Imagine a thin, digital display so flexible that you can wrap it around your wrist, fold it in any direction, or curve it over your car’s steering wheel. Researchers at the Pritzker School of Molecular Engineering (PME) at the University of Chicago have designed just such a material, which can bend in half or stretch to more than twice its original length while still emitting a fluorescent pattern.
The material, described in Nature Materials, has a wide range of applications, from wearable electronics and health sensors to foldable computer screens.
“One of the most important components of nearly every consumer electronic we use today is a display, and we’ve combined knowledge from many different fields to create an entirely new display technology,” said Sihong Wang, assistant professor of molecular engineering, who led the research with Juan de Pablo, Liew Family Professor of Molecular Engineering.
“This is the class of material you need to finally be able to develop truly flexible screens,” added de Pablo. “This work is really foundational and I expect it to allow many technologies that we haven’t even thought of yet.”
Making flexible, light-up polymers
The displays on most high-end smartphones, as well as a growing number of televisions, use OLED (organic light-emitting diode) technology, which sandwiches small organic molecules between conductors. When an electrical current is switched on, the small molecules emit a bright light. The technology is more energy-efficient than older LED and LCD displays and praised for its sharp pictures. However, the molecular building blocks of OLEDs have tight chemical bonds and stiff structures.
“The materials currently used in these state-of-the-art OLED displays are very brittle; they don’t have any stretchability,” said Wang. “Our goal was to create something that maintained the electroluminescence of OLED but with stretchable polymers.”
Wang and de Pablo knew what it takes to imbue stretchability into materials—long polymers with bendable molecular chains—and also knew what molecular structures were required for an organic material to emit light very efficiently. They set out to create new polymers that integrated both properties.
“We have been able to develop atomic models of the new polymers of interest and, with these models, we simulated what happens to these molecules when you pull on them and try to bend them,” explained de Pablo. “Now that we understand these properties at a molecular level, we have a framework to engineer new materials where flexibility and luminescence are optimized.”
—Prof. Jacqueline Stewart
