Date of Award

Spring 4-19-2021

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Engineering

Advisor

Caitlin Howell

Second Committee Member

Michaela Reagan

Third Committee Member

Andre Khalil

Additional Committee Members

Douglas Bousfield

Richard Corey

Abstract

Research on novel materials to handling water- and airborne samples for biological threats analysis is in great demand due to the COVID-19 pandemic. Work conducted on a new field of material science, called liquid-infused surfaces, demonstrate strong potential for the handling and manipulation of biological samples. As a result of the field’s infancy, only a limited number of studies have explored how liquid-infused surfaces can apply droplet manipulation strategies to address real-world problems. Presented in this dissertation are two platforms that leverage liquid-infused surfaces to address the challenges associated with handling water- and airborne biological samples. When dealing with waterborne biological samples, the paper-based materials commonly used in point-of-care devices rely on capillary forces to drive droplet movement, but this mechanism can result in significant sample loss. To simultaneously localize and concentrate with minimal loss, liquid-infused surfaces were fabricated by infusing silicone release paper with polydimethylsiloxane oil. Functionality was provided by folding the polymer surfaces into 3D geometries of the sample which enabled clean separation into predefined locations. The liquid-infused surfaces permitted ~3.4-fold increase in concentration of bacterial samples within a material that resisted adhesion, enabling downstream analysis. To capture airborne biological samples, many current methods suffer from pathogen recirculation, harsh chemical extraction protocols, and retention of captured airborne pathogens. Here, liquid nets are explored as a new method of filter-based air sampling, focused on improving the release of capture bioaerosols. Liquid nets were fabricated with traditional liquid-infused surface materials, polytetrafluorethylene (PTFE) filters were infused with perfluoropolyether oil, as well as melt-blown polypropylene high-efficiency particulate air (HEPA) filters wetted with perfluoropolyether oil. The PTFE liquid nets significantly improved the rate at which the captured Escherichia coli aerosol droplets were transferred for culturing on agar plates compared to the bare PTFE controls. Similarly, results from the HEPA filters demonstrated that the liquid nets improved the release of the captured E. coli, in comparison to the bare HEPA filters. The improvements to bacterial transfer provided by liquid nets present a new filter-based air sampling method to capture and detect biological threats within the surrounding environment.

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