  Soft actuators have shown great advantages in compliance and morphology
matched for manipulation of delicate objects and inspection in a confined
space. There is an unmet need for a soft actuator that can provide torsional
motion to e.g. enlarge working space and increase degrees of freedom. Towards
this goal, we present origami-inspired soft pneumatic actuators (OSPAs) made
from silicone. The prototype can output a rotation of more than one revolution
(up to 435{\deg}), more significant than its counterparts. Its rotation ratio
(=rotation angle/ aspect ratio) is more than 136{\deg}, about twice the largest
one in other literature. We describe the design and fabrication method, build
the analytical model and simulation model, and analyze and optimize the
parameters. Finally, we demonstrate the potentially extensive utility of the
OSPAs through their integration into a gripper capable of simultaneously
grasping and lifting fragile or flat objects, a versatile robot arm capable of
picking and placing items at the right angle with the twisting actuators, and a
soft snake robot capable of changing attitude and directions by torsion of the
twisting actuators.
