| GUO Yong-gang,LYU Zhi,ZHU Ya-chao.Wettability and Anisotropy of Laser Patterned Aluminum Alloy Surfaces[J],52(3):352-359, 369 |
| Wettability and Anisotropy of Laser Patterned Aluminum Alloy Surfaces |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.03.033 |
| KeyWord:6061 aluminum superhydrophilic/superhydrophobic nanosecond laser etching anisotropy |
| Author | Institution |
| GUO Yong-gang |
School of Mechanical & Electrical Engineering, Henan University of Technology, Zhengzhou , China;Carbon Fiber Composites International Joint Research Lab in Henan, Henan University of Technology, Zhengzhou , China;Henan Provincial Engineering Laboratory of Automotive Composite Materials, Henan University of Technology, Zhengzhou , China |
| LYU Zhi |
School of Mechanical & Electrical Engineering, Henan University of Technology, Zhengzhou , China |
| ZHU Ya-chao |
School of Mechanical & Electrical Engineering, Henan University of Technology, Zhengzhou , China |
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| Abstract: |
| In this paper, a superhydrophobic 6061 aluminum alloy surface with a microgrid pattern was fabricated by nanosecond laser etching and subsequent modification of low-surface-energy fluorosilane. Then, rectangular, parallelogram and circular superhydrophilic microfluidic channels were fabricated by laser etching again on the surface of the superhydrophobic aluminum alloy. The anisotropic wetting and rolling resistance phenomena of rectangular microfluidic channels along the direction parallel and perpendicular to the grooves were analyzed. The effects of laser-etched groove width and depth on the anisotropic wetting and rolling of droplets on the surface of superhydrophilic/superhydrophobic patterned aluminum alloys were investigated. And the movement of droplets along microfluidic channels under the action of gravity was investigated. In order to explain the phenomenon of anisotropic wetting and anisotropic rolling of droplets on the contact surface more clearly, we innovatively defined the parallel contact angle θcp, vertical contact angle θcv, parallel rolling angle θrp and vertical rolling angle θrv in this paper, and evaluated the changing laws of anisotropic wetting and anisotropic rolling through their changing laws. Scanning electron microscopy(SEM)and three-dimensional profiler were used to observe the morphology of the aluminum alloy surface. The contact angle measurement instrument was employed to observe and measure the contact state and adhesion state of the droplets on the solid surface. The high-speed camera was applied to observe the specific situation of the water droplet movement on the surface. The experimental results showed that the droplets exhibited obvious contact anisotropy and rolling anisotropy on the surface of the superhydrophilic/superhydrophobic patterned aluminum alloy. And the droplets showed different contact states and different adhesion on the surfaces with different wettability, for example, 10 μL of water droplets spread on 0.1 mm wide linear grooves, and the parallel contact angle θcp was only 93.9°; while perpendicular to the direction of the linear groove, the vertical contact angle θcv was 152.6°. The parallel rolling angle θrp was 21.5°, while the vertical rolling angle θrv was greater than 90°, and the water droplets cannot roll off. Both the parallel contact angle θcp and the vertical contact angle θcv of water droplets decreased with the increase of the linear groove width, at the same time the contact angle anisotropy tended to increase. The vertical rolling angle θrv were greater than 90° and could not fall off, while the parallel rolling angle θrp decreased with the increase of the linear groove width, and it can be concluded that the rolling resistance anisotropy increased with the increase of the linear groove width. As linear groove depth increases, there was no significant change in wettability anisotropy and rolling resistance anisotropy. Based on the characteristics of rolling anisotropy, a kind of aluminum alloy surface with microfluidic directional transport by gravity was prepared successfully, which has good droplet anisotropy and lossless transmission performance. Nanosecond laser processing can control the microstructure, macroscopic shape and the size of the processing area, anisotropic superhydrophilic/superhydrophobic patterned surfaces can be processed easily combined with subsequent low surface energy modification technology. The method here has the advantages of low cost, simple process, and fast response, so it's suitable for the processing of hydrophilic patterns on superhydrophobic surfaces of various metal substrates. Therefore, it has potential applications in biopharmaceutical, high-throughput cell screening and droplet storage. |
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