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Chemical and electrochemical sensors and sensor arrays can be produced using microfabrication and micromachining technologies. These technologies permit the formation of three-dimensional structures and also produce geometrically well-defined, highly reproducible sensor prototypes. Most present chemical and electrochemical sensors operate using a single device for absolute measurements. There are many circumstances in which interference by other species, the signal-to-noise ratio, and/or the selectivity and sensitivity are less than desirable when using a single sensor. It is feasible to employ a differential mode of sensor operation to overcome these weaknesses. In the differential mode of measurement, a pair of identical sensors is used, with one sensor as the active device, and the other serving as a reference. The active device may incorporate an electrocatalyst, while the reference sensor does not.

In recent years, microelectronic fabrication techniques such as photolithographic reduction, thick and thin film and reactive sputtering metallization, chemical and plasma etching, etc. have been applied to the production of miniature and microsize chemical sensors. The introduction of solid electrolytes and conductive polymers further enhances the applicability of electrochemical and chemical sensors, particularly in a gaseous environment. Recent advances in micromachining technology also add new dimensions to the development of chemical sensors.