Many everyday items in your home—from candles and cleaning sprays to furniture and cosmetics—can release formaldehyde, a colorless, odorless gas that may pose health risks even at low levels.
Breathing in formaldehyde at concentrations above 0.1 parts per million (ppm) has been linked to health problems, including respiratory issues and even cancer over long-term exposure.
To make it easier and more affordable to monitor this invisible threat, researchers at Carnegie Mellon University have created a new type of formaldehyde sensor designed for indoor use.
What makes this sensor stand out is its special polymer coating, which significantly extends the sensor’s life and even allows it to regenerate when it starts to wear out.
The sensor is based on a material called MXene—a class of compounds known for their excellent electrical properties and ability to detect gases. MXenes are already being explored for use in batteries, filters, and sensors.
However, MXene-based devices have a big weakness: they don’t hold up well when exposed to air or humidity, which causes them to break down quickly.
To solve this, the Carnegie Mellon team developed a new method to protect the sensor.
They used a technique called Chemical Vapor Deposition (CVD), where hot vaporized chemicals are pumped into a vacuum chamber and form a thin, invisible layer over the cold surface of the MXene sensor—similar to how water condenses on a cold glass.
This nano-scale polymer coating acts like a shield, keeping out oxygen and moisture that would otherwise cause the sensor to fail.
The difference this coating makes is dramatic. Without it, the sensor only lasted about two months.
With the coating, it worked effectively for over five months—more than twice as long.
Even more exciting, the team found that the polymer coating did more than just protect the sensor.
During the testing period, they discovered that the coating actually helped a chemical reaction occur, making the sensor more sensitive to formaldehyde. This unexpected bonus led them to experiment further.
When the sensor’s performance started to fade, they introduced a bit of humidity—and to their surprise, the sensor bounced back, regaining about 90% of its original sensitivity. In short, the sensor could regenerate itself.
Professor Reeja Jayan, who led the research, explained that the coating is not only protective but also sustainable, as it helps the sensor remain stable and functional over time. Her lab is now working on similar materials to improve the performance and safety of batteries.
Simulations by Jerry Wang, another researcher involved, confirmed that the polymer layer slows the penetration of harmful gases like oxygen and water vapor, giving the sensor added durability.
According to co-author Albert Presto, this innovation could pave the way for low-cost, long-lasting air quality sensors that connect to smart devices and eventually even be built into walls or clothing.
That kind of constant, real-time monitoring could help people make more informed choices about the products they use and the air they breathe—ultimately creating healthier indoor environments for everyone.