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Piezoelectric Graphene

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March 16, 2012 – Comments (2)

Piezoelectrics = cool
Graphene = cool
Piezoelectric Graphene = double cool

Obviously just do the math :)

But seriously, I keep referring to all these graphene articles because it is such an impressive material. Materials science advancements have led many of the previous scientific and engineering booms over the last century. And I think graphene studies will turn into applications that lead another such boom.

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Straintronics: Engineers Create Piezoelectric Graphene
ScienceDaily (Mar. 16, 2012)

http://www.sciencedaily.com/releases/2012/03/120316094535.htm

Yet, while graphene is many things, it is not piezoelectric. Piezoelectricity is the property of some materials to produce electric charge when bent, squeezed or twisted. Perhaps more importantly, piezoelectricity is reversible. When an electric field is applied, piezoelectric materials change shape, yielding a remarkable level of engineering control.

Piezoelectrics have found application in countless devices from watches, radios and ultrasound to the push-button starters on propane grills, but these uses all require relatively large, three-dimensional quantities of piezoelectric materials.

Now, in a paper published in the journal ACS Nano, two materials engineers at Stanford have described how they have engineered piezoelectrics into graphene, extending for the first time such fine physical control to the nanoscale.

Straintronics

"The physical deformations we can create are directly proportional to the electrical field applied and this represents a fundamentally new way to control electronics at the nanoscale," said Evan Reed, head of the Materials Computation and Theory Group at Stanford and senior author of the study. "This phenomenon brings new dimension to the concept of 'straintronics' for the way the electrical field strains -- or deforms -- the lattice of carbon, causing it to change shape in predictable ways."

"Piezoelectric graphene could provide an unparalleled degree of electrical, optical or mechanical control for applications ranging from touchscreens to nanoscale transistors," said Mitchell Ong, a post-doctoral scholar in Reed's lab and first author of the paper.

Using a sophisticated modeling application running on high-performance supercomputers, the engineers simulated the deposition of atoms on one side of a graphene lattice -- a process known as doping -- and measured the piezoelectric effect.

They modeled graphene doped with lithium, hydrogen, potassium and fluorine, as well as combinations of hydrogen and fluorine and lithium and fluorine on either side of the lattice. Doping just one side of the graphene, or doping both sides with different atoms, is key to the process as it breaks graphene's perfect physical symmetry, which otherwise cancels the piezoelectric effect.

The results surprised both engineers.

"We thought the piezoelectric effect would be present, but relatively small. Yet, we were able to achieve piezoelectric levels comparable to traditional three-dimensional materials," said Reed. "It was pretty significant."

2 Comments – Post Your Own

#1) On March 17, 2012 at 2:53 AM, traderbach (< 20) wrote:

Hey Binve,

 I've been amazed at reading about graphene & watching some of the youtube videos on its applications.  Question is who will be the leader in the manufacture & utilization of graphene? Or will there be a leader at all being that the manufacture is fairly simple & the raw materials for that plentiful.  Seems like it might be ubiquitous, like plastic, but not from a very finite supply like hydrocarbons.  There is no doubt that it is a revolution of awesome potential that will allow many of man's technological future dreams to become reality.

I always enjoy your blogs.  Thanks.

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#2) On March 18, 2012 at 10:35 AM, binve (< 20) wrote:

Hi traderbach, thanks I appreciate that.

It is a good question and I think it is too early to say. The production of graphene is still very much the realm of research facilities (although we have come far since the 'scotch-tape' method).

My guess is that this will shake out something like the carbon fiber industry. Several companies will make low modulus low strength carbon fibers (low cost/high volume), a few companies will specialize in high modulus high strength (high cost/low volume) graphite fibers, and the there will be several system integrators for panels / frames / etc.

But graphene is going to be at least an order of magnitude more useful to a wide variety of industries than cabon fiber. So we are going to see a very diverse production and application chain being set up in the next decade. No idea how it will shake out yet, but I am very excited and think we will all be better off for it.

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