A thin polymer film with an annular shape that is floating on water. As the surface tension pulling on the outer edge is lowered, the sheet forms wrinkles and then two folds. The sheet is 394 nm thick and 16 mm wide.

Wrinkles are all around us — on hanging curtains, the skin of drying fruit, or a surprised forehead. The more a material is squished, the deeper and taller the wrinkles become, until they collapse into a fold. Typically, this process depends strongly on the materials in question, for example the thickness of the skin, or the softness of the flesh underneath. However, we show that a wrinkle-to-fold transition may be affected only by the shape of the compressed object, rather than by any mechanical properties! Continue reading “Geometry-driven folding in PRL”