Using cavitation rheology to understand dipeptide-based low molecular weight gels

We show that combining cavitation and conventional rheology can be used to understand the underlying microstructure in gels.

Cross-Platform Mechanical Characterization of Lung Tissue

ABSTRACTPublished data on the mechanical strength and elasticity of lung tissue is widely variable, primarily due to differences in how testing was conducted across individual studies. This makes it extremely difficult to find a benchmark modulus of lung tissue when designing synthetic extracellular matrices (ECMs). To address this issue, we tested tissues from various areas of the lung using multiple characterization techniques, including micro-indentation, small amplitude oscillatory shear (SAOS), uniaxial tension, and cavitation rheology. We report the sample preparation required and data obtainable across these unique but complimentary methods to quantify the modulus of lung tissue. We highlight cavitation rheology as a new method, which can measure the modulus of intact tissue with precise spatial control, and reports a modulus on the length scale of typical tissue heterogeneities. Shear rheology, uniaxial, and indentation testing require heavy sample manipulation and destruction; however, cavitation rheology can be performed in situ across nearly all areas of the lung with minimal preparation. The Young’s modulus of bulk lung tissue using microindentation (1.9±0.5 kPa), SAOS (3.2±0.6 kPa), uniaxial testing (3.4±0.4 kPa), and cavitation rheology (6.1±1.6 kPa) were within the same order of magnitude, with higher values consistently reported from cavitation, likely due to our ability to keep the tissue intact. Although cavitation rheology does not capture the non-linear strains revealed by uniaxial testing and SAOS, it provides an opportunity to measure mechanical characteristics of lung tissue on a microscale level on intact tissues. Overall, our study demonstrates that each technique has independent benefits, and each technique revealed unique mechanical features of lung tissue that can contribute to a deeper understanding of lung tissue mechanics.

Viscoplastic fracture transition of a biopolymer gel

We study the effects of gelatin chain composition on the fracture behavior of gelatin gels using cavitation rheology to show two fracture mechanisms exist for these materials that is determined by the whether the gel concentration is above or below the critical concentration for entanglements.