UC Berkeley

Microfluidic chips allow researchers to perform complex chemical and biological assays with less volume and in less time than comparable benchtop experimental formats. To date, many microfluidic chip designs have been developed that replicate macro-scale experimental techniques while increasing sensitivity and measurements density. Biochemical assays investigating the function of biological macromolecules have particularly benefitted from the ability to perform complex, micro-scale experiments that use expensive, often precious reagents in microfluidic devices; structural investigations of biological macromolecules also have benefitted from microfluidic approaches. For my doctoral work, I designed and fabricated microfluidic chips to carry out functional investigations of macromolecular interactions and for X-ray diffraction studies of microcrystalline samples. In the first phase of this work, microdroplet-based microfluidic devices were used to study the reaction kinetics of the protein DnaA with various DNA substrates. Despite successful device fabrication and calibration, attempts to study the rates at which DnaA can extend a single-stranded DNA substrate ultimately were unsuccessful due to technical issues involving poor sample behavior in-chip. These challenges led me to focus on a different problem; namely, how to deliver microcrystals to microfocus synchrotron and X-ray free electron laser beam sources. Using the knowledge of microfluidic technologies gained through designing microdroplet-based chips, I helped design a PDMS-based flow trap array for microcrystal capture and positioning, and I independently designed, fabricated, and tested a silicon nitride-based device for microcrystal harvesting and delivery to X-ray beam line endstations. Both chip designs provide a powerful new means for allowing data collection from challenging structural targets.