Self-repairing packaging method for laser-induced graphene

Abstract

The invention relates to the technical field of graphene sensor packaging, and particularly discloses a self-repairing packaging method for laser-induced graphene, which comprises the following steps: sequentially carrying out oxygen plasma treatment and amination treatment on the surface of laser-induced graphene, and then sequentially spin-coating and curing an inner-layer solution, a middle-layer solution and an outer-layer solution to form a gradient structure; wherein the inner layer and the surface of the laser-induced graphene form a covalent bonding interface; the middle layer comprises a dynamic hydrogen bond network and a conductive filler so as to provide a self-repairing function and electrical stability; the outer layer contains a reinforcing filler to provide mechanical reinforcement and wear protection. Through chemical bonding and gradient structure design, the interface bonding strength, the environment barrier property, the mechanical durability and the self-repairing function of the packaging layer are synergistically improved, the problems of interface stripping, environment interference and mechanical damage of the laser-induced graphene sensor in practical application are effectively solved, and the service life of the device is remarkably prolonged.

Description

Technical Field

[0001] This application relates to the field of graphene sensor packaging technology, and in particular to a self-healing packaging method for laser-induced graphene. Background Technology

[0002] Laser-induced graphene (LIG) is a porous graphene material prepared on precursor materials such as polyimide using laser direct writing technology. It possesses excellent electrical conductivity, good mechanical flexibility, and customizable microstructure features, thus showing broad application potential in flexible electronic devices, wearable sensing devices, and environmental monitoring sensors. For example, LIG-based strain sensors can achieve high-precision deformation detection, while gas sensors exhibit high sensitivity to various volatile organic compounds.

[0003] However, LIG ​​sensors still face significant technical challenges in practical applications. On the one hand, their porous structure and surface chemical properties make them susceptible to contaminants such as moisture and dust in the environment, causing electrical performance drift and signal instability. On the other hand, under repeated bending, friction, or compression, the LIG microstructure is prone to damage or even fracture, leading to device performance degradation or failure. Therefore, achieving high-reliability packaging for LIG sensors to mitigate environmental interference and mechanical damage is crucial for their practical application.

[0004] Currently, most common encapsulation methods employ a single material system, such as polydimethylsiloxane (PDMS). While PDMS offers some flexibility and isolation, it still has significant limitations: the interfacial bonding between PDMS and LIG is weak, making it prone to peeling; the material itself lacks self-healing capabilities, leading to permanent failure once mechanical damage occurs; furthermore, traditional encapsulation layers struggle to balance environmental stability, mechanical strength, and signal transmission consistency during long-term use. Although some research has attempted to improve certain performance aspects by adding functional fillers (such as reinforcing particles or conductive agents), these efforts often suffer from problems such as decreased flexibility, poor interfacial compatibility, or difficulty in synergistic functional optimization due to inadequate material design. Summary of the Invention

[0005] Self-healing materials based on dynamic reversible chemical bonds (such as hydrogen bonds) and gradient functional structure design offer new ideas for high-performance packaging. Dynamic hydrogen bonds can undergo reversible breakage and recombination under certain conditions, enabling materials to self-repair after damage. Gradient composite structures can achieve targeted performance design in different regions of the encapsulation layer according to different functional requirements, such as strengthening interface bonding in the inner layer, achieving self-healing and electrical stability in the middle layer, and providing mechanical reinforcement and wear-resistant protection in the outer layer.

[0006] Against this backdrop, this application provides a self-healing encapsulation method for laser-induced graphene. Based on PDMS-Urea gradient encapsulation using a dynamic hydrogen bond network, combined with surface modification technology and multilayer spin coating process, a "sandwich" structure encapsulation film with a covalent bonding interface, a self-healing intermediate layer, and a reinforcing outer layer is constructed. This method is expected to not only improve the reliability and service life of LIG sensors in complex environments, but also provide a new solution for the functional integration and structural optimization of flexible electronic packaging technology.

[0007] This application provides a self-healing encapsulation method for laser-induced graphene, employing the following technical solution: A self-healing encapsulation method for laser-induced graphene includes the following steps: Oxygen plasma treatment: The laser-induced graphene surface is treated with oxygen plasma to generate carboxyl and hydroxyl groups on its surface; Surface amination treatment: An aminosilane solution is sprayed onto the laser-induced graphene surface after oxygen plasma treatment and then heat-treated to form an amination surface; Preparation of gradient encapsulation film: Inner layer, middle layer and outer layer solutions are sequentially spin-coated and cured on the aminated surface to obtain gradient encapsulation film; wherein, the inner layer forms a covalent bond interface with the laser-induced graphene surface; the middle layer contains a dynamic hydrogen bond network and conductive filler to provide self-healing function and electrical stability; the outer layer contains reinforcing filler to provide mechanical reinforcement and wear-resistant protection.

[0008] This application first introduces active groups on the LIG surface through chemical modification, which then form covalent bonds with the aminated inner layer, improving the problem of easy interface peeling in traditional physical encapsulation and enhancing the long-term stability of the encapsulation layer. Secondly, it employs a functional gradient design, integrating interface bonding, self-healing conductivity, and mechanical protection into a single layer. This achieves comprehensive performance that cannot be simultaneously possessed by a single material, enabling the encapsulated LIG sensor to resist external environmental corrosion and mechanical wear, and to self-repair after damage, significantly improving the reliability and lifespan of the device under complex operating conditions.

[0009] Furthermore, the inner layer is an amino-modified polydimethylsiloxane layer.

[0010] The amino groups at the terminal ends of the aminated polydimethylsiloxane molecule can undergo efficient amidation or condensation reactions with the carboxyl / hydroxyl groups generated on the LIG surface through plasma treatment, forming a strong covalent bond interface. This strong interfacial bonding can effectively suppress problems such as delamination and warping of the encapsulation layer caused by repeated bending of the device, providing a stable and reliable adhesion foundation for the entire gradient packaging structure.

[0011] Further, the spin-coating and curing of the inner layer solution includes: spin-coating the amino-dimethylsiloxane solution at a speed of 1500-2500 rpm and drying it at 70-90°C for 5-15 minutes.

[0012] A spin coating speed of 1500-2500 rpm ensures uniform spreading of the low-viscosity, high-flow-rate aminated polydimethylsiloxane solution, forming an ultra-thin and dense defect-free interface layer, avoiding the formation of voids that could affect encapsulation integrity. Medium-temperature drying conditions of 70-90℃ effectively remove solvent, promote molecular chain movement to optimize interfacial covalent bonding, and prevent damage to the LIG structure or existing chemical bonds that may occur due to excessively high temperatures.

[0013] Furthermore, the polymer matrix of the middle layer is polydimethylsiloxane-urea, wherein the mass percentage of the urea component is 15%-20%; the conductive filler is carbon black, which accounts for 0.3%-1.0% of the mass.

[0014] Using polydimethylsiloxane-urea (PDMS-Urea) with a urea content of 15%-20% as the matrix allows for the formation of a sufficiently dense and reversible dynamic hydrogen bond network, providing optimal self-healing efficiency for the encapsulation layer. The addition of 0.3%-1.0% carbon black filler enables the construction of a stable conductive network without significantly affecting the material's flexibility and self-healing ability. This network can compensate for resistance changes caused by sensor deformation or temperature variations, thereby improving the stability of the sensor's electrical signal after encapsulation.

[0015] Furthermore, the middle layer also contains a crosslinking agent, which is tetraethoxysilane.

[0016] The silanol groups produced after hydrolysis can react with groups on the PDMS-Urea chain and condense with each other, introducing appropriate covalent cross-linking points on the basis of dynamic hydrogen bond network. This network structure enhances the mechanical strength of the middle layer material on the one hand, preventing excessive plastic deformation during use; on the other hand, it does not sacrifice its self-healing ability, because the dynamic hydrogen bonds can still dominate the repair process under thermal activation, achieving a good balance between strength and self-healing.

[0017] Further, the spin-coating and curing of the intermediate layer solution includes: spin-coating a polydimethylsiloxane-urea solution containing conductive filler and crosslinking agent at a speed of 1200-1800 rpm and drying at 50-70°C for 10-20 minutes.

[0018] A moderate spin coating speed of 1200-1800 rpm is suitable for PDMS-Urea solutions with appropriate viscosity containing carbon black filler. This ensures uniform distribution of conductive filler and a moderate interlayer thickness, guaranteeing the continuity of the conductive pathway while providing sufficient space for molecular chain movement to facilitate hydrogen bond recombination. Low-temperature drying conditions of 50-70℃ facilitate slow solvent evaporation, preventing filler agglomeration or film cracking due to excessively rapid drying. Simultaneously, this temperature is sufficient to activate some hydrogen bond formation, initially stabilizing the interlayer structure.

[0019] Furthermore, the polymer matrix of the outer layer is polydimethylsiloxane-urea; the reinforcing filler is silica nanoparticles, which account for 15%-25% by mass.

[0020] Using PDMS-Urea as the matrix ensures good compatibility and adhesion between the outer and middle layers. Adding 15%-25% silica nanoparticles significantly improves the hardness, modulus, and wear resistance of the outermost surface of the encapsulation layer, effectively resisting mechanical damage such as friction and scratches. The high nanoparticle content also fills the free volume of the polymer, forming a dense physical barrier that greatly enhances the encapsulation system's ability to block environmental factors such as moisture and dust.

[0021] Further, the spin-coating and curing of the outer layer solution includes: spin-coating a polydimethylsiloxane-urea solution containing reinforcing fillers at a speed of 800-1200 rpm and drying at 70-90°C for 15-25 minutes.

[0022] A relatively low rotation speed of 800-1200 rpm is suitable for high-viscosity, high-filler-content outer layer slurries, which is conducive to forming a thicker protective outer layer and providing sufficient mechanical reinforcement. A higher drying temperature of 70-90℃ effectively removes solvents and promotes the bonding between polymer chains and silica filler interfaces. Simultaneously, the addition of inhibitors ensures that the curing reaction proceeds in an orderly manner at this temperature, avoiding surface defects and ultimately forming a robust, dense, and smooth wear-resistant protective layer.

[0023] Furthermore, after the gradient encapsulation film preparation step is completed, the step of thermally activating the gradient encapsulation film is also included. The thermal activation treatment is carried out at a temperature of 50-70°C for 3-10 minutes to promote the ordering of the dynamic hydrogen bond network.

[0024] Thermal activation provides a crucial "annealing" process for the entire encapsulation film. This gentle heat treatment promotes the movement of PDMS-Urea molecular chain segments, allowing the dynamic hydrogen bond network rapidly formed during spin coating to rearrange and optimize, resulting in more and more ordered hydrogen bond sites. This significantly improves the self-healing efficiency and mechanical robustness of the encapsulation film, enabling it to respond optimally to the thermal activation repair mechanism during subsequent use, thereby fully releasing the material's self-healing potential.

[0025] This application also provides a laser-induced graphene sensor, which is prepared using a self-healing encapsulation method for laser-induced graphene. The sensor includes a laser-induced graphene substrate and a gradient encapsulation film disposed on the surface of the laser-induced graphene substrate. The gradient encapsulation film includes an inner layer, a middle layer, and an outer layer. The inner layer forms a covalently bonded interface with the surface of the laser-induced graphene. The middle layer contains a dynamic hydrogen bond network and conductive fillers to provide self-healing functionality and electrical stability. The outer layer contains reinforcing fillers to provide mechanical reinforcement and wear-resistant protection.

[0026] In summary, this application includes the following beneficial technical effects: The PDMS-Urea gradient encapsulation film based on a dynamic hydrogen bond network provides excellent environmental adaptability and mechanical durability for laser-induced graphene sensors. The outer layer of this encapsulation film, doped with silica nanoparticles, forms a dense physical barrier that effectively blocks the intrusion of contaminants such as moisture and dust, ensuring signal stability in high-humidity environments. Simultaneously, the conductive carbon black in the middle layer works synergistically with the dynamic hydrogen bond network, enabling the sensor to maintain resistive stability over a wide temperature range, significantly superior to unencapsulated devices, thus guaranteeing detection accuracy in complex temperature environments.

[0027] The core advantage of this encapsulation system lies in its self-healing mechanism: the dynamic hydrogen bond network constructed in the middle layer PDMS-Urea material possesses reversible breakage and recombination characteristics. When the encapsulation layer is mechanically damaged, the hydrogen bonds in the damaged area break due to external force or thermal activation. Surrounding molecular chains diffuse towards the damaged interface and promote the formation of new hydrogen bonds, achieving spontaneous crack closure. This self-healing function effectively restores the mechanical properties and structural integrity of the material, improving the durability of the encapsulation film under friction, bending, and extrusion conditions, as well as the long-term reliability of the sensor.

[0028] The gradient functional layered design further achieves synergistic optimization of multiple performance characteristics: the inner layer of aminated PDMS is firmly bonded to the graphene substrate through covalent bonds, effectively improving the interface peeling problem; the middle layer has both self-healing and conductive functions, maintaining the signal stability of the sensor; and the outer layer of silica nanoparticles helps to enhance mechanical strength and wear resistance.

[0029] Furthermore, by controlling the spin coating speed, drying conditions, and material formulation in layers, the orderly construction and interface fusion of each functional layer were achieved, ensuring the overall quality and consistency of the encapsulation film. This enabled the laser-induced graphene sensor to still exhibit excellent comprehensive performance and service life under complex working conditions. Attached Figure Description

[0030] Figure 1 This is a flowchart of a self-healing encapsulation method for laser-induced graphene according to an embodiment of this application; Figure 2 These are the stability test results of the embodiments of this application under cyclic strain conditions; Figure 3 This is a diagram illustrating the self-healing process of the PDMS-Urea-based packaging module in an embodiment of this application. Figure 4 These are the test results of the resistance change rate of the sensor before, after and after the PDMS-Urea-based encapsulation film was damaged in the embodiments of this application. Detailed Implementation

[0031] The following is in conjunction with the appendix Figure 1-4 This application will be described in further detail.

[0032] This application discloses a self-healing encapsulation method for laser-induced graphene. (Refer to...) Figure 1 The self-healing encapsulation method for laser-induced graphene includes the following steps: Step 1, Oxygen Plasma Treatment: The prepared laser-induced graphene (LIG) substrate is placed in a plasma cleaner and treated for 30 seconds at a power of 100 W under an oxygen atmosphere. After treatment, active groups such as carboxyl and hydroxyl groups are introduced onto the surface of the laser-induced graphene.

[0033] Step 2, Surface Amination Treatment: Dissolve 3-aminopropyltriethoxysilane (APTES) in anhydrous ethanol to prepare a 2 vol% solution. The APTES ethanol solution is uniformly deposited onto the plasma-treated LIG surface using a spray coating method, and then annealed in an oven at 110°C for 10 min to allow the APTES to react with the active groups on the LIG surface, forming a stable amination interface.

[0034] Step 3, preparation of the gradient encapsulation film, includes the following steps: Step 3-1: Preparation, spin coating, and curing of the inner layer solution: Solution preparation: Take 80 wt% PDMS prepolymer (Sylgard 184, component A:B mass ratio = 10:1), 5 wt% APTES, and 15 wt% toluene solvent. Stir the mixture at 800 rpm for 2 hours at 25°C to allow it to react completely. Then, degas under a vacuum of -0.1 MPa for 30 minutes and filter using a 1 μm pore size nylon filter membrane to remove unreacted particles, obtaining the inner layer solution (aminated polydimethylsiloxane solution).

[0035] Spin coating and curing: The inner layer solution was spin-coated onto the amination-treated LIG surface at 2000 rpm, and then dried at 80°C for 10 min to form the inner layer encapsulation film. This layer ensures a strong interfacial bond through covalent bonding between the amino groups and the LIG surface.

[0036] Step 3-2: Preparation and spin coating of the intermediate layer solution, and curing: Solution preparation: Take 92.5 wt% polydimethylsiloxane-urea (PDMS-Urea) prepolymer (18% urea content), 0.5 wt% conductive carbon black (Vulcan XC-72), 5 wt% crosslinking agent tetraethoxysilane (TEOS), and 2 wt% solvent tetrahydrofuran (THF). Ball mill the mixture with zirconia grinding balls (0.5 mm diameter) for 24 hours to ensure sufficient dispersion of the carbon black. Then, sonicate at 40 kHz and 300 W for 1 hour to further break down the aggregates, obtaining the intermediate layer solution. The prepared intermediate layer solution must be stored away from light to prevent THF photolysis.

[0037] Spin coating and curing: The intermediate layer solution was spin-coated onto the cured inner layer surface at 1500 rpm and then dried at 60°C for 15 min to form the intermediate layer encapsulation film. The dynamic hydrogen bond network in this layer endows it with self-healing capabilities, while the doped carbon black provides electrical stability.

[0038] Step 3-3: Preparation, spin coating, and curing of the outer layer solution: Filler pretreatment and solution preparation: First, oleophilic silica nanoparticles (Aerosil R812) and silane coupling agent KH-570 were mixed at a mass ratio of 95:5 and reacted at 120℃ for 2 hours to obtain modified silica nanoparticles. Then, 78 wt% of polydimethylsiloxane-urea prepolymer, 20 wt% of modified silica nanoparticles, and 2 wt% of inhibitor ethyl cyanoacrylate were mixed. The mixture was dispersed at 10,000 rpm for 30 minutes using a high-speed shear emulsifier, and the final solution viscosity was controlled at 1200 cP (25℃) to obtain the outer layer solution.

[0039] Spin coating and curing: The outer layer solution was spin-coated onto the cured intermediate layer surface at 1000 rpm, and then dried at 80°C for 20 min to form the outer encapsulation film. The high content of silica nanoparticles in this layer significantly enhances the mechanical strength and wear resistance of the encapsulation film.

[0040] Step 4, Post-processing: After the three-layer structure is fully fabricated, the entire device is placed in a 60°C hot air oven for 5 minutes. This heat treatment process promotes the ordered recombination of the dynamic hydrogen bond network in the PDMS-Urea system, thereby activating and optimizing the self-healing performance of the encapsulation film.

[0041] A stability experiment was conducted on a laser-induced graphene sensor prepared by the above method under cyclic strain (5%) conditions, as follows: Figure 2As shown, the sensor's resistance change rate is very small under repeated bending. The self-healing process of the PDMS-Urea-based package is illustrated in the diagram below. Figure 3 As shown, the resistance change rate of the sensor before, after, and after the PDMS-Urea-based encapsulation film is as follows: Figure 4 As shown above, the results demonstrate that the self-healing function of the PDMS-Urea-based encapsulation mold effectively restores the mechanical properties and structural integrity of the material, ensuring the durability and long-term reliability of the sensor.

[0042] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A self-healing encapsulation method for laser-induced graphene, characterized by: The method comprises the following steps: oxygen plasma treatment: oxygen plasma treatment is performed on the surface of laser-induced graphene to generate carboxyl and hydroxyl groups on the surface thereof; surface amination treatment: after the oxygen plasma treatment, an aminosilane solution is sprayed on the surface of the laser-induced graphene and heat treatment is performed to form an aminated surface; preparation of a gradient encapsulation film: an inner layer, a middle layer and an outer layer solution are sequentially spin-coated and cured on the aminated surface to obtain a gradient encapsulation film; wherein the inner layer forms a covalent bonding interface with the surface of the laser-induced graphene; the middle layer comprises a dynamic hydrogen bond network and a conductive filler to provide self-healing function and electrical stability; and the outer layer comprises a reinforcing filler to provide mechanical reinforcement and wear-resistant protection.

2. The self-healing encapsulation method for laser-induced graphene according to claim 1, wherein: The inner layer is an aminated polydimethylsiloxane layer.

3. The self-healing encapsulation method for laser-induced graphene according to claim 2, wherein: The step of spin-coating and curing the inner layer solution comprises spin-coating the aminated polydimethylsiloxane solution at a rotation speed of 1500-2500 rpm and drying at 70-90℃ for 5-15 minutes.

4. The self-healing encapsulation method for laser-induced graphene according to claim 1, wherein: The polymer matrix of the middle layer is polydimethylsiloxane-urea, wherein the mass percentage of the urea component is 15%-20%; and the conductive filler is carbon black, with a mass percentage of 0.3%-1.0%.

5. The self-healing encapsulation method for laser-induced graphene according to claim 4, wherein: The middle layer further comprises a cross-linking agent, which is tetraethoxysilane.

6. The self-healing encapsulation method for laser-induced graphene according to claim 5, wherein: The step of spin-coating and curing the middle layer solution comprises spin-coating the polydimethylsiloxane-urea solution containing the conductive filler and the cross-linking agent at a rotation speed of 1200-1800 rpm and drying at 50-70℃ for 10-20 minutes.

7. The self-healing encapsulation method for laser-induced graphene according to claim 1, wherein: The polymer matrix of the outer layer is polydimethylsiloxane-urea; and the reinforcing filler is silicon dioxide nanoparticles, with a mass percentage of 15%-25%.

8. The self-healing encapsulation method for laser-induced graphene according to claim 7, wherein: The step of spin-coating and curing the outer layer solution comprises spin-coating the polydimethylsiloxane-urea solution containing the reinforcing filler at a rotation speed of 800-1200 rpm and drying at 70-90℃ for 15-25 minutes.

9. The self-healing encapsulation method for laser-induced graphene according to claim 1, wherein: After the preparation step of the gradient encapsulation film, a step of heat activation treatment of the gradient encapsulation film is further included, wherein the heat activation treatment is performed at a temperature of 50-70℃ for 3-10 minutes to promote the ordering of the dynamic hydrogen bond network.

10. A laser-induced graphene sensor, characterized by: A laser-induced graphene self-healing encapsulation method is provided, comprising a laser-induced graphene substrate and a gradient encapsulation film arranged on the surface of the laser-induced graphene substrate, wherein the gradient encapsulation film comprises an inner layer, a middle layer and an outer layer; the inner layer forms a covalent bonding interface with the surface of the laser-induced graphene; the middle layer comprises a dynamic hydrogen bond network and a conductive filler to provide self-healing function and electrical stability; and the outer layer comprises a reinforcing filler to provide mechanical reinforcement and wear-resistant protection.

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