Nanotech 2011

Dynamics of Assembly of Colloidal Particles at Liquid Interfaces (invited presentation)

D.M. Kaz, R. McGorty, G. Meng, M. Mani, J. Fung, V.N. Manoharan
Harvard University, US

Keywords: colloid, interface, self-assembly

Abstract:

A wide variety of material microstructures have been created using liquid interfaces as the template. Our understanding of how to design these microstructures is based largely on equilibrium models for the binding energy and position of particles at the interface. But we know little about the dynamics of binding and assembly. I will discuss experiments in which we track micron-sized colloidal particles as they adsorb to and assemble on oil-water interfaces. We find that the dynamics of adsorption are more complicated than anticipated. Sometimes we see particles stick to but not penetrate a planar interface. When they do penetrate, they take a long time to relax – at least several seconds and possibly even hours or days. The results call into question whether equilibrium models are relevant for many particle-interface systems. Because the slow adsorption causes the interactions between particles to vary over time, we have designed a system in which particles bind to the interface through a depletion interaction rather than by surface tension. We study the assembly of particles on emulsion droplet interfaces, and we find that nucleation and growth on the spherical interfaces leads to microstructures characterized by interconnected, asymmetric crystalline domains.
 

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