Automated Fabrication of Elastomeric Prepregs for Soft Robotics Applications

Abstract

Fluidic elastomer soft robots typically consist of a top and a strain-limiting bottom part. Both parts are usually cast and then glued together. Elastomeric prepregs, which can be stored at low temperatures for several months without significant cross-linking, simplify this manufacturing process. A cured top part of an arbitrary shape is placed on the wet prepreg, which later forms the strain-limiting layer, and the actuator is finally cured in an oven. Herein, a machine is designed and developed that automatically produces prepregs. Three different concepts are realized in a modular prototype: direct roller application, reverse roller application, and application with slot dies. Experiments show that the direct and the reverse roller application concepts are both suitable for the automated production of prepregs, where the latter one may be preferred due to the smaller number of contact surfaces. Three different textiles (polyester/cotton-blended fabric, nylon fabric, and fleece) are impregnated with the reverse roller application concept using Sylgard 184 and stored at À25 C for 12 days. Using these prepregs, soft bending actuators are manufactured and tested for their functionality. Long-term fatigue tests show that only actuators produced with fleece prepregs are durable, without any signs of delamination. Soft robotics is an emerging field of research that can complement conventional hard robotics. Soft robots consist almost entirely of soft materials, whereby their Young's moduli typically lie in the range of biological structures (10 4-10 9 Pa). [1] They often mimic the movements of animals without endo-or exoskeletons, [2] are usually cheaper than rigid robots, can move better in difficult terrain, [2,3] and grasp fragile objects (e.g., an egg). [4] Pneumatically operated soft robots are resistant to many external influences, such as tensile and compressive stresses, hammer strikes, [5] and high temperatures, [3] but are vulnerable to cuts and punctures. [6] Many soft robots consist of room temperature-vulcanizing two-component (RTV-2) elastomers and use