Sensors and Actuators B 120 (2007) 538–544 Single step cell lysis/PCR detection of Escherichia coli in an independently controllable silicon microreactor Cathy Ke ∗ , Ann-Marie Kelleher, Helen Berney, Michelle Sheehan, Alan Mathewson Tyndall National Institute, Lee Maltings, Prospect Row, Cork, Ireland Received 13 December 2005; received in revised form 2 March 2006; accepted 9 March 2006 Available online 5 May 2006 Abstract Our studies describe a novel microreactor capable of single step microbial assays involving cell lysis and DNA amplification. The device with an integrated platinum heater and temperature sensor, was fabricated using conventional silicon fabrication technologies and then anodically bonded to a Pyrex lid. Finite element analysis (FEA) and experiments have shown that the temperature uniformity in the microreactor reaction cavity is homogeneous and that the microreactor is capable of fast thermal cycling with heating and cooling rates of 11 and 2.7 ◦ C/s, respectively. The microreactor has novel design features, such as a thermal isolation channel which eliminates thermal cross talk and an inlet/outlet port designed for ease of use. The fabricated microreactor was successfully characterised using a multifunction microbial assay involving cell lysis and PCR in a single step. An assay time of 32 min was achieved. © 2006 Elsevier B.V. All rights reserved. Keywords: Silicon microreactor; Cell lysis; PCR; Thermal cross talk 1. Introduction In the last decade, several DNA analysis systems have been developed [1–3] capable of DNA hybridisation, polymerase chain reaction (PCR) and DNA electrophoresis. Miniaturisation of silicon devices capable of DNA analysis has several advan- tages, namely lower cost, lower reagent volume and shorter sample analysis time. The PCR process which is widely used in genetic analysis and microbial detection has been optimised for use in several materials including glass, plastic polymers, silicon and PDMS. The first silicon fabricated PCR chip was published in 1993 [4] and since then, several features of the PCR chips have been optimised, in an effort to improve assay speed. These features have included reduction in adsorption of PCR reagents to the microchamber walls, reducing evaporation and more effective heat dissipation [5–9]. The increased miniaturisa- tion of the PCR microchips has increased temperature ramping rates, reduced sample volumes, improved sensitivity and low- ered power consumption. Furthermore, the adoption of standard IC technology decreases manufacturing cost and reduces pro- ∗ Corresponding author. Tel.: +353 21 4904441. E-mail address: cathyke2004@yahoo.com (C. Ke). duction time. While the optimisation of the function of individ- ual reactors leads to improved assay times for individual assays, it is necessary to fabricate an array of optimised microreactors to achieve high throughput. A number of microreactor systems assembled in an array format have been demonstrated recently [10–15]. A low volume microchamber array having a silicon substrate was used successfully for DNA amplification. Since it is difficult to eliminate thermal cross talk in silicon, other materials such as plastic or PDMS have been used to construct microchamber arrays for DNA amplification [16]. However, plastic has a disadvantage because it has low thermal diffusion and therefore a slow thermal conduction speed. This makes it unsuitable material for microchambers when a short cycle time is required. In recent years, very high throughput DNA array chips have been developed to study DNA expression, gene muta- tions and polymorphisms. While DNA hybridisation occurs at the same temperature for many different gene targets, the devel- opment of in-chamber PCR arrays has been more technically challenging since PCR conditions vary slightly from one gene target to another. To generate microreactor arrays suitable for the analysis of multiple gene targets, it requires the fabrication of a thermally isolated microreactor array. Such microreactors can be programmed independently with gene specific PCR conditions. One strategy that has been employed to suppress thermal cross 0925-4005/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2006.03.019