PROVIDENCE, R.I. -- Wrinkles and folds are ubiquitous. They occur in furrowed brows, planetary topology, the surface of the human brain, even the bottom of a gecko's foot. In many cases, they are nature's ingenious way of packing more surface area into a limited space. Scientists, mimicking nature, have long sought to manipulate surfaces to create wrinkles and folds to make smaller, more flexible electronic devices, fluid-carrying nanochannels or even printable cell phones and computers.
But to attain those technology-bending feats, scientists must fully understand the profile and performance of wrinkles and folds at the nanoscale, dimensions 1/50,000th the thickness of a human hair. In a series of observations and experiments, engineers at Brown University and in Korea have discovered unusual properties in wrinkles and folds at the nanoscale. The researchers report that wrinkles created on super-thin films have hidden long waves that lengthen even when the film is compressed. The team also discovered that when folds are formed in such films, closed nanochannels appear below the surface, like thousands of super-tiny pipes.
"Wrinkles are everywhere in science," said Kyung-Suk Kim, professor of engineering at Brown and corresponding author of the paper published in the journal Proceedings of the Royal Society A. "But they hold certain secrets. With this study, we have found mathematically how the wrinkle spacings of a thin sheet are determined on a largely deformed soft substrate and how the wrinkles evolve into regular folds."
Wrinkles are made when a thin stiff sheet is buckled on a soft foundation or in a soft surrounding. They are precursors of regular folds: When the sheet is compressed enough, the wrinkles are so closely spaced that they form folds. The folds are interesting to manufacturers, because they can fit a large surface area of a sheet in a finite space.
Kim and his team laid gold nanogranular film sheets ran
|Contact: Richard Lewis|