Prof. Michelle Driscoll, Department of Physics & Astronomy, Northwestern University

"Suspension drops under extreme stress"

Abstract: Understanding the rich and nuanced physics of drop impact is crucial in many processes: for example, geological erosion, industrial coating, forensics, and agrochemical delivery, and the drop impact of Newtonian fluids has been a studied extensively for over a century. However, literature on the impact dynamics of complex fluids is relatively sparse, despite the ubiquity of complex fluids in many natural and industrial impact processes. Here, we present a systematic study of colloidal drop impact over a large range of volume fractions and impact velocities, allowing us to explore the full range of non-newtonian flow behaviors in these suspensions. We observe impact behaviors ranging from liquid-like spreading to solid-like jamming and connect them to the bulk rheological behavior of our colloidal system. These experiments allow for an exploration of the rich flow behaviors that are only apparent in the absence of confinement, and they provide a window into high-stress suspension dynamics, inaccessible by other means.