Soft Printable Robots with Flexible Metal Endoskeleton

Recent advancements in soft robotics have seen the rapid development of soft grippers for industrial pick-and- place applications. They are however ill-suited to bear heavy loads due to their compliant nature. Paradoxically, researchers have sought to increase the stiffness of soft grippers to improve load-bearing capabilities. Unfortunately, contemporary soft ac- tuators with variable stiffness are fabricated using manual processes and their performance is subject to an individual’s mastery. They are hence not reliable for long-term industrial use. In this paper, we present our work on a 3D-printed metal- endoskeleton-reinforced actuator (MERA) for industrial pick- and-place applications. We also highlight the fabrication pro- cesses needed to recreate it repetitively. Using stainless steel splints (SSS), we demonstrate that MERA is able to modulate its stiffness at selective junctures for stable and effective grasp- ing. We also describe our design rationale with a qualitative mathematical model and validate its performance quantitatively using a finite element model, which is further investigated in the following fatigue test. In our experiments, the MERA equipped with SSS is able to output a peak tip force of 8N, which is a 291% increase compared to the one without metallic reinforcement. In addition, an increase of 76.5% in gripping load and a maximum holding force per actuator of 13.8N are realized through the stiffness tuning of a MERA-Gripper. Despite significantly improving load-bearing capabilities, the actuator manages to retain an overall low profile with a weight of 82g. Finally, we adapted the MERA into a reconfigurable gripper and tested its grasping capabilities on objects of various shapes, sizes, and weights.