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" to quantify the adhesion between graphene and glass plates.
Adhesion energy describes how "sticky" two things are when placed together. Scotch tape is one example of a material with high adhesion; the gecko lizard, which seemingly defies gravity by scaling up vertical walls using adhesion between its feet and the wall, is another. Adhesion also canplay a detrimental role, as in suspended micromechanical structures where adhesion can cause device failure or prolong the development of a technology, said Bunch.
The CU research, the first direct experimental measurements of the adhesion of graphene nanostructures, showed that so-called "van der Waals forces" -- 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 multilayer 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, said Bunch.
The CU-Boulder study was funded primarily by the National Science Foundation and the Defense Advanced Research Projects Agency.
The importance of graphene in the scientific world was illustrated by the 2010 Nobel Prize in physics that honored two scientists at Manchester University in England, Andre K. Geim and Konstantin Novoselov, for producing, isolating, identifying and characterizing graphene.
There is interest in exploiting graphene's incredible mechanical properties to create ultrathin membranes for energy-efficient separations such as those needed for natural gas processing or water purif
|Contact: Scott Bunch|
University of Colorado at Boulder