Bilayer microbot powered by humidity

Soft Robots Many plant seeds, including pine cones, open or close in response to changes in humidity. Inspired by these hygroexpansive seeds, Shin et al. fabricated a “hygrobot.” The hygrobot was composed of a film that was responsive to environmental humidity attached to a film that was not. Aligned nanofibers in the responsive layer swelled when humidity increased, causing the bilayer structure to bend. Decreasing humidity shrunk the moisture-responsive layer, straightening out the robot. Legs with asymmetric friction coefficients converted the bending into directional motion on a moist surface. Sci. Robot. 3 , eaar2629 (2018).