The Key to Better Wearables: Liquid, Printable Metal

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Black ink drips from a printing machine at the El Pais printing plant in Madrid, Spain, on Tuesday, Oct. 30, 2012. Prisa, the publisher of El Pais newspaper, has announced staff reductions and salary cuts. Photographer: Angel Navarrete/Bloomberg via Getty Images
Black ink drips from a printing machine at the El Pais printing plant in Madrid, Spain, on Tuesday, Oct. 30, 2012. Prisa, the publisher of El Pais newspaper, has announced staff reductions and salary cuts. Photographer: Angel Navarrete/Bloomberg via Getty Images Photo: Angel Navarrete/Bloomberg via Getty Images

A team of Purdue University researchers have figured out how to run liquid metal through an inkjet printer, leading to a process that can place electronic circuitry on anything you can imagine. Rebecca Kramer, a mechanical-engineering professor at Purdue, is imagining “robots that need to squeeze through small spaces, or wearable technologies that aren't restrictive of motion.” Think of a glove printed with the circuitry that allows it to interact with your computer, but feels no different from any other glove. That’s the promise this technology holds.

The key to the new manufacturing process is using ultrasound to break up a liquid metal in a solvent, in this case ethanol. With the liquid metal dispersed in the solvent, it will pass through the tiny nozzle on an inkjet printer. Upon printing, the ethanol evaporates and you’re left with a layer of liquid metal nanoparticles on whatever surface you’ve chosen.

There's one more step to the process. After printing, the nanoparticles are covered in a thin skin. This skin must be broken before the liquid metal will conduct electricity, and that’s easily done “by stamping or by dragging something across the surface,” Kramer says in a release from the university. It sounds like a drawback, but it may make this process even more useful than originally thought, by simplifying mass production. Giant printers could create sheets of nanoparticle-covered materials, which could be selectively activated based on the electron functions desired.