By Chris Newmarker

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

The research team members — based at U of M mechanical engineering professor Michael McAlpine’s lab — think their work could result in relatively low-cost OLED displays. The advance could potentially aid the creation of medtech wearables and a host of other devices that rely on digital displays.

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

“OLED displays are usually produced in big, expensive, ultra-clean fabrication facilities,” McAlpine said in a news release. “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 research was published in January in the American Association for the Advancement of Science’s peer-reviewed Science Advances journal. McAlpine is the study’s senior author; the study’s first author is Ruitao Su, a 2020 U of M mechanical engineering Ph.D. graduate who is now a postdoctoral researcher at MIT.

The University of Minnesota researchers in the past found it challenging to 3D print OLEDs with uniform light-emitting layers. They say other research groups partially printed displays, but they 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 printing modes to fully create the six device layers that made up the OLED. Extrusion printing created the electrodes, interconnects, insulation and encapsulation; the same 3D printer at room temperature used spray printing to create the active layers.

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

“I thought I would get something, but maybe not a fully working display,” Su said. “But then it turns out all the pixels were working, and I can display the text I designed. My first reaction was, ‘It is real!’ I was not able to sleep the whole night.”

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

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

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

“The nice part about our research is that the manufacturing is all built-in, so we’re not talking 20 years out with some ‘pie-in-the-sky’ vision,” McAlpine said. “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.”

The University of Minnesota team also included 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 NIH’s National Institute of Biomedical Imaging and Bioengineering was the primary funder, with additional support from Boeing and the state of Minnesota’s Minnesota Discovery, Research, and InnoVation Economy (MnDRIVE) initiative.