Researchers have combined 3D printing advances and gradient material strategy to build a flexible robot that is devoid of the traditional rigidity of metallic components, but is also extremely durable.
Unlike traditional robots that are made using components and rigid materials including metal and hydraulic parts, researchers at Wyss Institute researchers and their collaborators have been able to use a novel three-dimensional printing strategy to construct entire robots in a single build that incorporate this biodesign principle.
One of the major challenges with designing flexible robots that could assist humans in search and rescue operations is integrating soft materials with requisite rigid components that power and control the robot’s body. Further, another issue is the stress concentration and structure integrity at interfaces of soft and rigid material.
Based on the understanding on how organisms solve this problem by self-assembling their bodies in a way that produces a gradual transitioning from hard to soft parts, the team has managed to build complex and robust structures that can’t be achieved using conventional nuts and bolts manufacturing.
A proof-of-concept prototype- a soft-bodied autonomous jumping robot reported in the July 10 issue of Science – was 3D printed layer upon layer to ease the transition from its rigid core components to a soft outer exterior using a series of nine sequential material gradients.
Researchers used additive manufacturing to create a single body fabricated with nine sequential layers of material, increasing in stiffness from rigid to soft towards the outer body. Thanks to a gradient material strategy, researchers have managed to greatly reduce stress concentrations typically found at the interfaces of soft and rigid components thereby creating an extremely durable robot.
With the expertise of study co-author and Wyss Institute Senior Research Scientist James Weaver, Ph.D., who is a leader in high-resolution, multi-material 3D printing, the team was able to 3D print the jumping robot’s body in one single 3D printing session.
Usually, 3D printing is only used to fabricate parts of robots, and is only very recently being used to print entire functional robots. And this jumping robot is the first entire robot to ever be 3D printed using a gradient rigid-to-soft layering strategy.
For the power, researchers have used explosive actuator on its body that harnesses the combustion energy of butane and oxygen instead of wires or tethers. It utilizes three tilting pneumatic legs to control the direction of its jumps, and its soft, squishy exterior reduces the risk of damage upon landings, makes it safer for humans to operate in close proximity, and increases the robot’s overall lifespan.
The soft bodied robot was developed based on previous combustion-based robots designed by co-senior author George Whitesides, Ph.D., who is a Wyss Institute Core Faculty member and the Woodford L. and Ann A. Flowers University Professor at Harvard University.
“Traditional molding-based manufacturing would be impractical to achieve a functionally-graded robot, you would need a new mold every time you change the robot’s design. 3D printing manufacturing is ideal for fabricating the complex and layered body exhibited by our jumping robot,” said Nicholas Bartlett, a co-first author on the study and a graduate researcher in bioinspired robotics at the Wyss Institute and Harvard SEAS.
As compared to traditional mold manufacturing, which uses fixed molds, the nature of 3D printing facilitates rapid design iterations with utmost ease, allowing faster prototyping throughout development.