BESTMEMS is an international collaborative project between Taiwan and France which proposes to deeply analyze the energy conversion steps involved in vibration energy harvesters and in self-powered systems, going from the transduction material to the global system through mechanical and electrical domains as well energy management. In addition to the scientific advances in each specific domains (such as the fabrication of highly electromechanically coupled transducer, the design of a system able to scavenge energy on a wide vibration frequency band or the conception of efficient electrical interface for energy extraction), BESTMEMS purpose also encompasses a detailed analysis of the interfaces between all of the investigated fields, allowing a global approach and optimization of the system as the whole, and hence permitting the design of a truly enhancement compared to the associated of locally optimized blocks ; the latter approach yielding a sub-optimal global system because of the bidirectional couplings between each stage. Finally, BESTMEMS features a strong willingness of realistic applications and proposes, in addition to the microgenerator design itself, the inclusion of the later in a complete system (which would also permit giving general guidelines for the design of self-powered devices) that addresses strong socio-economical needs and challenges, through, for example, the development of a Tyre Pressure Monitoring System (TPMS) able to operate using tyre vibrations, as well as the design of a Structural Health Monitoring (SHM) device integrated within bearings. This strong applicative target is besides supported by the presence of industrial partners within the project consortium.
The approach proposed in the framework of BESTMEMS lies in two levels. From a “local” point of view (i.e., study in each domains addressed by the project), significant scientific advances are expected in the development and fabrication of efficient piezoelectric microtransducers through the optimization of aerosol deposition technique, that is simple but efficient. From a mechanical and electromechanical point of view, the design of a system taking advantage of intrinsic material nonlinearities and/or externally induced nonlinearities will allow converting energy on a wide vibration frequency band. Finally, the design and integration of nonlinear electrical energy extraction interfaces will permits a significant gain in terms of harvested energy compared to classical approaches, while ensuring a power harvesting independent from the connected load (or equivalently to the state of the connected device). BESTMEMS also includes a “global” aspect in terms of the design and conception of self-powered devices. Rarely taken into account in the literature, the fine and deep analysis of the combination of each stage (material, mechanical and electrical) will be done thanks to the complementarity of the consortium expertise. Hence, this global methodology, conducted with a particular attention paid to the interfaces between each domain, will lead to the emergence of new approaches for the global optimization of the system. This scientific expertise merging will not only lead to the optimization of the harvested energy by the microgenerator, but will also go further through the inclusion of the later within a full self-powered system, with a particular study of the energy balance between the available and required operating energy, including the development of energy management strategies as well as the selection and/or the design of ultralow-power sensors.