Analysis of MEMS cantilever sensor for sensing volatile organic compounds

Abstract

Increased concentration of Volatile Organic Compound (VOC) in environment can cause severe health issues and create the ozone layer at ground level. The increased concentration of ozone at the ground level creates the smog which will affect the biodiversity of mother earth, environment and human health in many ways. Many researchers have persuaded the continuous research on miniaturized sensors to detect the VOC with high sensitivity and selectivity. This paper presents the design and fabrication of MEMS cantilever sensor to sense VOCs viz., acetone (C3H6O) and Isopropyl alcohol (C3H8O). Here, the metal oxide films of Poly-vinyl-pyrrolidone (PVP) and Amino-propyl-tri-ethoxy-silane (3-APTES) having 600 nm thickness is deposited on oxidized p-type Si surface by RF sputtering process. The cantilever structure of 128 μm length, 80 μm width and thickness 600 nm is designed having a sensor area of 10,240 μm 2 . With this design specification the sensor is simulated in COMSOL Multiphysics software. Then, the sensor is fabricated using surface micromachining technique. The detection of VOCs is carried out by omnicant instrument. Here, the detection sensitivity of PVP and 3-APTES towards Acetone and Isopropyl alcohol are analyzed. The experimental results show that, PVP coated sensor performs 39% increase in sensitivity as compared to 3-APTES coated sensor to detect acetone, and 3-APTES coating sensor exhibit 7.5% increase in sensitivity to detect Isopropyl alcohol as compared to PVP coated sensor. • The cantilever sensor is designed in COMSOL Multiphysics and fabricated using surface micromachine technique. Then the fabricated sensor is tested in the omnicant instrument. By this experimentation following results and conclusions are drawn. • The coating material PVP and 3 APTES is tested against acetone and Isopropyl alcohol. The sensitivity of PVP with acetone is found 39% greater than sensitivity of 3-APTES with acetone. The sensitivity of PVP with isopropyl alcohol is 7.5% greater than 3PATES with Isopropyl alcohol. • The sensitivity of cantilever sensor is directly proportional to length and inversely proportional to the thickness of the cantilever beam. • The sensitivity is directly proportional to thickness of coated material on the sensor surface. The metal oxide film PVP is the preferable coating material to detect VOC Acetone. 3-APTES is preferable coating material to detect the Iso propyl alcohol.