Flat, Flexible, Wireless Power Source Can Go Anywhere

May 23, 2007 feature
Flat, Flexible, Wireless Power Source Can Go Anywhere
The wireless power transmission sheet, shown embedded into a floor. Credit: Takao Someya

A team of Japanese researchers has created a novel wireless power-transmission device that is thin, flat, and flexible. Based on a sheet of plastic, the device can be put on desks, floors, walls, and almost any other location, delivering power to electronics placed on or near it without the use of cables or connectors.

The power sheet is described in the April 29, 2007, online edition of Nature Materials.

Flat, Flexible, Wireless Power Source Can Go Anywhere
A small Christmas tree lights up when placed on the power sheet.

The electrical components are deposited onto the plastic via state-of-the-art inkjet printing technology using “electronic ink.” The finished product is about one millimeter thick and 21 centimeters square, although power sheets large enough to cover entire walls or floors could potentially be created.

The sheet can deliver up to about 40 watts, enough to power light bulbs and small electronics (cell phones, clocks, etc.) equipped to accept wireless power. The sheet has an impressive 81 percent efficiency, meaning 81 percent of the emitted power is received by devices.

The sheet is a significant step forward for the field of electronics. Corresponding researcher Takao Someya, a scientist at the University of Tokyo, told PhysOrg.com, “Our power-transmission sheet addresses two of the issues facing the electronics field: creating ecologically friendly power systems and developing power-transmission technologies that further the imminent trend of 'ambient electronics' – electronic networks, such as sensors, built into our homes and offices to increase our day-to-day security and convenience.”

The sheet is an example of “organic electronics,” a fast-growing field in which circuits are based on conducting plastics rather than conventional silicon. Organic electronics have several advantages, including being cheaper to manufacture, more environmentally safe to produce, physically light, and, as in this case, are often thin and bendable.

Flat, Flexible, Wireless Power Source Can Go Anywhere
An LED in water, lit by power from the power sheet, poses no danger to a goldfish.

However, many organic electronic devices can only be integrated into low-power applications because organic transistors have high electrical resistances and cannot handle large amounts of electricity. By combining organic transistors with a technology traditionally used to fabricate silicon circuits, Someya and his colleagues have boosted the amount of power their organic power-transmission sheet can handle.

The finished product consists of several layers. These include a layer printed with an array of thin, flat copper coils, which sense the position of nearby electronic devices, and a layer of sender coils that deliver the wireless power. This process occurs via electromagnetic induction, a physics phenomenon in which a magnetic field can induce a current in a nearby conductor. Here, a voltage applied across the sender coils produces a magnetic field, which induces current flow in nearby devices that need power, as long as those devices are equipped with receiver coils.

Someya and his colleagues say that any potential safety concerns regarding wireless power, such as electric shock and leakages, have been addressed by coating the power sheet's sender coils and other electrical components with an insulating material. They demonstrated the system's safety by using the sheet to power a light bulb submerged in water.

“This could lead to a whole new class of water-safe electronics,” said Someya.

Citation: Tsuyoshi Sekitani, Makoto Takamiya, Yoshiaki Noguchi, Shintaro Nakano, Yusaku Kato, Takayasu Sakurai and Takao Someya, “A large-area wireless power-transmission sheet using printed organic transistors and plastic MEMS switches” Nature advance online publication DOI: 10.1038/nmat1903

Copyright 2007 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: 'Squid skin' metamaterials project yields vivid color display

add to favorites email to friend print save as pdf

Related Stories

First graphene-based flexible display produced

Sep 05, 2014

(Phys.org) —A flexible display incorporating graphene in its pixels' electronics has been successfully demonstrated by the Cambridge Graphene Centre and Plastic Logic, the first time graphene has been used ...

Weathering the storm

Sep 03, 2014

Old-timers sharing childhood stories about growing up in Maine sometimes recount hiking 10 miles uphill in 3 feet of snow to get to school—and home.

Breakthrough for carbon nanotube solar cells

Sep 03, 2014

Lighter, more flexible, and cheaper than conventional solar-cell materials, carbon nanotubes (CNTs) have long shown promise for photovoltaics. But research stalled when CNTs proved to be inefficient, converting ...

Recommended for you

New complex oxides could advance memory devices

21 minutes ago

The quest for the ultimate memory device for computing may have just taken an encouraging step forward. Researchers at The City College of New York led by chemist Stephen O'Brien have discovered new complex ...

Mechanical behavior of twinned aluminum revealed

Sep 15, 2014

A research group has discovered plasticity and work-hardening behaviors in twinned aluminum with incoherent twin boundaries by using in situ nanoindentation technique. The group's paper titled "In situ nanoindentation ...

Invisibility cloaks closer thanks to 'digital metamaterials'

Sep 15, 2014

The concept of "digital metamaterials" – a simple way of designing metamaterials with bizarre optical properties that could hasten the development of devices such as invisibility cloaks and superlenses – is reported in a paper published today in Nature ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

gardoglee
not rated yet Jan 28, 2008
The concept of water safe electronics is intereateing, but if these could also be made explosive environment safe then they could have a tremendous practical commercial application.