In an indoor test tank at MIT, eight square robots the size of dinner plates drifted out from random starting points, converged on a target outline, and clamped together into a single rigid raft. Then they let go, rearranged into a new shape, and glided across the pool as one vessel. Each full cycle took between four and eight minutes.
The system, named FloatForm, is described in a newly published open-access paper in Nature Communications by researchers from MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL) and its Senseable City Lab, with collaborators now at the University of Wisconsin-Madison and KU Leuven. It grew out of Roboat, MIT's earlier project with the Amsterdam Institute for Advanced Metropolitan Solutions, which put full-size autonomous vessels on that city's canals.
Each 21-centimetre-square unit is a self-contained boat carrying its own thrusters, sensors and magnetic latches. What sets FloatForm apart, though, is less the hardware than how the boats decide where to go.
A lesson from fire-ant rafts
The team took its cue from fire ants, which survive floods by linking their bodies into living rafts. No ant directs the others; each follows simple local rules, and a resilient structure emerges. Most self-assembling robot swarms instead depend on a central computer that plans every move — an approach that collapses if that computer fails and slows as robots are added, forcing the machines to assemble one at a time while most sit idle.
FloatForm inverts that balance. A lightweight central planner steps in only briefly, assigning each robot a final position to sharpen the lattice; otherwise the boats navigate, avoid collisions and absorb disturbances on their own, exchanging positions only with their immediate neighbours. Because each robot's calculations depend on those neighbours rather than the size of the swarm, the whole fleet moves at once, and assembly time barely grows as the group expands. In simulation, the framework scaled to 64 boats.
"Whether you are working with eight boats or 80, the entire fleet coordinates and moves simultaneously," said Wei Wang, the paper's lead author, who now leads the Marine Robotics Lab at the University of Wisconsin-Madison. Sticking together brings a physical payoff, too: like an ant raft, the joined boats ride out waves and currents more steadily than any single hull.
The researchers see the water surface as underused public space. Their paper points to temporary infrastructure, environmental monitoring and on-demand transport as early applications; the group also imagines emergency bridges to relieve street traffic, floating markets, and pop-up stages that appear for a festival and dissolve when the crowd goes home.