Passive nanotechnology based sensors for the remote detection of environmental pollutants impacting public health

Carbon nanotube sensors offer sensitivity and compactness, and provide a versatile chemical platform for ambient monitoring of environmental pollutants such as ozone, ammonia and volatile organic compounds, known to cause acute respiratory health problems (e.g., exacerbations of asthma and COPD). The advances in electronics and the feasibility to interface complex sensor materials with low-resistance metallic contacts enable novel sensor configurations, such as passive nodes scattered on ground and remotely monitored by drones or radar. Under an NIH Grant, we are developing sensor arrays to detect ambient environmental triggers of respiratory diseases in the personal microenvironment. Our approach makes use of the unique electronic properties of single-walled nanotubes (SWNTs) and the tremendous potential to modulate their sensitivity and selectivity using tailored chemical functionalization to adsorb specific molecules. In this paper, we present the first results to demonstrate the feasibility of a completely passive SWNT-based ammonia sensor remotely interrogated by an instrumented monostatic radar. It is shown that the backscattered signal produces a unique resonant response that can be used as a marker for the gas detection.