Measurement of the contact angle of a water droplet on a flat surface

PHYS 324

Uriel Vazquez1, Chi-cheng Chiu, cxc058300@utdallas.edu2, Wataru Shinoda, w.shinoda@aist.go.jp3, D. Vladimir Perez, vladimirck@gmail.com4, Preston B Moore, p.moore@usp.edu4, and Steven O. Nielsen, steven.nielsen@utdallas.edu5. (1) Centro de Investigacion en Matematicas, Centro de Investigacion en Matematicas, AP 402, Guanajuato, 36240, Mexico, (2) Department of Chemistry, The University of Texas at Dallas, 2601 North Floyd Rd., Richardson, TX 75080-0688, (3) Research Institute for Computational Sciences, National Institute of Advanced Industrial Science and Technology, Central 2, 1-1-1 Umezono, Tsukuba, 305-0035, Japan, (4) Department of Chemistry and Biochemistry, West Center of Computational Chemistry and Drug Design, University of the Sciences in Philadelphia, 600 S 43rd Street, Phila, PA 19104, (5) Department of Chemistry and The Alan G. MacDiarmid NanoTech Institute, The University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080
The surface tension of an oil/water interface is recognized as having tremendous potential to control the organization and assembly of nanoparticles. However, there is no way to measure the surface tension at a nanoscale level directly. It is possible to relate the surface tension with the contact angle, but current theory is flawed and is not applicable to nanoparticles. We report on our progress to correct this theory, specifically inclusion of three-phase contributions to the line tension.

We also report three methods to measure the contact angle of a water droplet on a flat surface. The first method, the radius of the droplet is a measure in function of its height from which the contact angle is estimated. The second method, several perpendicular slices are taken, then spline curves are used to adjust the border molecules. Finally, the third method, the density profile of the liquid/vapor interface is used. We compare and contrast these three methods.

 

PHYS Poster Session - Water Mediated Interactions
7:30 PM-10:00 PM, Wednesday, August 20, 2008 Pennsylvania Convention Center -- Hall C, Poster

Division of Physical Chemistry

The 236th ACS National Meeting, Philadelphia, PA, August 17-21, 2008