Improving Indoor Air Quality With More Effective, Long-Lasting Sensors

Common household items like cleaning products, candles, cribs and makeup emit formaldehyde, a colorless, odorless chemical that has been found to be a risk to human health. But new low-cost technology from researchers at Carnegie Mellon University could help solve that problem by making indoor air quality sensors last longer and catch unsafe formaldehyde levels sooner.

“Indoor air quality is often overlooked,” said Albert Presto(opens in new window), director of the Center for Atmospheric Particle Studies(opens in new window) at CMU and co-author of a recently published paper(opens in new window) on the technology. “We want to better educate people on indoor pollutants, so that they can make informed decisions. Only then can we improve indoor air quality and eliminate the inherent health risks.”

Researchers were able to lengthen the lifespan of the air quality sensor by using a unique polymer coating that extends the sensor’s half-life by more than 200% and enables it to regenerate when its performance begins to degrade.

How the sensor works

The sensor uses MXene — a class of compounds that is good at storing energy and sensing gases. But MXenes are highly susceptible to oxidation, particularly when exposed to air and/or humidity. 

That poses a major challenge for MXene-based air quality monitors. The CMU researchers, led by Reeja Jayan(opens in new window), professor of mechanical engineering, addressed this problem by covering the MXene in a polymer coating. The team used a technique that vaporizes specific materials, which then form a nano-coating on the cold sensor in a way similar to how condensation coats the outside of an ice-cold drinking glass on a hot day.

Without the coating, the MXene sensor lasted for a little over two months. But when the polymer layer was applied, the sensor ran for more than five months. 

Shwetha Sunil Kumar, a Ph.D. candidate in mechanical engineering(opens in new window), said the coating also made the sensors better at detecting formaldehyde. 

“We found that our polymer layer allowed the sensor to detect lower levels of formaldehyde in the air,” Kumar said. 

The team also found that by adding humidity to the sensor at the end of its life it regained about 90% of its sensing ability.

Jayan is confident that these materials could be deployed to other devices to enhance lifetime and performance. She is currently developing similar technology(opens in new window) to extend the life and safety of batteries.