Junhong Chen, the University of Chicago’s Crown Family Professor at the new Pritzker School of Molecular Engineering, directs an energetic research team. Through that work, they’ve developed a novel sensor that can identify toxic PFAS compounds in drinking water in less than 10 minutes. This innovative technology is so sensitive, it can measure PFAS concentrations down to 250 parts per quadrillion (ppq). That’s similar to looking for just one grain of sand in a whole Olympic-sized swimming pool!
The need for better PFAS detection comes from growing public health alarm associated with these chemicals. A growing body of evidence has linked PFAS exposure to serious health impacts, including multiple cancers, thyroid disease and reproductive harms, and immune system effects. The U.S. Environmental Protection Agency (EPA) has recently proposed aggressive regulations. Specifically, they plan to restrict use of two of the most toxic PFAS compounds—perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS)—to a mere 4 parts per trillion.
The Challenge of PFAS Detection
Detection and elimination of PFAS compounds pose significant technological challenges, as well dangers to our public health and the environment. Andrew Ferguson, a Professor of Molecular Engineering at UChicago PME, underscores this worry.
“PFAS detection and elimination is a pressing environmental and public health challenge.” – Andrew Ferguson
Current methods for detecting PFAST are costly and take weeks to return results. They depend on liquid chromatography/tandem mass spectrometry, which is costly, needs highly specialized equipment and expertise, and takes weeks to return results. This was no small feat, as Chen and his team faced the daunting challenge of creating faster and ultimately cheaper testing processes. What they needed to accomplish PFAS drinking water detection at scale.
Manufacturers have a hard time creating cost-effective tests. PFAS chemicals tend to be present in water at much lower concentrations than more prevalent contaminants, making them difficult to detect. There are, as the EPA acknowledges, thousands of different PFAS compounds. Each one has minor differences in their chemical structure that can dramatically change their health effects and regulations.
Innovative Use of Machine Learning
Chen’s group was very aggressive in trying to overcome these hurdles. They used machine learning to develop novel probes that could selectively attach PFAS to probe compounds for specific PFAS. Moving toward an enrichment-based method through this approach, they were able to increase selectivity and sensitivity, while decreasing costs. These sensors are made from silicon chips. When one of those PFAS molecules hooks up to them, it throws off the electrical conductivity over the chip’s surface.
“Computer simulations and machine learning have proven to be an incredibly powerful tool to understand how these molecules bind to molecular sensors and can guide experimental efforts to engineer more sensitive and selective molecular probes.” – Andrew Ferguson
Seth Darling, a member of Chen’s research team, touted the need to identify unique molecular signatures PFAS.
“Even though they are typically present at minuscule concentrations, PFAS do have certain molecular characteristics that differentiate them from other things dissolved in water, and our probes are designed to recognize those features.” – Seth Darling
In 2021, the team was awarded a Discovery Challenge Award from the UChicago Center for Data and Computing (CDAC). This support enabled them to start using artificial intelligence in their engineering and scientific design process on PFAS probes, which greatly expanded their detection capabilities.
Future Applications and Next Steps
Chen hopes to broaden the use of their sensor technology to other toxic substances.
“Our next step is to predict and synthesize new probes for other, different PFAS chemicals and show how this can be scaled up.” – Junhong Chen
This forward-thinking approach could potentially open doors for monitoring a wide range of contaminants in various environments—from chemicals in drinking water to antibiotics and viruses in wastewater.
Chen recognized the difficulty of enforcing current regulatory limits, citing the complicated nature of detecting PFAS.
“The problem with enforcing these limits is that it’s very challenging and time-consuming to detect PFAS.” – Junhong Chen
Right now, testing individual water samples for PFAS is complicated and would require equipment that should not be in a household.
“You currently can’t just take a sample of water and test it at home.” – Junhong Chen
