Colloids Learn to Breathe express
A drop of water on glass trembles and shimmers: it seems to have a life of its own. Similar behavior can now be observed in the world of colloids: tiny particles suspended in a liquid. Researchers simulated particles that emit chemical signals. These signals, like scents in the air, spread around and cause neighbors to either draw closer or move apart.
This mechanism is called paracrine signaling (cell-to-cell communication via chemical messages)—it's how cells in our bodies talk to each other without direct contact. In the model, particles respond to the history of interactions: what happened a moment ago influences the next step. This breaks the usual equilibrium and sets off an internal clock. The system, on its own and without external commands, begins to pulsate: clusters of particles grow and then fall apart.
The authors mapped out different behavioral regimes, from complete stillness to sustained oscillations. Everything depends on three levers: how quickly signals are produced, how quickly they decay, and how far they manage to spread. In one regime, self-sustaining cycles emerge — particles dance endlessly, assembling and disassembling again. This is not just a pretty picture; it's a first step toward programmable materials with living dynamics.
In our blood, platelets use a similar principle: they release chemicals that attract other platelets to quickly plug a wound. But there, the signal works in one direction, toward assembly, while in the scientists' model, particles can both assemble and disperse.
In Stanisław Lem's novel "The Invincible," the heroes encounter a swarm of mechanical "flies" that act as a single organism, following simple rules. Such colloids are a step toward creating artificial life of this kind.