  We investigate the influence of particle stiffness on the grasping
performance of granular grippers, a class of soft robotic effectors that
utilize granular jamming for object manipulation. Through experimental analyses
and X-ray imaging, we show that grippers with soft particles exhibit improved
wrapping of the object after jamming, in contrast to grippers with rigid
particles. This results in significantly increased holding force through the
interlocking. The addition of a small proportion of rigid particles into a
predominantly soft particle mixture maintains the improved wrapping but also
significantly increases the maximum holding force. These results suggest a
tunable approach to optimizing the design of granular grippers for improved
performance in soft robotics applications.
