  Macroscale experiments show that a train of two immiscible liquid drops, a
bislug, can spontaneously move in a capillary tube because of surface tension
asymmetries. We use molecular dynamics simulation of Lennard-Jones fluids to
demonstrate this phenomenon for NVT ensembles in sub-micron tubes. We
deliberately tune the strength of intermolecular forces and control the
velocity of bislug in different wetting and viscosity conditions. We compute
the velocity profile of particles across the tube, and explain the origin of
deviations from the classical parabolae. We show that the self-generated
molecular flow resembles the Poiseuille law when the ratio of the tube radius
to its length is less than a critical value.
