Topography‐Directed Hot‐Water Super‐Repellent Surfaces. Issue 18 (30th July 2019)

• Record Type: Journal Article
• Authors: Zhu, Pingan; Chen, Rifei; Wang, Liqiu
• Is Part Of: Advanced science. Volume 6:Issue 18(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-07-30
• Subjects: heat transfer -- liquid repellency -- structure–property relationship -- wetting dynamics; Science -- Periodicals; 505
• DOI: 10.1002/advs.201900798
• Languages: English
• ISSNs: 2198-3844

Abstract

Abstract: Natural and artificial super‐repellent surfaces are frequently textured with pillar‐based discrete structures rather than hole‐based continuous ones because the former exhibits lower adhesion from the reduced length of the three‐phase contact line. Counterintuitively, here, the unusual topographic effects are discovered on hot‐water super‐repellency where the continuous microcavity surface outperforms the discrete microneedle/micropillar surface. This anomaly arises from the different dependencies of liquid‐repellency stability on the surface structure and water temperature in the two topographies. The unexpected wetting dynamics are interpreted by determining timescales for droplet evaporation, vapor condensation, and droplet bouncing. The associated heat transfer process is unique to the wetting states and remarkably distinct from each other in the two topographies. It is envisioned that hot‐water super‐repellent microcavity surfaces will be advantageous for a variety of applications, especially when both self‐cleaning and thermal insulation are imperative, such as clothing for scald protection and digital microfluidics for exothermic reactions. Abstract : The topography of surface microstructures can surprisingly affect the repellency of hot water in such a way that surfaces with interconnected microcavities outperform those with discrete microneedles/micropillars, as the interconnection structures give rise to higher capillary stability. Hot‐water super‐repellent microcavity surfaces will be conducive to various applications, including thermal‐insulating clothes for scald protection and digital microfluidics for exothermic reactions.