Condensation Induced Delamination of Nanoscale Hydrophobic Films. (1st September 2019)

• Record Type: Journal Article
• Authors: Ma, Jingcheng; Cha, Hyeongyun; Kim, Moon‐Kyung; Cahill, David G.; Miljkovic, Nenad
• Is Part Of: Advanced functional materials. Volume 29:Number 43(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-09-01
• Subjects: blister -- condensation -- droplets -- failure -- hydrophobic; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201905222
• Languages: English
• ISSNs: 1616-301X

Abstract

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. Abstract : Nanoscale pinholes in hydrophobic films govern blister formation and long‐term degradation during water vapor condensation. The outcomes of this work provide guidelines for creating robust hydrophobic films for a plethora of applications, especially stable dropwise condensation.