系，以及軍事奈米技術研究所（Institute for Soldier Nanotechnologies）的研究人員所共同
|Sci-Tech-Prod (Science-Technology-Products) Village: 科學技術產品村: 011
|Wireless energy could power consumer, industrial electronics: 跟電線說 bye-bye MIT 研究出無線輸電技術
received from Pi-Twan Huang 黃碧端
文/陳曉莉 (編譯) 2007-06-11
Researchers present a graphic illustrating how magnetism can transmit energy
wirelessly. Marin Soljacic, left, assistant professor of physics, Aristeidis Karalis, G,
and John Joannopoulos, professor of physics, use theoretical calculations and
computer simulations to find ways to recharge electronics wirelessly. Enlarge image
Dead cell phone inspired researcher's innovation
Davide Castelvecchi, American Institute of Physics
November 14, 2006
Recharging your laptop computer, your cell phone and a variety of other gadgets
may one day be as convenient as surfing the web--wirelessly.
Marin Soljacic, an assistant professor in MIT's Department of Physics and
Research Laboratory of Electronics, will describe his and his MIT colleagues'
research on that wireless future on Tuesday, Nov. 14 at the American Institute of
Physics Industrial Physics Forum in San Francisco.
Like many of us, Soljacic (pronounced Soul-ya-CHEECH) often forgets to recharge
his cell phone, and when it is about to die it emits an unpleasant noise. "Needless
to say, this always happens in the middle of the night," he said. "So, one night, at 3
a.m., it occurred to me: Wouldn't it be great if this thing charged itself?" He began to
wonder if any of the physics principles he knew of could turn into new ways of
After all, scientists and engineers have known for nearly two centuries that
transferring electric power does not require wires to be in physical contact. Electric
motors and power transformers contain coils that transmit energy to each other by
the phenomenon of electromagnetic induction. A current running in an emitting coil
induces another current in a receiving coil; the two coils are in close proximity, but
they do not touch.
Later, scientists discovered electromagnetic radiation in the form of radio waves,
and they showed that another form of it--light--is how we get energy from the sun.
But transferring energy from one point to another through ordinary electromagnetic
radiation is typically very inefficient: The waves tend to spread in all directions, so
most of the energy is lost to the environment.
Soljacic realized that the close-range induction taking place inside a transformer--or
something similar to it--could potentially transfer energy over longer distances, say,
from one end of a room to the other. Instead of irradiating the environment with
electromagnetic waves, a power transmitter would fill the space around it with a
"non-radiative" electromagnetic field. Energy would only be picked up by gadgets
specially designed to "resonate" with the field. Most of the energy not picked up by a
receiver would be reabsorbed by the emitter.
In his talk, Soljacic will explain the physics of non-radiative energy transfer and the
possible design of wireless-power systems.
While rooted in well-known laws of physics, non-radiative energy transfer is a novel
application no one seems to have pursued before. "It certainly was not clear or
obvious to us in the beginning how well it could actually work, given the constraints
of available materials, extraneous environmental objects, and so on. It was even
less clear to us which designs would work best," Soljacic said. He and his
colleagues tackled the problem through theoretical calculations and computer
With the resulting designs, non-radiative wireless power would have limited range,
and the range would be shorter for smaller-size receivers. But the team calculates
that an object the size of a laptop could be recharged within a few meters of the
power source. Placing one source in each room could provide coverage throughout
Soljacic is looking forward to a future when laptops and cell phones might never
need any wires at all. Wireless, he said, could also power other household gadgets
that are now becoming more common. "At home, I have one of those robotic
vacuum cleaners that cleans your floors automatically," he said. "It does a fantastic
job but, after it cleans one or two rooms, the battery dies." In addition to consumer
electronics, wireless energy could find industrial applications powering, for
example, freely roaming robots within a factory pavilion.
Soljacic's colleagues in the work are Aristeidis Karalis, a graduate student in the
Department of Electrical Engineering and Computer Science, and John
Joannopoulos, the Francis Wright Davis Professor of Physics. Both are also
affiliated with the Research Laboratory of Electronics. The work is funded in part by
the Materials Research Science and Engineering Center program of the National
A version of this article appeared in MIT Tech Talk on November 15, 2006