4D Printing Inflatable Silicone Structures

This article details steps in creating low-power artificial muscles using 3D printing. It describes a manufacturing system that can be used to fabricate seamless tubular dielectric elastomer actuators (DEA), for eventual use in biorobotic devices. The focus is on producing passive elastomeric components of DEA and the dimensional changes that occur after printing is complete. A four-axis printing system is described, capable of spray depositing multilayer tubular silicone membranes onto an air-permeable mandrel. Mechanical strain was imparted in the membranes by means of inflation. A laser measurement system was constructed to act as a 3D scanner, which measured the shape of the inflated balloon.'' The surface shape was reconstructed in software using the parametric modeling tool Grasshopper. Seamless auxetic tessellations were calculated across the entire surface, and then converted to CNC GCode. These toolpaths were then physically extruded over the surface of the balloon, stacked five layers high. When the extruded silicone structure was completely cured, the pneumatic strain was released, allowing the structure to collapse evenly. The compression in the printed structure was balanced by the tension in the stretched membranes, thus producing a minimum energy structure.