Yang, Shenyang (2016-12). Microfluidics Based Droplet Gradient Generator for Screening Microalgae under Various Culture Media Conditions. Master's Thesis.
Thesis
Microalgae has attained great interest as a future renewable energy source. However, the production cost of microalgae based biofuel is still not economically competitive compared to fossil fuel and food crops and oil seeds. As a result, microalgae based second generation biofuel requires a significant improvement. One strategy to achieve this is the optimization of their cultivation conditions that can provide both high cell growth and oil production. Here, this thesis will present a versatile droplet microfluidics based gradient generator, it is capable of adjusting culture media composition, which allows for studying the effect of nutrient conditions on microalgal growth. The developed platform entails droplet microfluidics where a large number of single-cell encapsulated droplets can be generated and utilized as independent bioreactors. The platform consists of a droplet gradient generator and a downstream culture chamber. In the droplet gradient generator, a mixture of two different culture media solutions, each containing cells, was used as input solution. While maintaining a total flow of the mixture into the droplet generator, only the mixing ratio of those two solutions was changed by adjusting flow rates between them, droplets of time dependent concentration could be generated. This flow rate change is automatically controlled by a LabVIEW program, enabling to manage a step size and time interval between each change. In the downstream culture chamber, a serpentine channel structure is utilized to store droplets in sequence and track their growth and oil production over time. The gradient generation in the platform was first characterized with FITC solution where a linear profile of fluorescent intensity distribution was observed. Also by manipulating the step size and time interval, a gradient of concentration with different concentration range was easily adjusted. This platform is currently being utilized to analyze the growth of Chlamydomonas reinhardtii under different nitrogen concentrations.
