3D-printer customised to make OLED displays

Researchers at the University of Minnesota Twin Cities believe the discovery could result in low-cost OLED displays in the future that could be widely produced using 3D printers by anyone at home, instead of by technicians in expensive microfabrication facilities.

The OLED display technology is based on the conversion of electricity into light using an organic material layer and are widely used in both large-scale devices such as television screens and monitors as well as handheld electronics such as smartphones.

“OLED displays are usually produced in big, expensive, ultra-clean fabrication facilities,” said Michael McAlpine, 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 group had previously tried 3D printing OLED displays, but they struggled with the uniformity of the light-emitting layers. Other groups partially printed displays but also relied on spin-coating or thermal evaporation to deposit certain components and create functional devices.

The team combined two different modes of printing in order to produce the six device layers needed for the displays.

The electrodes, interconnects, insulation, and encapsulation were all extrusion printed, while 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 worked and displayed light.

“I thought I would get something, but maybe not a fully working display,” said Ruitao Su, first author of the study. “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 and could be packaged in an encapsulating material which makes it possible to be useful in 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 researchers now plan 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.”

In September, South Korean researchers created an ultrathin quantum dot LED variant that can be folded as freely as paper into various 3D structures such as butterflies, aeroplanes and pyramids.