Two-Axis MEMS Resonant Magnetometer with Torsion Springs
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Solution Overview
Problem
Current MEMS magnetometers using the Lorentz Force for multi-axis magnetic field measurement are bulky, complex to manufacture, and have limited sensitivity, particularly when sensing magnetic fields in orthogonal directions.
Innovation Solution
A compact two-axes MEMS resonant magnetometer design featuring a freestanding rectangular frame with torsion springs, where the frame and springs are made of low resistivity, low Young's modulus material, and are capacitively coupled to minimize cross-sensitivities, allowing for efficient differential capacitive measurement of in-plane magnetic field components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If several single axis MEMS magnetometers are used to form a multi-axis magnetometer, then magnetic field measurement along multiple axes is achieved, but the footprint and device complexity increase
Solution Approach 1:
The patent combines multiple single-axis magnetometer functionalities into a single integrated MEMS structure. The device uses a common frame with multiple torsion springs, where each spring-sensing electrode pair measures magnetic field along a different axis. This merging approach achieves multi-axis measurement capability while significantly reducing the footprint compared to using separate magnetometers for each axis.
2Adaptability or versatility
If several single axis MEMS magnetometers are used to form a multi-axis magnetometer, then magnetic field measurement along multiple axes is achieved, but the manufacturing complexity increases
Solution Approach 1:
The patent merges multiple magnetometer functions into a single MEMS device with a common frame, torsion springs, and sensing electrodes. This integrated design simplifies manufacturing by reducing the number of separate components that need to be assembled and aligned, while still providing multi-axis measurement capability.
3Adaptability or versatility
If differential capacitive measurement is used for one axis and single pick-off electrode for the other axis, then multi-axis measurement is achieved, but the sensitivity is limited
Solution Approach 1:
The patent applies different sensing configurations to different axes based on their specific measurement requirements. For axes where high sensitivity is critical, differential capacitive measurement is used, while for other axes, single pick-off electrodes are employed. This localized optimization of sensing methods allows the device to achieve good overall sensitivity across all axes while maintaining multi-axis measurement capability.
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
The design achieves a smaller footprint, higher sensitivity, and reduced power consumption while maintaining ease of integration with other MEMS devices, enabling effective measurement of magnetic fields along multiple axes with improved manufacturing simplicity.
Implementation Method 1
Lorentz Force based magnetometers have a conductor that deflects in response to an interaction between an electrical current flowing through the conductor and an external magnetic field in which the conductor is placed.
Implementation Method 2
four sensing electrodes or capacitors can be present, whereby each sensing electrode can be capacitively coupled to a different side of the rectangular frame
Data Source
AI summary
A two-axes MEMS magnetometer includes, in one plane, a freestanding rectangular frame having inner walls and four torsion springs, wherein opposing inner walls of the frame are contacted by one end of only two torsion springs, each torsion spring being anchored by its other end, towards the center of the frame, to a substrate. In operation, the magnetometer measures the magnetic field in two orthogonal sensing modes using differential capacitance measurements.