Integration of electronic materials in microfluidic systems

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.