Confinement of Colloidal Suspensions in Cylindrical Geometries and the Decoupling of Rotational and Translational Diffusion in a 2D Granular Experiment Open Access

Saklayen, Nabiha (2012)

Permanent URL: https://etd.library.emory.edu/concern/etds/2f75r905d?locale=en
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Abstract


Abstract
Confinement of Colloidal Suspensions in Cylindrical Geometries and the Decoupling of
Rotational and Translational Diffusion in a 2D Granular Experiment
We study binary colloidal suspensions confined within a glass microcapillary to model the glass
transition in confined cylindrical geometries. We use high speed three-dimensional confocal
microscopy to observe particle dynamics. The use of a slightly tapered microcapillary enables us to
probe a range of local volumes for a single colloidal sample. We observe that confinement of the
sample slows down particles. In addition, the particles form layers against the capillary walls; these
layers also influence particle mobility. We split the mobility into three components and see that all
components slow down close to the boundary. As the microcapillary is made smaller, all three
components of mobility start to show large fluctuations due to the closely packed layers that form
in tight spaces. We found that when the volume fraction is increased, the "bulk" mobility of the
system decreases.
We also experimentally study the rotation and diffusion of granular clusters in a 2D binary granular
system. Our apparatus vibrates a 2D system of densely packed granular bidisperse disks (to avoid
crystallization) containing a trackable 3-particle cluster. We use this system to mimic hard-sphere
fluids and the clusters probe the system's local translational and rotational dynamics. As the area
fraction of the bidisperse disks is increased, diffusion within the sample becomes slower, and above
a critical area fraction, the sample behaves as a granular glass. We analyze the rotational and
translational motions of the clusters to determine whether they decouple with changing area
fraction of the system. As we approach the glass transition, we observe a decoupling between the
two motions.

Table of Contents

List of Figures 1


1 Chapter 1: Introduction 3


1.1 Jamming and the Glass Transition 3


1.2 Confinement of Colloids 5


1.3 Decoupling of Rotational and Translational Diffusion 7


1.4 Particle Tracking 9


2 Chapter 2: Confinement of Colloids in Cylindrical Geometries 11


2.1 Experimental Details 11


2.2 Results 18


2.3 Conclusion 37


3 Chapter 3: Decoupling of Rotational and Translational Diffusion


in a 2D Granular Experiment 39


3.1 Experimental Details 39


3.2 Results 46


3.3 Conclusion 65


4 Chapter 4: Conclusion 67


5 References 70


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