Tiny water droplets have been made to move in a controlled direction along threads of synthetic spider webs.
Lei Jiang at the Chinese Academy of Sciences in Beijing, Yongmei Zheng of the Beijing University of Aeronautics and Astronautics and their colleagues constructed webs from different polymers and observed the spontaneous movement of micrometre-sized water droplets on their strands. On polymers with a rough surface, drops always migrate towards and coalesce at knots in the silk, regardless of its hydrophobicity. But if the surface is smoother they move away from the knots if the polymer is hydrophobic, and towards them if it is hydrophilic.
These results should allow the design of devices that can drive water droplets in a controllable manner.