Nanoparticle Diffusion, Aggregation, and Fractal Growth in Fluid Smectic Membranes

Undergraduate Honors Thesis

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Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/p2676w188

Abstract

Membranes can be found in many biological systems and the transport and diffusion of inclusions, especially nanoparticles, in such membranes is important in understanding many biological processes. Additionally, the unique two-dimensional (2-D) nature of membranes makes them an ideal system in which to probe the limits of 2-D hydrodynamics. We observe directly the diffusion and aggregation of nanoparticles (buckyballs) embedded in thin, freely-suspended smectic A films of 8CB liquid crystal using reflected light microscopy in order to better understand the hydrodynamics of inclusions in finite, two-dimensional fluids. The growth of buckyball aggregates has been measured using time-lapse video, and is seen to have an effective radius that increases linearly with time. Large buckyball fractals form in the final stage of the aggregation process. The measured fractal dimension of these objects suggests that the aggregation is a diffusion-limited process and yields an approach to characterizing the stickiness of different particles by their final fractal dimension. Measurements of the diffusion of buckyball aggregates at varying stages in the aggregation process yield mobilities that deviate significantly from theoretical predictions for single inclusions. Similar behavior is observed in several high density systems, which suggests that the higher inclusion mobilities may be a result of crowding.

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