A Novel Monolithic MEMS Array for E-Nose Applications

In this letter, we present a novel monolithic microelectromechanical syste-ms (MEMS) matrix array that can be adapted for electronic nose (E-nose) applications. The proposed MEMS array consists of four heater rows and four sensing electrode columns, arranged in crossbars and resulting in 16 intersections, which sit on top of suspended membranes created by frontside isotropic dry etching. Power supply, fine-tuning, and wireless communication are integrated on a custom printed circuit board. Thin films of metal oxide are deposited on this matrix array via atomic layer deposition. The achieved E-nose is low power, ultrasensitive, fast, scalable, reliable, and repeatable. It responds to different volatile organic compounds (VOCs) through the identification of optimal operating temperature. For nitrogen dioxide, ethanol, and carbon monoxide (CO), optimal temperatures and measured lower detection limits are ∼150 °C, 6.67 ppb, ∼250 °C, 50 ppb, and ∼350 °C, 1 ppm, respectively. Calculated theoretical detection limits are orders of magnitude lower. At optimal conditions, response/recovery time is <1 min. By tuning temperature profiles, this E-nose can inherently separate VOCs in mixtures. The proposed array is a versatile platform, compatible with back end of line complementary metal–oxide–semiconductor (CMOS) technology.