Scott Bunch sheds new light on adhesion qualities of graphene

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The most exciting new material under study in the world of nanotechnology -- graphene -- just got even more exciting.

Consisting of a single layer of carbon atoms chemically bonded in a hexagonal chicken wire lattice, graphene represents a unique atomic structure that could someday replace silicon as the basis of electronic devices and integrated circuits because of its remarkable electrical, mechanical, and thermal properties.

Not only does  graphene have the highest electrical and thermal conductivity among all materials known, but this “wonder material” has been shown to be the thinnest, stiffest, and strongest material in the world, as well as being impermeable to all standard gases. We can now add adhesion to graphene’s list of seemingly contradictory qualities, according to the latest experimental results from CU- Boulder Professor Scott Bunch and his colleagues.

In the paper, “Ultrastrong adhesion of graphene membranes,” published online in Nature Nanotechnology,  graduate students Steven Koenig and Narasimha Boddeti, along with professors Martin Dunn and Scott Bunch, report that the extreme flexibility of  graphene  allows it to conform to the topgraphy of even the smoothest substrates.

“The real excitement for me is the possibility of creating new applications that exploit the remarkable flexibility and adhesive characteristics of graphene and devising unique experiment that can teach us more about the nanoscale properties of this amazing material,” Bunch said.

The CU-Boulder team measured the adhesion energy of graphene sheets, ranging from one to five atomic layers, with a glass substrate, using a pressurized blister test.  The experiments, which are the first direct experimental measurements of the adhesion of graphene nanostructures, showed that  “van der Waals forces,” defined as the sum of the attractive or repulsive forces between molecules, clamp the graphene samples to the substrates and also hold together the individual graphene sheets in multi-layer samples.

The researchers found the adhesion energies between graphene and the glass substrate were several orders of magnitude larger than adhesion energies in typical micromechanical structures, an interaction they described as more liquid-like than solid-like.

The new findings will help to guide the development of graphene manufacturing and of graphene-based mechanical devices such as resonators and gas separation membranes. 

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