MEMS Magnetic Gradient Sensor with Differential Platforms
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Solution Overview
Problem
Existing MEMS devices are not effectively capable of measuring magnetic field gradients while being insensitive to mechanical acceleration and gravitational forces, which affects their accuracy.
Innovation Solution
A MEMS structure comprising two platforms with different materials and magnetizations, suspended independently via flexible beams, allows for differential movement in response to magnetic field gradients while minimizing the impact of mechanical forces, using sensors to measure these movements and calculate the gradient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single platform with magnetic material is used to measure magnetic field, then the device can detect magnetic field strength, but it becomes sensitive to mechanical acceleration and gravitational forces
Solution Approach 1:
The device divides the measurement function into two separate platforms: one dedicated to magnetic field sensing and another to acceleration/gravitation sensing. This segmentation allows each platform to be optimized for its specific function, with the magnetic platform having magnetic material and the reference platform having non-magnetic material, thereby eliminating cross-sensitivity interference.
Solution Approach 2:
Both platforms are designed with identical physical structures, masses, and suspension mechanisms to ensure they respond identically to mechanical acceleration and gravitational forces. This homogeneity in mechanical properties allows the differential measurement to cancel out these common-mode disturbances, leaving only the magnetic field signal.
2Measurement precision
If magnetic material is added to increase magnetic sensitivity, then magnetic field detection capability improves, but the device complexity increases
Solution Approach 1:
The magnetic material is segmented and placed only on the first platform, while the second platform remains non-magnetic. This segmentation enables differential measurement where only the magnetic platform experiences magnetic forces, allowing accurate magnetic field gradient detection while keeping the overall structure relatively simple and symmetric.
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 solution provides a highly sensitive and accurate measurement of magnetic field gradients, reducing interference from mechanical acceleration and gravitational forces, thereby enhancing the signal-to-noise ratio and improving accuracy.
Implementation Method 1
a first movement of the first platform in a first direction caused by an ambient force or acceleration and/or by an ambient magnetic field gradient
Implementation Method 2
a first flexible suspension anchored to a substrate to support or suspend the first platform, while allowing a first movement of the first platform
Implementation Method 3
at least one sensor configured for measuring at least one of the following: a characteristic of the first movement, a characteristic of the second movement
Data Source
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AI summary
A MEMS structure (100) comprising: a first platform (101) comprising a first material, and further comprising an object or layer of a second, magnetic material (M2), having a first magnetization; and a second platform (102) comprising a third material, and optionally further comprising an object or layer of a fourth material (M4) being a non-magnetic material, or being magnetic and having a second magnetization different from the first magnetization; the first platform and the second platform being movable in a first direction (X) caused by an ambient acceleration and/or by an ambient magnetic field gradient; at least one sensor (51). A sensor device comprising said MEMS structure and a processing circuit (111) connected to said sensor. A method (900) of determining a magnetic field gradient using said MEMS structure.