A device for energy harvesting from an impact by using a piezoelectric MEMS harvester comprising at least a gear (1) driven by an inertial mass system and a piezoelectric transducer (2) located over the gear in order to keep the system as compact as possible wherein the piezoelectric transducer, such as a cantilever structure, is coupled to the inertial mass system through a tip (3) at the free end of the cantilever so that when the gear rotates, the piezoelectric cantilever is set into motion by the impact between the gear teeth (4) and the tip of cantilever. On the other hand, the piezoelectric cantilever can be set into motion using locked and released of the tip using the gear. In this matter, the tip and gear shape need to be optimized. Moreover, the frictionless coating of the tip using SiC or diamond would be taken into account in order to improve the efficiency of the systems.