Printed silicone pneumatic actuators for soft robotics

A silicone-based embedded additive manufacturing method, called Rapid Liquid Printing (RLP) is applied to the fabrication of soft pneumatic actuators to investigate and demonstrate its potential for applications in soft robotics. This process is shown to improve on traditional silicone casting and additive manufacturing of elastomers, the two main manufacturing methods used in soft robotics, by offering complete design freedom at high speed without compromising material properties. Contrary to existing silicone printing techniques, RLP uses commercially available materials and a simple robotic arm or gantry CNC machine to print large structures in a supporting gel at a rate of four times the speed of state-of-the-art multi-material printers. To determine the applicability of RLP for soft robotics and in the production of soft actuators, a benchmark testing procedure for pneumatic linear actuators is developed. A linear actuator design is manufactured using three techniques: silicone casting, multi-material polyjet printing, and RLP. These actuators are tested for elongation and fatigue behavior through cycling and force. Rapid liquid printed actuators perform comparably for elongation range and exceed the two other methods for repeatability and longevity. A complex, multi-chambered demonstrator is designed from the actuator geometry to showcase the advantages of RLP versus existing silicone printing methods including speed, scale, and part complexity. These results demonstrate the applicability of RLP to the field of soft robotics and pave the way for its further implementation in the manufacturing of soft pneumatic actuators.