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JUL/AUG 2013  

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A “bionic” ear and 3-D printing’s promise

Continued laboratory advances hint at how additive manufacturing technology could change the way some electronic devices are made, including a 3-D printed battery and a bionic ear, according to an MIT Technology Review article.

Today’s 3-D printers can generally only build things out of one type of material—usually a plastic or, in certain expensive industrial versions of the machines, a metal. They can’t build objects with electronic, optical, or any kind of functions that require the integration of multiple materials. But recent advances in the research lab—including a 3-D printed battery and a bionic ear—suggest that this might soon change, according to the MIT article.

In June 2013, researchers unveiled what they say is the world’s first 3-D printed battery, made from two different electrode “inks.” Led by Jennifer Lewis, a professor of biologically inspired engineering at Harvard, the group used tiny nozzles to precisely deposit the anode and cathode inks, which contain nanoparticles of lithium titanium oxide and lithium iron phosphate, respectively.

Whereas it may take many years before something as complicated as a smartphone will be printable, certain 3-D printed electronic products might not be too far off. Companies already print the plastic shell that sits in the wearer’s ear cavity. The electronic components are assembled separately, and the devices use small batteries that must be replaced roughly every 7 days. “Imagine if you could 3-D-print the entire hearing aid,” Lewis said. “We can print on curved surfaces.” The electrical components, and a rechargeable battery like the one her group just demonstrated, could thus be additively deposited within the plastic shell.”

Opportunities that result from the ability to precisely deposit electronic or optical materials within 3-D printed objects are not limited to consumer electronics. In May, researchers at Princeton reported using an off-the-shelf 3-D printer to produce a computer-designed ear made of real tissue with interwoven electronics, including a coiled antenna and electrodes composed of a conductive polymer infused with silver nanoparticles. To print tissue, the researchers seeded a jellylike matrix with bovine cells. The matrix gave the printed ear its form as the cells developed into cartilage.

printed electronics

This optical image shows a nozzle with a diameter of 30 micrometers depositing layers of electrode ink.

The researchers admit that the ear, which can detect radio frequencies, serves mainly as a demonstration. But it is nonetheless the first example of this kind of integration of biological tissue and electronics, and suggests a new additive manufacturing-based approach to tissue engineering.

The 3-D printed ear and Lewis’s battery—both produced using printers that extrude material through a nozzle—“open a window to the potential” of additive manufacturing for making things with more than one function, says Richard Hague, director of the EPSRC Center for Innovative Manufacturing in Additive Manufacturing at the University of Nottingham.

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