Researchers at Harvard have created a 3D-printing nozzle smaller than the width of a human hair, to make microscopic lithium-ion batteries.
As our gadgets shrink ever smaller, the pressure is on to reduce the size of batteries as much as humanly possible. And we're getting close to a workable solution: scientists have just used 3D printing to build the smallest lithium-ion battery in the world — the size of a grain of sand.
Together with the University of Illinois at Urbana-Champaign, researchers at Harvard's Wyss Institute, led by senior author Jennifer Lewis, have turned to 3D printing to create tiny stacks of electrodes, tightly interlaced.
The team created a custom 3D printer with a nozzle narrower than a human hair to lay down the ink — but it's the ink itself that was the trickiest part. First, it had to be able to work as eletrochemically active materials in order to function as the battery's cathodes and anodes. Second, it needed to fulfil the properties of 3D-printing material, exiting from the nozzle in a pliable state and hardening almost instantaneously.
Two inks were developed, incorporating nanoparticles of two different lithium-ion compounds. These were deposited onto the teeth of two gold combs, creating a tightly interwoven stack that was then enclosed in a case with an electrolyte solution that activated the battery.
This solved a previous problem when attempting to manufacture microbatteries. In order to fit inside a tiny device, previous batteries were created of thin films of solid material that were unable to hold sufficient power. The new battery, according to the report "3D Printing of Interdigitated Li-Ion Microbattery Architectures", delivers a lot more.
"The electrochemical performance is comparable to commercial batteries in terms of charge and discharge rate, cycle life and energy densities. We're just able to achieve this on a much smaller scale," said co-author Shen Dillon.
Although they may be tiny, the batteries' potential is huge, with possible applications in fields such as medicine and communications — from tiny flying robots, medical implants and cameras and microphones that could be fitted to a pair of glasses.
"Jennifer's innovative microbattery ink designs dramatically expand the practical uses of 3D printing, and simultaneously open up entirely new possibilities for miniaturisation of all types of devices, both medical and non-medical. It's tremendously exciting," Wyss founding director Donald Ingber said.