Effect of some geometrical characteristics of asymmetric nanochannels on acceleration-driven flow
M Sahebi and AR Azimian, MICROFLUIDICS AND NANOFLUIDICS, 18, 1155-1163 (2015).
The geometrical effects of a rough wall asymmetric conical nanochannel on the mass flux of a simple liquid flow are studied via molecular dynamics simulations. Both static and dynamic driving forces are applied to each fluid atom to form a so-called acceleration or force-driven flow. The mean-zero time-dependent periodic dynamic force is applied to induce a net flow as a ratchet. The results show that when the static driving forces are strong enough, there is a symmetry breakdown between mass fluxes in divergent and convergent channels. Thus, by applying a dynamic force, a net mass flux is induced (toward the convergent direction). In this paper, the effects of three different geometrical parameters are investigated. Simulation results indicate that (1) if the radiuses of the two sides of the channel are kept constant, there is a certain length in which the net flux induced by ratchet motion has a maximum value; (2) when the length and the radius of the smaller area of the channel are kept constant, increasing the other side radius generally increases the flux in ratchet motion, and (3) increasing channel length in constant apex angle increases the flux in ratchet motion. The simulation results are justified with molecular principals to provide a better understanding of flow in such nanochannels. The results can be applicable in designing and optimizing nanofluidic devices such as thermocapillary pumps, ion pumps, and Brownian pumps.
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