Cold plasma: Contactless disinfection of surfaces

One of the most time-consuming tasks in hospitals is the manual cleaning and disinfection of high touch points and surfaces such as door handles, buttons, and switches. These are areas where microorganisms are spread by direct skin contact. The "MobDi – Mobile Disinfection" research project is developing a robot that automatically cleans and disinfects these areas. It will use cold plasma as one of its tools.

In this MEDICA-tradefair.com interview, Dr. Kristina Lachmann explains how atmospheric pressure plasmas are generated and used for disinfection purposes and reveals how a robot can use the technology to facilitate cleaning and disinfection – not only in hospitals but in all high traffic areas.

Dr. Lachmann, what is atmospheric pressure plasma?

Dr. Kristina Lachmann: Plasma is called the fourth state of matter, right along with solid, liquid and gas. Plasmas naturally occur in nature. We encounter hot plasmas in lightning flashes and cold plasmas in the northern lights at the Arctic Circle. Atmospheric pressure plasmas are cold plasmas. They are created by applying very high voltage to a gas under atmospheric pressure. This prompts the gas atoms to split into ions, electrons, and radicals, producing reactive species that interact with surfaces and act as a disinfectant against microorganisms.

How does plasma affect pathogens?

Lachmann: Radicals break the bonds of organic molecules. Simultaneously, plasma glows because the excited electrons fall back down to their lower energy states and give off energy in the process. This creates UV radiation, which damages cells or destroys their DNA depending on the type of gas.

Your Institute developed a plasma system for the cleaning and disinfection of surfaces. What is its intended use?

Lachmann: We designed it as an interchangeable tool that can be managed by a mobile disinfection robot – in conjunction with other cleaning methods. The device could disinfect intricate components such as door handles or contact areas with a simpler design including light switches or elevator buttons and surfaces. The plasma can also clean and disinfect moisture-sensitive and porous textiles using a virtually dry approach. The objective is to have the robot use the different tools and manage the process autonomously, thus turning it into an integral part of standard cleaning operations.

Having said that, the use of plasma technology for disinfection should always be the last step in the cleaning process. It is merely an added tool since all heavy-duty organic matter and soiling must first be removed before its eventual application. However, surfaces where there is no visible contamination can be disinfected this way.

Is plasma disinfection designed as a replacement or as a complement to the manual wipe disinfection technique?

Lachmann: It still takes conclusive research to determine whether or to what extent this method can actually substitute wipe disinfection. If it ends up being just as efficient, the technique will eliminate the use of a rag or cloth, which can potentially spread germs and pathogens. The benefit of the plasma technology is that it delivers a contactless approach to direct surface disinfection.

That being said, the technology cannot replace the cleaning process for heavily contaminated areas or large areas such as floors, for example. It is designed to target small, special sections that can be accessed using the robot and where it makes sense to clean at frequent intervals. Using a robot in combination with other tools and equipment can be a great way to ease and reduce staff workload and stress and protect employees in charge of cleaning and disinfecting contaminated areas.

Have you tested your system yet?

Lachmann: We have teamed up with the Municipal Hospital Braunschweig and the Institute of Construction Design, Industrial and Health Care Building at the Technical University of Braunschweig to set up a patient room as a system demonstrator. Since we focus on infection prevention, this setting delivers an excellent test environment to assess and review our system, which is something that was not an option as such until now.

We have not yet been able to conduct any large-scale studies because the Municipal Hospital had faced relentless challenges and operated at full capacity due to the COVID-19 pandemic. Once the patient room will be set up come this summer, our goal is to study how the plasma system in conjunction with the cleaning robot stack up in comparison or if we see a positive impact when it is combined with current cleaning options and disinfection procedures. We primarily focus on different materials and surfaces in this setting.