Asymmetric air-spaced cantilevers for vibration energy harvesting

This paper reports the study of asymmetric air-spaced cantilevers for vibration energy harvesting. Such novel structures increase the amplitude of the AC voltage generated, leading to a larger AC to DC energy conversion efficiency. The overall energy conversion efficiency is further increased by allowing the majority of the mechanical energy to be used for electricity generation. An analytical model for the bending of asymmetric air-spaced cantilevers is established by decomposing the cantilever deformation into pure bending and S-shape bending. This model is further verified by a discrete component model and finite element simulations. A criterion to determine the dominant bending mode is presented. Design optimization from an energy perspective has also been discussed. Finally, a prototype energy harvesting device based on asymmetric air-spaced cantilevers is constructed and tested. The results from these experiments show good agreement with the analytical model.