Effect of triple-phase contact line on contact angle hysteresis

Recent studies have shown that the triple-phase contact line has critical effect on the contact angle hysteresis of surfaces. In this study, patterned surfaces with various surface structures of different area fractions were prepared by electron etching on a silicon wafer. The advancing angle, receding angle and hysteresis angle of these surfaces were measured. Our experimental results showed that while the geometry of microstructure and contact line have a minor effect on the advancing angle, they have a significant effect on the receding angle and thus the hysteresis angle. We have shown that the effect of microstructure and the contact line can be described by a quantitative parameter termed the triple-phase line ratio. The theoretical predictions were in good agreement with our experimental results.