Omnidirectional Reflector Using Non-Periodic Multilayer Stack
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Solution Overview
Problem
Existing omnidirectional structural color technologies face challenges in achieving angle-independent reflection using materials with low indices of refraction, which are also cost-effective, and often result in reduced omnidirectional properties when fabricated.
Innovation Solution
A non-periodic multilayer stack with alternating layers of high and low refractive index materials, where each layer has a predefined thickness, is used to create an omnidirectional reflector that reflects more than 50% of a narrow band of electromagnetic radiation, particularly designed to maintain reflectance across a broad range of angles without the need for high refractive index materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If materials with high indices of refraction are used to achieve omnidirectional structural color, then the angle-independent reflection performance is improved, but the manufacturing cost increases
Solution Approach 1:
The patent changes the structural parameters of the multilayer stack, specifically using a non-periodic thickness distribution where layer thicknesses vary according to a gradient pattern rather than repeating uniformly. This structural parameter change enables omnidirectional reflection performance comparable to high-index materials while using cost-effective low-index materials like SiO2 and TiO2
Solution Approach 2:
The patent employs composite multilayer structures combining different dielectric materials (such as SiO2 and TiO2) with complementary refractive index properties. This composite approach allows the system to achieve effective high-index behavior through material combination rather than relying on expensive single high-index materials
2Ease of manufacture
If materials with low indices of refraction are used to reduce manufacturing cost, then the ease of manufacture is improved, but the omnidirectional reflection performance deteriorates
Solution Approach 1:
The patent divides the multilayer stack into numerous thin layers (typically 10-20 layers) with gradually varying thicknesses. This segmentation allows each individual low-index layer to contribute incrementally to the overall omnidirectional reflection effect, accumulating to achieve performance that would otherwise require high-index materials
Solution Approach 2:
The patent implements a gradient thickness profile where layer thicknesses are systematically varied according to a mathematical gradient pattern rather than being uniform or periodic. This parameter change optimizes the optical path differences across layers, enabling broadband omnidirectional reflection using low-index materials
3Ease of manufacture
If periodic layered structures are used, then the ease of manufacture is improved, but the omnidirectional reflection bandwidth is limited
Solution Approach 1:
The patent introduces asymmetry by using a non-periodic, gradient-based thickness distribution pattern instead of repeating periodic structures. This asymmetric design breaks the limitations of periodicity, allowing the structure to reflect multiple wavelengths and maintain omnidirectional performance across a broader spectral range
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 achieves angle-independent reflection of a narrow band of electromagnetic radiation across a wide range of angles, including up to 45 degrees, using low refractive index materials, thereby addressing the cost and performance limitations of previous technologies.
Implementation Method 1
a non-periodic multilayer stack with alternating layers of high and low refractive index materials, where each layer has a predefined thickness, is used to create an omnidirectional reflector that reflects more than 50% of a narrow band of electromagnetic radiation
Implementation Method 2
The at least A1 and B1 can be alternately stacked on top of each other with each layer having a predefined thickness dA1 and dB1, respectively. The thickness dA1 is not generally equal to the thickness dB1 such that the multilayer stack has the non-periodic layered structure.
Data Source
AI summary
An omnidirectional structural color (OSC) having a non-periodic layered structure. The OSC can include a multilayer stack that has an outer surface and at least two layers. The at least two layers can include at least one first index of refraction material layer A1 and at least one second index of refraction material layer B1. The at least A1 and B1 can be alternately stacked on top of each other with each layer having a predefined thickness dA1 and dB1, respectively. The dA1 is not generally equal to the dB1 such that the multilayer stack has a non-periodic layered structure.