Revolutionary Polymer Coating Enhances MXene Sensors for Indoor Air Quality

In a significant advancement for indoor air quality monitoring, researchers at Carnegie Mellon University have developed a polymer coating that extends the lifespan of MXene-based formaldehyde sensors by 200%, while also enabling them to regenerate performance when low on efficacy. This innovation, detailed in a study published in *Science Advances* on July 11, 2025, addresses critical health concerns associated with formaldehyde exposure found in household items like cleaning products and cosmetics.

Formaldehyde, a colorless and odorless chemical, is widely recognized as a health risk when present in air concentrations exceeding 0.1 parts per million. With the development of this sensor, which utilizes MXene, a promising class of two-dimensional materials known for their exceptional electrical properties, the researchers aim to enhance indoor air quality monitoring, making it more accessible and effective.

The research team, led by Reeja Jayan, a Mechanical Engineering professor at Carnegie Mellon University, employed a technique known as initiated Chemical Vapor Deposition to create a polymer nano-coating that encapsulates the MXene sensor. Jayan explained that this process involves pumping vaporized precursor materials into a vacuum chamber, where they polymerize and form a protective layer on the sensor. Without this coating, the sensor's lifespan was limited to just over two months, whereas with the polymer, it can now function for over five months.

Shwetha Sunil Kumar, the first author of the research paper and a Ph.D. candidate, observed that the polymer layer not only improved the sensor's longevity but also enhanced its sensitivity to lower formaldehyde levels due to a chemical reaction facilitated by the coating. The research team discovered that by introducing humidity at the end of the sensor's life, it could regain up to 90% of its original sensing ability.

This finding has broad implications for future applications. Albert Presto, director of the Center for Atmospheric Particle Studies at CMU and co-author of the study, believes that such sensors could eventually be integrated into everyday objects, such as walls or clothing, for continuous indoor air quality monitoring. Presto emphasized the need for increased awareness regarding indoor pollutants to empower individuals in making informed choices to improve their living environments.

Simulations conducted by Jerry Wang, an Assistant Professor of Civil and Environmental Engineering, further validated the effectiveness of the polymer coating, demonstrating its ability to slow the permeation of oxygen and moisture. This capability not only enhances sensor stability but also contributes to sustainability efforts in air quality monitoring technologies.

The research represents a pivotal step in the field of nanotechnology and environmental safety, highlighting how materials science can influence public health. As the world faces increasing challenges related to indoor air quality, innovations like this polymer-coated MXene sensor could play a critical role in safeguarding health and enhancing the quality of life.

Going forward, Jayan is exploring the application of similar polymer technologies to extend the lifespan and safety of batteries, indicating a promising future for material science innovations in various fields. The researchers' work not only demonstrates the potential of MXene in creating advanced sensors but also points to a broader trend of using nanotechnology to address pressing health and environmental issues.