3D Printed Batteries can Help Make Miniature Medical Implants

Harvard researchers have now shown that lithium-ion batteries as tiny as a grain of sand could be printed using 3D printing technology. These batteries could be used to power tiny medical implants.

Each tiny battery is made of stacks of small battery electrodes that have the same width as a strand of human hair. The batteries were made by a team of researchers from Harvard University and the University of Illinois at Urbana-Campaign.

"Not only did we demonstrate for the first time that we can 3D-print a battery, we demonstrated it in the most rigorous way," said Jennifer Lewis, Ph.D., from the Harvard School of Engineering and Applied Sciences (SEAS) and senior author of the study.

Recently many engineers have built tiny medical equipment. However, powering these devices has been a major challenge as batteries that deliver adequate power are often larger than the device. Other designs for smaller batteries failed because they couldn't pack-in much power.

The latest study has demonstrated that not only can batteries be made smaller, but can also be printed easily. The latest type of miniature batteries has tightly interlaced electrodes that are stacked over each other. The electrodes are ultrathin and are built out of a plane.

3D material printing works by following instructions from a 3D drawing and using it to deposit successive layers of material. Lewis's team has designed functional 3D inks that have chemical and optical properties. By using these inks they can build structures with customized optic, chemical, mechanical and biological properties.

In this study, researchers needed a material that had electrochemical properties. For this, they created an ink with nanoparticles of one lithium oxide compound that served as anode and an ink from nanoparticles of another lithium oxide compound, which acted as a cathode.

These inks were then deposited on the teeth of two gold combs, leading to a tightly interlaced stack of anodes and cathodes. The electrodes were packed into a tiny container which was filled with an electrolyte, completing the entire battery.

Researchers then calculated the amount of power that these batteries could deliver.

"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 Shen Dillon, an Assistant Professor of Materials Science and Engineering and co-author of the study, according to a news release.

The study is published in the journal called Advanced Materials.