Theoretical analysis for dynamic contact angle hysteresis on chemically patterned surfaces

A dynamic wetting problem is studied for a moving thin fiber inserted in fluid and with a chemically inhomogeneous surface. A reduced model is derived for contact angle hysteresis by using the Onsager principle as an approximation tool. The model is simple and captures the essential dynamics of the contact angle. From this model, we derive an upper bound of the advancing contact angle and a lower bound of the receding angle, which are verified by numerical simulations. The results are consistent with the quasi-static results. The model can also be used to understand the asymmetric dependence of the advancing and receding contact angles on the fiber velocity, which was observed recently in the physical experiments reported in the work of Guan et al. ["Asymmetric and speed-dependent capillary force hysteresis and relaxation of a suddenly stopped moving contact line," Phys. Rev. Lett. 116, 066102 (2016)].