Date of Award

Spring 1-1-2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy In Chemical Engineering Degree

Department

Chemical And Biomedical Engineering

First Advisor

Wirth, Christopher

Second Advisor

Nolan Holland

Third Advisor

Dr. Petrus S Fodor

Abstract

Colloidal interactions play an important role in determining the macroscopic properties of different materials. Recent work in this area has focused on the role anisotropic particles play in these materials. This thesis summarizes work conducted on the dynamics and interactions of an anisotropic colloid particle near a solid wall. Specifically, the methodology for conducting Total Internal Reflection Microscopy (TIRM) on anisotropic colloidal systems near a boundary was developed. This new method is called “Scattering Morphology Resolved - TIRM” (SMR-TIRM). Simulations of the Brownian motion of a sphere comprising hemispheres of different composition (i.e. a Janus particle) very near a wall were conducted. Trajectories obtained from these simulations were used to construct 3D potential energy landscapes. Results showed that the potential energy landscape of a Janus sphere has a transition region at the location of the boundary between the two Janus halves, which depended on the relative zeta potential magnitude. In this thesis, an experimental technique for the direct and local measure of cap thickness of a coated Janus particle was summarized. It is found that the cap varied in thickness continuously along the perimeter ofthe particle. To better understand the impact ofthe coating on the dynamics of Janus particle, Brownian dynamics simulations to predict the translational and rotational fluctuations of a Janus sphere with a cap of non-matching density near a boundary was utilized. The simulation results show that the presence of the cap significantly impacts the rotational dynamics of the particle as a consequence of gravitational torque. vi In the last part of this thesis, the SMR-TIRM was used to map scattering from ellipsoid particles. The hypothesis driving this work was that evanescent wave scattering from an ellipsoidal particle depended on both the aspect ratio and orientation. Analysis of the light scattered from the particle showed that both ellipticity and directionality correlated with particle orientation and aspect ratio. In principle, these relationships will allow tracking of the particle’s position and orientation via the scattered light morphology.

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