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A Combined Preconcentrator and Sensor for Live Water-borne Pathogens
Initiated: October 2002
Team: Art Pontau, Yolanda Fintschenko, Eric Cummings, Blake Simmons,
Camille Troup, Blanca H. Lapizco-Encinas
The proposed system is based on a recent discovery (US patent application filed) in which an electric field applied across a two-dimensional array of microfabricated insulating posts separates, isolates, and concentrates 0.1-10 micron particles dielectrophoretically, based on their physique: polarizability, geometry and structure. We propose to develop and demonstrate a system that continuously concentrates and filters particles from water samples at >1-liter per hour and provides the collected samples to a microfluidic separation channel. The concentrator works by a sequence of physically specific interactions:
1.) During collection, a moderately applied electric waveform dielectrophoretically excludes large particulates and debris from the device entrance and traps particles in size-specific zones of the device containing a high-volume, non-uniform array of insulating posts, while other solutes and water flow unimpeded to a waste stream.

2.) Trapped particles within a selected size range are released in a concentrate to a medium-volume array having a different applied waveform frequency and DC offset. Particles are re-trapped in zones of this secondary device that are specific to the internal physique of the particles. This trapping behavior should distinguish between living cells, dead cells, and inert matter in the same size range.

3.) Selected particles are then released to a tertiary low-volume dielectrophoretic sieve bearing an electric-field-generated conductivity gradient to further filter and select particles that physically respond to osmolality and conductivity, a live-particle signature.

4.) A sharply pulsed electric field lyses the selected cells, releasing their contents to a canonical microfluidic separation channel.

The coupling between the dielectrophoretic concentrator and an actual microfluidic separation channel will demonstrate the feasibility of this technology in practical water monitors based upon a wide range of separation and sensor technologies.

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