Climbing Liquid Drops on Chemically Patterned Surfaces: Potential Applications for On-Chip Microfluidics

We employ reactive-wetting drops to move fluid against gravitational force. Early experiments have shown that the surface energy gradient must achieve a critical value in order to induce a significant increase in the front dewetting. The velocity of a climbing-drop is constant, unlike the gradual decrease intuitively linked to object under gravitation. The drop velocity does decrease, however, for increased slope. The maximum inclination, or stopping, angle for our particular setup is 25.. A non-dimensional ratio is employed to reproduce the experimentally obtained trend, and its use may be of value in the future.