Three-phase contact line expansion during air bubble attachment to hydrophobic solid surface – experiment and modeling

Kinetics of spreading of the three-phase contact hole (dewetting) formed by an air bubble colliding with hydrophobic solid surface, after rupture of intervening liquid film, was studied both experimentally and numerically. During experiments it was found that evolution of the TPC line diameter with time occurs with characteristic S-shaped trend which, in consequence, causing rather unexpected maxima at the TPC line spreading velocity curves. It was determined that position of this maximum appears after 1-2 ms after TPC hole formation and its position (in respect to time) depends on the bubble diameter. In solution of surface-active substance this maximum was much smoother and longer. By means of complementary numerical calculations the source of maxima existence and differences in their position and shapes were explained. It was concluded that this effect has only hydrodynamic origin, caused by different course of bubble shape pulsations during TPC line formation and spreading, which depends on degree of liquid/gas interface immobilization (fluidity retardation).