Dynamic Wetting by Viscous Liquids: Effects of Softness, Wettability and Curvature of the Substrate and Influence of External Electric Fields

摘要: The wetting of solid surfaces by liquids is commonly observed in nature, and it also a key to number industrial applications biological processes. In the past two centuries, most studies about were devoted mainly equilibrium situations thus static measurements. However, cases dynamic more relevant has received less attension. goal this thesis study effects softness, wettability curvature substrate influence external electric fields on viscous liquids. The contains main parts. first part focuses early simple types that show different complexity: flat viscoelastic substrates highly curved microparticles. On substrates, novel stage dominated inertia was found. dynamics characterized radius, r=K't^α, following power law similarly as rigid surfaces, with exponent α only depending surface wettability. After inertial stage, spreading slows down enters another viscoelasticity substrate. transition between controlled “softness”. A theory developed Prof. Martin E.R. Shanahan explain these findings. An during snap-in process, i.e. wetting, single colloidal particles into large water drops. time dependent capillary force inertia, but independent contrast, larger for hydrophilic smaller hydrophobic particles. scaling model proposed describe or individual colloids. The second liquids. First, drops aqueous electrolyte solutions various wettable driven electrostatic forces, which termed “electrospreading”, investigated. It found electrospreading electrostatics. not applied potential, concentration solutions. energy stored double layer near solid-liquid interface served an additional driving drop spreading. Based molecular simulation done Dr. Chunli Li, presented dynamics. Finally, systematic carried out. Both liquid viscosity well stage. During effective mass affected viscosity. This results slower speed Viscous did take place all those contact angles than critical value, depended again experimental observations.