Lattice Structures with Designed Thermal Expansion Coefficients
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Solution Overview
Problem
Current design methods for microstructural architectures with superior thermal properties rely on topology optimization, which often results in local minima solutions and impractical features due to the lack of creative recognition and application of practical constraints, making it difficult to achieve optimal thermal expansion coefficients.
Innovation Solution
The development of lattice-based structures with unit cells featuring bi-material constructions, including flexure bearings and thermally actuated tabs, allowing for the accommodation of thermal expansion in void spaces to achieve desired bulk thermal expansion coefficients, either positive, negative, or zero, by using the Freedom and Constraint Topologies (FACT) methodology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If topology optimization is used to generate microstructural architectures, then the design can approach desired target thermal properties, but the solution often gets trapped in local minima and produces impractical features due to lack of creative recognition of practical constraints
Solution Approach 1:
The patent applies parameter changes by systematically varying geometric parameters (unit cell dimensions, strut thicknesses, cavity sizes) and material properties (thermal expansion coefficients, elastic moduli) to achieve desired bulk thermal expansion coefficients. This analytical parameter optimization avoids local minima traps by providing direct design equations rather than iterative numerical optimization.
Solution Approach 2:
The patent implements local quality by creating unit cells with non-uniform material distribution and varying local geometries. Different regions of the unit cell have different material properties and structural characteristics, allowing localized thermal expansion management while achieving global thermal stability. The bi-material construction with different expansion coefficients in different regions exemplifies this principle.
2Manufacturing precision
If bi-material unit cell constructions with flexure bearings are used, then thermal expansion can be accommodated in void spaces to achieve desired bulk thermal expansion coefficients, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the lattice structure into repeating unit cells, each containing segmented functional elements (base, actuators, flexure bearings, tabs, void spaces). This modular segmentation allows independent optimization of each component while achieving complex bulk thermal properties through systematic arrangement of simple repeating units.
Solution Approach 2:
The patent implements nesting by placing actuators and tabs within void spaces of the unit cell, and by nesting flexure bearings within the bi-material construction. The actuator is positioned within the base cavity, and the tab connects internal actuator motion to external structural movement, creating a nested arrangement that manages thermal expansion efficiently within compact geometry.
3Manufacturing precision
If void spaces are formed between adjacent unit cells to accommodate thermal expansion, then the lattice structure can maintain desired bulk thermal expansion coefficient, but the volume of the structure increases
Solution Approach 1:
The patent applies porous materials principles by incorporating void spaces within unit cells and between adjacent unit cells. These controlled porosity regions accommodate thermal expansion movements without requiring significant additional volume. The void spaces act as thermal expansion buffers, allowing the lattice to maintain dimensional stability while minimizing volume increase through efficient space utilization.
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 approach enables the creation of materials with tunable thermal expansion coefficients, suitable for applications requiring precision and stability, such as optical alignment, electrical packaging, and thermal actuators, by effectively managing thermal growth or shrinkage through designed void spaces and structural modifications.
Implementation Method 1
an actuator, of a second material type and associated second thermal expansion coefficient greater than the first thermal expansion coefficient, operably connected to the tab and the base so that thermal expansion of the actuator inwardly displaces the tab into the base cavity
Implementation Method 2
a flexible bridge connected to the base across the cavity opening; a tab connected to the flexible bridge so as to be guided thereby in a direction into or out of the base cavity
Data Source
AI summary
A thermal expansion-managed lattice structure having a plurality of unit cells each having flexure bearing-mounted tabs supported on a base and actuated by thermal expansion of an actuator having a thermal expansion coefficient greater than the base and arranged so that the tab is inwardly displaced into a base cavity. The flexure bearing-mounted tabs are connected to other flexure-bearing-mounted tabs of adjacent unit cells so that the adjacent unit cells are spaced from each other to accommodate thermal expansion of individual unit cells while maintaining a desired bulk thermal expansion coefficient of the lattice structure as a whole.