Plastic Membrane Pressure Cell with Metallic Coating
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Solution Overview
Problem
Piezo-resistive pressure sensors face sensitivity loss and damage when exposed to aggressive substances due to swelling or dissolving of silicone encapsulation, and existing protective measures reduce pressure transmission efficiency, limiting their sensitivity and size for small pressure difference measurements.
Innovation Solution
A pressure measuring cell with a plastic membrane of uneven form, coated with a metallic alloy, and filled with a pressure transfer medium, ensuring efficient pressure transmission and chemical resistance, suitable for MEMS sensors in harsh environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicone or fluorosilicone encapsulation is used to protect the pressure sensor from aggressive substances, then chemical resistance is improved, but the sensitivity of the pressure measurement deteriorates due to swelling and embrittlement when exposed to strong acids, bases or halocarbons
Solution Approach 1:
The patent introduces a fluoropolymer coating as an intermediary layer between the aggressive external environment and the silicone encapsulation. This coating acts as a mediator that blocks harmful substances (strong acids, bases, halocarbons) from contacting the silicone, preventing swelling and embrittlement, while allowing pressure transmission to maintain sensor sensitivity.
Solution Approach 2:
The patent creates a composite protective structure combining fluorosilicone encapsulation with a fluoropolymer coating layer. This composite material system leverages the chemical resistance of fluorosilicone while adding the environmental stability and dimensional consistency of fluoropolymer, eliminating the deterioration issues of pure silicone encapsulation.
2Reliability
If protective layers or barriers are introduced to shield the pressure sensor from corrosive substances, then chemical resistance is improved, but pressure transmission efficiency deteriorates, reducing measurement sensitivity
Solution Approach 1:
The patent employs a thin fluoropolymer coating film that provides chemical protection while maintaining flexibility for effective pressure transmission. The film's thin nature and elastic properties allow it to transmit pressure changes efficiently to the sensor, avoiding the stiffness problem of metal protective layers.
Solution Approach 2:
The patent changes the material parameters of the protective layer by selecting fluoropolymer with specific elastic modulus and thickness characteristics. These parameter optimizations ensure the coating is sufficiently thin and compliant to transmit pressure efficiently while providing adequate chemical protection.
3Reliability
If metallic protective layers are used in small-dimension pressure measuring cells, then chemical resistance is improved, but pressure transmission deteriorates due to high inherent stiffness, limiting the minimum size of the cells
Solution Approach 1:
The patent replaces stiff metallic protective layers with flexible fluoropolymer thin films. This substitution enables effective pressure transmission in small-dimension cells by providing a compliant barrier that can deform with pressure changes, eliminating the stiffness limitation of metal layers in miniaturized sensors.
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 enhances sensitivity and durability of pressure measurements while maintaining chemical resistance, allowing for precise measurement of small pressure differences without compromising sensitivity or size, making it suitable for medical, pharmaceutical, and biotechnological applications.
Implementation Method 1
Piezo-resistive pressure measurement is based on the principle that the resistance value of the piezo-resistive sensors changes under deformation resulting from pressure effect.
Implementation Method 2
The internal space is filled with a pressure transfer medium which can be a liquid, a gelatinous or an oily substance or a hardened elastomer
Data Source
AI summary
The invention relates to a pressure measuring cell with a base body including an internal space, which base body comprises a first opening. A pressure sensor is arranged in the internal space of the base body and the internal space is filled with a pressure transfer medium. The pressure measuring cell further comprises an uneven membrane made from plastic. The membrane fully covers the first opening of the base body and is metallically coated at least on one of its two sides.