Counterintuitive Wetting Transitions in Doubly Reentrant Cavities as a Function of Surface Make-up, Hydrostatic Pressure, and Cavity Aspect Ratio (Advanced Materials Interfaces)

by Sankara Arunachalam, Zain Ahmad, Ratul Das, Himanshu Mishra
Year: 2020 DOI: 10.1002/admi.202001268


Arunachalam, S., Ahmad, Z., Das, R., Mishra, H.*, "Counterintuitive Wetting Transitions in Doubly Reentrant Cavities as a Function of Surface Make‐Up, Hydrostatic Pressure, and Cavity Aspect Ratio". Adv. Mater. Interfaces 2020, 2001268.


Surfaces that entrap air underwater can serve practical applications, such as mitigating cavitation erosion and reducing frictional drag. To achieve this, perfluorinated coatings are exploited that are non-biodegradable and fragile. Thus, coating-free, sustainable, and more robust approaches are desirable. Recently, a microtexture comprising doubly reentrant cavities (DRCs) has been demonstrated to entrap air on immersion in wetting liquids. While this is a promising approach, insights into the effects of surface chemistry, hydrostatic pressure, and cavity dimensions on wetting transitions remain unavailable. In response, we investigated Cassie-to-Wenzel transitions into circular DRCs submerged in water and compared them with cylindrical “simple” cavities (SCs). We found that at low hydrostatic pressures (~50 Pa), DRCs with hydrophilic and hydrophobic make-ups fill within 105 s and 10s, respectively, while SCs with hydrophilic make-up fill within < 10-2 s. Under elevated hydrostatic pressure ( 90 kPa), counterintuitively, DRCs with hydrophobic make-up fill dramatically faster than the commensurate SCs. This comprehensive report should provide a rational framework for harnessing microtextures and surface chemistry towards coating-free liquid repellency.


Doubly reentrant cavities simple cavities wetting transitions Underwater hydrostatic pressure capillary condensation diffusion breakthrough pressure