Although the lure of using 3-D printing technology to create electronic components is great, the challenges are perhaps greater. Nevertheless, when asking the question earlier this year what's next for 3-D printing, our answer was: printable electronics.

Now, researchers at Princeton University have succeeded in embedding tiny LEDs into a standard plastic-based contact lens. The team's objective was to prove that 3-D printing can be used to produce electronics featuring complex shapes and materials. Although the new device is not designed for actual use, lead researcher Michael McAlpine, an assistant professor of mechanical and aerospace engineering, believes that its creation opens the road to producing such complex electronics as semiconductors.

The new device consists of a hard-plastic contact lens substrate and tiny crystals known as quantum dots or nanoparticles. Used to create the LEDs, these dots are of different sizes and thus capable of generating a range of different colors.

Describing this work in Nano Letters, researcher Yong Lin Kong noted that the contact lens project involved printing active electronics using diverse materials. The problem is that these materials were often mechanically, chemically, or thermally incompatible. To overcome this obstacle, the team learned how to manage these incompatibilities and develop new methods for printing 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 stated in a Princeton University press release.

3-D printing's greatest strength is its ability to create electronics in complex forms, McAlpine explains. While traditional electronics manufacturing builds circuits in flat assemblies and then stacks them into three dimensions, 3-D printing can create vertical structures as easily as horizontal ones. "In this case," he says, "we had a cube of LEDs. Some of the wiring was vertical and some was horizontal."

The power of 3-D printing resides in is its ability to produce custom devices for specific uses, McAlpine adds. This includes medical devices tailored to a patient's shape or those that must blend unusual materials in customized ways. For example, in the case of the contact lens/LED device, the researchers created custom electronics by first scanning the lens and then feeding the geometric information back into the 3-D printer, enabling conformal 3-D printing of the LED on the plastic lens.
 

Bob Michaels is senior technical editor at UBM Canon.

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