Needle-embedded sessile drop method

Advancing and receding contact angle have been known for more than a century to be the maximum and minimum angle that can be measured reliably and reproducibly when liquid is added to or withdrawn from a liquid droplet at a very slow rate [4,5]. Most of the current goniometer is equipped with an automated dosing system, where drop volume and rate of addition/withdraw can be controlled very precisely. The needle-embedded sessile drop method is the most frequently used method and is schematically shown in Fig. 2.15. 

2 Contact Angle Measurements and Surface Characterization Techniques 

---