Research activity in chemical gas sensing is currently directed towards the search for highly selective (bio)chemical layer materials, and to the design of arrays consisting of different partially selective sensors that permit subsequent pattern recognition and multi-component analysis. Simultaneous use of various transduction platforms has been demonstrated, and the rapid development of integrated-circuit technology has facilitated the fabrication of planar chemical sensors and sensors based on three-dimensional microelectromechanical systems. Complementary metal-oxide silicon processes have previously been used to develop gas sensors based on metal oxides and acoustic-wave-based sensor devices. Here we combine several of these developments to fabricate a smart single-chip chemical microsensor system that incorporates three different transducers (mass-sensitive, 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 control and monitoring of the sensor functions, and enables on-chip signal amplification and conditioning that notably improves the overall sensor performance. The circuitry also includes analog-to-digital converters, and an on-chip interface to transmit the data to off-chip recording units. We expect that our approach will provide a basis for the further development and optimization of gas microsystems.

The sensing behavior of polymer-coated resonant cantilevers for mass-sensitive detection of volatile organic compounds was investigated. Industrial complementary metal oxide semiconductor (CMOS) technology combined with subsequent CMOS-compatible micromachining was used to fabricate a single-chip system comprising the transducers and all necessary driving and signal-conditioning circuitry. An analytical model was developed to describe the mass-sensing mechanism of polymer-coated resonant cantilevers. The model was validated by measurements of various gaseous analytes. As an exemplary application, the quantitative analysis of a binary mixture using an array of four cantilevers is described. Experimental results are given for the concentration prediction of a mixture of n-octane and toluene. Finally, it was established that the limit of detection achieved with cantilever sensors is comparable to that of other acoustic wave-based gas sensors.

No abstract

No abstract

No abstract

No abstract

No abstract

The paper reviews the state-of-the-art in the field of CMOS-based microelectromechanical systems (MEMS). The different CMOS MEMS fabrication approaches, pre-CMOS, intermediate-CMOS, and post-CMOS, are summarized and examples are given. Two microsystems fabricated with post-CMOS micromachining are presented, namely a mass-sensitive chemical sensor for detection of organic volatiles in air and a 10-cantilever force sensor array for application in scanning probe microscopy. The paper finishes with a look into the future, discussing key challenges and future application fields for CMOS MEMS.