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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