Climbing soft robot using re-programmable metamaterial

Buckling-driven metamaterials are increasingly being exploited for novel functionality in soft robotics as shape-adaptation and exotic constitutive behaviour can be tailored by controlling the nonlinearity of individual unit cells. Extensive work has been done on tailoring the post-buckling behaviour of metamaterials through geometry/material modification before fabrication, also known as `modal nudging’. In this work, we demonstrate the re-programmability of metamaterials after fabrication through the use of embedded actuators. To design the metamaterial we use an in-house generalised path-following solver that explores the complete post-critical bifurcation landscape of a buckling-driven latticed metamaterial comprising an elastomeric matrix with an embedded square array of circular holes. With the full bifurcation landscape at hand, and multiple stable states in the post-critical regime, we propose an active modal nudging technique that switches the latticed metamaterial between two distinct configurations---a shearing mode and a polarized mode---through a pair of concentrated forces applied in the central hole. The applied actuation leads to a sudden mode change by means of a snap-through instability. Based on the ability to interchange between two stable states, a soft robotic climber is manufactured and its effectiveness verified through demonstration tests. The conducted work sheds light on programming the behaviour of soft metamaterials through embedded actuators after manufacturing, which will further enrich the design space of mechanical metamaterials and their application in soft robotics.