| Mechanical Energy Harvesters Utilizing (001) Textured PZT Films on Flexible Metal Foils |
| Hong Goo YEO |
| The Pennsylvania State University |
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Recently, interest in extracting energy from human activities such as walking, breathing, typing, and so on using piezoelectric energy harvester is growing.1~3 However, there are unique challenges to self-powering wearable devices from a user¡¯s activities such as weak base excitation, potential damage to fragile structure by shock input, and the low vibration frequency (<10Hz). Thus, a high efficiency, flexible, low resonance frequency harvester with a wide bandwidth is needed. Piezoelectric Compliant Mechanism (PCM), suggested by Ma and Rahn, shows a significantly higher efficiency with uniform strain for its 1st mode, than a simple cantilever design with the strain decreases along the length of the PZT beam. So, higher sensitivity, efficiency and larger power are predicted as compared with that of PCM at low frequency mechanical vibration.
This work shows that strongly {001} oriented PZT could be deposited by RF magnetron sputtering and ex situ annealing on (100) oriented LaNiO3 / HfO2 / Ni foils. Based on this design, the PCM design with PZT films on Ni foil consists of three main structures such as PZT beam, flexible frame used for compliant hinge and rigid frame for support structure by 2.9 mm thick acrylic plate. The performance of PCM with actual device area of 6.34 cm2 exhibits an average power of 7.5 ¥ìW response at a 0.1 G (G=9.8 m/s2) excitation level at a resonance frequency of 7.8 Hz after hot poling to align the c-domains out-of-plane. Table 1 exhibits the power performance generated with various excitation accelerations and area power density at 7.8Hz.
Table 1. Performance of PCM harvesting devices at various excitation levels.
References:
[1] P. Pillatsch, E. M Yeatman, A. S. Holmes, Sensors and Actuators A 206, 178 (2014)
[2] J. Yun, S. N. Patel, M. S. Reynolds, G. D. Abowed, Computing 8, 1 (2010).
[3] J. M. Donelan, Q. Li, V. Naing, J. A. Hoffer, D. J. Weber, A. D. Kuo, Science 319, 807 (2008).
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| Acknowledgements : This work was supported by a National Security Science and Engineering faculty fellowship and the NSF ASSIST ERC (EEC-1160483). |
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