Robot feet that don’t need batteries.

Nature studies the beauty of mechanical advantage… in exoskeleton boots that do what feet do just a little bit better, faster, stronger:

People walking in the boots expend 7% less energy than they do walking in normal shoes, the devices’ inventors report on 1 April in Nature1. That may not sound like much, but the mechanics of the human body have been shaped by millions of years of evolution, and some experts had doubted that there was room for further improvement in human locomotion, short of skating along on wheels.

As early as the 1890s, inventors tried to boost the efficiency of walking by using devices such as rubber bands, says study co-author Gregory Sawicki, a biomedical engineer and locomotion physiologist at North Carolina State University in Raleigh. More recently, engineers have built unpowered exoskeletons that enable people to do tasks such as lifting heavier weights — but do not cut down the energy they expend. (Biomechanists still debate whether the running ‘blades’ made famous by South African sprinter Oscar Pistorius are more energetically efficient than human feet….)

The researchers’ exoskeleton structures, built of lightweight carbon-based materials, have a spring that connects the back of the foot to just below the back of the knee, where it attaches with a mechanical clutch…. When the Achilles tendon is being stretched, the clutch is engaged and the spring, rather like an additional tendon, stretches and helps to store energy. After the standing leg pushes down, unleashing elastic energy, the clutch releases and absorbs the slack in the spring, in preparation for the next cycle.

Video at the link!