Preparation method of flexible wrinkled surface

Abstract

The invention discloses a preparation method of a flexible wrinkled surface. Comprising the following steps: mixing a PDMS matrix and a curing agent according to a specific mass ratio to form a prepolymer, and heating and curing after defoaming to obtain a flexible PDMS substrate; applying uniaxial or biaxial drawing force to the flexible PDMS substrate to deform the flexible PDMS substrate; keeping a stretching state, removing bubbles from newly prepared prepolymers with the same proportion, coating the prepolymers on a substrate, and heating and curing to form a double-layer flexible structure; the drawing force is released, and the PDMS film is compressed due to deformation recovery of the substrate to generate a wrinkle structure. Controllable adjustment of the size of the wrinkle structure can be achieved by adjusting and controlling the stretching direction and amplitude, the preparation material is single, the process is simple, cost is low, the period is short, controllability is high, the method is suitable for large-scale production, the problems that in the prior art, a flexible wrinkle surface preparation process is complex, cost is high, and large-scale production is difficult are solved, and the method is suitable for large-scale production. The method has a wide application prospect in the fields of flexible electronics, biomedical engineering, optical engineering and the like.

Description

Technical Field

[0001] This invention relates to the field of flexible material preparation technology, and specifically to a method for preparing a flexible wrinkled surface. Background Technology

[0002] Flexible pleated structures, due to their good ductility, special surface wettability and excellent optical properties, are widely used in the fabrication of products such as stretchable sensors, flexible circuits, bio-tissue engineering scaffolds, dynamically modulated surfaces and optical sensors. They have important application value in many fields such as flexible electronics and wearable device manufacturing, smart response material manufacturing, biomedical engineering, optical engineering and environmental and energy engineering.

[0003] Currently, the fabrication of flexible wrinkled surfaces typically relies on micro / nano fabrication processes such as physicochemical deposition, self-growth, and etching. However, these existing processes are complex, difficult to operate, and costly to produce, hindering the large-scale production of flexible wrinkled surfaces and severely limiting their application and industry development. Therefore, developing a rapid, efficient, low-cost method for fabricating flexible wrinkled surfaces suitable for mass production has become a pressing technical challenge in this field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a flexible wrinkled surface. This method is simple to operate, highly controllable, low in cost, and has a short cycle. It can achieve controllable preparation of wrinkled structures of different sizes and is suitable for large-scale production.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a flexible wrinkled surface includes the following steps:

[0007] Step S1: Mix the PDMS matrix and curing agent evenly to form a prepolymer, remove air bubbles from the prepolymer, and heat to cure to obtain a flexible PDMS substrate;

[0008] Step S2: Apply a uniaxial or biaxial tensile force to the flexible PDMS substrate to stretch the flexible PDMS substrate and cause it to deform in one or two directions.

[0009] Step S3: Maintain the unidirectional or bidirectional tensile force applied to the flexible PDMS substrate, that is, maintain the tensile state and tensile deformation of the flexible PDMS substrate, uniformly mix the PDMS matrix and curing agent to form a new prepolymer, remove the air bubbles in the new prepolymer and coat it on the PDMS substrate in the tensile state, and heat and cure to obtain a double-layer flexible structure composed of PDMS substrate and PDMS film.

[0010] Step S4: Release the uniaxial or biaxial tensile force applied to the PDMS substrate. The tensile deformation of the PDMS substrate disappears, and the PDMS film on the PDMS substrate is subjected to uniaxial or biaxial compression pressure and produces a wrinkled structure.

[0011] Furthermore, in step S1, the mass ratio of the PDMS matrix and curing agent used to uniformly mix and form the prepolymer is 10:1; the heating and curing temperature is 20~100℃, and the curing time is 0.5~24 h. This ratio and curing parameters ensure that the PDMS substrate has good flexibility and structural stability, providing a reliable basis for subsequent tensile deformation and the formation of a bilayer structure.

[0012] Furthermore, in step S2, when applying a uniaxial or biaxial tensile force to the flexible PDMS substrate, the uniaxial tensile amplitude is 5% to 50%. By adjusting the tensile amplitude, the final pleated structure size can be precisely controlled to meet the pleated structure requirements of different application scenarios.

[0013] Furthermore, in step S3, the mass ratio of the PDMS matrix and curing agent used to uniformly mix and form the new prepolymer is 10:1; the heating and curing temperature is 20~100℃, and the curing time is 0.5~24 h. Using the same material ratio and similar curing parameters as the PDMS substrate can ensure the bonding stability and property uniformity of the double-layer flexible structure, avoiding structural delamination or performance instability caused by material differences or different curing degrees.

[0014] Furthermore, in steps S1 and S3, the preferred method for removing air bubbles from the prepolymer is to place the prepolymer horizontally in a negative pressure environment for 0.5 hours. This method can efficiently remove air bubbles from the prepolymer, avoiding the impact of residual air bubbles on the structural integrity and surface smoothness of the PDMS substrate and PDMS film, thereby ensuring the formation quality of the wrinkled structure.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0016] 1. By adjusting the stretching direction (uniaxial or biaxial) and stretching amplitude (5%~50%) of the PDMS substrate, the present invention can precisely control the size of the wrinkled structure on the surface of the prepared flexible PDMS, realize the controllable preparation of wrinkled structures of different sizes, and meet diverse application needs.

[0017] 2. The materials required for preparing the flexible wrinkled surface in this invention are only PDMS matrix and curing agent. The materials are simple, and the prepared flexible wrinkled surface has uniform properties and strong structural stability.

[0018] 3. The preparation method proposed in this invention is simple, convenient and highly controllable. Compared with conventional micro-nano processing techniques such as physicochemical deposition, self-growth and etching, it does not require complex equipment and harsh processing conditions. It has low cost, short production cycle and can achieve large-scale production. It effectively solves the bottleneck problem of flexible wrinkled surface preparation in the prior art and has broad application prospects. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the preparation process of the flexible wrinkled surface of the present invention.

[0020] Figure 2 This is a schematic diagram of the flexible wrinkled surface structure of the present invention, wherein 1 is a PDMS substrate and 2 is a PDMS film with a wrinkled structure on the surface.

[0021] Figure 3 This is a schematic diagram of the surface morphology of the flexible PDMS sample with a wrinkled structure prepared in Example 1 of the present invention using SEM.

[0022] Figure 4 This is a schematic diagram of the appearance of the flexible PDMS sample with a pleated structure prepared in Example 1 of the present invention.

[0023] Figure 5 This is a schematic diagram of the surface morphology of the flexible PDMS sample with a wrinkled structure prepared in Example 2 of the present invention using SEM. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the embodiments. The described embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] For the purposes of this specification and the appended claims, unless otherwise stated, all expressions, percentages, or proportions, and other numerical values ​​used in this specification and the appended claims, are to be understood to be modified by the term "about" in all cases. Furthermore, all scopes disclosed herein include their endpoints and can be combined independently.

[0027] Example 1: This example provides a method for preparing a flexible wrinkled surface using uniaxial stretching. The specific steps are as follows:

[0028] Step 1: Mix dimethylsiloxane (PDMS matrix) and curing agent in a mass ratio of 10:1 to form a prepolymer. Pour the prepolymer into a round glass petri dish and place it in a negative pressure environment for horizontal static 0.5h to completely remove air bubbles from the prepolymer. Then, place the round glass petri dish containing the prepolymer horizontally in an oven for curing at a curing temperature of 60℃ for 3h. After curing, separate the PDMS from the round glass petri dish and cut it into squares of 10mm × 10mm to obtain a flexible PDMS substrate.

[0029] Step 2: Apply uniaxial tension to the above-mentioned flexible PDMS substrate using a stretching device, so that the 10mm×10mm flexible PDMS substrate is stretched by 10% in one direction, and maintain this stretched state.

[0030] Step 3: Maintaining the unidirectional tensile force and 10% stretch amplitude applied to the flexible PDMS substrate, mix dimethylsiloxane and curing agent in a mass ratio of 10:1 again to form a new prepolymer. Pour the new prepolymer onto the flexible PDMS substrate in a stretched state and place it in a negative pressure environment for 0.5 hours to remove air bubbles. Then, place the PDMS substrate covered with the new prepolymer in an oven for curing at a curing temperature of 60°C for 1 hour. After curing, a double-layer flexible structure consisting of a PDMS substrate and a PDMS film is obtained.

[0031] Step 4: Slowly release the uniaxial tensile force applied to the PDMS substrate. The PDMS substrate returns to its original state under its own elasticity, and its tensile deformation disappears. The PDMS film covering the substrate is subjected to uniaxial compressive pressure due to the loss of tensile support, thus forming a uniform wrinkled structure.

[0032] Example 2: This example provides another method for preparing a flexible wrinkled surface using uniaxial stretching, the specific steps of which are as follows:

[0033] Step 1: Mix dimethylsiloxane (PDMS matrix) and curing agent in a mass ratio of 10:1 to form a prepolymer. Pour the prepolymer into a round glass petri dish and place it in a negative pressure environment for 0.5 hours to remove air bubbles. Place the round glass petri dish containing the prepolymer horizontally in an oven for curing at 50°C for 6 hours. After curing, separate the PDMS from the petri dish and cut it into 10mm × 10mm square flexible PDMS substrates.

[0034] Step 2: Apply a uniaxial tensile force to the flexible PDMS substrate, so that the substrate is stretched by 30% in one direction and maintained in a stretched state.

[0035] Step 3: Keeping the unidirectional tensile force and 30% stretching amplitude constant, mix dimethylsiloxane and curing agent at a mass ratio of 10:1 to form a new prepolymer, pour it onto the stretched PDMS substrate, and let it stand horizontally under negative pressure for 0.5 hours to remove bubbles; then place it in an oven for curing at a curing temperature of 50℃ for 2 hours to obtain a double-layer flexible structure.

[0036] Step 4: Release the uniaxial tension, the PDMS substrate returns to its original shape, and the PDMS film is subjected to uniaxial compression to produce a wrinkled structure.

[0037] Example 3: Uniaxial stretching (low amplitude stretching)

[0038] This embodiment provides a method for preparing a flexible wrinkled surface for scenarios with low stretching range. The specific steps are as follows:

[0039] Step 1: Mix dimethylsiloxane (PDMS matrix) and curing agent at a mass ratio of 10:1 to form a prepolymer. Pour the prepolymer into a 20mm×20mm square glass mold and place it in a vacuum drying oven under negative pressure (vacuum degree -0.09MPa) for 0.5 hours to completely remove air bubbles. Then place the mold in an oven and cure it at a low temperature of 25℃ for 24 hours. After curing, peel the PDMS from the mold to obtain a flexible PDMS substrate with a size of 20mm×20mm.

[0040] Step 2: Apply uniaxial tension to the flexible PDMS substrate using a high-precision tensile testing machine, control the tensile rate to 1 mm / min, so that the substrate's tensile amplitude in one direction reaches 5% (i.e., the unidirectional dimension after stretching is 21 mm). After stretching to the target amplitude, keep the tension constant and maintain the tensile state.

[0041] Step 3: Maintaining the above 5% stretching amplitude and tensile force, prepare a new PDMS prepolymer at a mass ratio of 10:1. After stirring evenly, pour it onto the surface of the PDMS substrate in a stretched state, ensuring that the prepolymer evenly covers the substrate with a thickness controlled at 0.3 mm. Place it again in a vacuum drying oven under negative pressure for 0.5 h to remove bubbles, and then transfer it to an oven to cure at 25 °C for 24 h to form a tightly bonded PDMS substrate-film bilayer flexible structure.

[0042] Step 4: Slowly release the tensile force from the tensile testing machine at a rate of 0.5 mm / min. The PDMS substrate gradually returns to its original size, and its tensile deformation completely disappears. At this point, the PDMS film is subjected to uniform uniaxial compressive force due to substrate shrinkage, ultimately forming a fine and uniform wrinkled structure. The wrinkled structure prepared in this embodiment has a small size and is suitable for flexible sensing elements with high surface roughness requirements.

[0043] Example 4: Biaxial stretching (medium amplitude stretching)

[0044] This embodiment uses a biaxial stretching method to prepare a bidirectional pleated structure. The specific steps are as follows:

[0045] Step 1: Mix dimethylsiloxane and curing agent at a mass ratio of 10:1 to form a uniform prepolymer; pour the prepolymer into a 30mm diameter circular glass petri dish and place it in a negative pressure environment (vacuum degree -0.08MPa) for 0.5h to remove bubbles; place the petri dish in an oven and heat at 80℃ for 2h to cure; after curing, peel off the PDMS to obtain a 30mm diameter circular flexible PDMS substrate.

[0046] Step 2: Fix the circular PDMS substrate on the fixture of the biaxial stretching device, and apply tension in both the X and Y axes. Control the biaxial stretching rate to 2 mm / min, so that the substrate stretches by 20% in both vertical directions (i.e., the dimensions in both the X and Y axes are stretched to 36 mm). After reaching the target amplitude, maintain the tension to maintain the biaxial stretching state.

[0047] Step 3: Keeping the biaxially stretched state unchanged, prepare a new PDMS prepolymer at a mass ratio of 10:1. After stirring evenly, coat it uniformly onto the surface of the stretched PDMS substrate with a coating thickness of 0.5 mm. After standing in a negative pressure environment for 0.5 h to remove bubbles, transfer it to an oven and cure it at 80 °C for 2 h to obtain a double-layer flexible structure in the biaxially stretched state.

[0048] Step 4: Simultaneously and slowly release the tension in the X and Y axes at a rate of 1 mm / min. The PDMS substrate shrinks synchronously in both directions and returns to its original diameter of 30 mm. Under the action of biaxial contraction force, the PDMS film is subjected to biaxial compression, forming a biaxially interlaced wrinkled structure. This biaxial wrinkled structure has superior isotropy and is suitable for applications requiring biaxial stretchability, such as flexible circuits and dynamically modulated surfaces.

[0049] Example 5: Uniaxial stretching (high amplitude stretching + high temperature curing)

[0050] This embodiment employs a high tensile strength combined with a high-temperature curing process, and the specific steps are as follows:

[0051] Step 1: Mix dimethylsiloxane and curing agent at a mass ratio of 10:1, stir evenly to form a prepolymer, pour into a 15mm×15mm square glass mold, let stand under negative pressure for 0.5h to remove bubbles; put the mold into an oven and cure rapidly at 100℃ for 0.5h; after curing, cut into 15mm×15mm square flexible PDMS substrates.

[0052] Step 2: Apply a uniaxial tensile force to the PDMS substrate at a stretching rate of 3 mm / min, so that the unidirectional stretching amplitude reaches 50% (i.e., the unidirectional dimension after stretching is 22.5 mm), keep the tensile force constant, and maintain the stretched state.

[0053] Step 3: Maintaining a 50% stretching range, prepare a new 10:1 ratio PDMS prepolymer, uniformly coat it onto the stretched substrate with a thickness of 0.8 mm; after degassing under negative pressure for 0.5 h, place it in a 100℃ oven to cure for 0.5 h to form a double-layer flexible structure.

[0054] Step 4: Rapidly release the tension. The PDMS substrate quickly returns to its original size. The PDMS film is subjected to strong uniaxial compressive force, forming a wrinkled structure with large amplitude and wide spacing. The wrinkled structure prepared in this embodiment has more significant surface undulations and is suitable for applications such as bioengineering scaffolds and flexible sensors with large deformation.

[0055] As can be seen from the above embodiments 1-5, the present invention can achieve precise control of wrinkle structures of different sizes and shapes by flexibly adjusting the stretching direction (uniaxial / biaxial), stretching amplitude (5%-50%), curing temperature (25℃-100℃), and time (0.5h-24h). Among them, low stretching amplitude corresponds to fine wrinkles, and high stretching amplitude corresponds to wide-spacing wrinkles, meeting the diverse needs of different application scenarios.

[0056] The scope of protection of this invention is not limited to the above embodiments. For those skilled in the art, any adjustments and improvements to parameters such as curing temperature, curing time, stretching amplitude, and coating thickness in the steps, without departing from the technical principles of this invention, as well as process optimization methods such as using substrates of different sizes and different stirring rates, should be considered within the scope of protection of this invention.

Claims

1. A method for preparing a flexible wrinkled surface, characterized in that, Includes the following steps: Step S1: Mix the PDMS matrix and curing agent evenly to form a prepolymer, remove the air bubbles in the prepolymer, and heat to cure to obtain a flexible PDMS substrate; Step S2: Apply a uniaxial or biaxial tensile force to the flexible PDMS substrate to cause deformation in one or two directions. Step S3: Maintain the tension applied to the flexible PDMS substrate to maintain its tensile state and tensile deformation. Mix the PDMS matrix and curing agent evenly to form a new prepolymer. After removing the air bubbles in the new prepolymer, coat it onto the PDMS substrate in a tensile state. After heating and curing, a double-layer flexible structure composed of a PDMS substrate and a PDMS film is obtained. Step S4: Release the tension applied to the PDMS substrate. The tensile deformation of the PDMS substrate disappears, and the PDMS film on the PDMS substrate is subjected to uniaxial or biaxial compression and produces a wrinkled structure.

2. The method for preparing a flexible wrinkled surface according to claim 1, characterized in that, In step S1, the mass ratio of the PDMS matrix to the curing agent is 10:1; the heating curing temperature is 20~100℃, and the curing time is 0.5~24 h.

3. The method for preparing a flexible wrinkled surface according to claim 1, characterized in that, In step S2, the unidirectional stretching range is 5% to 50%.

4. The method for preparing a flexible wrinkled surface according to claim 1, characterized in that, In step S3, the mass ratio of the PDMS matrix to the curing agent is 10:1; the heating curing temperature is 20~100℃, and the curing time is 0.5~24 h.

5. The method for preparing a flexible wrinkled surface according to claim 1, characterized in that, In steps S1 and S3, the method for removing air bubbles from the prepolymer is to place the prepolymer in a negative pressure environment and let it stand horizontally for 0.5 hours.

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