Shown in the photos above: (a) Knee-joint piezoelectric harvester. It is worn on the
external side of the knee and fixed by braces. Inside, a hub carries a
number of bimorphs, which are plucked by the ring-mounted plectra as the
joint rotates during walking. (b) Geometrical details of the harvester
showing side view (above) and top view of the mounted bimorph.
Click on image to enlarge
A team of UK researchers from Cranfield University, the University of Liverpool and the University of Salford proposes a piezoelectric energy harvester to be worn on the knee-joint that relies on the plucking technique to achieve frequency up-conversion. The energy harvester, which is designed to fit onto the outside of the knee, is circular and consists of an outer ring and central hub. The outer ring rotates as the knee joint goes through a walking motion. The outer ring is fitted with 72 plectra which "pluck" four energy-generating arms attached to the inner hub.
By strapping the energy harvester to the knee joint, a user could power body-monitoring devices such as heart rate monitors, pedometers and accelerometers by simply walking and not have the worry of running out of power and replacing batteries.