Ultrafast ultrasonic imaging coupled to rheometry: principle and illustration

TL;DR

This paper introduces a novel ultrafast ultrasonic imaging technique integrated with rheometry, enabling real-time visualization and measurement of local fluid dynamics and properties during shear, with high frame rates and broad application potential.

Contribution

It presents a new 'rheo-ultrasound' method combining ultrasonic imaging with rheology to study soft materials under shear with high temporal resolution.

Findings

Successful visualization of Taylor-Couette instability.

Observation of shear-banded flow in micellar solutions.

High frame rate imaging of fluid dynamics under shear.

Abstract

We describe a technique coupling standard rheology and ultrasonic imaging with promising applications to characterization of soft materials under shear. Plane wave imaging using an ultrafast scanner allows to follow the local dynamics of fluids sheared between two concentric cylinders with frame rates as high as 10,000 images per second, while simultaneously monitoring the shear rate, shear stress, and viscosity as a function of time. The capacities of this "rheo-ultrasound" instrument are illustrated on two examples: (i) the classical case of the Taylor-Couette instability in a simple viscous fluid and (ii) the unstable shear-banded flow of a non-Newtonian wormlike micellar solution.