A metamaterial “superlens” has been developed that can dramatically increase the range of wireless power transfer, according to a new study. Although previous attempts to transmit energy through air have only produced unwieldy devices that operate over small distances, this new approach used metamaterials to develop a square superlens that efficiently focuses magnetic fields over much greater distances than the size of the transmitter and receiver. The concept appears to be a viable way of manipulating the near fields, and could lead to a significant extension in the usable volume from “power hot spots”.
A multi-disciplinary team from Duke University, whose research – which has connections to the automotive and radio frequency identification (RFID) industry – was published in Scientific Reports [Lipworth, et al., Sci. Rep. (2014), doi:10.1038/srep03642], created a superlens with the exterior and interior walls of each hollow block being etched with long, spiraling copper wire, with the end of each coil connected to its twin on the reverse side of the wall. The repetitive nature and geometry of the wire form a metamaterial that interacts with magnetic fields so that the fields are transmitted and confined into a narrow cone in which the power intensity is much higher.
Although metamaterial-enhanced wireless power has previously been demonstrated, the distance the power was transmitted over was about the same as the diameter of the power coils; it would be more useful to have a wireless power system that allows you to charge a device wherever it is. With the superlens, the magnetic field is focused nearly a foot away with sufficient strength to induce electric current in the identically sized receiver coil. As team leader Yaroslav Urzhumov points out, “We want to be able to use small-size sources and/or receivers, and that's what the superlens enables us to do.”
The team are looking to develop a tunable superlens that controls the direction of its focused power cone. Access to magnetic materials that have combinations of properties unavailable in natural media could lead to applications in radio-frequency noise filters and magnetic resonance imaging, and benefit from advancements in the field of 3D printing and other free-forming technologies. However, they need to significantly upgrade their concept to make it more suited to powering consumer electronics.