John Foster, Professor of Nuclear Engineering and Radiological Sciences and Aerospace Engineering at the University of Michigan, has led a research team investigating how cold plasma can be used to destroy PFAS and other persistent contaminants in water. The team, including doctoral graduate Zimu Yang, has focused on understanding the intricate self-organized patterns that form when plasma interacts with water, revealing a potential method to increase surface contact and improve treatment efficiency.
Yang, Z., Wang, Z., & Foster, J. (2025). Surface deformation coupled with self-organized pattern on a liquid anode of 1 atm DC glow discharge. Plasma Sources Science and Technology, 34(9), 095013. https://doi.org/10.1088/1361-6595/ae0764
PFAS, or per- and polyfluoroalkyl substances, are synthetic chemicals used in fire-fighting foams, non-stick cookware, and other applications. Their strong carbon-fluorine bonds make them resistant to conventional water treatment methods, causing them to persist in the environment and accumulate in human and animal tissues. Exposure has been linked to cancer, endocrine disruption, and other health risks.
John Foster, Professor of Nuclear Engineering and Radiological Sciences and Aerospace Engineering at the University of Michigan stated,
“These processes are governed by non-equilibrium thermodynamics. Here energy and reactive species are deposited by the plasma locally in an open system such that deposited species concentration never approaches thermodynamic equilibrium as reactants cannot build up. Without reactant depletion, these open systems are susceptible to self-organization. These pattern footprints are larger and thus can be used to increase plasma contact area.”
Recent studies have shown that plasma, an activated gas containing energetic electrons, ions, and excited molecules, can break down these stable compounds. The University of Michigan team has focused on nonthermal, or cold, plasma, produced with fast high-voltage pulses. These plasmas can deliver sufficient energy to cleave carbon-fluorine bonds without significantly heating the water, making the method suitable even for sensitive biological applications.
When the plasma comes into contact with water under specific conditions, it self-organizes into distinct patterns resembling stars, gears, or wagon wheels. These patterns expand outward, increasing the contact area between plasma and water. High-speed imaging revealed that the plasma exerts an electrical force on the water, deforming the surface and generating waves that mirror the plasma patterns above.
The researchers found that the characteristics of these surface waves depend on the plasma’s gas flow, heating rate, and the water’s electrical properties. By adjusting these variables, it may be possible to control the size and shape of the plasma patterns, allowing larger volumes of water to be treated efficiently.
Plasma-water interactions occur on timescales of about ten microseconds. To observe these rapid events, the team developed a specialized high-speed camera setup. A plasma jet was positioned just millimeters above the water surface, and a speckled laser illuminated the water at an angle. Synchronizing the camera with the plasma pulses allowed the researchers to capture the formation of patterns and the resulting surface deformation.
The experiments confirmed that the plasma patterns directly drive the water waves. By fine-tuning plasma parameters and the water’s electrical properties, the team could produce different pattern geometries and corresponding surface deformations.
The electrical forces, excited species, ions, solvated electrons, and UV light produced by the cold plasma can break the strong carbon-fluorine bonds in PFAS and fragment the carbon chains into smaller, harmless molecules. This approach offers a route to destroy contaminants that resist conventional treatment.
Foster notes that while laboratory demonstrations show near-complete removal of contaminants, plasma-based methods remain energy-intensive. Scaling the process to industrial levels will require optimization of energy usage and treatment design. Nevertheless, controlling self-organized plasma patterns offers a pathway to increasing treatment efficiency and surface area interaction, which is critical for larger-scale water purification applications.
This research provides a foundation for further studies on plasma-water interactions, with potential applications beyond PFAS removal. By understanding and controlling self-organized plasma patterns, engineers could develop more efficient methods for decontaminating water, treating microbial contaminants, or even integrating plasma technologies into industrial water treatment facilities. The study demonstrates how insights from plasma physics can be translated into practical environmental engineering solutions.
The University of Michigan team, led by John Foster with contributions from Zimu Yang, has shown that self-organized plasma patterns can significantly enhance the interaction between plasma and water. These findings provide a new approach to treating persistent contaminants like PFAS, highlighting a promising avenue for research in advanced water treatment technologies.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
