Batteries consist of two opposite electrodes -- an anode and cathode -- separated by an electrolyte. In the current work, the MIT team created both the anode and the electrolyte. The team of engineers have described the assembling and successfully testing two of the three key components of a battery. A complete battery is on its way.
First, on a clear, rubbery material the team used a common technique called 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. In 2006, Hammond, Belcher, Chiang and colleagues reported in Science how to do this. Specifically, they altered the virus's genes so it makes protein coats that collect molecules of cobalt oxide to form ultrathin wires -- together, the anode.
The final result: a stamp of tiny posts, each covered with layers of electrolyte and the cobalt oxide anode. Then they turned the stamp over and transfer the electrolyte and anode to a platinum structure that, together with lithium foil, is used for testing.
"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," disclosed MIT professors Paula T. Hammond, Angela M. Belcher, Yet-Ming Chiang and colleagues.
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