Helfield BL, et al. – The aim of this research is to help substantiate the merit of polymeric microbubble sonoporation as a non–viral, localized cell permeation and payload delivery strategy by taking a ground–up approach to elucidating the fundamental mechanisms at play. These outcomes have revealed one aspect of polymeric bubble activity on the microsecond time scale that is correlated with eliciting sonoporation in adjacent endothelial cells, and contributes toward an understanding of the physical rationale for sonoporation with polymer–encapsulated microbubble contrast agents.