Temperature-triggered directional motion of tiny water droplets on bioinspired fibers in humidity.

We designed a kind of smart bioinspired fiber using the N-isopropyl-acrylamide (NIPAAm) polymer, with roughness and curvature features similar to those of wetted spider silk. The motion of tiny water droplets can be manipulated reversibly in directions by the effective cooperation of multi-gradients such as roughness, curvature and temperature-responsive wettability.