Wideband MEMS energy harvesters utilizing nonlinear springs
Appears in the following Collection
- Institutt for informatikk 
AbstractMicro-scale energy harvesting from motion has received increasing research interest. The energy harvesters can be used as replacements for batteries in low-power wireless electronic devices. Conventional vibration energy harvesters are designed as linear resonance structures. These have a very narrow bandwidth and operate efficiently only when the excitation frequency is very close to the resonant frequency of the harvester. The narrow bandwidth limits their applications in realworld environments that have a wide spectrum of frequencies or varying vibration spectra.
This thesis investigates a method to extend the bandwidth of the energy harvesters. We exploit nonlinearities of suspensions, in particular softening and bistable characteristics, to widen the harvesting bandwidth. The nonlinear-spring characteristics are obtained purely through their geometrical design without relying on extra features such as permanent magnets that can interfere with the surroundings.
Two electrostatic energy harvesters are designed, fabricated and characterized based on microelectromechanical systems (MEMS). The first harvester with a quad-angled spring, which displays a softening characteristic, is made by through-wafer-thickness deep-reactive ion etching onto a silicon wafer. The experimental results show that a 13-fold increase in the bandwidth of the harvester with the angled springs and an average output power increase of 68% compared with that of linear-vibrating energy harvesters at a broadband random vibration of 7×10−4 g2/Hz. We also find that the harvester is tolerant to variations both in the center frequency and bandwidth of vibration, and can perform close to its theoretical maximum with wideband vibrations.
The second MEMS electrostatic energy harvester with curved springs is fabricated on a silicon-on-insulator wafer using bulk micro-fabrication technology. The curved springs display an asymmetrical bistable behavior obtained purely through geometrical design. The experimental results with a white noise vibration at 4×10−3 g2/Hz show that the harvester bandwidth reaches 715 Hz, representing the largest bandwidth reported in the literature so far.
Such wideband harvesters are well-suited to extract power from a wide spectrum of vibrations or from sources with a wide range of variability in the spectrum.
List of papers
Papers 1, 4 and 5 are removed due to publisher restrictions.
1 L. G. W. Tvedt, S. D. Nguyen, and E. Halvorsen, ”Nonlinear behavior of an electrostatic energy harvester under wide- and narrowband excitation,” IEEE/ASME Journal of Microelectromechanical Systems, vol. 19, no. 2, pp. 305-316, Apr 2010. DOI: 10.1109/JMEMS.2009.2039017
2 S. D. Nguyen and E. Halvorsen, ”Analysis of vibration energy harvesters utilizing a variety of nonlinear springs,” Proceedings of PowerMEMS 2010 (Leuven, Belgium, Nov 30 Dec 3), pp.331-334, 2010.
3 S. D. Nguyen and E. Halvorsen, ”Wideband energy harvester utilizing nonlinear springs,” Proceedings PowerMEMS 2009 (Washington D.C., USA, Dec 1-4, 2009) pp.411-414, 2009.
4 S. D. Nguyen, E. Halvorsen, G. U. Jensen and A. Vogl, ”Fabrication and characterization of a wideband MEMS energy harvester utilizing nonlinear springs,” Journal of Micromechanics and Microengineering, vol. 20, no. 12, p. 125009 (11p), Dec 2010. DOI:10.1088/0960-1317/20/12/125009
5 S. D. Nguyen and E. Halvorsen, ”Nonlinear springs for bandwidth-tolerant vibration energy harvesting,” IEEE/ASME Journal of Microelectromechanical Systems, vol. 20, no. 6, pp.1225-1227, Dec 2011. DOI: 10.1109/JMEMS.2011.2170824
6 S. D. Nguyen, E. Halvorsen and G. U. Jensen, ”Wideband MEMS energy harvester driven by colored noise,” submitted to IEEE/ASME Journal of Microelectromechanical Systems, Nov 2012. DOI: 10.1109/JMEMS.2013.2248343
7 S. D. Nguyen, N. H. T. Tran, E. Halvorsen and I. Paprotny, ”Design and fabrication of MEMS electrostatic energy harvester with nonlinear springs and vertical sidewall electrets,” Proceedings of PowerMEMS 2011 (Seoul, Korea, Nov 15-18 2011), pp.126-129, 2011.
8 S. D. Nguyen, E. Halvorsen and I. Paprotny, ”Bistable springs for wideband MEMS energy harvesters,” vol. 102, no. 02, Applied Physics Letters, p. 023904, Jan 2013. DOI: 10.1063/1.4775687