8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P7.88Thu 811:10-14:00The geometrical representation of the superhydrophobicdrop profile and its applicationsJoonsik Park 11 Korea Institute of Machinery and Materials, Mechatronics dong 314ho, Yuseong-gu305343, Daejeon, South KoreaSince the superhydrophobicity has been discovered from lotus leaf and gained a great attentionin its applicability in self cleaning effect, the scale of superhydrophobicity is generally evaluatedthrough the drop-surface contact angle, which can be easily predicted from Cassie-Baxter equation.While the use of contact angle is effective in drawing a distinction between hydrophilic andhydrophobic surface, in case of a superhydrophobic surface whose contact angle exceeds 150 ◦ theassessment of the surface cannot be justly made within 30 ◦ scale between 150 ◦ to 180 ◦ , especiallyconsidering that measurement of a higher contact angle of a near-spherical drop becomes increasinglysubjective. This work shows a simple geometrical representation of the superhydrophobicdrop that satisfies the Young-Laplace condition at the boundary and the minimization of the freeenergy. Given the interfacial energies, the contact areal fraction and the drop volume, the closelyapproximated profile of the drop can be calculated. From the drop profile, the ratio of the dropheight to the maximum diameter represents the drop’s sphere-likeness. Using the geometricalprofile, the current progress in understanding the several interfacial phenomena such as the heatexchange and the surface’s robustness against the impregnation are discussed.88