The ability of insects to walk upside on ceilings has inspired stories of human flies and attempts to produce biosynthetic materials with similar properties. How do insects adhere to a surface? The legs of many insects contain hair covered pads. The dense hairs and can flex to provide more contact area with uneven surfaces. The adhesive force is proportional to the contact area between two surfaces.
However, insects can generate adhesive forces much greater than that attributed to dry adhesion. Some insect adhesive hairs have pores that connect to a liquid reservoir inside the insect. The hairs secrete tiny amounts of liquid that wet the hairs of the pad and a surface forming a liquid bridge. The liquid is cohesive because of hydrogen bonding and must be stretched to break contact between the pad and the surface. This “wet adhesion” can be orders of magnitude larger than dry adhesion.
A group of scientists* studied adhesion in arboreal ants and created a biosynthetic capable of wet adhesion by delivering liquid from a reservoir through micropores. The biosynthetic proved the principle of wet adhesion, adhering much more strongly that the dry material.
Studies of insects are improving our understanding of adhesion and is leading to new products.
*Longjian Xue, Alexander Kovalev, Anna Eichler-Volf, Martin Steinhart & Stanislav N. Gorb. 2015. Humidity-enhanced wet adhesion on insect-inspired fibrillar adhesive pads. NATURE COMMUNICATIONS 6:6621