CN103204459B - The formation method of flexible substrate film surface micro-structure - Google Patents

Abstract

The present invention proposes a kind of formation method of flexible substrate film surface micro-structure, comprising: curve plotting figure also prepares photo etched mask; Utilize photo etched mask, photoetching quartz glass; At patterned quartz glass top casting flexible substrates performed polymer, then solidification obtains patterned flexible substrates and peels off; And in patterned flexible substrates metal-coated membrane.The present invention is in flexible base material surface forming curves structure, plated film in substrate again, because variations in temperature produces thermal stress, curvilinear structures guides the stress distribution in film, can by the curvilinear structures of design different curvature, spacing and shape, control region and the amplitude of the generation of fold flexing, the method is simple to operate, is easy to realize.

Description

Formation method of surface microstructure of flexible substrate film

technical field

The invention belongs to the technical field of micro-nano manufacturing, and in particular relates to a method for forming a surface microstructure of a flexible substrate film.

Background technique

With the gradual popularization and application of flexible circuits and flexible devices, the design and optimization of flexible structures is particularly important. Flexible sensors, exciters and flexible electronic circuits are currently emerging as an important subject area. Utilizing the surface buckling of flexible substrate membrane structures to realize the function of flexible structures in service is a method that has been widely used. NedBowden et al. plated a gold film on the surface of a flexible substrate PDMS, and the temperature change generated during the coating process caused the film substrate system to spontaneously buckle and wrinkle. Subsequently, many scholars have studied the buckling of this thin film substrate system due to mismatch strain from theory and experiment. Essentially, the buckling occurs due to the large difference in elastic constants between the film and the flexible substrate. Generally, the elastic modulus of the film is two or three orders of magnitude higher than that of the substrate. Experimentally, a thicker film is formed on the surface of thermally expanded PDMS after oxygen plasma modification treatment. After cooling, the mismatch strain generated by the shrinkage of PDMS forms wrinkles on the surface of the film. EdwinP et al. (EdwinP et al., Softmatter, 2 (2006) 324–328) changed the modulus of a film on the surface by UV-ozone aging treatment on PDMS, and then placed it in ethanol vapor to cause buckling and wrinkles on the PDMS surface. CunjiangYu et al. (CunjiangYu et al., APPLIEDPHYSICSLETTERS, 96 (2010) 041111) released PDMS to buckle the surface after UV oxidation treatment of prestretched PDMS, and controlled the wavelength and amplitude of buckling by changing the amplitude of prestretching. The periodic structure formed on this surface can be used as an optical grating. None of the above experimental methods can achieve selective wrinkle buckling on the PDMS surface. For the design of flexible devices, it is particularly important to selectively design microstructures on the surface.

Contents of the invention

In view of the defects in the prior art, the purpose of the present invention is to propose a method for forming the surface microstructure of the flexible substrate film, which can selectively generate folds and buckles on the surface of the flexible substrate film, and is simple to operate and easy to implement.

The method for forming the surface microstructure of a flexible substrate film according to an embodiment of the present invention includes the following steps: S1: draw a curve pattern and prepare a photolithography mask; S2: use the photolithography mask to photolithography quartz glass; S3: Casting the flexible substrate prepolymer on the patterned quartz glass, then curing to obtain the patterned flexible substrate and peeling off; and S4: Coating a metal film on the patterned flexible substrate.

Preferably, the flexible substrate is one or a combination of polydimethylsiloxane, polymethyl methacrylate or polyimide.

Preferably, the metal film is one or a combination of aluminum, copper or gold.

Preferably, the curve radius of the curve pattern is 150-450 microns, and the curve interval is 50-450 microns.

Preferably, the curve pattern is a plurality of parallel wavy lines.

Preferably, the order of the concavo-convex of two adjacent wavy lines is the same or opposite.

Preferably, the metal film has a thickness of 100-300 nm.

The method for forming the surface microstructure of the flexible substrate film of the present invention forms a curved structure on the surface of the flexible substrate material, and then coats a film on the substrate. Thermal stress is generated due to temperature changes, and the curved structure guides the stress distribution in the film, which can be designed by designing different curvatures, The curved structure of spacing and shape controls the area and magnitude of fold buckling. This method is simple to operate and easy to implement.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and comprehensible from the description of the embodiments in conjunction with the following drawings, wherein:

Fig. 1 is the flowchart of the method for forming the surface microstructure of the flexible substrate film according to the embodiment of the present invention;

Fig. 2 is the curve patterns of different arc radii, curve spacing and shape drawn by CAD;

Fig. 3 is the curve pattern on the imaged quartz glass;

Figure 4 is an SEM scan of the wrinkled buckling of the PDMS substrate aluminum film system;

Figure 5 is the wrinkled and buckled morphology of the base film observed under an ultra-depth-of-field optical microscope;

Fig. 6 is a stress distribution trend diagram guided by curve graphics on the substrate simulated by Abaqus software.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

Fig. 1 is the flow chart of the forming method of the surface microstructure of the flexible substrate film of the embodiment of the present invention, Fig. 2 is the curve patterns of different arc radii, curve pitches and shapes drawn by CAD, Fig. 3 is the graph on the quartz glass Curve pattern, Figure 4 is the SEM scanning image of the fold and buckle of the flexible substrate aluminum film system, Figure 5 is the fold and buckle morphology of the substrate film observed under the ultra-depth optical microscope, and Figure 6 is the stress distribution trend guided by the curve pattern on the substrate simulated by Abaqus software .

As shown in Figure 1, the method for forming the surface microstructure of the flexible substrate film of the present invention comprises the following steps:

S1: Draw a curve graph and prepare a photolithography mask.

Generally, the curve radius of the curve pattern is 150-450 microns, and the curve interval is 50-450 microns. In one embodiment of the present invention, the curved pattern is a plurality of parallel wavy lines. The order of the ups and downs of two adjacent wavy lines is the same or opposite.

S2: Using a photolithography mask, photolithography of quartz glass.

S3: casting the flexible substrate prepolymer on the patterned quartz glass, and then curing to obtain the patterned flexible substrate and peeling off.

Specifically, the flexible substrate is one or a combination of polydimethylsiloxane, polymethyl methacrylate or polyimide.

S4: Coating a metal film on the patterned flexible substrate.

Specifically, the metal film is a combination of one or more of aluminum, copper or gold, and the thickness of the metal film is 100-300 nm.

In order for those skilled in the art to better understand the present invention, FIG. 1 will be described in detail below in conjunction with FIG. 2 to FIG. 6 .

First design different curve structures, and use CAD software to draw curve graphics. The embodiment of the present invention takes the arc curve as an example. The radius of the arc can be 200um, 300um, 400um, etc., and the distance between the curves can be 100um, 200um, 400um, etc. The drawn curve pattern is shown in Figure 2. In addition to arcuate curves, other types of curves are equally possible. Then make the curve pattern on the film, the line width of the curve is 20um, and the film is used as a photolithography mask.

Next, spray the photoresist on the quartz glass with a thickness of 1 mm at a speed of 3000 r/min for 1 min. Pre-bake before exposure, and bake at 100°C for 5 minutes. Then carry out ultraviolet exposure to the baked photoresist, and use the previously obtained film film as a mask and put it on the ultraviolet exposure machine for exposure. The exposure time is 30s. Where the photoresist is exposed is the area without the curved pattern. Baking is carried out after exposure, and the duration is 1min. Developing, the developing solution is 5‰ NaOH solution, and the developing time is 10s. After developing, the photoresist curve pattern appears on the quartz glass, and then the quartz glass sheet is rinsed, and the quartz glass is baked. The quartz glass is corroded by dilute hydrofluoric acid solution, the curve pattern is transferred to the quartz glass, and then the quartz glass is cleaned with acetone to remove the residual photoresist to obtain the quartz template with the curve pattern. The resulting curved pattern on the patterned quartz glass is shown in Figure 3.

Then mix the polydimethylsiloxane (polydimethylsiloxane, PDMS) prepolymer and the curing agent according to the proportion of 10:1, stir evenly and put the glue in the centrifuge. After the bubbles in the mixture are basically thrown out, the PDMS The mixture is cast directly on the quartz glass. Place in an oven, heat at 70°C for 1 hour to cure, peel off the cured PDMS from the quartz glass, copy the curve pattern on the PDMS, and obtain a patterned PDMS substrate.

Finally, the method of thermal evaporation is used to coat the aluminum film on the PDMS substrate. In the embodiment of the present invention, the thickness of the aluminum film is 200nm. The PDMS surface obtained under the SEM after the aluminum film is coated is shown in Figure 4. Further zooming in can clearly see the buckling of the formed folds as shown in Figure 5. The thickness of the aluminum film is controllable with the length of the coating, and the thickness of the aluminum film can be adjusted in the range of 100-300nm according to the needs. With the different thickness of the coating, the wavelength and amplitude of the buckling of the folds are also different. In addition, the initial CAD curve design process Curvilinear structures with different curvatures and shapes can control the magnitude and area of membrane wrinkle buckling.

We used computer simulations to simulate the influence of the curved structure of the surface of the flexible substrate on the stress distribution. The finite element software Abaqus is used to simulate, and the compressive stress is applied to the model to simulate the compressive stress in the PDMS substrate. In order to simplify the model in Figure 6, it is a rotationally symmetrical model, and there is a concentric groove on the circular base. Figure 6(a) shows the circumferential stress distribution along the radial direction. It can be seen from the stress cloud diagram that the compressive stress decreases close to 0 on the concave side of the curve close to the groove, and the compressive stress increases on the convex side of the curve close to the groove, and the compressive stress is the largest on the convex side of the curve. On the concave side, compressive stress can inhibit the occurrence of buckling folds along the radial direction. From Figure 4 and Figure 5 (especially the left figure), it can be seen that the fold buckling occurs on the convex side of the curve, while no fold buckling occurs on the concave side.

The method for forming the surface microstructure of the flexible substrate film of the present invention forms a curved structure on the surface of the flexible substrate material, and then coats a film on the substrate. Thermal stress is generated due to temperature changes, and the curved structure guides the stress distribution in the film, which can be designed by designing different curvatures, The curved structure of spacing and shape controls the area and magnitude of fold buckling. This method is simple to operate and easy to implement.

Any process or method descriptions in flowcharts or otherwise described herein may be understood to represent modules, segments or portions of code comprising one or more executable instructions for implementing specific logical functions or steps of the process , and the scope of preferred embodiments of the invention includes alternative implementations in which functions may be performed out of the order shown or discussed, including substantially concurrently or in reverse order depending on the functions involved, which shall It is understood by those skilled in the art to which the embodiments of the present invention pertain.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be construed as limitations to the present invention. Variations, modifications, substitutions, and modifications to the above-described embodiments are possible within the scope of the present invention.

Claims (7)

1. A method for forming a flexible base film surface microstructure, characterized in that, comprising the steps: S1: Draw a curve graph and prepare a photolithography mask; S2: Using the photolithography mask, photolithography of quartz glass; S3: casting a flexible substrate prepolymer on patterned quartz glass, then curing to obtain a patterned flexible substrate and peeling off; and S4: Coating a metal film on the patterned flexible substrate. 2. the forming method of flexible substrate film surface microstructure according to claim 1, is characterized in that, described flexible substrate is one in polydimethylsiloxane, polymethyl methacrylate or polyimide one or more combinations. 3. The method for forming the surface microstructure of the flexible substrate film according to claim 1, wherein the metal film is one or more combinations of aluminum, copper or gold. 4 . The method for forming the surface microstructure of the flexible substrate film according to claim 1 , wherein the curve radius of the curve pattern is 150-450 microns, and the curve interval is 50-450 microns. 5 . The method for forming the surface microstructure of the flexible substrate film according to claim 1 , wherein the curved pattern is a plurality of parallel wavy lines. 6 . The method for forming the surface microstructure of the flexible substrate film according to claim 5 , wherein the order of the concavo-convex of two adjacent wavy lines is the same or reversed. 7 . 7 . The method for forming the surface microstructure of the flexible substrate film according to claim 1 , wherein the metal film has a thickness of 100-300 nm.