Charge-pumping in a synthetic leaf for harvesting energy from evaporation-driven flows

Inspired by water transport in plants, we present a synthetic, microfabricated "leaf" that can scavenge electrical power from evaporative flow. Evaporation at the surface of the device produces flows with velocities up to 1.5 cm/s within etched microchannels. Gas-liquid interfaces within the channels move across an embedded capacitor at this velocity, generating 250 ms, 10-50 pF transient changes in capacitance. If connected to a rectified charge-pump circuit, each capacitive transient can increase the voltage in a 100 mu F storage capacitor by similar to 2-5 mu V. We provide estimates of power density, energy density, and scavenging efficiency. (C) 2009 American Institute of Physics. [DOI:10.1063/1.3157144]