First-passage statistics of a confined brownian particle

The encounter of diffusing entities underlies a wide range of natural phenomena. The dynamics of these first-passage processes are strongly influenced by the geometry of the system. In this Letter, we investigate the impact of confinement on the first-passage statistics of a diffusing particle. These rare events are probed by combining holographic microscopy with advanced statistical inference methods. Our numerical and experimental results provide a comprehensive understanding of a process governed by the coupling between surface forces and thermal fluctuations, resolved at the nanometric scale. Confinement - which alters the diffusion of micrometric particles through hydrodynamic interactions - emerges as a key ingredient for modeling realistic environments. Our work highlights and quantifies the dynamics of target-finding processes that govern chemical reactions in crowded media, and thus the physics of life itself. We further show that, in some cases, hydrodynamically induced non-Gaussianities enhance first-passage kinetics.