Sample concentration and impedance detection on a microfluidic polymer chip.

We present an on-chip microfluidic sample concentrator and detection triggering system for microparticles based on a combination of insulator-based dielectrophoresis (iDEP) and electrical impedance measurement. This platform operates by first using iDEP to selectively concentrate microparticles of interest based on their electrical and physiological characteristics in a primary fluidic channel; the concentrated microparticles are then directed into a side channel configured for particle detection using electrical impedance measurements with embedded electrodes. This is the first study showing iDEP concentration with subsequent sample diversion down an analysis channel and is the first to demonstrate iDEP in the presence of pressure driven flow. Experimental results demonstrating the capabilities of this platform were obtained using polystyrene microspheres and Bacillus subtilis spores. The feasibility of selective iDEP trapping and impedance detection of these particles was demonstrated. The system is intended for use as a front-end unit that can be easily paired with multiple biodetection/bioidentification systems. This platform is envisioned to act as a decision-making component to determine if confirmatory downstream identification assays are required. Without a front end component that triggers downstream analysis only when necessary, bio-identification systems (based on current analytical technologies such as PCR and immunoassays) may incur prohibitively high costs to operate due to continuous consumption of expensive reagents.