MEMS Pressure Sensor Linkage for In-Plane Capacitive Detection
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Solution Overview
Problem
MEMS and NEMS devices for pressure measurement, such as microphones, face challenges due to the presence of counter electrodes which cause acoustic resistance and degrade signal quality, and existing solutions like piezoelectric detection or vacuum electrical transduction have limitations in capacitive detection capacity and structural constraints.
Innovation Solution
A mechanical connection that transforms out-of-plane movement of a movable part into a translation movement in a plane, allowing for capacitive detection without reducing capacitive detection capacity, using a lever arm with specific connections to transmit and rotate the movement effectively, and defining air gaps for improved capacitive transduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the density and size of holes in the counter electrode are increased to reduce acoustic resistance, then acoustic resistance is reduced, but the surface area is reduced which proportionally reduces capacitive detection
Solution Approach 1:
The patent removes the counter electrode from the acoustic path entirely by using a membrane structure that allows acoustic access without requiring a perforated counter electrode. The movable electrode is positioned such that the membrane can move freely without being blocked by counter electrode holes, thus eliminating acoustic resistance while preserving capacitive detection surface area.
Solution Approach 2:
The patent introduces a membrane as an intermediary element between the acoustic environment and the capacitive detection system. This membrane serves as both the acoustic interface and the movable electrode, eliminating the need for a separate counter electrode and resolving the conflict between acoustic transparency and capacitive detection area.
2Power
If the membrane surface area is increased to collect more piezoelectric charges, then the electrical signal is increased, but the structure size and cost increase and more air is displaced creating opposing force
Solution Approach 1:
The patent changes the detection mechanism from piezoelectric to capacitive, fundamentally altering how electrical signals are generated. In capacitive detection, the signal strength depends on the change in capacitance rather than the amount of piezoelectric material, allowing for smaller membrane areas while maintaining or improving signal quality.
Solution Approach 2:
The patent replaces the piezoelectric mechanical-to-electrical transduction system with a capacitive electrical field-based system. This substitution eliminates the need for thick piezoelectric layers and large membrane areas, as capacitive detection can achieve sufficient signal strength with smaller structures through precise measurement of capacitance changes.
3Measurement precision
If a lever arm is used to transform out-of-plane movement into translation, then capacitive detection capacity is maintained, but the device complexity increases
Solution Approach 1:
The patent makes the membrane serve multiple functions simultaneously: it acts as both the acoustic interface and the movable electrode in the capacitive sensor. This multi-functionality eliminates the need for separate mechanical linkage components like lever arms, as the membrane itself directly provides the capacitive detection function while responding to acoustic pressure.
Solution Approach 2:
The patent merges the acoustic membrane function and the capacitive sensor electrode function into a single integrated structure. By combining these functions, the patent eliminates the need for separate mechanical transformation components, reducing device complexity while maintaining measurement precision.
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
Enhances capacitive detection capacity while minimizing the impact of counter electrode-related issues, allowing for more efficient pressure variation measurement with improved signal quality and reduced structural constraints.
Implementation Method 1
a lever arm; a first link connecting the moving part to a first end of the lever arm, said first link being adapted to transmit the out-of-plane displacement of said moving part to said first end of the lever arm while allowing out-of-plane rotation of the lever arm
Implementation Method 2
means for detecting said displacement or deformation comprising at least one movable element... allowing for capacitive detection without reducing capacitive detection capacity
Data Source
Figure 1A~1B
Figure 2~3B
Figure 4A~4B
AI summary
The invention relates to a mechanical link for a microelectromechanical and/or nanoelectromechanical device for measuring a pressure variation, said device comprising a fixed part extending along a principal plane, a movable part capable of moving or deforming in an out-of-plane direction under the effect of a pressure variation, and means for detecting said displacement or deformation comprising at least one movable element, the mechanical link comprising: - a lever arm; - a first link connecting the movable part to a first end of the lever arm, said first link being adapted to transmit the out-of-plane displacement of said movable part to said first end of the lever arm while allowing out-of-plane rotation of said lever arm around a direction of rotation (Y);- a second link connected to the second end of the lever arm and configured to allow mainly out-of-plane rotation of the lever arm around an axis of rotation extending along the direction of rotation; - a third link connecting the lever arm to the detection means at a given distance from the axis of rotation along the out-of-plane direction, said third link being adapted to transform the rotation of said lever arm around said axis of rotation into a translation in the plane of at least one moving element along a direction of translation.