Soft robotic actuators can be distinguished according to their overall deformation when actuated. One of these actuators shows a twisting deformation upon inflation. While in literature twisting actuator designs have been proposed that use spiraling constraints to redirect volumetric expansion, the soft robotics group introduced a planar design.
Key benefits of this design is that it can be made out of a single material, and is compatible with (soft) lithography. This greatly enhances the potential for further scaling down and merging with flexible electronics. The video below shows the deformation of such a twisting actuator with outer dimension of 7mm x 17 mm x 0.65mm, made using soft lithography.
Four of these twisting actuators have been combined to form a soft robotic platform with 2 degrees of freedom, which is capable of deflecting the central end effector from -25° to 25° over two perpendicular axes.