This Supporting Information includes:Figure S1, S2, S3Supplementary Video Supplementary Video S1: Locomotion of the mobile robot. Supplementary Video S2: Vortex deforming the liquid-liquid interface. Supplementary Video S3: Locomotion of the mobile robot without electrode attached. Supplementary Video S4: Locomotion of the mobile robot with reversed polarity. Supplementary Video S5: Drawing “SIT” by controlling a floating robot with multiple electrodes.  Corresponding author Email:  vito.cacucciolo@epfl.ch, hshige@shibaura-it.ac.jp