Influence of fluoropolymer surface wettability on electrowetting display performance

Amorphous fluoropolymer (FP), as a material for both insulating and hydrophobic coating, plays an essential role in electrowetting displays (EWD). In this work, three FPs based on Teflon AF1600, Hyflon AD60 and Cytop 809A were studied according to their influence on the EWD performance. Both water/air and oil/water contact angles were utilized to compare the surface wettability of these three FPs. Reversible and fast optical switch could be achieved in the EWD devices fabricated using all three FPs; however, the less hydrophobicity of the Cytop 809A surface would lead to a slower Off-switching speed or even incomplete close of the micro-pixels. The reflow temperature for restoring the hydrophobicity of fluoropolymer surface should be high enough to achieve a sufficient surface recovery, and at the same time avoid inducing failures like film dislocation and breakdown. The optimal reflow temperature has been investigated and evaluated based on the EWD performance. This work would help us deeply understand the surface wettability effect on fluidic behavior in micro-pixels driven by electrowetting, and related optical phenomena in EWDs as well.