Charging Nanotubes to Produce Fibers and Films
For a long time people were trying to understand how a gecko is able to crawl up surfaces too smooth to attach to with other, better known methods. Eventually it was discovered that gecko toes have extremely small hairs that take advantage of van der Waals forces to adhere to any surface. What helps the gecko though does not help carbon nanotubes, but Rice University researchers have found a solution to that.
Van der Waals forces exist between molecules that are sufficiently near each other for their electrostatic fields to interact, often causing them to attract. For a gecko, this attraction allows them to crawl up walls, but for carbon nanotubes, it causes them to clump together into an unusable mess. Previous research had successfully infused nanotubes with potassium atoms and then removed some with a solvent, to give the nanotubes a negative charge that counters the van der Waals forces. By adding cage-like crown ethers to the mix, the Rice researchers were able to remove additional potassium ions, thereby leaving behind more electrons to negatively charge the nanotubes.
This greater negative charge is enough to prevent the nanotubes from clumping together due to van der Waals forces, allowing more to be in a solution together. With more nanotubes in a solution, super strong and conductive fibers of nanotubes can be more easily created. Also, the negative charge applied to the nanotubes is more easily worked with than the positive charge a superacid would impart.
Source: Rice University