CMOS gas sensors and smart devices

In this paper we review developments in the last decade towards making silicon-based gas sensors and smart sensor systems. A range of different transduction principles is considered and the technologies that underpin them. We also examine the need for a smart interface. Sensor interfaces usually take the form of electronic circuitry and so we discuss the possibility of making low-cost, integrated gas sensors using CMOS technology. This approach naturally leads, in to the description of smart devices and interfaces both for on-chip compensation of some of the "curses of chemical sensors" namely, environmental stability (sensitivity to ambient temperature, humidity etc.), and poisoning. However, in its wider sense there may be the need to interface, say, a high-pressure microfluidic system in a complex micro-GC unit or a high-voltage ion source in a quadrupole micro-MS. We complete our review progress in analytical instruments-on-a-chip.