DPD simulation of the reciprocating translocation behaviour of polymer chain in a microchannel under variable external force

Abstract

ABSTRACT In this study, an investigation has been carried out regarding the reciprocating translocation (i.e. back and forth motion) of a polymer chain in a microchannel. External force is one of the important factors in the movement of the polymer chain. In this investigation, variable forces are applied to the polymer chain and all fluid particles in which at a certain time, the direction of the force and the movement will change in this simulation. The behaviour and the properties of the chain, such as the radius of gyration, the centre of mass velocity and the amount of translocation, have been examined in this reciprocating movement. Based on the present results, when employing a longer polymer chain and especially applying the force on the polymer and fluid particles, due to the inertia effect, it would not be easily possible to stop the polymer chain. Consequently, changing the direction of polymer motion would not instantly occur by changing the force direction. In fact, some amount of displacement and lost time (LT) (around 6 dissipative particle dynamics units out of a total time of 40) will be associated with the case of applying force on just a polymer chain and imposing variable external force on all particles, LT has increased dramatically (dimensionless LT parameter is around 50%). The present method is a suitable tool for simulating the variable movement of polymer for the design of micro-actuators or polymer sensors.