Flexible pressure sensor based on laser deoxidized graphene

Abstract

The invention discloses a flexible pressure sensor based on laser deoxidized graphene, which comprises a dielectric layer and a graphene conductive induction layer which are sequentially arranged on the surface of a flexible substrate, and is characterized in that the conductive induction layer is a laser deoxidized graphene LDG structure film layer formed by irradiating graphene oxide with 266 nm pulse laser. The LDG film has a layered corrugated structure, nanosphere particles are uniformly distributed in the LDG film, the LDG film is compounded with the GO dielectric layer in a vacuum filtration mode to form an integral film body, the thickness of the obtained film layer is uniform, and an interlayer conductive path is stable. The material has a relatively high specific surface area and excellent flexibility and force-electricity conversion performance. The pressure sensor provided by the invention has ultrahigh sensitivity and excellent stability, and is suitable for the fields of wearable equipment, robot tactile feedback, medical health monitoring and the like. In addition, a laser solid-phase reduction process is adopted, a solvent and a post-treatment step are not needed, the process is simple, the preparation period is short, and good batch production adaptability and environmental friendliness are achieved.

Description

Technical Field

[0001] This invention relates to the field of flexible sensors and their fabrication technology, specifically to a flexible pressure sensor based on laser-deoxidized graphene. Background Technology

[0002] In recent years, with the rapid development of emerging fields such as wearable electronics, intelligent robots, human-computer interaction, and health monitoring, flexible pressure sensors have received widespread attention as core components. Achieving high sensitivity, wide dynamic range, excellent mechanical stability, and environmental adaptability in these sensors has become an important research direction in this field.

[0003] Graphene oxide (GO) exhibits great potential in sensor device fabrication due to its excellent flexibility, processability, and two-dimensional structure rich in oxygen-containing functional groups. GO materials possess good solubility and dispersibility, and can be deposited into films using simple wet processes, making them an important source of electroactive materials for flexible sensors.

[0004] Currently used GO reduction methods include thermal reduction, chemical reduction, and hydrothermal reduction. Although these methods can improve conductivity to some extent, they generally suffer from drawbacks such as complex processes, high energy consumption, and significant pollution, which are detrimental to the green fabrication and mass production of flexible devices. Furthermore, these methods have low precision in terms of reduction degree and structural control, making it difficult to meet the dual requirements of high-performance sensors for both microstructure and electrical performance.

[0005] To improve the specific surface area and conductive pathway construction efficiency of GO, researchers have attempted to introduce porous structures or heterogeneous templates into GO, such as combining GO with SiO2 nanoparticles and forming porous structures through etching, which effectively increases the material's surface area. However, such methods typically rely on large amounts of chemical reagents, resulting in cumbersome cleaning, impurity residues, complex processes, and environmental unfriendliness, making it difficult to simultaneously ensure device cleanliness and batch consistency.

[0006] On the other hand, in the deposition process of GO thin films, traditional methods often use liquid phase methods such as drop coating, spin coating or spray coating. GO suspension is deposited between flexible substrate electrodes by drop coating to form a sensing film. Although high sensitivity is obtained, the film formation process is easily affected by fluidity, wettability and other factors, which leads to problems such as uncontrollable film thickness, severe edge effect and poor structural repeatability, which is not conducive to the stable fabrication of high-performance flexible devices.

[0007] In summary, the key to realizing high-performance flexible sensors lies in developing a GO deoxygenation and film formation technology that simultaneously possesses high reduction efficiency, structural tunability, and process simplicity. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a flexible pressure sensor based on laser-deoxidized graphene, which solves the problems of uneven film structure, insufficient specific surface area, and difficulty in balancing sensitivity and stability in existing flexible pressure sensors based on graphene oxide. It has the advantages of controllable process, high sensitivity, stable structure and strong environmental adaptability.

[0009] To address the aforementioned technical problems, this invention provides a flexible pressure sensor based on laser-deoxidized graphene, comprising a dielectric layer and a conductive sensing layer sequentially disposed on a flexible substrate, wherein the conductive sensing layer is formed by irradiating graphene oxide (GO) with a pulsed laser with a wavelength of 266 nm to form a laser-deoxidized graphene (LDG) film, and the dielectric layer is a graphene oxide (GO) film.

[0010] Furthermore, the method for preparing the conductive sensing layer is as follows: Graphene oxide (GO) powder was prepared using the Hummers method. The prepared GO powder was placed at the bottom of a three-necked flask and irradiated with a laser under continuous nitrogen gas flow protection. After irradiation, the obtained solid material is collected, washed with water and ethanol, and dried to obtain laser deoxidized graphene (LDG) powder, which is used to construct the conductive sensing layer.

[0011] Furthermore, the laser-deoxidized graphene (LDG) powder contains graphene nanospheres with a particle size of 4–8 nm, which are uniformly distributed between the wrinkled structures to form a three-dimensional conductive network.

[0012] Furthermore, laser-deoxidized graphene (LDG) powder is prepared into an LDG aqueous solution, and graphene oxide (GO) powder is prepared into a GO aqueous solution. The GO aqueous solution is first filtered through vacuum to form a film, and then the LDG aqueous solution is filtered onto the surface of the graphene oxide (GO) film to form a composite film. This composite film is then fixed to a flexible substrate using PDMS adhesive. Copper wires are fixed using conductive silver paste to achieve electrical connection with external circuitry, thus completing the assembly of the flexible pressure sensor device.

[0013] Furthermore, after film formation, the composite film is transferred to an ethanol coagulation bath for rapid solvent exchange, resulting in structural rearrangement to reduce electrostatic repulsion between films and enhance π→π* stacking. Specifically, by gradually adding ethanol, the carboxyl groups (-COOH) and hydroxyl groups (-OH) on the GO surface are converted from ionic to neutral, thereby reducing charge repulsion and promoting tighter interlayer stacking and hydrogen bond network formation, thus achieving a highly adhesive physical composite structure.

[0014] Furthermore, the dielectric layer has a thickness of 300-500 nm, and the conductive sensing layer has a thickness of 3-4 μm.

[0015] Furthermore, the pulsed laser spot diameter during the laser irradiation process is 0.1 cm, the pulse frequency is 10 Hz, the single pulse energy is about 120 mJ, and the irradiation time is selected as 15–25 minutes.

[0016] Furthermore, the wavelength selection method for pulsed lasers is as follows: A molecular model of isolated GO system of graphene oxide (GO) powder was constructed, including carboxyl functional groups, carbonyl functional groups, hydroxyl functional groups, and epoxy functional groups; Using density functional theory, the molecular model of the isolated GO system was geometrically optimized. After optimization, frequency calculations were performed to obtain the energy thresholds required for electrons of carboxyl, carbonyl, hydroxyl, and epoxy functional groups to transition from the ground state to the excited state. Using the maximum energy threshold as the basis for calculation, the wavelength is calculated according to the formula: ; Where h is Planck's constant, c is the laser speed, and E laser λ represents the maximum energy threshold, and λ is the wavelength.

[0017] Furthermore, after frequency calculation, the Gaussian was used as the broadening function, and the Mulliken atomic orbital projection method was employed to decouple the projected density of states of the carboxyl, carbonyl, hydroxyl, and epoxy functional groups.

[0018] Furthermore, in the process of geometric optimization and frequency calculation, the electron exchange correlation is treated with B3LYP hybrid functionals and expanded with wave function using the Bopp basis set 6-31+G**, which includes d / p polarization functions.

[0019] The beneficial effects of this invention are: This invention combines laser irradiation with vacuum filtration to construct high-quality dielectric and conductive sensing layers. The resulting film possesses a high specific surface area, a robust three-dimensional conductive network, and excellent mechanical flexibility. This method eliminates the need for chemical reducing agents, making the process environmentally friendly and simple, with good repeatability and process stability. The film formed through vacuum filtration exhibits uniform thickness, structural stability, and strong controllability, which is beneficial for improving batch consistency of devices. The constructed flexible sensor demonstrates ultra-high sensitivity (ΔR / R0 = 42.3%) and excellent cyclic stability (fluctuation <0.32% after 300 bends) in physiological signal detection, showcasing broad application prospects and commercial potential. Attached Figure Description

[0020] Figure 1 This is a flowchart of the laser reduction preparation process of graphene oxide according to the present invention; Figure 2These are the FT-IR spectra of laser-deoxidized graphene (LDG) of this invention under different irradiation times; Figure 3 These are the XPS photoelectron spectroscopy analysis results of the laser-deoxidized graphene oxide (LDG) of this invention; Figure 4 This is a comparison of the Raman spectra of the laser-deoxidized graphene oxide (LDG) samples of this invention; Figure 5 This is a comparison of the infrared spectra of laser-deoxidized graphene oxide (LDG) samples prepared under different conditions of this invention with those of raw GO. Figure 6 These are the UV-Vis-NIR absorption spectra of the original GO and laser-deoxidized graphene oxide (LDG) samples prepared under different laser wavelengths in this invention; Figure 7 This is a cross-sectional SEM image of the GO / LDG bilayer composite membrane prepared in this invention; Figure 8 This is a schematic diagram of vacuum filtration film formation according to the present invention, showing the self-leveling mechanism and film homogenization process under negative pressure drive; Figure 9 These are the long-term stability test results of the pressure sensor of the present invention under different pressure conditions; Figure 10 These are the pressure response and cyclic hysteresis curves of the LDG-based pressure sensor of this invention under different laser fabrication conditions; Figure 11 This is a three-dimensional distribution diagram of the relative resistance change rate (ΔR / R0) of the LDG-based flexible pressure sensor of the present invention under different temperature and humidity environments; Figure 12 This is a schematic diagram of the structure and working mechanism of the sensing layer of the LDG pressure sensor proposed in this invention; Figure 13 This is a schematic diagram of the flexible pressure sensor based on laser deoxidized graphene (LDG) of the present invention in multiple application scenarios. Figure 14 This is a schematic diagram of the response curve of the flexible pressure sensor of the present invention to an ultralight mass object (5.2mg petals); Figure 15 This is a schematic diagram of the resistance response curve of the flexible pressure sensor of the present invention in radial artery pulse monitoring; Figure 16 This is the real-time resistance response curve of the flexible pressure sensor of the present invention in throat vibration monitoring; Figure 17 This is a schematic diagram of the differential stress detection of the flexible pressure sensor of the present invention when it is attached to different finger joints for ball gripping actions. Figure 18This invention demonstrates the current stability performance of the flexible pressure sensor under long-term cyclic testing of a bionic robotic arm. Figure 19 This is a comparison of the sensitivity (ΔR / R0) of the flexible pressure sensor of this invention with that of a previously reported two-dimensional flexible resistive sensor.

[0021] Figure 20 This is the X-ray photoelectron spectrum of the experimental batch GO of this invention; Figure 21 This is the projected density of states diagram of each functional group in this invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0023] This embodiment of the flexible pressure sensor based on laser-deoxidized graphene (LDG) of the present invention includes a dielectric layer and a conductive sensing layer sequentially constructed on a flexible substrate. The conductive sensing layer is prepared by vacuum filtration of laser-modulated graphene oxide (LDG). By controlling the laser wavelength, pulse energy, and irradiation environment, local modification and defect introduction of the graphene oxide structure are achieved, resulting in reduced graphene oxide (LDG) material with high specific surface area and excellent load response characteristics. This LDG dispersion is then used as a vacuum filtration film-forming raw material to produce a dense, controllable-thickness functional thin film, significantly improving the sensor's performance in dynamic pressure response and environmental stability. This results in a pressure sensor with high sensitivity, high reliability, and good repeatability, suitable for high-performance flexible electronic device applications.

[0024] The sensor manufacturing process is as follows: After preparing graphene oxide powder using a modified Hummers method, GO powder was placed at the bottom of a three-necked flask. Under continuous nitrogen protection, the dispersion was irradiated with a pulsed laser for 15–25 minutes. The short-wavelength laser selectively excited oxygen-containing functional groups such as hydroxyl and epoxy groups in GO, initiating photodissociation and simultaneously inducing wrinkles and localized conductive networks on the surface of the sheets.

[0025] During laser irradiation, oxygen-containing functional groups such as hydroxyl and epoxy groups in GO undergo selective excitation and dissociation, forming uniform graphene nanospheres and wrinkled structures on the surface, thus restoring some of the sp. 2 Conjugated network; graphene nanospheres are generated by laser ablation process under the parameters of this application.

[0026] After laser irradiation, the sample was washed sequentially with deionized water and ethanol, and dried to constant weight to obtain laser-deoxidized graphene oxide powder (LDG). The LDG powder was redispersed in deionized water to prepare an aqueous dispersion, which was then deposited sequentially with GO on a flexible substrate using vacuum filtration to form a composite film structure. The resulting composite film was cut to an appropriate size (e.g., 1.5cm × 1.5cm), fixed to an LCP flexible substrate using PDMS adhesive, and copper wires were fixed with conductive silver paste to achieve electrical connection with external circuitry, thus completing the assembly of the flexible pressure sensor device. The preferred thickness of the LDG sensing layer is approximately 3.7μm, and the preferred thickness of the GO dielectric layer is approximately 400nm; sensors with these dimensions exhibit good flexibility and response accuracy.

[0027] like Figure 1 As shown, in preparing the functional films used for the dielectric layer and conductive sensing layer, the graphene oxide dispersion was first modulated using laser irradiation, and then the modulated LDG dispersion was deposited into a film by vacuum filtration. Before laser irradiation, the graphene oxide dispersion was prepared to a specified concentration and placed in a beaker, followed by laser irradiation treatment under set parameters. The following is a comparative explanation of the graphene oxide modulation process using different laser wavelengths, energy densities, and irradiation times: LDG 266 -15: After synthesizing graphene oxide powder via the Hummers method, 100 mg of GO sample was placed at the bottom of a three-necked flask and subjected to laser reduction using an Nd:YAG pulsed laser (266 nm, 10 Hz, 120 mJ) under continuous nitrogen gas flow (80 sccm) protection for 15 minutes. The resulting product was named LDG. 266 -15.

[0028] LDG 266 -20: After synthesizing graphene oxide powder via the Hummers method, 100 mg of GO sample was placed at the bottom of a three-necked flask and subjected to laser reduction using an Nd:YAG pulsed laser (266 nm, 10 Hz, 120 mJ) under continuous nitrogen gas flow (80 sccm) protection for 20 minutes. The resulting product was named LDG. 266 -20.

[0029] LDG 266 -25: After synthesizing graphene oxide powder via the Hummers method, 100 mg of GO sample was placed at the bottom of a three-necked flask and subjected to laser reduction using an Nd:YAG pulsed laser (266 nm, 10 Hz, 120 mJ) under continuous nitrogen gas flow (80 sccm) protection for 25 minutes. The resulting product was named LDG. 266 -25.

[0030] LDG 532 -20: After synthesizing graphene oxide powder via the Hummers method, 100 mg of GO sample was placed at the bottom of a three-necked flask and subjected to laser reduction using an Nd:YAG pulsed laser (532 nm, 10 Hz, 120 mJ) under continuous nitrogen gas flow (80 sccm) protection for 20 minutes. The resulting product was named LDG. 532 -20.

[0031] LDG 532 -40: After synthesizing graphene oxide powder via the Hummers method, 100 mg of GO sample was placed at the bottom of a three-necked flask and subjected to laser reduction using an Nd:YAG pulsed laser (532 nm, 10 Hz, 120 mJ) under continuous nitrogen gas flow (80 sccm) protection for 40 minutes. The resulting product was named LDG. 532 -40.

[0032] LDG 1064 -20: After synthesizing graphene oxide powder via the Hummers method, 100 mg of GO sample was placed at the bottom of a three-necked flask and subjected to laser reduction using an Nd:YAG pulsed laser (1064 nm, 10 Hz, 120 mJ) under continuous nitrogen gas flow (80 sccm) protection for 20 minutes. The resulting product was named LDG. 1064 -20.

[0033] LDG 1064 -60: After synthesizing graphene oxide powder via the Hummers method, 100 mg of GO sample was placed at the bottom of a three-necked flask and subjected to laser reduction using an Nd:YAG pulsed laser (1064 nm, 10 Hz, 120 mJ) under continuous nitrogen gas flow (80 sccm) protection for 60 minutes. The resulting product was named LDG. 1064 -60.

[0034] LDG after laser treatment 266 -15, LDG 266 -20 and LDG 266Compare with -25, and refer to Figure 2 The FT-IR spectra shown indicate that as the irradiation time increases from 15 minutes to 25 minutes, the LDG... 266 The absorption peaks of oxygen-containing functional groups such as –OH, C=O, and C–O in the sample gradually weakened, indicating an increased degree of deoxygenation. Among them, LDG 266 -20 achieves the best balance between restoration effect and structural integrity, avoiding LDG 266 -25 Thermal damage caused by excessive radiation. Combined with... Figure 3 and Figure 4 XPS and Raman analysis, LDG 266 -20 forms with sp 2 The graphene framework, which is dominated by hybridization, has a stable structure and is suitable for subsequent device integration.

[0035] LDG after laser treatment 266 -20, LDG 532 -40 and LDG 1064 -60 was compared with the untreated GO sample, as referenced Figure 5 As shown, LDG 266 -20 at 3432cm⁻ 1 The complete disappearance of the O–H stretching vibration peak indicates that the hydroxyl functional group in GO has been almost completely removed, while in LDG... 532 -40 and LDG 1064 The -60 concentration still retains a distinct characteristic peak of oxygen-containing functional groups, indicating poor reduction efficiency. (Refer to...) Figure 6 In the UV-VIS absorption spectrum, GO exhibits a significant π→π* transition absorption at a wavelength of 266 nm. Energy can be transferred to oxygen-containing functional groups via a non-radiative pathway, inducing selective fragmentation. Density functional theory calculations show that the hydroxyl group has the highest excitation energy, approximately 4.7 eV, corresponding to a laser wavelength of 266 nm. Therefore, LDG... 266 The deoxygenation effect is most significant at -20°C.

[0036] In summary, LDG 266 -20 exhibits the best performance in removing O–H functional groups, achieving complete reduction in a short time and providing high-quality precursor materials for subsequent device fabrication; while LDG 532 -40 and LDG 1064 -60 requires a longer time and still retains some oxygen-containing groups, resulting in lower deoxygenation efficiency.

[0037] With LDG 266 A sensing membrane was prepared using -20°C as the raw material. The laser-reduced graphene oxide product was uniformly dispersed in deionized water. An appropriate amount of the dispersion was taken and deposited onto a filter membrane using vacuum filtration. Nitrogen gas was continuously introduced during the constant-pressure filtration process to maintain an inert environment. Figure 7 The SEM image shown indicates that the composite film has a GO layer thickness of approximately 400 nm and an LDG layer thickness of approximately 3.7 μm. The LDG layer exhibits a porous, wrinkled structure with some interlayer aggregation, which helps improve electron transport efficiency, while the GO layer maintains an ordered dielectric layer structure. The resulting film has good flexibility and excellent conductivity, making it suitable for use as a flexible pressure sensing membrane.

[0038] The membrane deposition process during vacuum filtration possesses a self-regulating mechanism: (Refer to...) Figure 8 In areas where the flow rate increases, nanosheets preferentially accumulate in thinner regions, achieving self-balancing of thickness. This ultimately results in a dense, uniformly thick graphene film. Compared to traditional deposition methods, this approach offers higher controllability and consistency, facilitates complete peeling of the film from the filter membrane, and meets the requirements for subsequent integration into flexible pressure sensors.

[0039] The graphene composite film was cut into 1.5cm×1.5cm square units, bonded to the LCP substrate with PDMS adhesive, and copper wires were fixed with conductive silver paste to achieve electrical connection, thus finally producing a pressure sensor device.

[0040] See Figure 9-11 Based on LDG 266 The pressure sensor fabricated at -20 exhibits excellent performance in many aspects. During a 10-hour continuous loading stability test, its relative resistance change (ΔR / R0) remained essentially constant, without significant drift, indicating that the device possesses long-term stable operating capability. Figure 9 In the load-unload loop, its hysteresis error is less than 2%, significantly better than LDG. 532 -40 (12.4%) and LDG 1064 -40 (14.6%), demonstrating good consistency in mechanical response ( Figure 10 ) In an environment of 20–80°C and 30–90%RH, LDG 266 The output fluctuation of the -20 sensor was only 4.6%, which is more environmentally stable compared to other samples (13.2%, 20.3%). Figure 11 ).

[0041] Figure 12 This study further revealed the impact of different reduction structures on device performance. The wrinkled structure forms an effective conductive channel through particle bridging, improving the balance between sensitivity and detection range; the dense structure is sensitive but not suitable for large strains; the multi-gap structure is suitable for large-range pressure detection, indicating that different morphologies are adapted to different application scenarios.

[0042] Figure 13 This demonstrates the sensor's versatility in practical applications. It can detect minute pressure applied by as little as 5.2 mg of flower petals. Figure 14Clearly record the biphasic characteristics of the arterial pulse and achieve heart rate recognition. Figure 15 It can also identify the muscle vibration patterns of the throat during vocalization. Figure 16 ), to achieve force distribution analysis during finger grasping ( Figure 17 Simultaneously, this device can be integrated into a robotic arm to achieve precise responses to complex hand gestures. Figure 18 ).according to Figure 19 As shown, the sensor performance of this patent invention is significantly better than that of sensors proposed in known papers.

[0043] This application also takes the fabrication of sensors under irradiation with different laser parameters as an example: LDG 532 40: Graphene oxide was dispersed in deionized water to form a graphene oxide dispersion, and then irradiated with a 532 nm pulsed laser for 40 min under continuous nitrogen protection. During the laser irradiation, some hydroxyl, carboxyl, and epoxy groups in the graphene oxide were removed, forming a preliminary conductive sheet structure. The resulting sample was named LDG. 532 40.

[0044] Using LDG 532 40. A sensitive thin film was prepared by vacuum filtration and assembled into a flexible pressure sensor M1. Compared with the control sensor prepared by ordinary GO, the performance of M1 is significantly improved. Under the same external force loading, the output resistance changes more significantly, the response speed is faster, and it is less affected by environmental humidity and temperature, exhibiting higher sensitivity and stability.

[0045] LDG 1064 60: Graphene oxide was dispersed in deionized water to form a graphene oxide dispersion, which was then irradiated with a 1064 nm pulsed laser under continuous nitrogen protection for 60 min. Under this wavelength condition, laser reduction mainly relied on thermal effects, some oxygen-containing functional groups were removed, and a preliminary conductive network was formed in the material. The resulting material was named LDG. 1064 60.

[0046] LDG 1064 60. A flexible pressure sensor was formed by vacuum filtration and assembled. Compared with sensors prepared with ordinary GO membranes, this sensor exhibits a larger relative resistance change under pressure, a more stable response, and improved resistance to environmental interference.

[0047] To improve specific surface area, this invention proposes a laser-modulated specific surface area optimization process. By irradiating graphene oxide with a laser in an aqueous dispersion, short-wavelength laser light (e.g., 266 nm) can trigger π→π* electron transitions, promoting local deoxidation and introducing wrinkles and micro-defects, thereby significantly increasing the material's specific surface area. This process is carried out entirely in aqueous solution, making it environmentally friendly, requiring no additional chemical reagents, and introducing no impurities.

[0048] Regarding film deposition, this invention employs a vacuum filtration process to prepare the sensitive membrane. By adjusting the filtration pressure, the film layers spontaneously level out under negative pressure, while maintaining an appropriate interlayer porosity. This facilitates effective separation from the filter membrane and maximizes sensitivity. Vacuum filtration also provides a natural "self-leveling" effect, making the film thickness and morphology more controllable, thus providing a reliable guarantee for the subsequent stable performance of the sensor and its commercial mass production.

[0049] In laser modulation techniques, the selection of laser wavelength is extremely important and directly affects the reconstruction effect. Therefore, this application also provides a method for accurately selecting the wavelength: First, a model needs to be constructed. The structural model was built using GaussView 6.0 software. A complete molecular model of the isolated GO system was constructed based on the classic Lerf–Klinowski model. This model not only includes hydroxyl and epoxy functional groups, but also specifically introduces carbonyl and carboxyl functional groups at the edge sites, making the model more realistically reflect the complex chemical structure of GO. In the graphene oxide model constructed based on actual GO, the ratio of carboxyl:carbonyl:hydroxyl:epoxy is 4:7:8:6, which, along with X-ray photoelectron spectroscopy (XPS, see reference...)... Figure 20 The experimental data (as shown) show good consistency. Notably, the carbon-to-oxygen ratio (C / O) of the constructed model is 1.75, which is not significantly different from the XPS characterization result (1.753).

[0050] Subsequently, geometry optimization and frequency calculations based on density functional theory (DFT) were performed, both in the Gaussian16 program. The electron exchange correlation was handled using a B3LYP hybrid functional, and wavefunction expansion was performed using 6-31+G**. This basis set scheme, by introducing d / p polarization functions, can accurately describe the electronic polarization effect of carbon-oxygen bonds.

[0051] Gaussian16 is a standard software for quantum chemical calculations, supporting DFT calculations and offering high accuracy and reliability. It is suitable for complex systems such as graphene oxide. Density functional theory (DFT) is an efficient quantum mechanical method that strikes a good balance between computational cost and accuracy, suitable for medium to large-scale systems, such as the graphene oxide model. Geometric optimization aims to find the minimum energy structure of the system, while frequency calculations are used to verify that the optimized structure is a minimum (without imaginary frequencies) and to obtain vibrational properties. B3LYP is a hybrid functional widely used in organic molecule and materials calculations, providing accurate predictions of electronic structure, energy, and bonding properties. The basis set 6-31+G** contains d / p polarization functions, accurately describing the electronic polarization effects of carbon-oxygen bonds.

[0052] The energy required for an electron in a corresponding functional group to transition from the ground state to an excited state can be obtained through frequency calculation; this is known as the energy threshold. By comparing the energy thresholds of various functional groups, the largest one is selected as the basis for calculation.

[0053] To more intuitively see the energy threshold for excitation, refer to... Figure 21 As shown, the density of states was obtained through frequency calculations. Specifically, Gaussian was used as the broadening function, and the projected density of states of each oxygen-containing functional group (including epoxy, hydroxyl, carboxyl, and carbonyl groups) was decoupled using the Mulliken atomic orbital projection method. In the figure, visual results can be quickly obtained from 0 to the first peak. The maximum energy threshold here is 4.70 eV, therefore this is used as the basis for the calculations.

[0054] The calculation formula is: Where h is Planck's constant (4.135667662 × 10⁻¹⁵ eV⋅s) and c is the speed of light (2.998 × 10¹⁷ nm / s). Substituting these values, the wavelength λ≈264 nm can be calculated. Using this wavelength for laser modulation is sufficient to drive π electrons in the sp² hybrid domain of carbon atoms in the GO framework to undergo π→π* jumps. These electrons, excited to the antibonding π* orbitals, are in an unstable high-energy state. Subsequently, the excited π electrons transfer energy to neighboring oxygen-containing functional groups through radiation. This localized energy injection leads to the vibrational excitation and breaking of chemical bonds (such as CO, C=O, OH) within the functional groups, ultimately triggering the decomposition and desorption of oxygen-containing groups.

[0055] Using the methods described above, the laser wavelength parameters for the current batch of GO can be quickly and accurately determined, ensuring the restoration effect.

[0056] The embodiments described above are merely preferred embodiments for fully illustrating the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A flexible pressure sensor based on laser-deoxidized graphene, characterized in that, The invention comprises a dielectric layer and a conductive sensing layer sequentially disposed on a flexible substrate. The conductive sensing layer is formed by laser deoxidizing graphene (LDG) film by irradiating graphene oxide (GO) with a pulsed laser with a wavelength of 266 nm. The dielectric layer is a graphene oxide (GO) film. The dielectric layer is fixed on the flexible substrate with PDMS adhesive. The dielectric layer and the conductive sensing layer are formed into a composite structure by vacuum filtration.

2. The flexible pressure sensor based on laser-deoxidized graphene as described in claim 1, characterized in that, The method for preparing the conductive sensing layer is as follows: Graphene oxide (GO) powder was prepared using the Hummers method. The prepared GO powder was placed at the bottom of a three-necked flask and irradiated with a laser under continuous nitrogen gas flow protection. After irradiation, the obtained solid material is collected, washed with water and ethanol, and dried to obtain laser deoxidized graphene (LDG) powder, which is used to construct the conductive sensing layer.

3. The flexible pressure sensor based on laser-deoxidized graphene as described in claim 2, characterized in that, Laser-deoxidized graphene (LDG) powder contains graphene nanospheres with a particle size of 4–8 nm, which are uniformly distributed between the wrinkled structures to form a three-dimensional conductive network.

4. The flexible pressure sensor based on laser-deoxidized graphene as described in claim 2, characterized in that, Laser-deoxidized graphene (LDG) powder was prepared into an LDG aqueous solution, and graphene oxide (GO) powder was prepared into a GO aqueous solution. The GO aqueous solution was first filtered into a film by vacuum filtration, and then the LDG aqueous solution was filtered into a film on the surface of the graphene oxide (GO) film to form a composite film.

5. The flexible pressure sensor based on laser-deoxidized graphene as described in claim 4, characterized in that, After film formation, the composite membrane is transferred to an ethanol coagulation bath for structural rearrangement through rapid solvent exchange, which reduces electrostatic repulsion between membranes and enhances π→π* stacking.

6. The flexible pressure sensor based on laser-deoxidized graphene as described in claim 1, characterized in that, The dielectric layer has a thickness of 300-500 nm, and the conductive sensing layer has a thickness of 3-4 μm.

7. The flexible pressure sensor based on laser-deoxidized graphene as described in claim 2, characterized in that, The pulsed laser spot diameter during the laser irradiation process is 0.1 cm, the pulse frequency is 10 Hz, the single pulse energy is about 120 mJ, and the irradiation time is selected as 15–25 minutes.

8. The flexible pressure sensor based on laser-deoxidized graphene as described in claim 7, characterized in that, The wavelength selection method for pulsed lasers is as follows: A molecular model of isolated GO system of graphene oxide (GO) powder was constructed, including carboxyl functional groups, carbonyl functional groups, hydroxyl functional groups, and epoxy functional groups; Using density functional theory, the molecular model of the isolated GO system was geometrically optimized. After optimization, frequency calculations were performed to obtain the energy thresholds required for electrons of carboxyl, carbonyl, hydroxyl, and epoxy functional groups to transition from the ground state to the excited state. Using the maximum energy threshold as the basis for calculation, the wavelength is calculated according to the formula: ； Where h is Planck's constant, c is the laser speed, and E laser λ represents the maximum energy threshold, and λ is the wavelength.

9. The flexible pressure sensor based on laser-deoxidized graphene as described in claim 8, characterized in that, After frequency calculation, the Gaussian was used as the broadening function, and the Mulliken atomic orbital projection method was used to decouple the projected density of states of carboxyl, carbonyl, hydroxyl and epoxy functional groups.

10. The flexible pressure sensor based on laser-deoxidized graphene as described in claim 8, characterized in that, In the process of geometry optimization and frequency calculation, the electron exchange correlation is treated with B3LYP hybrid functionals and expanded with wave function using the Bopp basis set 6-31+G**, which includes d / p polarization functions.

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