Development and Application of Disposable Microfluidic Devices for Bioassays

The research presented in this dissertation is focused on the development of polyester-toner (PeT) based microchip as a potential affordable, disposable microfluidic platform for medical diagnostics. Besides a brief review of current fabrication techniques for microfluidic devices, the fundamental concepts of flow control methods on microfluidic platform and the latest detection methods are introduced in Chapter 1. Chapter 2 describes a rapid, cost-effective fabrication method to realize the valving functionality on PeT microfluidic device, where laser printer lithography was employed to conveniently create hydrophobic toner valves providing tunable burst pressures in microchannel. Chapter 3 continues to focus on the development of the flow control on PeT microchip. A CD-sized five-layer PeT microfluidic device operated on an inexpensive and portable battery-powered centrifugal system was developed, providing all the basic fluidic control functionalities which are essential for conducting comprehensive biology assays. By simply controlling the rotation speed of the PeT microchip, sample and buffer can be aliquoted from 200 nL to 2 μL and serially-diluted by buffer in parallel. Additionally, in order to enhance the mixing process on the chip, a reciprocating mixing domain for improving the mixing of viscous biology sample was designed and characterized in Chapter 3. With the advantage of the flow control functionalities developed for PeT microchip, Chapter 4 describes an adaption of DNA-induced magnetic bead aggregation detection reaction to a CD-sized PeT microchip as a simple and high-throughput solution to enumerate the white cells in human blood. Furthermore, development of PeT microchip for PCR application using an in-house infra-red thermal control system was detailed in Chapter 5. PeT microchips with different samples throughput were designed and evaluated in terms of the temperature ramp rate, effectiveness of IR-PCR system for thermal cycle temperature control and PCR efficiency. The dynamic surface passivation for chip surface was devised so that PCR performance on PeT microchip is comparable to conventional glass microchips. Finally, feasible future research direction towards using PeT microchip as an integrated, commercialized platform for diagnostics is outlined in Chapter 6.