The self-charging cellphone

YOUR cellphone need never again run out of juice while you're on the go. So says Nokia of Finland, which filed a US patent last week for a handset that recharges itself by harvesting energy from the owner's motion.

Nokia envisages a phone in which the heavier components, such as the radio transmitter circuit and battery, are supported on a sturdy frame. This frame can move along two sets of rails, one allows it travel up and down, the other side to side.

Strips of piezoelectric crystals sit at the end of each rail and generate a current when compressed by the frame. So as the user walks, or otherwise moves the phone, the motion generates electricity. This charges a capacitor which in turn trickles charge into the battery, keeping it topped up.