Principles of surface-directed liquid flow in microfluidic channels
Principles of surface-directed liquid flow in microfluidic channels
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DOI：
10.1021/ac020269w
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发表时间：
2002-08-15
影响因子：
7.4
通讯作者：
Beebe, DJ
中科院分区：
文献类型：
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作者：
Zhao, B;Moore, JS;Beebe, DJ
为了引导微通道内的液体流动，通过使用自组装单层 (SAMS) 结合多流层流或光刻来形成表面自由能图案。对于光刻方法，设计并合成了两种可光裂解的 SAM。通过光脱保护获得了羧酸封端的单分子层，并通过接触角和X射线光电子能谱证实了这一点。使用这些图案化方法中的任何一种，我们都表明，当压力保持在临界值以下时，水性液体仅沿着亲水路径流动；液体被称为被虚拟墙限制。通过分析导出了表面图案通道中液体流动的几个原理并通过实验进行了验证。这些原则包括虚拟壁能够承受的最大压力、能够支持自发流动的亲水通道的临界宽度、在外部压力下液体流的最小宽度、在液体不穿过亲水-疏水边界的情况下可以引入亲水通道的临界曲率半径、以及在最大压力下两股液体流保持分离的最小距离。实验结果与分析预测非常吻合。
To direct liquid flow inside microchannels, surface free energies were patterned by use of self-assembled monolayers (SAMS) in combination with either multistream laminar flow or photolithography. For the photolithographic method, two photocleavable SAMs were designed and synthesized. Carboxylic acid-terminated monolayers were obtained by photodeprotection, which was confirmed by contact angle and X-ray photoelectron spectroscopy. Using either of these patterning methods, we show that aqueous, liquids flow only along the hydrophilic pathways when the pressure is maintained below a critical value; the liquids are referred to as being confined by virtual walls. Several principles of liquid flow in surface-patterned channels were derived analytically and verified experimentally. These principles include the maximum pressure that virtual walls can withstand, the critical width of the hydrophilic pathway that can support spontaneous flowi the smallest width of the liquid streams under an external pressure, the critical radius of curvature of turns that can be introduced into the hydrophilic pathway without liquid crossing the hydrophilic-hydrophobic boundary, and the minimal distance for two liquid streams to remain separated under the maximum pressure. Experimental results are in good agreement with the analytical predictions.