  Pneunets are the primary form of soft robotic grippers. A key limitation to
their wider adoption is their inability to grasp larger payloads due to objects
slipping out of grasps. We have overcome this limitation by introducing a
torsionally rigid strain limiting layer (TRL). This reduces out-of-plane
bending while maintaining the gripper's softness and in-plane flexibility. We
characterize the design space of the strain limiting layer for a Pneu-net
gripper using simulation and experiment and map bending angle and relative grip
strength. We found that the use of our TRL reduced out-of-plane bending by up
to 97.7% in testing compared to a benchmark Pneu-net gripper from the Soft
Robotics Toolkit. We demonstrate a lifting capacity of 5kg when loading using
the TRL. We also see a relative improvement in peak grip force of 3N and
stiffness of 1200N/m compared to 1N and 150N/m for a Pneu-net gripper without
our TRL at equal pressures. Finally, we test the TRL gripper on a suite of six
YCB objects above the demonstrated capability of a traditional Pneu-net
gripper. We show success on all but one demonstrating significant increased
capabilities.
