Autonomously Repeating High-Speed Motions in Soft Materials

Soft materials, such as polymer gels, have long been realized as a potential platform for actuation in robotic systems; however, several challenges have limited their integration into translatable technologies. In particular, soft matter actuators are slow, unable to generate significant power, and typically require external intervention to initiate multiple, sequential actuation events. Recent results from our research group have demonstrated the ability to harness evaporation-induced stresses to initiate snap-through transitions, which can generate high velocity, high acceleration motions with swollen elastomers. Importantly, we discovered that certain combinations of materials properties and geometries allowed for the system to undergo multiple, consecutive snap-through transitions without external intervention. Here, we review these previous findings and introduce our latest research results focused on understanding the structure-property relationships that control the total energy flow of these self-repeating, high velocity events. The lessons learned are built upon the materials science principles that have been developed as part of a multi-university team, which takes inspiration from examples in nature including mantis shrimp and trap-jaw ants. These organisms use Latch-Mediated Spring Actuation (LaMSA) to achieve high power, impulsive movements by integrating actuators, elastic elements, and stability-mediating latches. The strategies and results discussed provide new insight into how polymer properties can combine with purposeful structural design to achieve complex, energy-efficient tasks, which can be used in the development of microscale robots.