Chemicapacitive microsensors for detection of explosives and TICs

Seacoast Science develops chemical sensors that use polymer-coated micromachined capacitors to measure the dielectric permittivity of an array of selectively absorbing materials. We present recent results demonstrating the sensor technology's capability to detect components in explosives and toxic industrial chemicals. These target chemicals are detected with functionalized polymers or network materials, chosen for their ability to adsorb chemicals. When exposed to vapors or gases, the permittivity of these sorbent materials changes depending on the strength of the vapor-sorbent interaction. Sensor arrays made of ten microcapacitors on a single chip have been previously shown to detect vapors of organic compounds (chemical warfare agents, industrial solvents, fuels) and inorganic gases (SO2, CO2, NO2). Two silicon microcapacitor structures were used, one with parallel electrode plates and the other with interdigitated "finger-like" electrodes. The parallel-plates were approximately 300 μm wide and separated by 750 nm. The interdigitated electrodes were approximately 400 μm long and were elevated above the substrate to provide faster vapor access. Eight to sixteen of these capacitors are fabricated on chips that are 5 x 2 mm and are packaged in less than 50 cm 3 with supporting electronics and batteries, all weighing less than 500 grams. The capacitors can be individually coated with different materials creating a small electronic nose that produces different selectivity patterns in response to different chemicals. The resulting system's compact size, low-power consumption and low manufacturing costs make the technology ideal for integration into various systems for numerous applications.