New 3D-printed muscle is the strong, sensitive type

One of the biggest challenges in soft robotics is getting a robot to move without rigid motors or hard circuitry that restrict the robot’s range of motion. Liquid crystal elastomers (LCE) are powerful and promising polymers that are known to bend or shrink in response to heat and that can serve as artificial muscles, also called actuators. Now a team of researchers led by Shuo Li at Cornell University has taken LCE artificial muscles a step further by developing a way to 3D print a soft actuator that can not only crawl, grab things, and lift heavy weights, but also provide feedback on those actions, opening the door for a more controllable soft robot (Sci. Adv. 2021, DOI: 10.1126/sciadv.abg3677). The team used digital light processing, a 3D-printing technique, to fabricate the muscle layer by layer and embed light-emitting diodes (LEDs). The material bends when part of it is heated, and the polymer chains at that point realign, which changes the material’s opacity. The more the material bends, the more transparent it becomes. Embedded photodiodes detect this change in transparency, providing feedback about the material’s motion that a robot could use to plan its next move. Being able to self-sense “is something that’s very new in materials,” says Chiara Daraio, a materials scientist at the California Institute of Technology not involved with the research. “I think it’s very neat.”