A Silicon Disk with Sandwiched Piezoelectric Springs for Ultra-low Frequency Energy Harvesting

Exploiting the sporadic availability of energy by energy harvesting devices is an attractive solution to power wireless sensor nodes and many other distributed modules for much longer operation duration and much lower maintenance cost after they are deployed. MEMS energy harvesting devices exhibit unique advantageous of super-compact size, mass productivity, and easy-integration with sensors, actuators and other integrated circuits. However, MEMS vibration energy harvesting devices are rather difficult to be used practically due to their poor response to most of the ambient vibrations at ultra-low frequency range. In this paper, a micromachined silicon disk with sandwiched piezoelectric springs was successfully developed with resonant frequency of 15.36 similar to 42.42 Hz and quality factor of 39 similar to 55 for energy harvesting. Footprint size of the device was 6 mm x 6 mm, which is less than half of the piezoelectric cantilevers, while the device can scavenge reasonably high power of 0.57 mu W at the acceleration of 0.1 g. The evaluation results also suggested that the device was quite sensitive as a sensor for selective monitoring of vibrations at a certain frequency.