...AND CHEAPER...:

But the electric motor is in the midst of launching a far bigger, far more subtle revolution--not in cars, but robots. Open up a robotic arm and you'll find that its joints are actually electric motors, known as actuators. Actuators make robots leap and run and do backflips and lift 500-pound pipes (different robots, mind you, thank God). The electric car? That's impressive as hell, but just the beginning. It's robots that are fueling the quiet ascendance of the electric motor.

So what is an electric motor, exactly? Well, it's an opposition machine. Inside the device are permanent magnets and an electromagnet; apply current to the electromagnet and it pushes against the permanent ones, spinning the motor. Typically, this is paired with a gearbox, because electric motors are most efficient when they spin at very high speeds. And because the electric motor isn't working alone, but with a transmission, the whole operation is called an actuator. So every time you see a robot move, it's the magic of magnets at work--a seemingly simple force that powers an incredible variety of machines. And actuators are growing more precise and more sensitive by the day.

"Developing highly capable and low cost and easy to use actuators is of paramount importance for the future of robotics," says roboticist Howie Choset of Carnegie Mellon University. "If we want to really hit the tipping point with robotics, so robots can reach the masses, we have to make these systems easy to use as well as low cost."

That revolution is already well under way. 3-D printers that lay down carbon fiber are making it easier than ever for roboticists to iterate their actuators quickly. Even cooler: 3-D metal printing is emerging, which would mean engineers could print out magnets for actuators on demand.

Meanwhile, the cost of actuators is plummeting. "Then there's not a whole lot for costs in a robot besides the actuators," says roboticist Stephen McKinley of UC Berkeley. "That's where the cost for a robot arm lies." An actuator that used to set you back $3,500 has fallen to perhaps $1,700. That's thanks in part to a growing robotics industry that's creating an economy of scale for the parts.

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