Low-Frequency Piezoelectric Energy Harvester with Novel 3D Folded Zigzag Design and High Power Density

Abstract

Cantilevers have been widely used for vibration energy harvesting applications using piezoelectric materials due to their simple geometries, frequency tune-ability, and closed form analytical solution. Recent studies have focused on overcoming some of the drawbacks for this configuration, which include low power density and natural frequencies much higher than those available in the environment. Some have investigated two-dimensional geometries, such as a zigzag shaped design, or meandering or elephant design. The previously researched designs offer a higher flexibility that allows for much smaller fundamental natural frequencies, and hence, improved power densities. The presented work extends this idea by offering a novel, three-dimensional design called “folded zigzag” that provides a much better flexibility than the aforementioned units, and aids significantly with natural frequency requirements while having a small footprint. The research compares the proposed design to the planar symmetric zigzag design for the same footprint area. This paper demonstrates that the proposed geometry offers a much lower resonating frequency, and results in much improved strain node geometry by avoiding torsion in the fundamental modes of operation. This significantly eases the fabrication by avoiding charge cancellations when mounting continuous electrodes. In addition to that, the new design being more flexible due to its geometry, has higher strain, producing a larger voltage. The graphs produced using validated simulations compare the power densities of various designs. More specifically, the proposed design’s power density is compared to the conventional planar symmetric zigzag design’s power density. The results show that the individual layers of the new design can produce higher power density than a planar symmetric zigzag. This work also outlines the manufacturing process used to fabricate a folded zigzag design with piezoelectric material, which involves strain matching the electrodes, on both the top and bottom layer. Overall, not only is the folded zigzag design more resistant to the formation of strain nodes than the planar zigzag design but it also produces higher power at a low natural frequency, making it suitable for wireless sensor technology and other applications.