Chemical Sensor Research at NIST

Process Measurement Division, Process Sensing Group

Increasing global competition has placed new demands on the chemical process industry for more efficient use of materials, better process reproducibility, and environmental safety. Similar concerns are encountered in the automotive field where engine performance and reduced emissions are issues. Sensing devices that detect and quantify chemical species are expected to have a major impact in meeting measurement needs in these areas. The need for chemical measurements extends to many other applications as well, for example, home safety, food freshness, and medical applications. Meeting all of these demands requires a low-cost technology for the measurement of gas species, which can provide immediate, on-site analysis for the detection of reaction products, exhaust gases, leaks, etc.

The Process Sensing Group at NIST is investigating generic technology issues related to next-generation chemical measurements with solid state devices. A significant portion of the research uses a basic micromachined platform, known as a microhotplate to develop materials and new methods for detection and quantitation of gases. The microhotplate contains a built-in heater, thermometer, and sensing film. The device uses conductance changes in the sensing film to detect the presence of adsorbed gas species. Temperature changes may be used to alter the reaction kinetics between the gas and sensor surface. Because of the small size, millisecond temperature changes in the range 20 °C to over 500 °C are used to create response "fingerprints" for different analytes. Surface analytical and microcharacterization methods are also used to investigate materials properties and mechanisms for sensing.