We use a mesoscale simulation to measure the strength of the velocity flux needed to push a polymer into a narrow channel. We find excellent agreement with the prediction by T. Sakaue, E. Rapha€ el, P.G. de Gennes and F. Brochard-Wyart, Europhys. Lett., 2009, 72, 83, based on a de Gennes blob model of the polymer, that the critical velocity flux for translocation depends linearly on the temperature, but is independent of the length of the polymer chain or the width of the channel.

The viscosity-temperature relation is determined for the water models SPC/E, TIP4P, TIP4P/Ew, and TIP4P/2005 by considering Poiseuille flow inside a nano-channel using molecular dynamics. The viscosity is determined by fitting the resulting velocity profile (away from the walls) to the continuum solution for a Newtonian fluid and then compared to experimental values. The results show that the TIP4P/2005 model gives the best prediction of the viscosity for the complete range of temperatures for liquid water, and thus it is the preferred water model of these considered here for simulations where the magnitude of viscosity is crucial. On the other hand, with the TIP4P model, the viscosity is severely underpredicted, and overall the model performed worst, whereas the SPC/E and TIP4P/Ew models perform moderately.

In this paper, we demonstrate for the first time that insulative dielectrophoresis can induce size-dependent trajectories of DNA macromolecules. We experimentally use ͑48.5 kbp͒ and T4GT7 ͑165.6 kbp͒ DNA molecules flowing continuously around a sharp corner inside fluidic channels with a depth of 0.4 m. Numerical simulation of the electrokinetic force distribution inside the channels is in qualitative agreement with our experimentally observed trajectories. We discuss a possible physical mechanism for the DNA polarization and dielectrophoresis inside confining channels, based on the observed dielectrophoresis responses due to different DNA sizes and various electric fields applied between the inlet and the outlet. The proposed physical mechanism indicates that further extensive investigations, both theoretically and experimentally, would be very useful to better elucidate the forces involved at DNA dielectrophoresis. When applied for size-based sorting of DNA molecules, our sorting method offers two major advantages compared to earlier attempts with insulative dielectrophoresis: Its continuous operation allows for highthroughput analysis, and it only requires electric field strengths as low as ϳ10 V / cm.