The aerogel's properties become even more remarkable when electricity is applied. An electrical charge of less than a volt causes the aerogel to expand 220 percent in milliseconds, many times faster than normal human muscle can move. Even at large voltages, the muscle can expand and contract with virtually no fatigue. Only when operating at extreme temperatures will the carbon nanotube aerogel start to degrade. At more normal temperatures the artificial muscle contracts and expands indefinitely. The new artificial muscle is also stronger than human muscle. "If a human with two arms can lift 200 pounds, then they would be able to lift 32 times that amount," said Baughman. Baughman doesn't like comparing his artificial muscle and real muscle, however. At this point, it is unlikely that artificial muscle will be implanted into humans to replace natural muscle tissue because of its size and the voltages necessary to operate it. Instead, the transparent artificial muscle will likely first be used in solar cells, organic light emitting diodes (OLED) and incandescent light bulbs, among a wide variety of other potential applications. The carbon nanotubes act like electrodes, able to transmit electricity, and are also transparent, allowing light to pass through them. When an electrical charge is applied they become opaque. Before any large scale applications are realized, scientists have to create larger amounts of the aerogel. To create the aerogel in the first place, the scientists use a technique called chemical vapor depositions (CVD). Much simplified, the scientists create an extremely fine mist of individual carbon atoms. These atoms settle on an iron plate and bind to each other to create a what looks like tubes of chicken wire. The densely packed carbon nanotubes are 30 times taller than they are wide. A cross section of the nanotubes looks like a bamboo forest, according to Baughman. To create the aerogel, scientists pull a single "tree" from the forest, which drags other "trees" with it. As the nanotubes emerge they rotate and realign themselves to create the extremely lightweight aerogel. Run electrical current through them and they become an artificial muscle. "Our discovery of methods for producing these carbon nanotube sheets, their strange properties, and their corresponding remarkable performance as artificial muscles is just the beginning of a story," said Baughman. "My guess is that this story will have a happy ending in terms of new products that benefit humankind." Related Links: |
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