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Forensic sample analysis on a microchip either dithiothreitol or tris(2-carboxyethyl)phosphine circumvented the chromatographic DNA extraction step. In order to generate a short tandem repeat (STR) profile for a suspected rapist, the researchers incorporated a PCR step. Although microdevices created by other groups have integrated elements that provide heat and sense temperature, these microchips are expensive and very difficult to microfabricate, says Landers. “When you look at what [clinical laboratories] pay for diagnostic tests, they want tests done for a few dollars per test at most,” he says. Therefore, his group developed a novel noncontact heating and temperature-sensing system using two external and reusable IR lamps. The bottom lamp heats the DNA solution, and the top lamp allows for 10 m the measurement of solution temperature using extrinsic Fabry–Perot interferometry. With this setup, the team demonstrated on-chip PCR amplification for a variety of genetic markers on a device that Landers estimates would cost
