February 4, 2022 @ 11:00 am - 12:00 pm
Learning from Natural Surfaces: from Transport to Phase Change of Water
K-C. Kenneth Park
Associate Professor, Dept. of Mechanical Engineering, Northwestern University
ATTEND IN PERSON: JHU Homewood campus, Malone G33/35
Numerous studies have focused on a low surface energy coating and a micro/nanoscale surface texture to design functional surfaces that delay frost formation and reduce ice adhesion. However, the scientific challenges for long-term icephobic surfaces have not been fully addressed because of degradation such as mechanical wearing. Inspired by the suppressed frost formation on concave regions of natural leaves, here we report findings on the frosting process on surfaces with various serrated structures. Dropwise condensation, the first stage of frosting, is enhanced on the peaks and suppressed in the valleys when the wavy surface is exposed to humid air, causing frosting to initiate from the peak. The condensed droplets in the valley are then evaporated, resulting in a non-frost band. The effects of surface topography on the frost pattern are systematically studied by varying the serrated geometry defined as the vertex angle, and numerically modeling the spatial distribution of diffusion flux of water vapor on the wavy surface. Under different ambient humidity levels, the magnitudes of diffusion flux at the non-frost boundaries of the surfaces are nearly identical, implying that the critical value of diffusion flux is the key to understanding the non-frost pattern.
Dr. K.-C. Kenneth Park joined the Department of Mechanical Engineering as an Assistant Professor in 2017. He received his BS in mechanical and aerospace engineering from Seoul National University in South Korea in 2008 and his MS and PhD in mechanical engineering from the Massachusetts Institute of Technology in 2013 supported with the Xerox-MIT Fellowship and Samsung Scholarship. He then worked as a postdoctoral fellow in the John A. Paulson School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering at Harvard University in 2013-2016. During his PhD and postdoctoral research, he received four awards including the MIT Wunsch Foundation Silent Hoist and Crane Award for Outstanding Graduate Research and Harvard Postdoctoral Award for Professional Development. He was selected as a recipient of the Hanwha Non-Tenured Faculty Award in 2021. His research group works on bio-inspired surface engineering problems and interfacial transport phenomena.