Killing germs with new copper-based materials

Researching new materials

Left exposed on smooth, polished copper, bacteria will die before long. This is extremely useful in attempts to control dangerous infections. But pure copper becomes tarnished with brown and black copper oxide, which is not forcibly less beneficial for killing bacteria, but suggests an "unclean" optical impression. Saarbrücken-based Professor Dr.-Ing. Frank Mücklich, who heads up the Steinbeis Research Center Material Engineering Center Saarland is working with material scientists in an attempt to develop copper materials that help overcome this problem. Focusing on special surfaces and copper alloys, the team aims to create materials that can actively kill bacteria over an extended period. The project has Euro 300,000 of backing from the German Research Foundation.

“More and more hospitals are reporting cases involving multi-resistant germs, and even the strictest hygiene measures can’t deal with them,” reports Prof. Dr. Mücklich, Professor of Functional Materials at Saarland University. This could be a case for copper-based materials, for example as a coating on light switches or door handles. “But much more detailed research is needed,” he continues, “to see how exactly copper makes bacteria harmless and how to maintain its efficacy over time.” The material researcher is currently working with Marc Solioz, an international copper expert and pharmacologist at the University of Berne as well as microbiologists at Saarland University. The team will examine the efficacy of new types of copper materials in killing dangerous germs.

To change material surfaces, the researchers working with Prof. Dr. Mücklich are looking at a type of technology known as laser interference. This involves directing several laser beams at a material, bundled together, to create extremely precise patterns over an area of about one square centimeter. The effects are no bigger than several micro- or nanometers. “The light from the laser inflicts high temperatures on an extremely small surface area. We can practically melt all metals to onetenth of the width of a hair,” explains Prof. Dr. Mücklich.

The intense heat of the laser beam can even change the topography of a surface so that it has tiny peaks or valleys. “These are about the size of an individual bacterium. So in theory it must be possible to form a kind of burrow, which the germs will fall into, like a trap, and then they’re encircled by copper,” suggests Prof. Dr. Mücklich. The scientists are hoping that the laser treatment will also create material surfaces, which will not oxidize easily. “The antibacterial properties of materials should remain intact for as long as possible and not be compromised by cleaning materials or disinfectants,” states Prof. Dr. Mücklich, describing the best-case scenario. To achieve this, the laser beams will also be used to change the inner structure of the material in a wafer-thin layer. “As well as experimenting with copper alloys, we’ll also be using minute silver particles. Silver is known for its ability to kill off bacteria,” adds Prof. Dr. Mücklich.

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