Improved laser-induced graphene and preparation method thereof

Abstract

The invention discloses improved laser-induced graphene and a preparation method thereof.The preparation method comprises the steps that a base material is cleaned and dried, a polyimide film is cut, and the polyimide film is tightly attached to the surface of the base material; performing patterning processing on the surface of the polyimide film by using laser to obtain patterned laser-induced graphene; placing the patterned laser-induced graphene in a vacuum environment; and performing pulse processing on the patterned laser-induced graphene to obtain the improved laser-induced graphene. According to the preparation method of the laser-induced graphene, a pulse current processing mode is adopted, and the laser-induced graphene is adjusted so as to change the number of graphene layers, induction strain in crystal lattices and an electron energy band structure. The pulse current processing in the step S4 is short in time consumption, the crystal structure of the laser-induced graphene can be accurately controlled by adjusting pulse parameters such as voltage and duration, the operation is more convenient, the controllability is higher, and the influence on the environment is extremely small.

Description

Technical Field

[0001] The invention relates to the field of laser induced graphene, and in particular to improved laser induced graphene and a preparation method thereof. Background Art

[0002] Laser-induced graphene, or LIG for short, is a new type of two-dimensional material that has the characteristics of high conductivity, high flexibility, porous structure, and maskless patterning. It is widely used in the field of flexible electronic devices. However, in the process of preparing laser-induced graphene, due to laser irradiation, the inherent amorphous properties of the laser-induced graphene surface will appear locally. This amorphous structure can reduce its own conductivity, resulting in an increase in the resistivity of the electronic devices prepared using it, thereby impairing the performance of the electronic devices and limiting the application of laser-induced graphene in electronic devices such as sensors.

[0003] In the prior art, methods for repairing defects in graphene materials mainly include overall heating and chemical reduction. However, when using the above methods to repair defects, the carbonization of the entire material leads to ablation of the polymer substrate during the repair process. At the same time, there is a lack of control over the patterning of the material, and the chemical reduction method cannot change the structure of the amorphous carbon ring. Summary of the invention

[0004] The purpose of the present invention is to provide an improved laser induced graphene and a preparation method thereof, so as to solve the problem that the inherent amorphous properties appear locally on the surface of the above-mentioned laser induced graphene, resulting in an increase in the resistivity of electronic devices prepared using the graphene.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for preparing laser-induced graphene, comprising the following steps:

[0007] S1: cleaning and drying the substrate, cutting the polyimide film, and closely attaching the polyimide film to the surface of the substrate to form a processing area on the surface of the substrate;

[0008] S2: Using laser to pattern the surface of polyimide film to obtain patterned laser-induced graphene;

[0009] S3: placing the patterned laser-induced graphene in step S2 in a vacuum environment;

[0010] S4: Pulse processing the patterned laser induced graphene to obtain improved laser induced graphene.

[0011] In the method for preparing laser induced graphene, in step S1, the processing area is a square area, and the side length of the processing area is 1 to 20 mm.

[0012] In the preparation method of laser induced graphene, the pattern formed by the patterning process includes a plurality of dumbbell-shaped patterns distributed at intervals, the dumbbell-shaped pattern includes a first pattern area, a middle pattern area and a second pattern area, the first pattern area and the second pattern area are the same in shape and size, and the lengths of the first pattern area and the second pattern area in the X-axis direction are greater than the length of the middle pattern area in the X-axis direction; one end of the middle pattern area is connected to the first pattern area, and the leading end of the middle pattern area is connected to the second pattern area.

[0013] In the method for preparing laser-induced graphene, in step S4, the duration of the pulse processing is 10.0 to 15.0 s, and the voltage applied to the patterned laser-induced graphene is 170 to 190 V.

[0014] In the method for preparing laser-induced graphene, the pulse processing step includes: applying a direct current pulse current to the surface of the patterned laser-induced graphene, and the power of the pulse current is 2.0 to 2.5 kW.

[0015] In the preparation method of laser induced graphene, in step S2, the power of the laser is 4.6-5.0 W, the frequency of the laser is 8-12 kHz, the duty cycle is 7-9%, the scanning speed of the laser is 900-1200 mm / s, the pulse width of the laser is 4-6 um, and the scanning line spacing of the laser is 20-30 um.

[0016] In the method for preparing laser-induced graphene, the substrate includes one of a glass substrate, a polyethersulfone plate, an acrylic plate and a polyetheretherketone plate.

[0017] In the method for preparing laser-induced graphene, the thickness of the substrate is 200-250 um.

[0018] The present invention also provides an improved laser induced graphene, and the improved laser induced graphene is prepared by the above-mentioned method for preparing laser induced graphene.

[0019] A technical solution in the present invention can have the following beneficial effects:

[0020] The preparation method of laser-induced graphene adopts a pulse current processing mode to adjust the laser-induced graphene to change the number of graphene layers, the induced strain in the lattice and the electronic band structure. The pulse current processing in step S4 takes a short time and can accurately control the crystal structure of the laser-induced graphene by adjusting its pulse parameters, such as voltage, duration and other conditions. The operation is more convenient, the controllability is higher, and the impact on the environment is minimal.

[0021] The method for preparing laser-induced graphene can significantly improve the conductivity of laser-induced graphene, while maintaining the original appearance of patterned laser-induced graphene and reducing cracks or deformation of laser-induced graphene. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a top view of patterned laser induced graphene in one embodiment of the present invention;

[0023] In the accompanying drawings: first pattern area 1, middle pattern area 2, second pattern area 3. DETAILED DESCRIPTION

[0024] The technical scheme of the present invention is further illustrated by specific embodiments below. In order to facilitate understanding of the present invention, the present invention is described more comprehensively below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0025] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0027] The present invention provides a method for preparing laser-induced graphene, comprising the following steps:

[0028] S1: cleaning and drying the substrate, cutting the polyimide film, and closely attaching the polyimide film to the surface of the substrate to form a processing area on the surface of the substrate;

[0029] S2: Using laser to pattern the surface of polyimide film to obtain patterned laser-induced graphene;

[0030] S3: placing the patterned laser-induced graphene in step S2 in a vacuum environment;

[0031] S4: Pulse processing the patterned laser induced graphene to obtain improved laser induced graphene.

[0032] In step S1, the substrate is first cleaned and dried to prevent impurities on the substrate from affecting the adhesion between the substrate and the polyimide film, thereby reducing the polyimide film from falling off the substrate. The polyimide film is tightly attached to the surface of the substrate. When the laser irradiates the polyimide film, the polyimide film is carbonized and reorganized, and a graphene structure is formed on the surface of the substrate.

[0033] In the patterning process of step S2, a laser is used to emit laser light, and the polyimide film is induced to form graphene by laser, so that laser-induced graphene with a regular pattern is formed on the surface of the substrate.

[0034] In step S3, the patterned laser-induced graphene is placed in a vacuum environment before step S4, which can avoid the influence of oxygen and other gases on the synthesis process, effectively reduce the risk of oxidation of graphene during the synthesis process, and thus improve the quality of graphene. In addition, the introduction of impurities can be reduced, ensuring that the synthesized graphene is purer and has better electrical and mechanical properties.

[0035] During the pulse processing in step S4, the patterned laser-induced graphene is heated instantaneously without being exposed to high temperature or uneven heating conditions for a long time, thereby minimizing damage to the crystal structure and preserving the structural integrity of the laser-induced graphene, ensuring the stability and reliability of the laser-induced graphene in subsequent applications.

[0036] During the patterning process of step S2, the laser pulse performs rapid heating and cooling within microseconds, which causes the disordered arrangement of internal atoms and amorphous characteristics; therefore, in the present invention, through the pulse processing process in step S4, but after the pulse processing, the crystallinity of graphene can be increased, realizing the transformation from amorphous to crystalline.

[0037] The polyimide film undergoes a transition from carbonization to graphitization during the patterning process. During this process, the CN bonds and C=O bonds of the polyimide are cleaved, releasing CO and CO 2 、N 2 The pulse processing in step S4 does not change the original macroscopic morphology or surface structure of the material, but only improves the internal crystal order and conductivity. In addition, because the processing will also produce instantaneous high temperature, gas will also be produced; the gas is released from the surface of the polyimide film, and more sponge-like structures are added while maintaining the integrity of the original sponge-like structure.

[0038] The preparation method of the laser-induced graphene adopts a pulse current processing mode to adjust the laser-induced graphene to change the number of graphene layers, the induced strain in the lattice, and the electronic band structure. The pulse current processing of step S4 takes a short time, and can accurately control the crystal structure of the laser-induced graphene by adjusting its pulse parameters, such as voltage, duration, etc., which is more convenient to operate, more controllable, and has minimal impact on the environment; the preparation method of the laser-induced graphene can significantly improve the conductivity of the laser-induced graphene, while maintaining the original appearance of the patterned laser-induced graphene, and reducing the occurrence of cracks or deformation of the laser-induced graphene.

[0039] Specifically, in step S1, the processing area is a square area, and the side length of the processing area is 1 to 20 mm.

[0040] The processing area is the area where the polyimide film is attached. In a specific embodiment of the present invention, the substrate and the polyimide film are the same size. The area of ​​the processing area is the area for subsequent patterning and pulse processing. When the side length of the processing area is greater than the above range, the area of ​​the processing area is too large to be placed in the cavity of the processing device.

[0041] Please refer to Figure 1 Specifically, the pattern formed by the patterning process includes a plurality of dumbbell-shaped patterns distributed at intervals, and the dumbbell-shaped pattern includes a first pattern area 1, a middle pattern area 2 and a second pattern area 3, the first pattern area 1 and the second pattern area 3 have the same shape and size, and the length of the first pattern area 1 and the second pattern area 3 in the X-axis direction is greater than the length of the middle pattern area 2 in the X-axis direction; one end of the middle pattern area 2 is connected to the first pattern area 1, and the collar end of the middle pattern area 2 is connected to the second pattern area 3.

[0042] When the pattern of the above shape is subjected to external force, the deformation of the middle part is more obvious, and it shows good flexibility in mechanical properties, which is very suitable for application in the field of flexible sensors.

[0043] Moreover, the middle pattern area 2 can concentrate heat to quickly complete structural optimization, so that the laser-induced graphene forms a stable hexagonal structure, significantly improving the conductivity of the laser-induced graphene, so that when the laser-induced graphene is used in the flexible sensor, the sensitivity of the flexible sensor is improved.

[0044] The lengths of the first pattern area 1 and the second pattern area 3 in the X-axis direction are greater than the length of the middle pattern area 2 in the X-axis direction. Therefore, compared with the middle pattern area 2, the heat obtained by the first pattern area 1 and the second pattern area 3 is more dispersed, and there may be a very small part of the position where the defect optimization is not fully achieved. However, in specific applications, the specific performance of the improved laser-induced graphene is mainly reflected by the middle pattern area 2, so the position where the first pattern area 1 and the second pattern area 3 fail to fully achieve defect optimization can be ignored.

[0045] Specifically, in step S4, the duration of the pulse processing is 10.0 to 15.0 s, and the voltage applied to the patterned laser-induced graphene is 170 to 190 V.

[0046] According to the Joule heat formula, when the resistance of the processed material remains unchanged, the greater the voltage, the more heat is generated, causing the patterned laser-induced graphene to reach a higher temperature instantly, repairing the defects in the patterned laser-induced graphene. Therefore, when the voltage is 170-190V, the repair process can be promoted, thereby improving the arrangement of atoms, completing the transformation of the crystal structure, and reducing the defect density. After eliminating the vacancies and other defects prepared by laser-induced graphene, the arrangement of carbon atoms becomes more orderly, forming a more stable crystal structure, which can provide more conduction channels and reduce the obstacles encountered by electrons during movement, thereby increasing the conductivity of the modified laser-induced graphene and reducing the resistance.

[0047] Specifically, the pulse processing step includes: applying a direct current pulse current to the surface of the patterned laser-induced graphene, and the power of the pulse current is 2.0 to 2.5 kW.

[0048] In a specific embodiment of the present invention, pulse processing uses direct current pulse current instead of alternating current. Since the pulse direction of alternating current changes periodically, it will cause uneven heating of the material and generate internal heat fluctuations, which is not conducive to the repair of the crystal structure.

[0049] DC pulses generate enough Joule heat through continuous high current and longer heating time than AC current, causing the carbon atoms inside the graphene to instantly increase in temperature and gain enough energy to rearrange themselves, transforming the pentagonal and heptagonal defects in laser-induced graphene into a more stable hexagonal lattice.

[0050] Specifically, in step S2, the power of the laser is 4.6-5.0 W, the frequency of the laser is 8-12 kHz, the duty cycle is 7-9%, the scanning speed of the laser is 900-1200 mm / s, the pulse width of the laser is 4-6 um, and the scanning line spacing of the laser is 20-30 um.

[0051] In a specific embodiment of the present invention, the above parameters are used for patterning processing.

[0052] When the laser power is higher than 5.0W, it may cause excessive ablation and destroy the graphene surface structure; when the laser power is higher than 4.6W, the graphene layer cannot be effectively formed.

[0053] When the frequency of the laser is too high, it can cause overheating of the graphene surface and increase the defect density, while too low a frequency may not be able to fully complete the laser-induced graphitization process.

[0054] The change in duty cycle affects the duration of the pulse. Other duty ratios can cause the material to overheat or even damage its microstructure. The scanning speed determines the time the material is heated. Too fast a speed will result in an incomplete laser-induced graphene layer, while too slow a speed will result in over-processing. The pulse width controls the duration of the laser action. A shorter pulse width can produce a finer pattern, while a longer pulse width will increase the heat accumulation of graphene and may destroy the predetermined patterned design. Too large a scan line spacing may result in uneven processing; too small a scan line spacing may also result in excessive heat accumulation.

[0055] Optionally, the substrate includes one of a glass substrate, a polyethersulfone board, an acrylic board and a polyetheretherketone board.

[0056] The substrate needs to be resistant to high temperatures and have good thermal stability. Using the above material as the substrate can avoid the problem of reduced quality and performance of laser-induced graphene due to chemical reactions of the substrate caused by high temperatures during patterning and pulse processing.

[0057] Optionally, the thickness of the substrate is 200-250 um. The thickness of the substrate affects the heat conduction efficiency. A thicker thickness may lead to uneven heat distribution and affect the repair of the crystal structure. A thinner thickness may not provide sufficient support.

[0058] The present invention also provides an improved laser induced graphene, and the improved laser induced graphene is prepared by the above-mentioned method for preparing laser induced graphene.

[0059] Example 1

[0060] A method for preparing laser-induced graphene comprises the following steps:

[0061] S1: Clean a 10×10 mm glass substrate with alcohol and deionized water, and dry it; cut a 10×10 mm 200 um polyimide film and attach it closely to the surface of the dried glass substrate;

[0062] S2: Use of CO 2The laser was used to pattern the surface of the substrate with the polyimide film to form multiple dumbbell-shaped patterns with intervals. The laser processing power was 4.6W, the frequency was 10kHz, the duty cycle was 8%, the scanning speed was 1200mm / s, the pulse width was 4um, and the scanning line spacing was 20um to obtain patterned laser-induced graphene.

[0063] S3: Place the patterned laser-induced graphene into a high-power pulse experimental chamber and provide a vacuum environment;

[0064] S4: applying a direct current pulse current to the surface of the patterned laser-induced graphene, the power of the pulse current is 2.0 kW, the applied voltage is 190 V, and the duration is 10.0 s, to obtain improved laser-induced graphene.

[0065] Example 2

[0066] The preparation steps of Example 2 are the same as those of Example 1, except that in step 4, the applied voltage is 170V.

[0067] Comparative Example 1

[0068] The preparation steps of Comparative Example 1 are the same as those of Example 1, except that in step 4, the applied voltage is 150V.

[0069] Comparative Example 2

[0070] A method for preparing laser-induced graphene comprises the following steps:

[0071] S1: A 10×10 mm glass substrate is cleaned with alcohol and deionized water in turn, and then dried; a 10×10 mm 200 um polyimide film is cut and closely attached to the surface of the dried glass substrate.

[0072] S2: Use of CO 2 The laser is used to pattern the side with the polyimide film to form multiple dumbbell-shaped patterns with intervals. The laser processing power is 4.6W, the frequency is 10kHz, the duty cycle is 8%, the scanning speed is 1200mm / s, the pulse width is 4um, and the scanning line spacing is 20um; laser induced graphene is obtained.

[0073] Compared with Example 1, Comparative Example 2 differs in that step S3 and step S4 are not performed.

[0074] Laser induced graphene is widely used as a material for flexible electronic devices, and resistance is one of the key indicators for measuring the conductive properties of a material, and the magnitude of the resistance is a response to its defects to a certain extent. Therefore, the resistance values ​​of the improved laser induced graphene obtained in Example 1, Example 2, Comparative Example 1, and the laser induced graphene obtained in Comparative Example 2 were measured, and the results are shown in Table 1.

[0075] Table 1 - Resistance value measurement results

[0076]

[0077] It can be seen from Example 1, Example 2 and Comparative Example 1 that when the voltage applied by the high-power DC pulse is changed and other conditions remain unchanged, the resistance value of the improved laser-induced graphene changes with the change of the voltage. When the voltage applied to the material is too small, the patterned laser-induced graphene can only be heated to a moderate temperature, and the carbon atoms cannot be completely rearranged to complete the transformation of the crystal structure.

[0078] It can be seen from Example 1 and Comparative Example 2 that the DC pulse can effectively reduce the resistance value of laser-induced graphene, thereby achieving higher conductivity, that is, it can realize the manufacture of flexible porous laser-induced patterned graphene with high crystallinity.

[0079] The technical principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the scope of protection of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific embodiments of the present invention without creative work, and these equivalent variations or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A method for preparing laser-induced graphene, characterized in that: The following steps are involved: S1: cleaning and drying the substrate, cutting the polyimide film, and closely attaching the polyimide film to the surface of the substrate to form a processing area on the surface of the substrate; S2: Using laser to pattern the surface of polyimide film to obtain patterned laser-induced graphene; S3: placing the patterned laser-induced graphene in step S2 in a vacuum environment; S4: Pulse processing the patterned laser induced graphene to obtain improved laser induced graphene.

2. The method for preparing laser-induced graphene according to claim 1, characterized in that: In the step S1, the processing area is a square area, and the side length of the processing area is 1 to 20 mm.

3. The method for preparing laser-induced graphene according to claim 1, characterized in that: The pattern formed by the patterning process includes a plurality of dumbbell-shaped patterns distributed at intervals, and the dumbbell-shaped pattern includes a first pattern area, a middle pattern area, and a second pattern area. The first pattern area and the second pattern area have the same shape and size, and the lengths of the first pattern area and the second pattern area in the X-axis direction are greater than the length of the middle pattern area in the X-axis direction; one end of the middle pattern area is connected to the first pattern area, and the leading end of the middle pattern area is connected to the second pattern area.

4. The method for preparing laser-induced graphene according to claim 1, characterized in that: In the step S4, the duration of the pulse processing is 10.0 to 15.0 s, and the voltage applied to the patterned laser-induced graphene is 170 to 190 V.

5. The method for preparing laser-induced graphene according to claim 1, characterized in that: The pulse processing step includes: applying a direct current pulse current to the surface of the patterned laser-induced graphene, wherein the power of the pulse current is 2.0 to 2.5 kW.

6. The method for preparing laser-induced graphene according to claim 1, characterized in that: In step S2, the power of the laser is 4.6-5.0 W, the frequency of the laser is 8-12 kHz, the duty cycle is 7-9%, the scanning speed of the laser is 900-1200 mm / s, the pulse width of the laser is 4-6 um, and the scanning line spacing of the laser is 20-30 um.

7. The method for preparing laser-induced graphene according to claim 1, characterized in that: The substrate includes one of a glass substrate, a polyethersulfone plate, an acrylic plate and a polyetheretherketone plate.

8. The method for preparing laser-induced graphene according to claim 1, characterized in that: The thickness of the substrate is 200-250um.

9. An improved laser induced graphene, characterized in that: The improved laser induced graphene is prepared by the method for preparing laser induced graphene according to any one of claims 1 to 8.

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