Rapid, Low-Cost, Microfluidic Thermocycler for High-Throughput Genetic Diagnostics

Conventional instrumentation for amplifying nucleic acids by the polymerase chain reaction (PCR), which involves repeated temperature cycling, suffers from slow heating rates (e.g., 3 C/s) and large, costly sample volumes (i.e., 50 μL). Performing PCR is often the most time-consuming step in genetic sample preparation for common procedures such as pathogen detection and forensics. Faster thermocycling can reduce overall runtime and facilitate time-sensitive analyses. Smaller reaction volumes require fewer expensive reagents. Efforts to miniaturize genetic sample preparation have been largely confined to glass devices that are relatively expensive and require elaborate fabrication methods. Landers [1] has used glass microchips fabricated by wet etching to perform PCR, in which volumes of approximately 270 nL can be cycled 25 times with a tungsten filament lamp in only 5 min. Other developments include the work of Yasuda [2] and Faris [3], using infrared laser radiation to perform real-time PCR in 10–30 nL droplets suspended in mineral oil with amplification times of 3.5 and 6 min, respectively. Still, these devices can only perform a single reaction at a time.