Local Oscillatory Rheology from Echography

TL;DR

LORE combines traditional rheology with ultrasonic imaging to provide detailed local measurements of material response during oscillatory shear, enabling analysis of heterogeneity, wall slip, and nonlinear behavior.

Contribution

This paper introduces a novel method that synchronizes rheology with ultrasonic imaging to measure local viscoelastic properties during oscillatory shear.

Findings

Effective in characterizing heterogeneous samples

Able to detect wall slip phenomena

Capable of analyzing nonlinear responses in soft materials

Abstract

Local Oscillatory Rheology from Echography (LORE) consists in a traditional rheology experiment synchronized with high-frequency ultrasonic imaging which gives access to the local material response to oscillatory shear. Besides classical global rheological quantities, this method provides quantitative time-resolved information on the local displacement across the entire gap of the rheometer. From the local displacement response, we compute and decompose the local strain in its Fourier components and measure the spatially-resolved viscoelastic moduli. After benchmarking our method on homogeneous Newtonian fluids and soft solids, we demonstrate that this technique is well suited to characterize spatially heterogeneous samples, wall slip, and the emergence of nonlinearity under large amplitude oscillatory stress in soft materials.