Long-term influence of fluid inertia on the diffusion of a Brownian particle

Giuseppe Pesce, Giorgio Volpe, Giovanni Volpe, Antonio Sasso
2014 Physical Review E  
We demonstrate experimentally that a Brownian particle is subject to inertial effects at long time scales. By using a blinking optical tweezers, we extend the range of previous experiments by several orders of magnitude up to a few seconds. The measured mean square displacement of a freely diffusing Brownian particle in a liquid shows a deviation from the Einstein-Smoluchowsky theory that diverges with time. These results are consistent with a generalized theory that takes into account not only
more » ... to account not only the particle inertia but also the inertia of the fluid surrounding the particle. This can lead to a bias in the estimation of the diffusion coefficient from finite-time measurements. We show that the decay of the relative error is polynomial and not exponential and, therefore, can have significant effects at time scales relevant for experiments.
doi:10.1103/physreve.90.042309 pmid:25375496 fatcat:fwotyzb2lzckxj53uczb7xnpli