Engineers at Northwestern University have unveiled the behavior of single microscopic particles when they unite. The findings reveal an enigmatic, perfectly synchronized dance.
Study: Self-oscillating synchronematic colloids. Image Credit: Lukas Gojda/Shutterstock.com
The research team discovered that groups of minuscule particles suspended in a liquid oscillate in harmony, maintaining a synchronized rhythm as if they can somehow perceive each other’s movements. Adjacent particles align, creating clusters that seem to sway together – rocking back and forth with remarkable coordination. The study was published in the journal Nature Communications.
The driving force behind this synchronization, according to computer simulations, is the liquid itself. As each particle oscillates, it gently agitates the surrounding fluid. These minute ripples propagate outward, nudging neighboring particles.
Although the particles do not physically contact one another, they affect each other’s movements. The motion of the fluid allows the particles to “sense” one another from a distance.
These findings may provide insight into how intricate, collective behaviors arise without the need for communication or signaling. From fireflies that illuminate in unison to heart cells that contract simultaneously, numerous living systems depend on synchronized timing without a central authority. By traversing a common medium, individual elements can impact each other’s timing.
The results imply that in biological systems as well, the environment itself – whether it be fluid, tissue, or air – could play a vital role in coordinating collective rhythms.
This project took years to complete. The main question was ‘why are these particles moving together?’ Somehow, they appeared to be influencing each other and eventually synchronize their movements. It’s almost like the particles cooperate, and it was impossible for us to understand why. We reproduced the experimental model as a complex simulation, so we could watch the interactions in high detail.
Monica Olvera de la Cruz, Study Senior Author, Northwestern University
The phenomenon known as synchronization, which refers to the emerging coordination among a group of individuals, is frequently observed in both natural and engineered systems. The researchers were surprised to witness this phenomenon manifest so distinctly within a straightforward physical system.
In computer simulations, Leyva examined hundreds of simplified microscopic particles navigating through a shallow, fluid-like medium. Leyva assigned colors to each particle according to its position within its oscillation cycle.
Entire clusters illuminated in corresponding colors, indicating that groups of particles were functioning as a unified, coordinated entity.
Initially, Olvera de la Cruz and Leyva speculated whether the electric field could account for this behavior. Upon further examination of the computer simulation, they swiftly dismissed that possibility.
In our simulations, we were able to turn off the electrostatics. You can’t do that in an experiment. But in the model, we could isolate the hydrodynamics while keeping the oscillatory dynamics of the particles.
Sergi Leyva, Study Primary Author and Postdoctoral Fellow, Northwestern University
The team illustrated that interactions driven by fluid dynamics could solely account for the synchronization of the particles by integrating the comprehensive simulation with experimental data and a streamlined mathematical model.
The researchers were also able to forecast the color (or oscillation phase) that each particle would assume, depending on its location within the group.
When a particle moves in a fluid, it generates a flow. If there is another particle nearby, it’s affected by this flow. So, if you have two particles that initially oscillate at different phases, eventually they end up oscillating together. They synchronize with their closest neighbors.
Sergi Leyva, Study Primary Author and Postdoctoral Fellow, Northwestern University
With the underlying mechanism now understood, the researchers aim to explore methods for controlling synchronization. By adjusting particle density, geometry, and confinement, subsequent research could enable the activation and deactivation of collective motion – establishing a foundation for programmable materials and microscale systems that exhibit functions derived from coordinated behavior.
The results provide a novel physical framework for comprehending how synchronization occurs in living systems, where movement through shared fluids is crucial.
“Sometimes the most complex behavior comes from the simplest ingredients. In this case, motion through a fluid is enough to bring an entire system into sync,” said Olvera de la Cruz.
The study was supported by the U.S. Department of Energy.
Hidden rhythm brings microscopic particles into unison
A hidden rhythm brings microscopic particles into unison. Video Credit: Northwestern University
Journal Reference
Leyva, G. S., et al. (2026) Self-oscillating synchronematic colloids. Nature Communications. DOI: 10.1038/s41467-026-68552-8.