Molecular Diffusion Replaces Capillary Pumping in Phase-Change Driven Nanopumps

TL;DR

This paper introduces a phase-change driven nanopump that operates nearly isothermally, replacing traditional capillary pumping with a molecular diffusion mechanism at the nanoscale, suitable for NEMS and MEMS applications.

Contribution

It demonstrates that molecular diffusion can replace capillary pumping in nano-sized pumps, enabling efficient, isothermal fluid transport without meniscus structures.

Findings

Efficient pump operation despite absence of capillary menisci

Molecular diffusion replaces capillary action at nanoscale

Suitable for continuous gas separation in NEMS/MEMS

Abstract

Nano-scale fluid transport has vast applications spanning from water desalination to biotechnology [1,2]. It is possible to pump fluids in nano-conduits using pressure gradients [3], thermal methods [4], electric [5,6] and magnetic fields [7], and with manipulations of surface chemistry and electric fields [8-10]. Inspired by the capillary-driven phase change heat transfer devices, we present a phase-change driven nanopump operating almost isothermally. Meticulous computational experiments on different sized nanopumps revealed efficient operation of the pump despite the reduction in system size that extinguishes capillary pumping by annihilating the liquid meniscus structures. Measuring the density distribution of liquid in cross sections near to the evaporating and condensing liquid-vapor interfaces, we discovered that phase change induced molecular scale mass diffusion mechanism replaces the capillary pumping in the absence of meniscus structures. Therefore, proposed pumps can serve as a part of both nanoelectromechanical (NEMS) and microelectromechanical systems (MEMS) with similar working efficiencies, and can be used for continuous gas separation applications.