--- title: "A Paper-Thin Robot Swims on a Single Layer of Living Muscle, Steered by Flashlight" description: "MIT’s gum-stick-sized aquabot flaps through a watery maze at a stately four body lengths per minute — cow shark pace" author: "Penny Quirke" published: 2026-09-29T08:47:12.715Z modified: 2026-09-29T09:51:21Z url: https://rews.cc/a/a-paper-thin-robot-swims-on-a-single-layer-of-living-muscle--d8c24c language: en tags: ["robots", "ai", "biology", "engineering", "swimming", "tech"] publisher: "Rews (https://rews.cc)" --- # A Paper-Thin Robot Swims on a Single Layer of Living Muscle, Steered by Flashlight *MIT’s gum-stick-sized aquabot flaps through a watery maze at a stately four body lengths per minute — cow shark pace* By Penny Quirke · September 29, 2026 · https://rews.cc/a/a-paper-thin-robot-swims-on-a-single-layer-of-living-muscle--d8c24c ## In brief - MIT engineers built a swimming robot powered by a single layer of live muscle cells thinner than a hair - The gum-stick-sized bot’s GelMA gel skeleton forms two fins, steered by flashing light on either side - Top speed is about four body lengths per minute — cow shark pace, well short of Olympic swimmers - The team says it is the first thin, two-dimensional muscle-powered robot capable of locomotion - The study appears in Advanced Functional Materials; Maheera Bawa is first author, Ritu Raman leads the group Swimming, as anyone who has done a lap or two can attest, takes muscle. But how much muscle, exactly, is the minimum order? MIT engineers have an answer, and it is less than you think: a single layer of muscle cells, thinner than one strand of your hair, is enough to power a robot through water — provided you design the rest of it correctly. In a paper appearing today in the journal *Advanced Functional Materials*, a team led by Ritu Raman, associate professor of mechanical engineering at MIT, presents what they describe as the first very thin, two-dimensional, muscle-powered robot capable of locomotion. The aquabot’s “skeleton” is a film of gel about the length and width of a stick of gum, split into two halves that serve as fins. Each fin is coated with live muscle cells genetically engineered to twitch in response to light. That last detail is the steering wheel. Shine light on one fin and the muscle on its surface contracts, flapping the fin hard enough to pull the whole robot forward. Flash the light on one fin or the other, at various intervals, and the researchers can command the bot’s direction and speed — enough to swim and swivel it through a simple watery maze laid out in the dish it lives in. Top speed: about four body lengths per minute. Olympic swimmers cover up to 65 body lengths per minute, so the aquabot will not be taking Michael Phelps’s spot. But the MIT team notes the robot could hold its own against the cow shark, which ambles around the ocean at roughly the same rate. For a device made of gelatin and a whisper of muscle, keeping pace with an actual shark — even the ocean’s most unhurried one — is not nothing. > It takes a lot of force to move through water versus air. The robot’s quite strong, given its size. That assessment comes from Raman, who has a particular grudge against the way biohybrid robots are usually built. “Currently, biohybrid robots from our group and others’ are built from bulky, 3D chunks of lab-grown skeletal muscle that require millions of cells to fabricate,” she says. Thinner designs like the new bot, she argues, could be cheaper to build and could move more efficiently. Her longer ambition: “We believe that biohybrid robots powered by living muscle could one day perform delicate jobs like exploring environments too fragile or unpredictable for conventional hardware, because living tissue is soft, responsive to its surroundings, and can heal itself.” A robot that heals itself is not a claim your average titanium drone can make. The study’s MIT co-authors are first author Maheera Bawa, Arielle Berman, Laura Schwendeman, Ferdows Afghah, and Seanbiron Johnson. ## First, teach muscle to live flat The aquabot builds on work Raman’s group published last year: an iris-inspired disk of artificial muscle tissue. They stamped a gel disk with concentric and radial grooves, deposited live muscle cells on top, and watched the cells grow along the grooves in a thin layer. Stimulated with light, the muscle stretched and squeezed the disk the way a human iris dilates and constricts a pupil. It was the first demonstration that muscle cells could be grown in a very thin layer, in complex patterns, moving in multiple controllable directions. It was also, by robotic standards, faintly underwhelming in the oomph department. “People hadn’t seen this muscle architecture engineered from scratch before,” Raman says. “And the cells were moving in multiple directions. But they only moved about 100 microns. From a robotics perspective, their movements were tiny.” A tenth of a millimeter will not get you through a maze. The fix, the team found, was the skeleton. In the iris design the muscle grew on fibrin, an ultrasoft gel that, the researchers realized, shrivels quickly under the forces the muscles generate — picture doing push-ups on a waterbed. So they set about tuning three properties of the underlying gel: its composition, its stiffness, and the size and shape of the grooves stamped into it. “For engineering any type of tissue, it’s known that these are knobs you can tune,” Raman says. “And we wanted to optimize all these parameters to support live muscle cells.” ## Square grooves, stiff gel, half a millimeter The experiments read like a very meticulous episode of a cooking show. The team tried multiple gel formulations and groove geometries — one groove resembled a skinny square trough, another more of a long curved valley. Cells settled into alignment in the squarer grooves, and aligned cells tend to fuse into fibers that form stronger, more coordinated muscle tissue. Square it was. In place of fibrin they used gelatin methacrylate, or GelMA, a workhorse material in tissue engineering, and found that cells aligned better and produced the most force on stiffer gels. They varied the film’s thickness too, landing on a half-millimeter-thin sheet of GelMA: light enough that the cells stayed stuck to the gel when they contracted, rather than peeling themselves off like a sticker in the bath. Then the muscle went to the gym. The team “exercised” the cells with a training routine of flashing lights to strengthen them — which means the robot’s muscle tissue had a workout regimen before it had a body. The finished robot packs all of it: GelMA film, square-bottomed grooves stamped on both sides, muscle cells fused into aligned fibers on each fin. “You can think of the robot as having two independent muscles,” Raman says. “If we shine a light on just one, only that muscle moves. If shining on both, they both flap.” In the maze test, the researchers submerged the robot in a large petri dish of water and manually moved a light source over it; the robot followed the light, flapping and swiveling its way through. No tiny onboard computer, no propeller, no battery — just light, gelatin, and a layer of living cells doing the one thing muscle cells have done for a few hundred million years. The cow shark, presumably, remains unbothered.