11-06/07 :: June/July 2011

nanotimes News in Brief

59

Nanomechanical measurements (model sys- tem and microimage of typical specimen).

a) thin rigid film on elastic substrate b) initial strain induces surface wrinkles parallel to stress

c) additional strain induces regular pattern of cracks in the film

d) typical specimen imaged with optical profilometer (280 X 210 µm.)

© Chung, Lee/NIST

few hours. Tests using the wrinkle-crack method, however, show that the mechanical properties degrade con- tinuously – the material becoming more and more stiff, brittle and weak – up to the longest duration tested, 10 days. “It may be an aging effect in polymers,” says Stafford. “We‘re continuing to study that to figure out what‘s going on in there, because it‘s a real measurement challenge to get in on that length scale to follow the structure over time.”

J.Y. Chung, J.-H. Lee, K.L. Beers and C.M. Stafford: Stiffness, strength, and ductility of nanoscale thin films and membranes – A combined wrinkling-cracking methodology, In: Nano Letters ASAP, July 15, 2011, DOI:10.1021/nl201764b: http://dx.doi.org/10.1021/nl201764b