3D printing can be used to assemble hard-to-combine materials into functioning devices, such as complex electronics made from nanoparticles.
In a demonstration by Princeton research engineers, electronics were 3D printed in a plastic contact lens. The project started with the design and construction of a custom 3D printer at an estimated cost of about $20,000. The researchers then printed tiny crystals, called quantum dots, to create LEDs that generate colored light. Different size dots can be used to generate various colors.
“We used the quantum dots [also known as nanoparticles] as an ink,” said Michael
McAlpine, an assistant professor of mechanical and aerospace engineering at Princeton, who was in charge of the research team. “We were able to generate two different colors, orange and green.”
In all, five materials are printed: (1) emissive semiconducting inorganic nanoparticles, (2) an elastomeric matrix, (3) organic polymers as charge transport layers, (4) solid and liquid metal leads, and (5) a UV-adhesive transparent substrate layer. A contact lens was used for the demonstration to show that the materials could be conformally printed on a curved surface. Most electronics ae manufactured on flat surfaces.
Printing LED lights inside a contact lens serves no practical purpose; it was strictly a demonstration. There was no power source in the lens for the lights. The Princeton project is believed to be one of the first projects involving 3D printing of active electronics. 3D printing generally has been limited to specific plastics, passive conductors, and a few biological materials.
Financial support for the project came from the Air Force Office of Scientific Research and the Defense Advanced Research Projects Agency.