Soft Robot Walks

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.”