It seems like you can 3D-print pretty much anything these days. We’ve seen 3D-printed cars, 3D-printed handguns, and even a custom-assembled mechanical computer made from 3D-printed parts. But deep in Harvard’s research labs, a team is working hard on a 3D printing project that has the potential to change mobile devices as we know it: a fully operational, incredibly small, 3D-printed battery. And when we say small, we mean really small: the battery is about the size of a grain of sand and thinner than a human hair.
We spoke to Jennifer Lewis, the Hansjörg Wyss Professor of Biologically Inspired Engineering at the Harvard School of Engineering and Applied Sciences, and a core team member responsible for the creation of one of the world’s first 3D-printed batteries, about the potential uses for this printed power source and how 3D printing is changing the future of technology.
Small battery, big power potential
Lewis and her team at Harvard recognized the need for a small, customizable power source, specifically one that could be used to unlock new miniaturized technologies. “The proliferation of microscale devices such as micro-electro-mechanical systems (MEMS), biomedical sensors, wireless sensors, and actuators requires the development of new batteries whose size and shape can be tailored to fit small devices,” Lewis said. “We knew that our research group’s 3D printing expertise could play a key role in the development of this next generation of batteries.”
It’s similar to a cell phone battery, except that it is about 15,000 times smaller.
The battery produces around the same power per volume as a lithium phone battery. However, they’re obviously much smaller than standard phone batteries. “The power produced by our 3D-printed batteries could certainly be increased by simply printing larger batteries,” Lewis said. So a “grain-sized” battery isn’t capable of powering a phone, or anything bigger than a grain of sand for that matter, but, it could power a phone if a larger size was printed.
Not your average 3D printer
Clearly, you can’t just go out and print this type of battery with your Makerbot Replicator 2X. The team used a custom positioning system from Aerotech that’s capable of positioning the printing nozzle with a precision of 50 nanometers (2 millionths of an inch). “This is the most precise 3D printer we have in our lab, and it was the printer’s high degree of precision that allowed us to print such small features in our battery,” Lewis said.
But you can’t just toss together a battery out of plastic either. The team introduced specialized ink in order to give the tiny cell its charge. How do you just “print power?” The answer lies in a specialized lithium metal oxide and cathode ink. “The anode and cathode are two essential components in a lithium-ion battery, because those materials largely govern the charging and discharging processes,” Lewis said. “Our choice of materials plays a large role in determining the cell voltage, energy and power densities, and lifetime of the printed battery.”
The reason why the inks require specialized engineering is twofold: cell performance and flow behavior. Lewis explained that for cell performance, they needed to pack as much active material (lithium metal oxide) in the ink per volume so that maximum energy and power densities in volume can be achieved. “However, we have to balance increased solids loading with that ability of the ink to still flow through the fine 30 micron nozzles.”
Besides having the capability to power a cell phone, Lewis told us these batteries could be mass-produced, and would be especially useful in applications that require individualized customization of the shape and size of the battery, like hearing aids, for example. “Hearing aids are customized to specifically fit each patient’s ears, and these batteries could be customized to specifically fit in each customized hearing aid,” Lewis said.
The materials used to produce a single battery cost about a fifth of a cent per battery.
It isn’t just miniaturized technologies either. Lewis told us that it’s possible to print a larger battery. Does that mean it’s possible to print a laptop battery? “We can 3D-print larger batteries for those types of applications – however, the battery performance would be comparable to existing commercial Li-ion batteries – at least for our first generation design,” Lewis said.
We’d love to see a fully functional laptop battery just “printed,” and according to Lewis, the process to create these batteries is both inexpensive and fairly quick. “The printing time for each battery is only four minutes,” Lewis said. “The materials used to produce a single battery cost about a fifth of a cent per battery.”
The future of printable batteries
This is the first battery of its kind, but that doesn’t mean it’s the last. The Harvard group’s creation provides a blueprint that can easily be upgraded and customized to fit in a variety of situations. “We’d like to continue to optimize the materials used for the anode and cathode inks in order to further increase the performance of the printed batteries, as well as improve the way in which these batteries are packaged,” Lewis said. It’ll be interesting to see if any manufacturers jump on board with this newly discovered tech in the future and attempt to make use of this game-changing discovery.
Photos courtesy of Harvard School of Engineering and Applied Sciences