Transport of a droplet by directional deformations with asymmetric electrode

Ratchet motions of a droplet were realized by the repeated deformations of it on an asymmetric V-shaped electrode. The surface wetting of the electrode was reversibly regulated by electrochemical reactions of the ferrocenyl-alkanehiol monolayer. When the surface was changed from repulsive to wetting, the contact line of the droplet facing to the wider side advanced while the other side was almost pinned. The contact line facing to the narrower side retracted when the surface was changed from wetting to repulsive. The directional deformations of the droplet resulted in a net transport of it. The process of the droplet deformation was discussed based on the contact angle measurement.