Researchers at the University of Minnesota Manufacture the First 3D Printed Flexible OLED Display

A team of researchers at the University of Minnesota have created the first 3D printed, flexible organic light-emitting diode (OLED) displays, measuring 3.8 cm by 3.8 cm with 64 pixels. The project is particularly interesting as it is a flexible display that could be used to fold smartphone or TV screens, all at a more affordable cost. Two different additive manufacturing technologies and a custom printer were used to produce it.

Organic light-emitting diodes rely on organic materials to emit light, unlike LCDs which use inorganic crystalline semiconductors. OLEDs are therefore an alternative to LCDs and have several interesting features: better energy efficiency as they do not require backlighting, high contrast ratio, mechanical flexibility, wider viewing angle and better resistance to breakage. However, 3D printing of such diodes has so far presented many challenges. OLED display technology is based on the conversion of electricity into light using a layer of organic material. Creating this layer is difficult because it requires perfect uniformity, which is more complicated to achieve through additive manufacturing. Additionally, polymer-metal bonds made using 3D printing are also more unstable.

An extrusion method and a spray process were used (photo credits: McAlpine Group, University of Minnesota)

Six layers 3D printed to form the OLED display

The team used two 3D printing processes to overcome these challenges and create the six layers of the display. Using an extrusion machine, they created the electrodes, insulation, interconnects and encapsulation. The same 3D printer was then used to create the layers using a spray printing process. Specifically, the layers were successively printed from various materials, depending on the function of the layer in question. For example, the first layer was deposited on a flexible PET film and silver nanoparticles; the fourth layer is a silicone layer covering the underlying conductive materials. Finally, the device was encapsulated with a polymer cast in an extrusion-printed silicone mold.