From hydrophilic to superhydrophobic: fabrication of micrometer-sized nail-head-shaped pillars in diamond.

The hydrophobicity of microtextured diamond surfaces was investigated. Pillarlike structures were fabricated in both nanocrystalline diamond and microcrystalline diamond. By changing the surface termination of the textured diamond surface, we could switch between superhydrophobic surfaces and hydrophilic surfaces. Examined terminations were hydrogen, fluorine, and oxygen. To evaluate the wetting properties, advancing and receding contact angles were measured. By designing pillars with a wide diamond top on a narrower silicon stem, superhydrophobicity was achieved even when the advancing contact angle on the unstructured diamond surface was below 70 degrees. The possibility to manipulate the hydrophobicity and the Fresnel reflection simultaneously at an infrared wavelength is also demonstrated.