A microfluidic device for label-free detection of Escherichia coli in drinking water using positive dielectrophoretic focusing, capturing, and impedance measurement.

Abstract While sensors that allow for high-throughput enumeration of microorganisms within drinking water are useful for water quality monitoring, it is particularly challenging to accurately quantify microorganisms that are present in low numbers ( Escherichia coli detection system that is integrated with a focusing and sensing electrode. By incorporating a passivation layer, we avoided issues with adhesion of E. coli to the electrode, and achieved efficient cell focusing under high flow rate conditions (1500 μL/h). The resulting focused E. coli cells were then trapped on the sensor electrode, resulting in changes in impedance. The proposed system was evaluated using four different E. coli populations (150–1500 CFU/mL). We successfully enumerated populations as low as 300 CFU/mL within 1 min, and the signal variation was 1.13±0.37%. The device introduced in this study provides the basis for the development of portable, highly sensitive microorganism sensors that enable rapid detection of bacteria in drinking water.