Spray-coated electret materials with enhanced stability in a harsh environment for an MEMS energy harvesting device

Anxin Luo; Yixin Xu; Yulong Zhang; Mi Zhang; Xiaoqing Zhang; Yan Lu; Fei Wang

doi:10.1038/s41378-021-00239-0

Spray-coated electret materials with enhanced stability in a harsh environment for an MEMS energy harvesting device

Microsyst Nanoeng. 2021 Feb 9:7:15. doi: 10.1038/s41378-021-00239-0. eCollection 2021.

Authors

Anxin Luo^#^{1

2

3

4}, Yixin Xu^#⁵, Yulong Zhang⁶, Mi Zhang⁷, Xiaoqing Zhang⁷, Yan Lu^{2

3}, Fei Wang^{1

4}

Affiliations

¹ School of Microelectronics, Southern University of Science and Technology, 518055 Shenzhen, China.
² State Key Laboratory of AMS-VLSI, Institute of Microelectronics, University of Macau (UM), 999078 Macao, China.
³ Department of Electrical and Computer Engineering, FST, UM, 999078 Macao, China.
⁴ Engineering Research Center of Integrated Circuits for Next-Generation Communications, Ministry of Education, Southern University of Science and Technology, 518055 Shenzhen, China.
⁵ Department of Mechanical Engineering, Boston University, Boston, MA USA.
⁶ College of New Materials and New Energies, Shenzhen Technology University, 518118 Shenzhen, China.
⁷ Shanghai Key Laboratory of Special Artificial School of Physics Science and Engineering, Tongji University, 200092 Shanghai, China.

^# Contributed equally.

Abstract

The charge stability of electret materials can directly affect the performance of electret-based devices such as electrostatic energy harvesters. In this paper, a spray-coating method is developed to deposit an electret layer with enhanced charge stability. The long-term stability of a spray-coated electret is investigated for 500 days and shows more stable performance than a spin-coated layer. A second-order linear model that includes both the surface charge and space charge is proposed to analyze the charge decay process of electrets in harsh environments at a high temperature (120 °C) and high humidity (99% RH); this model provides better accuracy than the traditional deep-trap model. To further verify the stability of the spray-coated electret, an electrostatic energy harvester is designed and fabricated with MEMS (micro-electromechanical systems) technology. The electret material can work as both the bonding interface and electret layer during fabrication. A maximum output power of 11.72 μW is harvested from a vibrating source at an acceleration of 28.5 m/s². When the energy harvester with the spray-coated electret is exposed to a harsh environment (100 °C and 98% RH), an adequate amount of power can still be harvested even after 34 h and 48 h, respectively.

Keywords: Electrical and electronic engineering; Physics.