Erasing wrinkles, without injection: studies reveal nature's tricks for smoothing deformations.
Physicists have figured out how wrinkles erase themselves naturally--no Botox needed. But Joan Rivers shouldn't visit the lab just yet. These wrinkles appear not on skin, but on thin sheets of polymers.
In a pair of papers published online July 14 in Physical Review Letters, scientists report how sharp folds make a transition to smoother wrinkles, and how wrinkles themselves vanish toward the edges.
On a basic level, the research describes the math behind everyday experiences of wrinkles, everywhere from the surface of pudding to a poorly made bed. "These are things you see everywhere, in beautiful and amazing deformation," says materials scientist Douglas Holmes of Princeton University, coauthor of one of the studies.
More practically, such insights could one day improve technologies that incorporate thin films, like flexible solar panels or tissues grown for biological uses.
In one study, a team led by Jiangshui Huang of the University of Massachusetts Amherst tackled how wrinkles smooth out toward the edge of an elastic sheet.
Imagine cramming a corrugated sheet edge-to-edge against a smooth one. One way the sheets can accommodate the incompatibility is for the corrugated one to develop a series of sharp, branching folds along its edge. But when Huang floated a thin, wrinkly sheet of polystyrene on water and butted it up against a smooth one, more and more tiny wrinkles appeared toward the edge to accommodate the difference between the sheets.
Similar elastic films, from shrink-wrap to skin to biomembranes, should exhibit the same sort of smooth cascade.
In the second study, another Amherst team mapped out how sharp folds fade into smooth wrinkles when a sheet is pinched in one spot and pulled up, like pulling a tissue out of a box.
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|Title Annotation:||Matter & Energy; creases from thin sheets of polymers|
|Article Type:||Brief article|
|Date:||Aug 14, 2010|
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