Description:

Soft matter physics is at its heart a discipline that studies systems which are nonlinear, disordered, and out-of-equilibrium, making many of our standard tools in physics challenging to apply.  My approach to this challenge is to use emergent structures and patterns as a new way to probe soft matter systems, giving new insight which allows us to characterize and control these materials.  One of the research avenues in my lab is centered on using boundary-free fluid flows that allow us to obtain localized measurements of complex material behavior.  In this talk, I will discuss how I have used this approach to unravel the complexities of non-Newtonian flow behavior.  In particular, I will describe how my lab has used drop impact experiments to gain new insights into shear thickening, the remarkable ability of dense suspensions to transition from a flowing liquid into a solid under applied stress.  Leveraging the power of high-seed imaging, and the unique geometry of drop impact, we are able to obtain flow information in a spatially-localized manner, so that we can observe coexisting solid and liquid phases. Furthermore, our measurements allow us to capture solidification as it occurs via a front traveling from the impact point, and show that the speed of this front is set by how far the impact conditions are beyond the shear thickening transition.  I will conclude by discussing how this methodology can be applied to gain insight into dynamics as well as microstructure in a  wide range of soft materials.

Speaker: Michelle Driscoll, Assistant Professor, Northwestern University

Host: Andre de Gouvea