Who needs Glass when you’ve got contact lenses that can display video and even detect health problems? What’s more, lenses with these capabilities could one day be created using a 3D printer.
Most of today’s 3D printers work with scraps of plastic or metal and turn them into simple objects. But Michael McAlpine at Princeton University and his colleagues have developed a 3D printer that can make a five-layered contact lens, one which emits light into the wearer’s eyes.
The lens is a transparent polymer with several components embedded inside: nanoscale quantum dot light-emitting diodes, wiring made from silver nanoparticles, and organic polymers that could act as parts of electrical circuits.
The trickiest part, McAlpine says, was working out which chemical solvents would deposit each layer best, leaving them dry enough for the next layer to adhere.
Another challenge was the fact that everyone has uniquely shaped eyeballs. The team scanned the contact lens constantly with two cameras to ensure the final shape matched the user’s prescription.
Air Force backing
The work was funded by the US Air Force, which hopes to use such lenses to display in-flight data. Replacing the LEDs with light sensors could also reveal the state of the wearer’s retina and possibly monitor pilot health without invasive implants.
They could also be replaced with sensors that detect chemical biomarkers of fatigue in eye fluids, McAlpine suggests. “Planes have sensors for the state of everything, except the most important thing: the pilot’s exhaustion level,” he says.
Taking the system out of the lab and into the cockpit won’t be easy, however, says physicist Raymond Murray at Imperial College London. He thinks the 3D printed LED display is interesting, but notes that the voltage it needs to switch on is still too high to use in a commercial contact lens.
In addition, the team needs to ensure the devices have no adverse effects on the body – the materials that make quantum dots, such as cadmium selenide, have known health risks.