Infrared Active Actuators Mimicking Locomotion Patterns of Soft-Bodied Invertebrates

Soft-bodied invertebrates such as caterpillars and leeches transduce muscle contraction and relaxation sequences toward their locomotion ability. Mimicking these complex locomotory patterns to design soft robots with predictable gaits remains a significant challenge to date. Here we report infrared responsive actuators based on graphite ink-coated low-density polyethylene (LDPE) sheets, capable of performing caterpillar-like crawling and somersaulting motion with high predictability, reversibility and rapidity. By strategically patterning graphite ink on LDPE and performing thermal imaging, we show that the heat generation across actuators upon photoirradiation correlates to actuation response time and magnitude. These actuators achieve a curvature angle of 270° in 9 s and return consistently to their original state, with over 70% improvement in the restoration time. Similarly, somersaulting (in 5 s) and wave-like crawling (30.8 mm/min) achieve over 60% improvement in the actuation speed. Our findings therefore open possibilities of designing untethered actuators with high precision and adaptable locomotion modes.