A new material may allow for development of a "soft robot" that could reconfigure its shape and move using its own internally generated power, scientists say. Typically, robots are formed from bulky, stiff materials and require connections to external power sources but these features limit their dexterity and mobility.
By developing a new computational model, researchers at the University of Pittsburgh's Swanson School of Engineering have designed a synthetic polymer gel that can utilise internally generated chemical energy to undergo shape-shifting and self-sustained propulsion. "Movement is a fundamental biological behaviour, exhibited by the simplest cell to human beings. It allows organisms to forage for food or flee from prey," said study co-author Anna C Balazs, the Swanson School's Distinguished Professor of Chemical and Petroleum Engineering. "But synthetic materials typically don't have the capability for spontaneous mechanical action or the ability to store and use their own energy, factors that enable directed motion," Balazs said.
"Moreover in biology, directed movement involves some form of shape changes, such as the expansion and contraction of muscles. So we asked whether we could mimic these basic interconnected functions in a synthetic system so that it could simultaneously change its shape and move," Balazs said. Balazs and team were inspired by the single-celled organism euglena mutabilis, which processes energy to expand and contract its shape in order to move.
To mimic the euglena's mobility, researchers looked to polymer gels containing spirobenzopyran (SP) since these materials can be morphed into different shapes with the use of light, and to Belousov-Zhabotinsky (BZ) gels, a material first fabricated in the late 1990s that not only undergoes periodic pulsations, but also can be driven to move in the presence of light. "The BZ gel encompasses an internalised chemical reaction so that when you supply reagents, this gel can undergo self-sustained motion," said Olga Kuksenok, co-author of the study published in the journal Scientific Reports.
"Although researchers have previously created polymer chains with both the SP and BZ functionality, this is the first time they were combined to explore the ability of "SP-BZ" gels to change shape and move in response to light," Kuksenok said. Balazs and Kuksenok noted that these systems are distinctive because they not only undergo self-bending or folding, but also self-propelled motion. Balazs said that these SP-BZ gels could enable the creation of small-scale soft robotics for microfluidic devices that can help carry out multi-stage chemical reactions.
