Carbon Nanotube Flow Sensors

TLDR

The authors propose an explanation based on pulsating asymmetric ratchets. The mechanism involves direct forcing of free charge carriers in the nanotubes by the fluctuating Coulombic field of the flowing liquid, modeled as pulsating asymmetric ratchets. The flow of liquid on single‑walled carbon nanotube bundles induces a voltage that follows a logarithmic velocity dependence over six decades, with magnitude sensitive to ionic conductivity and liquid polarity, highlighting potential for flow sensing and energy conversion.

Abstract

We report that the flow of a liquid on single-walled carbon nanotube bundles induces a voltage in the sample along the direction of the flow. The voltage that was produced fit a logarithmic velocity dependence over nearly six decades of velocity. The magnitude of the voltage depended sensitively on the ionic conductivity and on the polar nature of the liquid. Our measurements suggest that the dominant mechanism responsible for this highly nonlinear response involves a direct forcing of the free charge carriers in the nanotubes by the fluctuating Coulombic field of the liquid flowing past the nanotubes. We propose an explanation based on pulsating asymmetric ratchets. Our work highlights the device potential for nanotubes as sensitive flow sensors and for energy conversion.