Microfluidics is a powerful tool that is currently revolutionizing chemical and biological analysis. Rapid mixing of reactants is essential in many microfluidic systems to initiate biochemical reactions. Hence, microfluidic mixer, with the purpose to achieve rapid and efficient mixing of reactants, is the foremost and indispensable component in a microfluidic system for most applications in analytical chemistry and life science. This thesis mainly involves the development of novel ultrafast microfluidic mixing platforms and the utilization of the platforms coupled with the state-of-the-art optical detection and characterization techniques to study rapid self-assembly kinetics of protein folding and small organic nanoparticle formation.

First we developed a novel optical detection techn...[ Read more ]

Microfluidics is a powerful tool that is currently revolutionizing chemical and biological analysis. Rapid mixing of reactants is essential in many microfluidic systems to initiate biochemical reactions. Hence, microfluidic mixer, with the purpose to achieve rapid and efficient mixing of reactants, is the foremost and indispensable component in a microfluidic system for most applications in analytical chemistry and life science. This thesis mainly involves the development of novel ultrafast microfluidic mixing platforms and the utilization of the platforms coupled with the state-of-the-art optical detection and characterization techniques to study rapid self-assembly kinetics of protein folding and small organic nanoparticle formation.

First we developed a novel optical detection technique using two-photon fluorescence lifetime imaging microscopy (FLIM) to depict two-dimensional (2D) maps of ultrarapid mixing dynamics in microdroplets with high temporal and spatial resolution. The quantitative characterization technique is potentially applicable to the real-time kinetic study of biological and chemical reactions in droplet-based microfluidic systems. Then we built an ultrafast hydrodynamic focusing microfluidic mixer platform that allows us to observe and measure rapid chemical and biological reaction kinetics with timescale on the order of microsecond. Moreover, we combined the time-resolved fluorescence resonance energy transfer measurement with the ultrarapid hydrodynamic focusing microfluidic mixer as an exciting experimental tool to explore early protein folding with temporal resolution at microsecond level and structural resolution at Angstrom level. The developed tool can be readily applied to the study of early biological process with FRET engaged in the process. Furthermore, we established an ultrafast three-dimensional (3D) hydrodynamic focusing micromixer platform and measured the rapid kinetics of small organic aromatic molecule self-assembly in real-time. Finally, we built a 3D hydrodynamic flow focusing microfluidic platform that enables controllable formation of aromatic nanoparticles with tunable size and size distribution. Such microfluidic device with the ability to precisely control the convective-diffusion process and continuously vary the fluid flow condition is promising for studying the formation of nanomaterials.