Interdigitated cantilever array topology for low frequency MEMS vibration energy harvesting

Micro-fabricated vibration energy harvesters enable merits such as miniaturisation, economies of scale for manufacturing, and ease of integration with semiconductor IC technologies. However, the frequency range of ambient vibration is generally low (10's Hz to 100's Hz). Existing MEMS vibration energy harvesters that target these frequencies typically are in the centimetre scale range. This sacrifices the miniaturisation aspect as well as introducing new challenges in packaging and integration for the unconventionally large MEMS devices. This paper proposes a new interdigitated fork cantilever array topology, which allows for up to about a third reduction in resonant frequency compared to the classical cantilever topology, for the same design area and without compromising on power optimisation. Further resonant frequency reduction is also possible, but at the expense of power optimisation. This opens up design flexibility to achieve low frequency MEMS resonators that are more suitable to practically target ambient vibration, without sacrificing the aforementioned merits of MEMS technology.