Non-Newtonian viscosity of E-coli suspensions

TL;DR

This study experimentally investigates the complex non-Newtonian viscosity behavior of E-coli bacterial suspensions in microfluidic channels, revealing regimes of rheo-thickening and rheo-thinning and conditions where viscosity drops below that of the suspending fluid.

Contribution

It provides new experimental insights into the rheological behavior of active bacterial suspensions, including direct measurements of concentration and velocity profiles in microfluidic setups.

Findings

Identification of rheo-thickening and rheo-thinning regimes

Observation of viscosity lower than suspending fluid at low shear rates

Direct measurement of bacteria concentration and velocity profiles

Abstract

The viscosity of an active suspension of E-Coli bacteria is determined experimentally in the dilute and semi dilute regime using a Y shaped micro-fluidic channel. From the position of the interface between the pure suspending fluid and the suspension, we identify rheo-thickening and rheo-thinning regimes as well as situations at low shear rate where the viscosity of the bacteria suspension can be lower than the viscosity of the suspending fluid. In addition, bacteria concentration and velocity profiles in the bulk are directly measured in the micro-channel.