OVERVIEW

Small, low-cost, robust, reliable, and sensitive sensors are needed to enable the realization of practical and economical sensor networks. Although there are a large number measurands that are of interest for sensor-network applications (e.g., seismic, temperature, light, sound, magnetic, chemical, etc.), appropriate commercial sensors exist for many of these measurands. However, one prominent exception is the fact that appropriate chemical sensors are not available. It is for this reason that the sensor technology effort within CENS is researching the design, fabrication, and implementation of chemical sensors that have the specifications needed for sensor networks.

In order to have a targeted effort to develop chemical sensors for sensor networks, we have focused on one sensor-network application, namely monitoring soil contamination / habitat monitoring. To model the flow of contaminants in soil, miniaturized lab-based soil systems (i.e., designed on the scale of meters) are first used to simulate real-world macroscopic field tests. These lab-based test systems need an array of miniaturized chemical sensors to accurately monitor the flow of contaminants in the model. Microsensors developed for this application will first be used in the lab-based system that has a controlled environment. Once the sensors have the robustness needed they will be used for field tests. To further focus and simplify the initial sensor technology development, the specific chemical contaminant compound that will be monitored is nitrate.

OBJECTIVES

In order to detect nitrate in aqueous solutions with concentrations in the range of 1 to 100 ìM, the sensor technology development team is taking multiple approaches. Two efforts are focused on developing miniaturized and selective electrochemical sensors and one effort is focused on developing a microscale liquid chromatography (LC) system. The development of the electrochemical sensors are both near-term projects but will be highly tailored for nitrate detection. The development of the LC system is a long-term project but has the potential to be a general sensing system.