Sorting Metallic SWNTs via Magnetic Gradient

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Solution Overview

Problem

Existing methods for producing single wall carbon nanotubes (SWNTs) result in mixtures of metallic and semiconducting SWNTs with varying diameters and lengths, making it difficult to achieve uniform conductivity, which is necessary for improved application performance.

Innovation Solution

The process involves disposing SWNTs in a dilute fluid and exposing them to a dipole-inducing magnetic field that induces magnetic dipoles, orienting metallic SWNTs, and then using a spatial gradient magnetic field to separate them from semiconducting SWNTs, allowing for the effective sorting of metallic and semiconducting types based on conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If existing methods are used to produce SWNTs, then SWNTs can be manufactured, but the product is a mixture of metallic and semiconducting SWNTs with varying diameters and lengths, resulting in non-uniform conductivity

Engineering Contradiction:

Improveconductivity uniformityVSAvoidsorting process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies parameter changes by utilizing the differential magnetic susceptibility between metallic and semiconducting SWNTs. Metallic SWNTs have higher magnetic susceptibility and become strongly oriented in magnetic fields, while semiconducting SWNTs remain randomly oriented. This parameter difference enables selective separation through magnetic field application, achieving conductivity uniformity without complex sorting machinery.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces mechanical separation methods with magnetic field-based separation. Instead of using mechanical filters, centrifuges, or other physical separation devices that would be complex and potentially damaging to the nanotubes, the invention uses magnetic field orientation to selectively align metallic SWNTs, allowing for simple and gentle separation based on their magnetic properties.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If magnetic field is applied to orient metallic SWNTs, then metallic SWNTs can be separated from semiconducting SWNTs, but the process requires precise control of magnetic field strength and duration

Engineering Contradiction:

Improveseparation purityVSAvoidprocess control difficulty

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The patent employs dynamic magnetic field application, transitioning from static to time-varying magnetic fields. The magnetic field strength is varied over time to first orient metallic SWNTs and then maintain that orientation during separation. This dynamic approach allows for effective separation while simplifying control, as the field can be turned on and off rather than requiring continuous precise adjustment.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies preliminary action by first applying a magnetic field to orient metallic SWNTs before actually performing the separation. This pre-orientation step ensures that when separation occurs, the metallic SWNTs are already aligned and ready for efficient separation, reducing the need for complex real-time control during the separation process itself.

Inventive Principle:

Principle #10Preliminary action

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 method enables the separation of metallic and semiconducting SWNTs, ensuring uniform conductivity, which enhances the performance and application of SWNTs in various technologies by providing pure metallic or semiconducting SWNTs.

Implementation Method 1

exposing the SWNTs to a dipole-inducing magnetic field which induces magnetic dipoles in the SWNTs so that a strength of a dipole depends on a conductivity of the SWNT containing the dipole, orienting the metallic SWNTs

Methodology Applied

Scientific EffectMagnetic dipole induction: Magnetic Field

Implementation Method 2

exposing the SWNTs to a magnetic field with a spatial gradient so that the oriented metallic SWNTs drift in the magnetic field gradient thereby becoming spatially separated from the semiconducting SWNTs

Methodology Applied

Scientific EffectMagnetic field gradient force: Lorentz Force

Data Source

PatentUS9517938B2Applying spatial gradient magnetic field to metallic/semiconducting SWNTs in fluid

Publication Date: 2016.12.13 TEXAS INSTRUMENTS INC

AI summary

A process of sorting metallic single wall carbon nanotubes (SWNTs) from semiconducting types by disposing the SWNTs in a dilute fluid, exposing the SWNTs to a dipole-inducing magnetic field which induces magnetic dipoles in the SWNTs so that a strength of a dipole depends on a conductivity of the SWNT containing the dipole, orienting the metallic SWNTs, and exposing the SWNTs to a magnetic field with a spatial gradient so that the oriented metallic SWNTs drift in the magnetic field gradient and thereby becomes spatially separated from the semiconducting SWNTs. An apparatus for the process of sorting SWNTs is disclosed.