Wireless power transfer enhanced by metamaterials

April 30, 2015 by Lisa Zyga feature
WPT
Wireless power transfer between two coils. The metamaterial is the gray 3 x 3 square embedded into the coil on the right. Credit: Q. Wu, et al. ©2015 EPLA

(Phys.org)—Over the past decade, research on wireless power transfer has led to the development of several commercial applications, such as wireless charging of mobile devices and electric toothbrushes, as well as wireless powering of radio-frequency identification (RFID) tags. However, these applications are restricted by limitations on the distance and efficiency of current wireless power transfer technology.

In a new study published in EPL, scientists at Tongji University in Shanghai, China, have experimentally demonstrated a way to improve the of by using magnetic metamaterials. The new method improves the efficiency of the design from a few percent to nearly 20% at a distance of 4 cm, which could pave the way toward new applications, including wireless charging of implanted pacemakers and electric vehicles.

The concept of wireless power transfer dates back to the 1890s, when Nikola Tesla began experimenting with wireless electricity with limited success. Now more than a century later, the idea has again attracted attention. In 2007, for example, MIT researchers demonstrated wireless power transfer and have been developing products under the start-up "Witricity."

Coincidentally, metamaterials have had a somewhat similar history. Around the turn of the 20th century, scientists began exploring the idea of artificial materials that could manipulate light in unusual ways, but not until the early 2000s were true metamaterials first fabricated.

In the new paper, the Tongji researchers have embedded magnetic metamaterials into the coils used in non-radiative wireless power transfer, which is the method used by most of today's wireless power transfer applications. In the researchers' design, one coil creates a magnetic field, which is captured by the second coil as voltage.

(a) A large increase in transfer efficiency (purple line) at a distance of 2 cm is measured when both the transmitting and receiving coils (T and R, respectively) are embedded with the metamaterial (yellow). (b) Measured efficiencies at different distances for the case where both coils are embedded with the metamaterial. Although the efficiency drops as transfer distance increases, the efficiency near 20% at 4 cm (blue line) is ideal for some medical devices, such as wireless charging for implanted heart pacemakers. Credit: Q. Wu, et al. ©2015 EPLA

Like all metamaterials, the ones used here contain subwavelength microstructures that can manipulate electromagnetic waves in ways not possible with other materials. Here, the metamaterials are assembled with "meta-atoms," which are 2.6-cm etchings on the spiral copper coils.

This particular size of 2.6 cm is important because it allows for strong coupling between the deep subwavelength resonant modes of the meta-atoms, and this coupling is responsible for increasing the transfer efficiency.

"By embedding metamaterials into non-resonant coils, the overall efficiency of the wireless power transfer system is found to be greatly enhanced, due to the coupling between metamaterials," the researchers wrote in their paper.

Although the efficiency decays quickly as distance increases—from 32% at 3 cm to 15% at 5 cm—the 20% efficiency near 4 cm marks a sweet spot for certain applications, such as of pacemakers and other medical devices.

In the future, the researchers hope to build on this metamaterial-enhanced wireless power transfer method to develop many other applications. The scientists expect that, due to the metamaterials' homogenous magnetic behavior, the metamaterials can be assembled like ordinary materials, and so can avoid the technical fabrication challenges that many metamaterials face.

"Since the transfer system based on metamaterials has many benefits, we believe it can be widely used in medical research, electric vehicle charging, the civilian industry, and so on," the researchers wrote.

Explore further: Key factors for wireless power transfer

More information: Q. Wu, et al. "Wireless power transfer based on magnetic metamaterials consisting of assembled ultrasubwavelength meta-atoms." EPL. DOI: 10.1209/0295-5075/109/68005

Related Stories

Key factors for wireless power transfer

July 31, 2013

What happens to a resonant wireless power transfer system in the presence of complex electromagnetic environments, such as metal plates? A team of researchers explored the influences at play in this type of situation, and ...

Researchers develop new wireless power transfer technique

August 4, 2014

A wireless power transfer technique that uses miniaturised receivers suitable for real-world use has been demonstrated by researchers in Korea. Hyoungjun Kim and Chulhun Seo from Soongsil University used a metamaterial slab ...

Metamaterials shine bright as new terahertz source

April 23, 2015

Metamaterials allow design and use of light-matter interactions at a fundamental level. An efficient terahertz emission from two-dimensional arrays of gold split-ring resonator metamaterials was discovered as a result of ...

'Superlens' extends range of wireless power transfer

January 10, 2014

(Phys.org) —Inventor Nikola Tesla imagined the technology to transmit energy through thin air almost a century ago, but experimental attempts at the feat have so far resulted in cumbersome devices that only work over very ...

Recommended for you

Carefully crafted light pulses control neuron activity

November 17, 2017

Specially tailored, ultrafast pulses of light can trigger neurons to fire and could one day help patients with light-sensitive circadian or mood problems, according to a new study in mice at the University of Illinois.

Strain-free epitaxy of germanium film on mica

November 17, 2017

Germanium, an elemental semiconductor, was the material of choice in the early history of electronic devices, before it was largely replaced by silicon. But due to its high charge carrier mobility—higher than silicon by ...

New imaging technique peers inside living cells

November 16, 2017

To undergo high-resolution imaging, cells often must be sliced and diced, dehydrated, painted with toxic stains, or embedded in resin. For cells, the result is certain death.

The stacked color sensor

November 16, 2017

Red-sensitive, blue-sensitive and green-sensitive color sensors stacked on top of each other instead of being lined up in a mosaic pattern – this principle could allow image sensors with unprecedented resolution and sensitivity ...

27 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

gkam
1 / 5 (4) Apr 30, 2015
It is still using magnetic fields as the interconnection, just like we do in transformers. Most folk do not understand there are no direct connections between the primary and secondary current-carrying conductors. The entire grid is supplied by magnetic fields, the same kind which generate the electricity in the first place.

Tesla's coil was a simple inductor producing high electric fields which produced his action at a distance. They were not the magnetic fields we use to supply and transform electricity. today.
katesisco
5 / 5 (2) Apr 30, 2015
I wish magnetism and its applications were introduced in grade school. Perhaps I would not be so confused about Tesla's claim that there is a separate energy alongside the electron stream we know as electricity. I am reading An Ocean of Air by G Walker and I am astounded by the pattern of discoveries that air is a combination of gases, once thought to be one. Is this the way our concept of the power stream that carries electricity among other as yet unidentified power flows will resolve? That electron bonding is only one form?
gkam
1.6 / 5 (5) Apr 30, 2015
kate, good questions. We know much more about the flow of electricity now than we did about the composition of the air. I think Tesla was still theorizing without a background of knowledge. Not all of his ideas were practical, especially the one of power transmission through the air.
Eikka
5 / 5 (2) Apr 30, 2015
Tesla's coil was a simple inductor producing high electric fields which produced his action at a distance. They were not the magnetic fields we use to supply and transform electricity. today.


The story behind Tesla's idea of wireless electricity transmission is a bit more complex than simply electric fields. He had apparently observed what is called the Schumann resonance which is basically a radio wave that keeps travelling around the waveguide formed by the ionosphere and the ground.

There's an approximately 7.85 Hz oscillation going on, which gets more energy from lightning strikes and other radio interference, and Tesla - misunderstanding what this is about - took to believe he could charge up the wave by injecting energy with massive Tesla coils and then collecting the energy back at another location.

It "works", you can excite the Schumann resonance artifically, but getting energy out is another matter entirely.

Eikka
5 / 5 (2) Apr 30, 2015
Perhaps I would not be so confused about Tesla's claim that there is a separate energy alongside the electron stream we know as electricity.


As far as I know, Tesla wasn't a firm believer of the modern theory of atoms, and he disagreed entirely about the existence of the electron along with every other sub-atomic particle. To Tesla, the atom was the smallest particle and they were immutable and un-breakable.

Electrons, if they existed, couldn't have anything to do with electricity - and he argued against the experiental proof for electrons' existence as being an artifact of the experiment. They would be artifical "sub-atoms".

His basic stance was that empty space has no properties and cannot carry fields of force or curve like Einstein said; that only substance can affect substance. Therefore there must exist an all-pervasive invisible ether-stuff that flows everywhere between the atoms and this fluid is what carries electricity.

Eikka
5 / 5 (2) Apr 30, 2015
Is this the way our concept of the power stream that carries electricity among other as yet unidentified power flows will resolve? That electron bonding is only one form?


Other flows than "Electron bonding" have been identified. Technically, electricity itself isn't carried by electrons but by charge. One can just as well move a bunch of naked protons and call that electricity.

That's the difference between Tesla and modern physics. Tesla didn't believe there exists this "charge" that was without substance, because it would have implied fields of force instead of stuff pushing against ether pushing against other stuff.

To Tesla, space was full of stuff - how else would anything move? To modern physics, space is empty but full of fields, and there's barely any stuff in it at all.
gkam
1 / 5 (4) Apr 30, 2015
"One can just as well move a bunch of naked protons and call that electricity. "
------------------------------------

We use hole-flow in often semiconductor theory.
Eikka
5 / 5 (3) Apr 30, 2015
"One can just as well move a bunch of naked protons and call that electricity. "
------------------------------------

We use hole-flow in often semiconductor theory.


Indeed, and there you're literally moving nothing at all.

But in actuality, moving the holes implies movement of electrons to fill the previous hole and open up another one, so that's not a very good example. It's not a different thing - just a difference in perspective.
Urgelt
5 / 5 (1) May 01, 2015
Wait, what?

Telsa is mentioned, and the discussion here verges on sanity?

I must be dreaming.
PPihkala
2 / 5 (1) May 02, 2015
Telsa is mentioned, and the discussion here verges on sanity?

His name was Nikola Tesla, not Telsa. Why don't people learn to write people's names the correct way?
As far as I know it is a common misconception that Tesla was trying to move power through air. It was through ground like Eikka wrote. People just could not see what was under the Wardenclyffe tower.
gkam
1 / 5 (4) May 02, 2015
PP, you need more than just the atmosphere or the Earth, you need them both, for electricity is a differential charge.
KBK
5 / 5 (2) May 04, 2015
The core issue is that the human body is incredibly sensitive to electrical fields, fields in modulation. We are electrochemical creatures and our bodies operate on very miniscule levels of charge differential, in the chemical domain. It is gets more complex than that, but suffice it to say we are definitely inclusive of being electrical in nature. Subtle levels of electricity.

This means we should not be putting any form of high low or medium power RF or EM energies anywhere near the human body. It would severely damage human body function.

This means that this particular idea of electrical power transmission to objects in the human sphere of living, is RETARDED in the extreme and should not be attempted, in any way.

Whomever promotes this stuff is either malignant or ignorant, and they need a good boot up their ass. It boggles my mind..... the sheer Darwinian idiocy of this crap.

Some things should not be done, and this is one of those things that should not be done.
gkam
1 / 5 (4) May 04, 2015
KBK is correct. Mammals are very sensitive to electricity. For example, having worked with "stray voltages" produced by long utility radials, we had to make sure there was not as much as one-half Volt between any places in dairy barns. Since it only takes one milliampere for detection in mammals, the 560-Ohm cow is will shut off milk production if only one half Volt is present between hoof and lip.
gkam
1 / 5 (5) May 04, 2015
I am waiting for challenges to my very specific post regarding the susceptibility of mammals to electricity, and their inherent electrical resistance, from otto-wiki and his puppets.

I will be glad to explain how it works to them.
TheGhostofOtto1923
3 / 5 (4) May 04, 2015
I am waiting for challenges to my very specific post regarding the susceptibility of mammals to electricity
Well I am waiting for satisfactory explanations for the following gkam bullshit:

-HIGH ENERGY alpha cant penetrate skin

-Fallout is the MAJOR cause of lung cancer (not even on the list)

-Fukushima H2 explosions can cause Pu nuclear detonations which throw macroscopic vessel parts 130km without making a crater

-There is plutonium raining down on idaho

-Swimming pools are commonly being used to cool houses

-Only 1 scientist ever concluded that the next ice age is imminent

-Thorium reactor research is being abandoned worldwide

-Radiation exposure (including HIGH ENERGY alpha) cant kill you in minutes

-In your professional opinion floating concentrated power stations cannot be installed on reservoirs even though you 'evaluated' such a system 25 years ago

-Youre an engineer

-Etcetcetcetc

-as well as some indication of when its going to stop.
TheGhostofOtto1923
3 / 5 (4) May 04, 2015
@pikahalla
As far as I know it is a common misconception that Tesla was trying to move power through air
Well if you knew a little farther you would realize that you can look these things up on the internet. Which is, after all, where we are.

"Inventor Nikola Tesla performed the first experiments in wireless power transmission at the turn of the 20th century, and may have done more to popularize the idea than any other individual. In the period 1891 to 1904 he experimented with transmitting power by inductive and capacitive coupling using spark-excited radio frequency resonant transformers, now called Tesla coils, which generated high AC voltages."
gkam
1 / 5 (5) May 04, 2015
Oh, wow, an instant wiki-expert on high frequency, high voltage generation!
TheGhostofOtto1923
3.7 / 5 (3) May 05, 2015
See, the bullshit artistes gkam doesn't care whether facts are valid or not, he only cares where they come from.
TheGhostofOtto1923
3 / 5 (4) May 05, 2015
Gkam also claimed that tesla never attempted wireless power transmission either. Remember that George? This is why people like you fear the Internet. No place to hide here.

That's why it's so funny when you claim that your experience has taught you certain things, and a rudimentary search proves you wrong. This both disproves what you know, and the quality of the 'experience' that informed you; thereby making you look like an ass twicefold. Asshole squared. Ahaahaaaaa.
gkam
1 / 5 (4) May 05, 2015
" Asshole squared. Ahaahaaaaa."
------------------------------------------
Can we get rid of these vandals hiding behind pseudonyms?

This is a science forum, not detention.
TheGhostofOtto1923
4 / 5 (4) May 06, 2015
" Asshole squared. Ahaahaaaaa."
------------------------------------------
Can we get rid of these vandals hiding behind pseudonyms?

This is a science forum, not detention.
Can we get rid of these vandals hiding behind phony CVs and false claims of 'experience'? This is a science forum not the bar down at the VFW.

99% of the posters here use pseudonyms. If 'we' got rid of them you'd be bullshitting to an empty theatre.
gkam
1 / 5 (4) May 06, 2015
I am already talking to cowardly sniper, one who admitted he played "games" in these fora, using a variety of pseudonyms. You outed yourself, you fool.
Urgelt
5 / 5 (2) May 06, 2015
PPihkala wrote, "His name was Nikola Tesla, not Telsa. Why don't people learn to write people's names the correct way?"

Pretty harsh response to an innocent typo.

Here's the right way to respond to a typo: 'Hey, dude, you misspelled Tesla.' Then I go 'oops!' and we move on. No condemnations needed.

gkam
1 / 5 (5) May 06, 2015
Urgelt, wait until you run into otto, who screams "liar" and "bullshit" in all caps.
TheGhostofOtto1923
3 / 5 (4) May 06, 2015
I am already talking to cowardly sniper, one who admitted he played "games" in these fora, using a variety of pseudonyms. You outed yourself, you fool
George. Even if your allegations were true (theyre not) it would not make the nonsense you post any more valid.

The facts speak for themselves. Your facts are wrong despite your alleged 'experience'. My facts are right because I get them from genuine experts.

Look at all the stuff you got wrong in this thread
http://phys.org/n...rgy.html

-and the only rebut you ever have, is your worthless 'experience'.

The FACT that you cannot realize this despite months of being shown the truth, indicates that your connection with this world is fading fast. Or it could indicate overmedication on VA drugs and creams.

"Doctors at the U.S. DVA medical center in Tomah, Wisc, hand out so many narcotic painkillers that some veterans have taken to calling the place "Candy Land."
Urgelt
5 / 5 (1) May 06, 2015
gkam, I've coexisted with Otto for years in this forum. He's never taken a swipe at me, possibly because if I'm determined to sprout fringe nonsense, I label it as such before I begin.

Alas, many posters here are genuinely deluded.

Cranks are easy to spot. They're dead certain; they despise peer-reviewed science; they always have answers where real scientists mainly have questions. And they're loud, repetitive and insulting.

Then you have the crank-haters. Alas for my soul, I fall into that category myself, though I try not to be too insufferably offensive about it. But it annoys me that where an opportunity for legitimate public discussion about science exists, it's invariably flooded by cranks and crank-haters, so much so that meaningful discussion becomes an exercise in tedious wading through awful junk.

The Phys.org comment system could be valuable. We, the users, have made that nearly impossible.
gkam
1 / 5 (4) May 06, 2015
Some gamers have so many pseudonyms, they call themselves various forms of otto, probably teutonic.

otto, you blew your own cover when you bragged about your aliases and how you like to play "games" with us online.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.