E.S. Kooij, H.P. Jansen, H.J.W. Zandvliet
Univ. Twente, MESA+ Inst. Nanotechnology, Netherlands
pp. 480 - 483
Keywords: directional wetting
The ability to control liquids at surfaces is highly relevant for many application areas, including for example the performance and reliability of inkjet nozzles. Generally, the wettability of solid substrates can be modified both by morphological micro- and nanostructuring as well as by chemical functionalization. In this presentation we discuss the potential of chemically defined patterns to control dynamic liquid behaviour on morphologically flat surfaces. The spreading of droplets on chemically patterned surfaces consisting of alternating hydrophilic and hydrophobic micron-wide stripes is studied using high-speed imaging of the shape evolution of the deposited droplets. Asymmetric droplet shapes are analysed in relation to the relative and absolute stripe widths. To provide a benchmark for the analysis of our results, we use the multicomponent multiphase lattice Boltzmann method (LBM). This method enables modelling of dynamic behaviour and therewith identification of kinetics effects. The final droplet shape exhibits unique scaling behaviour; the aspect ratio as well as contact angles in the directions parallel and perpendicular to the stripes only depend on the relative hydrophobicity. Additionally, measurements using a high-speed camera while varying the viscosity of the liquid reveal the importance of kinetics involved in the formation of the asymmetric droplets.