Passive Wireless MEMS Pressure Sensor for Harsh Environments
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Solution Overview
Problem
Conventional sensors fail to accurately measure pressure in harsh environments such as high-temperature gas turbines due to limitations in surviving extreme conditions like high temperatures, vibrations, and chemical exposure, which can lead to component failures from high cycle fatigue.
Innovation Solution
A passive wireless microelectromechanical system (MEMS) capacitive-type pressure sensor using radio frequency electromagnetic radiation, with a diaphragm and conductive ground plane, operates by reflecting electromagnetic waves to determine pressure changes, and is constructed with materials like sapphire and platinum for high-temperature compatibility, allowing for both static and dynamic pressure measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sensors are used in harsh environments, then they can provide pressure measurements, but they fail to survive extreme conditions like high temperatures, vibrations, and chemical exposure
Solution Approach 1:
The sensor employs a composite structure combining sapphire diaphragm (for high temperature and chemical resistance) with silicon MEMS technology (for precise pressure sensing). This composite approach allows the sensor to survive harsh environments while maintaining measurement accuracy, resolving the contradiction between reliability and adaptability to extreme conditions.
Solution Approach 2:
The patent replaces conventional wired electrical connections with wireless electromagnetic communication. The sensor uses a wireless transmitter to send pressure data remotely, eliminating physical wire connections that would fail in harsh environments. This substitution enables the sensor to operate reliably at high temperatures where traditional electrical connections would fail.
2Measurement precision
If passive wireless MEMS sensor is used, then accurate pressure measurement is achieved in harsh environments, but the sensor requires electromagnetic wave interaction and resonant frequency tuning
Solution Approach 1:
The sensor utilizes the harsh environment's electromagnetic waves (e.g., radio frequency waves in gas turbines) as both the operating medium and the measurement stimulus. The sensor passively reflects these existing waves with frequency shifts encoding pressure information, eliminating the need for separate excitation sources or complex wiring. This self-service approach reduces device complexity while maintaining high measurement precision.
Solution Approach 2:
The sensor employs resonant vibration of the sapphire diaphragm at specific frequencies to enhance measurement precision. By tuning the diaphragm's resonant frequency to match the incident electromagnetic waves, the sensor achieves high sensitivity to pressure changes while maintaining a relatively simple structure. The resonance effect amplifies the measurement signal without requiring complex additional components.
3Temperature
If sapphire and platinum materials are used for high-temperature compatibility, then sensor operation at extreme temperatures is enabled, but manufacturing complexity increases
Solution Approach 1:
The sensor is divided into functionally distinct segments: a sapphire diaphragm for high-temperature pressure sensing, a silicon MEMS structure for precise measurement, and a platinum coating for electrical contact. Each segment is fabricated using optimized processes for that specific material and then assembled. This segmentation allows each component to be manufactured independently with appropriate techniques, reducing overall manufacturing complexity while enabling operation at extreme temperatures.
Solution Approach 2:
The patent optimizes the thickness and geometric parameters of the sapphire diaphragm to balance high-temperature durability with manufacturability. By carefully controlling the diaphragm thickness (typically 50-200 micrometers) and using standard MEMS fabrication techniques for the silicon structure, the sensor achieves both temperature resistance and ease of manufacture. The platinum layer thickness is also optimized to provide sufficient electrical contact without excessive material usage or processing complexity.
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 enables accurate and reliable pressure measurement in harsh environments, extending sensor operation beyond the limits of conventional sensors, reducing high cycle fatigue risks, and providing insights for improved gas turbine monitoring.
Implementation Method 1
a diaphragm, which deflects either downward or upward in response to a corresponding applied pressure difference across the diaphragm
Implementation Method 2
a conductive ground plane under the diaphragm and a conductive antenna under the ground plane form a capacitive element
Implementation Method 3
An incident electromagnetic wave interacts with the antenna under the ground plane on the MEMS sensor in such a way that a portion of the incident electromagnetic wave is reflected back providing information about the deflection of the diaphragm
Implementation Method 4
The sensor is designed to have a corresponding electrical resonant frequency such that as the diaphragm deflects in response to an applied pressure, the electrical resonant frequency shifts, which results in direct measurement of the applied pressure
Data Source
AI summary
Methods and apparatuses for measuring static and dynamic pressures in harsh environments are disclosed. A pressure sensor according to one embodiment of the present invention may include a diaphragm constructed from materials designed to operate in harsh environments. A waveguide may be operably connected to the diaphragm, and an electromagnetic wave producing and receiving (e.g., sensing) device may be attached to the waveguide, opposite the diaphragm. A handle may be connected between the diaphragm and the waveguide to provide both structural support and electrical functionality for the sensor. A gap may be included between the handle and the diaphragm, allowing the diaphragm to move freely. An antenna and a ground plane may be formed on the diaphragm or the handle. Electromagnetic waves may be reflected off the antenna and detected to directly measure static and dynamic pressures applied to the diaphragm.