Out-of-Equilibrium Crystallization Dynamics in Light-Driven Self-Assembly

We explore the dynamics of colloidal crystal formation through light-driven thermal convection in a binary mixture of gold nanoparticles and polystyrene microparticles. In our system, gold nanoparticles absorb visible light and generate a temperature gradient that induces convection, driving the assembly of polystyrene microparticles into a crystalline monolayer. We quantified the crystallization dynamics by varying the light intensity and observed that crystals with high hexatic order emerge above a critical light threshold. Larger particles (10 μm) experience stronger hydrodynamic interactions that promote crystallization at a low intensity but suffer from slower growth kinetics. Additionally, we observe different nucleation and growth dynamics depending on particle sizes – the larger (5 μm and 10 μm) particles form crystals that grow around a central nucleus, while the smaller particles (2 μm) nucleate into many small grains that coarsen under the influence of the convection flow. We modeled the experimental data with a growth curve to predict the crystal growth rate based on particle diameter and light intensity. The insights