Optically Transduced MEMS Magnetometer with Multi-Layer Grating
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Solution Overview
Problem
Conventional MEMS Lorentz force magnetometers face limitations in sensitivity and dynamic range, leading to the need for more sensitive and versatile devices capable of accurately measuring magnetic fields across varying environments.
Innovation Solution
The development of MEMS magnetometers with optically transduced resonator displacement using multi-layer gratings that vary in dimension in response to magnetic field-induced Lorentz forces, allowing for improved sensitivity and extended dynamic range through light intensity modulation, and incorporating a bulk substrate for increased rigidity and conductive anchors for efficient current conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive or piezoelectric sensing techniques are used to detect resonator deformation, then the device structure is simple, but the sensitivity and dynamic range are limited and cross-talk occurs
Solution Approach 1:
The patent replaces conventional capacitive or piezoelectric sensing mechanisms with an optical sensing system. A light source illuminates the resonator, and photodetectors measure light intensity changes caused by resonator deflection. This optical substitution eliminates electrical cross-talk between drive and sense electrodes while providing enhanced sensitivity and dynamic range for magnetic field measurement.
2Strength
If the resonator is made with thicker bulk substrate to increase rigidity and conductive cross-section, then the mechanical stability and current conduction improve, but the device volume increases
Solution Approach 1:
The patent applies different substrate thicknesses to different regions of the resonator structure. The bulk substrate is used specifically at anchor points and support regions where mechanical rigidity and electrical conductivity are needed, while other areas maintain thinner profiles. This localized application of thick substrate provides the necessary strength and conductive cross-section without uniformly increasing the entire resonator volume.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances sensitivity and reduces crosstalk, enabling precise magnetic field measurements across a wide range of field strengths and environments, surpassing the limitations of conventional techniques.
Implementation Method 1
Lorentz forces form in the resonator inducing the resonator to mechanically deform
Implementation Method 2
an alternating current (AC) is applied to induce a mechanical resonance in a suspended member
Implementation Method 3
a first grating extending from the support and disposed over the resonator, a second grating in the resonator overlapping the first grating to form a multi-layer grating having apertures that vary dimensionally in response to deflection
Data Source
AI summary
MEMS magnetometers with optically transduced resonator displacement are described herein. Improved sensitivity, crosstalk reduction, and extended dynamic range may be achieved with devices including a deflectable resonator suspended from the support, a first grating extending from the support and disposed over the resonator, a pair of drive electrodes to drive an alternating current through the resonator, and a second grating in the resonator overlapping the first grating to form a multi-layer grating having apertures that vary dimensionally in response to deflection occurring as the resonator mechanically resonates in a plane parallel to the first grating in the presence of a magnetic field as a function of the Lorentz force resulting from the alternating current. A plurality of such multi-layer gratings may be disposed across a length of the resonator to provide greater dynamic range and/or accommodate fabrication tolerances.