Lorentz force based resonant MEMS magnetic-field sensor with optical readout

• A Lorentz force based resonant MEMS magnetic-field sensor with optical readout has been designed, fabricated and tested.
• The rotating mirror is designed based on flexible springs and a mirror membrane, and fabricated by using bulk micromachining.
• The sensor demonstrated high sensitivity in atmospheric pressure, and controllable sensitivity by varying the AC bias.
• Operating with a maximum coil current (50 mA), the sensor is capable of a noise limited resolution of 400 pT with operation.

A Lorentz force based resonant MEMS magnetic-field sensor with optical readout has been demonstrated. The sensor employs a micromachined resonant mirror that is excited by the Lorentz force generated between a sinusoidal current flowing through a coil on the mirror and the incident magnetic field. The amplitude of the rotation angle is detected by the optical positioning system and external electronics. Sensor sensitivity is controlled by the control of the coil bias current, and shows linear sensitivity with incident field. The resolution and noise floor is 0.4 nT and 1.78 nT/√Hz respectively at 53 mHz bandwidth, for a coil bias current of 50 mArms and operation at atmospheric pressure. This sensor is suitable for various applications due to wide measurement range, from sub-nanoTesla fields to several Tesla.