# Molecular diffusion replaces capillary pumping in phase-change-driven nanopumps

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## Abstract

Inspired by the capillary-driven heat transfer devices, we present a phase-change-driven nanopump operating almost isothermally. 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 near 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 as long as the liquid wets the walls of the capillary conduit. Therefore, proposed pumps can serve as a part of both nanoelectromechanical and microelectromechanical systems with similar working efficiencies.

## Keywords

Nanopump Phase change Molecular dynamics Nanoscale fluid transport Evaporating meniscus Capillary pumping## Notes

### Acknowledgements

Authors thank Prof. BoHung Kim of University of Ulsan for the helpful discussions. Y.A. acknowledges the financial support of ASELSAN Inc. under scholarship program for postgraduate studies. Computations were carried out using high-performance computing facilities of Center for Scientific Computation at Southern Methodist University.

## Supplementary material

Supplementary material 1 (MP4 28,490 kb)

Supplementary material 2 (MP4 26,570 kb)

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