Reconfigurable Auxetic Devices (RADs) for Robotic Surface Manipulation

Robotic surfaces traditionally use materials with a positive Poisson's ratio to push and pull on a manipulation interface. Auxetic materials with a negative Poisson's ratio may expand in multiple directions when stretched and enable conformable interfaces. Here we demonstrate reconfigurable auxetic lattices for robotic surface manipulation. Our approach enables shape control through reconfigurable locking or embedded servos that underactuate an auxetic lattice structure. Variable expansion of local lattice areas is enabled by backlash between unit cells. Demonstrations of variable surface conformity are presented with characterization metrics. Experimental results are validated against a simplified model of the system, which uses an activation function to model intercell coupling with backlash. Reconfigurable auxetic structures are shown to achieve manipulation via variable surface contraction and expansion. This structure maintains compliance with backlash in contrast with previous work on auxetics, opening new opportunities in adaptive robotic structures for surface manipulation tasks.