Bioinspired mechanisms and actuation of soft robotic crawlers

Inspired by soft-bodied animals, scientists and roboticists have explored and created soft materials and robots in this last decade to mimic the functionality and behaviour of soft crawling animals. Such effort has originated from the unique ability of soft structures to crawl effectively in complex natural environments. As a result, there is growing interest in the design of highly functional soft robotic crawlers through the creation of new flexible functional materials, understanding the underlying science of crawling mechanisms and employing advanced actuation strategies. This review investigates the current state-of-the-art in this fascinating area to demonstrate the nexus between materials, mechanisms, actuation and applications. Bioinspired crawling mechanisms of soft crawlers are initially outlined, which includes two-anchor peristaltic and serpentine crawling and undulatory motion as analogues to caterpillars, worms and snakes respectively. The fabrication and use of new materials in the design of soft crawlers is also discussed, along with the exploitation of actuation mechanisms to achieve specific crawling locomotion. Finally, insights into future research directions are outlined.