Fig. 3.

(A) Successive images extracted from the 2D simulations. A drop with viscosity $\eta$ = 16 mPa.s and radius $R$ = 1 mm is deposited on an evaporating bath and spontaneously self-propels. The corresponding movie is Movie S6. (B) Drop velocity $V$ as a function of time $t$. (C) Difference in film thickness $h$ between the left ($h_l$, in blue) and right ($h_r$, in red) parts of the drop where the film is thinner. (D) Model for the propulsion force: The film has a mean thickness $h\ll R$, and vapor is continuously escaping with a characteristic velocity $u$. The difference $\mathrm{\Delta }h\ll h$ in the film thickness changes the vapor distribution, generating a viscous propelling force $F_{prop}$, directed toward the larger opening.