Batteries built by Viruses ....

What do chicken pox, the common cold, the flu, and AIDS have in common? They’re all diseases caused by viruses, tiny microorganisms that can pass from person to person. It’s no wonder that when most people think about viruses, finding ways to steer clear of viruses is what’s on people’s minds.

Not everyone runs from the tiny disease carriers, though. In Cambridge, Massachusetts, scientists have discovered that some viruses can be helpful in an unusual way. They are putting viruses to work, teaching them to build some of the world’s smallest rechargeable batteries.

Viruses and batteries may seem like an unusual pair, but they’re not so strange for engineer Angela Belcher, who first came up with the idea. At the Massachusetts Institute of Technology (MIT) in Cambridge, she and her collaborators bring together different areas of science in new ways. In the case of the virus-built batteries, the scientists combine what they know about biology (the study of living things), technology and production techniques.

Belcher’s team includes Paula Hammond, who helps put together the tiny batteries, and Yet-Ming Chiang, an expert on how to store energy in the form of a battery. “We’re working on things we traditionally don’t associate with nature,” says Hammond.

Many batteries are already pretty small. You can hold A, C and D batteries in your hand and the coin-like batteries that power watches are often smaller than a penny. However, every year, new electronic devices like personal music players or cell phones get smaller than the year before. As these devices shrink, ordinary batteries won’t be small enough to fit inside.

The ideal battery will store a lot of energy in a small package. Right now, Belcher’s model battery, a metallic disk completely built by viruses, looks like a regular watch battery. But inside, its components are very small—so tiny you can only see them with a powerful microscope.

How small are these battery parts? To get some idea of the size, pluck one hair from your head (unless that seems too painful). Place your hair on a piece of white paper and try to see how wide your hair is—pretty thin, right? Although the width of each person’s hair is a bit different, you could probably fit about 10 of these virus-built battery parts, side to side, across one hair. These microbatteries (“micro” means very small) may change the way we look at viruses.

Slimy liquids that pack a punch
The word “virus” comes from a Latin word that means “poison” or “slimy liquid.” Each virus has a name, and the virus used by Belcher and her team is called M13. To humans, the M13 virus is actually harmless. The virus only infects bacteria. Under a powerful microscope, the M13 virus looks like a thread.

Many batteries are already pretty small. You can hold A, C and D batteries in your hand and the coin-like batteries that power watches are often smaller than a penny. However, every year, new electronic devices like personal music players or cell phones get smaller than the year before. As these devices shrink, ordinary batteries won’t be small enough to fit inside.

The ideal battery will store a lot of energy in a small package. Right now, Belcher’s model battery, a metallic disk completely built by viruses, looks like a regular watch battery. But inside, its components are very small—so tiny you can only see them with a powerful microscope.

How small are these battery parts? To get some idea of the size, pluck one hair from your head (unless that seems too painful). Place your hair on a piece of white paper and try to see how wide your hair is—pretty thin, right? Although the width of each person’s hair is a bit different, you could probably fit about 10 of these virus-built battery parts, side to side, across one hair. These microbatteries (“micro” means very small) may change the way we look at viruses.

Slimy liquids that pack a punch

The word “virus” comes from a Latin word that means “poison” or “slimy liquid.” Each virus has a name, and the virus used by Belcher and her team is called M13. To humans, the M13 virus is actually harmless. The virus only infects bacteria. Under a powerful microscope, the M13 virus looks like a thread.

Changing the recipe
Remember that when a virus invades a cell, it forces the cell to start making new virus particles. At MIT, the scientists are turning that relationship on its head. Belcher and her team are able to go inside the virus and change its genetic recipe. With these changes, the scientists turn the tiny foe into a useful friend.

Instead of attacking other cells, the altered virus does something no natural virus would do: It starts to collect little bits of metal on its shell. Soon the virus is covered by a tiny suit of armor. Underneath the metal, the virus is still there. Belcher likens the virus to a scaffolding—the support structure you might see outside a building that is under construction. The virus provides the structure, giving form to the metal parts while the parts are being put together.

“The virus remains intact, but is completely covered,” Belcher says.

This metal structure plays an important part in the battery. After the battery charges and discharges, she says, the virus itself may break down, but the metal structure will remain.

A battery is made of three main parts: two electrodes and an electrolyte. Electrodes are pieces of metal with electric charges, and an electrolyte is a material between them. You might think of a battery as a peanut butter sandwich, where the metal electrodes are like the bread and the peanut butter is the electrolyte. (For more information, see What is a Battery? below.)

The metal collected by the virus can be used as an electrode. In 2006, the team built only one electrode, but their research has advanced quickly since then. “We have the materials where we can make the full microbattery now as well,” Belcher says. Last year, together with Hammond and Chiang, she showed how the virus-built electrodes can be produced quickly and cheaply, without toxic chemicals. And earlier this year, with another team of engineers, she helped design the other electrode. When Belcher’s team tested the new, complete battery in the laboratory, it performed as well as other rechargeable batteries.

The microbatteries could be used to power a wide variety of tiny electronic devices. “Because [the batteries] are very small, they can be implemented into anything that involves microfabrication,” says Hammond.

In addition to the ever-shrinking world of electronics, the batteries may also play a role in the search for alternative energy sources. One reason we don’t see more electric vehicles on the road is that they require many heavy batteries to operate. If Belcher, Hammond and Chiang’s work is any indication, then lighter, more efficient batteries aren’t too far away. Just think—the batteries in your car may one day be built with help from a virus!

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