  One of the many secrets to the success and prevalence of insects is their
versatile, robust, and complex exoskeleton morphology. A fundamental challenge
in insect-inspired robotics has been the fabrication of robotic exoskeletons
that can match the complexity of exoskeleton structural mechanics. Hybrid
robots composed of rigid and soft elements have previously required access to
expensive multi-material 3D printers, multi-step casting and machining
processes, or limited material choice when using consumer-grade fabrication
methods. Here we introduce a new design and fabrication process to rapidly
construct flexible exoskeleton-inspired robots called flexoskeleton printing.
We modify a consumer-grade fused deposition material (FDM) 3D printer to
deposit filament directly onto a heated thermoplastic base layer which provides
extremely strong bond strength between the deposited material and the
inextensible, flexible base layer. This process significantly improves the
fatigue resistance of printed components and enables a new class of
insect-inspired robot morphologies. We demonstrate these capabilities through
design and testing of a wide library of canonical flexoskeleton elements;
ultimately leading to the integration of elements into a flexoskeleton walking
legged robot.
