  This work introduces a novel technique for fabricating functional robots
using 3D printers. Simultaneously depositing photopolymers and a non-curing
liquid allows complex, pre-filled fluidic channels to be fabricated. This new
printing capability enables complex hydraulically actuated robots and robotic
components to be automatically built, with no assembly required. The technique
is showcased by printing linear bellows actuators, gear pumps, soft grippers
and a hexapod robot, using a commercially-available 3D printer. We detail the
steps required to modify the printer and describe the design constraints
imposed by this new fabrication approach.
