Thermal stability of superhydrophobic, nanostructured surfaces

[Display omitted] . ► The thermal stability of superhydrophobic surfaces after thermal annealing. ► SiOx-contained carbon coatings show robust superhydrophobicity up to 350°C. ► Superhydrophobicity is stable on nanostructured surfaces with high aspect ratio. ► Surfaces become superhydrophilic for annealing temperatures higher than 500°C. 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 90o to 60o while nanostructured surfaces maintained superhydrophobicity with more than 150° for annealing temperatures between 25 and 300°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°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°C.