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Materials

Soft Robot Walks

Harvard scientists create floppy, all-polymer crawler capable of navigating obstacles

by Lauren K. Wolf
December 5, 2011 | APPEARED IN VOLUME 89, ISSUE 49

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Credit: Proc. Natl. Acad. Sci. USA
Wiggling its limbs and spine, an all-polymer robot moves forward about half an inch in one step; the inset shows which limbs are pressurized (green) and which ones are not (red) during the cycle.
08949-scicon-robotweb.jpg
Credit: Proc. Natl. Acad. Sci. USA
Wiggling its limbs and spine, an all-polymer robot moves forward about half an inch in one step; the inset shows which limbs are pressurized (green) and which ones are not (red) during the cycle.

Not all robots must contain heavy metal skeletons and parts such as mechanical joints, according to a research team at Harvard University. Led by George M. Whitesides, the scientists have constructed an all-polymer robot that can crawl and undulate backward and forward, even navigating obstacles (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1116564108). Fabricated with soft-lithography techniques used to build microfluidic devices, the robot moves via a series of inflatable chambers embedded between layers of the stretchy commercial elastomer Ecoflex and the more rigid plastic polydimethylsiloxane (C&EN, Feb. 14, page 36). The researchers sequentially inflate the chambers in the arms and spine of the tetrapod robot to propel it along. Because of its flexibility, the 0.9-cm-thick robot is able to pass below a glass plate elevated only 2 cm from a surface. The soft crawler has a number of favorable qualities, including its simple, lightweight design, the researchers say. But other materials will be needed to improve its durability and load-bearing capacity. “Soft robotics,” they write, “may, thus, initially be a field more closely related to materials science and to chemistry than to mechanical engineering.”

DOING THE LIMBO
Credit: Proc. Natl. Acad. Sci. USA/C&EN
In this clip, a starfish-inspired robot, made from elastomeric polymers, crawls, undulates, and creeps under an obstacle.
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