Thermodynamic State of the Interface during Acoustic Cavitation in Lipid Suspensions

TL;DR

This study investigates the thermodynamic behavior of lipid interfaces during shock wave cavitation, revealing how phase transitions influence cavitation thresholds and dynamics, with implications for biomedical and physical applications.

Contribution

It provides direct measurements of lipid interface states during cavitation, highlighting the role of phase transitions and heat exchange in cavitation processes.

Findings

Cavitation threshold is lowest near lipid phase transition.

Lipid dehydration and crystallization occur during cavitation expansion.

Interface heat absorption is from within, decoupled from free water.

Abstract

The thermodynamic state of lipid interfaces was observed during shock wave induced cavitation in water with sub-microsecond resolution, using the emission spectra of hydration-sensitive fluorescent probes co-localized at the interface. The experiments show that the cavitation threshold is lowest near a phase transition of the lipid interface. The cavitation collapse time and the maximum state change during cavitation are found to be a function of both the driving pressure and the initial state of the lipid interface. The experiments show dehydration and crystallization of lipids during the expansion phase of cavitation, suggesting that the heat of vaporization is absorbed from within the interface, which is adiabatically uncoupled from the free water. The study underlines the critical role of the thermodynamic state of the interface in cavitation dynamics, which has mechanistic implications for ultrasound-mediated drug delivery, acoustic nerve stimulation, ultrasound contrast agents, and the nucleation of ice during cavitation.