#wrinkling

Scientists Iron Out the Physics of Wrinkling

Researchers combine experiments and theory to determine how curved edges affect the wrinkling of ultra-thin materials.

When we think of wrinkles, we usually envision the lines etched into our skin, for some an unwelcome reality and for others a proud sign of a life well-lived. In material science, wrinkles can also be either wanted or unwanted. But the physical factors that cause wrinkling to occur are not yet fully understood.

Now, in a paper recently published in Applied Physics Letters, researchers from the Mathematics, Mechanics, and Materials (MMM) Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) have shown how wrinkles can be increased or reduced by altering the curvature at the edge of a material.

“Historically, scientists and engineers have focused on preventing wrinkling, which can adversely affect the performance of pressure sensors, aircraft panels, and lightweight spacecraft structures including deployable space booms and telescopes,” said Professor Eliot Fried, who leads the MMM unit. “But recent research has also shown that wrinkling can give materials useful properties. For example, it can be used to make a material super hydrophobic or to make coatings that reflect light in unique ways.”

Fabric Manipulation Techniques - Indigo & Violet 

A thread of mineral oil laid across a pool of water twists and turns like a river run wild. Because the oil has a lower surface tension than the water, Marangoni forces spread it outward (far left). Small variations in the thread make the areas of highest oil concentration start to bend just a bit. Inside the bends, the gradient of surface tension -- the difference between the lowest and highest surface tensions -- is very high, which pulls at these regions more than others. So bends beget more bends, causing the entire thread to wrinkle. Although the behavior is driven by a completely different process than the one that causes rivers to meander, the end result looks remarkably similar; this is because, in both cases, forces act to make each bend increasingly sinuous. (Image credit: B. Néel et al., source)