Programming touch-me-not knot topologies for rapid and diverse leaping and flying motions

Miniature leaping robots are desired to perform fast, programmable, and versatile motions. In this study, we present our approach for harnessing the impulsive unknotting process triggered upon heating millimeter-sized knots made from Kevlar-reinforced liquid crystal elastomer (LCE) composite fibers. The LCE shell with twisted mesogens undergoes torsional deformation, generating an actuation force that overcomes friction, converting the stored elastic energy into kinetic energy for launching tall and rapid leaps with diverse posttakeoff motions depending on the knot topology. By manipulating the bending-twisting coupling and the unknotting numbers, we realize flipping, spinning, and sequential gymnastic in-air motions. We further program posttakeoff flight, including self-return and vertical descent by integrating a wing. Encoding topology and anisotropy provides a rich design space to program soft robots for rapid, agile, and highly efficient motions.