MEMS Electret Generator for Energy Harvesting

J. Nakano, S. Kim, H. Xie, J. Lu, M. Adachi, K. Kittipaisalsilpa and Y. Suzuki


Energy harvesting is now attracting much attention targeting at their application to automotive sensors, implantable medical equipments and network nodes for structural health monitoring. Final goal of the present study is to develop vibration-driven MEMS power generation device, which produces electricity from environmental low-frequency vibration.

Whereas electromagnetic induction is used for converting kinetic energy to electricity in macro scale, electrostatic induction is superior in micro scale, where relative speed remains small. In the present study, we employ electrostatic induction using polymer electrets as the power generation principle.

So far, we develop a new fluorinated amorphous polymer material based on CYTOP by adding animosilane and demonstrate extremley-high surface charge density above 2 mC/m^2 (at the film thickness of 15 um), which is up to 5 times larger than that of conventional electret materials. It is also found that nano clusters are formed in the animonsilane-doped CYTOP film by local phase separation between the polymer matrix and the addtives. These clusters should work as the charge trapping site in the CYTOP films.

We develop a novel MEMS process for Parylene high-aspect ratio structure (HARS) for soft but robust HARS spring. We also propose a passive gap-spacing control method using electret in order to avoid stiction between top and bottom substrates. Out-of-plane repulsive force is successfully demonstrated with our early prototype both in air and liquid. By using the present electret-based levitation method to keep the air gap, a MEMS electret generator has been developed for energy harvesting applications. Dual-phase electrode arrangement is adopted in order to reduce the horizontal electrostatic damping force. With the present prototype, the total power output of 6 µW has been obtained at an acceleration of 1.4 G with 40 Hz. In addition, with the aid of a non-linear polymer spring system, power generation at a broad frequency range of 16-40 Hz has also been demonstrated. We have also developed an early prototype of battery-less sensor network node with the MEMS energy harvester and accomplished intermittent wireless data transmission.

For eletret transducers, charging techniques are important as well as the electret material. In the present study, novel photoionization charge technologies with soft X-ray and vacuum UV have also been developed for through-substrate charging and charging "vertical electrets" such as the side wall of comb drives. With the aid of the soft X-ray charging technique, new types of electret generator using comb fingers and trench-filled piezoelectric polymer electret are also proposed.

In addition, electrostatic power generation system from unsteady thermal field is under development.

Sponsor: Next Generation World-Leading Researchers (NEXT Program) (JSPS) [PI: Y. Suzuki]

Concept of MEMS Electret Generator

Nano cluster formed in aminosilane-doped CYTOP film visualized with trapping mode AFM (Kashiwagi et al., 2011)

MEMS Electret Generator with Parylene High-aspect-ratio Springs (Miki et al., IEEE MEMS2010)

Prorotype Battery-less Sensor Network Node (Matsumoto et al., PowerMEMS 2011)

Recent Reports

Review Article

  • Suzuki, Y.,
    "Electrostatic/Electret-based Harvesters,"
    in Micro Energy Harvesting, eds. Briand, D., Yeatman, E., and Roundy, S., Wiley-VCH, pp. 149-174 (2015).
  • Suzuki, Y.,
    "Electret-based Vibration Energy Harvesting for Sensor Network,"
    Invited talk, 18th Int. Conf. Solid-state Sensors, Actuators, and Microsystems (Transducers ’15), Anchorage, pp. 43-46, (2015).
  • Suzuki, Y.,
    "Recent Progress in MEMS Electret Generator for Energy Harvesting,"
    IEEJ Trans. Electr. Electr. Eng., Vol. 6, No. 2, pp. 101-111 (2011).
    (doi: 10.1002/tee.20631)

Electret-based MEMS Energy Harvester

  • Matsumoto, K., Saruwatari, K., and Suzuki, Y.,
    Vibration-powered Battery-less Sensor Node Using Electret Generator,”
    11th Int. Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2011), Seoul, pp. 134-137 (2011).
  • Suzuki, Y., Miki, D., Edamoto, M., and Honzumi, M.,
    “A MEMS Electret Generator With Electrostatic Levitation For Vibration-Driven Energy Harvesting Applications,”
    J. Micromech. Microeng., Vol. 20, Issue. 10, No. 104002, 8pp, (2010).

Electret-based Rotational Energy Harvester

  • Nakano, J., Komori, K., and Hattori, Y., and Suzuki, Y.,
    MEMS Rotational Electret Energy Harvester for Human Motion,”
    15th Int. Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2015), Boston, (2015). Also, J. Phys.: Conf. Ser., Vol. 660, No. 012052 (2015) (Best Paper Award).

Modeling of Electret Generator for Higher Power Density

  • Kittipaisalsilpa, K., Kato, T., and Suzuki, Y.,
    Liquid-crystal-enhanced Electret Power Generator,”
    29th IEEE Int. Conf. Micro Electro Mechanical Systems (MEMS’16), Shanghai, pp. 37-40 (2016).
  • Chen, R., and Suzuki, Y.,
    “Suspended Electrodes for Reducing Parasitic Capacitance in Electret Energy Harvesters,”
    J. Micromech. Microeng., Vol. 23, Issue 12, 125015 (2013).
  • Miki, D., Suzuki, Y., and Kasagi, N.,
    "Effect of Nonlinear External Circuit on Electrostatic Force of Micro Electret Generator,"
    15th Int. Conf. Solid-state Sensors, Actuators, and Microsystems (Transducers' 09), Denver, pp. 636-639 (2009).
  • Marboutin, C., Suzuki, Y., and Kasagi, N.,
    "Optimal Design of Micro Electret Generator for Energy Harvesting,"
    7th Int. Workshop Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2007), Freiburg, pp. 141-144 (2007).

High-performance Polymer Electret Film

  • Kashiwagi, K., Okano, K., Miyajima, T., Sera, Y., Tanabe, N., Morizawa, Y., and Suzuki, Y.,
    “Nano-cluster-enhanced High-performance Perfluoro-polymer Electrets for Micro Power Generation,”
    J. Micromech. Microeng., Vol. 21, Issue 12, No. 125016, (2011).
  • Sakane, Y., Suzuki, Y., and Kasagi, N.,
    "Development of High-performance Perfluorinated Polymer Electret and Its Application to Micro Power Generation,"
    J. Micromech. Microeng., Vol. 18, No. 10, 104011, 6pp. (2008).
    (doi: 10.1088/0960-1317/18/10/104011)
  • Tsutsumino, T., Suzuki, Y., Kasagi, N., and Sakane, Y.,
    "Seismic Power Generator Using High-Performance Polymer Electret, "
    19th IEEE Int. Conf. Micro Electro Mechanical Systems (MEMS2006), Istanbul, pp.98-101 (2006).

Low-resonant-frequency MEMS Seismic Structure

New Charging Method Using Photoionization

  • Kim, S., Fu, Q., Hagiwara, K., and Suzuki, Y.,
    Development of A Pre-packaged MEMS Electret Energy Harvester Before Charging,”
    14th Int. Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2014), Awaji, (2014). Also, J. Phys.: Conf. Ser., Vol. 557, No. 012063 (2014).
  • Hagiwara, K., Goto, M., Iguchi, Y., Tajima, T., Yasuno, Y., Kodama, H., Kidokoro, K., and Suzuki, Y.,
    “Electret Charging Method Based on Soft X-ray Photoionization for MEMS Applications,”
    Trans. IEEE, Dielectr. Electr. Insul., Vol. 19, No. 4, pp. 1291-1298 (2012).
  • Honzumi, M., Hagiwara, K., Iguchi, Y., and Suzuki, Y.,
    "High-Speed Electret Charging Method Using Vacuum UV Irradiation,"
    Appl. Phys. Lett., Vol. 98, 052901, (2011).
    (doi: 10.1063/1.3548866)

MEMS Energy Harvester Using Vertical Electret

Trench-filled Piezoelectric Polymer Electret

Electret-based Energy Harvesting from Unsteady Temperature Change

Last update: 2016-11-11