Brownian Disks Lab: Simulating time-lapse microscopy experiments for exploring microrheology techniques and colloidal interactions

Brownian Disks Lab (BDL) is a Java-based application for the real-time generation and visualization of the motion of two-dimensional Brownian disks using Brownian Dynamics (BD) simulations. This software is designed to emulate time-lapse microscopy experiments of colloidal fluids in quasi-2D situations, such as sedimented layers of particles, optical trap confinement, or fluid interfaces. Microrheology of bio-inspired fluids through optical-based techniques such as videomicroscopy is a classic tool for obtaining the mechanical properties and molecular behavior of these materials. The results obtained by microrheology notably depend of the time-lapse value of the videomicroscopy setup, therefore, a tool to test the influence of the lack of statistics by simulating Brownian objects in experimental-like situations is needed. We simulate a colloidal fluid by using Brownian Dynamics (BD) simulations, where the particles are subjected to different external applied forces and inter-particle interactions. This software has been tested for the analysis of the microrheological consequences of attractive forces between particles [1], the influence of image analysis on experimental microrheological results [2], and to explore experimental diffusion with optical tweezers [3]. The output results of BDL are directly compatible with the format used by standard microrheological algorithms [4]. In a context of microrheology of complex bio-inspired fluids, we use this tool here to study if the lack of statistics may influence the observed potential of a bead trapped by optical tweezers.