A MEMS torsion magnetic sensor with reflective blazed grating integration

• Published in: Journal of micromechanics and microengineering Vol. 26; no. 7; pp. 75004 - 75015
• Main Authors: Long, Liang, Zhong, Shaolong
• Format: Journal Article
• Language: English
• Published: IOP Publishing 06.06.2016
• Subjects: blazed grating; magnetic sensor; MEMS; permanent magnet
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/26/7/075004

A novel magnetic sensor based on a permanent magnet and blazed grating is presented in this paper. The magnetic field is detected by measuring the diffracted wavelength of the blazed grating which is changed by the torsion motion of a torsion sensitive micro-electromechanical system (MEMS) structure with a permanent magnet attached. A V-shape grating structure is obtained by wet etching on a (1 0 0) SOI substrate. When the magnet is magnetized in different directions, the in-plane or out-of-plane magnetic field is detected by a sensor. The MEMS magnetic sensor with a permanent magnet is fabricated after analytical design and bulk micromachining processes. The magnetic-sensing capability of the sensor is tested by fiber-optic detection system. The result shows the sensitivities of the in-plane and out-of-plane magnetic fields are 3.6 pm μT−1 and 5.7 pm μT−1, respectively. Due to utilization of the permanent magnet and fiber-optic detection, the sensor shows excellent capability of covering the high-resolution detection of low-frequency signals. In addition, the sensitive direction of the magnetic sensor can be easily switched by varying the magnetized direction of the permanent magnet, which offers a simple way to achieve tri-axis magnetic sensor application.