Fabrication of super-hydrophobic channels
Fabrication of super-hydrophobic channels
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DOI：
10.1088/0960-1317/20/2/025029
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发表时间：
2010-02-01
影响因子：
2.3
通讯作者：
Luo, Cheng
中科院分区：
文献类型：
--
作者：
Liu, Xinchuan;Luo, Cheng
在这项工作中，开发了一种新的方法来创建通道，不仅具有超疏水的底部表面，但也超疏水的侧壁。研究人员已经证明，在微/纳米结构形成的顶部和底部表面的通道中，流动经历的阻力较小，因此需要较小的驱动压力。在不仅具有图案化的顶表面和底表面而且具有图案化的侧壁表面的通道中，应当进一步减小拖曳力。然而，由于现有的光刻方法的限制，侧壁不能被适当地图案化。因此，在这项工作中开发了一种新的方法来克服这一障碍。首先使用模塑方法在PDMS膜上产生纵横比为1.4、2.0和2.7的聚二甲基硅氧烷（PDMS）微柱，然后应用热压印工艺将其分别转移到三个1 mm宽和1 mm深的通道的侧壁和底表面。考虑了相应的变形机制。PDMS膜的宽度对所产生的通道的横截面轮廓具有关键影响。沟道拐角半径和侧壁倾斜度随薄膜宽度的增加而增大。测量并比较了变形前后PDMS薄膜的接触角。由于微柱之间的距离变化很小，因此在侧壁的中间部分以及在所产生的通道的底部的接触角与原始PDMS膜上的接触角几乎没有差异。然而，接触角增加和减少，分别在底部和顶部角落的产生的通道，因为PDMS膜在这些角落在制造过程中被压缩和拉伸。根据现有的两个理论公式，进一步分析了各个通道中接触角的变化。这些变化随着PDMS微柱纵横比的增加而增加。所制备的超疏水通道可以潜在地用于减少微流体应用中的阻力。
A new approach was developed in this work to create channels which had not only super-hydrophobic bottom surfaces but also super-hydrophobic sidewalls. Researchers have demonstrated that a flow experienced less drag forces and thus required smaller driving pressure in a channel of micro/nanostructure-formed top and bottom surfaces. The drag forces should be further reduced in a channel which has not only patterned top and bottom surfaces but also patterned sidewall surfaces. However, due to the limitation of the existing lithographic approaches, sidewalls could not be properly patterned. Therefore, a new approach was developed in this work to overcome this obstacle. Polydimethylsiloxane (PDMS) micropillars of aspect ratios 1.4, 2.0 and 2.7 were first generated on PDMS films using a molding method, and then transferred to the sidewalls and bottom surfaces of three 1 mm wide and 1 mm deep channels, respectively, applying a hot-embossing process. The corresponding deformation mechanism was considered. The widths of the PDMS films had a critical effect on the cross-section profiles of the generated channels. The radii of the channel corners and inclined degrees of the sidewalls increased with the film widths. Contact angles on the PDMS films before and after the deformations were measured and compared. The contact angles in the middle portions of the sidewalls, as well as at the bottoms of the generated channels, were little difference from those on the original PDMS films due to the small changes in the distances between the micropillars. However, the contact angles were increased and decreased, respectively, at the bottom and top corners of the generated channels since the PDMS films were compressed and stretched at these corners during the fabrication. The variation of the contact angle in each channel was further analyzed according to two existing theoretical formulas. These variations increased with the increasing aspect ratios of the PDMS micropillars. The super-hydrophobic channels fabricated could be potentially employed to reduce drag forces in microfluidic applications.