A New Model for Capillary Imbibition With Asymmetric Wettability Walls

The imbibition dynamics is controlled by energy dissipation mechanisms and influenced by asymmetric wettability in a nanochannel. This work proposes a new theoretical model for capillary imbibition while the imbibition dynamics are described by a combined model of the Lucas-Washburn equation and the Cox-Voinov law considering velocity-dependent contact angles. Most of previous studies on capillary imbibition have focused on channels with walls of homogeneous and symmetric wettability. The imbibition dynamics in channels with asymmetric wettability is not well understood. Meanwhile, the energy dissipation mechanism in capillary imbibition also remains to be elucidated. Here, theoretical analysis and molecular dynamics simulations are combined to investigate the energy dissipation mechanism of capillary imbibition in nanochannels. The model may have a wide range of applications, for example, in development of novel materials and microfluidic chips, control of transport of water molecules and ions in cement-based materials, and regulating the spontaneous imbibition of hydraulicfracturing fluids in shale reservoirs.