A method and device for laser stress-assisted surface crack growth of PDMS

Abstract

The present invention belongs to the field of laser surface modification, and discloses a method and device for laser stress-assisted surface crack growth of PDMS. The present invention uses direct laser radiation on the surface of PDMS, and controls its surface modification or the formation of surface microcracks through stress control and various parameters of the laser (laser energy, pulse repetition frequency, focal plane, etc.), which can improve the surface bioadhesion of PDMS to varying degrees; moreover, through the control of the stress direction of the working platform, the growth direction of cracks can be controlled in complex local areas on the surface, making the patterning more delicate; compared with the prior art, the present invention improves the processing quality and has higher processing efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of laser surface modification, and particularly relates to a method and device for laser stress-assisted PDMS surface crack growth. Background Art

[0002] PDMS (polydimethylsiloxane) is a special polymer with characteristics such as biocompatibility, high optical transparency, gas permeability, and mechanical flexibility, and is widely used in optical conduction, medical devices, microelectromechanical systems, microfluidic chips, and gas sensors, etc. Among all polymer materials used for fabricating microfluidic devices, PDMS has received the most attention and has obvious advantages over PC (polycarbonate) and PMMA (polymethyl methacrylate) in the following aspects: (1) It is soft and elastic, and is easy to remove from the template without damaging itself or the template; (2) It can be easily obtained by low-temperature polymerization; (3) It is transparent to light with wavelengths above 280 nm, suitable for optical detection; (4) It is biologically inert and non-toxic; (5) It has good gas permeability, which is conducive to oxygen supply to a closed system for cell culture; (6) It is easy to seal with other materials. Even so, PDMS is still restricted to a certain extent in cell culture applications. Untreated PDMS tends to concentrate on the air-exposed interface, making the material have a very hydrophobic coating, which is prone to non-specific adsorption of proteins or small hydrophobic molecules, and is a highly hydrophobic material. Since the current functional requirements in cell culture or microfluidic devices demand cell adhesion and growth, PDMS needs to be surface-modified in order to be better used in modern technology research and applications.

[0003] Currently, laser patterning of the PDMS surface is a means of modification. Laser patterning of the PDMS surface is mainly based on the thermal expansion of the laser. After the laser beam is focused, it can act on a very small area on the material surface. Microcracks will form in the PDMS (polydimethylsiloxane) area after laser radiation, and these microcracks can fix biomolecules such as proteins, cell growth factors, enzymes, and nucleic acids on the surface of a specific material, providing a good environment for cell attachment and growth. Or the surface of PDMS (polydimethylsiloxane) is modified after laser radiation, which can improve biological adhesion.

[0004] Using laser to act on the material surface for modification or forming surface microcracks can simplify the PDMS surface modification steps without affecting the surface structure or chemical properties of the unmodified area, greatly improving the preparation efficiency and having broad application prospects.

[0005] The basic technical principle is as follows: The laser generates high-energy pulsed laser, and the energy and frequency of the laser are adjustable. The laser is reflected by the mirror in the optical path system and focused onto the PDMS surface by a convex lens. Under the action of the high energy and impact force brought by the local area of the PDMS surface under laser radiation, complex photothermal and photochemical reactions occur, and it instantaneously vaporizes or splashes, thereby forming microcracks on the surface of the local area of interaction. Or the laser energy reaches the chemical bond energy of PDMS (polydimethylsiloxane) to generate new functional groups that can promote cell adhesion, improving the surface biocompatibility. The improvement of the biocompatibility of the PDMS (polydimethylsiloxane) surface by laser action can vary to different degrees according to laser process parameter variables such as different pulse energies, pulse overlap rates, and defocus amounts.

[0006] With the development of current microfluidic chips and various portable detection instruments, higher requirements are placed on microbial culture media. The above-mentioned laser patterning PDMS surface technology has certain limitations in the forming effect of surface microcracks, cannot accurately control the crack growth direction, and the growth length is limited, which is not conducive to large-area processing. Summary of the Invention

[0007] In order to overcome the disadvantages and deficiencies existing in the prior art, the primary object of the present invention is to provide a device for laser stress-assisted PDMS surface crack growth.

[0008] Another object of the present invention is to provide a method for laser stress-assisted PDMS surface crack growth using the above device. This method is to modify the surface of the material or form surface microcracks under the action of laser with stress assistance, and assist in controlling the growth of microcracks through the magnitude and direction of stress. Without affecting the surface structure or chemical properties of the non-modified area, the surface pattern is refined, the PDMS surface modification steps are simplified, and the preparation efficiency is greatly improved.

[0009] The object of the present invention is achieved by the following technical solutions:

[0010] A device for laser stress-assisted PDMS surface crack growth, the device includes a laser, a collimator, a beam homogenizer, a mirror, a convex lens, PDMS, an XY working platform, a motion control system, and a computer; the computer is respectively connected to the laser and the motion control system; the motion control system is also connected to the XY working platform; the PDMS is placed on the XY working platform and clamped by the fixture of the XY working platform; the laser, the collimator, the beam homogenizer, the mirror, and the convex lens are successively located in the laser beam path emitted by the laser.

[0011] The mirror changes the transmission angle of the laser beam coming from the beam homogenizer and then vertically focuses it onto the PDMS surface through the convex lens.

[0012] A method for laser stress-assisted PDMS surface crack growth using the above-mentioned device, comprising the following steps:

[0013] The computer guides the laser to generate high-energy pulsed laser with adjustable energy and frequency. After being collimated by a collimator, it enters a homogenizer for beam homogenization. Then, it passes through a reflecting mirror to change the transmission angle, and then passes through a convex lens to be vertically focused on the PDMS surface, causing the local area of the PDMS surface to instantaneously vaporize or spatter under laser radiation, thereby forming microcracks on the surface of the local area of interaction. At the same time, the fixture of the XY working platform applies a variable tensile stress to the PDMS. The computer guides the motion control system to precisely control the two-dimensional movement of the XY working platform in the horizontal direction. When microcracks are formed on the PDMS surface, the tensile stress will cause the microcracks on the PDMS surface to grow in the stress direction, and the stress further enhances the forming effect of the surface microcracks.

[0014] The tensile stress refers to the control of the resultant force on the PDMS by the tensile force ratio in the XY direction.

[0015] In the device and method of the present invention, the laser acting on the PDMS (polydimethylsiloxane) surface improves the biological adhesion. According to different laser process parameter variables such as pulse energy, pulse overlap rate, and defocus amount, the biological adhesion on the PDMS surface changes to different degrees. At the same time, the XY working platform adjusts the tensile force parameters to further adjust the performance of biological adhesion.

[0016] After the laser beam energy is adjusted to an appropriate value and then collimated and focused, it can act on a very small area of the PDMS surface. Therefore, the laser radiation after power regulation to the specified area of the PDMS (polydimethylsiloxane) will only form microcracks without generating microgroove structures. A controllable tensile force is applied to the PDMS in the horizontal direction of the two-dimensional XY working platform, and its horizontal movement is coordinated to better control the crack growth. The growth of microcracks is jointly controlled by the laser scanning path and the two-dimensional tensile stress XY working platform, which can better solve the problem of damage to the surface structure in the non-radiation area. These microcracks can fix biomolecules such as proteins, cell growth factors, enzymes, and nucleic acids at specific positions on the material surface, providing a good environment for cell attachment and growth. At the same time, the surface of the PDMS (polydimethylsiloxane) after laser radiation is modified, which can improve the biological adhesion.

[0017] The present invention has the following advantages and effects compared with the prior art:

[0018] (1) Good processing adaptability for complex local areas: The XY working platform moves in two-dimensional horizontal directions and prepares the patterns of the space required to improve cell adhesion in a path scanning manner, so as to improve the biological adhesion of the required modified areas on the PDMS surface without affecting the unmodified areas. Therefore, the method and device of the present invention have good processing adaptability for complex local areas.

[0019] (2) Stress increases the degree of surface microcrack formation and improves processing efficiency: After applying a certain tensile force to the XY working platform, compared with simple placement processing, at the same laser power, the radiation area of surface microcracks is increased to a certain extent. Therefore, the present invention can effectively improve processing efficiency on the basis of low-cost increase and is more adaptable to current processing and commercialization.

[0020] (3) The growth direction angle of surface cracks is controllable, meeting the biological adhesion requirements of various fields: Through the ratio of applied tensile forces, the microcracks formed by laser radiation no longer simply grow at 90° on both sides of the path; theoretically, it can be completely controlled by tensile force to grow in any direction, solving the current increasingly refined requirements. Description of the Drawings

[0021] Figure 1 It is a device diagram of laser stress-assisted PDMS surface crack growth of the present invention, where (1) is a laser, (2) is a collimator, (3) is a beam homogenizer, (4) is a reflector, (5) is a convex lens, (6) is PDMS, (7) is an XY working platform, (8) is a motion control system, and (9) is a computer.

[0022] Figure 2 It is a simple schematic diagram of the XY working platform.

[0023] Figure 3 It is a method of laser stress-assisted PDMS surface crack growth using the device of the present invention, and the sample diagrams obtained when the included angles between the tensile stress direction and the vertical direction are 0°, 30°, and 60° respectively, where a is the sample diagram obtained when the included angle is 0°, b is the sample diagram obtained when the included angle is 30°, and c is the sample diagram obtained when the included angle is 60°. Detailed Embodiments

[0024] The present invention will be further described in detail below in conjunction with embodiments, but the embodiments of the present invention are not limited thereto.

[0025] Embodiment 1

[0026] A device for laser stress-assisted PDMS surface crack growth, as Figure 1As shown in the figure, the device includes a laser (1), a collimator (2), a homogenizer (3), a mirror (4), a convex lens (5), PDMS (6), an XY working platform (7), a motion control system (8), and a computer (9); the computer is respectively connected to the laser and the motion control system; the motion control system is also connected to the XY working platform; the PDMS is placed on the XY working platform and clamped by the fixture of the XY working platform; the laser, the collimator, the homogenizer, the mirror, and the convex lens are successively in the path of the laser beam emitted by the laser;

[0027] The mirror changes the transmission angle of the laser beam coming from the homogenizer, and then the laser beam is vertically focused onto the surface of the PDMS through the convex lens.

[0028] A simple schematic diagram of the XY working platform is as Figure 2 shown, and tensile stress can be applied to the PDMS in four directions.

[0029] Embodiment 2

[0030] A method for laser stress-assisted crack growth on the surface of PDMS using the above device includes the following steps:

[0031] The computer instructs the laser to generate high-energy pulsed laser with adjustable energy and frequency. After being collimated by the collimator, it enters the homogenizer for homogenization. Then, it passes through a 45° mirror to change the transmission angle, and then passes through the convex lens to be vertically focused onto the surface of the PDMS. Under the action of appropriate energy and impact force under laser radiation, complex photothermal and photochemical effects occur on the local area of the PDMS surface, and instantaneous vaporization or splashing occurs, thereby forming microcracks on the surface of the local area of interaction. At the same time, the fixture of the XY working platform applies variable tensile stress to the PDMS, and the computer instructs the motion control system to precisely control the XY working platform to perform two-dimensional motion in the horizontal direction. When microcracks are formed on the surface of the PDMS, the tensile stress will promote the growth of microcracks on the surface of the PDMS in the stress direction, and the stress further enhances the forming effect of the surface microcracks. The direction of the resultant force on the PDMS is controlled by the tensile force ratio in the XY directions, and finally, the growth of cracks in the ideal area is controlled, and a more complex regional pattern required for surface modification of the PDMS is prepared. Thus, the surface of the PDMS (polydimethylsiloxane) can be simply and quickly patterned without affecting the non-modified area, and the quality and efficiency of crack generation are greatly improved, and its bioadhesion is enhanced.

[0032] In this embodiment, the sample diagrams obtained when the angle between the tensile stress direction and the vertical direction is 0°, 30°, and 60° respectively are as Figure 3 shown.

[0033] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for laser stress-assisted PDMS surface crack growth, characterized in that The method includes the following steps: The computer guides the laser to generate high-energy pulsed laser with adjustable energy and frequency. The laser passes through a collimator for collimation, then enters a beam homogenizer for beam homogenization. Next, it passes through a reflector to change the transmission angle, and then through a convex lens to be vertically focused on the surface of the PDMS, causing the local area of the PDMS surface to instantaneously vaporize or spatter under laser radiation, thereby forming microcracks on the surface of the local interaction area. At the same time, the fixture of the XY working platform applies a variable tensile stress to the PDMS. The computer guides the motion control system to precisely control the XY working platform to perform two-dimensional motion in the horizontal direction. When the microcracks are formed on the PDMS surface, the tensile stress will promote the growth of the microcracks on the PDMS surface in the stress direction, and the stress further enhances the forming effect of the surface microcracks. The tensile stress refers to the control of the resultant force on the PDMS by the tensile force ratio in the XY direction. The device used in the method includes a laser, a collimator, a beam homogenizer, a reflector, a convex lens, a PDMS, an XY working platform, a motion control system, and a computer. The computer is respectively connected to the laser and the motion control system. The motion control system is also connected to the XY working platform. The PDMS is placed on the XY working platform and clamped by the fixture of the XY working platform. The laser, the collimator, the beam homogenizer, the reflector, and the convex lens are successively located in the laser beam path emitted by the laser.

2. The method according to claim 1, wherein: The reflector changes the transmission angle of the laser beam coming from the beam homogenizer and then focuses it vertically on the PDMS surface through the convex lens.

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