A contamination-free microstructure in a humid environment by means of a combination of hydrophilic and hydrophobic surfaces

A novel concept that prevents dust particles, which are often formed in wet/dry ambient cycles, from contaminating microstructure surfaces is presented. It is shown that a geometrical combination of hydrophilic and hydrophobic surfaces can prevent the contamination on a part of the hydrophobic surface. The driving force of the mechanism is generated by the surface tension force of condensed water on the surface. Formation of isolated water droplets which become nuclei of contamination is prevented by controlling the dynamic behavior of the condensed water. It is also shown that the hydrophilic surface can be realized by forming concave patterns on a hydrophobic surface with conventional silicon etching. This greatly reduces the fabrication steps of the hybrid surface, making the proposed technique realistic.