title: Propulsion on a superhydrophobic ratchet.
abstract: Liquids in the Leidenfrost state were shown by Linke to self-propel if placed on ratchets. The vapour flow below the liquid rectified by the asymmetric teeth entrains levitating drops by viscosity. This effect is observed above the Leidenfrost temperature of the substrate, typically 200°C for water. Here we show that coating ratchets with super-hydrophobic microtextures extends quick self-propulsion down to a substrate temperature of 100°C, which exploits the persistence of Leidenfrost state with such coatings. Surprisingly, propulsion is even observed below 100°C, implying that levitation is not necessary to induce the motion. Finally, we model the drop velocity in this novel "cold regime" of self-propulsion.
authors.affiliation: 1] Physique et Mécanique des Milieux Hétérogènes, UMR 7636 du CNRS, ESPCI, 75005 Paris, France [2] Ladhyx, UMR 7646 du CNRS, École Polytechnique, 91120 Palaiseau, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Dupeux
authors.affiliation: 1] Physique et Mécanique des Milieux Hétérogènes, UMR 7636 du CNRS, ESPCI, 75005 Paris, France [2] Ladhyx, UMR 7646 du CNRS, École Polytechnique, 91120 Palaiseau, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Bourrianne
authors.affiliation: 1] Physique et Mécanique des Milieux Hétérogènes, UMR 7636 du CNRS, ESPCI, 75005 Paris, France [2] Ladhyx, UMR 7646 du CNRS, École Polytechnique, 91120 Palaiseau, France.
authors.forename: Quentin
authors.initials: Q
authors.lastname: Magdelaine
authors.affiliation: 1] Physique et Mécanique des Milieux Hétérogènes, UMR 7636 du CNRS, ESPCI, 75005 Paris, France [2] Ladhyx, UMR 7646 du CNRS, École Polytechnique, 91120 Palaiseau, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Clanet
authors.affiliation: 1] Physique et Mécanique des Milieux Hétérogènes, UMR 7636 du CNRS, ESPCI, 75005 Paris, France [2] Ladhyx, UMR 7646 du CNRS, École Polytechnique, 91120 Palaiseau, France.
authors.forename: David
authors.initials: D
authors.lastname: Quéré