Self-Folding “Rollbot” Paves the Way for Fully Untethered Soft Robots


This 3D-printed soft robotic system is motivated by origami and can move and alter shape inresponse to external stimuli, paving the way for fully untethered soft robots. (Image thanks to Lori K. Sanders/Harvard SEAS)

Most of soft robots today depend on external power and control, keeping them connected to off-board systems or rigged with difficult parts. Now, scientists from the Harvard John A. Paulson School of Engineering and Applied Sciences(SEAS) and Caltech have actually established soft robotic systems, motivated by origami, that can move and alter shape in reaction to external stimuli, paving the way for fully untethered soft robots. 

The research study is released in Science Robotics. 

“The ability to integrate active materials within 3D-printed objects enables the design and fabrication of entirely new classes of soft robotic matter,” stated Jennifer A. Lewis, the Hansjorg Wyss Teacher of Biologically Motivated Engineering at SEAS and co-lead author of the research study. 

Lewis is likewise a Core Professor at the Wyss Institute for Biologically Motivated Engineering at Harvard.

The scientists relied on origami to produce multifunctional soft robots. Through consecutive folds, origami can encode several shapes and performances in a single structure. Utilizing products referred to as liquid crystal elastomers that alter shape when exposed to heat, the research study group 3D-printed 2 kinds of soft hinges that fold at various temperature levels and hence can be set to fold in a particular order. 

“With our method of 3D printing active hinges, we have full programmability over temperature response, the amount of torque the hinges can exert, their bending angle, and fold orientation. Our fabrication method facilitates integrating these active components with other materials,” stated Arda Kotikian, a college student at SEAS and the Graduate School of Arts and Sciences and co-first author of the paper. 

“Using hinges makes it easier to program robotic functions and control how a robot will change shape. Instead of having the entire body of a soft robot deform in ways that can be difficult to predict, you only need to program how a few small regions of your structure will respond to changes in temperature,” stated Connor McMahan, a college student at Caltech and co-first author of the paper. 

To show this approach, Kotikian, McMahan, and the group constructed numerous soft gadgets, consisting of an untethered soft robot nicknamed the “Rollbot.” The Rollbot starts as a flat sheet, about 8 centimeters long and 4 centimeters large. When put on a hot surface area, about 200°C, one set of hinges folds and the robot curls into a pentagonal wheel. 

Another set of hinges is embedded on each of the 5 sides of the wheel. A hinge folds when in contact with the hot surface area, moving the wheel to rely on the next side, where the next hinge folds. As they roll off the hot surface area, the hinges unfold and are prepared for the next cycle.

“Many existing soft robots require a tether to external power and control systems or are limited by the amount of force they can exert. These active hinges are useful because they allow soft robots to operate in environments where tethers are impractical and to lift objects many times heavier than the hinges,” stated McMahan.

Another gadget, when positioned in a hot environment, can fold into a compact folded shape looking like a paper clip and unfold itself when cooled. 

“These untethered structures can be passively controlled,” stated Kotikian. “In other words, all we need to do is expose the structures to specific temperature environments and they will respond according to how we programmed the hinges.” 

While this research study just concentrated on temperature level actions, liquid crystal elastomers can likewise be set to react to light, pH, humidity and other external stimuli. 

“This works demonstrates how the combination of responsive polymers in an architected composite can lead to materials with self-actuation in response to different stimuli. In the future, such materials can be programmed to perform ever more complex tasks, blurring the boundaries between materials and robots,” stated Chiara Daraio, Teacher of Mechanical Engineering and Applied Physics at Caltech and co-lead author of the research study. 

This research study was co-authored by Emily C. Davidson, Jalilah M. Muhammad, and Robert D. WeeksIt was supported by Army Research study Workplace, and Harvard Products Research Study Science and Engineering Center through the National Science Structure, and the NASA Space Technology Research Study Fellowship.

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