Chemical-free disinfection through plasma technology

Growth of Escherichia coli bacteria after treatment with PBF (left) and without treatment (right). Viable bacteria grow as white colonies on the nutrient agar. © Fraunhofer FEP

The Fraunhofer FEP is investigating plasma-activated water as a chemical-free alternative to conventional disinfectants. The innovative solution remains active for over 300 days and is suitable for pharmaceuticals, the food industry, and agriculture.

Scientists at Fraunhofer FEP are researching a technology for producing plasma-treated liquids (PBL), which can be used as an environmentally friendly alternative to conventional chemical disinfectants. A recent study examines their suitability as surface disinfectants. The research results show a shelf life of over 10 months and good antimicrobial efficacy against E. coli.

The technology uses atmospheric pressure plasma sources to treat liquids, creating reactive oxygen and nitrogen species. "The plasma-activated water can be pre-treated and then transported to the deployment site without the need for plasma sources or other treatment devices on-site," explains Linda Steinhäußer, lead author of the Fraunhofer FEP study.

Comparison of Different Plasma Processes

Compared to dielectric barrier discharge, arc discharge showed up to four times higher antimicrobial effectiveness. Tests with the model organism E. coli demonstrated a reduction of up to 4 log levels, depending on the material, exposure time, and PBF volume used.

Versatile Applications

The plasma-treated liquids are suitable for various industries:

– Pharmaceuticals and cleanrooms: chemical-free disinfection under sterile conditions
– Food industry: Cleaning-in-Place processes, e.g., for milk tanks and similar systems
– Agriculture: potential use as disinfectants and fertilizers through nitrogen species

Material-Dependent Effectiveness Demonstrated

The study documents for the first time a material-dependent antimicrobial efficacy. Polymer surfaces (ABS, PVC) and stainless steel surfaces were compared. These findings are relevant for industrial applications and enable targeted optimization for different surface materials and use scenarios.

Storage Stability Investigated

"The physicochemical parameters indicate a shelf life of over 300 days for longer plasma treatment times," says Steinhäußer. While the long-term stability of the physicochemical parameters has been demonstrated, the correlation with disinfectant efficacy is still under investigation.

The Fraunhofer team is already collaborating with partners from the pharmaceutical industry and is open to further cooperation.

About the Research

The study was published in the journal "Surface & Coatings Technology" and was conducted in collaboration between the Fraunhofer Institute for Electron Beam and Plasma Technology FEP in Dresden and the Fraunhofer Institute for Surface and Thin Film Analysis IST in Braunschweig.