Studies On Combination Of Sequential Injection With Microfluidic Separation And Reaction Systems

Despite the strong impetus in development of microfluidic analysis technique in the past decade, studies on sample introduction, change and pretreatment still appear to be a weak point. The sequential injection (SI) technique has played an important role for the automation of chemical analysis and on-line sample pretreatment. SI system can be readily automatized, and can provide steady fluid flow at relatively low flow-rates. Micro syringe pumps can be used to meter μL-level, or even sub-μL-level samples with high precision. The combination of SI with microfluidic system is a powerful means for sample introduction and pretreatment. In this thesis, systematic studies are conducted on combining SI system to microfluidic chip-based electrophoresis separation, microfluidic chip based-solid phase reaction and microfluidic chip-based PCR liquid phase reaction using conventional SI equipment for sample introduction.A SI-microfluidic chip-based electrophoresis separation system was developed featuring a non-interrupted continuous sample introduction with world-to-chip interfacing achieved by a falling-drop design. The interface was fabricated on the glass chip and allowed electrical isolation of the capillary electrophoresis system from the SI system. A novel miniaturized microfluidic chip analyzer was developed, for capillary electrophoresis separation with laser induced fluorescence detection, with simplified optics involving the use of optical fibers, capable of non-interrupted continuous sample introduction using a SI system. The performance of the system was demonstrated in the separation of Cy5 from impurities. Low carryover (<4%) between samples were achieved at a sampling frequency of 35/h with a precision of 1.9% RSD (n=11).In the SI-microfiuidic chip based-solid phase reaction system, a conventional sequential injection system was adapted for direct coupling with the microfluidic system integrated with a solid phase reactor. Difficulties owing to large difference in the scale of fluid manipulation between SI system and mcirofluidic system were overcome by reducing the volume and flow-rate during SI sample manipulation and increasing the structure dimension of the microfluidic system. A novel method for the immobilization of controlled-pore-glass based reactive particles on PDMS microreactor beds was developed, producing an on-chip solid phase reactor that featured large reactive surface and low flow impedance. Efficient mixing of reagent/sample/carrier streams was achieved by incorporating chaotic mixer structures in the microfluidic channels. The...