Analysis of multi-direction low-frequency vibration energy harvester using diamagnetic levitation

Abstract

This paper presents theoretical analysis and verification of a micro vibration energy harvester based on magnetic levitation using diamagnetic structures. The analysis verifies that diamagnetic material experiences anti-magnetic force in mag- netic field and that it can be used for stable magnetic levitation. This study proposes a novel design that is comprised of a lifting permanent magnet, an upper pyrolytic graphite sheet, a floating permanent magnet, and a lower pyrolytic graphite sheet, with copper spiral coils formed on the two pyrolytic graphite sheets. The gravity of the floating permanent magnet is balanced by the attractive force between the lifting and floating magnets. The diamagnetic force exerted on the levitated magnet by the two pyrolytic graphite sheets serves as a restoring force, forcing the floating permanent magnet return to the equilibrium position. Through finite element analysis, the maximum movable range of the floating magnet is defined to be 1.3 mm. Comparative anal- ysis of the attractive magnetic force and the anti-magnetic force is performed to determine the key parameters of the structure. The characteristics of vertical and horizontal motion of the magnet are also studied in detail. The results validate the effec- tiveness of the proposed design for harvesting multi-dimensional, low-frequency vibration energy. The diamagnetic levitation mechanism without conventional mechanical suspensions eliminates loss of vibration energy and resultant thermal issues. The system is potentially promising, through further miniaturization, in providing sustainable power for micro-electro-mechanical systems.