Using 3D Printing, Princeton Researched Embed LEDs into Contact Lens

As part of a project demonstrating new 3D printing techniques, Princeton researchers have embedded tiny light-emitting diodes into a standard contact lens, allowing the device to project beams of colored light. Although the technology is experimental, it could conceivably be used to create contact lenses with built-in displays.

Michael McAlpine, the lead researcher, cautioned that the lens is not designed for actual use—for one, it requires an external power supply. Instead, he said the team created the device to demonstrate the ability to “3D print” electronics into complex shapes and materials.

“Where we’re at is a very preliminary stage,” McAlpine told Eye². “Really, what we demonstrated was the implementation of a single LED on a contact lens. The novelty here for us was the use of a 3D printer to accomplish this goal, and in parallel, the use of a 3D scanner to perfectly map the exact topology of the contact lens. This enabled conformal printing of the LED device on the contact lens, by feeding that scanned information into the printer and adjusting accordingly.”

Photo by Frank Wojciechowski

The hard contact lens is made of plastic. The researchers used tiny crystals, called quantum dots, to create the LEDs that generated the 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 McAlpine, who is pictured above holding an LED printed printed on curved glass. “We were able to generate two different colors, orange and green.”

The contact lens is also part of an ongoing effort to use 3D printing to assemble diverse, and often hard-to-combine, materials into functioning devices. In the recent past, a team of Princeton professors including McAlpine created a bionic ear out of living cells with an embedded antenna that could receive radio signals.

In an Oct. 31 article in the journal Nano Letters, lead author Yong Lin Kong said that the contact lens project involved the printing of active electronics using diverse materials. The materials were often mechanically, chemically or thermally incompatible — for example, using heat to shape one material could inadvertently destroy another material in close proximity. The team had to find ways to handle these incompatibilities and also had to develop new methods to print electronics, rather than use the techniques commonly used in the electronics industry.

The researchers were able to custom 3D print electronics on a contact lens by first scanning the lens, and feeding the geometric information back into the printer. This allowed for conformal 3-D printing of an LED on the contact lens.

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