Biological Applications of Surfaces with Extreme Wettabilities

Abstract

Surfaces with extreme wettabilities have become an increasingly popular topic due to their wide range of applications – from simply keeping dirt off clothing to oil-water separation in the event of an oil spill. In particular, these surfaces have been of keen interest for a diverse range of biological applications as they can be fabricated from biocompatible materials. First, a facile methodology involving fluoro-silanization followed by oxygen plasma etching, for the fabrication of surfaces with extreme wettabilities is discussed. Open channel, paper-based microfluidic devices fabricated using these surfaces with extreme wettabilities allow for the localization, manipulation, and transport of virtually all high- and low- surface tension liquids. This in turn expands the utility of paper-based microfluidic devices to a range of applications never before considered. These include, continuous oil-water separation, liquid-liquid extraction, open-channel microfluidic emulsification, micro-particle fabrication, the precise measurement of a mixtures’ composition, and cell patterning. Next, a particular paper-based microfluidic device is expanded upon for the detection of E. coli and all coliforms. Coliforms are one of the most common families of bacteria responsible for water contamination, and certain pathogenic strains can be extremely harmful, leading to death if consumed. Current technologies for detection are expensive, requiring bulky setups, and can take up to 24 hours to produce accurate results. In this work, we have created an integrated microfluidic coliform lysis and detection device, the first of its kind to demonstrate successful lysing on-chip as it can allow for the flow and control of both high and low surface tension. The fabricated, optimized microfluidic device was able to successfully detect E. coli, via the presence of the coliform-specific enzyme, β-galactosidase. These devices can be implemented for real world E. coli contamination detection in multiple applications, including food and water safety. Finally, antifouling and antibacterial surfaces have been of extreme interest due to a plethora of potential applications. Many natural oils, including tea tree oil, possess antimicrobial properties. However, these oils are typically volatile, and depending on the environment can evaporate from a surface within a few minutes to several hours. In this work, we produce long lasting antimicrobial surfaces by partially crosslinking different natural oils within a cross-linkable polymer matrix. The remaining free oil is then stabilized by the partially crosslinked oil, yielding an antimicrobial surface that can remain antimicrobial for extended periods of time. These surfaces exhibit significant reductions in attached bacteria and there is currently no other known antimicrobial surface with this combination of instant and persistent kill. Taken together, this thesis lays the building blocks for a plethora of current and future biological applications of surfaces with extreme wettabilities.