Microfluidic Technologies for High-Throughput Screening Applications

Abstract

In this thesis, I present a strategy for the design and development of microfluidic devices for high-throughput screening applications, such as mutant enzyme libraries expressed in prokaryotic hosts, where a few point mutations at the DNA level translates to hundreds of thousands of enzyme variants. The work falls into three main sections. Section I addresses fundamental research in polymer chemistry, where I explore the suitability of several polymers for microfluidic applications, examining properties such as molding, fluorescence, solvent compatibility, and adhesion/sealing to glass substrates. Section II describes my development of a two-phase microfluidic device, in which I report on crossflow-based dynamic formation of picoliter-sized water droplets in a continuously flowing oil-surfactant stream. A predictive model describing the fluid dynamics of droplet formation in this model is presented as well as its applications in screening bacterial populations. Section III reports the development of multilayer soft lithography technology using silicone rubber to build addressable high-density microfluidic arrays with thousands of integrated mechanical valves. This technology, which introduces the concept of fluidic large scale integration, is presented as a high-throughput parallel method to analyze bacterial enzyme expression at the single cell level. The detection of enzymatic activity in these high-density microarrays is described, comparing a self-constructed solid-state laser apparatus with a modified scanner (Axon Industries) used for looking at DNA arrays.