US Patent 8110125 - Separation of carbon nanotubes by density gradients

http://www.freepatentsonline.com/8110125.html

This patent from Northwestern University has priority going back to 2005 and includes some basic claims to sorting single walled carbon nanotubes between metallic and semiconducting types. Claim 1 reads:

1. A system for separation of single-walled carbon nanotubes, said system comprising:

a fluid medium comprising a density gradient; and

a nanotube composition comprising single-walled carbon nanotubes of mixed nanotube diameters, chiralities, electronic types, or combinations thereof and at least one surface active component.