Look closely. This dollhouse is not mere child’s play. It is a picture of the future. A demo of what this century holds for us. A demonstration of a smart carpet, invented by a team of Japanese engineers led by Takao Someya from the School of Engineering, The University of Tokyo. The carpet can supply power to devices without any cards or plugs and pins. All the devices in this dollhouse are powered without being plugged into any power outlet. The carpet provides the power required by them.
Remember how you always get annoyed at the railway station when you can’t find a  spare power point to charge the dying battery of your mobile phone? Or the miserable time spent searching for the right power cord of the printer among the tangled dozen cords of your PCs accessories? Imagine the benefits of such a ‘magic carpet’. No more searching for power sockets. No more tangled cables. Just rest your gadget on the carpet and it gets powered.
The carpet - called a “power transmission sheet” by Someya - is a blend of the latest in material research and nano fabrication technologies. It is made up of sheets of organic conducting polymers, sandwiched between which are delicately crafted copper coils as are also switches and position sensors made up of silver nanoparticles and polymer transistors. The whole carpet works on the principle of “electromagnetic induction,” a phenomenon very familiar to physicists.
To power a device, say a mobile phone, it is placed on the sheet. The sensors in the sheet sense its presence and direct the copper coils near it to draw the power and supply to the phone. A special coil at the bottom of the phone then “inductively” draws power. There are no metallic pins or sockets to plug into. In fact, the device can be placed anywhere, and the sensors dispersed all over the sheet immediately sense its presence and ‘switch’ on only the neighbouring coil. Of course, the carpet is connected to a mains somewhere.
Electromagnetic induction if you remember is the driving force of the receiver antennas of the radio receivers. The radiowaves – a sort of electromagnetic wave – transmitted by our familiar FM stations, cause a current to occur in the antenna, a thin coil of copper in the receivers which is then amplified and converted back into music. In a similar way, the coils in the bottom of the gadgets are inductively powered by the copper coils in the sheet developed by Someya’s team.
“Since all the components are manufactured on plastic films, the system is thin, lightweight, and mechanically flexible. It is easy to place the wireless power transmission sheet on walls, ceilings or in imaginative locations, opening up new ways to interact with electronic products,” says Someya. To power a device, one only has to place it on the sheet. Because the power transmission only occurs selectively when an object is sensed, there is very little transmission loss. Someya’s demo sheet has a net power-coupling efficiency of 81.4%, that is, it transfers 81.4% of power without much trouble. Power levels as high as 40 watts (enough to light a flourescent lamp) have been transferred in this fashion by Someya’s team.
The Japanese invention makes it possible to transmit high power to anywhere over a large area by “spatial subdivision”. In this way, the system selectively feeds power as high as 40 watts to electronic objects placed upon it. The sheet is ultra thin and light weight. - one mm in thickness; a squared meter large sheet weighing only 50 grams -and can be easily manufactured.
“All the device deponents are manufactured on plastic films. The system is thin, lightweight, and flexible. Therefore, it is easy to put the sheet system on the wall, desk, floor - anywhere you can imagine. Secondly, the system is manufactured by printing technologies,” says Someya.
The team used the commonplace inkjet and screen printing to craft their polymer transistor laid sheets, a reason for their very low cost.
“This is the first step towards building infrastructure for ubiquitous electronics where multiple electronic objects are scattered over desks, floors, walls, and ceilings and need to be powered”, exults Someya. Currently, the sheet can transmit a maximum of 40 W using a one inch coil in it which is sufficient to run a laptop.
Devices needing larger power requirements can also be powered by the sheets, in which case more than a single coil is used.
You may also be shocked to hear that you can safely walk, sleep and jog on the “electricity supply sheet”.
“Since the power is transmitted to the exact position where the electronic objects are placed, the risks are less. Furthermore, this is wireless transmission, and there are no plugs. Hence it is much safer than regular methods where plugs and cables are used,” explains Someya. Indeed, the team has powered a light kept in water along with two live fish as shown in the picture.
In just five years, the carpet could be there in the market, by which time Someya hopes, the cost could also be as low as one cent per sq cm of the sheet, making it quite affordable. But then, the gadgets too should be equipped with a receiving coil. When that is realised, with the wifi environment also making its presence, it will be possible to scatter your gadgets all over, and work with all of them.