MIT chemists have developed an innovative sensor capable of detecting minuscule levels of perfluoroalkyl and polyfluoroalkyl substances (PFAS), often referred to as “forever chemicals.” These substances are commonly present in everyday items such as food packaging and nonstick cookware.
Known for their persistence in the environment, these chemicals are linked to serious health concerns, including cancer, reproductive issues, and disturbances in the immune and endocrine systems.
With the new sensor technology, researchers successfully identified PFAS concentrations as low as 200 parts per trillion in water samples. This groundbreaking device could empower consumers to test their drinking water and serve as a crucial tool for industries dependent on PFAS, such as semiconductor manufacturing and firefighting equipment fabrication.
“There is an urgent need for these sensing technologies. We are facing a long-term challenge with these chemicals, so it’s vital that we can detect and eliminate them,” explained Timothy Swager, the John D. MacArthur Professor of Chemistry at MIT and lead author of the study published in the Proceedings of the National Academy of Sciences.
The research team also includes former MIT postdoc and lead author Sohyun Park, along with graduate student Collette Gordon.
Understanding PFAS Detection
PFAS chemicals are utilized in a wide array of consumer products, from nonstick cookware to water-resistant clothing, stain-proof fabrics, grease-resistant pizza boxes, cosmetics, and firefighting foams. These fluorinated compounds, in use since the 1950s, can enter the environment through factories, sewage treatment plants, and landfills, contaminating drinking water sources across all 50 states.
In 2023, the Environmental Protection Agency established health advisory levels for two of the most dangerous PFAS, perfluorooctanoic acid (PFOA) and perfluorooctyl sulfonate (PFOS), setting limits at 0.004 and 0.02 parts per trillion, respectively.
Currently, the only way for consumers to verify the presence of PFAS in their drinking water is to send samples to labs for mass spectrometry testing, a process that can take weeks and costs hundreds of dollars.
To develop a more accessible and cost-effective PFAS testing method, the MIT team utilized lateral flow technology — similar to the technology behind rapid Covid-19 tests and pregnancy tests. Instead of using a test strip coated with antibodies, the sensor incorporates a special polymer called polyaniline, which can toggle between semiconductive and conductive states in the presence of protons.
The researchers applied this polymer onto nitrocellulose paper strips and coated them with a surfactant that effectively extracts PFAS from a water sample. As protons from the PFAS enter the polyaniline, it transforms into a conductor, allowing for a measurable change in electrical resistance. This shift can be accurately detected via electrodes and transmitted to an external device, like a smartphone, providing a precise quantification of PFAS levels.
This sensor is particularly effective for acidic PFAS, including the highly toxic PFOA and perfluorobutanoic acid (PFBA).
Designing a User-Friendly System
The current prototype can detect PFBA at concentrations as low as 200 parts per trillion and PFOA at about 400 parts per trillion. Although these levels do not meet existing EPA standards, the sensor requires only a minuscule volume of water for effective testing. The researchers are working on a larger system capable of filtering about a liter of water through a polyaniline membrane, which they anticipate will significantly increase sensitivity, potentially exceeding EPA thresholds.
“We envision a user-friendly household device,” says Swager. “Imagine inserting a liter of water, passing it through the membrane, and obtaining a measurement of the resistance change.”
This novel testing method could offer an affordable and rapid alternative to current PFAS detection techniques. If hazardous levels of PFAS are identified in drinking water, commercially available filters can mitigate those dangers. The new sensor could also aid factories in monitoring the safety of water used in their processes before releasing it into the environment.
The study received funding from an MIT School of Science Fellowship awarded to Gordon, a Bose Research Grant, and a Fulbright Fellowship for Park.
Photo credit & article inspired by: Massachusetts Institute of Technology
