Researchers at the University of Tokyo have developed a method to 3D print robotic muscles and ligaments using thermoplastic polyurethane. The team utilized TPU 95A for flexible components and PLA for the main frame, printing the parts on a Prusa XL machine. By adjusting the internal lattice structure, specifically increasing the thickness of the grid bridges from 1.5 mm to 3 mm, the researchers achieved a 28-fold increase in stiffness.
Each robotic leg features six artificial muscles, some of which span two joints to allow for complex movements like simultaneous hip extension and knee flexion. The system uses motors located in the pelvic area to pull cables connected to these muscles. This design eliminates the need for traditional casting and reduces manual assembly, with each muscle requiring 20 to 40 hours to print.
During testing, the robotic legs performed movements with stride lengths of 0.4 m and 0.8 m. The components successfully endured 999 load cycles without tearing, although their stiffness levels shifted over time. The researchers now intend to scale this technology to develop full-sized humanoid robots equipped with integrated sensors and complete body structures.
