Coupled oscillation and spinning of photothermal particles in Marangoni optical traps

Significance Oscillators, widely found in nature, form the basis of a wide variety of actuating and signal processing mechanisms. While the ability to mimic arrays of oscillators and control their coupling is a central goal in the field of bioinspired soft materials, this has been difficult to achieve. Using Marangoni forces generated during spatially inhomogeneous illumination of photothermally responsive particles, we demonstrate a scheme for optically trapping arrays of particles at air–water interfaces that can incite a range of oscillatory and spinning behaviors. When multiple objects are arranged in proximity, they exhibit complex, collective behavior emerging from geometry-dependent interparticle coupling. This route to achieving collective motion is expected to open opportunities in the study of active materials.