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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

The Rational Nanostructuring of Surfaces for Extreme Icephobicity in Nature and Technology

Get access (open in a dialog) DOI: 10.1615/IHTC15.kn.000021
pages 389-404

Résumé

Icing of surfaces is commonplace in nature, technology and everyday life, bringing with it sometimes catastrophic consequences. Superhydrophobic surfaces, with micro- , nano-, or (often biomimetic) hierarchical roughnesses, have shown in laboratory setttings excellent repellency and low adhesion to water down to temperatures near the freezing point. For extreme icephobicity, however, additional important functionalities (in addition to superhydrophobicity) are required. Despite progress, suppressing ice formation passively with a rational methodology leading to the design of surfaces with extraordinary resistance to ice formation and adhesion under a variety of conditions remains elusive. Here we highlight our recent and, in this context, other related work in this area and present unexpected results on ice formation on surfaces. We show that homegeneous nucleation starting at the free surface of a droplet can become the preferred ice nucleation mode over the widely accepted heterogeneous nucleation. We discuss a new mechanicm for the freezing of undercolled droplets on surfaces, explaining also how frost can propagate in dry environments. Finally we focus on the science base of deterministic surface texture design leading to extreme icephobicity. Employing (necessarily) knowledge from the crossroads of nucleation thermodynamics, fluid dynamics and (surface) nananoengineering, we show how surfaces can be made, where, for example, at -21°C the ice nucleation of a sessile mm-size water droplet supercooled at the same temperature is remarkably delayed by over 25 hours. Equally remarkable are results demonstrating complete surface drop impalement resistance (complete rebound) at -30°C for drop impact velocity of 2.6 m/s.