Double-Deck Metal Solenoids 3D Integrated in Silicon Wafer for Kinetic Energy Harvester.

Nianying Wang,Xinxin Li,Jiebin Gu,Changnan Chen,Ruofeng Han

doi:10.3390/mi12010074

Abstract

A silicon-chip based double-deck three-dimensional (3D) solenoidal electromagnetic (EM) kinetic energy harvester is developed to convert low-frequency (<100 Hz) vibrational energy into electricity with high efficiency. With wafer-level micro electro mechanical systems (MEMS) fabrication to form a metal casting mold and the following casting technique to rapidly (within minutes) fill molten ZnAl alloy into the pre-micromachined silicon mold, the 300-turn solenoid coils (150 turns for either inner solenoid or outer solenoid) are fabricated in silicon wafers for saw dicing into chips. A cylindrical permanent magnet is inserted into a pre-etched channel for sliding upon external vibration, which is surrounded by the solenoids. The size of the harvester chip is as small as 10.58 mm × 2.06 mm × 2.55 mm. The internal resistance of the solenoids is about 17.9 Ω. The maximum peak-to-peak voltage and average power output are measured as 120.4 mV and 43.7 . The EM energy harvester shows great improvement in power density, which is 786 and the normalized power density is 98.3 . The EM energy harvester is verified by experiment to be able to generate electricity through various human body movements of walking, running and jumping. The wafer-level fabricated chip-style solenoidal EM harvesters are advantageous in uniform performance, small size and volume applications.

Highlights

Great efforts have been made to develop small-size and low-power electronic microsystems for wearable applications [1,2], wireless sensors [3,4], wireless security-monitoring microsystems [5], etc
This paper proposes double-deck three-dimensional (3D) metal solenoids that are fabricated with a silicon-wafer based integration method and can generate much larger power density than single-layer solenoid structure [13]
A cylindrical permanent magnet is inserted into the central channel of the solenoid that was pre-formed in the silicon substrate with the mechanical systems (MEMS) technique

Summary

Introduction

Great efforts have been made to develop small-size and low-power electronic microsystems for wearable applications [1,2], wireless sensors [3,4], wireless security-monitoring microsystems [5], etc. Harvesting energy from the environment and converting it into electrical power is a promising alternative to conventional power sources. Various ambient energy sources existing in the environment, such as vibration energy, solar energy, thermal energy and so on [6] have been tried for conversion into electrical power. Among these environmental energy sources, vibration energy has great advantage in broad accessibility, which is abundant in the environment and distributed in a wide frequency range, especially in low frequencies [7]. As one of the self-powered solutions of electronic micro-systems, various kinetic energy harvesters are explored extensively to convert ambient vibration energy to electricity

Methods

Results

Conclusion