New technique could revolutionise disinfection of ambulances and hospitals

A novel microwave sterilisation method that could revolutionise the way ambulances and hospitals are disinfected has been created in research involving the University of Strathclyde.

At present, sterilisation is done manually with conventional techniques that use chemicals. This can take around 30 to 40 minutes to disinfect a single ambulance. During this time, the ambulance is out of action, putting increasing pressure on emergency services during busy times.

The possibility of the new technique could drastically reduce the time it takes to get an ambulance safely back on the road to save lives.

In recent years, several other techniques have been proposed for disinfecting and sterilising surfaces, ranging from hydrogen peroxide aerosols to UV irradiation and infrared radiation. However, these techniques have been shown to degrade surfaces over time, or to be harmful to humans if they are in close proximity. This has, so far, limited their long-term application.

In contrast, the new method works using electromagnetic waves, antennas, sensor beacons, and a liquid layer to heat-up and sterilise surfaces rapidly. Its automation means a person can easily operate the system from a safe distance, rather than touching contaminated surfaces directly during cleaning.

The research was led at the University of Edinburgh and also involved Heriot-Watt University. It has been published in the IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology.

Strathclyde researchers played a role in demonstrating whether microwave beams were effectively hitting the surfaces and could heat them at the right temperature.

Professor Nico Bruns, a polymer specialist in Strathclyde’s Department of Pure and Applied Chemistry, was a partner in the study. He said: “My group used hen egg white proteins that are known to denature at 60 degrees centigrade.

“By looking at the solution turning white, we were able to show that the right temperature was reached to enable virus deactivation. This would be extremely helpful for an operator of the proposed system.”

The study used microwave beams emanating from antennae, like those found in mobile smart phones and domestic Wi-Fi systems. The antennae allow the microwave radiation to be directed and focused on locations where it is most needed.

A microwave powered, open-ended oven was shown to enable the deactivation of live coronavirus (strain 229E) at a relatively low temperature of 60 degrees centigrade in 30 seconds.

The collaborative team funded the initial research themselves, using existing lab equipment and their goodwill. They are now seeking funding to manufacture a device that can be installed in ambulances as a proof-of-concept demonstrator.