Scientists at the University of Washington have taken the idea of green energy to the next level by devising an electrical circuit that draws its power entirely from trees.
By hooking nails to trees and connecting a voltmeter, researchers found that the bigleaf maples common on their campus generate a steady voltage of up to a few hundred millivolts.
A boost converter was then developed to produce an output voltage of 1.1 volts, enough to run low-power sensors.
While tree power is unlikely to replace solar power for mainstream applications, the system could potentially be used to power tree sensors which detect environmental conditions, warn of forest fires and gauge a tree's health.
"I'm interested in applying our results as a way of investigating what the tree is doing," commented co-author Babak Parviz.
"When you go to the doctor, the first thing that they measure is your pulse. We don't really have something similar for trees."
Last month researchers at the University of Washington developed circuits built with organic semiconductors capable of transporting both positive and negative charges.