Condensation Induced Delamination of Nanoscale Hydrophobic Films

Abstract

Vapor condensation is a crucial phenomenon governing the efficiency of many processes. In particular, dropwise condensation on hydrophobic thin films (≈100 nm-thick) has the potential to achieve remarkable heat transfer. However, the lack of durability of these thin films has limited applications for a century. Although degradation due to steam condensation has been described as "blistering," no satisfactory insight exists capable of elucidating the driving force for film delamination. Here, it is shown that nanoscale pinholes in hydrophobic films are the source of blister formation. By creating artificial pinholes via nanoindentation on thin (30 to 500 nm-thick) fluorinated hydrophobic films, it is demostrated that water blisters can be initiated at the pinholes during condensation. It is experimentally demonstrated that vapor is transferred to the blister through the nanoscale pinhole, and the driving force for delamination is capillary pressure generated at the pinhole by the pinned liquid-vapor interface. The techniques and insights presented here will inform future work on polymeric thin film and enable their durable design for a variety of applications.

Endoscopic Visualization of Contact Line Dynamics during Pool Boiling on Capillary‐Activated Copper Microchannels

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Atmosphere‐Mediated Scalable and Durable Biphilicity on Rationally Designed Structured Surfaces

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Development of automated angle-scanning, high-speed surface plasmon resonance imaging and SPRi visualization for the study of dropwise condensation

“…Dropwise condensation occurs on non-wetting surfaces or partially wetting surfaces (Nouri et al 2012). After nine decades of research on dropwise condensation (Cho et al 2017;Emonsi 1939;Enright et al 2014;Miljkovic and Wang 2013;Schmidt et al 1930), design and fabrication of a surface that can sustain this mode of condensation for a long term have not been successful (Ahlers et al 2018;Ma et al 2019;Oh et al 2018). The main reason for this is that there is no united understanding of dropwise condensation phenomena because of the complexity of the physics involved.…”