Using three-dimensional printing, designers can make highly customized products, including shoe soles, engine parts, and some wearable electronics such as hearing aids. But when designers want to make new personal electronics, their imaginations are limited by the shapes of existing batteries, such as coin shapes, rectangles, cylinders, and pouches. Harvard University materials scientist Jennifer Lewis, who specializes in materials and methods for 3-D printing, wants to make it possible for batteries to be designed around the electronics they will power, not vice versa.
She and her colleagues now have combined 3-D printing and other techniques to make batteries in any arbitrary shape. They constructed multiple kinds of batteries, including rechargable zinc-ion ones, in the shapes of rings, letters, circles, and more (ACS Nano 2018, DOI: 10.1021/acsnano.8b02744).
In 2013, Lewis’ lab was the first to make 3-D printed batteries using lithium-ion chemistry (Adv. Mat. 2013, DOI: 10.1002/adma.201301036). Because the materials in these batteries are water-sensitive and flammable, she says, they had to do all their work in a glovebox filled with inert gas. These manufacturing limitations made it difficult to move beyond the initial demonstration of small batteries printed on chips in the lab.
Lewis collaborated with Korea Advanced Institute of Science and Technology nanomaterials scientist Il-Doo Kim, to work on other battery chemistries, chiefly zinc-ion, which uses water-based electrolytes and is easier to toy around with in open air. They decided to “go with a chemistry we don’t have to worry about,” Lewis says.
The team integrated several manufacturing methods to make these batteries. For example, they used electrospinning to make a cathode that could be cut to any desired shape, and laser micromachining to make other battery parts. Finally, Lewis and colleagues used stereolithography to print packages for the batteries in desired shapes, and applied methods she developed previously for 3-D printing metals to make electrical connections in the batteries.
The researchers constructed a battery in the shape of a ring, and used 3-D printing to fabricate a simple light sensor on top of it. The set of methods works for customizing other kinds of energy storage devices, Lewis says, including graphene supercapacitors and zinc-manganese dioxide batteries.
The zinc-ion batteries can discharge and recharge quickly,says Sang-Young Lee, a battery chemist at Ulsan National Institute of Science & Technology. Kim says this is due to the high surface area of the electrospun cathodes, which are made of carbon nanofibers coated with polyaniline, a porous conductive polymer. The battery recharges in just a few minutes, he says.
It’s hard to predict just what designers will make when freed from the constraints of conventional batteries, Lewis says, though she imagines niche applications such as personalized, wearable, and implantable medical devices. “This work is meant to be provocative,” she says.
CORRECTION: On Nov. 15, 2018, the scale bar on the photograph of printed batteries was corrected.