  Integration of structures and functions allowed reducing electric
consumptions of sensors, actuators and electronic devices. Therefore, it is now
possible to imagine low-consumption devices able to harvest their energy in
their surrounding environment. One way to proceed is to develop converters able
to turn mechanical energy, such as vibrations, into electricity: this paper
focuses on electrostatic converters using electrets. We develop an accurate
analytical model of a simple but efficient cantilever-based electret energy
harvester. Therefore, we prove that with vibrations of 0.1g (~1m/s^{2}), it is
theoretically possible to harvest up to 30\muW per gram of mobile mass. This
power corresponds to the maximum output power of a resonant energy harvester
according to the model of William and Yates. Simulations results are validated
by experimental measurements but the issues of parasitic capacitances get a
large impact. Therefore, we 'only' managed to harvest 10\muW per gram of mobile
mass, but according to our factor of merit, this puts us in the best results of
the state of the art. http://iopscience.iop.org/0964-1726/20/10/105013
