Formation of gears through buckling multilayered film–hydrogel structures

We investigate the buckling instability of a multilayered hydrogel tubular structure under shrinking using both analytical method and computer simulation. It is found that the mechanical stabilities enable three types of post-buckling configurations with regular patterns; that is, the formation of inner teeth alone, the formation of outer teeth alone, and the formation of both inner and outer teeth. The critical conditions and the post-buckling configurations have been predicted. The controlled post-buckling structures may be used as basic building components for smart gear systems.