Co-axially Rotating Carbon Nanotubes: A Novel Mechanism for Nanoscale Pumping of Fluids

Carbon nanotubes (CNT) are one of the most widely used and ideal nanofluidic devices, especially for desalination. With an ever-increasing scarcity of freshwater, there is a strong need to reduce the energy cost associated with pumping water across nanotube membranes, which are the most energy efficient devices for desalination. It becomes important to study novel mechanisms used to transport water molecules through carbon nanotubes and to compare the effectiveness and rate of fluid flow provided by them. In this study, we have considered three popular non-conventional mechanisms for pumping water through a CNT, namely, thermally driven flows, by rotating chiral CNT and by applying AC electric field across a carbon nanotube. Using molecular dynamics simulations, these mechanisms are studied to understand the flow behavior inside carbon nanotubes. Based on the promising results from the rotating chiral CNT mechanism of water pumping, we investigate this mechanism thoroughly using liquid argon to save on computational time. We also propose a simple addition to the device in the form of a coaxially rotating nanotube, which was found to increase the flux of argon at certain rotational speeds. We then extend this work to water molecules to find if the coaxial CNT system holds much promise for pumping water at nanoscales.