Conical carbon filaments with axial cylindrical channels and open tips (see Figure) supported on vapor-grown carbon microfibers; can be prepared by iron-catalyzed pyrolysis of methane. The filament tips are single-walled and the cylindrical channels are open at the tip, opening the possibility of transporting fluids in nanochannels. The dimension of the. base was on the micrometer scale, allowing handling or assembly of the filaments.