Researchers at the University of California, Berkeley, the University of Michigan and MIT have created glass "leaves" with networks of veiny channels filled with water. The smallest channels extend all the way to the edges of the leaf, where open ends allow water to evaporate, which draws water along the central stem of the leaf -- at a rate of about 1.5 centimeters per second. The glass leaves have been wired for electricity by adding metal plates to the walls of the central stems and connecting them to a circuit. Researchers then charge the plates and the water inside the stems creates two conducting layers separated by an insulating layer, which acts as a capacitor. The waterflow is then periodically interrupted with air bubbles, and every time a bubble passes through the plates a small electrical current is generated -- about 2 - 5 microvolts per bubble. The team thinks that on a large scale, artificial trees could be use to generate large amounts of energy entirely through evaporation.