Wetting and dewetting play an important role in the natural environment and in many technical applications, e.g. cleaning surfaces. The wetting behavior of a single component liquid has been investigated in many studies. The wetting characteristics of surfactant solutions has not been in the focus of experimental attached less attention. Some efforts were made to gain deeper insight of the physical mechanisms, e.g. it was shown that there is a strong influence of the surfactant on the dynamic contact angle.
The contact angle decrease with increasing surfactant concentration. The effect on the dynamic contact angle is much stronger than expected from the changed in surface tension. Simple estimates show that the driving mechanism is most probably due to Marangoni stresses along the free liquid-air interface. These stresses couple to the hydrodynamic flow and induce changes in the flow profile close to the contact line. The range of this region is typically 100 µm. We present results of the dynamic contact angle as a function of receding velocity and surfactant concentration and correlate them to the measured changes in the flow field close to the contact line.
Selected References:
Fell, D., N. Pawanrat, E. Bonaccurso, H.-J. Butt and G. K. Auernhammer. "Influence of surfactant transport suppression on dynamic contact angle hysteresis." Colloid Polym. Sci. 291(2): 361-366.
Fell, D., G. K. Auernhammer, E. Bonaccurso, C. Liu, R. Sokuler and H.-J. Butt. "Influence of Surfactant Concentration and Background Salt on Forced Dynamic Wetting and Dewetting." Langmuir 27(6): 2112-2117.
auhammer@mpip-mainz.mpg.de
