The hype surrounding nanotechnology usually conjures images of microscopic machines acting to repair and monitor things ranging from macroscopic machines to the human body. But the machines themselves have been largely hypothetical, constrained by limitations such as power sources and manufacturing techniques. As a result, many of the successful applications of nanotechnology have involved chemical or biological systems. A new report in Science Express details a technique that may help bridge the gap between the biology and machine worlds on the nanoscopic level.
The MIT-based research group, led by Angela Belcher (who is the recipient of a MacArthur "genius grant"), has extensive experience in mixing the biological with the chemical. The basis of her research is the recognition that many biological systems can self-assemble into structures with regular and defined dimensions. Her work combines that knowledge with the known activity of many proteins that bind atoms or small chemical compounds. By using the biological structure as a backbone, and adding in the appropriate binding sites, the biology can serve as a scaffold for assembling collections of metals or ceramics, generating useful materials on the nanoscopic scale of the original biological material.
Her latest breakthrough has great potential for use in batteries. On the chemical side, the group chose to work with cobalt oxide, which "has shown excellent electrochemical cycling properties and it thus under consideration as an electrode for advanced lithium batteries." On the biological end of things, the picked the bacterial virus (or "phage") M13, which has been used in molecular biology for decades. M13 forms protein-coated filaments 6 nanometers across with a length that's determined by the amount of DNA packaged in them. The M13 coat protein was modified to include a binding pocket for gold atoms, which helped with electrical conductivity, and placed in a cobalt solution. The result was an ordered array of wires spaced at 6 nanometers and composed of a combination of cobalt oxide and gold. These are still a cathode away from being functional nano-batteries, but with the basic structure in place, that next step is sure to follow.
How quickly it follows, and whether it ever makes it past the stage of an interesting proof of concept are different questions. To generate useful currents, the wires of a battery have to be connected, and connecting wires on the scale of 6 nanometers is likely to prove to be quite a challenge. After all, the most advanced chip fabrication facilities are only beginning to experiment with 45 nanometer lithography techniques, and commodity components (which is how batteries are viewed) rarely use leading edge fab technology. It may be possible to generate these nano-wires within a larger-scale wired framework generated by more traditional methods. How well the standard and biological technologies integrate, and whether they do so at an economically sensible price, may prove to be the ultimate test of this technique's utility.