Knee Brace Harnesses 'Power Walking'

Feb. 8, 2008 -- Talk about power walking. A new knee-mounted device converts the kinetic energy of strolling, sauntering and striding into usable electricity.

The energy harvested could work to power portable electronics, such as GPS locators or cell phones or supply electricity to motorized prosthetic joints and implanted neurotransmitters.

"There is power to be harvested from various places in the body, and you can use that to generate electricity. The knee is probably the best place," said Arthur Kuo, an associate professor of mechanical engineering at the University of Michigan in Ann Arbor.

Kuo and colleagues from Simon Fraser University in Canada and the University of Pittsburgh describe the technology in this week's issue of Science.

At first glance, the knee brace looks like the future of orthopedic support. But this brace goes beyond buttressing to not only making walking easier but to also generate electricity along the way.

A small oblong generator and an aluminum chassis -- complete with transmission, clutch, sensor and computer controls -- are mounted to the outside of the brace.

As the person walks, each leg swings naturally forward and back, with a stance in the middle, when the foot is firmly on the ground. The sensor, called a potentiometer, monitors the knee's angle during the swing and stance phases and feeds that information to the computer.