Room-Size Ozone Chamber Enables Real-World Sensor Testing with Human Subjects

Achievement date: 
2017
Outcome/accomplishment: 

A room-size EPA ozone chamber is making possible more realistic gas-sensor testing, which allowed, for example, the first-ever test of a room-temperature sensor being worn by a person. The test was conducted by scientists at the Engineering Research Center (ERC) for Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST), funded by the NSF and based at North Carolina State University.

Impact/benefits: 

Real-world testing is crucial to refining the new sensors being developed at ASSIST. In previous years, sensors were evaluated in a lab using a small, flow-through chamber. Successfully using the EPA ozone chamber not only gives scientists the ability to test with human subjects, but with fine control over ozone, temperature, and humidity.

Explanation/Background: 

Earlier ASSIST testing in the flow-through chambers subjected sensors to streaming air, rather than sensing air as it diffuses about a room in a fashion more typical of work conditions. The new tests have given scientists a better understanding of the surface reactions with ozone and water vapor of the nanoscale metal-oxide gas sensors developed at ASSIST and that are included in its Health and Environmental Tracker (HET). The wrist-worn trackers are an integrated, wearable system designed to monitor a user’s environment and health. The new tests have enabled techniques to improve sensor operation in high humidity and to reduce power consumption. In addition, management of UV light exposure and intermittent, low-temperature heating can extend sensor stability over long periods while maintaining low power levels suitable for portable applications. Moreover, humidity has a large impact on all metal oxide sensors. Water vapor in the air can vary substantially, while the mechanisms for water vapor interacting with metal oxide surfaces at low temperature are not well understood.

Scientists also derived data on small-motion artifacts that occur when a person wears the sensor, and have developed strategies to mitigate those disturbances.