Surfaces disinfected with light protect against bacteria and viruses
The aim of recent research work carried out by Fraunhofer IFAM in cooperation with the University of Szeged in Hungary was to develop a flexible coating solution for component surfaces, which enables reliable and permanent decontamination without chemical treatment and which can also be implemented cost-effectively on a large scale.
Initial development work by Fraunhofer IFAM on silver-doped titanium dioxide photocatalysts intercalated in layered silicate and dispersed in a polyurethane coating – PU in short – has shown that application of the functional coating on surfaces enables successful decontamination of bacteria as well as viruses – even in the visible light range at wavelengths > 430 nm. One decisive cause for this fast and effective mechanism are the layered silicates themselves, which form active centers of a few nanometers in size on the surface, thus enabling direct contact between the microorganisms and the photoactive substances.
Very good antibacterial and antiviral degradation results
In a further approach, silver has been substituted by copper and was produced using a scalable manufacturing approach. For the production of the copper-doped photocatalyst, a process was developed at Fraunhofer IFAM which also allows the production of larger quantities already on a laboratory scale. The catalyst could then be dispersed in a PU coating system and also compounded in thermoplastic polymers. The thermoplastic polymers could be easily extruded into filaments, which could then be printed into complex components using the 3D printing process Fused Filament Fabrication (FFF). The influence of different filling contents of the photocatalyst complex on their antimicrobial effectiveness was investigated.
The test series showed that fill levels of the photocatalyst complex of around 35 percent by weight in the PU coating and 50 percent by weight in the polymer achieved very good antibacterial and antiviral degradation results. Within two hours, a degradation rate of more than 80 percent could be achieved compared to the control components, both under UV light and with a light source similar to sunlight. As a result, silver can be fully replaced by copper in the various applications. A patent application has also been filed for this process.
Further information can be found on the Fraunhofer IFAM website.