PFAS in water
Researchers at Penn State have developed a new sensor architecture that could significantly improve the detection of trace chemicals and biomolecules in liquids, with possible applications in environmental monitoring, healthcare and agriculture.
The advance centres on a redesigned field-effect transistor (FET), a core electronic component used in many sensing devices. FET-based sensors are already known for their small size and sensitivity, but they have often struggled in liquid environments, where signal drift, electrical leakage and long-term instability can undermine performance. That has limited their use in settings where reliable measurements in water or other fluids are essential.
For environmental and biological monitoring, liquid compatibility is critical. Whether the target is a pollutant in water or a biomarker in the body, the sensor has to maintain accuracy over time while exposed to a fluid medium.
According to the Penn State team, conventional FET designs can become unstable when immersed in liquid because their electrical readings gradually shift even when the thing being measured has not changed. This signal drift reduces confidence in results and makes it harder to distinguish genuine chemical changes from device noise.
The Penn State researchers addressed this by redesigning the transistor so that it uses two gates instead of one. In a standard transistor sensor, the gate controls the flow of current through the device, but repeated adjustments during measurement can introduce instability. In the new design, the two gates allow separate control of current flow and sensing response.
This dual-gate arrangement enables the system to keep current constant while a built-in feedback mechanism tracks small chemical changes more precisely. The top gate is highly sensitive to the surrounding environment, while the bottom gate provides a more stable electronic counterbalance. Together, they amplify tiny surface charge changes, making subtle chemical signals much easier to detect.
The device is built around graphene, a two-dimensional material made of a single layer of carbon atoms. Graphene is highly conductive and extremely sensitive to its surroundings, which makes it attractive for sensing applications. However, that same sensitivity can also make it difficult to use reliably in liquids unless the supporting device structure is carefully engineered.
In this case, the researchers combined graphene with ultra-thin metals, an insulating oxide and a silicon wafer base to create a transistor that is both highly responsive and better able to withstand the challenges of liquid-phase sensing.
According to the team, sensors based on the new architecture delivered up to 20 times greater sensitivity than comparable single-gate transistor sensors, while also reducing signal drift by up to 15 times.
That is particularly relevant for environmental monitoring, where instruments often need to detect very low concentrations of harmful substances with a high degree of confidence. The researchers specifically highlighted PFAS as one of the targets the sensors can detect, alongside biological compounds such as dopamine, serotonin and IL-6, a protein associated with inflammation.
For water monitoring professionals, the ability to identify persistent contaminants like PFAS with greater sensitivity and lower drift could be especially valuable, particularly in portable or distributed systems where long-term stability is a major requirement.
Another practical advantage is scalability. The team said it can integrate up to 32 sensors into custom circuit boards, with each sensor measured independently and without electrical interference. By stacking these boards, the system can be expanded while keeping the sensing elements themselves extremely small.
That points towards future multi-analyte platforms capable of monitoring a range of chemical or biological parameters at once. For instrumentation users, that could eventually support more compact and flexible sensing systems for field or near-real-time applications.
The researchers now plan to continue refining the architecture with a view to commercial use. They are currently optimising the platform to detect volatile organic compounds linked to Parkinson’s disease, but they are also exploring whether other two-dimensional materials could further improve performance.
For the environmental monitoring sector, the broader significance is clear. This work suggests that advanced materials such as graphene, when paired with smarter transistor design, may help overcome some of the longstanding limitations of liquid-phase sensing. If the technology can be translated into rugged, field-ready instruments, it could offer a new route to highly sensitive, low-drift monitoring for water quality and other demanding applications.
IET 36.2 Mar/Apr 2026
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