Direct and inverse modeling for stochastic passive microbead rheology

Abstract

AbstractThe need in biology to understand the rheological properties of cells, tissues, membranes, and biological liquids, has led to new techniques in microrheology, where passive bead tracking is the fundamental probe of viscoelastic properties. We present stochastic methods for direct and inverse characterization based on noisy time series associated with either one or multiple beads, focusing on the distinctions in bead statistics due to bead‐bead hydrodynamic interactions versus the ratio of bead separation distance and bead radii. Our modeling combines the seminal works of Mason & Weitz for single bead statistics and of Crocker‐Levine‐Lubensky for 2‐bead statistics, together with the recent methods of the authors on direct and inverse simulation tools for generalized Langevin equations. The aim is to develop statistically accurate and fast direct simulation tools for bead‐bead fluctuations, and then inversion methods derived from maximum likelihood methods and the Kalman filter. The application is to support experiments by R. Superfine and D. Hill and for characterization and simulations of transport mechanisms in lung airway surface liquids within the Virtual Lung Project at UNC Chapel Hill. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)