Thermoelectric Properties of Fe0.2Co3.8Sb12-xTex ... - Physics

A new model of flow induced voltage generation in
Carbon Nanotubes based on van der Waals friction
K. Sathya Narayanan and A.K. Sood
Department of Physics, Indian Institute of Science, Bangalore-560012, India.
We present here a simple model to explain the plethora of experimental results
concerning the flow induced voltage generation in carbon nanotubes which, thus
far, have been only inadequately explained. To do this, we consider the zeroth
order picture of the alignment of water molecules confined inside the nanotubes
subject to the force field exerted by the imposed flow outside the tubes. These
aligned water molecules polarize the nanotubes containing them, thereby
inducing a potential difference across its length. Importantly, we model this force
field as due to the van der Waals (VdW) frictional stress that exists between any
two dissipating dielectric media in relative motion with each other, which, here, is
between the confined water molecules and the flowing liquid. This simple model,
surprisingly, captures the qualitative behavior observed in the experiments such
as: induced voltage as a function of flow velocity, gate voltage and electrolyte
concentration. Further, this also explains the apparently unrelated non-local
voltage generation observed in isolated carbon nanotubes when filled with water
vapor. We extend this even more to try and understand the intriguing
phenomenon of flow induced voltage generation in carbon nanotubes trapped in
Ice, wherein the flowing medium is well isolated from the nanotubes by a
sufficiently thick layer of ice. We believe that this understanding is crucial to
optimization of future energy harvesting devices.