Design, fabrication and testing of thermal components and their integration into a microfluidic device

Microfluidics devices and Microsystems are gaining significant popularity as they provide attractive solutions to automate and miniaturize the handling of fluids, reagents and other fluids used in DNA sample preparation, synthesis and screening. These devices greatly enhance a multitude of potential applications in the areas of point-of-care diagnostics, pharmacogenomics, high-throughput drug discovery, forensics, food safety, plant genomics, agriculture and military applications. In this paper we discuss design, integration and testing of thermal components in a microfluidic device designed for on-chip genetic sample preparation. A typical microdevice must perform several operations to be capable of analyzing a sample of body fluid (blood, urine, saliva), extracting DNA from concentrated cells, hybridization, purifying and amplifying DNA, and finally detecting DNA fragments of interest. In conventional bench-top PCR thermal cyclers, samples are mixed in stationary vessels to about 100 L-. range and undergo a series of temperature shifts programmed to optimize the efficiency of each of the PCR steps. The time at a set temperature is the most critical component for each step. Reduction of the sample volume down to a few (.)Ls and improvement of the ramp times between temperature steps makes micro-PCR devices desirable. Thermal components such as heaters and resistive thermal devices (RTDs) are fabricated as an integral part of a complete genetic sample preparation micro-system. The ability to precisely control the temperature is a critical component of most microfluidic devices intended for on-chip genetic sample preparation Devices were fabricated and demonstrated a temperature variation of similar to 1degreesC over the entire sample volume. A design of the device, including chamber dimensions, placement of the heating and cooling elements will be presented. The results of temperature cycling experiments will be shown. We have measured the heating rate of similar to2.4degreesC A and the cooling rate of similar to2.0degreesC /s for devices tested under active heating/cooling control. Finally, a brief overview of relevant microfabrication methods will also be presented.