Levich Institute Seminar Announcement, 09/10/2013
Steinman Hall, Room #312
(Chemical Engineering Conference Room)
Professor Karen Daniels
North Carolina State University
Department of Physics
"Tiny Sandpiles: Flow-Stabilized Solids in Microfluidics "
Disordered microscopic (Brownian) and macroscopic (granular) particulate matter share many similarities in their geometric structures, yet differ in the inter-particle interactions and the degree to which thermal fluctuations play a role in their statics and dynamics. We have developed a technique for assembling a flow-stabilized solid, formed by flowing a colloidal suspension towards a flat-topped ridge within a microfluidic channel. The resulting heaps are characterized by two distinct phases: a solid-like bulk phase in the interior and a highly fluctuating, liquid-like state which exists along its leading edge. We observe that heaps only form above a critical flow velocity (Peclet number) and that they are destroyed by thermal rearrangements when the flow ceases. The suspension flow-rate determines the heap size via the angle of repose (up to 7 degrees, even though the particles are frictionless). For steady-state heaps, we determine a large linear-elastic regime, and measure the elastic modulus via compressions or expansions due to fluid pressure steps.
BRIEF ACADEMIC/EMPLOYMENT HISTORY
Professor Daniels received her PhD in 2002 from Cornell University and spent 2002-5 as a postdoctoral research associate at Duke University. She joined the faculty of North Carolina State University in 2005, and was promoted to Associate Professor in 2011. She was a 2007 recipient of an NSF Faculty Early Career Development Program (CAREER) Award, and a 2011 recipient of an Alexander von Humboldt Fellowship which provided support for a sabbatical leave to the Max Planck Institute for Dynamics and Self-Organization in Göttingen, Germany.
RECENT RESEARCH INTERESTS: