MEMS Acceleration Sensor Capacitor Lever Amplification
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Solution Overview
Problem
The sensitivity of parallel plate capacitors in MEMS acceleration sensors is low due to their small change range, making existing sensors unsatisfactory for accurate acceleration measurement.
Innovation Solution
The design incorporates a lever mechanism using silicon-made sensitive elements and connecting arms, with cantilever beams that amplify strain, increasing the capacitance change by leveraging the force applied to the sensitive elements, thereby enhancing the sensor's sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a parallel plate capacitor is used in a MEMS acceleration sensor, then the sensor has simple processing and low parasitic capacitance influence, but the sensitivity is low due to small change range
Solution Approach 1:
The patent introduces a lever arm that extends in a direction perpendicular to the traditional displacement direction, creating a dimensional transformation. The sensitive element moves in one dimension while the lever arm amplifies this motion in another dimension, increasing the effective displacement range and capacitance change without complicating the basic parallel plate structure
Solution Approach 2:
The lever arm acts as an intermediary mechanism between the sensitive element and the fixed electrode. It mediates the small displacement of the sensitive element by converting it into a larger effective displacement through rotational motion, thereby amplifying the capacitance change while maintaining the simple parallel plate capacitor structure
2Reliability
If the parallel plate capacitor structure is used, then parasitic capacitance and edge effect are reduced, but the capacitance change range is small leading to low sensitivity
Solution Approach 1:
By introducing the lever arm that rotates perpendicular to the primary displacement direction, the patent transforms small linear displacements into larger effective displacements in a different dimensional plane, thereby increasing capacitance change range while preserving the parallel plate structure's resistance to parasitic capacitance
Solution Approach 2:
The patent changes the geometric parameters of the capacitor system by introducing a lever arm with specific length and orientation. This parameter change amplifies the effective displacement without altering the fundamental parallel plate configuration, thus increasing capacitance change while maintaining reliability against parasitic effects
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 design significantly increases the displacement of the polar plates under acceleration, resulting in a greater capacitance change, making the acceleration sensor more sensitive and effective.
Implementation Method 1
The parallel plate capacitor can amplify a strain of the sensitive element by a leverage effect formed by the element connecting arm, the sensitive element and the first polar plate of the capacitor
Implementation Method 2
an anchoring base disposed on a substrate where the second polar plate is located, the anchoring base is connected to the element connecting arm via a cantilever beam
Implementation Method 3
the capacitor can be more susceptible to force and generates capacitance change
Data Source
Figure 1~2
Figure 3
AI summary
A parallel plate capacitor includes a first polar plate (10), and a second polar plate disposed opposite to the first polar plate (10). The parallel plate capacitor further includes at least a pair of sensitive units disposed on a substrate forming the first polar plate (10); the sensitive units includes sensitive elements (21a, 21b, 22a, 22b) and element connecting arms (23a, 23b, 24a, 24b) connecting the sensitive elements (21a, 21b, 22a, 22b) to the first polar plate (10). The parallel plate capacitor further includes anchoring bases (30, 31, 32, 33) disposed on a substrate where the second polar plate is located; the anchoring bases (30, 31, 32, 33) are connected to the element connecting arms (23a, 23b, 24a, 24b) via cantilever beams (30a, 30b, 31a, 31b, 32a, 32b, 33a, 33b); each element connecting arm (23a, 23b, 24a, 24b) is connected to at least two anchoring bases (30, 31, 32, 33), which are symmetric with respect to the element connecting arm. The parallel plate capacitor is more likely to be influenced by an external factor, thus being more likely to experience capacitance change. An acceleration sensor including the parallel plate capacitor is also provided.