A miniaturized chemocapacitor system for the detection of volatile organic compounds

A miniaturized gas sensing system suitable for real life applications, consisting of an array of 8 polymer-coated capacitive sensors and low power read-out electronics is designed and realized. The chemocapacitor array is fabricated with standard microelectronics/micromachining processes allowing for the realization of planar InterDigitated Electrodes (IDEs) with 2 μm critical dimension. The read-out electronics sub-module consists of an analog multiplexer for the sequential measurement of the sensor array elements, a capacitance to 24-bit converter and a USB to I2C interface. The electronic sub-module developed, was evaluated against a standard capacitance meter and presents a noise of ∼0.2 fF and therefore capacitance signal (ΔC) of 0.6 fF (S/N = 3) is detectable. The compact module has been successfully applied in the detection of low concentrations of p-xylene and toluene, according to the international health standards, in the presence of humidity.