Non-Equilibrium Dynamics in Optical Matter Systems under Variable Light Fields: A Computational Fluid Dynamics Perspective

Abstract

The self-organization of nanoparticles into ordered arrays mediated by optical binding forces, known as optical matter, represents a frontier in soft matter physics and photonics. While static optical  binding has been extensively characterized, the behavior of these systems under time-varying light fields remains less understood, particularly regarding the role of hydrodynamic interactions. This  study employs a coupled Computational Fluid Dynamics (CFD) and electrodynamics simulation framework to investigate the non-equilibrium dynamics of optical matter in aqueous environments.  By explicitly resolving the solvent velocity field using the Navier-Stokes equations alongside the Langevin dynamics of the particles, we elucidate the complex interplay between optical scattering forces and fluid-mediated coupling. Our results demonstrate that under variable illumination—specifically oscillating and rotating optical traps—hydrodynamic interactions significantly alter the trajectory and stability of particle arrays compared to predictions based solely on conservative  optical forces. We observe emergent collective motion and fluid pumping effects that suggest new mechanisms for controlling transport at the mesoscale. This work underscores the necessity of full  hydrodynamic treatments in modeling dynamic optical matter systems and offers a predictive platform for designing optically reconfigurable colloidal machines.