Self-propelled drops on hydrophilic microfinned surfaces

Straight and curved hydrophilic microfinned surfaces are prepared in this work by photolithography and sputtering coating techniques using silicon wafers as substrates. The behavioral characteristics of drops on these surfaces are discussed by using image-processing technology. The experimental results show that when a drop is placed on the straight microfinned surface, the front contact line of the drop can move, while the rear contact line remains fixed. On the curved microfinned surface, however, both the front and the rear contact line can move. The drop can be self-propelled directionally from the region with larger roughness to the region with smaller roughness. The characteristics of velocity and acceleration on both surfaces are analyzed. A theoretical model is proposed by analyzing the energy conversion and compared with the experimental results. This study provides a novel microstructured surface for enhancing the heat-transfer performance of condensers.