University 3D prints first flexible OLED

In a groundbreaking new study, researchers at the University of Minnesota Twin Cities used a customized printer to fully 3D print a flexible organic light-emitting diode display, a discovery that could result in anyone being able to 3D print low-cost OLED displays at home.

OLED display technology is based on converting electricity into light using an organic material layer. Functioning as high-quality digital displays – often made flexible and in both large-scale devices such as televisions and monitors as well as handheld electronics such as smartphones – OLED displays have gained popularity due to their lightweight, power-efficient, thin and flexible, and wide viewing angle and high contrast ratio.

"OLED displays are usually produced in big, expensive, ultra-clean fabrication facilities," said Michael McAlpine, a University of Minnesota Kuhrmeyer Family Chair Professor in the Department of Mechanical Engineering and the senior author of the study. "We wanted to see if we could basically condense all of that down and print an OLED display on our table-top 3D printer, which was custom built and costs about the same as a Tesla Model S."

The team had previously tried 3D printing OLED displays, but they struggled with the uniformity of the light-emitting layers. Likewise, other groups have partially printed displays and relied on methods such as spin-coating or thermal evaporation to deposit specific components and create functional devices.

In this new study, however, the research team combined two different modes of printing to create six device layers that resulted in a fully 3D-printed, flexible organic light-emitting diode display.

The electrodes, interconnects, insulation, and encapsulation were all extrusion printed (squeezed out like frosting in a piping tip). In contrast, the active layers were spray printed using the same 3D printer at room temperature.

The display prototype was about 1.5 inches on each side and had 64 pixels – every pixel was functional and could display light.

"I thought I would get something, but maybe not a fully working display," said Ruitao Su, the first author of the study and a 2020 University of Minnesota mechanical engineering Ph.D. graduate who is now a postdoctoral researcher at MIT. "This is something that we actually manufactured in the lab, and it is not hard to imagine that you could translate this to printing all kinds of displays ourselves at home or on the go within just a few years, on a small portable printer."

In addition to McAlpine and Su, the research team included University of Minnesota mechanical engineering scientists Xia Ouyang, a postdoctoral researcher; Sung Hyun Park, who is now a senior researcher at Korea Institute of Industrial Technology; and Song Ih Ahn, who is now an assistant professor of mechanical engineering at Pusan National University in Korea.

The research is published in "Science Advances," a peer-reviewed scientific journal published by the American Association for the Advancement of Science.