Anna Harley-Trochimczyk

In Situ Localized Growth of Ordered Metal Oxide Hollow Sphere Array on Microheater Platform for Sensitive, Ultra-Fast Gas Sensing

A simple and versatile strategy is presented for the localized on-chip synthesis of an ordered metal oxide hollow sphere array directly on a low power microheater platform to form a closely integrated miniaturized gas sensor. Selective microheater surface modification through fluorinated monolayer self-assembly and its subsequent microheater-induced thermal decomposition enables the position-controlled deposition of an ordered two-dimensional colloidal sphere array, which serves as a sacrificial template for metal oxide growth via homogeneous chemical precipitation; this strategy ensures control in both the morphology and placement of the sensing material on only the active heated area of the microheater platform, providing a major advantage over other methods of presynthesized nanomaterial integration via suspension coating or printing. A fabricated tin oxide hollow sphere-based sensor shows high sensitivity (6.5 ppb detection limit) and selectivity toward formaldehyde, and extremely fast response (1.8 s) and recovery (5.4 s) times. This flexible and scalable method can be used to fabricate high performance miniaturized gas sensors with a variety of hollow nanostructured metal oxides for a range of applications, including combining multiple metal oxides for superior sensitivity and tunable selectivity.

Low power microheater-based combustible gas sensor with graphene aerogel catalyst support

This paper reports a microheater-based combustible gas sensor with ultra-low power consumption (1.4 mW) using pulsed heating and novel sensing materials. High surface area graphene aerogel is used as a support for platinum and palladium nanoparticles. Pulsed heating (450 °C) at a 10% duty cycle yields an order of magnitude reduction in power consumption with no loss of sensitivity. Sensing response to hydrogen and propane gas shows promising selectivity and order of magnitude faster response and recovery times (1-2 s) compared to previous work. The results indicate a high level of flexibility in creating selective, low power combustible gas sensors using this microheater platform and catalytic material system.