Preparation method of shape memory reversible biomimetic adhesive material

Abstract

The present application relates to a kind of preparation method of shape memory reversible biomimetic adhesive material, belong to biomimetic material technical field.The method includes: with PVC gel preparation male die, copy PDMS female die;Shape memory polymer matrix, curing agent and toughening copolymer are mixed into epoxy resin precursor;By template method in PDMS female die solidification, obtain the adhesive material with microstructure array.The material can realize adhesive reversible switching by flexion mechanism under thermal stimulation: heating to above glass transition temperature, microstructure softening flexion and increase contact area, produce strong adhesion;After cooling, hardening keeps state;Again heating then shape recovery, realize low energy consumption detachment.The present application process is simple, and material has high adhesive strength, fast response, long life and good adaptability, can be widely applied in intelligent robot, precision manipulation and flexible electronic etc.Field.

Description

Technical Field

[0001] This invention relates to the field of biomimetic materials, and in particular to a method for preparing a shape memory reversible biomimetic adhesive material. Background Technology

[0002] In recent years, with the rapid development of intelligent robots, flexible electronics, and wearable devices, the demand for novel materials with controllable and reversible adhesive properties has been increasing. Traditional adhesive methods mainly rely on chemical adhesives or physical adsorption. The former, such as commonly used strong adhesives, is often difficult to remove after use and cannot be reused; the latter, such as suction cup structures, although capable of reversible adhesion to a certain extent, has high requirements for surface smoothness and cleanliness, and its performance deteriorates significantly in rough or complex environments. For example, CN112919129A discloses a biomimetic adhesive-desorption device based on a pneumatic push rod structure and polydimethylsiloxane adhesive material, which can achieve adhesion, handling, and release of industrial products such as printed circuit boards. However, its structure is bulky, has poor surface adaptability, and has a limited range of applications. Some studies have proposed reversible adhesive methods using electrostatic or magnetic principles. Although these methods can achieve on / off control through external fields, they often have poor selectivity for the adhesive surface and suffer from problems such as slow response speed, high energy consumption, and insufficient environmental adaptability. These existing technologies have not adequately addressed the balance between rapid response, low energy consumption maintenance, and long lifespan of reversible adhesive materials, and improvements are still needed, particularly in terms of reliability and adaptability under complex environmental conditions. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings in the above-mentioned background technology and provide a method for preparing a shape memory reversible biomimetic adhesive material. This material can achieve rapid and controllable switching of adhesive states through thermal stimulation, and has high adhesive strength, long cycle life and good environmental adaptability, which significantly improves the comprehensive performance and application range of reversible biomimetic adhesive materials.

[0004] The present invention adopts the following technical solution:

[0005] A method for preparing a shape memory reversible biomimetic adhesive material includes the following steps:

[0006] Step 1: Preparation of polyvinyl chloride base mold: PVC powder, 1,2-cyclohexanedicarboxylic acid diisononyl ester and tetrahydrofuran are mixed and stirred to form a PVC gel precursor. A silicon template is fixed on the bottom of a petri dish, the PVC gel precursor is poured and vacuum degassed, and after heating and curing, it is peeled off to obtain a PVC base mold.

[0007] Step 2: Preparation of polydimethylsiloxane concave mold: PDMS matrix material and curing crosslinking agent are mixed at a mass ratio of 10:1 to prepare PDMS precursor. After stirring and degassing, it is poured onto a PVC substrate convex mold. Vacuum treatment is performed to ensure that the precursor fully fills the microstructure gaps. After heating and curing, it is peeled off to form a PDMS concave mold.

[0008] Step 3, SMP material preparation: Preheat the shape memory polymer matrix material to reduce viscosity, add curing agent and toughening copolymer and stir until completely dissolved to form epoxy resin precursor;

[0009] Step 4: Preparation of biomimetic adhesive material: After degassing the epoxy resin precursor, it is poured onto a PDMS mold. Vacuum treatment is performed to ensure that the resin fully fills the micropores. After staged heating and curing, it is cooled and peeled off to obtain a shape memory polymer-based biomimetic adhesive material with a microstructure array.

[0010] As a further aspect of the present invention: in step one, the mass ratio of PVC powder, diisononyl 1,2-cyclohexanedicarboxylate and tetrahydrofuran is 1:(0.5-1.5):(5-15), and the curing condition is 48 hours at 60°C.

[0011] As a further aspect of the present invention: in step three, the shape memory polymer matrix material is bisphenol A diglycidyl ether, the curing agent is 4,4'-diaminodiphenylmethane, and the toughening copolymer is poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol). The mass ratio of shape memory polymer matrix material: curing agent: toughening copolymer is 100:(10-30):(5-20).

[0012] As a further aspect of the present invention: the stage heating and curing conditions in step four are 100°C for 2 hours and then 120°C for 4 hours.

[0013] As a further aspect of the present invention: the surface of the shape memory polymer-based biomimetic adhesive material has a microstructure array, and the adhesive state can be reversibly switched through thermal stimulation.

[0014] As a further aspect of the present invention: the unit structure of the microstructure array is any one of columnar, mushroom-shaped or wedge-shaped structure, with a height of 10-200μm, a diameter of 5-50μm and an aspect ratio of 1-10.

[0015] As a further aspect of the present invention: when the microstructure of the shape memory polymer-based biomimetic adhesive material is above the glass transition temperature, it buckles and collapses, forming the maximum contact area with the contact surface; when the microstructure is below the glass transition temperature, it hardens and fixes, achieving strong adhesion through intermolecular forces.

[0016] The beneficial effects of this invention are: the preparation method of this invention is simple and efficient, the material structure is stable and reliable, and the adhesive state switching response is fast; in addition, the microstructure design based on the buckling mechanism and the thermal response characteristics of SMP significantly improve the reversible adhesion performance and cycle life of the material, and broaden the application range of biomimetic adhesive materials in fields such as robot grasping and precision manipulation. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the preparation process according to an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of the microstructure of the SMP adhesive material prepared according to an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram illustrating the working principle of an embodiment of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings, but the present invention is not limited to the following embodiments.

[0021] A method for preparing a shape memory reversible biomimetic adhesive material, the method comprising the following steps:

[0022] Step one involves preparing the PVC substrate punch: (e.g.) Figure 1 As shown in Figure AD, the experimental supplies, including the silicon wafer mold, beaker, tweezers, and spatula used for preparing the shape memory polymer adhesive material, were first ultrasonically cleaned in batches in an ultrasonic cleaner and then dried in a forced-air drying oven for later use. Next, 1g of PVC powder, 1g of DINCH, and 15g of tetrahydrofuran were weighed and placed in an Erlenmeyer flask and stirred for 48 hours to form a PVC gel precursor. Then, a silicon template (concave mold) was fixed to the bottom of a petri dish, and an appropriate amount of the PVC gel precursor was poured on top. Vacuum degassing was performed for 10 minutes to allow the solution to fully penetrate the micropores of the silicon template under negative pressure. The dish was then placed in a heating oven at 60°C for 48 hours to allow the tetrahydrofuran organic solvent to gradually evaporate. As the organic solvent evaporates, the volume of the PVC gel shrinks. Meanwhile, DINCH not only plasticizes PVC but also has a certain oiliness, which can reduce the bonding force between the PVC gel and the silicon template when the PVC gel shrinks. Finally, the cured PVC gel was peeled off from the silicon template, and after cutting and cleaning, a PVC substrate convex mold was obtained.

[0023] Step two involves the preparation of the PDMS concave mold: (e.g.) Figure 1As shown in the figure, firstly, the PDMS matrix material and the curing crosslinking agent are prepared into a PDMS precursor at a mass ratio of 10:1. Secondly, the PDMS precursor is stirred at 800 rpm for 5 min, and then placed in a vacuum drying oven for degassing for 10 min. Then, the PVC substrate protrusion obtained in step one is fixed in a petri dish, and the degassed PDMS precursor is poured onto the PVC substrate protrusion. Vacuum is drawn in the vacuum drying oven to allow the PDMS precursor to fully enter the microstructure gaps of the PVC substrate protrusion. Then, the petri dish is placed in a heating oven and heated at 100°C for 40 min to form a silicone elastomer. Finally, the silicone elastomer is peeled off from the PVC substrate protrusion to form a PDMS concave mold.

[0024] Step three involves the preparation of SMP materials: such as... Figure 1 As shown in Figure i, taking bisphenol A diglycidyl ether-based SMP as an example, the SMP described in this patent is not limited to bisphenol A diglycidyl ether-based materials; all materials with shape memory properties are within the scope of protection of this patent. First, bisphenol A diglycidyl ether 1-16 is placed in a forced-air drying oven and preheated at 60°C for 2 hours to reduce the viscosity of the epoxy resin and increase its fluidity. Next, 100:20:10 bisphenol A diglycidyl ether is weighed and placed in a beaker. Then, it is preheated at 500 rpm and 100°C on a magnetic stirrer. Then, the appropriate mass ratio of curing agent 4,4'-diaminodiphenylmethane and toughening copolymer poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) are added and stirred continuously until the curing agent is completely dissolved to form an epoxy resin precursor.

[0025] Step four involves the preparation of epoxy resin-based shape memory biomimetic adhesive materials: such as... Figure 1 As shown in Figure 1, firstly, the epoxy resin precursor, which was stirred evenly in step three, was placed in a vacuum drying oven at 100°C and vacuumed for 10 minutes to remove bubbles. Secondly, the PDMS mold from step two was fixed on a culture dish, and the epoxy resin precursor was poured onto the PDMS mold. It was then placed in a vacuum drying oven again at 100°C and vacuumed for 10 minutes to ensure the epoxy resin fully penetrated the micropores inside the mold. Next, it was sealed and placed in a heating oven for curing at 100°C for 2 hours and then at 120°C for 4 hours. After curing, the culture dish was removed and slowly cooled to room temperature. Finally, the cured epoxy resin was peeled off from the PDMS mold, sheared, and cleaned to obtain the shape memory polymer-based biomimetic adhesive material. The structure was captured by SEM electron microscopy as shown in the figure. Figure 2 As shown.

[0026] The working principle of this invention is as follows: SMP achieves a reversible shape memory effect through thermodynamic control. Above the glass transition temperature (Tg), the molecular chains untangle and can be plastically deformed into a temporary shape by mechanical force; when cooled below Tg, the molecular chains rearrange and fix the deformation; when reheated above Tg, the material returns to its initial shape. Based on the above characteristics of epoxy resin-based SMP, this patent designs a gecko-inspired microstructure SMP adhesion system, the principle of which is as follows: Figure 2 As shown, when the temperature is below Tg, the material modulus is relatively large, making it difficult to form an effective contact area with the contact surface, such as... Figure 3 As shown in Figure a; when the temperature rises above Tg, the microstructure softens into a rubbery state. Under pre-stress, the microstructure buckles and collapses to adhere to the rough surface of the substrate, maximizing the contact area, as shown in Figure a. Figure 3 As shown in Figure b; after cooling below Tg, the microstructure hardens into a glassy state, forming a strong adhesion to the substrate through intermolecular forces (adhesion mode), as shown in Figure b. Figure 3 As shown in Figure c; during separation, heating restores the microstructure to its initial shape, drastically reducing the contact area and achieving low-energy separation (separation mode), as shown in Figure c. Figure 3 As shown in d. This dynamic control mechanism not only replicates the passive adaptability of gecko adhesion, but also endows the material with environmental responsiveness through temperature-driven active deformation, providing a new strategy for scenarios such as intelligent grasping and reversible packaging.

[0027] This invention possesses advantages such as excellent adhesion performance and rapid, reversible state switching. It integrates a buckling-collapse microstructure based on shape memory polymers to achieve efficient control of adhesion forces on material surfaces. A thermal stimulation response mechanism enables intelligent switching and recovery of the adhesion state. This invention features simple stimulation methods (requiring only a heat source), reversible adhesion on various surfaces (smooth / rough), high adhesion strength, long cycle life, and environmental adaptability.

[0028] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and can have many variations, such as changes in microstructure shape, size, type and proportion of shape memory materials, etc. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A method for preparing a shape memory reversible biomimetic adhesive material, characterized in that, Includes the following steps: Step 1: Preparation of polyvinyl chloride base mold: PVC powder, 1,2-cyclohexanedicarboxylic acid diisononyl ester and tetrahydrofuran are mixed and stirred to form a PVC gel precursor. A silicon template is fixed on the bottom of a petri dish, the PVC gel precursor is poured and vacuum degassed, and after heating and curing, it is peeled off to obtain a PVC base mold. Step 2: Preparation of polydimethylsiloxane concave mold: PDMS matrix material and curing crosslinking agent are mixed at a mass ratio of 10:1 to prepare PDMS precursor. After stirring and degassing, it is poured onto a PVC substrate convex mold. Vacuum treatment is performed to ensure that the precursor fully fills the microstructure gaps. After heating and curing, it is peeled off to form a PDMS concave mold. Step 3, SMP material preparation: Preheat the shape memory polymer matrix material to reduce viscosity, add curing agent and toughening copolymer and stir until completely dissolved to form epoxy resin precursor; Step 4: Preparation of biomimetic adhesive material: After degassing the epoxy resin precursor, it is poured onto a PDMS mold. Vacuum treatment is performed to fully fill the micropores with resin. After staged heating and curing, it is cooled and peeled off to obtain a shape memory polymer-based biomimetic adhesive material with a microstructure array. In step three, the shape memory polymer matrix material is bisphenol A diglycidyl ether, the curing agent is 4,4'-diaminodiphenylmethane, and the toughening copolymer is poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol). The mass ratio of shape memory polymer matrix material: curing agent: toughening copolymer is 100:(10-30):(5-20).

2. The preparation method according to claim 1, characterized in that: In step one, the mass ratio of PVC powder, DINCH and tetrahydrofuran is 1:(0.5-1.5):(5-15), and the curing condition is 48 hours at 60°C.

3. The preparation method according to claim 1, characterized in that: In step four, the curing conditions are: curing at 100°C for 2 hours, followed by curing at 120°C for 4 hours.

4. The preparation method according to claim 1, characterized in that: The shape memory polymer-based biomimetic adhesive material has a microstructure array on its surface, which can achieve reversible switching of the adhesive state through thermal stimulation.

5. The preparation method according to claim 4, characterized in that: The unit structure of the microstructure array is any one of columnar, mushroom-shaped or wedge-shaped structures, with a height of 10-200μm, a diameter of 5-50μm and an aspect ratio of 1-10.

6. The preparation method according to claim 1, characterized in that: The shape memory polymer-based biomimetic adhesive material exhibits microstructure buckling and collapsing above the glass transition temperature, forming the maximum contact area with the contact surface; below the glass transition temperature, the microstructure hardens and becomes fixed, achieving strong adhesion through intermolecular forces.

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