Processing method and application of femtosecond laser induced graphene array

Abstract

The invention discloses a femtosecond laser induced graphene array processing method and application, and the processing method comprises the following steps: in an ultra-clean environment, using a femtosecond laser direct writing processing system; a polyimide film is placed on a three-dimensional free moving platform, a Z axis of the three-dimensional free moving platform is regulated and controlled through a closed-loop control system, femtosecond laser is focused on the surface of the polyimide film through a focusing objective lens, and a clear object image is presented; the repetition frequency of femtosecond laser is set through a closed-loop control system, and a focusing objective lens selects a proper aperture for machining; the power of the femtosecond laser is adjusted by adjusting the angle of the optical attenuator; parameters are set according to the steps, and the three-dimensional porous graphene array structure is processed through a preset program in a closed-loop control system. According to the processing method, micron-grade processing can be realized, and effective and uniform large-scale induction can be realized.

Description

Technical Field

[0001] The present invention relates to the field of flexible sensing, and in particular to a processing method and application of a femtosecond laser-induced graphene array. Background Art

[0002] In the field of wind speed sensing, traditional rigid sensors are restricted by the limitations of a single detection axis and mechanical structure. In breeze flow fields as low as 0.5m / s or in complex environments with multi-directional turbulence, their measurement errors can be as high as over 40%.

[0003] Flexible pressure sensors are piezoelectric sensors that utilize the piezoresistive effect of graphene to measure surface forces. They consist of a motor layer, a graphene conductor layer, and an encapsulation layer. Laser-induced graphene (LIG) is a novel graphene material synthesis technique that uses laser irradiation on a carbon-containing material (polyimide film), causing the carbon atoms in the material to recombine and graphitize, forming graphene. Traditional methods for obtaining graphene, such as mechanical exfoliation or chemical vapor deposition, damage the structure during the process. The basic principle of mechanical exfoliation is to use external force to overcome the van der Waals forces between crystal layers, exfoliating the crystals layer by layer to obtain single-layer or multi-layer crystal structures. However, the amount of crystals obtained per exfoliation is very small, making it difficult to meet the needs of large-scale production and inefficient. The entire exfoliation process requires multiple repetitions, and the number and size of the resulting crystals are difficult to precisely control, resulting in low production efficiency and unsuitable for industrial large-scale production. Chemical vapor deposition (CVD) is a highly demanding process, requiring specialized equipment and environmental conditions such as high temperature and high vacuum. This leads to high equipment costs and skilled operators. The process is complex, requiring significant time and effort for process optimization and commissioning. Furthermore, the transfer process can introduce impurities, defects, or damage the crystal, impacting its performance and quality. Consequently, a process for the efficient and large-scale production and utilization of graphene is currently lacking.

[0004] There have been many achievements based on laser-induced graphene at home and abroad. Professor Meng Qingshi's team at Shenyang Aerospace University published a patent titled "Flexible Capacitive Pressure Sensor of Laser-Induced Graphene and Its Preparation Method and Application". The patent introduces "A Flexible Capacitive Pressure Sensor of Laser-Induced Graphene", which consists of a dielectric layer, an electrode layer and a packaging layer. The graphene induced by a carbon dioxide laser is the electrode layer, which realizes a single graphene block with a size of 30×80mm, a pore size of 1-5μm, a porosity of 80%-85%, and a pore size of 300μm-800μm. The sensitivity of its flexible capacitive pressure sensor is 0.09-0.13 Xiamen University researchers including Luo Tao published a paper titled "Facile and Cost-Effective Fabrication of Highly Sensitive, Fast-Response Flexible Humidity Sensors Enabled by Laser-Induced Graphene" in the journal ACS Appl. Mater. Interfaces. By designing and fabricating a multi-resistor network pressure sensor in the shape of a laser-induced graphene ring on a polyimide film layer, they demonstrated how printed electronics combined with laser-induced graphene sensors can create a fully functional microsystem. The research demonstrated how to use a 3D circuit board printer to print circuitry and use conductive and dielectric inks to encapsulate the laser-induced graphene sensor, showcasing the advantages of laser-induced graphene sensors, such as readable current, amplification, and simple wireless transmission. Professor Chen Xueye's team at Shandong University of Technology published a paper titled "Humidity / Pressure Dual-Mode Sensor for Human Health Monitoring Based on Laser-Induced Graphene" in the Chemical Engineering Journal. The research team utilized the properties of laser-induced graphene and combined them with the advantages of porous paper fibers to fabricate a flexible, wearable humidity and pressure sensor. The sensor utilizes the porosity and abundant hydroxyl groups of paper fibers, along with laser-induced graphene embedded in the paper fiber pores in the form of nanosheets. Carbon nanotubes and graphene are physically cross-linked with carboxymethyl cellulose to form a stable paper fiber membrane, which serves as the core pressure sensing framework. When external pressure is applied, the carbon nanotubes are squeezed into aggregates and connect to the electrodes, resulting in a change in resistance that generates a pressure-sensitive signal.

[0005] In summary, laser-induced graphene, as a basic component unit of sensors, has achieved considerable results. However, the above-mentioned are all large-area single pieces of graphene. Laser-induced graphene arrays still have problems such as uneven induced graphene and uneven response state. Its processing technology uses traditional carbon dioxide lasers, which have large laser spots and low induction accuracy. Summary of the Invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a processing method and application of femtosecond laser-induced graphene arrays, which can achieve micron-level processing and can effectively and uniformly induce large-scale production.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0008] In one embodiment of the present invention, a method for processing a femtosecond laser-induced graphene array and its application are proposed. The method for processing a femtosecond laser-induced graphene array comprises:

[0009] In an ultra-clean environment, a femtosecond laser direct writing processing system is used;

[0010] The polyimide film is placed on a three-dimensional free-motion platform. The Z axis of the three-dimensional free-motion platform is controlled by a closed-loop control system. The femtosecond laser is focused onto the surface of the polyimide film through a focusing objective lens, so that a clear image is presented.

[0011] The repetition rate of the femtosecond laser is set through a closed-loop control system, and the focusing objective lens selects the appropriate aperture for processing;

[0012] The power of the femtosecond laser is adjusted by adjusting the angle of the optical attenuator;

[0013] The parameters are set according to the above steps, and the three-dimensional porous graphene array structure is processed through the preset program in the closed-loop control system.

[0014] Furthermore, the femtosecond laser direct writing processing system includes: a femtosecond laser, an optical isolator, an aperture, a reflector, an optical attenuator, an imaging system, a focusing objective lens, a three-dimensional free-moving platform and a closed-loop control system, which are used to adjust the power and focus of the femtosecond laser and determine the position of the femtosecond laser light path.

[0015] Furthermore, a femtosecond laser is a laser that uses a semiconductor laser as a pump source, wherein both the oscillator and the amplifier are designed with a fully fused fiber structure for stably outputting high average power.

[0016] Furthermore, the imaging system includes an illumination light source, a reflector, and a CCD, wherein the CCD converts the received light signal into a digital signal and combines with a closed-loop control system to monitor the morphology of the polyimide film during processing in real time.

[0017] Furthermore, femtosecond laser-induced graphene arrays can cover some special curved objects. When the three-dimensional porous structure of graphene changes, its resistance will follow a linear change. By recording the difference before and after the change, the amount of change can be calculated, thereby realizing the detection of tiny mechanical deformations.

[0018] Furthermore, femtosecond laser-induced graphene arrays are used in flexible sensing of wind pressure and deformation.

[0019] Beneficial effects:

[0020] 1. The existing laser-induced graphene is limited to a single large-area graphene block. The present invention adopts femtosecond laser and its supporting processing method to achieve micron-level processing and can effectively and uniformly induce large-scale graphene.

[0021] 2. Compared with existing carbon dioxide lasers, due to the extremely short action time of femtosecond lasers, the processing process is basically "cold processing", avoiding the problems of material deformation, thermal damage and thermal stress that may be caused by traditional hot processing methods, which is conducive to maintaining the original performance and microstructure of the material. The energy, pulse width, repetition frequency and other parameters of the femtosecond laser can be precisely controlled, thereby achieving precise control of the processing process and processing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a diagram of the architecture of the femtosecond laser direct writing processing system of the present invention;

[0023] In the figure: 1- femtosecond laser, 2- optical isolator, 3- first aperture, 4- second aperture, 5- first reflecting mirror, 6- optical attenuator, 7- first reflecting mirror, 8- third aperture, 9- second reflecting mirror, 10- imaging system, 11- focusing objective lens, 12- three-dimensional free-moving platform, 13- closed-loop control system;

[0024] Figure 2 This is a measurement circuit diagram of the present invention based on a femtosecond laser-induced graphene array;

[0025] Figure 3 Schematic diagram of the deployment of the femtosecond laser-induced graphene array of the present invention applied to an aircraft wing;

[0026] Figure 4 yes Figure 3 Enlarged view of part A. DETAILED DESCRIPTION

[0027] The principles and spirit of the present invention will be described below with reference to several exemplary embodiments. It should be understood that these embodiments are provided solely to enable those skilled in the art to better understand and design the present invention, and are not intended to limit the scope of the present invention in any way. Rather, these embodiments are provided to make this disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0028] Those skilled in the art will appreciate that embodiments of the present invention may be implemented as a device, apparatus, apparatus, method, or computer program product. Therefore, the present disclosure may be implemented in the following forms: entirely in hardware, entirely in software (including firmware, resident software, microcode, etc.), or in a combination of hardware and software.

[0029] According to an embodiment of the present invention, a processing method and application of a femtosecond laser-induced graphene array are proposed. A large-scale patterned graphene array is induced on the surface of a polyimide film based on a femtosecond laser as the basic unit of a flexible sensor, and a related measurement circuit is designed to achieve high density and accurate measurement, and support multiple detection degrees of freedom. Based on existing inventions and applications, it can be proved that femtosecond laser-induced graphene can indeed be used in flexible sensing.

[0030] The principles and spirit of the present invention are explained in detail below with reference to several representative embodiments of the present invention.

[0031] The overall scheme adopted by the present invention includes the construction of a femtosecond laser direct writing processing system, a processing method of a femtosecond laser-induced graphene array, and a measurement circuit based on femtosecond laser-induced graphene.

[0032] 1. Construction of femtosecond laser direct writing processing system

[0033] like Figure 1 As shown, the femtosecond laser direct writing processing system includes: a femtosecond laser 1, an optical isolator 2, a first aperture 3, a second aperture 4, a first reflector 5, an optical attenuator 6, a first reflector 7, a third aperture 8, a second reflector 9, an imaging system 10, a focusing objective lens 11, a three-dimensional free-moving platform 12 and a closed-loop control system 13.

[0034] (1) Femtosecond laser 1: The high-power femtosecond laser used in the present invention is a semiconductor-pumped fiber laser. It uses a semiconductor laser as a pump source to provide energy for the laser. The oscillator and amplifier are both designed with a fully fused fiber structure, which avoids power fluctuations caused by spatial coupling and can stably output a high average power. Through unique dispersion design and nonlinear control, the laser can achieve a large pulse energy while maintaining good pulse output quality. The MOPA architecture, that is, the master oscillator power amplifier architecture, is used. The master oscillator generates seed light, which is then amplified by the power amplifier, so that the laser's pulse width, frequency, power and other parameters have high dynamic range tuning characteristics. The use of excellent industrial-grade optical and mechanical design and the "zero adjustable mirror frame" solution ensures the reliability and long-term stability of the system. Its working principle is: the light emitted by the semiconductor pump source excites the doped ions (such as erbium, ytterbium, etc.) in the optical fiber, causing the doped ions to transition to a high energy level. When the number of high-energy level particles is large enough, stimulated radiation is generated to form a laser. When laser outputs of different wavelengths are required, the fundamental frequency light can be converted into second harmonic (515nm), third harmonic (343nm), fourth harmonic (257nm), etc. through the optional harmonic module to meet different application requirements.

[0035] (2) Processing optical path: The present invention uses femtosecond laser direct writing processing optical path, such as Figure 1As shown, the system primarily includes components 1-12, which function to adjust laser power, focus, and determine the position of the femtosecond laser optical path. The modulated femtosecond laser is focused onto a three-dimensional free-motion translation stage 12 via a focusing objective lens 11. In practice, focusing objective lenses 11 with different numerical apertures are used to process metal plasmonic nanostructures at varying powers. For example, at a repetition rate of 200 kHz, a 5x focusing objective lens 11 can produce graphene blocks with an average value of 100 ohms. At the same power, a smaller aperture results in a higher femtosecond laser concentration, which, while remaining within the material's tolerance limits, improves processing efficiency.

[0036] (3) Imaging system (10 is a simplified schematic diagram in the figure): Its main internal components include an illumination light source, a reflector, and a CCD. The illumination light source is a common LED light source, which provides sufficient light intensity for processing. The CCD converts the received light signal into a digital signal and combines it with a closed-loop control system 13 to monitor the morphology of the polyimide film (sample) in real time during processing.

[0037] (4) Three-dimensional free-moving translation stage 12: A three-dimensional free-moving translation stage from PI company is used, and the polyimide film (sample) can be moved to any position through a closed-loop control system 13.

[0038] 2. Processing method of femtosecond laser-induced graphene array

[0039] Processing steps:

[0040] ① Place a 50μm thick, 10cm x 10cm long and wide polyimide film on a three-dimensional free-motion translation stage 12; use a closed-loop control system 13 to adjust the Z axis of the three-dimensional free-motion translation stage 12, and focus the femtosecond laser onto the surface of the polyimide film through the focusing objective lens 11, so that a clear image is presented;

[0041] ② Change the parameters in the closed-loop control system 13, set the repetition frequency of the femtosecond laser to 200 kHz, and select 10× focusing lens 11 for processing;

[0042] ③ Adjust the power of the femtosecond laser by adjusting the angle of the optical attenuator 6;

[0043] ④ Set the parameters according to the above steps and process the area 4×4mm through the set program 2 Three-dimensional porous graphene array structure.

[0044] ⑤ In order to ensure the precision and accuracy of processing, the above processing processes are carried out in an ultra-clean environment, and the processing will not stop until the processing is completed.

[0045] 3. Measurement circuit based on femtosecond laser-induced graphene array

[0046] This circuit is a precision strain gauge circuit based on laser-induced graphene array. Its working principle is: using graphene array to replace traditional pressure strain gauges, because its flexible characteristics can well cover some special curved objects. When the three-dimensional porous structure of graphene changes, its resistance will follow the linear change. By recording the difference before and after the change, the change amount can be calculated to judge the degree of mechanical deformation. It can measure tiny mechanical deformation and amplify the signal output through the signal amplifier AD8221. Compared with traditional strain gauges, the laser-induced graphene array can achieve more accurate and rapid mechanical deformation detection. The circuit is divided into three parts. The first is the input part (such as Figure 2 Part 1 shows the Wheatstone bridge based on laser-induced graphene, which is used to detect tiny mechanical deformation at the detection end; the second is the operational amplifier part (AD8221 as shown in the figure). Figure 2 The second part is shown as follows): used to amplify the input signal and output the signal after filtering; the third is the power supply part: provides the operating voltage for the circuit.

[0047] The present invention uses polyimide film as the base material, adopts femtosecond laser induced graphene array, and designs an innovative three-dimensional mesh topology structure while maintaining 0.01 While achieving an ultra-low pressure detection threshold, it also achieves 360° omnidirectional wind field component analysis capabilities. Each sensing unit adopts an interdigitated electrode structure, combined with a multi-source signal fusion algorithm of deep learning, which can improve the detection sensitivity of the lateral wind speed component to several orders of magnitude, which is 2 orders of magnitude higher than traditional equipment. The core breakthrough of this invention comes from the revolutionary innovation at the material level - a three-dimensional porous graphene framework constructed by femtosecond laser direct writing technology, whose unique Dirac cone band structure enables the carrier mobility to reach , which is several orders of magnitude higher than traditional electronic sensors. The ultra-high conductivity brought about by this quantum-like effect, combined with the super-elastic base material (polyimide film) that maintains a stable response under strain, makes the array's piezoresistive sensitivity basically unchanged after bending. It is particularly noteworthy that its unique three-dimensional porous microstructure can convert micro-pressure changes on the order of 0.1Pa into a resistance change rate, which is equivalent to the pressure applied at a single point on an A4 paper being accurately captured. In terms of pressure distribution perception, the flexible array exhibits advantages that are difficult to achieve with traditional rigid devices: through a distributed layout of 56 micro-sensing units per unit, combined with measurement circuits and algorithms, the three-dimensional pressure distribution of complex surfaces can be reconstructed within 3000ms. The breakthrough performance of this invention stems from three major innovative mechanisms:

[0048] The first is the graphene quantum confinement effect: a graphene-like lattice with a thickness of less than 3nm makes electrons exhibit relativistic characteristics, with a migration speed of 1 / 300 the speed of light; the second is the special microstructure design: the three-dimensional porous microstructure can convert 0.05% strain into a detectable electrical signal; the third is multi-physics field coupling: the piezoresistive-capacitive-piezoelectric triple sensing mechanism works together, and cross-validation ensures data reliability. In the aviation field, a 0.1mm thick flexible array can be completely attached to the curved surface of an aircraft wing, such as Figure 3 and Figure 4 As shown, it can analyze instantaneous turbulence generated by boundary layer separation in real time. In smart healthcare, bionic electronic skin can simultaneously monitor pulse and epidermal microtremors. And when applied to industrial robot end effectors, its ultra-high sampling frequency can accurately discern torque fluctuations as small as 0.2N, providing tactile feedback for precision assembly. This flexible sensing technology, which breaks through the limits of materials, is redefining the boundaries of intelligent sensing.

[0049] It should be noted that although the operations of the method of the present invention are described in a specific order in the above embodiments and drawings, this does not require or imply that these operations must be performed in this specific order, or that all illustrated operations must be performed to achieve the desired results. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0050] The processing method and application of the femtosecond laser-induced graphene array proposed in the present invention have the following advantages:

[0051] 1. The existing laser-induced graphene is limited to a single large-area graphene block. The present invention adopts femtosecond laser and its supporting processing method to achieve micron-level processing and can effectively and uniformly induce large-scale graphene.

[0052] 2. Compared with existing carbon dioxide lasers, due to the extremely short action time of femtosecond lasers, the processing process is basically "cold processing", avoiding the problems of material deformation, thermal damage and thermal stress that may be caused by traditional hot processing methods, which is conducive to maintaining the original performance and microstructure of the material. The energy, pulse width, repetition frequency and other parameters of the femtosecond laser can be precisely controlled, thereby achieving precise control of the processing process and processing effect.

[0053] Although the spirit and principles of the present invention have been described with reference to several specific embodiments, it should be understood that the present invention is not limited to the specific embodiments disclosed, and the division into various aspects does not mean that the features of these aspects cannot be combined to benefit. Such division is only for the convenience of expression. The present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0054] Regarding the limitation of the protection scope of the present invention, those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the protection scope of the present invention.

Claims

1. A processing method and application of a femtosecond laser-induced graphene array, characterized in that: The method for processing a femtosecond laser-induced graphene array comprises: In an ultra-clean environment, a femtosecond laser direct writing processing system is used; The polyimide film is placed on a three-dimensional free-motion platform. The Z axis of the three-dimensional free-motion platform is controlled by a closed-loop control system. The femtosecond laser is focused onto the surface of the polyimide film through a focusing objective lens, so that a clear image is presented. The repetition rate of the femtosecond laser is set through a closed-loop control system, and the focusing objective lens selects the appropriate aperture for processing; The power of the femtosecond laser is adjusted by adjusting the angle of the optical attenuator; After setting the parameters according to the above steps, the three-dimensional porous graphene array structure is processed through the preset program in the closed-loop control system; Femtosecond laser-induced graphene arrays can cover some special curved objects. When the three-dimensional porous structure of graphene changes, its resistance will change linearly. By recording the difference before and after the change, the amount of change can be calculated, thereby realizing the detection of tiny mechanical deformations.

2. The processing method and application of femtosecond laser induced graphene array according to claim 1, characterized in that: The femtosecond laser direct writing processing system includes: a femtosecond laser, an optical isolator, an aperture, a reflector, an optical attenuator, an imaging system, a focusing objective lens, a three-dimensional free moving platform and a closed-loop control system, which is used to adjust the power and focus of the femtosecond laser and determine the position of the femtosecond laser light path.

3. The processing method and application of femtosecond laser induced graphene array according to claim 2, characterized in that: The femtosecond laser is a laser that uses a semiconductor laser as a pump source, wherein both the oscillator and the amplifier are designed with a fully fused optical fiber structure to stably output high average power.

4. The processing method and application of femtosecond laser-induced graphene array according to claim 2, characterized in that: The imaging system includes an illumination light source, a reflector and a CCD, wherein the CCD converts the received light signal into a digital signal and combines with a closed-loop control system to monitor the morphology of the polyimide film in real time during the processing.

5. The processing method and application of femtosecond laser induced graphene array according to claim 1, characterized in that: The femtosecond laser induced graphene array is used in flexible sensing of wind pressure and deformation perception.

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