Superhydrophobic textures for microfluidics

Superhydrophobic surfaces have opened a completely new field of investigation with both fundamental and practical perspectives. Research on these materials has mostly focused on their extreme non-wettability, which has large-scale implications in the context of self-cleaning and impact processes. However, the implications of superhydrophobicity for transport phenomena, which are especially important at micro- and nanoscales, remain largely unexplored. Here, we summarize recent advances in this field, including the physical causes of water repellency, the origins of superhydrophobicity and a current switch in focus from wetting to related areas such as the remarkable drag-reducing ability of superhydrophobic materials. In particular, we show that superhydrophobic surfaces induce novel hydrodynamic properties such as giant effective slip, superfluidity and mixing, and affect electrokinetic phenomena. We also discuss developments and strategies in the fabrications of superhydrophobic materials for relevant applications, including microfluidic lab-on-a-chip devices. We finally suggest several remaining challenges in the field.