Fig. 4.

Recapillarity can manipulate the shape and local contact angle of droplets placed on dry substrates. (A) A droplet of liquid metal with a surface oxide (Left) supported by a glass slide. Electrochemical reduction of the oxide causes the metal to bead up (Right). Removal of the electrode before imaging creates the lobe on the top of the drop. (B) Three sequential side views (B, i–iii) of an EGaIn drop that asymmetrically dewets a glass slide in deionized water upon application of reductive potentials relative to a counterelectrode placed on the right side of the drop. Recapillarity causes the metal to move away from the anode, which is outside the frame of the image. The cathode gently touches the top of the drop to minimize perturbation of the shape of the metal.