MAGNETICALLY ACTUATED MICROMIRRORS FOR ELECTROMAGNETIC NDE

摘要

Micro-electromechanical systems (MEMS) are the small integrated devices or systems that combine electrical and mechanical components. They can be used for novel sensors, actuators and systems in many applications. In order to measure magnetic field with high sensitivity and high spatial resolution, a 2D magnetic field sensing system employing magnetically actuated micromirrors is proposed. The micromirrors are based on silicon material with electrodeposited magnetic materials, such as the permalloy (Ni_(77)Fe_(14)Cu_5Mo_4), for magnetic interaction and force generation. A small disturbance of magnetic field due to a hidden defect in a magnetically permeable material will cause the magnetic micromirror to deflect, which can be detected optically for non-destructive evaluation (NDE) application, which is very important for structural integrity. A series of numerical simulations were conducted with Multiphysics Modelling Package FEMLAB 3.1 and MEMS modelling software IntelliSuite before fabrication of the micromirrors. Based on the simulation results, the interaction of the magnetic force with various dimensions of the magnetic micromirrors is obtained. Depending on the size of micromirror and the thickness of electrodeposited magnetic material, deflection of the micromirror up to 100μm can be realised at the magnetic field as small as 0.1 Gauss. Furthermore, the force generated by different ferromagnetic materials including soft and hard magnetic materials was also calculated. By analysis and investigation into the interaction of the magnetic force with the properties and dimension of the magnetic material, the proposed magnetically actuated micromirror is optimized.