Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. Their radius is generally in the range of a few nanometers. It is a hollow structure with the walls formed by one-atom-thick sheets of carbon, called grapheme, and thus belong to the fullerene structural family forming from a single structural component. The difference in the types of CNTs id formed on the basis of the specific angle at which the graphene sheet is rolled. Hence there are three types of nanotubes based on the rolling angle:-
On the basis of number of CNTs encased:-
1. Single-walled nanotubes(SWNTs)
2. Multi-walled nanotubes (MWNTs)
Individual nanotubes naturally align themselves into "ropes" held together by van der Waals forces called pi-stacking.
They are very stiff with tensile stregnths in 13-60 Gpa range though, they cannot bear compressive stress ...view middle of the document...
Nanotubes and other Fullerenes can be filled with molecules that have either an electronic or structural property which can be used in the field of quantum computation.
Also there are many other new applications surfacing such as paper batteries, artificial muscles, thermo-cells, DNA sequencing or filtration of ions.
CNTs are stable over a large range of temperatures from -30 to 500 degrees celcius in comparison to normal adhesives which are stable over a much shorter range.
Their property of pi-stacking eliminates the chance of disfigurement or non alignment.
CNTs can be arranged much more densly than any other polymer and hence offers a much larger surface area in comparision.
1. Hierarchial structure of gecko toe pads
The minute structures have been thouroughly resolved via SEM (Scanning Electron Microscopy). The basic adhesive unit is the seta which is made of a beta-keratin like compound. It is curved at the the proximities, has an average length of 100 um and a diameter of 5 um for tokay geckos. Each seta further branches out into hundreds of spatula which function as the ultimate contacting elements. These terminals are also tapered, being 200 nm wide and 5-10 nm thick. Setal arrays are distribute on the outer portion of the overlapping stripes known as lamellae that are narrowly spaced with around 0.3-0.6 mm between consecutive lamellae
A single seta generates maximum adhesive forces of around 200 μN in tangential and 20 μN in normal directions against a smooth clean glass substrate. Normal pull-off force for a single spatulae is 10 nN( found by utilizing atomic force microscopy (AFM)). Now, with half a million spatula on one foot, a single foot of geckos could generate a force of 100 N, around 10 times that required for their average body weight. However these measurements have been done in near perfect conditions on a glass or silican substrate, the effectiveness of the adhesive in reality may even drop to 30 percent according to the conditions.