MIT'S LIGHT-STEERED SWIMMING ROBOT RUNS ON A HAIR-THIN LAYER OF LIVING MUSCLE

Summary from the TLDR Hardware newsletter

MIT built a swimming robot from a gum-stick-sized gel frame with two fins, each coated in a muscle layer thinner than a hair and engineered to contract under light. Lighting one fin or both steers it through a maze at about four body lengths per minute. The key fixes were stiff GelMA gel about half a millimeter thick with square-bottomed grooves that align the cells, and light-pulse training to strengthen the muscle. It's the first thin 2D biohybrid swimmer.