This paper deals with the problem of gathering electrical energy from sources readily available in the environment. In particular we focus on vibrations that are almost ubiquitous and that very often appear as random, weak and low frequency signals. The above listed features may significantly reduce the efficiency of traditional linear resonant and therefore alternative innovative strategies need to be explored. In this paper we present some devices that have been analytically modeled and experimentally verified for tackling this issue. The basic idea is centered on the use of bistable oscillators to realize vibration harvesters that can scavenge energy from broadband, weak, random vibrations: this idea will be expanded here toward some solutions where bistability is obtained by using magnets but also where it descends from purely mechanical devices. A brief review on solutions developed that exploit magnetic and non magnetic strategies for obtaining bistability is presented, finally the issue of MEMS fabrication for the devices conceived will be discussed.
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