Ultrasound radiation force as a method to characterize the viscosity of microbubble shells

Characterizing the complex viscoelastic properties of microbubble shells typically requires experimentally challenging techniques, such as isolating single microbubbles and measuring optically their oscillatory response to well- controlled acoustic driving. Here, we propose a relatively simple alternative method to determine the shell viscosity for a known shell elasticity,which consists of measuring ultrasound radiation force-induced displacements within freely floating microbubble populations using a standard ultrasound-imaging probe. We experimentally tested this technique on lipid-coated microbubbles and verified its accuracy by comparing with measurements made on the oscillatory response of individual microbubbles to ultrasound driving.