Equilibrium drop surface profiles in electric fields
(F. Mugele and J. Buehrle)
In this article we give an overview over the equilibrium shapes of liquid drops close to the three phase contact line in a typical electrowetting configuration. The most important numerical and theoretical results are the following:
•The macroscopic apparent contact angle follows the electrowetting equation, as expected based on Lippmann’s ideas.
•On a scale smaller than the thickness of the insulator, the local contact angle is equal to Young’s angle, independent of the applied voltage.
•The curvature of the drop surface diverges algebraically upon approaching the contact line with an exponent 0>>-1.
These findings are verified experimentally using water drops in silicone oil on top of teflon substrates with a variable thickness ranging between few micrometers and 0.15mm.