Fabrication, solute transport characterization and biological application of a microfluidic gradient chamber

Natural systems such as soil and groundwater contain a diverse array of microenvironments that are rich in physical, chemical, geological, and biological heterogeneity. Anthropogenic chemicals such as antibiotics, heavy metals, and chlorinated solvents released to soil and groundwater are distributed in these microenvironments, and their attenuation often depends on microbial transformation. At elevated concentrations, these pollutants can be toxic, or at a minimum induce stress in microorganisms. Understanding microbial response to these stressors is key for mitigating their impact. In this study, a microfluidic gradient chamber (MGC) was fabricated to simulate environmental stressors in subsurface microenvironments. The MGC was fabricated in 4-inch silicon wafers using standard photolithography methods. Solute transport and microbial growth in the MGC was monitored and characterized by epi-fluorescence microscopy. Results show that by varying flow rates across the boundary flow channels, advective or diffusive transport processes control the generation of solute concentration gradients across a 1200-well array, and concentration gradients of stressor chemicals can be controlled. A strictly anaerobic methanogenic archaea species (Methanosarcina acetivorans) was grown in the MGC by introducing high salt media along the two boundary channels. The M. acetivorans produced a large amount of methane gas, which ultimately displaced the liquid media in the 1200-well array, rendering the MGC non-functional. The results of this study are a detailed set of procedures for fabricating the MGC, characterization of chemical concentration gradients in the MGC as a function of flow rate, and experimental methods to successfully grow anaerobic microorganisms in the MGC. This work forms the basis for future efforts that will focus on exploring the microbial response to stress-promoting concentration gradients.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Environ Engr in Civil Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Alcalde, Reinaldo

Contributors dc:contributor

• Werth, Charles J.

• microfluidics
• solute transport
• stressor gradients
• Methanosarcina acetivorans

Statement dc:rights

• Copyright 2014 Reinaldo Alcalde

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/72824

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/72824