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Updated: Apr 29, 2026

Fabrication of Superhydrophobic Metal Surfaces for Anti-Icing Applications
Published on: August 15, 2018
Humidity-dependent wetting properties of high hysteresis surfaces
Michael J Mackel1, Sergio Sanchez, Julia A Kornfield
1Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
Abstract:
The advancing contact angle (thetaadv) of water on thin films ( approximately 1 microm) of poly(ethylene glycol) (PEG) with fluoroalkyl endgroups (6 kg/mol PEG with 10-carbon fluoroalkyl, denoted 6KC10) changes strongly with relative humidity (RH). Films of 6KC10 on silicon wafers pretreated with a fluorinated alkylsilane (TFOS) display thetaadv increasing from 75 degrees at 12% RH to 95 degrees at 94% RH. The surprising transition to nonwetting character at high humidity is attributed to fluoroalkyl groups ordering at the air-hydrogel interface when they are liberated by dissolution of PEG crystallites above 85% RH. When water is withdrawn from a drop on 6KC10, the contact line does not recede. This extreme hysteresis is attributed to restructuring of the gel to bury the fluoroalkyl groups when in contact with water.
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