Multi-Wall Carbon Nanotubes for Flow-Induced Voltage Generation (Preprint)

Recently it has been reported that voltage can be generated by passing fluids over single-walled carbon nanotube (SWCNT) arrays with potential application to flow sensors with a large dynamic range. The present work investigates voltage generation properties of multi-walled carbon nanotubes (MWCNT) as a function of the relative orientation of the nanotube array with respect to the flow direction, flow velocity, and solution ionic strength. It was found that the flow-induced voltage can be significantly enhanced by aligning the nanotubes along the flow direction, increasing the flow velocity and/or the ionic strength of the flowing liquid. A flow-induced voltage of 30mV, which is 15 times higher than the highest voltage reported for single-wall carbon nanotubes, has been generated from our perpendicularly-aligned MWCNT in an aqueous solution of 1 M NaCl at a relatively low flow velocity of 0.0005 m/s. The results are generally consistent with the pulsating asymmetric ratcheting mechanism proposed for SWCNT arrays, in which an asymmetrical spatial distributed strain forms from interactions with the polar and ionic species at the tube surface and is driven along the tube by the fluid flow. The original document contains color images. All DTIC reproductions will be in black and white. Prepared in cooperation with University of Dayton, Dept. of Chemical and Materials Eng., Dayton, OH.