Electrical engineers at Duke Univ.
have determined that unique man-made materials should theoretically make it
possible to improve the power transfer to small devices, such as laptops or
cell phones, or ultimately to larger ones, such as cars or elevators, without
This advance is made possible by the
recent ability to fabricate exotic composite materials known as metamaterials,
which are not so much a single substance, but an entire man-made structure that
can be engineered to exhibit properties not readily found in nature. In fact,
the metamaterial used in earlier Duke studies, and which would likely be used
in future wireless power transmission systems, resembles a miniature set of tan
Theoretically, this metamaterial can
improve the efficiency of “recharging” devices without wires. As power passes
from the transmitting device to the receiving device, most if not all of it
scatters and dissipates unless the two devices are extremely close together.
However, the metamaterial postulated by the Duke researchers, which would be
situated between the energy source and the “recipient” device, greatly
refocuses the energy transmitted and permits the energy to traverse the open
space between with minimal loss of power.
“We currently have the ability to
transmit small amounts of power over short distances, such as in radio
frequency identification (RFID) devices,” said Yaroslav Urzhumov, assistant
research professor in electrical and computer engineering at Duke’s Pratt
School of Engineering. “However, larger amounts of energy, such as that seen in
lasers or microwaves, would burn up anything in its path.
“Based on our calculations, it should
be possible to use these novel metamaterials to increase the amount of power
transmitted without the negative effects,” Urzhumov said.
The results of the Duke research were
published online in the journal Physical
Just as the metamaterial in the
cloaking device appeared to make a volume of space “disappear,” in the latest
work, the metamaterial would make it seem as if there was no space between the
transmitter and the recipient, Urzhumov said. Therefore, he said, the loss of
power should be minimal.
Urzhumov’s research is an offshoot of “superlens” research conducted in Smith’s laboratory.
The metamaterial used in wireless
power transmission would likely be made of hundreds to thousands of individual
thin conducting loops arranged into an array. Each piece is made from the same
copper-on-fiberglass substrate used in printed circuit boards, with excess
copper etched away. These pieces can then be arranged in an almost infinite
variety of configurations.
“The system would need to be tailored
to the specific recipient device, in essence the source and target would need
to be ‘tuned’ to each other,” Urzhumov said. “This new understanding of how
matematerials can be fabricated and arranged should help make the design of
wireless power transmission systems more focused.”