Light-driven Synchronization of Active Particles in Marangoni Optical Traps

We demonstrate a versatile platform of photoresponsive active particles that exhibit synchronized oscillation and rotation. The active particles, hydrogel nanocomposite disks, are patterned with gold nanoparticles (AuNPs) that enable a photothermal response. When confined to an air-water interface, spatially inhomogeneous illumination combined with the AuNP-patterning allows for the modulation of the Marangoni force on the particles. We observe distinct modes of light-driven active motion, including oscillation, spinning, and orbiting of individual particles around a trap. When multiple oscillators and rotors are arranged in proximity, we observe strong synchronization arising from thermal interactions between the particles. We study how the nature of the synchronization can be reconfigured using the geometry of the particles and the illumination patterns. Our experiments offer promise for understanding the collective behavior of active matter that arises from different modes of broken symmetry and motions.