Fabrication of superhydrophobic copper surface by direct current sputtering and its underwater stability

• Superhydrophobic copper films were grown on Si substrates using DC sputtering.
• The substrate temperature plays a key role in the development of the surface morphology.
• The behavior of water in contact with the film at different static pressures was studied.
• A model is proposed to explain the change of the surface wettability.

Superhydrophobic copper films with hierarchically sandbeach-like morphologies were grown on Si substrates using direct current (DC) sputtering. After the surfaces were hydrophobized with 1-Octadecanethiol (ODT), the surfaces became superhydrophobic. The substrate temperature during sputtering played a key role in the formation of the surface morphology. The films exhibited long-term stability in the temperature range of 25 to 100 °C. The underwater stability of the surfaces was also characterized by studying the water contact behavior on the immersed surfaces under different static pressures. After immersion in different depth in water, the film surfaces changed from superhydrophobic even to superhydrophilic, due to the water trapped in the surface structures. A model was proposed to explain such change in the surface wettability.