Plastic sheet delivers wireless power

news@nature.com ^ | 29 April 2007 | Tom Geller

[neverdem]

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Published online: 29 April 2007; | doi:10.1038/news070423-11

Plastic sheet delivers wireless power

Desks and walls could one day light up electronics without need for cables.

Tom Geller

This table can power a light placed above it — even one that's underwater. Takao Someya and colleauges

Annoyed by the tangle of power cords under your desk? A sheet of plastic invented by researchers in Japan could one day make for tables and walls that power devices placed on them — without any need for wires or plugs. Computers could be powered through the desks on which they sit, for example, or flat-screen televisions through the walls where they hang.

The team of seven researchers at the University of Tokyo has produced a sample sheet of the plastic, which is about the size of a very thin magazine — just one millimetre thick and weighing 50 grams. It can deliver up to 40 watts of power to products on or near it that contain a special 'receiving coil': enough to power a lightbulb or a very small laptop. They say that scaled-up production of such sheets could be inexpensive enough for widespread installation in desks, floors, ceilings and walls, ushering in a "new class of electronic devices".

The plastic, described today in Nature Materials¹, has as its base a layer of transistor featuring pentacene, an organic molecule whose electrical conductivity can be controlled. Topping that are layers holding copper coils that can sense whether a compatible electronic device is nearby, microelectromechanical-system (MEMS) switches that serve to turn on and off the power, and copper coils to transmit electricity.

When the sheet itself is plugged in, it can power devices — such as light-emitting diodes (LEDs) strung on a Christmas tree — that are built with a matching receiver coil. When these are placed within 2.5 centimetres of the sheet, the nearest MEMS switch turns on, feeding power to the closest sender coil, which powers the device's receiving coil through induction.

The researchers say the transmission of power happens with 81.4% efficiency — compared to 93% efficiency in the wired grid network as a whole — with a "quite low" level of leaked electromagnetic radiation. As a demonstration of the product's safety, the paper shows it powering an LED at the bottom of a bowl containing water and a live fish.

All four layers are produced by literally printing them — the coils using screen printing, the switch and transistor layers with an ink-jet printer (using special electronic inks). So the product is thin, lightweight and mechanically flexible.

Power pad

Wireless power systems are nothing new: many electric toothbrushes are charged wirelessly by standing them in a powered base where electrical contacts come in touch with each other, for example. And several companies offer power 'pads' that, when plugged in, will charge specially developed devices, such as compatible mobile phones, simply by placing them anywhere on the pad's surface. But these use silicon-based transistors, which are harder to manufacture and so are more expensive. Printable organic transistors can theoretically be made of any size, at a considerably lower cost.

Roger T. Howe, an electrical engineer at Stanford University in Palo Alto, California, is impressed by the work. "The demonstration of both organic transistors and MEMS switches in a useful system makes it impressive," he says.

But don't throw out your power cords yet: the researchers say that these plastic power sheets probably won't hit the market for 5 years, while they improve their reliability and stability. However, they have received "lots of feedback from many companies", and project a target manufacturing cost of US$100 per square metre. Then there's still the trick of getting device manufacturers to put the receiving coils into their products to make them compatible. But should that happen, you may someday enjoy a world with ubiquitous power — and no power cords.

Visit our newsblog to read and post comments about this story.

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References

1. Sekitani T., et al. Nature Materials, advance online publication; doi:10.1038/nmat1903 (2007).

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[Wiz]

ping

[familyop]

But beware of nerve attenuation syndrome.

[Pontiac]

The researchers say the transmission of power happens with 81.4% efficiency — compared to 93% efficiency in the wired grid network as a whole

Your loosing 12% efficiency.

When these are placed within 2.5 centimetres of the sheet, the nearest MEMS switch turns on, feeding power to the closest sender coil, which powers the device's receiving coil through induction.

So this pad will have to basically cover your entire desk top.

project a target manufacturing cost of US$100 per square metre.

To cover the average desk $150. You can get a quality surge protected power strip for under $20. So far I am not impressed enough to put out that kind of money.

[Fresh Wind]

“Wired grid network as a whole”?

What is that supposed to mean? The computer’s power cord? The power cord plus the wiring in your house? The power cord plus the wiring in your house plus the wiring to the transformer on the telephone pole? All that plus the wiring to the substation? All that plus the wiring to the power plant?

A meaningful efficiency comparison would stop at the wall outlet since that’s where the power sheet would be plugged in.

If you were losing 7% in a power cord, it would be hot to the touch, so that’s obviously not what they mean.

In other words, they’re lying about power losses.

[saganite]

I can see uses for this. Aircraft tray tables for instance that would continually charge your laptop or a conference table that would do the same. In some instances it’s not a matter of electrical efficiency but more a matter of human efficiency.

[Fairview]

I’d buy it if it cost twice as much. I detest this spaghetti-like tangle of cords behind my machinery: speakers, two printers, monitor, lamp, the computer itself, and the massive battery backup. Ech.

[JeanLM]

Would be very good on a roof though. Lots of flat roofs to cover out there. Forget the desktop. Look up on the roof. Market for single ply plastic roofs is 1 billion square feet annually. (90,000,000 m2). That’s a lot of power generation possibility.

[Red Badger]

Blow-up dolls will never be the same..................(not that i would know)......

[Red Badger]

I’d buy it if it cost twice as much.

Anything to get rid of the "wall-warts".....(little black transformers).........

[Little Pig]

Except that this is not a solar panel. You plug the sheet into the wall, then anything that sits on it receives power from it.

Or were you planning to put your PC up on your roof?

[ASOC]

Only for power, you would still have signal cables.

For folks freak out over WiFI, cell phones and power lines, this stuff would be like sleeping with the Devil hissself.

[neverdem]

Reversing Alzheimer's memory loss may be possible

Australian marsupials challenge gene theory

When smell cells fail they call in stem cell reserves

FReepmail me if you want on or off my health and science ping list.

[SunkenCiv]

This new technology is known to have caused brain cancer IN THE FUTURE!!! ;’)

[SunkenCiv]

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[Pontiac]

Anything to get rid of the "wall-warts".....(little black transformers).........

That is something that is not addressed by this device. Almost all of the devices that would be sitting on your desktop have very specific power requirements and they are all different.

Either you would have to have the transformer on your desk top or it would have to be built in to your devices in anticipation of you using this power sheet.