High speed MEMS device for sample preparation of bio agents in water
This paper describes an on-going effort to develop a MEMS device to deliver up to 1000X concentration for bio-agents in water using the traveling wave (TW) mechanism for the Joint Services Agent Water Monitor (JSAWM) program. The MEMS device has planar inter-digitated electrodes on the inside walls of the sample container. Low voltage traveling wave pulses are applied in preferred directions to create multi-dimensional electrostatic field transport and concentration of bio samples. The device can be optimized for rapid transport by proper matching of cavity dimensions, electrode pitch and sweep frequency to bio agent properties. Design considerations include bio agent charge enhancement, anti-adhesion to cavity walls, and optimal operation of the traveling wave mechanism. Efforts will be guided by computational prototyping where modeling serves to guide device design, development, and fabrication. This prototype may be interfaced to the front-end of JSAWM detectors. In this initial effort, several key technology challenges were successfully verified through proof of concept experiments using simulants for the three classes of samples. Specifically, simulants for toxin, virus and bacteria were: bovine serum albumin (BSA) and horse heart Cytochrome C (CYT C), Bacteriophage MS2, and Bacillus thurengiensis (for anthrax spore). Several findings are worth noting: charge enhancement may not be necessary in tap water as B. thurengiensis appears to have excellent electrophoretic mobility; and covalently bonded polyethylene glycol (PEG) coating on exposed surfaces may prevent bio-film buildup on insulator surfaces. More work is needed to fully determine functional coating systems for both conducting and insulative surfaces. A notable achievement is the successful design and initial fabrication of the vertically integrated cell (VIC).
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Lean, M. ; Hsieh, H. B. ; Voelkel, A. R. ; Jensen, J. L. High speed MEMS device for sample preparation of bio agents in water. 2nd Joint Conference on Point Detection for Chemical and Biological Defense; 2004 March 1-5; Williamsburg; VA.
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