Tech

A carbon membrane only a single atom thick has been used to create a pressurised "balloon" that is impermeable to gas.

To make it, researchers at Cornell University in Ithaca, New York inflated a sheet of graphene. This is a recently discovered carbon material just one atom thick, and is tipped to succeed silicon as the basis of computing.

They created the sheets of graphene using a low-tech process dubbed "mechanical exfoliation" - using sticky tape to peel layers from a chunk of graphite.

The sheets were used to seal microscopic wells made in a layer of silica glass, forming a kind of drum head. The membranes were held in place only by the van der Waals forces that make things sticky at microscopic scales. The wells varied from 1 to 100 square micrometers in area and 250 nanometres to 3 micrometers deep.

To see how well the graphene could hold in gas, the researchers altered the pressure inside, making the graphene membranes bulge outward or inward.

Leak free

The membranes were able to withstand pressure differences of up to several atmospheres before being dislodged. But as long as the seal remained, the graphene was completely impermeable.

Gas did leak in or out over several days, but the researchers discovered that it was leaving through the glass, not the membranes.

By measuring exactly how much the graphene bulged under a specific pressure, the researchers were able to calculate its elasticity, which turns out to be the same as that of normal graphite.

They also used a laser to vibrate the membrane and measure its resonance frequency, which provides a way to calculate the exact mass of the graphene.

Paul McEuen, a physicist at Cornell and a co-author of the paper, says that process means the setup could be used as a tiny weighing device. Graphene balloons could also be used as tiny pressure sensors, he adds.

Promising material

James Hone, a physicist at Columbia University in New York, calls inflating the tiny balloons "very nice work".

Hone thinks graphene clearly has more to offer than just its impressive electronic properties. "I think what we're learning from all these measurements is that graphene really does live up to its promise as a mechanical material. It really does outperform by orders of magnitude anything out there," he says.

Journal reference: Nano Letters (DOI: 10.1021/nl801457b)

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.