Dielectric Membrane Flow Sensor for Low-Power Thermal Isolation
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Solution Overview
Problem
Existing thermal fluid flow sensors suffer from high power dissipation, low sensitivity, slow dynamic response, mechanical fragility, complex fabrication processes, and non-CMOS compatibility, which affect their performance and reliability.
Innovation Solution
A micro-machined sensor with a dielectric membrane featuring recessed regions or holes that thermally isolate the heating element, allowing heat dissipation through fluid conduction and convection, and incorporating sensing elements to measure fluid flow and thermal conductivity properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a continuous dielectric membrane is used to support the heating element, then mechanical robustness is improved, but thermal isolation is reduced leading to higher power dissipation
Solution Approach 1:
The continuous dielectric membrane is segmented by introducing holes or recessed regions, creating a discontinuous structure. This segmentation reduces the thermal conduction paths through the membrane while maintaining mechanical support at the boundaries, thereby improving thermal isolation and reducing power dissipation without completely compromising mechanical robustness.
Solution Approach 2:
The dielectric membrane is designed with holes or porous regions that allow fluid passage while providing thermal isolation. The porous/discontinuous structure reduces thermal conduction from the heating element to the substrate, lowering power dissipation while the remaining membrane material maintains sufficient mechanical strength.
2Measurement precision
If the heating element is thermally isolated from the substrate, then sensitivity is improved, but power dissipation increases
Solution Approach 1:
Instead of complete thermal isolation which would cause excessive power dissipation, the patent applies partial thermal isolation through a discontinuous dielectric membrane. The holes or recessed regions provide sufficient thermal isolation to improve sensitivity for flow detection, while the remaining membrane material limits excessive heat loss, achieving an optimal balance between sensitivity and power consumption.
3Manufacturing precision
If a complex fabrication process is used to create precise sensor structures, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The discontinuous dielectric membrane structure serves multiple functions: it provides mechanical support, enables thermal isolation, allows fluid passage, and defines the sensing region. This multi-functionality is achieved through a single fabrication step patterned on the substrate, eliminating the need for separate structures or steps for each function and simplifying the overall fabrication process while maintaining manufacturing 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
The sensor achieves reduced power consumption, increased sensitivity, faster response, improved mechanical robustness, and compatibility with CMOS manufacturing processes, enabling accurate measurement of fluid flow properties and composition.
Implementation Method 1
a heating element located within the dielectric membrane
Implementation Method 2
allowing heat dissipation through fluid conduction and convection
Implementation Method 3
allowing heat dissipation through fluid conduction and convection
Implementation Method 4
recessed regions or holes that thermally isolate the heating element
Data Source
AI summary
We disclose herein a flow and thermal conductivity sensor comprising a semiconductor substrate comprising an etched portion, a dielectric region located on the semiconductor substrate, wherein the dielectric region comprises at least one dielectric membrane located over the etched portion of the semiconductor substrate and a heating element located within the dielectric membrane. The dielectric membrane comprises one or more discontinuities located between the heating element and an edge of the dielectric membrane.