Date of Award

Spring 1-1-2020

Degree Type

Thesis

Degree Name

Master of Science In Chemical Engineering Degree

Department

Chemical And Biomedical Engineering

First Advisor

Wirth, Christopher

Second Advisor

Dr. Nolan Holland

Third Advisor

Dr. Shawn Ryan

Abstract

Active Janus particles experience autonomous motion at scales where Brownian stochastic fluctuations typically dominate trajectories. This autonomous motion further drives a broad range of collective behavior in simple and complex environments. Such behavior of synthetic particles has been shown to closely mimic that of motile biological systems. Furthermore, active Janus particles have potential to drive innovation in existing applications, including transport in microscale environments. Herein, I will describe a series of experimentsthat delve into the ensemble behavior of active platinum-coated Janus particles, specifically, the influence of hydrogen peroxide and depletion forces on their clustering dynamics. These experiments are part of an effort to understand the influence of propulsion speed on collective behavior. I found the extent of clustering increased as hydrogen peroxide concentrations increased in the absence of depletion interactions. Depletion interactions, introduced by the addition of PEG, had a duel effect. At low volume fractions, the addition of PEG increased the probability of observing clusters by enhancing particle-to-particle attraction and cluster longevity. Yet, at high volume fractions where depletion interactions are previously known to quench swimming speeds, the extent of clustering was reduced as result of a diminished collision probability. These observations and conclusions reveal the nuanced affects ~kT scale interactions have on the collective behavior of propelling Janus particles.

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