Thursday, May 10, 2007

Searching for an invisible solution

Searching for an invisible solution


See-through electronics may sound like science fiction, but developers are already working on them, writes Michael Pollitt.

Advertisement

AdvertisementATROPE in science fiction films is the person standing in front of a transparent screen, manipulating the images there: think Tom Cruise in Minority Report or Ben Affleck in Paycheck.

It's the multi-touch screen, but with a screen that has disappeared.

Transparent screens don't exist - yet.

But Tobin Marks, a professor and synthetic chemist at Northwestern University in Illinois, is trying to turn this science fiction into fact. "I like to make unusual things and process unusual things in unusual ways," he says. "You can imagine a variety of applications for new electronics that haven't been possible previously - displays of text or images that would seem to be floating in space."

We're not talking about holograms here, but see-through colour screens fixed to transparent backing materials such as glass or plastic. For example, Marks imagines a vehicle windscreen that could display a route map, military goggles to give soldiers information, or even a shop window that doubles as a billboard - switch it off and the billboard becomes a window again.

By shunning silicon, Marks has made a new type of thin-film transistor from inorganic and organic materials. Thin-film transistors are commonly found in LCD TVs and computer monitors.

Marks's research group has combined films of an inorganic semiconductor - indium oxide - with a multilayer of self-assembling organic molecules for insulating properties.

The result is a transparent, high-performance thin-film transistor that can be assembled inexpensively on glass and flexible plastics while outperforming silicon transistors.

But all this is only halfway to transparent monitors. In your laptop screen, opaque thin-film transistors drive pixels - liquid crystals - that act as tiny shutters to a light source behind them. Put the invisible electronics behind the pixels and the result is remarkable.

Marks's idea is to combine transparent transistors with existing light display technologies, such as organic light-emitting diodes, liquid crystal or electroluminescent displays.

"Examples could include visors for motorcyclists, assembly-line workers, soldiers and athletes. More exotic would be displays as in the film Minority Report which seem to be floating in air," Marks says.

Dr John McCardle of Loughborough University in Leicestershire, Britain, a lecturer in electronic product design, said transparent electronics were an exciting proposition at first glance.

"There's the obvious integration into transparent products such as windscreens, spectacle lenses and improved computer displays. We even have the possibility of enhancing solar panels where windows could double up as power generators."

McCardle says thin-film components use less energy to manufacture.

But also he likes the idea of hiding the "ugly technology" of components, wires and printed circuit boards.

Although his ideas for invisible electronics go beyond those envisaged by Marks, McCardle suggests some rather more sinister angles not seen in films.

"There is the inevitable interest from the military sector and its use in covert surveillance is assured," he says.

"Where do we stand when there is the potential to be surrounded by invisible cameras hidden in windows and mirrors?"

Dr Henning Sirringhaus of Cambridge University, co-founder of Plastic Logic, is developing a flexible plastic display for portable electronic readers.

Sirringhaus appreciates the new applications for invisible display electronics but has other ideas to do with the aperture ratio: the proportion of thin-film transistor to each pixel being driven. In a typical LCD screen, the light source is behind the pixels which change shape to allow light through.

If you looked at a single pixel through a microscope, you'd see a thin-film transistor blocking one corner. The trick is to make it as small as possible so that it lets through the most light.

"On each pixel of the display, you've got one transistor. That transistor is used to turn on and off that pixel. With transparent electronics, in principle, you could use the whole pixel," says Sirringhaus.

Invisible electronics, he adds, is a concept looking for the right technology. Although Marks has now made a major breakthrough, we're still a long way from the big screens you see on the big screen.

0 Comments:

Post a Comment

<< Home