Researchers at the University of Minnesota Twin Cities used a custom printer to fully 3D print a flexible organic light-emitting diode (OLED) display.

Members of the research team, based in the lab of U of M mechanical engineering professor Michael McAlpine, believe their work could lead to relatively inexpensive OLED displays. This breakthrough could potentially aid in the creation of medtech wearables and a host of other devices that rely on digital displays.

OLED display technology converts electricity into light using a layer of organic material. They are popular because they are lightweight, energy efficient, thin and flexible, with wide viewing angle and high contrast ratio.

“OLED displays are typically produced in large, expensive, ultra-clean manufacturing facilities,” McAlpine said in a press release. “We wanted to see if we could condense all of this and print an OLED display on our tabletop 3D printer, which was custom built and costs about the same as a Tesla Model S.”

The research was published in January in the peer-reviewed journal of the American Association for the Advancement of Science Scientists progress newspaper. McAlpine is the lead author of the study; The study’s first author is Ruitao Su, a 2020 U of M. mechanical engineering Ph.D. graduate who is now a postdoctoral fellow at MIT.

In the past, researchers at the University of Minnesota have found it difficult to 3D print OLEDs with uniform light-emitting layers. They say other research groups have partially printed screens, but still needed spin-coating or thermal evaporation to deposit certain components to create functional devices.

The U of M team says they got around the problem by combining two different print modes to fully create the six device layers that make up the OLED. Extrusion printing created the electrodes, interconnects, insulation, and encapsulation; the same room temperature 3D printer used spray printing to create the active layers.

Their method created a 1.5-by-1.5-in. prototype display with 64 pixels that each worked and displayed light.

“I thought I would get something, but maybe not a fully functional screen,” Su said. “But then it turned out that all the pixels worked, and I can display the text that I designed.” My first reaction was, “It’s real! I couldn’t sleep all night.”

The 3D-printed screen was also flexible, according to Su. This means it could be wrapped in encapsulating material and used for a wide variety of applications.

“The device exhibited relatively stable emission over 2,000 bending cycles, suggesting that fully 3D-printed OLEDs can potentially be used for important applications in soft electronics and wearable devices,” said Su. .

The next challenge is to 3D print OLED displays that have higher resolution with improved brightness.

“The good part of our research is that the manufacturing is fully integrated, so we’re not talking about 20 years with a ‘pie-in-the-sky’ vision,” McAlpine said. “It’s something we’ve actually made in the lab, and it’s not hard to imagine you could translate that to printing all sorts of screens ourselves at home or on the go in just a few years, on a small portable printer.”

The University of Minnesota team also included Xia Ouyang, a postdoctoral researcher; Sung Hyun Park, who is now a senior researcher at the 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 NIH’s National Institute for Biomedical Imaging and Bioengineering was the primary funder, with additional support from Boeing and the Minnesota State’s Minnesota Discovery, Research, and InnoVation Economy (MnDRIVE) initiative. .