Magnetophoretic continuous purification of single-walled carbon nanotubes from catalytic impurities in a microfluidic device.

A magnetophoretic continuous purification method is presented of single-walled carbon nanotubes (SWCNTs) from the superparamagnetic iron-catalyst impurities in a microfluidic device without any influence on inherent SWCNT properties. By employing microfluidics and a magnetic-field-induced saw-tooth nickel microstructure, a highly enhanced magnetic force in adjoining microchannels is exploited. The iron impurities of SWCNTs are attracted towards areas of higher magnetic-flux density in the microchannels where magnetic field was asymmetrically generated perpendicularly to the streamline. We obtained highly purified SWCNTs at a rate of 0.36 mg h(-1) and that are estimated to be about 99% purity.