ABSTRACT
Having been evolving for billions of years, many creatures in the nature have various unusual abilities to survive in tough conditions. Bio-inspired by nature, designing and fabricating smart functional materials have become a very promising field of research. Wettability is the one of the most important subdisciplines of this field to prepare bio-inspired smart materials. Some biological surfaces show special wettability features such as lotus, water strider,1 rose, butterfly, spider silk, rice leaf, and desert beetle. For example, the capture silk of the cribellate spider (Uloborus walckenaerius) has a water-collecting ability resulting from a unique fiber structure that is formed after wetting with the “wet-rebuilt” fibers characterized by periodic spindle knots made of random nanofibrils and separated by joints made of aligned nanofibrils. These structural features result in a surface energy gradient between the spindle knots and the joints and also in a difference in Laplace pressure, with both factors acting together to achieve continuous condensation and directional collection of water drops around spindle knots. We named it as “Effect of Spider Silk.” Submillimeter-sized liquid drops have been driven
by surface energy gradients or a difference in Laplace pressure.
