Semiconducting metal oxides have been extensively studied as sensing materials for conductometric gas sensors. Nanostructured metal oxides integrated with miniaturized heating elements have been shown to exhibit particularly high sensitivity while maintaining low power consumption. However, the incorporation of nanostructured metal oxide films onto miniaturized heater-based sensing platforms commonly suffers from uncontrollability in film thickness and microstructure, which reduces sensor performance and fabrication reproducibility. We have developed a controllable and flexible method for the localized in situ growth of an ordered metal oxide hollow sphere 2D array directly on a microfabricated heater platform, which allows much improved controllability in the sensing material morphology and coverage. A resulting SnO2 hollow sphere-based microsensor shows high sensitivity and selectivity toward formaldehyde and extremely fast response and recovery. Furthermore, this method can be used to fabricate microsensors using a variety of metal oxides, including combinations of different metal oxides in multi-shelled hollow sphere arrays, for enhanced sensitivity and tunable selectivity.
Project end date: 07/05/17