M. Allen Northrup, Ph.D.
Microtechnology Center, L-222; Lawrence Livermore National Laboratory, Livermore, CA 94551

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Significant advantages can be attained by miniaturizing components of diagnostic instruments. Theory predicts huge gains can be made in efficiency and speed of analysis for chemical separation systems such as those used in chromatography and electrophoresis, and several research groups are taking advantage of these favorable scaling laws. Similar advantages are afforded for the miniaturization of chemical reactors allowing for new levels of performance and efficacy. We will show how these advantages are being used to build a miniature, low-cost, low-power, and high efficiency PCR instrument.

In this report we detail the design and development of a miniature thermal cycling instrument for performing and detecting the polymerase chain reaction (PCR) that uses microfabricated, silicon-based reaction chambers. Several different reaction chamber designs have been modeled, built, and tested. Each design incorporates an integrated thin film heater, passive silicon cooling surfaces, and optical windows for detection of the reaction. A highly efficient, battery-operated controller has been implemented that shows significant improvements over commercial thermal cycling instrumentation. We have named the instrument the Miniature Analytical Thermal Cycling Instrument (MATCI) for convenience. The following technical demonstrations have been accomplished with the MATCI: 1) low power operation (average 1.2 W per reaction chamber), 2) high cycling speed (10x commercial instruments)

with high product specificity, 3) multiplex (8 simultaneous amplicons), PCR, 4) real-time detection of DNA production with an LED and photodiode/CCD in the miniature system, 5) specific probe, energy-transfer-based detection of PCR product production (commercial system for the beta actin gene on human genomic DNA) with the diode detection system, 6) immobilized probe, reverse-dot-plot detection of products, 7) rapid amplification of viral, human genomic, and pathogenic bacteria targets, 8) the functionality of disposable plastic liners and 9) the integration of microPCR and microelectrophoresis (20 minute amplification and 1 minute separation/detection of the product). The results from the MATCI indicate a new ability to perform detailed studies of the reaction kinetics and improve the efficiency of this important diagnostic technique. Due to the use of microelectromechanical systems (MEMS) technology, we have shown that low-cost, portable, DNA-based, biotechnological and clinical diagnostic instrumentation is a reality.