Effects of crowding and enzyme-driven active fluctuations on particle correlations in colloidal suspensions

We investigated the correlation dynamics of colloidal particles in crowded, aqueous, and quasi-two-dimensional environments. Using optical microscopy, we analyzed variations in two-particle displacement and direction correlations, estimating their respective ranges of influence. Our results show that microscopic colloidal particles significantly impact the dynamics of their neighbors, with the strength of correlations diminishing with increasing distance - following a power-law decay. Increased particle area fractions, however, enhance these correlation ranges. Introducing localized active fluctuations via enzyme-substrate reactions, extends it even further. We performed overdamped Langevin dynamics simulations, which qualitatively supported our experimental findings. This study advances our understanding of active matter systems by revealing how crowding and enzyme-driven active fluctuations can modulate particle correlations. These insights pave the way for improved design and control of colloidal assemblies in complex environments, with potential applications in materials science, biophysics, and nanotechnology.