Charge Transfer Quenching and Maximum of a Liquid-Air Contact Line Moving over a Hydrophobic Surface.

Charge transfer when a hydrophobic fluoropolymer surface comes in contact with salt solutions of water, methanol, and glycerol is investigated. It is found that the charge transfer decreases faster with an increasing fraction of glycerol in water than it does with methanol in water. It is also demonstrated that for both mixtures, the charge transfer increases with the amount of added sodium chloride for small concentrations but then reaches a maximum and subsequently decreases.

Wetting of porous thin films exhibiting large contact angles.

Porous solid films that promote large apparent contact angles are interesting systems since their wetting properties are dependent on both the surface structure and water penetration into the film. In this study, a parahydrophobic coating is made by sequential dip coating of titanium dioxide nanoparticles and stearic acid on polished copper substrates. The apparent contact angles are determined using the tilted plate method, and it is found that the liquid-vapor interaction decreases and water droplets are more likely to move off the film when the number of coated layers increases.

Ion Concentration Influences the Charge Transfer Due to a Water-Air Contact Line Moving over a Hydrophobic Surface: Charge Measurements and Theoretical Models.

A metal electrode covered by an inert, hydrophobic polymer surface is dipped into water, and the charge transfer was measured as a function of ion concentration for different chlorides, sulfates, and nitrates. A generic behavior is observed wherein the charge transfer first increases and then decreases as the ion concentration increases. However, for acids, the charge transfer decreases monotonously with concentration and even reverses polarity.

Influence of Salt Concentration on Charge Transfer When a Water Front Moves across a Junction between a Hydrophobic Dielectric and a Metal Electrode.

An energy-harvesting device based on water moving across the junction between a hydrophobic dielectric and a metal electrode is demonstrated. The charge transfer due to contact electrification as the junction is dipped vertically into water is investigated. Experiments combined with finite element simulations reveal how the electrode voltage changes during the dipping process.

The Influence of Microscale Surface Roughness on Water-Droplet Contact Electrification.

When water comes in contact with a hydrophobic fluoropolymer, a triboelectric charge tends to form on the surface. Here, it is investigated how the triboelectric charge formed upon contact with water drops depends on the microscale surface statistics of the polymer. In particular, it is found that the transition to a superhydrophobic fakir state results in a considerable reduction in triboelectric contact charge, due to a reduced liquid?solid contact area.