New silk materials can wrinkle into detailed patterns, then unwrinkle to be ‘reprinted’

Science Daily  October 7, 2019
Water and methanol vapor, for example, can soak into the fibers and interfere with hydrogen bond cross links in the silk fibroin, causing it to partially ‘unravel’ and release tension in the fiber. Taking advantage of this property, the researchers at Tufts University fabricated a silk surface from dissolved fibroin by depositing it onto a thin plastic membrane (PDMS). After a cycle of heating and cooling the silk surface of the silk/PDMS bilayer folds into nanotextured wrinkles due to the different mechanical properties of the layers. Exposing any part of that wrinkled surface to water or methanol vapor causes the fibers to relax and the wrinkles to flatten. The smooth surface transmits more than 80% of light, while the wrinkled surface only allows 20% or less through, creating a visible contrast and the perception of a printed pattern. Patterns may also be created by depositing water using inkjet printing. They demonstrated printing patterns of very high resolution and the ability to print patterns over at least 50 cycles by erasing the pattern with vapor and recreating patterns…read more. TECHNICAL ARTICLE