Trapping air at the solid-liquid interface is a promising strategy for reducing frictional drag and desalting water, although it has thus far remained unachievable without perfluorinated coatings. Here, we report on biomimetic microtextures composed of doubly reentrant cavities (DRCs) and reentrant cavities (RCs) that can enable even intrinsically wetting materials to entrap air for long periods upon immersion in liquids. Using SiO2/Si wafers as the model system, we demonstrate that while the air entrapped in simple cylindrical cavities immersed in hexadecane is lost after 0.2 s, the air entrapped in the DRCs remained intact even after 27 days (~106 s). To understand the factors and mechanisms underlying this ten-million-fold enhancement, we compared the behaviors of DRCs, RCs and simple cavities of circular and non-circular shapes on immersion in liquids of low and high vapor pressures through high-speed imaging, confocal microscopy, and pressure cells. Those results might advance the development of coating-free liquid repellent surfaces.
|Original language||English (US)|
|State||Published - Sep 6 2018|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We thank Mr. Ulrich Buttner and Mr. Ahad A. Sayed from the KAUST Core Labs for their assistance in microfabrication, and Mr. Edelberto Manalastas and Mr. Zain Ahmad from HM’s research group for assistance in the measurement of breakthrough pressures. We acknowledge Mr. Ivan Gromicho, Scientific Illustrator at King Abdullah University of Science and Technology (KAUST), for preparing Fig. 5 and Dr. Virginia Unkefer and Dr. Elisabeth Lutanie (KAUST) for assistance in editing the manuscript. We also acknowledge Dr. Yair Kaufman (Ben-Gurion University of the Negev, Israel) for fruitful discussions.