Method for preparing a flexible electrode layer using laser-induced graphene and flexible electrode layer

Abstract

This invention discloses a method for preparing a flexible electrode layer using laser-induced graphene and the flexible electrode layer itself. The method includes: preparing a laser-induced graphene pattern on a polymer surface using a carbon dioxide laser; coating the polymer surface with the laser-induced graphene pattern with a flexible photosensitive resin; curing the resin with ultraviolet light; and peeling the cured flexible photosensitive resin along with the laser-induced graphene pattern from the polymer film to obtain a LIG@flexible photosensitive resin bilayer structure. This invention uses an ultraviolet light curing method to quickly and easily transfer the laser-induced graphene pattern onto a flexible photosensitive resin substrate, obtaining a flexible electrode layer with a LIG@flexible photosensitive resin layer structure that is bendable, patternable, and exhibits excellent conductivity.

Description

Technical Field

[0001] This invention belongs to the field of flexible electronic device fabrication, particularly the fabrication of flexible electrode layers for flexible pressure sensors. Specifically, it relates to a method for fabricating flexible electrode layers using laser-induced graphene, and the flexible electrode layer itself. Background Technology

[0002] Flexible electronic devices are a class of electronic products that are bendable, variable, and flexible. Compared to traditional rigid electronic devices, flexible electronic devices can be bonded to complex surfaces and have broad application prospects in wearable devices, health monitoring, human-computer interaction, and humanoid robots. However, the electrode layers of current flexible electronic devices are usually thinned metal films or metal films deposited through magnetron sputtering. Since the functional layers of flexible electronic devices are usually made of polymer materials, there is an inherent modulus mismatch between them and these metal films. Therefore, using metal films as electrode layers can lead to poor contact between the functional layers and the electrode layers, and the metal films are prone to detachment during repeated bending and deformation.

[0003] Laser-induced graphene (LIG) is a method discovered in the last decade or so for generating graphene on the surface of carbon-rich materials. Graphene structures can be induced by irradiating the surface of a carbon-containing material with a laser. The inventors of this application recognize that, due to the excellent electrical properties of graphene induced by this method and the ability to freely adjust its pattern using graphic design software, laser-induced graphene has the potential to pattern designed circuits. However, it has been further discovered that the high-carbon materials commonly used to generate LIG are not flexible, such as polyimide films (PI films). Based on this, the inventors of this application have continuously researched how to transfer the generated LIG onto a flexible substrate for use as an electrode layer in flexible electronic devices, and have thus proposed this application. Summary of the Invention

[0004] According to one embodiment of the present invention, the objective is to provide a method for preparing a flexible electrode layer using laser-induced graphene and a flexible electrode layer thereof. A laser-induced graphene pattern, such as a circuit pattern, is rapidly and easily transferred onto a flexible photosensitive resin substrate using an ultraviolet light curing method, thereby obtaining a flexible electrode layer with a LIG@flexible photosensitive resin layer structure, overcoming the limitations of laser-induced graphene applications in flexible electronic devices.

[0005] The above objective can be achieved through the following technical solutions:

[0006] According to one aspect of the present invention, a method for fabricating a flexible electrode layer using laser-induced graphene is provided, comprising:

[0007] Step 1) Prepare laser-induced graphene patterns on the polymer surface using a carbon dioxide laser;

[0008] Step 2) Coat the polymer surface with a flexible photosensitive resin with a laser-induced graphene pattern, cure it with ultraviolet light, and peel the cured flexible photosensitive resin together with the laser-induced graphene pattern off the polymer film to obtain a LIG@flexible photosensitive resin bilayer structure.

[0009] Optionally, it also includes: step 3) depositing metal nanoparticles on the LIG@flexible photosensitive resin bilayer structure to obtain a metal nanoparticle@LIG@flexible photosensitive resin trilayer structure.

[0010] Furthermore, metal nanoparticles are deposited on the LIG@flexible photosensitive resin bilayer structure using chemical deposition or electrochemical deposition methods.

[0011] Optionally, the flexible photosensitive resin is a polyacrylic photosensitive resin.

[0012] Optionally, during UV curing, the power of the UV light is 10-400W, and the curing time is 1-60s. Further, UV curing is performed in a 405nm UV curing chamber, with the sample 10-400mm away from the UV light source.

[0013] Optionally, the coating method for coating the polymer surface with the laser-induced graphene circuit pattern with the flexible photosensitive resin is spin coating or template drop application.

[0014] Furthermore, spin coating refers to using a spin coater to spin-coat uncured flexible photosensitive resin liquid onto the polymer surface. Even further, during spin coating, the spin coating speed is 10-5000 rpm, and the spin coating time is 1-60 seconds.

[0015] Furthermore, the template drop-addition method involves adhering a polymer with a laser-induced graphene circuit pattern to the bottom of a template, and then dripping uncured flexible photosensitive resin liquid onto the polymer surface until the flexible photosensitive resin liquid fills the template. Even further, the template thickness is 0.1-50 mm.

[0016] Optionally, in the template drop method, after the flexible photosensitive resin liquid fills the template, a vacuuming step is also included. Further, the vacuuming time is 1-60 minutes.

[0017] Optionally, the sheet resistance of the LIG@flexible photosensitive resin bilayer structure is 0.1-100kΩ / □.

[0018] Optionally, in the step of preparing laser-induced graphene patterns on the polymer surface using a carbon dioxide laser, the scanning pattern is preset based on CorelDRAW software, and then laser scanning is performed using a carbon dioxide laser to prepare the laser-induced graphene pattern.

[0019] Furthermore, the carbon dioxide laser has a laser wavelength of 10.6 μm, a laser power of 2 W-50 W, a scanning speed of 10-1000 mm / s, and a laser printing resolution of 10-1000 PPI.

[0020] Furthermore, the scanning pattern was preset as a circuit pattern using CorelDRAW software, and the resulting laser-induced graphene pattern was a laser-induced graphene circuit pattern.

[0021] Optionally, the LIG sheet resistance in the laser-induced graphene pattern on the polymer surface is 1-500 Ω / □.

[0022] Optionally, metal nanoparticles are deposited on the LIG@flexible photosensitive resin bilayer structure using a high-temperature chemical deposition method. Optionally, this includes: dissolving an active metal ion solution in ethanol to obtain a mixed solution; dropwise adding the mixed solution onto the surface of the LIG@flexible photosensitive resin bilayer structure and reacting it at a high temperature.

[0023] Furthermore, the volume ratio of the active metal ion solution to ethanol is 1:1 to 1:50.

[0024] Furthermore, the high temperature is 80-150℃, and the reaction time is 1-100s.

[0025] Optionally, the sheet resistance of the metal nanoparticle@LIG@flexible photosensitive resin three-layer structure is 0.01-100Ω / □.

[0026] According to another aspect of the present invention, a flexible electrode layer is provided by means of the method for preparing a flexible electrode layer using laser-induced graphene as described in the present invention.

[0027] Beneficial effects: According to one embodiment of the present invention, a flexible photosensitive resin substrate is used, which has good bendability and stretchability. The graphene induced by laser on polymers such as polyimide can be quickly and easily transferred to the flexible photosensitive resin substrate by using ultraviolet light curing. Moreover, by designing LIG patterns during laser-induced graphene, a corresponding pattern can be obtained on the flexible photosensitive resin substrate, realizing patternability (e.g., designing patterns for planar circuits to achieve circuit patterning). A bendable and highly conductive LIG@flexible photosensitive resin bilayer structure is prepared, which can be used as an electrode layer for flexible electronic devices.

[0028] Furthermore, in a preferred embodiment of the present invention, a flexible photosensitive resin is used as a flexible substrate, and LIG is used as an intermediate layer. Metal nanoparticles are deposited in the porous structure of LIG to improve its conductivity. Through the synergistic effect of LIG and metal nanoparticles, a flexible electrode layer with a three-layer structure of metal nanoparticles@LIG@flexible photosensitive resin that is flexible, patternable, and has excellent conductivity is obtained, which can be used as an electrode layer for flexible electronic devices.

[0029] Compared with the prior art, some embodiments of the present invention also have the following advantages:

[0030] 1) Using ultraviolet curing technology, LIG ​​patterns can be transferred onto a flexible photosensitive resin substrate. After the transfer, there is almost no residual graphene on the laser-induced graphene substrate, resulting in a LIG@flexible photosensitive resin bilayer structure that can be used as an electrode layer for flexible electronic devices.

[0031] 2) By designing LIG patterns, corresponding patterns can be obtained on flexible photosensitive resin substrates, realizing material patterning; in particular, patterns of planar circuits can be designed to realize circuit patterning, which can be used as flexible circuits for flexible electronic devices.

[0032] 3) After coating the polymer surface with LIG pattern using the template drop method, the flexible photosensitive resin is evacuated for a period of time under vacuum conditions to ensure that the flexible photosensitive resin liquid can penetrate into the LIG porous structure on the polymer.

[0033] 4) Due to the damage to the LIG structure after transfer, its resistance increased. By depositing metal nanoparticles in the porous structure of the double-layer LIG, the conductivity of the flexible electrode layer was improved.

[0034] 5) When depositing metal nanoparticles, the experimental parameters can be adjusted to deposit metal nanoparticles more uniformly in the LIG porous structure, which further improves the conductivity. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the entire process of preparing a flexible electrode layer using laser-induced graphene according to an embodiment of the present invention.

[0036] Figure 2 This is a scanning electron microscope image of laser-induced graphene generation on a PI film in one embodiment of the present invention;

[0037] Figure 3 This is a scanning electron microscope image of the LIG structure on the surface of the LIG@flexible photosensitive resin bilayer structure obtained in one embodiment of the present invention;

[0038] Figure 4This is an X-ray photoelectron spectrum of LIG on a PI film and LIG on a flexible photosensitive resin substrate in one embodiment of the present invention.

[0039] Figure 5 This is an X-ray diffraction analysis diagram of a three-layer structure of silver nanoparticles@LIG@flexible photosensitive resin in one embodiment of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below with reference to embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0041] One embodiment of the present invention provides a method for fabricating a flexible electrode layer using laser-induced graphene, comprising the following steps:

[0042] Step 1) Use a carbon dioxide (CO2) laser to induce the generation of laser-induced graphene (LIG) patterns with porous structures on the polymer.

[0043] The polymer refers to a carbon-containing material, such as polyimide, whose surface can be induced to form a graphene structure by laser irradiation. The graphene induced from this carbon-containing material exhibits excellent electrical properties. By designing patterns, such as circuit patterns, using graphic design software, laser-induced graphene patterns are fabricated, enabling the patterning of flexible electrode layers.

[0044] Furthermore, the carbon dioxide laser has a wavelength of 10.6 μm, a laser power of 2W-50W, a scanning speed of 10-1000 mm / s, and a laser printing resolution of 10-1000 PPI. When using a carbon dioxide laser to induce the preparation of graphene from carbon-containing materials, the laser scanning pattern, including graphics and dimensions, is pre-designed using CorelDRAW software; for example, a preset LIG circuit pattern for laser scanning. In this step, the LIG sheet resistance prepared on polymers such as polyimide is 1-500 Ω / □.

[0045] Step 2) Using ultraviolet (UV) curing technology, the LIG pattern is transferred onto a flexible photosensitive resin substrate to obtain a LIG@flexible photosensitive resin bilayer structure. The flexible photosensitive resin is a resin that can undergo a polymerization reaction under UV irradiation, thereby curing. Further, the flexible photosensitive resin is a polyacrylic acid-based photosensitive resin material. In addition, in this step, the LIG pattern can be completely transferred. Complete transfer means that the laser-induced graphene can be cleanly transferred to the surface of the flexible substrate, leaving almost no residual graphene on the laser-induced graphene substrate after the transfer.

[0046] Specifically, including:

[0047] Step 21) First, uniformly coat the uncured flexible photosensitive resin liquid onto the surface of a polymer such as polyimide with a LIG circuit pattern. Coating can be performed using either method (a) or method (b).

[0048] Method (a): Flexible photosensitive resin is spin-coated onto the surface of polymers such as polyimide using a spin coater. The spin coating speed can be 10-5000 rpm, and the spin coating time can be 1-60 s.

[0049] Method (b): A polymer such as polyimide is adhered to the bottom of a template, and then a flexible photosensitive resin liquid is dropped onto the surface of the polymer such as polyimide until the flexible photosensitive resin completely fills the template. The template thickness can be 0.1-50 mm.

[0050] Preferably, when coating using method (b), after the flexible photosensitive resin liquid has completely filled the template, the process further includes: evacuating the template under vacuum conditions for a period of time to ensure that the flexible photosensitive resin liquid can penetrate into the LIG porous structure on polymers such as polyimide. The vacuuming time is 1-60 minutes.

[0051] Step 22) Then, the sample is subjected to photocuring under ultraviolet light. The sample to be cured is placed in a 405nm ultraviolet curing chamber with an ultraviolet light power of 10-400W and the sample is 10-400mm away from the ultraviolet light source. The ultraviolet curing time is 1-60s.

[0052] Step 23) Finally, peel off the cured flexible photosensitive resin film along with the LIG pattern from the surface of the polymer such as polyimide, thus completing the transfer of the LIG pattern and obtaining the LIG@flexible photosensitive resin bilayer structure.

[0053] This step produces a LIG@flexible photosensitive resin bilayer structure with a sheet resistance of 0.1-100 kΩ / □.

[0054] In a preferred embodiment, the method further includes: step 3) depositing metal nanoparticles in the LIG porous structure of the LIG@flexible photosensitive resin bilayer structure to prepare a metal nanoparticle@LIG@flexible photosensitive resin trilayer structure. The metal nanoparticles can be, for example, Cu, Ag, Au, or other metal nanoparticles. The inventors of this application noted that the LIG structure was damaged (cracks appeared) after transfer, leading to increased resistance. This preferred embodiment improves the conductivity of the material by depositing metal nanoparticles in the LIG porous structure. Based on the synergistic effect of LIG and metal nanoparticles, a flexible, patternable, and highly conductive metal nanoparticle@LIG@flexible photosensitive resin trilayer structure is obtained, which can be used as an electrode layer for flexible electronic devices.

[0055] Furthermore, a chemical method was employed to deposit metal nanoparticles into the porous structure of LIG at high temperatures using a chemical reaction. For example, active metal ions were reduced to metal particles through chemical deposition at high temperatures, thus completing the deposition through a chemical reaction. Further, during the deposition of metal nanoparticles, the amount of metal ion active solution added, the heating temperature, and the heating time were controlled to uniformly deposit metal nanoparticles in the LIG porous structure, further improving conductivity. Specifically, this involved: adding a mixed solution of active metal ions to the surface of a LIG@flexible photosensitive resin bilayer structure; conducting a chemical reaction at 80-150℃ for 1-100 seconds; and generating metal nanoparticles on the surface of the LIG@flexible photosensitive resin bilayer structure after the reaction, thus preparing a metal nanoparticle@LIG@flexible photosensitive resin trilayer structure, effectively improving its conductivity. During deposition, the amount of metal ion active solution added was 1 μL / cm³. 2 -100μL / cm 2 Furthermore, the active metal ion mixed solution is obtained by dissolving an active metal ion solution in ethanol, with a volume ratio of active metal ion solution to ethanol of 1:1 to 1:50.

[0056] In this preferred embodiment, the sheet resistance of the prepared metal nanoparticle@LIG@flexible photosensitive resin three-layer structure is 0.01-100 Ω / □. It can be seen that by depositing metal nanoparticles and adjusting the parameters, the sheet resistance of the material can be reduced from 0.1-100 kΩ / □ to 0.01-100 Ω / □, significantly improving the material's conductivity.

[0057] The technical solution of the present invention will be further described below with reference to a specific embodiment. It should be noted that: in this embodiment, the preset scanning pattern is a square, but it is not limited to this. The preset scanning pattern and its size can be designed directly using the software as needed. For example, if the preset scanning pattern is a circuit, the circuit patterning in the flexible electrode layer can be realized.

[0058] Example 1

[0059] Figure 1 A schematic diagram illustrating the entire process of this embodiment is provided. (Reference) Figure 1 As shown, this embodiment provides a method for fabricating a flexible electrode layer using laser-induced graphene, comprising the following steps:

[0060] (1) Preparation of laser-induced graphene patterns. The parameters of the carbon dioxide laser were initially set as follows: laser power P = 7.5W, laser scanning rate ν = 200mm / s, and laser printing resolution 300PPI. The carbon dioxide laser was used to scan a 500μm thick polyimide (PI) film. The pre-defined scanning pattern was a square with dimensions of 10mm x 10mm, pre-set using CorelDRAW software. After scanning the PI film with the pre-defined pattern, laser-induced graphene with the pre-defined pattern was prepared. The scanning electron microscope (SEM) image is shown below. Figure 2 As shown.

[0061] (2) Adhere the PI film with LIG pattern printed on its surface to the bottom of the 10mm*10mm*2mm polytetrafluoroethylene template with double-sided tape.

[0062] The flexible photosensitive resin was then pretreated. In this embodiment, the flexible photosensitive resin used was Agilus 30, manufactured by Stratasys, abbreviated as A 30. The pretreatment involved placing the A 30 resin in a vacuum drying oven and repeatedly performing the degassing operation three times.

[0063] (3) Use a dropper to add A30 resin to the polytetrafluoroethylene template with a PI film attached to the bottom, and add until the resin liquid completely fills the template. Then place the filled template under vacuum conditions and evacuate for 30 minutes. The purpose of evacuation is to allow A30 resin to fully penetrate into the porous structure of LIG under negative pressure.

[0064] After vacuuming, the template is placed in a UV curing chamber, 100mm away from the UV light source. The UV light source power is adjusted to 100% to begin curing, which takes 50 seconds. After curing, the template is removed, and the cured flexible photosensitive resin substrate is peeled off. Then, the PI film is peeled off to obtain the LIG@flexible photosensitive resin bilayer structure. Its scanning electron microscope image is shown below. Figure 3 As shown, the X-ray photoelectron spectrum is as follows: Figure 4 As shown.

[0065] (4) The LIG@flexible photosensitive resin bilayer structure was placed on a heating stage. A mixture of active silver ion solution and ethanol (volume ratio 1:4) was then added dropwise using a pipette, controlling the amount of metal ion active solution added. After the solution had fully wetted the LIG on the surface of the bilayer structure, the heating stage was turned on and the temperature was set to 110℃ to allow the solution to react, depositing silver nanoparticles on the LIG to obtain an Ag nanoparticle@LIG@flexible photosensitive resin trilayer structure. Its X-ray diffraction pattern is shown below. Figure 5 As shown.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing description, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a flexible electrode layer using laser-induced graphene, characterized in that, include: Step 1) Prepare laser-induced graphene patterns on the polymer surface using a carbon dioxide laser; Step 2) Coat the polymer surface with a flexible photosensitive resin, which is a polyacrylic acid photosensitive resin, with a laser-induced graphene pattern. Perform ultraviolet curing in a 405nm ultraviolet curing chamber. The sample is 10-400mm away from the ultraviolet light source. During ultraviolet curing, the power of the ultraviolet light is 10-400W and the curing time is 1-60s. Peel off the cured flexible photosensitive resin together with the laser-induced graphene pattern from the polymer film to obtain a LIG@flexible photosensitive resin bilayer structure.

2. The method for preparing a flexible electrode layer using laser-induced graphene according to claim 1, characterized in that, Also includes: Step 3) Deposit metal nanoparticles on the LIG@flexible photosensitive resin bilayer structure using chemical deposition or electrochemical deposition methods to obtain a metal nanoparticle@LIG@flexible photosensitive resin trilayer structure.

3. The method for preparing a flexible electrode layer using laser-induced graphene according to claim 1 or 2, characterized in that, The coating method for coating flexible photosensitive resin onto the surface of a polymer with a laser-induced graphene pattern is spin coating. Spin coating refers to using a spin coater to spin-coat uncured flexible photosensitive resin liquid onto the polymer surface. During spin coating, the spin coating speed is 10-5000 rpm and the spin coating time is 1-60 s.

4. The method of claim 1 or 2, wherein the method is characterized by, The coating method for coating flexible photosensitive resin onto polymer surfaces with laser-induced graphene patterns is the template drop-addition method; The template drop method involves adhering a polymer with a laser-induced graphene pattern to the bottom of a template, then dropping uncured flexible photosensitive resin liquid onto the polymer surface until the flexible photosensitive resin liquid fills the template, and then evacuating the template for 1-60 minutes under vacuum conditions; the thickness of the template is 0.1-50 mm.

5. The method of claim 1 or 2, wherein the method is characterized by, The sheet resistance of the LIG@flexible photosensitive resin bilayer structure is 0.1-100kΩ / □.

6. The method of claim 1 or 2, wherein the method is characterized by, In the step of preparing laser-induced graphene patterns on polymer surfaces using a carbon dioxide laser, the scanning pattern is preset based on CorelDRAW software, and then laser scanning is performed using a carbon dioxide laser to prepare the laser-induced graphene pattern. The carbon dioxide laser has a wavelength of 10.6 μm, a laser power of 2 W-50 W, a scanning speed of 10-1000 mm / s, and a laser printing resolution of 10-1000 PPI. The sheet resistance of the laser-induced graphene in the laser-induced graphene pattern is 1-500 Ω / □. 7.The method of claim 6, wherein the laser-induced graphene is prepared by irradiating a mixture of water and an organic compound with a laser beam. The laser-induced graphene pattern was prepared by using CorelDRAW software to preset the scanning pattern as a circuit pattern.

8. The method for preparing a flexible electrode layer using laser-induced graphene according to claim 2, characterized in that, Metal nanoparticles were deposited on the surface of the LIG@flexible photosensitive resin bilayer structure using a high-temperature chemical deposition method. The process includes: dissolving an active metal ion solution in ethanol to obtain a mixed solution; dropping the mixed solution onto the surface of a LIG@ flexible photosensitive resin bilayer structure and reacting it at a high temperature; wherein the volume ratio of the active metal ion solution to ethanol is 1:1 to 1:50; the high temperature is 80-150℃ and the reaction time is 1-100s.

9. The method for preparing a flexible electrode layer using laser-induced graphene according to claim 2, characterized in that, The sheet resistance of the metal nanoparticle@LIG@flexible photosensitive resin three-layer structure is 0.01-100Ω / □.

10. A flexible electrode layer, characterized in that, The flexible electrode layer is prepared by the method described in any one of claims 1-9, which utilizes laser-induced graphene to prepare a flexible electrode layer.

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