Airtight containers are not always so airtight. As any child will discover the day after a birthday party, even a tightly tied helium balloon will leak out its gas over the course of many hours. Now scientists have come up with a supremely efficient barrier that lets nothing in or out.
The new type of wrapping material is made of graphene, a natural carbon fabric that is only a single-atomic-layer thick, so thin that sheets of graphene can only be seen with a microscope.
A related and more familiar form of carbon, graphite, is used in pencils. At the microscopic level, graphite consists of billions of two-dimensional sheets of carbon atoms. The fact that these sheets are only loosely attached to each other is what makes graphite such a good lubricant. Graphene is what you get when you take the layers of graphite one at a time. Little slivers of graphene -- imagine chicken wire made of carbon atoms -- were discovered for the first time only a few years ago when physicists picked them off of a piece of graphite.
Now, because of graphene’s interesting properties -- such as the fact that electrons flow through it without much energy loss -- it has become a hot topic among physicists. One of the most impressive properties is its mechanical strength, which is surprising since it is so thin.
Both experiments in the lab and simulations carried out with a computer have now shown that graphene sheets can sustain high pressure and act as ideal containers, and physicists at the University of Antwerp in Belgium have studied how graphene sheets can hold gases within a tiny balloon.
If any atom could escape from a nanoscopic bag it would be helium, the second lightest element in the universe with properties that make it difficult to contain. But, according to Antwerp researcher Ortwin Leenaerts, even helium is unable to escape his atomically thin enclosure. He and his colleagues published their findings in the journal Applied Physics Letters.
An experiment at Cornell University in Ithaca, New York, in the laboratory of Harold Craighead, with a sheet of graphene stretched across a tiny bottle holding gas, has shown that even high-pressure gas is kept in. The work by Craighead's team appeared in the journal Nano Letters.
Leenaerts says that graphene, aside from its electrical properties, can contribute to a number of nanotech products. Examples include tiny pressure sensors: depending on the pressure of a gas in a tiny bottle, the graphene “stopper” of such a bottle would vibrate at telltale frequencies. A tiny patch of graphene could serve as a nanoresonator: clamped on two sides, the graphene would vibrate at radio frequencies. An electrical signal could be sent in, causing the graphene to act as a tiny radio antenna. Graphene might even be used as an artificial membrane. Formed into something like an artificial cell, the graphene could contain medicine that might be released in the body.
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