The material, developed at the Pritzker School of Molecular Engineering (PME) at the University of Chicago and described in Nature Materials, has applications ranging 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,” de Pablo said in a statement. “This work is really foundational, and I expect it to allow many technologies that we haven’t even thought of yet.”
The displays on most high-end smartphones, plus 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 molecules emit a bright light. The technology is more energy-efficient than LED and LCD displays and delivers sharp pictures, but 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.”
“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,” said 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 optimised.”
A key feature in their design was the use of “thermally activated delayed fluorescence,” which let the materials convert electrical energy into light in a highly efficient way. This third-generation mechanism for organic emitters can provide materials with performance on par with commercial OLED technologies, the researchers claim.
As well as being used to display information, bendable materials can be integrated into wearable sensors that require light, said Wang.
Wang said a bendable light-up material also could eventually be integrated into implantable devices, including those that use light to control the activity of neurons in the brain.
“My overall dream is to make all the essential components for a full system of wearable electronics, from sensing to processing to displaying information,” said Wang. “Having this stretchable light-emitting material is another step toward that dream.”
The team is planning to develop new iterations of the display, integrating additional colours into the fluorescence and improving the efficiency and performance.