Power-Transmitting Sheet embedded in the floorWhat would you say if in a few years from now you would not need a power cord to charge your notebook or to deal with those annoying, tangled up cords behind your TV and stereo? Or would you imagine that your PDA or cell phone could be recharged remotely? I would say it is something rather from a more distant future, but research scientists at the University of Tokyo have come up with a unique material that can transmit electrical energy to nearby devices without the need for direct contact. The system is based on a well know phenomenon discovered by Faraday in 1831 – electromagnetic induction – when electrical energy can be transmitted without a contact, just like some electric toothbrushes that recharge while sitting in a plastic charger.

The power-transmitting material is a plastic film with imprinted elements:

  1. Japanese Researcher’s knowhow – a contactless position-sensing system that allows to direct power to wherever the appliance sits . It has a two-dimensional grid of copper coils and a matrix of transistors made from the organic molecule pentacene.
  2. Switching mechanism consisting of an arrangement of plastic microelectromechanical system (MEMS) switches, which direct the power to the device.
  3. A second two-dimensional layer of copper coils that transmits the energy.

The sheet is 21×21 cm, 1 mm thick, and weighs 50 g. It contains a grid of 64 position-sensing units and 64 power-transmission units. The sheet is capable of providing 40.5 watts of power with more than 80% efficiency – sufficient to operate a small laptop computer.

When an electronic device containing a ‘receiving coil’ is next to the sheet, its presence is detected by the positioning coils, and coordinates relayed by the organic transistor circuit. The MEMS switches then direct the power to that point.

A head of research group Takao Sekitani comments:

“Since all the device components are manufactured on plastic films, the system is thin, lightweight and flexible. Therefore it is easy to put the sheet system in the wall, desk, floor – anywhere you can imagine. And because the system is manufactured by printing technologies it is potentially low-cost and it can transmit high power selectively to the position of electronic objects, making transmission loss very small.”

Example of power transmission to LED in water:

Fish Tank
Reference: T Sekitani et al, Nat. Mater., DOI: 10.1038/nmat1903