Carbon Nanotube Infrared Sensor with High-TCR Semiconducting Layer
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Solution Overview
Problem
Existing infrared sensors using carbon nanotubes face challenges with low TCR values due to the presence of metallic nanotubes and the difficulty in removing ionic surfactants used for separation, limiting performance improvement.
Innovation Solution
The infrared sensor employs a carbon nanotube layer composed of at least 66% semiconducting carbon nanotubes with specific diameters and lengths, separated using a nonionic surfactant, and a manufacturing method involving dispersion, electrophoresis, and heat treatment to form a stable, dispersed network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If single-walled carbon nanotubes are applied to a bolometer unit using a low-cost thin film process, then manufacturing cost is reduced, but TCR value remains low due to the presence of metallic carbon nanotubes in the mixed state
Solution Approach 1:
The patent extracts and removes metallic carbon nanotubes from the mixed-state nanotube suspension through electrophoresis separation, isolating only the semiconducting carbon nanotubes for bolometer unit application. This extraction process resolves the contradiction by eliminating the harmful metallic components that limit TCR while maintaining the low-cost thin film manufacturing approach.
Solution Approach 2:
The patent changes the electrical charge parameter of carbon nanotubes through acid treatment, causing metallic and semiconducting nanotubes to exhibit different electrophoretic mobility. This parameter change enables effective separation through electrophoresis, allowing the bolometer unit to achieve high TCR values by selectively incorporating only semiconducting nanotubes while maintaining cost-effective manufacturing.
2Manufacturing precision
If ionic surfactant is used to separate semiconducting carbon nanotubes, then TCR value is improved, but the surfactant cannot be easily removed from the nanotube structure
Solution Approach 1:
The patent employs a disposable acid treatment approach that temporarily modifies the surface charge of carbon nanotubes for separation purposes, then removes the acid treatment effect through washing. This disposable approach avoids the need for persistent ionic surfactant coating, enabling easy removal of separating agents while achieving high TCR values through electrophoresis-based separation.
Solution Approach 2:
The patent substitutes the chemical surfactant-based separation mechanism with an electrical field-based electrophoresis mechanism. By replacing the ionic surfactant system with an electric field system, the patent achieves effective separation of semiconducting and metallic nanotubes without introducing difficult-to-remove surfactant residues, thus improving both TCR and ease of manufacture.
3Ease of manufacture
If metallic and semiconducting components are present in a mixed state, then the manufacturing process is simplified, but TCR value is limited due to the presence of metallic nanotubes
Solution Approach 1:
The patent segments the mixed-state carbon nanotube population into distinct metallic and semiconducting fractions through electrophoresis separation. This segmentation process divides the previously homogeneous mixed suspension into purified semiconducting nanotube fractions suitable for bolometer application, resolving the contradiction by maintaining process simplicity while achieving the necessary material purity for high TCR performance.
Solution Approach 2:
The patent introduces an acid treatment intermediary that temporarily modifies the surface properties of carbon nanotubes to enable electrophoresis separation. This intermediary acid treatment creates charge differences between metallic and semiconducting nanotubes, facilitating their separation while maintaining overall process simplicity. The acid treatment is subsequently removed, leaving purified semiconducting nanotubes for bolometer fabrication.
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 method achieves a high TCR value, enabling improved sensor performance with reduced costs and increased mass productivity through a simplified process that avoids the need for ultracentrifugation and easy surfactant removal.
Implementation Method 1
an infrared sensor comprising: a substrate; a first electrode on the substrate; a second electrode spaced from the first electrode on the substrate; and a carbon nanotube layer electrically connected with the first electrode and the second electrode
Implementation Method 2
subjecting the carbon nanotube dispersion liquid to free flow electrophoresis to separate semiconducting carbon nanotubes and metallic carbon nanotubes
Implementation Method 3
subjecting the substrate on which the semiconducting carbon nanotube dispersion liquid is applied to heat treatment
Data Source
AI summary
An object of the present invention is to provide an infrared sensor having a high TCR value, and a method for manufacturing the infrared sensor. The infrared sensor comprises a substrate, a first electrode on the substrate, a second electrode spaced from the first electrode on the substrate, and a carbon nanotube layer electrically connected with the first electrode and the second electrode, wherein the carbon nanotube layer comprises semiconducting carbon nanotubes in an amount more than 66% by mass based on the total amount of carbon nanotubes and 60% or more of the carbon nanotubes contained in the carbon nanotube layer have a diameter within a range of 0.6 to 1.5 nm and a length within a range of 100 nm to 5 μm.