Photometallization allows production of the entire circuitry on touchscreens in one step

January 20, 2015, Leibniz-Institut für Neue Materialien gGmbH
Photometallization

When users operate their smartphones, tablets and so on, they do not give a second thought to the complicated electronics that make them work. All that concerns them is that they can happily swipe and tap away. To make the touchscreens work, they are provided on their surface with microscopically small electrical conductor tracks, which detect the position when touched with a finger. At the peripheries of the devices, these microscopic tracks merge into larger conductor tracks. Until now, several production stages have been needed to create them. The researchers at the INM – Leibniz-Institute for New Materials are now presenting a novel process that allows microscopic and macroscopic conductor tracks to be produced in one step.

The researchers from the INM will be presenting their results at the International Nanotechnology Exhibition and Conference nano tech 2015, Tokyo, Japan.

The developers are basing the novel process on photometallization: under exposure to UV light, and acting in conjunction with a photoactive layer, colourless silver compounds turn into electrically conductive silver. The silver compound can be applied in the form of tracks or other structures to plastic films or glass by various methods. Tracks of various sizes, down to the smallest size of a 1000th of a millimetre, can be created in this way. The corresponding conductor tracks are then produced by exposure to UV light.

The foils or glass are first coated with a photoactive layer of metal oxide nanoparticles. "We then apply the colourless, UV-stable silver compound", says Peter William de Oliveira, Head of the Optical Materials Program Division. The exposure of this series of layers has the effect that the silver compound on the photoactive layer decomposes and the silver ions are reduced to metallic, electrically conductive silver. This process is said to have several advantages: it is claimed to be quick, flexible, variable in scale, low in cost and environmentally friendly. And there is no need for any further post-treatment process steps.

This basic principle allows researchers at the INM to very individually apply conductor strips of different sizes to substrates such as glass or plastic. "There are three different options that we can use as required. "Writing" using a UV laser is particularly good for the first customized production and testing of a new conductor strip design, but this method is too time-consuming for mass production", explains physicist de Oliveira.

Photomasks that are only UV-permeable at the desired positions can also be used for structuring. "The production of these masks is quite costly and has a high environmental impact. For a "semi-continuous process" they are particularly suitable for solid substrates such as glass", says the materials expert, but they were not suitable for a potential roll-to-roll process because they are mainly composed of quartz glass and are not flexible.

The researchers are currently focusing their efforts on a third method using so-called transparent stamps. "These stamps mechanically displace the silver complex, and where there is no silver there is also no conductor strip", in de Oliveira's opinion. "So we can form structures measuring just a few micrometers. Since the stamps are made of a flexible polymer, we have here the possibility of arranging them on a roll. Because they are transparent, we are working on incorporating the UV source in the roll, so the first steps would be done for a roll-to-roll process", the Head of the Program Division sums up. This has enabled conductor strip structures of different sizes to be produced on substrates such as polyethylene or polycarbonate film on a large scale.

Explore further: Novel process allows production of the entire circuitry on touchscreens in one step

Related Stories

Anti-microbial coatings with a long-term effect for surfaces

June 10, 2014

Researchers at the INM – Leibniz Institute for New Materials have now produced antimicrobial abrasion-resistant coatings with both silver and copper colloids with a long-term effect that kill germs reliably and at the same ...

Stable electrodes for improving printed electronics

April 19, 2012

Imagine owning a television with the thickness and weight of a sheet of paper. It will be possible, someday, thanks to the growing industry of printed electronics. The process, which allows manufacturers to literally print ...

Copper Nanowires Enable Bendable Displays, Solar Cells

June 1, 2010

(PhysOrg.com) -- A team of Duke University chemists has perfected a simple way to make tiny copper nanowires in quantity. The cheap conductors are small enough to be transparent, making them ideal for thin-film solar cells, ...

Solar modules embedded in glass

June 2, 2014

Organic solar modules have advantages over silicon solar cells. However, one critical problem is their shorter operating life. Researchers are working on a promising solution: they are using flexible glass as a carrier substrate ...

Recommended for you

Under-fire Apple removes 25,000 apps in China

August 20, 2018

Apple said Monday it had removed many gambling-related apps from its Chinese app store as the US giant comes under scrutiny amid trade tensions between Beijing and Washington.

Robots as tools and partners in rehabilitation

August 17, 2018

In future decades, the need for effective strategies for medical rehabilitation will increase significantly, because patients' rate of survival after diseases with severe functional deficits, such as a stroke, will increase. ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

BONK__RS
not rated yet Jan 20, 2015
is the silver solderable? this would make a really good small-geometry PCB printer.
PPihkala
not rated yet Jan 22, 2015
is the silver solderable? this would make a really good small-geometry PCB printer.

If it is solderable on the right surface, then UV-laser based printer could make PCBs cheaply and fast for prototype series.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.