Abstract
Electrowetting-on-dielectric is a preferred option in practical applications of the electrowetting phenomenon but limited by dielectric and breakdown performances of the dielectric layer. In the present work, a ceramic/polymer nanocomposite as a novel dielectric layer is developed to intensify the overall electrowetting performances by multiscale interface effect. Hereinto, surface fluoro-modified ZrO2 nanoparticles (mZrO2) are dispersed well in AF 1600 matrix to form a mZrO2@AF 1600 nanocomposite. The small addition of mZrO2 improves the dielectric constant of the nanocomposite, and the experimental value is larger than the theoretical value calculated by Maxwell–Garnett model, but fits well with the Rahaman–Khastgir model. The molecular dynamics simulations with the explicit model further verify the interfacial effect. Meanwhile, double contact angle modulation and higher breakdown field strength (Eb) are obtained. For the three-layer sandwich structure, both the top and bottom AF 1600 layer decrease the surface roughness for better electrowetting reproducibility and wider wettability modulation. The Forlani–Minnaja theory related to the empirical relationship between Eb and thickness of dielectric layer fit well with the monolayer structure, but cannot be applied in multi-layer structures. A new relationship is proposed to guide the design of dielectric multi-layers with high breakdown field strength.
Highlights
Electrowetting is a microfluidic phenomenon that tunes the surface tension of the liquid droplet on the electrode to enable large and reversible contact angle variations via applied electric field [1,2]
F is the measurement frequency (i.e., 1 kHz), and M is the morphological factor/fitting where parameter, depending on shape, size, dispersion, distribution, and permittivity of particulate inclusion and host medium. It means that the improvement of dielectric constant at low modified ZrO2 nanoparticles (mZrO2) content attributes to the interfacial polarization
Surface-fluorinated modification of ZrO2 nanoparticles improves the compatibility of nanoparticles and the AF 1600 matrix to increase the dielectric constant of mZrO2 @AF 1600 nanocomposite (2.02, about 31% higher than pure AF 1600’s) at low content, followed by double contact angle modulation and higher breakdown field strength
Summary
Electrowetting is a microfluidic phenomenon that tunes the surface tension of the liquid droplet on the electrode to enable large and reversible contact angle variations via applied electric field [1,2]. High dielectric constant of layer material can strengthen the electrowetting effect in high electric fields. Dielectric constant of layer material can strengthen the electrowetting effect in high electric fields. Once an electric field is applied, electric charges inevitably concentrate on the surface of hydrophobic layer with much lower applied, electric charges inevitably concentrate on the surface of hydrophobic layer with much lower dielectric constant than the dielectric layer, accelerating the lose efficiency. We focus on integrating both inorganic and polymeric insulating materials into into one highly compatible solution, and preparing the polymer nanocomposite. Designing sandwich-structured ceramic/polymer nanocomposites can significantly enhance breakdown fieldand strength [37,38].field.
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