MEMS-based array for hydrogen sulfide detection employing a phase transition

The monitoring of hydrogen sulfide in biogas is crucial due to its highly corrosive properties. Most notably, the lifetime of heat and power generation machinery suffers from high levels of hydrogen sulfide. Here an approach to enable large-scale, low cost deployment of selective, quasi-continuous hydrogen sulfide detection systems is presented. A chip featuring three individually controllable hotplates has been developed for this purpose. Each hotplate device consists of a heating structure and an interdigitated electrode structure, which we use to control the temperature and determine the resistivity of copper(II) oxide nanospheres, respectively. The fundamental process to determine the hydrogen sulfide concentration is based on a phase transition that occurs in the temperature regime below 200 degrees C. The transition process may be reversed at temperatures above 300 degrees C thus resetting the sensing layer. However, the reversal takes times, which is why we use a total of six hotplates simultaneously to enable a quasi-continuous monitoring of the hydrogen sulfide concentration.