Frit compression

Frit compression is the technique used to fabricate buckypaper and buckydiscs from a suspension of carbon nanotubes in a solvent. This is a quick, efficient method over surfactant-casting or acid oxidation filtration of carbon nanotubes.Buckypaper from frit compression of multi-walled carbon nanotubesA water-cast buckydisc with convex lower surfaceBuckycolumn just after castingBuckycolumn with hyperboloid geometry on dryingBuckyprism with casting frit Frit compression is the technique used to fabricate buckypaper and buckydiscs from a suspension of carbon nanotubes in a solvent. This is a quick, efficient method over surfactant-casting or acid oxidation filtration of carbon nanotubes. Traditional methods of buckypaper production involves the use of surfactants to disperse carbon nanotubes into aqueous solutions. It was found that filtering this suspension allowed the nanotubes to pack together in a paper-like mat, thus coining the term “buckypaper” (bucky being the reference to the buckminsterfullerene molecule). The problem was the difficulty in removing the surfactant afterwards, where the surfactant has been linked with cell lysis and tissue inflammation. Acid oxidation of carbon nanotubes can also be used in filtration to form buckypaper, but requires a high degree of surface acidic groups in order to obtain efficient dispersal in aqueous solution. An alternative casting method was developed in 2008 to produce buckypaper that did not require the use of surfactants or the acid oxidation of carbon nanotubes in order to obtain high-purity buckypaper for biomedical applications. The frit-compression system was adapted from a Solid phase extraction (SPE) column, where a suspension of carbon nanotubes is squeezed between two polypropylene frits (70 micrometre pore diameter) inside a syringe column. The pore structure of the frit allows a rapid exit of the solvent leaving the carbon nanotubes to be pressed together. The presence of the solvent controls the interaction between the tubes allowing the formation of tube-tube junctions; its surface tension directly affects the overlap of adjoining nanotubes thus gaining control over the porosity and pore diameter distribution of buckypaper. The distribution of carbon nanotubes in solvent does not have to be a stable suspension, rather a general dispersion serves much easier to keep the nanotubes between the frits rather than pass through them.