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Carbon nanotubes (CNTs) are hollow tube-like structures that can be measured in the nanometer scale.
These nanotubes are made up of carbon and exhibit extraordinary properties such as high elasticity, low density, good thermal and electrical conductivity, and being chemically inert. Researchers continue to make significant discoveries in the field of electronics, optics, medicine, water treatments, etc., with the help of carbon nanoparticles.
On the basis of the number of carbon layers, carbon nanotubes can be categorized as single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs). This article discusses the recent developments of carbon nanotubes with regard to their structural improvements and advancement in their applications.
Structural Advancement
Advancement in the development of the novel structure of carbon nanotube
New electronic devices demand sophisticated technology that could help to design devices that are smaller in size and contain maximum inbuilt features. These kinds of technological advancements can only take place with the structural development.
Researchers continue to explore new materials, modify their structural arrangement, and investigate their function. For example, the arrangement of two-dimensional crystals (one molecule thickness) in layers to produce structures called Van der Waals heterostructures.
Recently, Professor Shigeo Maruyama, Associate Professor Rong Xiang and their team at the University of Tokyo have developed carbon nanotubes by a new method. This method involves the binding of carbon nanotubes at a high-temperature atmosphere that contains boron nitride, to form an even and continuous layer or crystal.
Thereafter, a third layer is added in the form of molybdenum disulfide following the earlier process. This encapsulation of tube structures is known as a coaxial structure where multiple one-dimensional structures are arranged in an axis. Maruyama, Xiang and their team stated that these one-dimensional Van der Waals structures are an entirely new class of material and its properties are completely unexplored.
They are highly hopeful that their discovery could be effectively used in lasers, flexible electronics, electrocatalytic water splitting (to produce hydrogen), solar energy conversion, photoelectric devices, etc.
Find out more about carbon nanotubes
Advancement in Medicine
Carbon nanotubes for nervous tissue regeneration
A great structural and morphological similarity exists between carbon nanotubes and nerve cells. Carbon nanotubes share morphological similarity with neurites and dimensional similarities with dendrites. Some of the properties of carbon nanotubes such as charge, roughness, polarity, and the chemical structure have the ability to alter the affinity of neurons bound to the carbon nanotube-containing surface.
These characteristic features make carbon nanotubes interesting tools for studying neural pathologies and damage to nerve tissues. Carbon nanotubes also provide opportunities for neural repairing, probing, stimulating, reconfiguring neural networks, and also to study the mechanisms of neuronal functions.
There are two different ways by which the functions of a neural cell can be regulated through biofunctionalized carbon nanotubes. The first method involves the direct incorporation of the carbon nanotubes into the nerve tissue. In this method, carbon structures directly interact with nerve culture and therefore expand or disperse within the cells.
In the case of the second method, carbon nanotubes are used as modifiers of other materials which will ultimately improve various neuro functions. This approach is also able to enhance the activity of therapeutic drugs and proteins (neurotrophic factors) and nucleic acids (siRNA, etc.).
Among all the different types of neural injuries, peripheral nerve (transected sciatic nerve) damages are the most common occurrence. The regeneration of this nerve mainly depends on the severity of the injury. In a recent advancement, scientists have developed a carbon nanotube-interfaced phosphate glass microfiber scaffold for the regeneration of the transected sciatic nerve.
Learn about the production of carbon nanotubes from toxic industrial gases
Advancement in Electronics
The transition of carbon nanotube transistors from the laboratory to the commercial market
Until very recently, carbon nanotube field-effect transistors (CNFETs) existed in “artisanal” space, which was produced in very small quantities in academic laboratories. In a recent publication of Nature Electronics, scientists revealed how CNFETs can be manufactured in a larger quantity (200-millimeter wafers) and they described it as an energy-efficient option when compared to silicon field-effect transistors.
Max Shulaker, Assistant Professor of Electrical Engineering and Computer Science, at MIT and his team, analyzed and improved the deposition technique (deposition of carbon nanotube) used to make the CNFETs. This new technique could not only increase the numbers in production but also decrease the cost of production.
This method of deposition of nanotubes is known as incubation, where a wafer is completely soaked in a bath of nanotubes until the nanotubes bind to the surface of the wafer. Perfect alignment of nanotubes in a CNFET is the key to the best performance. However, it is very difficult to arrange billions of tiny nanotubes of one-nanometer diameter, in perfect alignment across a 200-millimeter wafer.
Even though the incubation method is practical for the industry, this technique fails to align nanotubes well, which was primarily thought of as an essential requirement for CNFET’s performance. However, researchers later confirmed that the production of CNFET using a simple incubation process could result in the creation of a transistor with superior performance when compared to a silicon-based transistor.
Scientists continued to improve the incubation process by means of a dry cycling method (intermittently drying out the submerged wafer) which could significantly reduce the incubation time.
Another method which is known as ACE (artificial concentration through evaporation) involves the deposition of a nanotube solution in lesser quantity on a wafer instead of submerging the wafer in a tank.
This process undergoes slow evaporation of the nanotube solution which results in an increase in concentration and density of nanotube deposition on wafer. This method is much more practical for industrial production as it is a rapid, automated, and low-cost process.
References and Further Reading
University of Tokyo (2020) Rolled up carbon nanotubes: New research builds upon carbon nanotubes to create a novel functional structure. ScienceDaily. http://dx.doi.org/10.1126/science.aaz2570
Ham, B (2020) Carbon nanotube transistors make the leap from lab to factory floor. [Online] MIT News. Available at: http://news.mit.edu/2020/carbon-nanotube-transistors-factory-0601 (Accessed on 3 June 2020).
Di Maio, E. and Redondo-Gomez, C. et al (2020) Recent Advances in Carbon Nanotubes for Nervous Tissue Regeneration. Advances in Polymer Technology. 686. https://doi.org/10.1155/2020/6861205
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