It wasn't exactly a display of super strength. The "grip," generated by four polymer strips designed to bend in response to electrical charges, was barely noticeable. But that force is more than enough for the individual strips to wipe dust from the windshield of a palm-size rover that NASA and the Japanese space agency isas will use to explore an asteroid in 2003. "Clearing dust may not seem like a big deal," says Yoseph Bar-Cohen, a physicist at NASA's Jet Propulsion Laboratory, who created the muscles. But using old-fashioned gears and motors, he says, would make the wiper mechanism "bigger and heavier than the whole rover."
No wonder the prospect of artificial muscles has NASA, well, pumped. Traditional robots, even in today's miniature sizes, draw heavily from the limited power supplies on a space probe, and their weight translates into higher launch costs. Bar-Cohen says the components required to construct each strip of artificial muscle cost a total of $200, need just four volts of power and weigh only a fraction of an ounce. Says Rob Manning, chief engineer for nasa's Mars Lander missions: "With all of our basketball-sized spacecraft, we're going to need this kind of technology."
Which is one reason artificial-muscle researchers convened for the first time earlier this month at the International Symposium on Smart Structures and Materials in Newport Beach, Calif. "It's clear that if we're going to build little robots that do things, then they've got to have muscles," says Paul Calvert, a materials scientist at the University of Arizona. He uses polymer gels to construct "Jell-O jacks," which resemble the wobbly dessert but are capable of raising and lowering small objects. Agrees Qiming Zhang, an electrical engineer at Pennsylvania State University: "The only bottleneck is that we haven't found the perfect muscle materials."
That could change, because the mission to asteroid 4660 Nereus has thrust artificial muscles into the limelight. Whereas human limbs move by contracting and relaxing muscles, Bar-Cohen's artificial variety bends in response to electricity. Apply a charge to one side of a strip, and ions within the polymer are pushed to the opposite side, effectively lengthening one surface while shortening the other.
Bar-Cohen foresees construction of artificial limbs that would allow a human to lift heavy objects the way an ant does. He has already received impassioned letters from disabled patients offering to test the first bionic limbs. But such equipment remains years from reality, because the polymer strips and gels being used for muscles are far too pliant to lift heavy weights. Until a new material is found, says Calvert, "you've only got to look at your arm to realize how far we have to go."