3D printing stretchable and compressible porous structures by polymerizable emulsions for soft robotics

Abstract

UV-curable 3D printing compositions for the fabrication of stretchable and flexible porous structures for soft robotics are presented. The stereolithography-based printing compositions are water-in-oil (W/O) emulsions in which water droplets are the pore-forming material, and the continuous phase is a stretchable polyurethane diacrylate (PUA). The porosity of the printed objects is controlled by the material's micro-porosity and by the macro-porosity obtained by a cellular design. The mechanical behavior can be tailored by the composition of the emulsion, providing both compliance and strength while utilizing a unique optimization methodology for fitting the ink to the 3D printer. This approach enables developing materials having superior mechanical properties, with the highest reported elongation-at-break for 3D printed porous structures, 450%. The emulsion-based printing compositions were utilized for fabricating a soft robotic gripper with unique actuation performance that could not be obtained with commonly used materials.