Preparation method of double-sided sensor based on femtosecond laser induced graphene

Abstract

The invention relates to a preparation method of a double-sided sensor based on femtosecond laser induced graphene, and belongs to the technical field of laser application. According to the method, in the preparation process, the lower surface of a polyether-ether-ketone film is subjected to laser processing in an out-of-focus state to prepare the LIG sensor; and the defocusing distance is greater than the thickness of the material, so that LIG is not generated on the upper surface when the lower surface is processed. And performing laser processing on the upper surface of the polyether-ether-ketone film in a focusing upper surface state to prepare the LIG sensor. The LIG processing patterns on the upper and lower surfaces are flexible in position and shape. If the positions of the processed patterns on the upper and lower surfaces are the same, the LIGs on the upper and lower surfaces are highly consistent at the corresponding positions. When the LIG processing pattern shapes of the upper surface and the lower surface are different, the sensor can be endowed with multifunctional characteristics, and different detection requirements and application scenes can be met, for example, one surface can be used for strain detection, and the other surface can be used for humidity detection.

Description

Technical Field

[0001] The invention relates to a method for preparing a double-sided sensor based on femtosecond laser induced graphene, and belongs to the technical field of laser application. Background Art

[0002] Graphite carbon-based materials exhibit excellent physical and chemical properties, including ultra-high electron mobility, excellent thermal stability, outstanding electrical conductivity, good optical transparency, high mechanical strength and large specific surface area, etc., and are therefore widely used in many fields such as wearable electronic devices and interactive robots. However, traditional graphene preparation methods, such as mechanical exfoliation, chemical vapor deposition, epitaxial growth, reduced graphene oxide, etc., have problems such as complex process, chemical residues, masking, harsh preparation conditions, low yield and high cost, which greatly limit their application development. In contrast, laser-induced graphene (LIG) technology can prepare graphene with good physical and chemical properties in an in-situ, single-step and scalable manner in air, and has become a new alternative technology for low-cost and large-scale production of graphene.

[0003] LIG has good conductivity, robustness and stability. As a conductive sensing unit and electrode material for flexible wearable sensors, it has good sensitivity, wide detection range, fast response time, mechanical robustness and long-term stability. At present, the most commonly used laser in the preparation of LIG is CO with a wavelength of 10.6 μm. 2 Laser, however, has low processing accuracy due to its obvious thermal effect, is prone to overheating and ablation, and has a limited range of substrate choices. In contrast, femtosecond laser has the advantages of relatively small processing heat-affected zone, extremely high peak power, and good penetration, which achieves higher processing accuracy, lower heat-affected zone, and a wider range of substrate choices in LIG preparation.

[0004] In the preparation of multifunctional wearable flexible sensors, the first option is to prepare multiple LIG sensors on the surface of the polymer, but this often causes mutual interference between sensors and cannot meet the size restrictions of portable wearable devices. The second option is to process LIG double-sided sensors on the upper and lower surfaces of the polymer. The multifunctional sensors can be separated while retaining the central insulating substrate. It not only meets the independence between sensors, but also reduces the size. However, the common processing method is to turn the sample over after processing one side and then process the other side. This processing method is complicated to operate, the positions of the upper and lower sensors are difficult to correspond well, and it is easy to damage the first processed LIG. The use of femtosecond laser to prepare LIG can realize the in-situ preparation of double-sided sensors, while having the advantages of single-step processing and scalability. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of singleness and complicated operation of the existing LIG-based double-sided sensor preparation method, and a method for preparing a double-sided sensor based on femtosecond laser induced graphene is provided. This method is mainly used to prepare a double-sided sensor based on LIG. During the preparation process, the lower surface of the polyetheretherketone film is first processed by laser in a defocused state to prepare a LIG sensor. The defocus distance should be greater than the material thickness to ensure that LIG will not be generated on the upper surface when the lower surface is processed. Afterwards, the upper surface of the polyetheretherketone film is laser processed in a focused upper surface state to prepare a LIG sensor. The LIG processing patterns on the upper and lower surfaces are flexible in position and shape. If the positions of the upper and lower surface processing patterns are the same, it can be ensured that the LIG on the upper and lower surfaces are highly consistent at the corresponding positions. When the shapes of the LIG processing patterns on the upper and lower surfaces are different, the sensor can be given multifunctional characteristics to meet different detection needs and application scenarios, such as one side can be used for strain detection and the other side can be used for humidity detection.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A method for preparing a double-sided sensor based on femtosecond laser induced graphene, by precisely adjusting the laser focus position, it is possible to ensure that only the lower surface is laser processed without ablating the upper surface of a polyetheretherketone film, thereby realizing efficient preparation of a lower surface LIG sensor; the focus position is moved again to the upper surface for focusing processing, thereby realizing preparation of an upper surface LIG sensor, thereby realizing in-situ preparation of a double-sided LIG sensor; the method comprises the following steps:

[0008] Step 1: Introduce the laser vertically into the objective lens and adjust the laser processing focus to coincide with the imaging focus;

[0009] Step 2: fix the polyetheretherketone film on a glass slide, fix the glass slide on a three-dimensional electric-controlled displacement platform, and obtain the laser focus position by adjusting the Z axis of the three-dimensional electric-controlled displacement platform until the upper surface of the polyetheretherketone film is clearly seen;

[0010] Step 3, moving the Z axis of the three-dimensional electric-controlled displacement platform upward, the moving distance being greater than the thickness of the polyetheretherketone film, so that both the upper and lower surfaces are in a defocused state, and LIG processing of the lower surface of the polyetheretherketone film is achieved;

[0011] Step 4: Move the Z axis of the three-dimensional electric-controlled displacement platform downward, and refocus the laser onto the upper surface of the polyetheretherketone film to achieve LIG processing on the upper surface of the polyetheretherketone film;

[0012] Copper wires were connected to the double-sided sensor electrodes, and conductive silver paste was dripped onto the double-sided sensor electrodes. The conductive silver paste was dried and solidified to complete the electrical connection of the double-sided sensor, and the strain sensor was encapsulated using medical polyurethane tape.

[0013] During the preparation of the upper and lower surface LIG sensors, if at least one side is processed into a humidity sensor, 5 μL of graphene oxide solution needs to be dripped onto the LIG interdigital electrodes; the graphene oxide solution is a humidity-sensitive material.

[0014] The LIG processing patterns on the upper and lower surfaces are flexible in position and shape. When the processing patterns on the upper and lower surfaces are in the same position, the LIG on the upper and lower surfaces can be highly consistent at the corresponding positions. When the LIG processing patterns on the upper and lower surfaces are different, the sensor can be given multifunctional characteristics to meet different detection needs and application scenarios. For example, one side can be used for strain detection, and the other side can be used for humidity detection.

[0015] The device for implementing the above method comprises a femtosecond laser, an attenuation disk, an electrically controlled shutter, a reflector, a dichroic mirror, an illuminator, a charge coupled device (CCD), a three-dimensional electrically controlled displacement platform and a 10X objective lens; the femtosecond laser sequentially passes through the attenuation disk for nonlinear energy adjustment, and then is controlled by the electrically controlled shutter to pass through; then the femtosecond laser is introduced into the objective lens through the reflector and the dichroic mirror; the laser can be focused or defocused on the upper surface of the polyetheretherketone film by controlling the Z axis of the three-dimensional electrically controlled displacement platform; for the imaging system, the white light source is provided by the illuminator, and the reflected light from the sample surface propagates along the opposite path, first passes through the objective lens, then passes through the dichroic mirror, and finally enters the charge coupled device (CCD);

[0016] Also included is a far-infrared graphite heating stage;

[0017] Beneficial Effects

[0018] 1. To solve the problems of singleness and complicated operation in the existing LIG-based double-sided sensor preparation method, the present invention makes innovative improvements to the LIG-based double-sided sensor preparation method by taking advantage of the unique advantages of femtosecond laser processing, including high-precision processing, small heat-affected zone, no need for subsequent treatment, wide application range, and powerful micro-nano processing capabilities. The upper and lower surfaces of the polyetheretherketone film are laser processed separately in the environment using a femtosecond laser, and the in-situ LIG-based double-sided sensor preparation is realized without flipping the polyetheretherketone film. This not only simplifies the operation process and reduces the risk of damage to the polyetheretherketone film during operation, but also improves the preparation efficiency and ensures the relative position accuracy of the upper and lower surface processing.

[0019] 2. The LIG processing patterns on the upper and lower surfaces are flexible in position and shape. If the positions of the processing patterns on the upper and lower surfaces are the same, it can ensure that the LIG on the upper and lower surfaces are highly consistent in the corresponding positions. This consistency is conducive to stable performance in some application scenarios that require high sensor uniformity. When the shapes of the LIG processing patterns on the upper and lower surfaces are different, the sensor can be given multifunctional characteristics to meet different detection needs and application scenarios. For example, one side can be used for strain detection, which can accurately detect the strain changes of finger bending; the other side can be used for humidity detection, which can sensitively sense changes in the humidity of nasal breathing. This method provides a new idea and technical approach for the preparation of double-sided sensors, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flow chart of the technical solution of the present invention.

[0021] Figure 2 Laser processing diagram Figure 1 The lower surface and the upper surface of the polyetheretherketone film are processed in sequence according to the designed pattern.

[0022] Figure 3 Schematic diagram of the pattern structure and actual processing of the double-sided sensor 1.

[0023] Figure 4 This is the actual application performance diagram of the double-sided sensor 1 (humidity response, finger bending).

[0024] Figure 5 Laser processing diagram Figure 2 The lower surface and the upper surface of the polyetheretherketone film are processed in sequence according to the designed pattern.

[0025] Figure 6 Schematic diagram of the pattern structure of double-sided sensor 2.

[0026] Figure 7 This is the actual application performance diagram of the double-sided sensor 2 (finger press).

[0027] Among them, 1-femtosecond laser, 2-attenuation disk, 3-electrically controlled shutter, 4-first coated reflector, 5-second coated reflector, 6-first dichroic mirror, 7-second dichroic mirror, 8-illumination lamp, 9-charge coupled device CCD, 10-10X objective lens, 11-polyetheretherketone film (thickness 150μm), 12-glass slide, 13-three-dimensional electrically controlled displacement platform, 14-computer control system. DETAILED DESCRIPTION

[0028] In order to better understand the method of the present invention, the technical solution of the present invention is further described in detail below in conjunction with specific embodiments.

[0029] Example 1

[0030] A method for preparing a double-sided sensor based on femtosecond laser induced graphene, the specific steps are as follows:

[0031] (1) The optical path system used in the present invention is as follows Figure 1 As shown. The laser at the laser light outlet of the femtosecond laser 1 is a Gaussian laser with a pulse width of 350fs, a wavelength of 1030nm, and a repetition rate of 800kHz. The laser emitted by the laser is nonlinearly regulated through the attenuation disk 2, and the passage of the laser is controlled by the electric shutter 3.

[0032] (2) The femtosecond laser is introduced into the objective lens 10 through the first coated reflector 4, the second coated reflector 5, and the first dichroic mirror 6. The Z axis of the three-dimensional electrically controlled displacement platform 13 is controlled to focus the laser on the upper surface of the polyetheretherketone film 11 sample fixed on the slide 12. The white light source of the imaging system is provided by the illumination lamp 8, and the light reflected from the sample surface passes through the objective lens 10, the first dichroic mirror 6, and the second dichroic mirror 7 and enters the charge coupled device CCD9. Before laser processing, the three-dimensional electrically controlled displacement platform 13 and the charge coupled device CCD9 are coordinated to adjust the processing focus to coincide with the imaging focus, and then the lower surface and the upper surface of the polyetheretherketone film 11 sample are processed in turn, as shown in FIG. Figure 2 shown.

[0033] (3) After the upper surface of the polyetheretherketone film 11 sample is clearly seen, the three-dimensional electric-controlled displacement platform 13 is moved up by 230 μm, and the movement of the three-dimensional electric-controlled displacement platform 13 and the opening and closing of the electric-controlled shutter 3 are controlled by the computer control system 14 to realize laser processing on the lower surface of the polyetheretherketone film 11 sample. The laser scanning speed is 3 mm / s, the scanning interval is 25 μm, the scanning number is 1, the laser power is 250 mW, and the processing pattern and size are as follows: Figure 3 shown.

[0034] (4) The three-dimensional electric-controlled displacement platform 13 is moved down by 230 μm to see the upper surface of the polyetheretherketone film 11 sample again. The computer control system 14 controls the movement of the three-dimensional electric-controlled displacement platform 13 and the switch of the electric-controlled shutter 3 to achieve laser processing on the upper surface of the polyetheretherketone film 11 sample. The laser scanning speed is 7 mm / s, the scanning interval is 25 μm, the scanning number is 1, the laser power is 150 mW, the interdigital electrode interval is 100 μm, and the processing pattern and size are as follows: Figure 3 The purpose of reducing the laser processing power on the upper surface is to retain the central insulating substrate, and the purpose of increasing the scanning speed is to reduce the sensor size and the line width of the interdigital electrodes.

[0035] (5) Connect copper wires to LIG electrodes, drip conductive silver paste to upper and lower LIG electrodes, and dry on a far-infrared graphite heating table at 80°C for 20 min to solidify the conductive silver paste and fix the copper wires. The lower surface LIG sensor is encapsulated with medical polyurethane tape to complete the preparation of strain sensors, and the upper surface LIG sensor is dripped with 5 μL of graphene oxide solution at the LIG interdigital electrodes to complete the preparation of humidity sensors. The actual application performance of the double-sided sensor is shown in Figure 2. Figure 4 shown.

[0036] Example 2

[0037] A method for preparing a double-sided sensor based on femtosecond laser induced graphene, the specific steps are as follows:

[0038] (1) Same as Example 1 (1)

[0039] (2) The femtosecond laser is introduced into the objective lens 10 through the first coated reflector 4, the second coated reflector 5, and the first dichroic mirror 6. The Z axis of the three-dimensional electrically controlled displacement platform 13 is controlled to focus the laser on the upper surface of the polyetheretherketone film 11 sample fixed on the slide 12. The white light source of the imaging system is provided by the illumination lamp 8, and the light reflected from the sample surface passes through the objective lens 10, the first dichroic mirror 6, and the second dichroic mirror 7 and enters the charge coupled device CCD9. Before laser processing, the three-dimensional electrically controlled displacement platform 13 and the charge coupled device CCD9 are coordinated to adjust the processing focus to coincide with the imaging focus, and then the lower surface and the upper surface of the polyetheretherketone film 11 sample are processed in turn, as shown in FIG. Figure 5 shown.

[0040] (3) After the upper surface of the polyetheretherketone film 11 sample is clearly seen, the three-dimensional electric-controlled displacement platform 13 is moved up by 230 μm, and the movement of the three-dimensional electric-controlled displacement platform 13 and the opening and closing of the electric-controlled shutter 3 are controlled by the computer control system 14 to realize laser processing on the lower surface of the polyetheretherketone film 11 sample. The laser scanning speed is 3 mm / s, the scanning interval is 25 μm, the scanning number is 1, the laser power is 250 mW, and the processing pattern and size are as follows: Figure 6 shown.

[0041] (4) The three-dimensional electric-controlled displacement platform 13 is moved down by 230 μm to see the upper surface of the polyetheretherketone film 11 sample again. The computer control system 14 controls the movement of the three-dimensional electric-controlled displacement platform 13 and the opening and closing of the electric-controlled shutter 3 to achieve laser processing on the upper surface of the polyetheretherketone film 11 sample. The laser scanning speed is 1 mm / s, the scanning interval is 25 μm, the scanning number is 1, the laser power is 350 mW, and the processing pattern and size are as follows. Figure 6 As shown in Figure 2, the laser processing power is increased and the scanning speed is reduced on the upper surface in order to remove the central insulating substrate.

[0042] (5) Connect copper wires to LIG electrodes, drip conductive silver paste to the upper and lower LIG electrodes, and dry them on a far-infrared graphite heating table at 80°C for 20 minutes to solidify the conductive silver paste and fix the copper wires. The upper and lower LIG sensors are encapsulated with medical polyurethane tape to complete the preparation of the double-sided sensor. The actual application performance of the double-sided sensor is as follows: Figure 7 shown.

[0043] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a double-sided sensor based on femtosecond laser induced graphene, characterized in that: By precisely adjusting the laser focus position, it is possible to ensure that only the lower surface is laser processed without ablating the upper surface of the polyetheretherketone film, thereby realizing efficient preparation of the lower surface LIG sensor; the focus position is moved again to the upper surface for focusing processing, thereby realizing preparation of the upper surface LIG sensor, thereby realizing in-situ double-sided LIG sensor preparation; the process includes the following steps: Step 1: Introduce the laser vertically into the objective lens and adjust the laser processing focus to coincide with the imaging focus; Step 2: fix the polyetheretherketone film on a glass slide, fix the glass slide on a three-dimensional electric-controlled displacement platform, and obtain the laser focus position by adjusting the Z axis of the three-dimensional electric-controlled displacement platform until the upper surface of the polyetheretherketone film is clearly seen; Step 3, moving the Z axis of the three-dimensional electric-controlled displacement platform upward, the moving distance being greater than the thickness of the polyetheretherketone film, so that both the upper and lower surfaces are in a defocused state, and LIG processing of the lower surface of the polyetheretherketone film is achieved; Step 4: Move down the Z axis of the three-dimensional electric-controlled displacement platform, and refocus the laser onto the upper surface of the polyetheretherketone film to achieve LIG processing on the upper surface of the polyetheretherketone film.

2. A method for preparing a double-sided sensor based on femtosecond laser induced graphene as claimed in claim 1, characterized in that: Copper wires were connected to the double-sided sensor electrodes, and conductive silver paste was dripped onto the double-sided sensor electrodes. The conductive silver paste was dried and solidified to complete the electrical connection of the double-sided sensor, and the strain sensor was encapsulated using medical polyurethane tape.

3. The method for preparing a double-sided sensor based on femtosecond laser induced graphene according to claim 1, characterized in that: During the preparation of the upper and lower surface LIG sensors, if at least one side is processed into a humidity sensor, 5 μL of graphene oxide solution needs to be dripped onto the LIG interdigital electrodes; the graphene oxide solution is a humidity-sensitive material.

4. The method for preparing a double-sided sensor based on femtosecond laser induced graphene according to claim 1, characterized in that: The LIG processing patterns on the upper and lower surfaces are flexible in position and shape; when the processing patterns on the upper and lower surfaces are in the same position, the LIG on the upper and lower surfaces can be highly consistent at the corresponding positions; when the LIG processing patterns on the upper and lower surfaces are different, the sensor can be endowed with multifunctional characteristics to meet different detection needs and application scenarios.

5. A device for implementing the method according to any one of claims 1 to 4, characterized in that: It includes a femtosecond laser, an attenuation disk, an electrically controlled shutter, a reflector, a dichroic mirror, an illuminator, a charge coupled device (CCD), a three-dimensional electrically controlled displacement platform and a 10X objective lens; the femtosecond laser passes through the attenuation disk in turn for nonlinear energy regulation, and then is controlled by the electrically controlled shutter to pass through; and then is introduced into the objective lens through the reflector and the dichroic mirror; By controlling the Z-axis of the three-dimensional electrically controlled displacement platform, the laser can be focused or defocused on the upper surface of the polyetheretherketone film; for the imaging system, the white light source is provided by the illumination lamp, and the light reflected from the sample surface propagates along the opposite path, first passing through the objective lens, then through the dichroic mirror, and finally entering the charge-coupled device CCD.

6. The device according to claim 5, characterized in that: Also includes far infrared graphite heating stage.

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