Researchers from Harvard University and the University of Illinois have created a lithium-ion micro battery the size of a grain of sand.  In order to create the batteries, the team used a custom 3D printer fitted with a 0.03 mm wide nozzle. They also invented two new electrochemically active printing materials.

The micro battery design calls for the printer to extrude interlaced stacks of the newly designed anode and cathode materials. Once the stacks are printed, researchers complete the batteries by putting them into containers filled with electrolyte solution.

The micro batteries might be tiny, but they are powerful. The development team announced they have a discharge rate, energy density and cycle life comparable to commercial batteries.

"Not only did we demonstrate for the first time that we can 3D-print a battery, we demonstrated it in the most rigorous way," senior author Jennifer Lewis from Harvard University said.

Lewis discussed several possible applications for the technology, including Harvard's Robobee. The Robobee is a tiny robot designed to fly and behave like a real bee. Researchers hope it will solve some of the pollination issues caused by declining bee populations. "The idea to be able to integrate small [power] sources directly onto those kinds of robotic insects would be powerful and enabling. Right now, everything is tethered to an electric power source. It would be very nice not to have that."

The team also hopes to apply the new technology to hearing aids. Hearing aids can currently be 98% printed using 3D methods, but the electronic components have to be added after the fact.

"Why not print the whole hearing aid?" Lewis said.