Design and Fabrication of Wearable Sensors for the Measurement of Ammonia Concentration in Air

Exposure to emissions from combustion, farming, and industrial processes triggers asthma, cardiovascular disease, and lung inflammation. One of the primary goals for environmental surveillance and health-related research is developing a low-cost and high-performance wearable sensing platform that can accurately measure concentrations of gaseous pollutants, toxic industrial chemicals, and other chemical compounds that adversely affect human health. Specifically, occupational exposure to ammonia is significant for janitorial workers, miners, and agricultural workers, and the health effect of exposure to low ammonia levels (<1 ppm) is unknown because there are no wearable ammonia sensors sensitive enough for this type of measurement. This paper introduces a novel opto-electrostatic sensing mechanism that utilizes single-walled carbon nanotubes (SWCNTs) to fabricate lightweight sensors capable of detecting ammonia concentrations as low as 100 ppb. The high sensitivity of Nafion-doped SWCNTs makes them superior to commercially available sensors at a cost significantly lower than that of laboratory-grade analyzers. By directly addressing the shortcomings of existing sensor technology, our work positions portable ammonia sensors to improve safety standards in industries utilizing ammonia.