Sol-gel transition programmed self-propulsion of chitosan hydrogel.

Active soft materials exhibit various dynamics ranging from boat pulsation to thin membrane deformation. In the present work, in situ prepared ethanol-containing chitosan gels propel in continuous and intermittent motion. The active life of the organic material loaded to the constant fuel level follows a linear scaling, and its maximal velocity and projection area decrease steeply with chitosan concentration. A thin propelling platelet forms at low polymer content, leading to the suppression of intermittent motion. Moreover, the fast accelerating thin gels can split into a crescent and circular-like shape or fission into multiple asymmetric fragments.