Abstract
Fluoropolymers play an essential role in electrowetting (EW) systems. However, no fluoropolymer possesses the desirable properties of both hydrophobicity and dielectric strength. In this study, for the first time, we report the integration of two representative fluoropolymers—namely, Teflon AF (AF 1600X) and Cytop (Cytop 809A)—into one bifunctionalized dielectric nanolayer. Within this nanolayer, both the superior hydrophobicity of Teflon AF and the excellent dielectric strength of Cytop were able to be retained. Each composed of a 0.5 μm Cytop bottom layer and a 0.06 μm Teflon AF top layer, the fabricated composite nanolayers showed a high withstand voltage of ~70 V (a dielectric strength of 125 V/μm) and a high water contact angle of ~120°. The electrowetting and dielectric properties of various film thicknesses were also systemically investigated. Through detailed study, it was observed that the thicker Teflon AF top layers produced no obvious enhancement of the Cytop/Teflon AF stack.
Highlights
Electrowetting (EW) refers to the phenomenon of altering the surface wettability of an electrode or dielectric layer with an applied electric field [1,2]
As an approach to manipulating minute fluids, electrowetting has attracted a great deal of attention for its application within reflective display devices [3,4], lab-on-a-chip systems [5,6], and optic lenses [7,8]
In 1993, Berge et al introduced the concept of electrowetting on dielectric (EWOD), in which a thin insulating layer is used to separate the conductive liquid from the electrode, preventing electrolysis [10]
Summary
Electrowetting (EW) refers to the phenomenon of altering the surface wettability of an electrode or dielectric layer with an applied electric field [1,2]. Teflon AF’s surface energy, producing a higher initial contact angle, larger contact angle variation under applied voltage, and better EW device performance than Cytop, which contains only –CF2 groups [27]. We integrated the advantages of the two fluoropolymer candidates into a electrowetting and leakage current of films with both single and composite materials were composite layer, namely, an insulating Cytop bottom layer and a hydrophobic Teflon AF top coating. In contrast to the fabrication of parylene or inorganic materials, which require extra stack maintained good dielectric strength, created a more hydrophobic surface, and was easy to techniques that are more complex and more inefficient than wet coating (e.g., spin coating) [12], this fabricate, making it greatly superior to parylene and fluoropolymer-integrated films. Of this composite provides a simple and practical strategy for the creation of a workable and robust dielectric layer in Methods electrowetting systems
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