290421 The Presence of Pseudo-Depletion Attraction in Micro-Particle Systems

Monday, October 29, 2012
Hall B (Convention Center )
Laura Blevins, Chemical Engineering, UMBC, Baltimore, MD; Chemical Engineering, UMBC, Baltimore, MD

Micro-particle based colloidal crystal structures serve as a potential architecture for biological applications due to their physiologically relevant particle/void sizes. A thorough understanding of the mechanisms
governing their arrangement is imperative for fine-tuning the structures and improving their overall quality. This work investigates the forces that form hexagonally packed colloidal structures of these "large" particles by means of artificial thermalization. Prior studies of analogous systems on the sub-micron and nano-scale indicate that depletion attraction forces dominate the particle organization, but are negligible for larger particle systems, such as those examined here. In this study, we analyze the relative influence of capillary forces versus a "pseudo-depletion attraction" -- that is a consequence of our artificial thermalization -- on the packing structure of micro-particles for mono-dispersed, binary, and tertiary systems. The resulting structures demonstrate ordered hexagonal packing. These results suggest that both capillary action and a force similar to that of depletion attraction contribute significantly to the character of micro-scale colloidal structures. 

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