Hydrodynamic Focusing for Improved Sensitivity of an Impedance Based Sensor for Cell Detection and Analysis

Hydrodynamic focusing was used to increase the sensitivity of an impedance-based biosensor. A modified T-junction channel allowed the focusing of conducting fluid from the top and sides by a non-conducting fluid from a single sheath stream. A 4-electrode impedance setup was used as it is less susceptible to electrode polarization at low signal frequencies. Impedance measurements performed before and after antibody mediated E. coli capture showed an increase in impedance. Optimum sheath-to-sample flow-rate ratios (FRR) for detection were between 50:2 and 100:2 μL/min. This label-free method, implemented in a microfabricated flow channel, is a powerful tool for cell detection and analysis.