Flow-induced voltage generation in high-purity metallic and semiconducting carbon nanotubes

We investigated the flow-induced voltage generation of single-walled carbon nanotubes (SWCNTs), comparing metallic and semiconducting types, flow velocity, and different ionic concentration solutions. The induced fluid-flow voltage was measured using a microfluidics chip that we fabricated with a SWCNT film embedded between its metal electrodes. We found that the voltage generated for semiconducting nanotubes was three times greater than that for metallic nanotubes and that both types of SWCNTs showed an unexpected reversal in signal sign, likely due to the switching of the major carrier between holes and electrons. These generated voltages increased proportionally for both types of SWCNTs as functions of flow velocity and ionic concentration.