(Invited) Microfabricated Sensors for Industrial, Health and Environmental Monitoring

Abstract

Introduction There remains a strong need for miniaturized, low-power gas sensors that can be deployed in wireless applications for improved environmental protection, for public health, and for safe and efficient operation of many industrial processes. Leveraging the microfabrication technologies and utilizing innovations in high surface area nanomaterials provide exciting opportunities towards low-power microchemical sensors. Approach One approach is based on a highly efficient microheater platform (Figure 1) with fast response and recovery times. The design, fabrication, and characterization of the microheater platform is described, with polysilicon as the heater material for moderate temperature [1] and silicon carbide [2] for improved reliability at high temperature operation. A small, isolated heated area decreases the required power consumption and a closed membrane facilitates easier deposition of sensing materials.The use of two-dimensional materials is attractive for gas sensing applications since they offer the highest possible surface area for gas interaction, leading to high sensitivity. Assembling these two-dimensional materials into three dimensions, such as aerogels, provides a low-density material with large number of interconnected pores that increases the surface area available in a given footprint while maintaining the properties of the few-layer sheets. Sensing materials for combustible and toxic gas detection have been developed based on ultra-high surface area aerogels [3-6]. Results and Conclusions By integrating these nanomaterials with our microheater platform, we have achieved fast and sensitive detection of several health and environmental pollutants. For combustible gas sensing, graphene or boron nitride aerogel acts as a scaffold for catalytic platinum or palladium nanoparticles [1,3]. Bare graphene aerogel, graphene aerogel coated with single to few-layer transition metal dichalcogenide (TMDC) sheets, and TMDC aerogels are used for toxic gas detection [4-8]. The microheater platform is also used for localized growth of nanocrystalline metal oxide sensing film. The fast thermal response of the microheater leads to rapid heating of the precursor, creating a highly porous film that is beneficial for toxic gas sensing [9,10]. The talk will end with current limitations and plans for future directions.