Phononic Crystal Beam Thermal Insulation for Infrared Sensors
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Solution Overview
Problem
Conventional infrared sensors with a phononic crystal beam exhibit reduced thermal insulation performance due to temperature-dependent changes in the phonon dispersion relation, leading to inadequate thermal insulation across the beam, as the phononic crystal's design is optimized for either the infrared receiver or the base substrate temperature, but not both.
Innovation Solution
A thin-film phononic crystal beam with periodically arranged through holes of varying periods is used, increasing the period at arbitrary intervals from the infrared receiver to the base substrate, creating multiple phononic domains with different periodic structures to enhance thermal insulation by mismatching phonon group velocities and forming multiple phononic band gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phononic crystal with a single period is used in the beam, then thermal insulation performance is improved at a specified temperature, but thermal insulation performance deteriorates when temperature changes cause the phononic band gap to deviate from the heat band
Solution Approach 1:
The beam is divided into multiple phononic crystal regions, each with different periodic structures (different periods P1, P2, P3). Each region creates phononic band gaps at different frequency ranges, allowing the beam to maintain thermal insulation performance across a wide temperature range as the heat band shifts with temperature changes.
Solution Approach 2:
Different sections of the beam are assigned different phononic crystal periods to create locally optimized thermal insulation properties. The first region has period P1 optimized for lower temperatures, the second region has period P2 for intermediate temperatures, and the third region has period P3 for higher temperatures, ensuring effective thermal insulation throughout the entire temperature range.
2Reliability
If porosity is increased in a simple porous structure, then thermal conductance is reduced, but thermal insulation performance is limited compared to phononic crystal structures
Solution Approach 1:
Instead of simply increasing porosity, the invention changes the fundamental parameter from random pore distribution to ordered periodic structures with specific periods. This creates phononic band gaps that actively block phonon propagation at specific frequency ranges, achieving superior thermal insulation performance compared to simple porous structures with the same porosity level.
3Reliability
If a phononic crystal is designed for the infrared receiver temperature, then thermal insulation is improved at the receiver side, but thermal insulation performance is reduced at the base substrate side due to temperature gradient
Solution Approach 1:
The beam is segmented into multiple phononic crystal regions with different periods arranged in sequence from the infrared receiver to the base substrate. This segmentation allows each region to be optimized for different temperature conditions, creating uniform thermal insulation performance throughout the entire beam despite the temperature gradient.
Solution Approach 2:
The phononic crystal structure is made asymmetric by using different periods in different regions rather than a uniform period throughout. This asymmetric design with periods P1, P2, P3 in different regions allows the structure to adapt to the asymmetric temperature distribution along the beam, improving overall thermal insulation uniformity.
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 configuration provides consistent and improved thermal insulation throughout the beam, enhancing the sensitivity of the infrared sensor by reducing thermal conductivity and maintaining effective insulation across varying temperatures.
Implementation Method 1
introduction of a periodic structure allows artificial control of original phonon dispersion of the material, allowing control of thermal conductivity itself of the material
Implementation Method 2
When the PBG can be formed in the heat band, phonons inside the PBG cannot exist and will not contribute to thermal conduction. As a result, thermal conductivity can be reduced
Implementation Method 3
increasing the period at arbitrary intervals in a direction from the infrared receiver toward the base substrate, allowing control of thermal conductivity itself of the material
Implementation Method 4
creating multiple phononic domains with different periodic structures to enhance thermal insulation by mismatching phonon group velocities and forming multiple phononic band gaps
Data Source
AI summary
An infrared sensor is formed in such a manner that an infrared receiver and a base substrate are spaced with a beam made of a thin-film phononic crystal in which through holes are arranged periodically. The beam made of a phononic crystal is formed in such a manner that a period P of through holes increases at arbitrary intervals in a direction from the infrared receiver toward the base substrate.