Buckypaper is a thin sheet made from an aggregate of carbon nanotubes. The nanotubes are approximately 50,000 times thinner than a human hair. Originally, it was fabricated as a way to handle carbon nanotubes, but in 2008 is being studied and developed into applications by several research groups, showing promise as a building material for aerospace vehicles, body armor and next-generation electronics and displays.

Background

Buckypaper is a macroscopic aggregate of carbon nanotubes (CNT), or "buckytubes". The idea for buckypaper came when British scientist Harry Kroto and Rice University scientists were attempting to create the conditions found in a star when it forms elemental carbon. It owes its name to buckminsterfullerene, the 60 carbon fullerene (an allotrope of carbon with similar bonding that is sometimes referred to as a "Buckyball" in honor of R. Buckminster Fuller). Richard Smalley, Sir Harold Kroto, and Robert Curl shared the 1996 Nobel Prize in Chemistry for their discovery of buckminsterfullerene. Their discoveries and subsequent work with carbon nanotubes led to a revolution in the fields of chemistry and materials science.

Synthesis

The generally accepted method for forming such CNT films involves the use of non-ionic surfactants, such as Triton X-100 and Sodium lauryl sulfate, which improves their dispersibility in aqueous solution. These suspensions can then be membrane filtered under positive or negative pressure to yield uniform films. The Van der Waals force's interaction between the nanotube surface and the surfactant can often be mechanically strong and quite stable and therefore there are no assurances that all the surfactant is removed from the CNT film after formation. Washing with methanol, an effective solvent in the removal of Triton X, was found to cause cracking and deformation of the film. It has also been found that Triton X can lead to cell lysis and in turn tissue inflammatory responses even at low concentrations.

In order to avoid adverse side-effects from the possible presence of surfactants, an alternative casting process was developed involving a Frit Compression method that did not require the use of surfactants or surface modification. The dimensions can be controlled through the size of the syringe housing and the through the mass of carbon nanotubes added. Their thicknesses are typically much larger than surfactant-cast buckypaper and have been synthesised from 120 μm up to 650 μm; whilst no nomenclature system exists to govern thicknesses for samples to be classified as paper, samples with thicknesses greater than 500 μm are referred to as buckydiscs. Beyond 5mm thickness, the sample is termed a buckycolumn. The frit compression method allows rapid casting of buckypaper, buckydiscs and buckycolumns with recovery of the casting solvent and control over the 2D and 3D geometry.