Accounting for inertia effects to access the high-frequency microrheology of viscoelastic fluids

TL;DR

This paper investigates high-frequency microrheology of viscoelastic fluids by analyzing microbead Brownian motion, explicitly accounting for inertia effects to accurately determine mechanical properties at short time scales.

Contribution

It introduces a method that considers inertia effects in microrheology measurements, enabling precise high-frequency characterization of viscoelastic fluids.

Findings

Recovered the 3/4 scaling exponent for loss modulus in micelle solutions.

Demonstrated the importance of inertia effects at short time scales.

Validated the approach with experimental data.

Abstract

We study the Brownian motion of microbeads immersed in water and in a viscoelastic wormlike micelles solution by optical trapping interferometry and diffusing wave spectroscopy. Through the mean-square displacement obtained from both techniques, we deduce the mechanical properties of the fluids at high frequencies by explicitly accounting for inertia effects of the particle and the surrounding fluid at short time scales. For wormlike micelle solutions, we recover the 3/4 scaling exponent for the loss modulus over two decades in frequency as predicted by the theory for semiflexible polymers.