Q-factor Optimisation of Diamagnetically Levitating Plate

Abstract

From levitating living organisms to developing high-Q resonators, diamagnetic levitation has become a powerful technique to mechanically isolate objects. Its ability to work at room temperature without power consumption and simple setups has found many applications in precision measurements, including accelerometers, MEMS devices, mass sensors, and motion stages. By using the strong diamagnetic properties of materials like pyrolytic graphite, both micro- and macro-scale objects can be stably levitated. This allows for systems that reduce mechanical losses and provide high isolation. Therefore, diamagnetic levitation is ideal for creating ultra-low dissipation mechanical systems with high quality factors (Q-factor). However, a key challenge remains, the damping caused by eddy currents that occur due to motion through a changing magnetic fields. These currents dissipate energy and limit the performance of these levitated systems by lowering their Q-factor.
This thesis explores the optimization of pyrolytic graphite-based composite resonators to enhance the Q-factor. By combining finite element method (FEM) simulations with Multi-Objective Particle Swarm Optimization (MOPSO), we investigate how plate geometry and segmentation can suppress eddy currents and reduce damping. Composite plates with insulating epoxy are fabricated and levitated over a 2x2 array of NdFeB permanent magnets. Experimental validations demonstrate a significant increase in Q-factor, particularly when combining segmentation and optimised shape, reaching values up to 420,000. This work contributes to the advancement of high-Q levitating resonators and highlights the importance of geometry and materials in achieving ultra-low dissipation.