Carbon Nanotube Field Emitter Rolling Method
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Solution Overview
Problem
Existing methods for making carbon nanotube field emitters, such as in-situ synthesis and printing, result in entangled nanotubes with unsatisfactory field emission characteristics and low mechanical properties, and the printing method is inefficient with a low carbon nanotube density and high risk of damage during processing.
Innovation Solution
A method involving a flexible carbon nanotube layer with aligned nanotubes, coated with a metal layer, and rolled to form a single structure with distinct emission and supporting portions, enhancing mechanical properties and field emission performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If in-situ synthesis method is used to grow carbon nanotubes directly on cathode electrode, then carbon nanotubes can be formed on the electrode surface, but the nanotubes become entangled and field emission characteristics deteriorate
Solution Approach 1:
The invention separates the carbon nanotube formation process from the electrode structure by using a flexible substrate as an intermediate carrier. Carbon nanotubes are grown on the flexible substrate separately, then the entire substrate is rolled into a cylindrical shape to form the final emitter structure. This segmentation prevents nanotube entanglement while maintaining coverage.
Solution Approach 2:
The invention transitions from a planar substrate to a three-dimensional cylindrical structure by rolling the flexible substrate. This dimensional change allows the carbon nanotubes to maintain their aligned growth direction while forming a curved surface emitter, improving field emission characteristics without causing entanglement.
2Quantity of substance
If in-situ synthesis method is used to grow carbon nanotubes on cathode electrode, then carbon nanotubes can be formed on the electrode, but mechanical properties of the emitter decrease
Solution Approach 1:
By separating the nanotube growth substrate from the final electrode structure, the invention allows the flexible substrate to provide mechanical support during manufacturing. The rolled cylindrical structure maintains mechanical integrity while accommodating high carbon nanotube density.
Solution Approach 2:
The invention creates a composite structure combining the flexible substrate material with the carbon nanotube layer. This composite approach leverages the mechanical properties of the substrate while maintaining the electrical and emission properties of the carbon nanotubes.
3Ease of manufacture
If printing method is used to deposit carbon nanotube paste on conductive cathode, then pattern can be formed on electrode, but effective emitter density remains low
Solution Approach 1:
Instead of printing nanotubes onto a rigid electrode and hoping for vertical extrusion, the invention inverts the approach by growing nanotubes vertically on a flexible substrate first, then rolling the substrate to create the cylindrical emitter. This ensures high emitter density from the start.
Solution Approach 2:
The invention uses the rolling process to transform a two-dimensional nanotube array on a flat substrate into a three-dimensional cylindrical emitter structure. This dimensional transformation maximizes the effective emitter density while maintaining the pattern formation capability.
4Ease of manufacture
If printing method is used with peeling step to form extrusions, then carbon nanotube emitters can be formed, but nanotubes are damaged and performance decreases
Solution Approach 1:
The invention performs the nanotube alignment and growth action in advance on the flexible substrate before the final emitter assembly. The nanotubes are already in their optimal vertical orientation when the substrate is rolled, eliminating the need for subsequent peeling or extrusion steps that could cause damage.
Solution Approach 2:
The invention extracts the damaging peeling step from the manufacturing process by using a flexible substrate that can be directly rolled. This removes the harmful mechanical action while preserving the emitter formation capability.
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 produces carbon nanotube field emitters with stable field emission performance and improved mechanical properties, addressing the issues of entanglement and low efficiency in existing methods.
Implementation Method 1
The carbon nanotube can transmit extremely high current density and emit electrons easily at low voltages. Thus it can be used as a field emitter
Data Source
AI summary
A carbon nanotube field emitter is disclosed. The carbon nanotube field emitter includes an emission portion and a supporting portion. The emission portion and the supporting portion are configured as one piece to form a roll structure. The emission portion includes a first rolled carbon nanotube layer, which includes a number of carbon nanotubes. The supporting portion includes a rolled composite layer, which includes at least one second rolled carbon nanotube layer and a rolled metal layer stacked with each other. Another carbon nanotube field emitter with a number of separated emission tips on the emission portion is also disclosed.