Detecting PFAS in Water: Breakthrough Sensor for Safety

Key Things to Know:

• Forever chemicals, particularly PFAS, pose significant health risks, including cancer, reproductive issues, and immune system interference, due to their persistence in the environment and the human body.
• MIT researchers have developed a groundbreaking sensor that can detect PFAS in drinking water at concentrations as low as 200 parts per trillion, offering a rapid and accessible testing method.
• The sensor utilises polyaniline, a polymer that changes conductivity in the presence of PFAS, enabling quick detection without the need for specialised laboratory equipment.
• This advancement not only has the potential to enhance public health safety measures but also paves the way for future innovations in environmental monitoring and electronic systems integration.

As researchers continue to observe the negative effects of forever chemicals in humans, the increasing levels of these chemicals in drinking water are raising serious concerns amongst health experts. Recognising the challenges faced with detecting such chemicals, researchers have recently developed a new test strip that can be used to identify key forever chemicals in minutes without the need for a lab. What challenges do forever chemicals present, how does the test work, and how could it be utilised in electronic systems?

What challenges do forever chemicals present?

The term “forever chemical” has continued to gain media attention, and when seeing the effects that such chemicals have on the human body, it’s completely understandable. A forever chemical is one that can last in the environment for extremely long periods of time (hence, forever), and it is only when they are consumed that they cause issues. 

While data is still being gathered on such chemicals, the most common issues identified by researcher so far has been cancer, reproductive issues, and immune system interference. To make matters complex, once such chemicals have entered a living body, they are not easily removed, meaning that once inside, they can cause long-lasting damage.

The Persistent Threat of PFAS in Everyday Products

One example of a forever chemical group is polyfluoroalkyl substances (PFAS), which has been found in numerous products since the 1950s including food packaging and non-stick cookware. Materials that contain these compounds are ok so long as the surface of those products is undamaged (which is why metal utensils must never be used with Teflon pans). However, over time, minute amounts of damage eventually cause small pieces of material to dissolve into food, thereby getting into the food chain and wider environment. 

Banning these products can help to eliminate the generation of new forever chemicals, but existing products, along with the vast amount of materials in landfills, mean that the environment will continue to be impacted by such chemicals for hundreds of years. Thus, contamination of these forever chemicals doesn’t just occur in the products that we use but also in the food and water that we consume.

To help mitigate against forever chemicals, those responsible for supplying drinking water can do frequent tests. While these tests do provide accurate results, they require the use of labs which are expensive to use. Furthermore, as these tests are generally inaccessible to homeowners, it can be difficult to get full transparency from water companies. Even if such tests are available to the public, their high price tag and long process time mean that real-time results are not possible.

Researchers create new sensor for real-time forever chemical detection 

Recognising the challenges faced with detecting forever chemicals, researchers from MIT have demonstrated a new testing kit that is able to provide results in minutes instead of days. The test, which operates in a similar way to COVID lateral flow tests, utilises a strip of paper with a special activator that changes in the presence of PFAS chemicals. According to the researchers, the sensor is able to react to the presence of PFAS in concentrations as low as 200 parts per trillion, allowing for rapid detection of these chemicals.  

The sensor's innovative approach, leveraging polyaniline, a unique polymer that transitions from a semiconductor to a conductor upon exposure to PFAS, marks a significant advancement in the field of environmental monitoring. This technology, as detailed in MIT's recent study, not only offers a quick and cost-effective method for detecting harmful substances in water but also sets a new standard for real-time environmental testing. The ability to detect PFAS at such low concentrations is crucial for protecting public health and preventing the long-term environmental impact of these persistent chemicals.

Understanding the Mechanism Behind the PFAS Detection Sensor

To make the test strip work, the researchers turned to a unique polymer called polyaniline, which has semiconductive properties. Under normal conditions, the resistance of this polymer remains poor (enough for a current to flow), but when exposed to PFAS molecules, protons absorbed by the polymer turn it from a semiconductor into a conductor, thereby significantly reducing its resistance.

 A small pair of electrodes can then be used to measure the resistance of the strip, thus allowing for the fast and reliable detection of PFAS. However, as the sensor relies on proton doners, it can only work with acidic PFAS solutions, meaning that there are forever chemicals which it cannot detect.

Further research and development are underway to enhance the sensor's capabilities, aiming to broaden its detection range to include non-acidic PFAS compounds. The team at MIT is focused on refining the sensor's sensitivity and user-friendliness, envisioning a future where households can easily test their water for a wide range of contaminants. The progress made by the researchers, as documented in their publication, underscores the potential of this technology to become an integral part of environmental safety measures worldwide.

How could such sensors be utilised in future electronic systems?

While the sensor developed by the researchers requires further refinement before it can be used by the public (as it doesn’t have the sensitivity required for water testing), it clearly demonstrates the power of self-testing and how electronic testing methods will likely become more important in daily life.

Considering that the sensor developed by the researchers had smartphones in mind, it is possible that future smartphones may incorporate a sensor port, or allow sensors to connect to the USB port so that different sensors can be connected. Such a setup would essentially allow users to turn their smartphones into personal “tricorders” (see Star Trek) that provide real-time environmental readings, check foods for allergens, and even diagnose diseases.

For example, tourists travelling to remote areas could utilise such a device to rapidly identify if food or water is safe to eat, if parasites are lurking in a river, or identify potentially dangerous atmospheres. 

Such sensors could also be massively beneficial for officials doing portable testing. Instead of having to take samples from an environment and bring them back to a lab, tests can be conducted in the field, which not only helps to speed up results but allows for immediate action should a test fail.

The sensor produced by the researchers needs further improvement, but it clearly demonstrates the power of electronic sensors and environmental monitoring.