Magnetic field assisted droplet manipulation on a soot-wax coated superhydrophobic surface of a PDMS-iron particle composite substrate

We report controlled motion of aqueous droplets on soot-wax coated superhydrophobic surface of a PDMS-iron particle composite substrate. The surface profile around a droplet is altered due to magnetic force acting on the iron particles embedded in the substrate, which leads to droplet motion. The contact angle and roll off angle depend on the soot deposit time and particle distribution. Endurance test is performed to confirm stability of the surface. The deformation behaviour of the substrate is studied with particle size, surface to magnet gap and the cone angle of the magnet. The proposed surface could find applications in the manipulation of sample drops in biological and chemical assays.