Comment on "Self-Running Droplet: Emergence of Regular Motion from Nonequilibrium Noise"

In a recent Letter (Y. Sumino et al., PRL 94, 068301 (2005)) a spontaneous motion of an oil droplet in the surrounding aqueous media along a glass surface was reported. The authors suggested that the self-locomotion is driven by a difference in wettability between the front and the rear of a droplet sustained by its translational motion. Whereas we do not question the presented visual evidences (see Ref.22 in the Letter), our comment concerns an interpretation of the experimental data of Sumino et al. and the underlying physical mechanism of the self-locomotion