Recently, there has been much interest in using lubricated surfaces to achieve extreme liquid repellency: a foreign droplet immiscible with the underlying lubricant layer was shown to slide o at a small tilt angle <5◦ . This behaviour was hypothesized to arise from a thin lubricant overlayer film sandwiched between the droplet and solid substrate, but this has not been observed experimentally. Here, using thin-film interference, we are able to visualize the intercalated film under both static and dynamic conditions. We further demonstrate that for a moving droplet, the film thickness follows the Landau–Levich–Derjaguin law. The droplet is therefore oleoplaning—akin to tyres hydroplaning on a wet road—with minimal dissipative force and no contact line pinning. The techniques and insights presented in this study will inform future work on the fundamentals of wetting for lubricated surfaces and enable their rational design.
We thank K.-C. Park, C. N. Kaplan and H. A. Stone for fruitful discussions. The work was supported by the Office of Naval Research, US Department of Defense, under MURI Award No. N00014-12-1-0875. J.V.I.T. was supported by the European Commission through the Seventh Framework Programme (FP7) project DynaSLIPS (project number 626954). We acknowledge the use of the facilities at the Harvard Center for Nanoscale Systems supported by the NSF under Award No. ECS-0335765 and at the Harvard Materials Research Science and Engineering Center (MRSEC) under Award No. DMR-1420570.