An interdisciplinary team of engineers at Princeton University has embedded tiny light-emitting diodes (LEDs) into a standard contact lens, allowing the device to project beams of colored light. While the lens is not designed for actual use, especially since it requires an external power supply, the team created the device to demonstrate its ability to 3D print electronics into complex shapes and materials.
The hard plastic contact lens was embedded with tiny crystals, called quantum dots, to create the LEDs that generated the colored light. They used the quantum dots as an ink, and said that they were able to generate two different colors—orange and green.
The contact lens project involved printing of active electronics using diverse materials, which were often mechanically, chemically, or thermally incompatible. For example, using heat to shape one material could inadvertently destroy another material in close proximity, they said. Their challenge was to find ways to handle these incompatibilities and also had to develop new methods to print electronics.
Unlike traditional electronics manufacturing, which builds circuits in flat assemblies and then stacks them into three dimensions, 3D printers can create vertical structures as easily as horizontal ones. In this case, the researchers created a cube of LEDs with some of the wiring vertical and some horizontal.
In addition, the team built a new type of 3D printer, which they estimated cost about $20,000 but will be very useful for situations that demand flexibility and must be tailored to a specific use, as well as devices that require the blending of unusual materials in customized ways.
In this case, the researchers were able to custom 3-D print electronics on a contact lens by first scanning the lens, and feeding the geometric information back into the printer. This allowed for conformal 3D printing of an LED on the contact lens.