Date of Award

2018

Degree Type

Thesis

Degree Name

Master of Science in Chemical Engineering

Department

Chemical and Biomedical Engineering

First Advisor

Wirth, Christopher

Subject Headings

Chemical Engineering

Abstract

The manipulation of colloidal particles via applying electric fields has been studied over the past 30 years due to the unique properties associated with the fabricated colloidal crystals. Most works in this field focused on utilizing an alternating current (AC) electric field with spherical particles. However, utilizing spherical colloidal particles as building blocks for complex microstructures has been challenging. Consequently, more recent work has shifted to employing complex colloids (anisotropic in nature) as building blocks for advanced materials. In our work, the phase diagram and the kinetics of assembling colloidal polystyrene ellipsoids under an AC electric field at low frequencies were studied. Specifically, the structure of colloidal ellipsoid ensembles under varying electric field potentials (0.5 V, 1.0 V, and 1.5 V) was measured at a periodically regulated frequency (30 Hz ~ 3000 Hz) and the same set of experiments was done for colloidal spheres as a comparable reference. Data suggested the approximate critical frequency for assembled particles depended on the aspect ratio and the inherent block anisotropy may impact the mesoscale structure. Additionally, the rate constant for the rapid aggregation of colloidal particles was calculated via the plot of singlet evolution at varying electric field conditions. Results showed an increase in applied potential and a larger aspect ratio for the colloidal ellipsoids both resulted in a larger rate constant.

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