Controlling the directional sliding velocity of a liquid through an omniphobic nano-bump surface

Directional liquid manipulation surfaces have been widely used in advanced digital microfluidic platforms for biological and chemical analyses. However, studies on surfaces capable of controlling the droplet behavior of various liquids, including oil as well as water, through sliding velocity have been rare. This article reports the development of an omniphobic surface capable of controlling the directional sliding velocity of a liquid by using partially exposed nano-bump morphologies. A robust and reliable fabrication criterion is discussed for the fabrication of a novel functional liquid sliding surface through the ultraviolet ozone partial etching technique of a UV-curable resin that contains inorganic oxide nanoparticles. The fabricated hierarchical micro-stripes with overhang cross-sectional structures are omniphobic and exhibit droplet sliding velocity control. The velocities of various liquid droplets with varying surface tensions can be controlled by adjusting the level of nano-roughness formed on the surface of the micro-line structure.