Rheology and Microstructural Behavior of Semidilute Suspensions of Semiflexible Rods across Five Decades of Shear Rate

Rod-like particles are efficient rheology modifiers and are commonly found in a variety of biological and industrially relevant suspensions, from biofilaments to worm-like surfactant micelles. These suspensions display strong shear-thinning behavior, and ongoing efforts aim to understand the microstructural changes of these fluids: how they depend upon the properties of the suspended particles and how these changes manifest in the resulting rheology. With suspensions of fd bacteriophage as a model monodisperse rod system, we use capillary microrheometry and flow birefringence to determine rheological behavior across nearly six decades of shear rate up to 6 × 10⁵ s^-1, at various semidilute concentrations. A single, and surprisingly large, primary fitting parameter accounting for the characteristic distance of hydrodynamic interactions is consistent with viscosity data up to very high shear rates. These results may prompt other work to understand the mechanics of these interactions.