LAUSR

Surface tension driven droplet transport in an open surface is increasingly becoming popular for various microfluidic applications. In this work, efficient transport of a glycerin droplet on an open wettability gradient surface with controlled wettability and confinement is numerically investigated. Nondimensional track width w* (ratio of the width of the wettability gradient track w and the initial droplet diameter d0) of a wettability gradient track laid on a superhydrophobic background represents wettability confinement. A lower value of w* represents higher wettability confinement. Droplet behavior changes for different wettability confinements and gradients of the track. It is found that droplet velocity is a function of the wettability confinement and the gradient; droplet transport velocity is maximum for w* = 0.8. Higher confinement (w* < 0.8) leads to a significant reduction in droplet velocity. Droplet transport characteristics on hydrophilic–superhydrophilic, hydrophobic–superhydrophilic, and s...