Directional wetting: Comparing simulations to experiments
H.P. Jansen, K. Sotthewes, J. van Swigchem, H.J.W. Zandvliet, and E.S. Kooij
Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede, The Netherlands
We present a lattice Boltzmann study of droplets deposited on a surface with alternating hydrophilic and hydrophobic stripes. Three cases are investigated both in experiments and simulations: (i) spreading, (ii) evaporation, and (iii) surface gradient induced droplet motion. The simulations accurately reproduce experimental results, which have shown that droplets on such surfaces adopt an elongated shape due to anisotropic preferential spreading. For evaporation, receding motion first happens in the direction parallel to the stripes. Once the droplet becomes spherical it also starts to recede in the direction perpendicular to the stripes. By changing the relative widths of the stripes, a gradient can be formed changing from predominantly hydrophobic to mostly hydrophilic. This leads to droplet motion under the influence of a surface energy gradient, enabling controlled liquid transport over the surface.
H.P. Jansen, K. Sotthewes, J. van Swigchem, H.J.W. Zandvliet, E.S. Kooij, Phys. Rev. E. 88, 013008 (2013)