Surface wettability plays an enormous role in many real-life applications ranging from biological to technological applications. It is a property that governs the interaction between the solid and liquid phases. For surface wettability study and characterization, contact angle measurement has been an indispensable tool due to its simplicity and versatility. A common approach to assess wettability is based on the sessile droplet contact angle. Despite its experimental simplicity, caution is required in measuring and interpreting the sessile contact angle as a wettability metric.
The present talk will focus on various measurement techniques for surface wettability encompassing the sessile drop method for static contact angle measurement, advancing/receding or quasi-static contact angle measurement, and sliding contact angle. Time-varying static contact angle and the effect of various surface inhomogeneity on the contact angle will be touched in the talk. The talk will also present measuring techniques for other surface parameters such as interfacial tension and surface-free energy. Since the area of wettability study is large, the presentation will try to cover the fundamentals of the contact angle and the different droplet profiles ranging from symmetric to asymmetric droplet profiles. Different curve fitting methods such as tangent, ellipse, and circle methods along with Young’s method for contact angle measurement will be brief. By and large, the talk will cover the dos and don’ts while measuring surface contact angle using a contact angle meter in manual and semi-automatic operating systems. The new challenges faced while capturing contact angles for hierarchical modified surfaces will be complementary to the talk. ​