Center for Embedded Network Sensing

A highly sensitive and miniaturized amperometric nitrate sensor for groundwater monitoring was successfully designed, fabricated, and tested. The silver sensing electrodes were patterned on the silicon substrate with microfabrication techniques. The sensor was thoroughly characterized and the performance is very promising. A low detection limit of 4 ,#61549;M, wide dynamic range of 10000 ,#61549;M with excellent linearity (r2=0.99), and a good selectivity (13.9 % increase in signal for 400% increase of interfering ion concentration) were achieved and yet sensor is in a small form factor (4��×4��×3 cm without electronics). Many efforts have been being made to improve the sensor reliability and operational lifetime, such as including polymer-coated Ag/AgCl reference electrode. To enable real-time field measurements, a sample-preparation system, an automated sample-handing system, and a micropotentiostat with built-in pumps and valves controller have also been studied. In order to overcome limited life-time of the thin-film working electrode, a palm-sized sensor system that consists of macro-scale commercial electrodes, Plexiglass housing, built-in microfluidic channels, and anion-permeable membrane, have been developed.