Model-based image analysis of a tethered Brownian fibre for shear stress sensing

Abstract

The measurement of fluid dynamic shear stress acting on a biologically relevant surface is a challenging problem,particularly in the complex environment of, for example, the vasculature.While an experimentalmethodfor the direct detection ofwall shear stress via the imaging of a synthetic biology nanorod has recently been developed, the data interpretation so far has been limited to phenomenological randomwalkmodelling, small-angleapproximation, andimageanalysis techniques which do not take into account the production of an image from a three-dimensional subject. In this report, we develop a mathematical and statistical framework to estimate shear stress from rapid imaging sequences based firstly on stochastic modelling of the dynamics of a tethered Brownian fibre in shear flow, and secondly on a novel model-based image analysis, which reconstructs fibre positions by solving the inverse problemof image formation. This framework is tested on experimental data, providing the first mechanistically rational analysis of the novel assay.What follows further develops the established theory foran untethered particle in a semi-dilute suspension, which is of relevance to, for example, the study of Brownian nanowireswithout flow, and presents new ideas in the field of multi-disciplinary image analysis.