Turning On Virus Power

by:
Jonathan Fahey, 11.05.08, 12:01 AM ET


The way Angela Belcher sees it, nature could do a lot more, if only given the opportunity.
Belcher, a materials science and biological engineering professor at the Massachusetts Institute of Technology, has long marveled at how abalone can spin a little calcium, carbon and oxygen into exquisite and incredibly strong shells. While still at the University of California at Santa Barbara, where she did her graduate work with a view of the Pacific Ocean, Belcher wondered if nature could make new materials when given combinations of elements that seldom occurred together.
"I wanted to know if you could get biology to work with the rest of the periodic table," she explains.
The answer is yes.
Belcher and two MIT colleagues, chemical engineering professor Paula Hammond and ceramics professor Yet-Ming Chiang, are coaxing viruses to assemble micro-batteries which are the size of a human cell. They could one day be used to power tiny devices like sensors or medical diagnostic tools.
In every abalone cell, and in every cell for that matter, there are instructions, written in DNA, for how to take elements like calcium, carbon and oxygen and arrange the atoms in certain extremely specific ways to produce something hard. Biology makes the world's best nanomaterials.
Nature worked on this problem for millions of years until finally, about 540 million years ago, the first shell-bearing creatures began to appear at the beginning of what is known as the Cambrian period. (Belcher has founded a company called Cambrios, in Sunnyvale, Calif., to commercialize some of her discoveries.)
Creatures settled on elements like calcium, carbon and oxygen because that's what was abundant. Belcher now runs evolution on fast-forward but under different conditions, trying to make new materials as amazing as an abalone shell that are more useful for humans.
She uses a well-known and simple virus that usually infects bacteria, called M13, and runs experiments on them, 1 billion at a time. She exposes them to the chemical she is interested in, cobalt oxide and gold in the case of her battery work, and selects those viruses that produce proteins with an affinity for the chemical.
Over a period of about two weeks, and thousands and thousands of virus generations, she can produce a strain of virus evolved to do her bidding and then clone it. Her battery-producing viruses cover their entire 880 nanometer-lengths with tiny balls of cobalt oxide and gold, leaving her with nanowires--six nanometers in diameter and 880 nanometers long. These function as the battery's anode.
Trying to make nanowires like this using human-engineered manufacturing processes would be expensive, if not impossible.
Belcher's colleague Paula Hammond, an expert in making highly ordered, self-assembling polymers and other materials, created a pattern of tiny posts, onto which the researchers deposited several layers of polymers that act as the battery's electrolyte.
The electrolyte is designed to be charged in such a way that it can help the viruses--shod in their metal-oxide coats and negatively charged--line up just so. "By harnessing the electrostatic nature of the assembly process with the functional properties of the virus, we can create highly ordered composite thin films combining the function of the virus and polymer systems," Hammond says.
The result is a stamp of the posts that under a microscope looks like a sheet of bubble wrap, each covered with layers of electrolyte and the cobalt oxide anode. The scientists can then turn the stamp over, and "print" their batteries.
Hopefully. They've tested the anode and the electrolyte, but they are still working on the final piece--the battery's cathode--using this same method.
"We'd like to stamp the final cathode on top," says Hammond.
Belcher, who came to MIT in 2002, won a MacArthur "genius" award in 2004 and works out of an office that is littered with more matter, both organic and inorganic, than any living thing could create order from. Hammond's office, meanwhile, resembles one of her self-assembled patterns--nothing is out of place. Together with Chiang, a founder of the lithium-ion battery company, A123 Systems, the three hope they will soon have a power pack for, say, an implantable cancer diagnostic.
It shouldn't take a million years. In fact, Belcher hopes her designs will turn into products within a much more manageable five years' time.