On metastable regimes of dynamic wetting

An explanation is proposed for a non-unique dependence of the dynamic contact angle on the wetting speed observed experimentally for some liquid-solid systems at low wetting speeds. The key idea is that the flow pattern near the wetting line, which follows from previously developed theory, suggests the possibility of a microscopic mass flux from the three-phase-interaction zone into the bulk thus causing `imperfect rolling' of the spreading liquid. The resultant `starvation' of the liquid-solid interface gives rise to a higher value of the contact angle. The above flow pattern turns into the regular one at a certain wetting speed thus determining the region where the metastable regimes of wetting can be observed.