Improved laser-induced graphene and preparation method thereof

Abstract

The present invention discloses an improved laser-induced graphene and a preparation method thereof, the steps comprising: cleaning and drying a substrate, cutting a polyimide film, and closely attaching the polyimide film to the surface of the substrate; patterning the surface of the polyimide film using a laser to obtain patterned laser-induced graphene; placing the patterned laser-induced graphene in a vacuum environment; and pulse-processing the patterned laser-induced graphene to obtain improved laser-induced graphene. The preparation method of the laser-induced graphene adopts a pulse current processing method 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 the crystal structure of the laser-induced graphene can be precisely controlled 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.

Description

Technical Field

[0001] The present 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 (LIG), a new two-dimensional material, boasts high conductivity, high flexibility, a porous structure, and the ability to be patterned without a mask. It is widely used in flexible electronic devices. However, during the LIG preparation process, laser irradiation can cause localized amorphous properties on the LIG surface. This amorphous structure reduces its conductivity, increasing the resistivity of electronic devices fabricated with it. This compromises the device's performance and limits its application in electronic devices such as sensors.

[0003] In the existing technology, the 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 propose 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 same.

[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: Clean and dry the substrate, cut the polyimide film, and adhere the polyimide film tightly to the surface of the substrate to form a processing area on the surface of the substrate;

[0008] S2: Using a laser to pattern the surface of a 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 is performed on 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 method for preparing laser-induced graphene, the pattern formed by the patterning process includes a plurality of spaced dumbbell-shaped patterns, the dumbbell-shaped pattern including a first pattern area, a middle pattern area, and a second pattern area, the first pattern area and the second pattern area having 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.

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

[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, wherein 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 to 5.0 W, the frequency of the laser is 8 to 12 kHz, the duty cycle is 7 to 9%, the scanning speed of the laser is 900 to 1200 mm / s, the pulse width of the laser is 4 to 6 μm, and the scanning line spacing of the laser is 20 to 30 μm.

[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 to 250 μm.

[0018] The present invention also provides an improved laser-induced graphene, which 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 laser-induced graphene preparation method uses pulsed current processing 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 pulsed current processing in step S4 is short and can precisely control the crystal structure of the laser-induced graphene by adjusting pulse parameters such as voltage and duration. This makes the process more convenient, more controllable, and has minimal environmental impact.

[0021] The method for preparing laser-induced graphene can significantly improve the electrical conductivity of laser-induced graphene while maintaining the original appearance of the patterned laser-induced graphene and reducing the occurrence of cracks or deformation in the 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 solution of the present invention will be further illustrated below by way of specific embodiments. To facilitate understanding of the present invention, the present invention will be described in more detail below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0025] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

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

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

[0028] S1: Clean and dry the substrate, cut the polyimide film, and adhere the polyimide film tightly to the surface of the substrate to form a processing area on the surface of the substrate;

[0029] S2: Using a laser to pattern the surface of a 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 is performed on 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 substrate surface. When the laser irradiates the polyimide film, the polyimide film is carbonized and reorganized, forming a graphene structure on the substrate surface.

[0033] During 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 a regular pattern of laser-induced graphene is formed on the surface of the substrate.

[0034] In step S3, placing the patterned laser-induced graphene in a vacuum environment before proceeding to step S4 prevents the effects of oxygen and other gases on the synthesis process, effectively reducing the risk of graphene oxidation during the synthesis process, thereby improving the quality of the graphene. Furthermore, this reduces the introduction of impurities, 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 the amorphous characteristics; therefore, in the present invention, through the pulse processing process of step S4, but after the pulse processing, the crystallinity of the graphene can be increased, realizing the transformation from amorphous to crystalline.

[0037] During the patterning process, the polyimide film undergoes a transition from carbonization to graphitization. During this process, the CN and C=O bonds of the polyimide are cleaved, releasing gases such as CO, CO2, and N2, which give the patterned laser-induced graphene a sponge-like structure. The pulsed processing in step S4 does not change the material's original macromorphology or surface structure; it only enhances its internal crystalline order and electrical conductivity. Furthermore, because the processing also involves transient high temperatures, gases are also generated; these gases are released from the surface of the polyimide film, adding more sponge-like structures while maintaining the integrity of the original sponge-like structure.

[0038] The laser-induced graphene preparation method uses a pulsed current processing method to adjust the laser-induced graphene to change the number of graphene layers, the induced strain in the crystal lattice, and the electronic band structure. The pulsed current processing in step S4 is short and can precisely control the crystal structure of the laser-induced graphene by adjusting its pulse parameters, such as voltage and duration. This makes the operation more convenient, more controllable, and has minimal impact on the environment. The laser-induced graphene preparation method 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 in 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 covered by the polyimide film. In a specific embodiment of the present invention, the substrate and the polyimide film are of equal size. The area of the processing area is the area within which patterning and pulse processing are subsequently performed. If the side length of the processing area exceeds this range, the processing area is too large to fit within 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 adopts the above shape, the deformation of the middle part is more obvious when subjected to external force, 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 and second pattern regions 1 and 3 along the X-axis are greater than those of the central pattern region 2. Therefore, compared to the central pattern region 2, the heat received by the first and second pattern regions 1 and 3 is more dispersed, potentially resulting in a small number of locations where defect optimization is not fully achieved. However, in practical applications, the specific performance of the improved laser-induced graphene is primarily reflected in the central pattern region 2, so the number of locations where defect optimization is not fully achieved in the first and second pattern regions 1 and 3 can be ignored.

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

[0046] According to the Joule heating formula, when the resistance of the processed material remains constant, the higher 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 is accelerated, thereby improving the atomic arrangement, completing the transformation of the crystal structure, and reducing the defect density. When the vacancies and other defects in the laser-induced graphene are eliminated, the arrangement of carbon atoms becomes more ordered, forming a more stable crystal structure, which provides more conduction channels and reduces 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, wherein the power of the pulse current is 2.0 to 2.5 kW.

[0048] In a specific embodiment of the present invention, pulse machining uses direct current pulses rather than alternating current. Since the pulse direction of alternating current changes periodically, it will cause uneven heating of the material, resulting in internal heat fluctuations, which is not conducive to the repair of the crystal structure.

[0049] The DC pulse generates 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 obtain enough energy to rearrange, so that the pentagonal and heptagonal defects in the laser-induced graphene are transformed into a more stable hexagonal lattice.

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

[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 will cause the graphene surface to overheat and increase the defect density, while too low a frequency may not be able to fully complete the laser-induced graphitization process.

[0054] Variations in the duty cycle affect the duration of the pulses; other duty cycles can cause the material to overheat and even damage its microstructure. The scanning speed determines how long the material is heated. Too fast a speed can result in an incomplete laser-induced graphene layer, while too slow a speed can lead to over-processing. The pulse width controls the duration of the laser's action. Shorter pulse widths produce finer patterns, while longer pulse widths increase heat accumulation in the graphene, potentially disrupting the intended patterning design. Excessively large scan line spacing can lead to uneven processing; too small a spacing can also result in excessive heat accumulation.

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

[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 chemical reactions of the substrate due to high temperatures during patterning and pulse processing, which leads to reduced quality and performance of laser-induced graphene.

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

[0058] The present invention also provides an improved laser-induced graphene, which 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 then dry it. Cut a 10×10 mm piece of 200 μm polyimide film and adhere it tightly to the surface of the dried glass substrate.

[0062] S2: Using a CO2 laser to pattern the surface of the polyimide film, multiple spaced dumbbell-shaped patterns were formed. 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 4μm, and the scanning line spacing was 20μm, thus obtaining 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 DC pulse current to the surface of the patterned laser-induced graphene, where 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, and then dried; a 10×10 mm piece of 200 μm polyimide film is cut and tightly attached to the surface of the dried glass substrate.

[0072] S2: Use a CO2 laser to pattern the side with a polyimide film to form multiple spaced dumbbell-shaped patterns. 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] Comparative Example 2 is compared with Example 1, except that step S3 and step S4 are not performed.

[0074] Laser-induced graphene is widely used as a material for flexible electronic devices. Resistance is one of the key indicators for measuring the conductive properties of a material, and the magnitude of the resistance is, to a certain extent, a reflection of its defects. 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. The results are shown in Table 1.

[0075] Table 1 - Resistance measurement results

[0076]

[0077] As shown in Examples 1 and 2, and Comparative Example 1, when the applied voltage of the high-power DC pulse is varied, while other conditions remain unchanged, the resistance of the modified LIG changes with the voltage. When the applied voltage is too low, the patterned LIG is heated only to a moderate temperature, failing to fully rearrange the carbon atoms and transform the crystal structure.

[0078] It can be seen from Example 1 and Comparative Example 2 that DC pulses can effectively reduce the resistance 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 principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and are not to be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will be able to devise other specific embodiments of the present invention without inventive effort, and such equivalent variations or substitutions are intended to be encompassed within the scope of the claims of this application.

Claims

1. A method for preparing laser-induced graphene, characterized in that: The following steps are involved: S1: Clean and dry the substrate, cut the polyimide film, and adhere the polyimide film tightly to the surface of the substrate to form a processing area on the surface of the substrate; S2: Using a laser to pattern the surface of a polyimide film to obtain patterned laser-induced graphene; The pattern formed by the patterning process includes a plurality of dumbbell-shaped patterns distributed at intervals, the dumbbell-shaped pattern including a first pattern area, a middle pattern area, and a second pattern area, the first pattern area and the second pattern area having 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; S3: placing the patterned laser-induced graphene in step S2 in a vacuum environment; S4: performing pulse processing on the patterned laser-induced graphene to obtain improved laser-induced graphene, wherein the pulse processing step includes: applying a DC 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.

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

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

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

6. The method for preparing laser-induced graphene according to claim 1, wherein: The thickness of the substrate is 200 to 250 μm.

7. 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 6.

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