Cell phone screens with no fingerprints in sight

Organic residues removed by photocatalysis

A coating with titanium dioxide makes surfaces resistant to organic deposits from fingerprints, bacteria or fungi. The titanium dioxide acts as a catalyst and is activated by UV light. In a photo-electrochemical process, organic substances are then broken down into their gaseous components. Touch screens for cell phones and tablets can be kept free of fingerprints and smudges. At the moment, however, only if the devices are regularly placed in the blazing sun.

fingerprintFingerprint: curse of smartphone users (Photo: pixelio.de, A. Bachert)

Dirt disappears

The first garden furniture with a titanium dioxide coating is already available in stores. They stay nice and clean even after years because no dirt sticks. "By applying photocatalysts such as titanium dioxide, surfaces made of glass or plastic can be freed from organic contaminants. Photocatalysis, for example, can decompose the organic components of fingerprints. The inorganic components, such as salts, are wiped off with water," explains Michael Vergöhl from Fraunhofer -Institute for Layer and Surface Technology http://www.ist.fraunhofer.de opposite pressetext.

However, a light source is required for the process to work. "Titanium dioxide is activated by UV light. Organic substances are broken down into gaseous residues in a photoelectrochemical process. The activity of titanium dioxide is not high enough for use on mobile phone displays. In direct sunlight, one hour is enough to erase fingerprints, In normal day-to-day work, however, the UV radiation is far less intense, and degradation would take a few weeks. In addition, titanium dioxide is highly reflective and an anti-reflective layer would be difficult to implement, "says Vergöhl.

Other materials

However, these obstacles are not insurmountable. Other materials can also be used as photocatalysts and perhaps activated with less light. "There are some promising candidates - such as zinc oxide - for everyday use. Application is not a problem, as there are various ways of ensuring a permanent coating," says Vergöhl. It has long been known that photocatalysis is a suitable tool for developing self-cleaning surfaces. Due to the problem of smeared smartphones, the technology is now up to date again.

"There have been similar projects in the past for coating car windshields. However, an anti-dirt windshield was more of a 'nice-to-have' than a necessity. Smartphones are bringing a new wind to research because smeared screens are a real nuisance Nevertheless, there is currently a lack of projects in this area, "says Vergöhl.