In the annals of organized arm wrestling, there had never been a match like this. Ever since 1952, when the first official arm-wrestling competition took place at Gilardi´s Saloon in Petaluma, California, contestants have generally been large men with unusually muscular forearms. But on this Monday afternoon, the TV cameras focus on a slim 17-year-old girl. Panna Felsen´s very participation is odd for a sport that still counts events like the Bad-to-the-Bone Armwrestling Championship in its lineup (and the fact is, she trained harder for her high school´s Science Olympiad than for today´s event). But even more unusual is her opponent. As match time approaches and the crowd grows quiet in the cavernous hotel ballroom, Felsen glances shyly at the phalanx of journalists surrounding her. Then she walks to the padded regulation arm-wrestling table, places her elbow down, and grips her opponent—a white plastic robotic arm.
The first-ever human-robot arm-wrestling match, held in March in San Diego, marked a milestone—as the emcee, Yoseph Bar-Cohen, a physicist at the Jet Propulsion Laboratory in Pasadena, was eager to declare to anyone within earshot. Never mind that Felsen´s opponent looked more like a beefed-up bowling pin than a real human arm. What mattered was the way it moved. The arm that Felsen was about to wrestle, and two more waiting in the wings, had no gears, no shafts, no cams, no moving metal parts whatsoever—a fact that distinguished them from windshield wipers, disk drives, prosthetic limbs and the millions of machines on Earth that create motion using electric motors. The robotic arm clamped to the table across from Felsen was propelled entirely by plastic.
The material driving these arms is a little-known one called electroactive polymer that has an unusual property: When stimulated by electricity or chemicals, it moves. It expands and contracts, curls and waves, pushes and pulls. It´s also springy, durable, quick, forceful and quiet. Since those properties are shared by human skeletal muscles, electroactive polymers have been dubbed “artificial muscle.”
Artificial-muscle enthusiasts like Bar-Cohen foresee a vast array of cheap, light, versatile and powerful actuators—motion-generating devices—for military technology, space vehicles and medical devices. Roy Kornbluh of SRI International, a pioneering artificial-muscle researcher, predicts that the materials could ultimately replace up to half the planet´s one billion electric motors. Already engineers are developing artificial-muscle-powered devices, including a knee brace that prevents injuries, tiny pumps to deliver drugs, and robots that wriggle like snakes, fly like birds, or hop like grasshoppers.
But beyond those devices lies an even more ambitious goal: to replace the genuine article.“In this material, we have the closest to real muscles we ever had,” Bar-Cohen says. Research has begun on a variety of medical devices that would be implanted in or attached to people´s bodies, such as artificial-muscle-powered prosthetics, a pumping device to assist diseased hearts, a urinary sphincter to treat incontinence and an artificial diaphragm to help people breathe. Further—much further—down the road, scientists talk of plastics that could replace or augment any muscle in the body.
Six years ago, Bar-Cohen issued a challenge: Build a robotic human arm that could beat the strongest arm wrestler on Earth. But by 2003, impatient to see his contest actually happen, he eased the requirements. It would be necessary only to prevail over a high-school student, he announced. The rules: Robot arms“should not perform any irritating acts,” such as flashing blinding lights, vibrating, or making annoying noises. And to win, it would have to be able rotate back to its starting position after pinning the human. Now, at the annual scientific conference on artificial muscle in San Diego, three teams claim to have made such a device. The upcoming event excites Bar-Cohen no end.“It´s incredible that we have it at that level!” he raves.
So at just after 5 p.m., Felsen, a senior at nearby La Costa Canyon High School, faces her first opponent. (Bar-Cohen chose her after learning that she´d started an engineering club at her high school and liked to build simple robots for fun.) Projected on a two-story screen at the front of the ballroom is an image of the robotic arm and Felsen, who at the moment resembles a deer in the headlights. Bar-Cohen quiets the crowd in his thick Israeli accent.“OK, go!” he barks. An arm-wrestling champion who had come to see the match has volunteered to help Felsen with her technique. He crouches by the corner of the table.“Stay close. Up on your toes,” he says. The robot doesn´t budge. Felsen, straining, manages a self-conscious smile.“Push harder!” her coach urges. Felsen´s face grows determined, and she struggles to tip the robot arm over.