Ultra-Low Power Gas Sensor Based on a 3D Array of Nanogaps

This paper reports the achievement of ultra-low-power operation under 10 nW by utilizing a wake-up function through a 3D-nanogap (~5 nm) structure consisting of 16×16×2 and 25×25×2 isolated conducting plate arrays. This 3D-nanogap structure improves the previous 2D-one by establishing multiple parallel possible conduction paths in 3D. It thus results in lower operation voltage down to a level (<3.7 V) compatible with a conventional rechargeable Lithium-ion battery. Such an improvement is crucial in enabling consistent and straightforward integration through a battery to various energy harvesters to realize a self-sustainable gas sensor node. Two different 3D-array-based nanogap sensors were fabricated, holding dimensions of 16×16×2 and 25×25×2. The fabricated 3D-nanogap sensors showed (1) that the operational voltages were reduced by 50% from 5V to 2.7 V in comparison to the 2D counterpart and (2) that it successfully detected a VOC (volatile organic compound) of hexanal at a power consumption of only 4 nW.