Estimating viscoelastic, soft material properties using a modified Rayleigh cavitation bubble collapse time

TL;DR

This paper introduces a modified Rayleigh collapse time method to estimate viscoelastic properties of soft materials using acoustic signals, enabling measurements in optically opaque tissues without direct visualization.

Contribution

The study develops a new energy-based theoretical framework that allows estimation of soft tissue properties from bubble collapse times without imaging, expanding IMR applicability.

Findings

Collapse time correlates with material stiffness above 10 kPa.

The method provides order-of-magnitude estimates of viscoelastic properties.

High measurement precision is required for very soft materials.

Abstract

Accurate determination of high strain rate (> 10^3 1/s) constitutive properties of soft materials remains a formidable challenge. Albeit recent advancements among experimental techniques, in particular inertial microcavitation rheometry (IMR), the intrinsic requirement to visualize the bubble cavitation dynamics has limited its application to nominally transparent materials. Here, in an effort to address this challenge and to expand the experimental capability of IMR to optically opaque materials, we investigated whether one could use the acoustic signature of the time interval between bubble nucleation and collapse, characterized as the bubble collapse time, to infer the viscoelastic material properties without being able to image the bubble directly in the tissue. By introducing a modified Rayleigh collapse time for soft materials, which is strongly dependent on the stiffness of the material at hand, we show that, in principle, one can obtain an order of magnitude or better estimate of the viscoelastic material properties of the soft material under investigation. Using a newly developed energy-based theoretical framework, we show that for materials stiffer than 10 kPa the bubble collapse time during a single bubble cavitation event can provide quantitative and meaningful information about the constitutive properties of the material at hand. For very soft materials (i.e., shear modulus less than 10 kPa) our theory shows that unless the collapse time measurement has very high precision and low uncertainties, the material property estimates based on the bubble collapse time only will not be accurate and require visual resolution of the full cavitation kinematics.