Control of Liquids by Surface Energies

Our every day experience of handling liquids is strongly linked to the presence of gravity. In a zero gravity environment, as realized during parabola flights or in space crafts, it is almost impossible to pour water from a bottle into a glass. A close look at a glass of water already reveals the influence of interfacial energies: the curvature of the water meniscus bends up close to its rim due to the high wettability of clean glass surfaces by water. When compartmentalized into structures smaller than a characteristic length being typically on the order of 1 mm gravity becomes irrelevant and interfacial energies dominate both the statics and dynamics of a liquid down to a length scale of about 10 nm [1].

The strong impact of interfacial energies on the morphology of submillimeter- sized wetting droplets can be utilized to control the position and the shape of tiny amounts of liquid on specifically designed substrates.