Superhelical locomotion of an active gel driven by scroll waves

Understanding the principles of self-organized motion in active materials can provide valuable insights into complex biological phenomena such as collective cell migration and bacterial locomotion. Furthermore, the ability to control and manipulate the motion of soft materials through stimuli opens up exciting possibilities for the design of novel soft robots capable of autonomous movement and adaptation. Here, we report the superhelical self-propulsion of a model Belousov-Zhabotinsky (BZ) self-oscillating gel in three-dimensional space driven by scroll waves under gradient illumination. A Transition from planar epicyclic locomotion to superhelical and irregular locomotion is obtained in nonilluminated and illuminated media, respectively. By increasing the illumination gradient, the wave dynamics becomes unstable and both ends of the wave filament drift randomly, causing three-dimensional irregular locomotion. The simulated locomotion can be fit with a two-frequency superhelix, similar to the locomotion trajectories of entities such as Euglena gracilis, sperm cells, and Chlamydomonas reinhardtii.