The energy for the next generation of miniature electronic devices could come from tiny microbatteries about half the size of a human cell and built with viruses. Engineers at the Massachusetts Institute of Technology (MIT, Cambridge, MA) have developed a battery that could one day power a range of miniature devices, by stamping them onto a variety of surfaces.
The researchers have created both an anode and an electrolyte. They’re currently working on the last piece of the battery puzzle: a cathode.
“To our knowledge, this is the first instance in which microcontact printing has been used to fabricate and position microbattery electrodes and the first use of virus-based assembly in such a process,” says Angela Belcher, a professor of materials science and biological engineering. “The technique itself does not involve any expensive equipment, and is done at room temperature.”
On a clear, rubbery material, Belcher and her colleagues used soft lithography to create a pattern of tiny posts either four or eight millionths of a meter in diameter. On top of these posts, they then deposited several layers of two polymers that together act as the solid electrolyte and battery separator.
Next came viruses that preferentially self-assemble atop the polymer layers on the posts, ultimately forming the anode. They altered the virus’s genes so it makes protein coats that collect molecules of cobalt oxide to form ultrathin wires.
The final result is a stamp of tiny posts, each covered with layers of electrolyte and the cobalt oxide anode. “Then, we turn the stamp over and transfer the electrolyte and anode to a platinum structure that, together with lithium foil, is used for testing,” says Paula Hammond, associate head of MIT’s Department of Chemical Engineering. “The resulting electrode arrays exhibit full electrochemical functionality.”
In addition to developing the third part of a full battery-the cathode-via the viral assembly technique, the team is exploring a stamp for use on curved surfaces. “We’re also interested in integrating [the batteries] with biological organisms,” Belcher points out.