Corrugated Sidewall Diaphragm Sensor for Pressure Measurement
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Solution Overview
Problem
The challenge lies in fabricating a three-dimensional capacitive pressure sensor with a large diaphragm suspended over a cavity, as conventional methods face issues with diaphragm collapse due to weak sidewall support and inconsistent deflection under pressure, primarily caused by stiction and intermolecular forces during the fabrication of the cavity sidewall.
Innovation Solution
The solution involves a diaphragm-based sensor design with a corrugated wall extending between the diaphragm and a base layer, where the diaphragm is suspended over a cavity, and the cavity is filled with a fluid of high dielectric constant, enhancing structural rigidity and sensitivity. The corrugated wall features a plurality of ridges and grooves, increasing the stiffness of the sidewall, and the diaphragm and base electrodes are encapsulated in parylene layers for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large diaphragm is used to increase sensor resolution for low-pressure range measurement, then measurement precision is improved, but the diaphragm becomes more prone to collapse due to weak sidewall support
Solution Approach 1:
The patent transforms the flat, weak sidewall into a three-dimensional corrugated structure with ridges and grooves. This dimensional change from a simple cylindrical cavity to a corrugated sidewall structure provides enhanced mechanical support and structural rigidity, preventing diaphragm collapse while maintaining the large diaphragm size needed for high-resolution low-pressure measurement
Solution Approach 2:
The corrugated sidewall introduces curved geometric features (ridges and grooves) that naturally distribute and reinforce structural loads. The curved geometry of the corrugations provides inherent mechanical strength, preventing the diaphragm from collapsing under its own weight or during operation, thus maintaining diaphragm stability for reliable measurement
2Ease of manufacture
If the cavity sidewall is made thinner to maintain flexibility, then ease of manufacture is improved, but the sidewall strength decreases leading to diaphragm collapse
Solution Approach 1:
Instead of increasing sidewall thickness, the patent adds dimensional complexity through corrugations (ridges and grooves) on the sidewall surface. This approach maintains the thin-walled flexible structure while the corrugated geometry provides the necessary mechanical strength to prevent collapse, resolving the contradiction between thin-walled ease of manufacture and structural strength
Solution Approach 2:
The patent employs a thin-walled cavity structure with corrugated sidewalls that maintains flexibility while providing sufficient strength. The corrugated thin film structure acts as a flexible yet strong container, allowing the sidewall to remain thin for ease of manufacture and biocompatibility while preventing diaphragm collapse through the geometric reinforcement of the corrugations
3Ease of manufacture
If conventional smooth sidewall cavity structure is used, then ease of manufacture is improved, but structural rigidity is insufficient leading to inconsistent diaphragm deflection
Solution Approach 1:
The patent adds dimensional complexity to the sidewall by introducing corrugations (ridges and grooves) rather than using a smooth surface. This corrugated structure significantly enhances structural rigidity and provides consistent mechanical support for the diaphragm, ensuring uniform deflection characteristics during operation while remaining compatible with standard microfabrication techniques
Solution Approach 2:
The corrugated sidewall divides the continuous sidewall surface into segmented ridges and grooves. This segmentation creates multiple structural support elements distributed around the cavity, providing enhanced and more uniform structural rigidity compared to a smooth sidewall, while still maintaining ease of manufacture through conventional patterning processes
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 reduces diaphragm collapse and enhances sensitivity by maintaining structural integrity and consistent deflection under varying pressures, achieving a 64-fold increase in capacitance measurement sensitivity when using a high-dielectric fluid like propylene carbonate, thus addressing the limitations of conventional sensors.
Implementation Method 1
The cavity can be filled with a fluid which has a dielectric constant greater than 1... achieving a 64-fold increase in capacitance measurement sensitivity when using a high-dielectric fluid like propylene carbonate
Implementation Method 2
The corrugated wall can include a plurality of ridges alternating with a plurality of grooves... the corrugated wall features a plurality of ridges and grooves, increasing the stiffness of the sidewall
Implementation Method 3
The deflection of the diaphragm under pressure is related to the applied pressure... The deflection of a circular diaphragm due to applied pressure is depicted by
Data Source
AI summary
A diaphragm-based sensor includes a deflectable diaphragm, a base layer opposite the diaphragm, and a corrugated wall extending between the diaphragm and the base layer. The diaphragm is suspended over a cavity enclosed by the diaphragm, the base layer and the corrugated wall. The diaphragm includes a first electrode and the base layer includes a second electrode such that a capacitance between the first and second electrodes changes when the diaphragm is deflected relative to the cavity.