On the kinetics of the capillary imbibition of a simple fluid through a designed nanochannel using the molecular dynamics simulation approach

A molecular dynamics (MD) approach was employed to simulate the imbibition of a designed nanopore by a simple fluid (i.e., a Lennard–Jones (LJ) fluid). The length of imbibition as a function of time for various interactions between the LJ fluid and the pore wall was recorded for this system (i.e., the LJ fluid and the nanopore). By and large, the kinetics of imbibition was successfully described by the Lucas–Washburn (LW) equation, although deviation from it was observed in some cases. This lack of agreement is due to the neglect of the dynamic contact angle (DCA) in the LW equation. Two commonly used models (i.e., hydrodynamic and molecular-kinetic (MK) models) were thus employed to calculate the DCA. It is demonstrated that the MK model is able to justify the simulation results in which are not in good agreement with the simple LW equation. However, the hydrodynamic model is not capable of doing that. Further investigation of the MD simulation data revealed an interesting fact that there is a direct relationship between the wall–fluid interaction and the speed of the capillary imbibition. More evidence to support this claim is presented.

A computational approach based on molecular dynamics (MD) simulation is suggested to evaluate the kinetics of the capillary imbibition of a simple fluid at nanoscale emphasizing the effect of the dynamic contact angle on this phenomenon.Figure optionsDownload high-quality image (33 K)Download as PowerPoint slideResearch highlights
► A molecular dynamics (MD) simulation approach is employed to assess the kinetics of capillary imbibition of a simple fluid through a designed nanochannel. Since we did use the dimensionless units, the obtained results could employ for a wide range of problems in this field.
► Generally, the kinetics of imbibition is successfully described by the Lucas–Washburn (LW) equation.
► The MK model is able to justify the simulation results in which are not in good agreement with the simple LW equation. However, the hydrodynamic model is not capable of doing that.
► There is a direct relationship between the wall–fluid interaction and the speed of the capillary imbibition.