SEN1: A High-Performance Micromachined Amperometric Nitrate Sensor for Environmental Monitoring

A nitrate-sensing system that consists of a micromachined sensing chip, anion-permeable membrane, and integrated microfluidic channels has been designed, fabricated, assembled, and tested. Our microsensor was designed for in-situ monitoring of nitrate concentrations in ground water. Cyclic voltammery of nitrate demonstrates high sensitivity of silver in 0.01 M NaOH electrolyte. Thus, a silver microelectrode was patterned for amperometric nitrate detection. An electrochemically oxidized silver electrode was used as a reference electrode. Microfluidic channels were fabricated as flow paths to the microelectrochemical cell for the eluent (0.01 M NaOH) and ground-water sample. A polyimide insulation layer was deposited to protect lead-wires and electrodes from corrosion. The sensor also incorporates an anion-permeable membrane that is used for selective measurement