Thermal stability of superhydrophobic, nanostructured surfaces

The thermal stability of superhydrophobic, nanostructured surfaces after thermal annealing was explored. Flat surfaces coated with hydrophobic diamond-like carbon (DLC) via plasma polymerization of hexamethyldisiloxane (HMDSO) showed a gradual decrease in the water contact angle from 90 degrees to 60 degrees while nanostructured surfaces maintained superhydrophobicity with more than 150 degrees for annealing temperatures between 25 and 300 degrees C. It was also found that surfaces with nanostructures having an aspect ratio of more than 5.2 may maintain superhydrophobicity for annealing temperatures as high as 350 degrees C; above this temperature, however, the hydrophobicity on surfaces with lower aspect ratio nanostructures gradually degraded. It was observed that regardless of the aspect ratios of the nanostructure, all superhydrophobic surfaces became superhydrophilic after annealing at temperatures higher than 500 degrees C. (C) 2012 Elsevier Inc. All rights reserved.