As devices shrink to microscopic proportions they need similarly-sized batteries to make them run. Although no such batteries exist today, a team of Massachusetts Institute of Technology (MIT) researchers this week reported in the Proceedings of the National Academy of Sciences (PNAS) a breakthrough in their work to create a microbattery that's small enough (yet powerful enough) to run a range of miniature devices, including labs-on-a-chip and implantable medical sensors.

(From left, professors Yet-Ming Chiang, Angela Belcher and Paula Hammond display a virus-loaded film that can serve as the anode of a battery in 2006. Photo courtesy of Donna Coveney, MIT)

The researchers, who include MIT professors Angela Belcher, Paula Hammond and Yet-Ming Chiang, made and positioned the mini-electrodes required to make such a small battery with help from the M13 virus, which is 6.5 nanometers in diameter and 880 nanometers in length. Belcher was Scientific American's 2006 Research Leader of the Year, and is well-known for her work engineering the M13 to latch onto and coat itself with tiny specks of semiconductor material (such as gold and cobalt dioxide), yielding metal nanowires that could be assembled into high energy-density electrodes.

The next step is to develop the final missing piece of the battery—the cathode, or positive electrode that receives electrons from the device the battery is powering—using their viral assembly technique. "Cathode materials are currently being investigated for a fully self-assembled microbattery," Belcher and her colleagues write.


(An array of microbattery electrodes, each only about four micrometers, or millionths of a meter, in diameter. Photo courtesy Belcher Laboratory; MIT)