Graphene goes jiggly

So there’s a cool breakthrough in nanotechnology and electronics, yet I’ve not seen it widely reported for some reason.  On the plus side, this means my late posting is still fairly relevant news.  Korean researchers at Sungkyunkwan University and Samsung have managed to make the nano macro by growing a graphene layer on a 63 centimeter polyester sheet.  If you’re not entirely sure why that is a big deal, well, realize that until recently, one of the most popular methods of making graphene was continually peeling off bits of graphite with scotch tape until you managed to end up with a layer that is only an atom thick.  I’m not joking.  Google “scotch tape method” and although the first result is a Wikipedia page describing a way to diagnose some horrifying tapeworm infection, almost everything else you see is about graphene.  And since the wonderful Scotch tape brand does not come in giant meter sized sheets, you of understand why you don’t see huge hunks of graphene even though its synthesis is pretty understood.

Researchers from UT-Austin showed last year that you can grow graphene on sheets of copper by vaporizing carbon and letting the atoms settle onto the sheet.  The Korean team  took that one step further to get their graphene sheet.  They wrap a flexible copper foil around a cylinder in a furnace, and after the graphene was synthesized, the copper was rolled out and the graphene layer transferred onto a polyester base.

This is important for two main reasons.  First, there’s the fact that now all the synthesis and transfer is occurring on rolls.  Although the team obviously didn’t do it in their first investigation of this method, rolls enable mass production.  As team member Byung Hee Hong points out, roll processes usually allow for continuous films.  It’s very easy to have machines cycling sheets through rollers and transporting or transferring materials.  Think about newspapers.  The second reason this new research is important is the material they transferred the graphene onto.  Graphene itself is very flexible, but most synthesis methods don’t really let you take advantage of that because the graphene is grown on a brittle substrate.   This is why the UT-Austin research was a good stepping stone.  Copper is ductile and can be made into rolls.  Most other graphene substrates would not survive the process.  But the transfer to polyester is even more impressive because the polyester the team used was flexible and transparent.

The last bit is most exciting for applications.  Researchers have dreamed of making new innovative electronics with graphene, because it is very flexible, highly conductive, and almost completely transparent to optical wavelengths.  The polyester base doesn’t disrupt any of those properties.  To the curious, who wondered why Samsung was working on synthesizing graphene, that’s why.  Dreams of foldable electronics are one step closer to being realized with this research.  The lab’s first use of their graphene sheet was as a flexible touch screen.  Of course, other uses care less about the flexibility and more about the fact that you can get a huge sheet of graphene.  Before the technology to make flexible electronic becomes common, Hong mentions that large sheets would also be useful for making economic solar cells or large flat-panel displays.  Although it isn’t mentioned, I want to know if we could use this as a stepping to making graphene’s cousin, carbon nanotubes, more efficiently.  Carbon nanotubes are essentially rolled up graphene sheets, and research has shown you can actually make nanotubes by rolling up graphene nanoribbons).  So could we use this to make foot long nanotubes?  Because I really want to see a nanotube space elevator soon.

P.S. In other news, I dropped off the face of the Earth over the summer because I’m on the other side of the Earth.  I’m doing research in Japan through the NanoJapan program.  If you’re interested in hearing the cultural experiences of Rice scientists and engineers abroad, might I suggest you go here.

Rice Science in the News

So the other point of Catalyst blog is to detail interesting things going on with science and engineering and several interesting things happened this month within the hedges. I never meant to wait this long, but finals and holidays derailed any hope of nonessential work. So much belatedly, two cool things I’ve been meaning to write about.

First, one of Rice’s own just got major recognition. Dr. James Tour was ranked one of the ten most prolific chemists of the last decade by Times Higher Education.  The ranking was based on how many papers Dr. Tour has published and how often papers he was an author on are cited by other researchers.   With an average 62.76 citations per paper, Dr. Tour’s research is highly regarded.  Much of Dr. Tour’s research focuses on nanotechnology and crosses several disciplines; Tour is mainly a chemistry professor, but is also a professor of computer science and a professor of mechanical engineering and materials science (in fact, many professors who do research in nanotechnology have an additional appointment in materials science if they are from another department).   Nanotechnology seems to be a recurring theme in the Times list.  Counting Dr. Tour, four of the top ten chemists do research in nanotechnology, and another two do work in materials chemistry/science.  Once again, congratulations Dr. Tour. 

From the physics department, we have a surprising but predicted result from the physics department.  Dr. Randy Hulet’s atom cooling group has come up with experimental support for an interesting bit of quantum theory.  In the 1970s, Russian physicist Vitaly Efimov (a professor at the University of Washington) predicted that there could be quantumer trimers: systems where three particles are bound together in a quantum state.  Like the commonly referenced example of Borromean rings, the particles can only be bound if all three are present.   Hulet’s research page says that this happens because the interactions between two particles are so strong that the third particle actually causes the system to achieve a new equilibrium point.  Until this blogger takes quantum mechanics, that’s all I can really say about the nature of the system.  Efimov’s theory has two other interesting consequences.  One is that the trimer can form over a large range of sizes, with the particles ranging from quarks to atoms, and being able to scale all of those orders of magnitudes is pretty impressive in the world of quantum mechanics.  The other cool thing is that the effect repeats itself.  Efimov predicted that if you find a stable trimer, you would find another one by scaling the energy up or down a factor of 22.7… and you could do this forever.  There is no other word to describe this but awesome.

Unfortunately for the theory, experimentalists have had a hard time proving it.  Early work by nuclear physicists failed to find the trimers because the systems had too much kinetic energy from heat.  Using laser cooling, physicists have been able to remove so much energy from the atoms that quantum effects would start to show.   Dr. Hulet’s group used another quantum effect, called Feshbach resonance, to manipulate how cooled lithium atoms would interact with each.  They found the predicted scaling of the trimers and also found a predicted tetramer state of four particles close to each trimer.  In a fitting end to this story, Hulet announced the results at a meeting in Rome that Efimov was also attending.  Efimov, excited for proof of his theory after so long, gave Dr. Hulet a high five after the meeting ended.