The enhanced absorption intensity indicates hydrogen bonding interactions between the oxygen-containing functional groups (such as –OH, –COOH) on the surface of the orange juice carbon dots and the polymer chains. Furthermore, the absence of new characteristic absorption peaks suggests that the carbon dots primarily exist physically embedded in the hydrogel matrix, without covalent grafting or chemical reactions. These results are consistent with XRD and Raman characterization, jointly confirming the successful introduction of carbon dots and their non-covalent interfacial interaction with the matrix.

[0047] (3) Raman characterization: The sample was tested using a Raman spectrometer, with a testing range of [missing information]. See attached Figure 4 The Raman spectra of the undoped carbon dots showed that the sample exhibited only a weak and broad background signal, with no obvious characteristic vibrational peaks, consistent with the typical Raman response of amorphous acrylamide polymers; in contrast, the carbon-doped sample showed a Raman response of approximately [missing information - likely a specific value]. A significant sharp peak appears at approximately [location missing], attributed to the G band (E2g mode) of the graphitized carbon structure, indicating that the orange juice carbon dots contain sp² hybridized conjugated carbon domains; simultaneously, at approximately [location missing]... A weak D-band can be observed, corresponding to defects or edge disorder in the carbon structure; the simultaneous presence of G and D bands indicates that the prepared carbon dots possess both a certain degree of ordered graphite core and surface / edge defects, consistent with its bio-derived synthetic pathway. Furthermore, C–H stretching vibrations in the region and The broad peaks in the vicinity were present in both groups of samples, further confirming that the hydrogel matrix structure was not chemically damaged by the introduction of carbon dots.

[0048] (4) SEM characterization: The microstructure of the two hydrogels was observed using scanning electron microscopy, as shown in Appendix. Figure 5 The SEM images show that the hydrogel without carbon dots (top image) exhibits a dense, low-porosity continuous network structure; the hydrogel doped with orange juice carbon dots (bottom image) transforms into a highly loose, porous three-dimensional framework with increased pore size and interconnected pores. This indicates that the carbon dots do not simply fill the pores, but rather promote phase separation or inhibit excessive local cross-linking during UV photopolymerization through their hydrophilic surface and interfacial effects, thereby constructing a more open network structure. This porous morphology is beneficial for improving the swelling properties, mass transport efficiency, and fluorescence response sensitivity of the hydrogel, revealing the significant regulatory role of carbon dots on the microstructure of the hydrogel.

[0049] Four targeted characterization methods—XRD, FTIR, Raman spectroscopy, and SEM—comprehensively verified the scientific validity and effectiveness of the material design. The successful embedding and structural preservation of the orange juice carbon dots were confirmed. The graphite characteristic peaks of XRD and the G / D band signals of Raman spectroscopy jointly corroborated the integrity of the carbon dot-like graphite sp² carbon core structure, providing a structural basis for improving the sensor's charge trapping capability. FTIR characterization revealed the non-covalent interaction between the carbon dots and the hydrogel matrix, demonstrating that the introduction of carbon dots did not disrupt the polymer backbone structure, ensuring the hydrogel's flexibility and biocompatibility. SEM characterization visually demonstrated the regulatory effect of carbon dots on the hydrogel's microstructure; the formation of a porous and loose structure improved the material's swelling performance and mass transport efficiency, providing microstructural support for subsequent high-sensitivity sensing.

[0050] Example 3

[0051] See attached document Figure 6 The triboelectric sensing performance of the sensor prepared in Example 1 was tested.

[0052] Appendix Figure 6 The text shows different amounts of carbon dots added to orange juice (0...). 5 10 15 20 The real-time output current response of the hydrogel triboelectric sensor was studied. The results showed that as the carbon dot content increased, the peak current of the sensor exhibited a trend of first increasing and then decreasing: at 15... It reaches a maximum value of approximately ±75nA at 20, while at 20 The voltage drop was significantly reduced to ±25 nA. This phenomenon indicates that carbon dots play a dual role in the triboelectric process: on the one hand, their abundant oxygen-containing functional groups enhance the polarity of the material surface, promoting charge separation during contact electrification; on the other hand, their sp² carbon structure helps to construct local electron transport channels, improving charge collection efficiency. However, when the carbon dot concentration is too high, local aggregation or network structure destruction may occur, leading to intensified charge recombination or unstable interfacial contact, thereby weakening the output signal. Therefore, 15 The optimal dosage of carbon dots achieves an optimal balance between charge generation and transport, and this formulation of hydrogel is used as an electrode material in pulse and respiration monitoring.

[0053] Through variable-control experiments (gradient carbon dot addition), the core performance of the sensor was precisely optimized. When the carbon dot addition in orange juice was 15... At this point, the sensor's peak current reached ±75nA, significantly improving the signal strength compared to the sensor without carbon dots. This solved the key problems of low surface charge density and weak output signal in traditional hydrogel-based sensors. It also revealed the dual mechanism of carbon dots—enhancing surface polarity to promote charge separation and constructing electron transport channels to improve collection efficiency. Furthermore, it explained the effect of high-dose carbon dots (20... The causes of signal attenuation (local aggregation, network destruction) provide a theoretical basis for subsequent material performance regulation; at the same time, standardized testing under the same external force ensures the comparability and reliability of the data, and the determined optimal ratio provides a core guarantee for the high signal-to-noise ratio output of subsequent physiological signal monitoring.

[0054] Example 4

[0055] See attached document Figure 7-8 The sensor is used for pulse and respiratory signal monitoring.

[0056] The fluctuation of the pulse is caused by the periodic changes in arterial pressure due to the pumping action of the heart. When the heart is in diastole, the blood vessels at the wrist constrict, with a pressure of 5.33-6.67 kPa (i.e., 40-50 mmHg). When the heart is in systole, the blood vessels at the wrist dilate, with a pulse pressure of 13.33-20 kPa (i.e., 100-150 mmHg). Obviously, the minimum monitoring range of the sensor (UHT Sensor) in this application can completely cover the pulse pressure at the wrist during the heart's systole and diastole.

[0057] Respiration consists of two processes: inhalation and exhalation. During inhalation, arteries constrict, blood vessels narrow, and blood flow velocity increases. This change in blood flow velocity alters the impact and shear forces exerted by the blood on the vessel walls, leading to vibration and deformation of the vessel walls. According to fluid mechanics formulas: F= ;

[0058] in; Let v be the blood density, v be the blood flow velocity, and A be the cross-sectional area of ​​the blood vessel.

[0059] The impact force peaks at the beginning of inhalation and then gradually weakens due to adjustments in blood flow distribution. In a healthy adult respiratory cycle, the fluctuation range of the impact force on the blood vessel wall at the wrist is approximately 10-15 kPa, and during exhalation, it is approximately 7.5-10 kPa. The sensor in this application has a minimum monitored pressure of 57.5 Pa, therefore it can also detect the minute mechanical movements caused by these hemodynamic changes. Combining the above two parameter acquisition methods, the UHT Sensor is worn on the wrist to measure... Figure 7 The curves show that the large, low-frequency waveforms represent continuous respiratory signals, while the continuous waveforms with low amplitude and high frequency distributed across the large waveforms represent pulse signals.

[0060] By using FFT filtering, complex physiological signals can be converted to the frequency domain for processing. Then, the frequency components of the pulse and respiration signals are analyzed separately, ultimately separating the individual pulse and respiration signal images. Figure 8 As shown. Therefore, by wearing a UHT sensor on the wrist, it is possible to simultaneously measure pulse and respiration signals. It can output triboelectric current signals in real time without external power supply. Combined with the Fast Fourier Transform (FFT) algorithm, it can effectively separate and simultaneously identify the two physiological rhythms of pulse (1–2 Hz) and respiration (0.2–0.4 Hz) from a single sensor signal. This provides substantial convenience for monitoring athletes' physiological parameters during exercise, and the wearing process does not interfere with the athlete's competitive activities.

[0061] This device achieves simultaneous acquisition of multiple signals from a single device. The sensor can capture pulse and respiration signals simultaneously simply by attaching it to the wrist, eliminating the need for multiple sensing units on the wrist, waist, or other areas. This meets the needs of athletes for lightweight and interference-free wear during exercise. Combined with the FFT algorithm, it successfully achieves precise separation of the two signals, producing clear waveforms and solving the technical challenge of distinguishing between coupled multimodal signals. The sensor's minimum monitoring pressure of 57.5 Pa completely covers the pressure fluctuation range of pulse (5.33-20 kPa) and respiration (7.5-15 kPa), providing sufficient accuracy for physiological monitoring. Furthermore, it requires no external power supply, enabling self-powered real-time monitoring. It is suitable for various scenarios such as intelligent health monitoring and telemedicine, and is particularly well-suited for continuous monitoring of physiological signals during high-intensity exercise.

[0062] This invention has been described through preferred embodiments. Those skilled in the art will understand that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. This invention is not limited to the specific embodiments disclosed herein; other embodiments falling within the scope of the claims are also within the protection scope of this invention.

Claims

1. A flexible self-powered triboelectric sensor, characterized by: The application relates to a flexible self-powered triboelectric sensor, which comprises, from top to bottom, a first silicone rubber layer, a hydrogel layer, a conductive silicone electrode layer and a second silicone rubber layer, wherein the first silicone rubber layer has a cavity structure, the surface of the second silicone rubber layer is provided with a papillary microstructure, the hydrogel layer is orange juice carbon dot-doped ultraviolet light cross-linked hydrogel, the hydrogel layer is formed into a three-dimensional network by copolymerization of N-isopropyl acrylamide (NIPAM), N, N-dimethyl acrylamide (DMAA), N, N'-methylene bisacrylamide (MBA) and sodium alginate (SA), and biological source orange juice carbon dots are in-situ embedded by ultraviolet light initiation, the first silicone rubber layer, the hydrogel layer, the conductive silicone electrode layer and the second silicone rubber layer are fixed by silicone glue on the periphery, and the silicone glue is giant sword 988A silicone glue.

2. The flexible self-powered triboelectric sensor according to claim 1, wherein: The first and second silicone rubber layers are prepared from Ecoflex 00-30 silicone rubber, and the A component and the B component of the silicone rubber are mixed according to a weight ratio of 1:1 and then cast into shape, the first silicone rubber layer has a size of 26mm*16mm*2mm, and the second silicone rubber layer has a size of 26mm*16mm*1mm.

3. The flexible self-powered triboelectric sensor according to claim 1, wherein: The conductive silicone electrode is made of JX-3350 and has a size of 20mm*10mm, and a wire for signal transmission is connected to the conductive silicone electrode.

4. A preparation method of the flexible self-powered triboelectric sensor according to any one of claims 1-3, comprising the following steps: Step one, preparation of orange juice fluorescent carbon dot solution: 20mL of fresh orange juice is taken, 10mL of ethanol and 0.05g of urea are added, the mixture is uniformly dispersed by ultrasonic and then transferred into a polytetrafluoroethylene-lined hydrothermal reactor, the reactor is placed in an oven, and the reaction is carried out at 190 DEG C for 6h to obtain a transparent brown solution, and the orange juice carbon dot solution is obtained by using a dialysis method for purification; Step two, preparation of hydrogel doped with fluorescent carbon dots: N-isopropyl acrylamide (NIPAM), N, N-dimethyl acrylamide (DMAA) and N, N'-methylene bisacrylamide (MBA) are added to a beaker, ultrasonic dissolution is carried out with deionized water, then sodium alginate (SA) is added, a magnetic stirrer is used for constant stirring to form a uniform solution, the solution is equally divided into five parts, different amounts of orange juice fluorescent carbon dot solution are added, a photoinitiator is added, and the mixture is uniformly stirred with a glass rod, and ultraviolet light is irradiated at a distance of 20cm for 5min to obtain ultraviolet light cross-linked hydrogel; Step three, preparation of a silicone rubber part: a 3D printer and polylactic acid (PLA, Esun) are used to print mold A and mold B respectively, the shell thicknesses of the molds are both 2mm, the mixed Ecoflex 00-30 silicone rubber is poured into the molds, and the molds are demolded after being left to stand at room temperature for 1h to obtain the first silicone rubber layer with a cavity structure and the second silicone rubber layer with a papillary structure. ​ Step four, sensor assembly: stack the silicone rubber with cavity structure, hydrogel layer, conductive silicone electrode and silicone rubber with papillary structure from top to bottom, coat silicone adhesive around, cool and solidify for 6 hours, to obtain flexible self-powered triboelectric sensor.

5. The preparation method of claim 4, wherein: The orange juice carbon dots are added in an amount of 15 In the second step, the N-isopropyl acrylamide in the hydrogel preparation system is 1.6975 g, the N,N-dimethyl acrylamide is 1.487 g, the N,N-methyl bisacrylamide is 0.046 g, the sodium alginate is 0.60 g, and the deionized water is 30 mL.

6. The preparation method of claim 4, wherein: In the second step, the photoinitiator is a solution of 200 mg of 2,2-dimethoxy- phenylphenacylketone in 1 mL of N-vinylpyrrolidone, the solution being added in a quantity of 30 .

7. The application of the flexible self-powered triboelectric sensor according to any one of claims 1-3, wherein: The sensor is attached to the human wrist, and the high signal-to-noise ratio triboelectric current signal output by the sensor in real time can synchronously monitor the pulse (1-2 Hz) and respiratory (0.2-0.4 Hz) physiological signals, and the fast Fourier transform (FFT) algorithm is used to convert the triboelectric current signal output by the sensor to the frequency domain for processing, and the independent pulse signal and respiratory signal can be separated from the single signal.

8. The application of claim 7, wherein: The minimum monitoring pressure of the sensor is 57.5 Pa, which can cover the pulse pressure change range of 5.33-20 kPa and the blood vessel wall impact force fluctuation range of 7.5-15 kPa caused by respiration at the wrist.

9. The application of claim 7, wherein: The sensor is applied to the fields of intelligent health monitoring, remote medical treatment or flexible wearable electronic devices, and is suitable for real-time monitoring of the pulse and respiratory physiological signals of athletes during exercise, and the wearing process of the sensor does not interfere with the athletes' competitive activities.

Images