Studies On Microfluidic Sample Introduction Systems With Sampling Probes

Microfluidics is the science and technology that manipulate small (nL～fL scale) amounts of fluids in channels with dimensions of tens to hundreds of micrometer, which have been widely applied in analytical chemistry. Its objective is to integrate all of the modules performed in routine laboratories, including sample introduction, pretreatment, transportation, mixing, reaction, separation and detection, into a compact device to achieve the miniaturization, automatization and integration of the whole analytical systems, providing advantages of high throughput, low samples and reagents consumption and low cost. Nevertheless, one of the major bottleneck in the development of microfluidic analytical systems lies in world-to-chip interface, which means sample introduction from external systems (μL～mL scale) into microfluidic systems (below nL scale) is of great significance to microfluidics.This dissertation is dedicated to relate the development of microfluidic sample introduction techniques based on sampling probes and their applications in chip-based and capillary-based droplet analysis, as well as in thin layer chromatography (TLC).In chapter one, the development of sample introduction techniques based on sampling probes, and the recent progress in microfluidic droplet analytical systems were detailedly reviewed.In chapter two, a capillary-based droplet analytical system based on a capillary and a slotted-vial array (SVA) sample presenting device was built, which capable of producing multi-component droplets in the nanoliter range. The present system was applied in various droplet microreactors, to demonstrate its application potentials in chemistry, biology and medicine. In chapter three, a microchip-based droplet analysis system with a monolithic sampling probe was developed for the first time, to achieve high-throughput sample introduction for different samples in droplet-based analysis. The sampling probe integrating functions of sample introduction, merging with reagents and generating droplet, was employed to produce diverse droplet microreactors automatically and continuously by coupling with a SVA system. The performance of the system was demonstrated in evaluating protein crystallization conditions and screening inhibitors for enzyme reaction. A possible highest sampling throughput of 10,000 samples/h for different screening reagents could be achieved by using this sample introduction technique.In chapter four, a simple capillary based TLC system was developed. A tapered glass capillary packed with silica gel was used as sampling probe and chromatographic column for TLC. The performance of the system was demonstrated in the separation of Camag test dye mixture I and a traditional Chinese medicine-Folium Isatidis.