Research

Wireless sensor nodes are being deployed in a variety of scenarios including buildings, bridges, transportation systems, and industrial machines in the low frequency range (below 100 Hz) [1,2]. In these applications there is access to low frequency mechanical vibrations that can be tapped to generate electrical energy. There are multiple ways to convert mechanical energy into electrical energy such as piezoelectric, electromagnetic, triboelectric, and electrostatic. However, the challenge in conversion of mechanical to electrical energy has been the low conversion efficiency and power density. We propose a solution to these issues by developing piezoelectric energy harvesters with complex beam geometries. A systematic modeling will be conducted to evaluate the output power from different complex beam geometries including Arc-Based Cantilevers (ABCs) and Spiral-Based Cantilevers (SBCs). The modeling will be validated through experiments conducted on ABC and SBC energy harvesters.

Recent developments have raised power harvesting to as much as 10 mW per 1 mT applied magnetic field [3]; however, such power generation is still insufficient for charging of remote sensors for much more than small LEDs. This observation motivates our first research objective: To model, design, fabricate, and test piezoelectric energy harvesters of complex geometries for improved power generation.

[1]   Aktakka, E. E., Peterson, R. L., and Najafi, K., 2012, “Integration of Bulk Piezoelectric Materials into Microsystems,” University of Michigan.

[2]   Lee, B. S., Lin, S. C., Wu, W. J., Wang, X. Y., Chang, P. Z., and Lee, C. K., 2009, “Piezoelectric MEMS Generators Fabricated with an Aerosol Deposition PZT Thin Film,” J. Micromechanics Microengineering, 19(6), p. 065014.

[3]   Annapureddy, V., Na, S. M., Hwang, G. T., Kang, M. G., Sriramdas, R., Palneedi, H., Yoon, W. H., Hahn, B. D., Kim, J. W., Ahn, C. W., Park, D. S., Choi, J. J., Jeong, D. Y., Flatau, A. B., Peddigari, M., Priya, S., Kim, K. H., and Ryu, J., 2018, “Exceeding Milli-Watt Powering Magneto-Mechano-Electric Generator for Standalone-Powered Electronics,” Energy Environ. Sci., 11(4), pp. 818–829.

Image taken from Sharpes, N., Abdelkefi, A. and Priya, S. (2015) ‘Two-dimensional concentrated-stress low-frequency piezoelectric vibration energy harvesters’, Applied Physics Letters, 107(9), p. 093901. doi:10.1063/1.4929844. Link.

Lithium ion batteries have been shown to have multifunctional capabilities including energy storage and actuation without external cumbersome wires after charging such as might be used in other types of actuators. Segmenting a lithium ion battery actuator has been shown to increase blocked force per volume relative to a non-segmented actuator of same length and actuation force as well as enable more complex, tailorable shapes than its non-segmented actuator counterpart. Both the analytical model and commercial FEA are successfully validated with experimental deflection data for a uniform unimorph at various SOC.

Gonzalez, C., Ma, J., Frecker, M. and Rahn, C. (2021) ‘Analytical modeling and simulation of a multifunctional segmented lithium ion battery unimorph actuator’, Smart Materials and Structures, 30(1), p. 015039. doi:10.1088/1361-665X/abc7fb. Link.