Flow-induced voltage and current generation in carbon nanotubes

TL;DR

This paper presents experimental and theoretical insights into flow-induced voltages and currents in carbon nanotubes, revealing a sublinear response explained by a Langevin-equation model involving ionic fluctuations and charge carrier dynamics.

Contribution

It introduces a new Langevin-equation based model for flow-induced electrical responses in nanotubes, challenging conventional streaming potential explanations.

Findings

Flow-induced voltage response is nearly logarithmic in flow speed.

Direction of induced current can be controlled by electrochemical bias.

Theoretical model aligns with experimental sublinear response.

Abstract

New experimental results, and a plausible theoretical understanding thereof, are presented for the flow-induced currents and voltages observed in single-walled carbon nanotube samples. In our experiments, the electrical response was found to be strongly sublinear -- nearly logarithmic -- in the flow speed over a wide range, and its direction could be controlled by an electrochemical biasing of the nanotubes. These experimental findings are inconsistent with the conventional idea of a streaming potential as the efficient cause. Here we present a new, physically appealing, Langevin-equation based treatment of the nanotube charge carriers, assumed to be moving under coulombic forcing by the correlated ionic fluctuations, advected by the liquid in flow. The resulting 'Doppler-shifted' force-force correlation, as seen by the charge carriers drifting in the nanotube, is shown to give a strongly sublinear response, broadly in agreement with experiments.