Nonlinear MEMS mechanisms for energy harvesting from vibrating source are evaluated. The typical mechanism to harvest energy is based on resonance mechanical bodies (linear systems) that enable collecting energy through self-generating materials and tuned close to the resonance spike. Moreover, it must be observed that in the vast majority of cases the ambient mechanical vibrations come in a vast variety of forms and having the energy distributed over a wide spectrum of frequencies. For this reason the novel approach proposed, is based on a nonlinear vibrating system based on a switching mechanism around two stable states. A wider spectrum is predicted for these nonlinear resonators, so more energy can be saved adopting a bistable dynamic.