MEMS Torsional Hinge Cavity for Magnet-Coil Coupling
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Solution Overview
Problem
The magnetic coupling between a permanent magnet and an electrical coil in torsional hinged MEMS devices diminishes with increasing distance, leading to reduced drive force or sensing accuracy, necessitating a method to reduce this distance without compromising structural strength or increasing complexity/cost.
Innovation Solution
The design incorporates an elongated hinge layer with a cavity in the coil support structure to position the permanent magnet closer to the electrical windings, optimizing magnetic coupling by minimizing the distance between the magnet and coil while maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the distance between the permanent magnet and the electrical coil is reduced to improve magnetic coupling, then the drive force or sensing accuracy is improved, but the structural strength may be compromised and the device complexity increases
Solution Approach 1:
The patent positions the permanent magnet in a cavity on the back side of the hinge layer, while the electrical coil is positioned on the front side, creating a face-to-face arrangement through the thickness of the hinge layer. This three-dimensional positioning reduces the magnetic distance without compromising the planar structural integrity of the device.
Solution Approach 2:
The permanent magnet is nested within a cavity formed in the coil support structure, allowing the magnet to be positioned in close proximity to the electrical coil windings. This nesting arrangement maximizes magnetic coupling while maintaining the structural framework of the device.
2Force
If the distance between the permanent magnet and the electrical coil is reduced to improve magnetic coupling, then the drive force or sensing accuracy is improved, but the device complexity and cost increase
Solution Approach 1:
The hinge layer serves multiple functions: it provides the torsional hinge mechanism for pivoting, supports the permanent magnet on its back side, and allows the electrical coil to be positioned on the front side. This multi-functionality reduces the need for additional structural elements, thereby limiting complexity increase.
Solution Approach 2:
The support structures for the magnet and the electrical coil are merged into a single integrated coil support structure with a cavity. This integration reduces the number of separate components and simplifies the overall device architecture while achieving close magnetic coupling.
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 configuration enhances the magnetic coupling, improving the drive force or sensing accuracy by maintaining the structural strength and cost-effectiveness of the device.
Implementation Method 1
Magnetic coupling between a permanent magnet on a torsional hinged structure and an electrical coil positioned close to the permanent magnet may be used to provide a drive force to pivot or oscillate the device, or the electrical coil may generate an output signal as the magnet moves with respect to the coil.
Data Source
AI summary
A pivoting device such as a MEMS mirror provides improved coupling between a permanent magnet on the device and an adjacent electrical coil that may provide a drive force or position sensing. The improved coupling is obtained by forming a cavity in the coil structure. The cavity receives the permanent magnet such that the spacing between the magnet and the electrical windings or coil is at a minimum.