Modeling the sensing behavior of a MEMS field ionization device coupled with capacitive actuation

We present and model a miniaturized field ionization sensor associated with a MEMS actuation system. The sensor consists in parallel plates spaced by a few micrometers and metal nanowires added to one of the electrodes in order to enhance the electric field. A split bottom electrode is used to differentiate between the ionization field monitoring and the electrostatically-actuated gap spacing. Such device is aimed at gas sensing, whereas the tunable electrode spacing replaces the sensor array including several gaps required for gas mixture analysis. Finite element numerical simulations performed with COMSOL Multiphysics® indicate the existence of an optimal distance for both maximizing electrical field enhancement and minimizing interference between the two electric fields. Electrical measurements are focused on the I-V characteristics of ambient air. The influence of gap variation on the breakdown voltage is consistent with the theoretical analysis of the modified Paschen's law, considering direct electron field emission at microscale interelectrode gaps.