Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cleaning with sunlight

03.07.2012
The sun breaks through the clouds – and surfaces start cleaning themselves! It may sound like magic, but in fact it’s all thanks to the addition of titanium dioxide molecules. Activated by UV light, they trigger a reaction which destroys bacteria, algae and fungi, keeping items such as the armrests of garden chairs nice and clean.

Summer is just around the corner and it’s time to dust off the garden tables and chairs. But garden furniture that has been left in the shade too long is often covered with a slimy film of algae, moss, bacteria and fungi which is difficult or even impossible to remove.


The surface coated with titanium
dioxide molecules (bottom) looks very
different from the non-coated sample
(top). (© Fraunhofer IGB)

Scientists are now hoping that they can solve this problem by incorporating titanium dioxide molecules in the plastic used to make the garden chair and adding a little bit of sunlight. When these titanium dioxide molecules are ‘activated’ by the UV light in the sun’s rays, they act as a kind of catalyst, triggering an electrochemical reaction which produces free radicals. These and other active molecules strike a fatal blow to bacteria, fungi and similar organisms, first destroying the cell walls and then penetrating the cytoplasm – the substance that fills the cell – and damaging the bacteria’s DNA. As a result, the organic substances are destroyed instead of remaining stuck to the surface.

But just how well do these photocatalytic coatings work? What organic elements do they destroy, and what are they powerless against? These two questions have been the subject of investigation by researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart. “For example, we ran some outdoor tests on garden chair armrests with photocatalytic coatings and compared them to ones made from conventional plastic,” says Dr. Iris Trick, group manager at the IGB. Dr. Trick and her team sprayed the coated and uncoated armrests with a mixture of various bacteria, mosses, algae and fungi and then left them exposed to the weather for two years.

At the end of the test, it was almost impossible to remove the layer of dirt from the normal armrests – yet the armrests made from photocatalytic plastics were still almost completely clean and white, even after spending two years outside. The researchers also tested the effectiveness of their special coatings on armrests and a range of other surfaces in the lab. To do this, they applied up to 30 different kinds of fungal, bacterial and algal cultures to coated and uncoated surfaces and compared how the cultures evolved. In addition, they analyzed the degradation products generated on the self-cleaning surfaces by the electrochemical reaction.

Self-cleaning walls and displays
The opportunities offered by titanium dioxide molecules extend far beyond armrests. For example, researchers from the Fraunhofer Institute for Manufacturing Engineering and Automation IPA in Stuttgart are working on paints for building façades which contain titanium dioxide particles. If the wall gets dirty, the photocatalysis degrades the organic contaminants and the paint stays reasonably clean. The scientists have even developed a self-cleaning coating for glass surfaces: “If you apply a thin coating of titanium dioxide to a glass surface such as a smartphone screen, the skin oils and fingerprints gradually disappear from the display by themselves,” says Dr. Michael Vergöhl, head of department at the Fraunhofer Institute for Surface Engineering and Thin Films IST in Braunschweig and head of the Fraunhofer Photocatalysis Alliance. All that is needed is one hour of sunlight – unlike previous photocatalytic surfaces, which would have required the smartphone to be left in the sun for three days.

The next step is to develop new materials that can also be activated by artificial light. The Fraunhofer Photocatalysis Alliance is a group of ten Fraunhofer institutes which have decided to combine their expertise in this field. It covers the full spectrum of photocatalytic surface development and offers considerable know-how from a single source.

Dr. Michael Vergöhl | Fraunhofer-Institute
Further information:
http://www.fraunhofer.de/en/press/research-news/2012/july/cleaning-with-sunlight.html

More articles from Materials Sciences:

nachricht New design improves performance of flexible wearable electronics
23.06.2017 | North Carolina State University

nachricht Plant inspiration could lead to flexible electronics
22.06.2017 | American Chemical Society

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Supersensitive through quantum entanglement

28.06.2017 | Physics and Astronomy

X-ray photoelectron spectroscopy under real ambient pressure conditions

28.06.2017 | Physics and Astronomy

Mice provide insight into genetics of autism spectrum disorders

28.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>