Graphene composite material, supercapacitor preparation method, flexible sensor and application
The preparation of graphene composite materials using a femtosecond laser processing system has solved the processing accuracy and material performance problems of traditional micro supercapacitors, realizing the preparation of high-performance flexible micro supercapacitors suitable for physiological signal detection in wearable devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA UNIV OF PETROLEUM (EAST CHINA)
- Filing Date
- 2026-03-30
- Publication Date
- 2026-06-23
Smart Images
Figure CN122266967A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of new materials technology, and more specifically, to a graphene composite material, a method for preparing a supercapacitor, a flexible sensor, and its applications. Background Technology
[0002] With the rapid development of flexible electronics and wearable technology, the demand for matching miniaturized, flexible, and high-performance energy storage systems is becoming increasingly urgent. Among various energy storage devices, micro supercapacitors (MSCs) have attracted widespread attention due to their high power density, long cycle life, and fast charge-discharge characteristics. As a key component of wearable systems, flexible micro supercapacitors not only need to possess excellent electrochemical performance but also meet the requirements of good mechanical flexibility and structural miniaturization. These devices are often directly attached to or worn on the surface of human skin for real-time monitoring and acquisition of physiological signals, showing broad application prospects in fields such as remote health management, human activity tracking, and human-computer interaction.
[0003] However, with the rapid development of technology, the traditional MSCs preparation process has gradually revealed many bottlenecks, specifically in terms of limited processing precision, difficulty in optimizing material properties, and high energy consumption and environmental pressure during the manufacturing process.
[0004] Polyvinylidene fluoride (PVDF), a polymer material with good flexibility and chemical stability, is often used as a separator or polymer electrolyte matrix in flexible energy storage devices. However, most PVDF-based separators in integrated supercapacitors currently fabricated by electrospinning typically suffer from inherent defects such as poor mechanical properties (easily punctured), thus exhibiting limited durability and insecurity. Separators prepared by solution casting are often limited by poor electrolyte absorption and low ionic conductivity, resulting in poor charge-discharge rates and cycle stability. The limitations of traditional processing methods in achieving fine patterning severely restrict its direct application as an electrode material. Summary of the Invention
[0005] To address the above problems, in a first aspect, the present invention provides a method for preparing graphene composite materials, characterized by comprising: Set the processing parameters for the femtosecond laser, adjust the position of the moving mirror in the femtosecond laser processing system, and split the femtosecond laser into two laser pulses.
[0006] The femtosecond laser processing system is activated, and the femtosecond laser is used to process the fluorine-containing polar polymer flexible substrate placed in the graphene dispersion to obtain the graphene composite material. The graphene composite material includes the fluorine-containing polar polymer flexible substrate and the sheet-like LIG-nanographene particle composite functional layer.
[0007] Optionally, the fluorinated polar polymer flexible substrate includes polytetrafluoroethylene, fluorinated ethylene propylene, polychlorotrifluoroethylene, and polyvinylidene fluoride.
[0008] Optionally, the processing parameters of the femtosecond laser include laser wavelength, single pulse energy, repetition frequency, and laser power, wherein the laser wavelength is 1030 nm, the single pulse energy is 7.5 μJ, the repetition frequency is 20 kHz, and the laser power is 90 mW-100 mW.
[0009] Optionally, the dual laser pulses include a first femtosecond laser pulse and a second femtosecond laser pulse, and the delay time between the first femtosecond laser pulse and the second femtosecond laser pulse is in the range of 0ps-30ps.
[0010] Secondly, the present invention also provides a method for preparing a supercapacitor, characterized in that it includes: Obtain the interdigitated electrode pattern of the designed supercapacitor and convert the interdigitated electrode pattern into a scanning path for a femtosecond laser.
[0011] The femtosecond laser scanning in the femtosecond laser processing system is controlled according to the obtained scanning path, and a micro supercapacitor based on graphene composite material is obtained by performing the graphene composite material preparation method described above.
[0012] Thirdly, the present invention provides a flexible sensor, characterized in that it includes a miniature supercapacitor obtained by the supercapacitor fabrication method described above.
[0013] Silver paste is applied to the two electrodes of a miniature supercapacitor, and the electrodes are connected by wires to extract signals. After encapsulation, a flexible sensor is formed.
[0014] Fourthly, the present invention provides an application of a flexible sensor, characterized in that the aforementioned flexible sensor is applied to detect human physiological signals.
[0015] This invention provides a graphene composite material, a method for preparing a supercapacitor, a flexible sensor, and its applications. Compared with existing technologies, it has the following advantages: Femtosecond laser processing of a fluorine-containing polar polymer flexible substrate placed in a graphene dispersion enables in-situ growth and composite formation of graphene on the substrate surface. The prepared graphene composite material exhibits excellent structural integrity and electrochemical performance in its sheet-like LIG-nanographene particle composite functional layer. This functional layer not only provides conductivity but also possesses electrolyte absorption capacity and ion transport channels due to its porous structure, effectively improving the material's charge / discharge rate and cycle stability. This addresses the problems of poor mechanical properties, susceptibility to puncture, and low electrolyte absorption capacity and ionic conductivity inherent in traditional PVDF-based membranes. The application of dual laser pulses provides a flexible control method for graphene structure formation, helping to optimize the morphology and crystallinity of graphene and further enhancing the overall performance of the composite material. This application not only provides a highly efficient and precise method for preparing graphene composite materials but also lays an important foundation for the development of flexible electronic devices, especially high-performance flexible micro supercapacitors. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the femtosecond laser processing system provided in an embodiment of the present invention.
[0017] Figure 2 This is a schematic diagram illustrating the fabrication of a flexible supercapacitor device provided in an embodiment of the present invention.
[0018] Figure 3 A schematic diagram of the molecular structure of the PVDF thin film surface processed by femtosecond laser liquid phase processing provided in an embodiment of the present invention.
[0019] Figure 4 Raman comparison images of PVDF-LIG and PVDF-LIG / Graphene provided for embodiments of the present invention.
[0020] Figure 5 Raman spectra of samples at different powers provided in embodiments of the present invention.
[0021] Figure 6 Different bond ratios of C elements in PVDF-LIG and LIG / Graphene provided for embodiments of the present invention.
[0022] Figure 7 Raman comparison images of PVDF-LIG / Graphene at multiple delay times provided in embodiments of the present invention.
[0023] Figure 8 Analysis of the C 1s peak percentage of PVDF-LIG / Graphene under multiple delay times provided in embodiments of the present invention.
[0024] Figure 9This is a patterned fabrication diagram of interdigitated electrodes under a metallographic microscope, provided in an embodiment of the present invention.
[0025] Figure 10 The CV test graphs for PVDF-LIG, PVDF-LIG / Gold, PVDF-LIG / MXene, and PVDF-LIG / Graphene provided in the embodiments of the present invention.
[0026] Figure 11 GCD test images of various materials provided in embodiments of the present invention.
[0027] Figure 12 The above are statistical charts of the area-to-capacitance ratio of various materials provided in the embodiments of the present invention.
[0028] Figure 13 An actual image of the flexible sensor provided in an embodiment of the present invention.
[0029] Figure 14 Parallel metallographic microscope images provided for embodiments of the present invention.
[0030] Figure 15 The CV curve of parallel MSCs provided in the embodiments of the present invention.
[0031] Figure 16 GCD curves of parallel MSCs provided in an embodiment of the present invention.
[0032] Figure 17 These are tandem metallurgical microscope images provided for embodiments of the present invention.
[0033] Figure 18 The CV curve of tandem MSCs provided in an embodiment of the present invention.
[0034] Figure 19 GCD curves of tandem MSCs provided in this embodiment of the invention.
[0035] Figure 20 The CV curves of the same MSCs device under different bending states are provided for embodiments of the present invention.
[0036] Figure 21 The graph shows a 10,000-cycle long-cycle test of MSCs provided in an embodiment of the present invention.
[0037] Figure 22 The CV curve of MSCs after seven days is provided for an embodiment of the present invention.
[0038] Figure 23 The GCD image obtained after seven days is provided for an embodiment of the present invention.
[0039] Explanation of reference numerals in the attached figures: 1. Femtosecond laser; 2. Polarizer; 3. Beam splitter; 4. First mirror; 5. Second mirror; 6. Moving mirror; 7. Optical path switch; 8. Dichroic mirror; 9. Camera; 10. Objective lens; 11. Dish. Detailed Implementation
[0040] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0041] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.
[0042] like Figure 1 As shown, in the femtosecond laser processing system, the femtosecond laser 1 emits laser light, which is then split into two laser pulses by the polarizer 2 and the beam splitter 3. The first femtosecond laser pulse is reflected by the first mirror 4, and the second femtosecond laser pulse is reflected by the moving mirror 6. Then, the two laser pulses pass through the second mirror 5, the optical path switch 7, the dichroic mirror 8, and the objective lens 10 to reach the surface of the material to be processed in the vessel 11. The camera 9 is used to photograph the processing situation inside the vessel 11. The position of the moving mirror 6 changes, which can adjust the delay time between the two femtosecond laser pulses.
[0043] like Figure 2 As shown in the embodiments of this application, a method for preparing a graphene composite material includes: The processing parameters for the femtosecond laser are set, and the position of the moving mirror in the femtosecond laser processing system is adjusted to split the femtosecond laser into two laser pulses. The delay between the two laser pulses is precisely adjusted by controlling the mounting platform of the moving mirror 6. The processing parameters for the femtosecond laser include laser wavelength, single pulse energy, repetition frequency, and laser power, wherein the laser wavelength is 1030 nm, the single pulse energy is 7.5 μJ, the repetition frequency is 20 kHz, and the laser power is 90 mW-100 mW.
[0044] The femtosecond laser processing system is activated, and the femtosecond laser is used to process the fluorine-containing polar polymer flexible substrate placed in the graphene dispersion to obtain the graphene composite material. The graphene composite material includes the fluorine-containing polar polymer flexible substrate and the sheet-like LIG (Laser Induced Graphene)-nanographene particle composite functional layer.
[0045] Specifically, the fluorinated polar polymer flexible substrate includes polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), polychlorotrifluoroethylene (PCTFE), and polyvinylidene fluoride (PVDF). Figure 2 As shown, the modulated beam is focused by a 20x objective lens and applied to the surface of the PVDF film to form a micro-machining region with an energy density of 121.86 J / cm².
[0046] For example, graphene was prepared by liquid-phase processing-induced fabrication on the surface of a PVDF film using a femtosecond laser processing system (laser wavelength 1030 nm, single pulse energy 7.5 μJ, repetition frequency 20 kHz, calculated energy density 121.86 J / cm²). Figure 3 As shown, under the action of the first femtosecond laser pulse, the surface of the PVDF film experiences an ultra-high peak power density due to the femtosecond laser. A plasma pulse (10¹³ W / cm²) breaks through the ionization threshold of the material, "pre-activating" the CF bonds in the PVDF molecular chain, reducing their bond energy and inducing structural instability. Simultaneously, it forms a micron-level rough structure on the surface, increasing the effective specific surface area for subsequent reactions. Furthermore, a plasma channel heats the aqueous solvent in the graphene dispersion, generating microbubbles to provide a locally confined environment for the subsequent reactions. A second femtosecond laser pulse, through energy superposition, induces selective breaking of the CF bonds, driving the reconstruction of the PVDF molecular chain and generating abundant active bonds such as C=C, CC, and CO. During this process, some carbon and oxygen atoms are released as CO and CO₂ gases, and the remaining free carbon atoms rearrange to form graphene, ultimately forming a sheet-like graphene structure on the film surface. Simultaneously, the same energy pulse effect dissociates the graphene sheets in the dispersion into nanoparticles, and the graphene dispersion sheets into nanoscale graphene particles. Under the synergistic drive of the plasma channel electric field and the microbubble buoyancy, these particles are precisely attached to the newly formed sheet-like laser-induced graphene substrate on the PVDF surface, ultimately constructing a sheet-like LIG-nanographene particle composite functional layer.
[0047] Femtosecond laser processing of a fluorine-containing polar polymer flexible substrate placed in a graphene dispersion enables in-situ growth and composite formation of graphene on the substrate surface. Compared with PVDF-based membranes prepared by electrospinning or solution casting in existing technologies, the graphene composite material prepared by this method exhibits excellent structural integrity and electrochemical performance in its sheet-like LIG-nanographene particle composite functional layer. This functional layer not only provides conductivity but also possesses electrolyte absorption capacity and ion transport channels due to its porous structure, thereby effectively improving the charge-discharge rate and cycle stability of the material. This solves the problems of poor mechanical properties, easy puncture, low electrolyte absorption capacity, and low ionic conductivity of traditional PVDF-based membranes.
[0048] Furthermore, the application of dual laser pulses provides a flexible control method for the formation of graphene structures, which helps to optimize the morphology and crystallinity of graphene and further improve the overall performance of the composite material. Therefore, the method in this embodiment not only provides a highly efficient and precise route for preparing graphene composite materials, but also lays an important foundation for the development of flexible electronic devices, especially high-performance flexible micro supercapacitors.
[0049] In an optional embodiment of this application, the laser power is 90 mW-100 mW.
[0050] like Figure 4 As shown, Raman spectroscopy characterization was performed on pure PVDF-LIG and PVDF-LIG / Graphene composite materials. The results showed that both samples exhibited the characteristic Raman peak of graphene, namely the D peak (~1350 cm⁻¹). - ¹), G peak (~1580 cm) - ¹) and 2D peak (~2670-2700 cm⁻¹) - ¹). Among them, the Raman peak intensity of the PVDF-LIG / Graphene composite material is higher than that of I. D / I G <1, while the I of pure LIG D / I G >1 indicates that liquid-phase processing of graphene sheets can effectively reduce the lattice defect density of PVDF-LIG.
[0051] To investigate the effect of actual laser power on the structure of PVDF-LIG / Graphene composite materials, the output power was varied by controlling the laser attenuation level, and Raman spectroscopy tests were performed on samples prepared at different powers. Figure 5 The results showed that when the laser power was higher than 90 mW, obvious 2D peaks began to appear in the Raman spectrum of the sample, indicating the gradual formation of graphene characteristic structures; further analysis of I... D / I G The ratio revealed that when the laser power exceeded 110 mW, I D / I G The value is greater than 1 and increases with increasing power, indicating that excessively high power leads to an increase in PVDF-LIG lattice defects; while when the laser power is 100 mW, I D / I G Reaching the minimum value (0.96) corresponds to the lowest material defect density and the optimal degree of graphitization. Based on these results, 100 mW was selected as the optimal laser processing power for the subsequent preparation of PVDF-LIG / Graphene composite materials. Figure 6As shown, the characteristic peak intensity of sp² hybrid carbon in the PVDF-LIG / Graphene composite structure is significantly higher than that of other bonded carbon forms, with a relative content of 33.03%, far exceeding the 25.65% of sp³ hybrid carbon and the proportion of various oxygen-containing functional groups. This result indicates that a large number of ordered graphitized crystal domains are formed in the composite structure, which is consistent with the synergistic mechanism of carbonization transformation of the PVDF matrix and particle formation of graphene dispersions during laser-induced processing. Compared with single PVDF-LIG, the relative content of sp² hybrid carbon in the PVDF-LIG / Graphene composite structure is increased by 24.49%. This phenomenon further confirms that femtosecond laser liquid phase processing effectively promotes the repair of conjugated structures and the improvement of graphitization degree in carbon materials, laying a structural foundation for the optimization of the material's electrical conductivity and mechanical properties.
[0052] In an optional embodiment of this application, the dual laser pulses include a first femtosecond laser pulse and a second femtosecond laser pulse, and the delay time between the first femtosecond laser pulse and the second femtosecond laser pulse is in the range of 0ps-30ps.
[0053] The PVDF-LIG / Graphene composite material exhibited the best overall characterization performance at a laser power of 100 mW. To further investigate the influence of the key parameter "laser electron delay" in femtosecond laser double-pulse time-domain shaping on the processing effect and microstructure of the composite material, a fixed laser power of 100 mW was used. Four different electron delay times (2 ps, 10 ps, 20 ps, and 30 ps) were selected for femtosecond laser double-pulse processing experiments on PVDF films, with 0 ps (no delay) serving as the control group. To systematically evaluate the effect of different laser electron delay times on the graphene properties in the processed material, Raman spectroscopy was performed on the PVDF-LIG / Graphene composite materials prepared under the above different delay conditions (2 ps, 10 ps, 20 ps, and 30 ps). The results are as follows: Figure 7 As shown, the characteristic peak of graphene, namely the D peak (~1350 cm⁻¹), appeared in the Raman spectra of all samples. - ¹), G peak (~1580 cm) - ¹) and 2D peak (~2670-2700 cm⁻¹) - ¹), confirming that different processing delays successfully induced the formation of graphene structures. The characteristic peak intensity ratio I was calculated. D / I G We obtained I under delay conditions of 2 ps, 10 ps, 20 ps, and 30 ps. D / I G The values are 0.94, 0.93, 0.91, and 0.95 respectively. It can be seen that as the delay time increases, I... D / IG It shows a trend of first decreasing and then increasing, where I under a delay of 20 ps D / I G The minimum value (0.91) indicates that the defect density of graphene is the lowest under this condition; the peak sharpness of the 2D peak is the largest, and the relative content of graphene in the material is the highest at a delay of 20 ps.
[0054] like Figure 8 As shown, the relative proportion of the characteristic peak of sp² hybrid carbon in the composite structure exhibits a significant "first increase, then decrease" trend with the extension of laser delay time. Specifically, when the delay time is 20 ps, the relative content of sp² hybrid carbon reaches its peak (38.75%), while the proportion of sp³ hybrid carbon drops to its lowest point (20.74%). During the shorter and gradually increasing delay period, the laser energy achieves effective thermal accumulation within the PVDF-LIG / Graphene composite system. This thermal effect not only provides thermodynamic drive for the defluorination and dehydrogenation processes of the carbon precursor in the PVDF matrix, but more importantly, it creates sufficient energy conditions for the dynamic rearrangement of carbon atoms. This promotes the transformation of a large number of disordered sp³ hybrid carbon atoms in the system into sp² hybrid carbon with a conjugated six-membered ring structure, thereby significantly increasing the relative proportion of sp² hybrid carbon. However, when the delay time exceeds the critical value of 20 ps, the continuous heat accumulation triggers an excessive thermal effect: on the one hand, it causes the already formed graphene sp² conjugated structure to break, and some ordered sp² hybrid carbon is re-converted into disordered sp³ hybrid carbon or amorphous carbon; on the other hand, it causes the thermal degradation of PVDF molecular chains, and the deposition of its degradation products on the LIG surface further interferes with the ordered arrangement of carbon atoms, ultimately leading to a downward trend in the proportion of sp² hybrid carbon characteristic peaks.
[0055] The characterization results from both core dimensions clearly show that, in terms of experimental parameters and experimental system, the 20 ps laser electronic delay parameter can simultaneously achieve both high graphene content and low defect characteristics, making it the optimal process parameter that balances the comprehensive performance of the composite structure.
[0056] This application provides a method for fabricating a supercapacitor, comprising: Obtain the interdigitated electrode pattern of the designed supercapacitor and convert the interdigitated electrode pattern into a scanning path for a femtosecond laser.
[0057] The femtosecond laser scanning in the femtosecond laser processing system is controlled according to the obtained scanning path, and a micro supercapacitor based on graphene composite material is obtained by executing the above-mentioned graphene composite material preparation method.
[0058] Through precise path control and a scanning speed of 0.5 mm / s, we directly achieved micron-level precision interdigitated electrode patterning on the surface of PVDF films. Figure 9There are a total of four groups, with an interdigital width of 100μm, a length of 500μm, and an interdigital electrode spacing of 20μm.
[0059] PVDF-LIG / Graphene MSCs were immersed in 1 mol / L H2SO4 electrolyte and allowed to stand for 2 h to achieve complete electrolyte penetration. Nano-graphene particles were attached to the LIG substrate, creating an efficient electron / ion dual transport pathway. After coating the MSCs with the electrolyte, H+, ... Ions migrate in opposite directions between electrodes, effectively storing charge in the PVDF-LIG matrix. This synergistically enhances the charge-discharge capacity and performance of MSCs. To investigate the regulatory effect of different dispersions on the electrochemical performance of PVDF-LIG MSCs, PVDF films were fabricated in gold nanoparticle dispersions and Ti3C2MXene dispersions to generate MSCs. These MSCs were then further impregnated with a 1 mol / L H2SO4 electrolyte and allowed to stand for 2 h to achieve complete electrolyte penetration. Considering that excessively high voltage might induce electrolyte hydrolysis and side reactions in the electrode materials, 0.8 V was selected as the rated operating voltage for electrochemical testing to ensure the stability of the testing process and the reliability of the results. At 20 mV... s - At a scan rate of ¹, cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests were performed on MSCs modified with different dispersions. The results are as follows: Figure 10 and Figure 11 As shown in the figure, the CV curves of PVDF-LIG / Graphene modified MSCs have the largest enclosing area and the curve shape is closer to the ideal rectangle (double-layer capacitance characteristic). The corresponding GCD curves show highly symmetrical triangles, indicating that the system has excellent capacitive behavior and charge transfer reversibility.
[0060] To quantitatively evaluate the differences in electrochemical performance, the areal capacitance of each sample was calculated using GCD curves. The results are as follows: Figure 12 As shown, the areal specific capacitances of PVDF-LIG, PVDF-LIG / gold nanoparticles, PVDF-LIG / MXene, and PVDF-LIG / Graphene are 15.75 mF. cm - ²、23.00 mF cm - ², 32.25 mF cm - ², 58.25 mF cm - ², clearly the graphene dispersion-modified sample exhibits the best energy storage performance.
[0061] The PVDF-LIG / Graphene composite material forms a sheet-like network structure that creates continuous, dense, and flexible conductive pathways on the surface of MSCs, enabling efficient charge collection and providing ample channels for ion transport. The sheet-like structure of graphene has an inherent advantage in constructing stable, continuous, and low-resistance conductive-ion transport networks, which is the core reason for its optimal energy storage performance.
[0062] Compared to the limitations of traditional micro supercapacitor (MSCs) fabrication processes, such as limited processing precision, difficulty in optimizing material properties, and high energy consumption, this method achieves precise control over laser energy input and action mode by setting the processing parameters of the femtosecond laser and adjusting the position of the moving reflector to split the femtosecond laser into two laser pulses. This precise control enables micron- or nanon-scale patterning on flexible fluorine-containing polar polymer substrates, thus overcoming the limitations of traditional processing methods in achieving fine patterning.
[0063] This application provides a flexible sensor, which includes a miniature supercapacitor obtained by the supercapacitor fabrication method described above.
[0064] Silver paste is applied to the two electrodes of a miniature supercapacitor, and the electrodes are connected by wires to extract signals. After encapsulation, a flexible sensor is formed.
[0065] Specifically, such as Figure 13 As shown, silver paste is applied to both ends of the electrode to construct a conductive path. The electrode is connected with a wire to lead out the signal, and the connection part is wrapped and sealed with insulating tape to improve structural stability and electrical insulation. Finally, the sealed sensor is placed on a 65°C constant temperature hot plate and baked for 1 hour to complete the curing and bonding of the electrode and the substrate, ensuring stable sensor performance.
[0066] To expand the practical applications of PVDF-LIG / Graphene MSCs, we will further explore their electrochemical performance after series-parallel connection. Figure 14 The metallographic microscopy image shows the integrity of the parallel structure after two MSCs units are connected in parallel. Figure 15 The CV curves show that the area enclosed by the CV curves after parallel connection is approximately twice that of a single MSC cell; corresponding to Figure 16 The GCD curves show that the charge-discharge time after parallel connection is approximately twice that of a single cell. This result demonstrates that parallel connection allows for the summation of total capacity while maintaining a constant operating voltage, confirming the good performance synergy of the prepared MSCs when connected in parallel. Figure 17 Metallurgical microscopy images of two MSCs units connected in series are presented, clearly demonstrating the integrity of the tandem structure. Electrochemical test results show that... Figure 18The CV curves confirm that, under the same constant current density conditions, the maximum charging voltage after series connection increases from 0.8 V for a single cell to 1.6 V; further analysis... Figure 19 The GCD curves show that the potential window width of series-connected MSCs is twice that of a single cell. This phenomenon indicates that series connection allows for the superposition of total voltages while maintaining a constant total capacity, demonstrating that the series structure of MSCs achieves effective voltage superposition.
[0067] This application provides an application of a flexible sensor, which is used to detect human physiological signals.
[0068] Figure 20 The figures show the CV curves of the same MSCs device under different bending conditions. It can be seen that under each bending condition, the CV curves almost completely overlap and maintain typical rectangular characteristics, with no significant deformation or peak shift, indicating that the device possesses excellent mechanical flexibility and bending resistance. This characteristic can effectively broaden its application scenarios, especially suitable for fields with stringent requirements for device flexibility, such as integrated circuits, wearable microelectronic devices, and implantable medical devices.
[0069] To investigate the charge-discharge cycle durability of MSCs, a test was conducted at a voltage window of 0.8 V and a voltage of 2 mA. cm - ² A series of 10,000 continuous charge-discharge cycles were performed at the current density, and the results are as follows: Figure 21 As shown in the figure. After cycling, the device exhibited a capacitance retention rate of 97.81%, far exceeding the cycling stability level of most micro energy storage devices, confirming that the MSCs possess excellent electrochemical stability and structural durability, meeting the application requirements for long-term repeated charge-discharge cycles. To evaluate the storage reliability of the MSCs, electrochemical performance tests were performed on the device after it had been rested for 7 days following fabrication, and the results were compared with those of a newly fabricated device. Figure 22 and Figure 23 As shown in the figure. Tests revealed that the capacitance performance of the device after 7 days of storage was almost identical to that of a newly fabricated device; further quantitative analysis showed that the areal capacitance measured daily within 7 days remained stable at 76.95-77.52 mF. cm - Between 2, the fluctuation range is only 0.57 mF. cm - ², with a relative deviation of less than 1%, fully demonstrates that these MSCs have excellent long-term storage stability, providing key support for their large-scale production and long-term storage applications.
[0070] Flexible sensors exhibit excellent response sensitivity and signal recognition for human body movements in different locations. These findings contribute to the future development of sensors for speech recognition, health monitoring, human-computer interaction, and sports rehabilitation. In conclusion, given their superior performance, PVDF-LIG / Graphene MSCs-based sensors are promising candidates for multifunctional applications in wearable human sensors.
[0071] In summary, compared with existing technologies, it has the following beneficial effects: Precise modification of PVDF films using graphene dispersion as a medium enables the efficient preparation of functional composite materials. Femtosecond laser-based liquid-phase material preparation methods exhibit significant advantages over traditional chemical synthesis routes due to their environmental friendliness and the absence of dispersants. In this strategy, under the action of the first femtosecond laser pulse, the PVDF surface precipitates due to the high power of the laser (…). At a plasma pulse intensity of 10¹³ W / cm², the ionization threshold is reached, and the plasma channel heats the solvent to generate microbubbles, creating a confined reaction environment. A second pulse induces selective CF bond breakage, driving molecular chain reconstruction and forming a sheet-like laser-induced graphene (LIG) substrate. Simultaneously, the same energy pulse dissociates the graphene sheets in the dispersion into nanoparticles. These nanoparticles attach to the LIG substrate, ultimately constructing a sheet-like LIG-nanographene composite functional layer. The PVDF-LIG / Graphene MSCs fabricated using femtosecond laser direct writing achieved an areal capacitance of 58.25 mF·cm². - ², compared to PVDF-LIGMSCs without graphene nanoparticles (15.75 mF·cm⁻¹), - ²) Improved by 3.7 times. Further employing dual-pulse time-domain shaping to control the pulse delay, the device showed optimal performance at a delay of 20 ps: 0.3 mA·cm⁻¹. - The peak area ratio capacitance at current density reaches 162 mF·cm². - ², and exhibits excellent cycle stability (97.81% capacitance retention after 10,000 charge-discharge cycles). These MSCs were used to construct a flexible sensor, and human trials confirmed their sensitive response to physiological activities in multiple body parts. This not only enriches the methods for preparing flexible functional materials but also provides theoretical and experimental support for next-generation flexible electronic devices (for speech recognition, health monitoring, human-computer interaction, and motor rehabilitation assessment).
[0072] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0073] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 this application.
Claims
1. A method for preparing a graphene composite material, characterized in that, include: Set the processing parameters for the femtosecond laser, adjust the position of the moving mirror in the femtosecond laser processing system, and split the femtosecond laser into two laser pulses; The femtosecond laser processing system is activated, and the femtosecond laser is used to process the fluorine-containing polar polymer flexible substrate placed in the graphene dispersion to obtain the graphene composite material. The graphene composite material includes the fluorine-containing polar polymer flexible substrate and the sheet-like LIG-nanographene particle composite functional layer.
2. The method for preparing graphene composite materials as described in claim 1, characterized in that, The fluorinated polar polymer flexible substrate includes polytetrafluoroethylene, fluorinated ethylene propylene, polychlorotrifluoroethylene, and polyvinylidene fluoride.
3. The method for preparing graphene composite materials as described in claim 1, characterized in that, The processing parameters of the femtosecond laser include laser wavelength, single pulse energy, repetition frequency, and laser power, wherein the laser wavelength is 1030 nm, the single pulse energy is 7.5 μJ, the repetition frequency is 20 kHz, and the laser power is 90 mW-100 mW.
4. The method for preparing graphene composite materials as described in claim 1, characterized in that, The dual laser pulses include a first femtosecond laser pulse and a second femtosecond laser pulse, and the delay time between the first femtosecond laser pulse and the second femtosecond laser pulse is in the range of 0ps-30ps.
5. A method for fabricating a supercapacitor, characterized in that, include: Obtain the interdigitated electrode pattern of the designed supercapacitor and convert the interdigitated electrode pattern into a scanning path for a femtosecond laser. The femtosecond laser scanning in the femtosecond laser processing system is controlled according to the obtained scanning path, and a micro supercapacitor based on graphene composite material is obtained by executing the graphene composite material preparation method as described in any one of claims 1-4.
6. A flexible sensor, characterized in that, This includes miniature supercapacitors obtained using the supercapacitor fabrication method described in claim 5; Silver paste is applied to the two electrodes of a miniature supercapacitor, and the electrodes are connected by wires to extract signals. After encapsulation, a flexible sensor is formed.
7. An application of a flexible sensor, characterized in that, The flexible sensor described in claim 6 is used to detect human physiological signals.