Developed to measure the effectiveness of plasma-based air disinfection, the approach could eventually assess other techniques as well
Study: Using Viral Aerosol Fluorescence for Detection of Virus Infectivity Change Induced by Non-thermal Plasma (DOI: 10.10007/s11090-026-10648-6)
Key takeaways
- Aerosols are major drivers of virus transmission
- The performance of air disinfection techniques is hard to measure, but a new fluorescence-based method speeds up the process.
- The researchers aim to use it to improve their air disinfection technology, which can deactivate up to 99.9% of virus particles with plasma.
The effectiveness of air disinfection devices may now be measured in minutes, rather than hours, with a new technique from University of Michigan Engineering. This is important for researchers developing better antiviral air purifiers, helping to mitigate outbreaks of viral respiratory diseases and prepare for the next pandemic.
The new method harnesses a property known as UV fluorescence, or how molecules absorb UV light, followed shortly thereafter by emission of energy at another wavelength. It turns out viral aerosols shine brighter before disinfection treatment than after. This finding offers the potential to indirectly but rapidly track the performance of air disinfection technologies and more.
"Our findings suggest that it may be possible to detect changes in aerosol infectivity in a rapid, real-time manner without tedious laboratory procedures," said Zhenyu Ma, a U-M postdoctoral research fellow and first author of the study in Plasma Chemistry and Plasma Processing. "As the field of application for this technology becomes clearer, we could use it to better understand the behavior of pathogenic aerosols and their infectivity, thereby providing essential information for public health guidelines."
The speed of the new approach, developed in the lab of Herek Clack, U-M associate professor of civil and environmental engineering, is key. The standard method of evaluating an air disinfection process requires collecting pathogen samples from air before and after treatment. For viruses, it involves exposing host cells to the pathogen sample so that the viruses have something to infect. Then, technicians look for signs of infection through a microscope, a labor-intensive process that yields just a single measurement of air disinfection performance.
In contrast, U-M's approach yields results after several minutes of sampling a small portion of the air stream entering, and then exiting, an air disinfection device or chamber. The sampled air streams flow separately into a device that measures the size of each particle, exposes it to UV light and measures the intensity of its glow. With thousands of these measurements taken over a couple of minutes of sampling, naturally occurring particle-to-particle variations cause the fluorescence intensity measurements to take the shape of a bell curve.
This bell curve shifts to lower intensities as the fraction of viral aerosols inactivated by the disinfection process increases. As a result, researchers can measure the fluorescence intensity of the air sample before and after the disinfection process and compare them to figure out how well disinfection worked.
Once the expected shift in the bell curve is known for a particular pathogen, between treated and untreated viruses, the effectiveness determination takes just a few minutes. For researchers like Clack, who develop disinfection processes, this means faster prototyping and testing at different air flow rates, air temperatures, humidity levels and more.
"Even as the paradigm has shifted regarding the significance of airborne disease transmission, air disinfection technologies that do not rely on filtering air suffer slow development cycles because of how tedious it traditionally has been to prove how well the pathogens have been inactivated," Clack said. "Having an indirect indicator, properly calibrated, for pathogen infectivity could speed up that development process tremendously."
Fluorescence monitoring could also be effective for disinfection tools such as ozone and chlorine, the researchers suggest. But for techniques that disrupt the virus' genome, such as ultraviolet light, fluorescence will not work. The genome is too deep inside the virus to be reached by these fluorescence detection methods, so their fluorescence signatures don't change in the same way.
Clack's group studies interactions between aerosols and strong electric fields. These fields produce nonthermal plasmas, or regions containing charged molecular fragments, which damage viruses and render them harmless. Their group has demonstrated that nonthermal plasmas are capable of reducing the number of infectious viruses in flowing air by 99.9% in lab testing as well as at enclosed livestock operations.
Clack's startup, Taza Aya, has prototyped plasma-based respiratory protective gear, currently being tested in a Michigan turkey processing plant.
Story by Jim Lynch, Michigan Engineering
