Date of Award:

12-2018

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Mechanical and Aerospace Engineering

Advisor/Chair:

Tadd T. Truscott

Abstract

This thesis examines droplets striking water repelling surfaces as well as the movement of a soil based bacteria under various light and heat conditions. Droplet impact studies have shown that introducing a macroscopic feature to a water repelling surface can reduce the amount of time that droplet is in contact with the surface. By manipulating water droplets to impact different sized needles at varying speeds, we present how a needle can induce a similar reduction in the residence time of the droplet to more widely studied features. Results show the spreading and lift-off characteristics of the droplet are dependent on the impact speed as well as the size of macroscopic feature.

A separate topic examines environmental motivators for mobility in a terrestrial cyanobacteria species called Microcoleus vaginatus. This cyanobacteria is indigenous to cold deserts, such as the Colorado Plateau or Mojave Desert in North America, and is essential to the health and preservation of the biological soil crust. These bacteria are the first organisms to grow in new soil, secreting a carbohydrate that acts as soil glue, thereby increasing soil adhesion. It has been shown that these bacteria will rise to the surface of the soil from their subsurface homes after rainfall, but it is unclear how they are able to make this journey. It is also unclear if other factors, such as nutrient levels or heat and light, affect their movement. Here we present an investigation of M. vaginatus’ response to light and heat in order to determine if these basic stimuli affect movement, thereby informing future restorative models.

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