We've discussed 3D printed robots, prosthetic noses, and even running shoes. Now a joint development effort by Harvard University, the University of Illinois at Urbana-Champaign, and visiting South Korean researchers has produced a tiny 3D printed lithium-ion battery that could be used one day as a power source for micromedical devices and robots.
This microbattery, which can fit on the head of a pin, is made by printing precisely interlaced stacks of battery electrodes -- each narrower than a human hair. The research combines two current hotbeds of research activity: 3D printing, which is poised to transform manufacturing, and lithium-ion batteries, where scientists are trying to overcome charging and degradation issues.
Harvard University, the University of Illinois at Urbana-Champaign, and visiting researchers from South Korea have demonstrated the ability to 3D print a pinhead-sized battery. These interlaced and stacked electrodes were printed layer by layer to create the working anode and cathode.
(Source: Jennifer A. Lewis/Harvard University)
Shen Dillon, an assistant professor of materials science and engineering at the University of Illinois, and Jennifer A. Lewis, a professor of biologically inspired engineering at the Harvard School of Engineering and Applied Sciences, co-authored a study about their research with three Korean researchers. The National Science Foundation and the Department of Energy supported the work.
Dillon told us in an email that the research team targeted producing interdigitated filamentary electrodes with a radius comparable to the diameter of commercial oxide electrode particles. "We wanted these filaments to be relatively dense to improve the volumetric capacity and positioned closely to one another to improve transport mass kinetics -- ie, diffusion through the electrolyte," he said. "Inks are synthesized from nanoparticle powders and printed in a geometry defined by CAD software."
The main challenge the team faced was formulating the printing inks to work through a 30-micron nozzle. "The general approach is to carefully control the surface chemistry of the individual nanoparticles so that they do not stick to one another during flow under stress, but pack tightly enough together in solution that they do not flow easily in absence of an applied stress." Once the appropriate inks are produced, they can be used for a wide variety of 3D printed structures.
This tiny battery could have myriad uses in microscale systems, including energy harvesting.
"Given the theoretical limitations on battery energy density, it will never be possible that batteries this small will be able to power large devices, such as a cell phone, but there are still a number of devices that require small batteries," Dillon said. "I have always envisioned these batteries being utilized in microscale systems that both harvest and use energy. Such systems naturally require energy storage if the harvesting or use of energy is intermittent."
For example, the battery could power a micro-LED and an optical sensor that measures blood chemistry in the human body for several minutes. "Between measurements the system would have to acquire energy from the environment. This could be from a piezoelectric, thermoelectric, or wireless (RF) energy harvesting."
The battery also could be used to support "brief wireless transmissions" in single-use scenarios like tiny robots sent by the militarly on stealth missions. In these cases, there also would be a harvester present. "This could be useful in battlefield data acquisition where it may be necessary to make measurements with things like robotic insects or inconspicuous microscale devices."