Smart single-chip gas sensor microsystem

Research activity in chemical gas sensing is currently directed towards the search for highly selective (bio)chemical layer materials, and to the desi gn of arrays consisting of different partially selective sensors that permi t subsequent pattern recognition and multi-component analysis(1-3). Simulta neous use of various transduction platforms has been demonstrated(4-6), and the rapid development of integrated-circuit technology has facilitated the fabrication of planar chemical sensors(7,8) and sensors based on three-dim ensional microelectromechanical systems(9,10). Complementary metal-oxide si licon processes have previously been used to develop gas sensors based on m etal oxides(11) and acoustic-wave-based sensor devices(12). Here we combine several of these developments to fabricate a smart single-chip chemical mi crosensor system that incorporates three different transducers (mass-sensit ive, capacitive and calorimetric), all of which rely on sensitive polymeric layers to detect airborne volatile organic compounds. Full integration of the microelectronic and micromechanical components on one chip permits cont rol and monitoring of the sensor functions, and enables on-chip signal ampl ification and conditioning that notably improves the overall sensor perform ance. The circuitry also includes analog-to-digital converters, and an on-c hip interface to transmit the data to off-chip recording units. We expect t hat our approach will provide a basis for the further development and optim ization of gas microsystems.