MIT engineers have designed a thin swimming robot powered by living muscle cells, described in a paper in the journal Advanced Functional Materials and reported by MIT News. The robot's 'skeleton' is a film of gel roughly the length and width of a stick of gum, whose two halves form fins. Each fin is covered with a layer of muscle cells much thinner than a strand of hair, genetically engineered to twitch in response to light. MIT says it is the first example of a very thin, two-dimensional, muscle-powered robot capable of locomotion.
Shining light on one fin makes its muscles contract and the fin flap, pulling the robot through water. By flashing light on one fin or the other at different intervals, the researchers control direction and speed. In tests in a petri dish, the robot followed a manually moved light source through a simple maze. At its fastest it covers about four times its body length per minute, which MIT compares with the leisurely pace of the cow shark; Olympic swimmers manage up to 65 body lengths per minute.
The work builds on the Raman Lab's earlier iris-inspired disk of artificial muscle, whose cells moved only about 100 microns. To generate more force, the team replaced the ultrasoft fibrin gel used before with gelatin methacrylate (GelMA), tested different stiffnesses and groove shapes, and found that stiffer gels and square grooves produced better-aligned cells and the most force. A half-millimetre-thin film supported a single layer of cells, which were then 'exercised' with flashing light to strengthen them.
Study author Ritu Raman, associate professor of mechanical engineering at MIT, said current biohybrid robots are built from bulky, 3D chunks of lab-grown muscle requiring millions of cells, whereas thinner designs could be cheaper to build and move more efficiently. She said living tissue is soft, responsive and can heal itself, which could suit environments too fragile or unpredictable for conventional hardware.
The team's next goal is to optimise the body design for faster swimming. Raman suggested that even slow muscle-powered swimmers could be used for environmental monitoring in aquatic settings. The research was supported in part by the Office of Naval Research; first author is graduate student Maheera Bawa.