Low voltage electrowetting using thin fluoroploymer films

J Colloid Interface Sci. 2006 Nov 15;303(2):517-24. doi: 10.1016/j.jcis.2006.08.004. Epub 2006 Aug 10.


This paper investigates the nonideal electrowetting behavior of thin fluoroploymer films. Results are presented for a three phase system consisting of: (1) an aqueous water droplet containing sodium dodecyl sulfate (SDS), (2) phosphorous-doped silicon topped with SiO2 and an amorphous fluoroploymer (aFP) insulating top layer on which the droplet is situated, and (3) a dodecane oil that surrounds the droplet. The presented measurements indicate that the electrowetting equation is valid down to a 6 nm thick aFP film on a 11 nm thick SiO2. At this dielectric thickness, a remarkable contact angle change of over 100 degrees can be achieved with an applied voltage less than 3 V across the system. The data also shows that for this water/surfactant/oil system, contact angle saturation is independent of the electric field, and is reached when the surface energy of the solid-water interface approaches zero.