Levich Institute Seminar Announcement, 02/16/2010
Tuesday, 02/16/2010
2:00 PM
Steinman Hall, Room #312
(Chemical Engineering Conference Room)

Professor James F. Gilchrist
Lehigh University
Department of Chemical Engineering

"Particle Self-Organization in Thin Film and Pressure-Driven Flows"


ABSTRACT


Self-organization arises in systems when constituents having local repulsion are confined or have a long range attraction, resulting in rich phase behavior and/or pattern formation. However, it is generally unclear how these systems behave when subjected to deformation or when self-organization is coupled to the underlying flow. Two prototypical systems will be discussed, both of which have practical applications in device fabrication and suspension handling. Convective deposition of nano- and microscale particles is used to fabricate surface morphologies such as microlens arrays atop light emitting diodes (LEDs) to enhance the photon extraction efficiency by over 300% and various other energy, optical, and BioMEMS applications. The fundamental mechanism behind self-organization of these particles is particle attraction driven by the local capillary interactions of particles confined in a thin film of an advancing meniscus. We will highlight resulting morphology and various instabilities that occur during deposition of uni- and bimodal suspensions. We also investigate the competition between chaos-enhanced dispersion and self-organization of particle suspensions. In steady pressure-driven flows, self-organization occurs due to multibody hydrodynamic interactions, typically driving particles away from the walls toward the center of the channel despite the diffusive motion of the particles. In channels whose geometry induces flow in the transverse direction to the pressure gradient, direct competition between particle self-organization and mixing due to advection results in concentration profiles where the underlying 3D flow acts as a template for pattern formation. The internal structure of these suspensions is investigated in an attempt to elucidate the details of the interactions that result in self-organization. We demonstrate this interplay is critical in designing microscale devices that handle suspensions such as blood for BioMEMS.