Jamming Metal Sheets Using Electropermanent Magnets for Stiffness Modulation

Soft robots exhibit natural compliance which is desirable in many applications, but often require stiffness modulation techniques when more rigidity is needed. However, many existing stiffening techniques lack portability or fast response times, hindering the ubiquitous adoption of soft robots. Here we introduce a new rapid stiffness modulation method based on magnetism that exhibits portability due to electronic control. This technique jams together thin layers of inherently magnetic metal sheets with a magnetic field generated by electropermanent magnets (EPMs), producing rapid stiffness changes. Quasi-static and dynamic mechanical characterizations for samples with varied layer numbers are presented, highlighting how the magnetic attraction generated by EPMs can be exploited to create a jamming effect. Stiffness increases of up to 68% and energy absorptions of up to 113 mJ were found during quasi-static and dynamic characterizations, respectively. Finally, we demonstrate how this jamming technique can be used in a haptic feedback application and to play a miniaturized version of the game of Skee-Ball.