Sticky Slippy Hemi-solids

A textured solid infused with a liquid comprises a class of materials in between a liquid and a solid. These hemi-solids may exhibit very little adhesion due to the lack of pinning sites. Here we show that alongside being `slippery’, these surfaces can be `sticky‘ as well. We investigate this by taking an elementary system consisting of a millimetric water droplet placed between two surfaces, infused with oils of different viscosities. We find that if the upper plate viscosity is greater, then by pulling the upper plate at sufficiently high velocities it is possible to detach the droplet completely off the bottom plate. The captured droplet can be subsequently deposited on the lower plate by bringing it in contact and pulling the plates apart slowly. In this talk, we will discuss the physics of such a viscous tweezer and the parameters that govern it.