Researchers develop 3D print light-emitting contact lens

Researchers have created a way to integrate tiny electronics directly into 3D printed objects, for this project they embedded LEDs into a contact lens allowing it to beam colored light. 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.  

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. “This shows that we can use 3D printing to create complex electronics including semiconductors,“ said McAlpine, an assistant professor of mechanical and aerospace engineering.

“We were able to 3D print an entire device, in this case an LED.” 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,” McAlpine said. “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.  

Yong Lin Kong, a researcher on both projects, said the bionic ear presented a different type of challenge. “The main focus of the bionic ear project was to demonstrate the merger of electronics and biological materials,” said Kong.Kong, the lead author of the article describing the current work in the journal Nano Letters, said that the contact lens project, on the other hand, 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 the electronics.  

“For example, it is not trivial to pattern a thin and uniform coating of nanoparticles and polymers without the involvement of conventional microfabrication techniques, yet the thickness and uniformity of the printed films are two of the critical parameters that determine the performance and yield of the printed active device,“ Kong said.

To solve these challenges, they collaborated with Ian Tamargo, Hyoungsoo Kim and Barry Rand. McAlpine said that one of 3D printing’s greatest strengths is its ability to create electronics in complex forms. Unlike traditional manufacturing, which builds circuits in flat assemblies and then stacks them into three dimensions, 3D printers can create vertical structures as easily.“In this case, we had a cube of LEDs,” he said. “Some of the wiring was vertical and some was horizontal.”  


To conduct the research, the team built a new type of 3D printer that McAlpine described as “somewhere between off-the-shelf and really fancy.” Dan Steingart, who helped design and build the new printer, which McAlpine estimated cost around $20,000.McAlpine said that he does not envision 3D printing replacing traditional manufacturing in electronics any time soon; instead, they are complementary technologies with very different strengths.

Prime uses for 3D printing are situations that demand flexibility and that need to be tailored to a specific use. For example, conventional manufacturing techniques are not practical for medical devices that need to be fit to a patient’s particular shape or devices that require the blending of unusual materials in customized ways.

“Trying to print a cellphone is probably not the way to go,” McAlpine said.“It is customization that gives the power to 3D printing.” In this case, they 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.


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