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Think small December 1, 2007

A remarkably simple experiment devised by scientists yields important information about the mechanical properties of thin films (nanoscopically thin layers of material that are deposited onto a metal, ceramic or semiconductor base)

The findings impact a broad range of scientific disciplines and applications, from cosmetics to coatings, to micro- and nanoelectronics, filters, very low loss high density optical films etc. Understanding the mechanical properties of thin films is essential to their performance and optimization.

Until now, determining the mechanical properties of these thin films was either an expensive and time-consuming endeavor, requiring powerful microscopes to view the films, or scientists examined composite structures and made uncertain assumptions. This new research will give scientists a simple way to access the material properties of most thin films. Low-power optical microscope is used to observe what happens when they place a tiny drop of water on thin film as it floats in a Petri dish of water. The capillary tension of the drop of water produces a starburst of wrinkles in the film. The number and length of the wrinkles are determined by the elasticity and thickness of the film.

In some of the materials studied, the wrinkles in the ultrathin polymer films vanished with time. This vanishing provides insight into the relaxation process of an ultrathin film by yielding information on the way polymer chains move in the highly confined geometry.

Source: NSF