Title: Integration of electronic materials in microfluidic systems
Description: This thesis describes several approaches for integrating electronic components--in the form of wires, sensors, and actuators--and microfluidic structures in lab-on-a-chip systems. Lab-on-a-chip systems are devices that combine one or more laboratory functions on a single, compact chip that is typically just a few square centimeters in size. By operating on small volumes of fluid (10 -9 to 10 -18 liters), these devices can be used to carry out separations and detections with high resolution and sensitivity using very little sample and reagent. The high surface-to-volume ratios and short diffusion paths that are characteristic of these devices allow for rapid heating, cooling, and analysis of a product. The chips can be manufactured in high quantity at low cost, and compact designs make it possible to analyze--and dispose of--samples at the point-of-need, rather than a centralized laboratory. One of the challenges in developing the next generation of lab-on-a-chip systems is the addition of electronic function to the microfluidic channels. This dissertation describes the fabrication and integration of electronic components in polymer- and paper-based microfluidic systems, and introduces practical applications of these techniques.

Chapter 1, which serves as an introduction to the thesis, reviews the strategy of co-fabrication, or the injection of one or more materials in a single layer of microfluidic channels to provide function. Chapter 2 presents the technique of microsolidics, which uses poly(dimethylsiloxane) (PDMS) microfluidic channels as the template for building flexible, metallic wires. Chapter 3 and Appendix 3 describe the fabrication of electromagnets that can be used to control the flow of functionalized superparamagnetic beads in microfluidic channels. Paper is becoming an increasingly important substrate for microfluidic devices. Chapter 4 illustrates methods for building electrically conductive wires directly on and in paper and other fiber-based substrates to produce foldable printed circuit boards. Chapter 5 introduces a low-cost paper display, which can be applied to show the results of diagnostic tests for human disease. Quantitative collection of data from microfluidic devices is a challenge in the development of point-of-care lab-on-a-chip systems. Chapter 6 provides a technical overview of a portable spectrophotometer for low-cost and quantitative detection of the concentration of disease or test markers in solution. Chapter 7 describes application of the detector to quantify the results of immunoassays and other biochemical tests in resource-poor settings.