Effects of fiber wettability and size on droplet detachment residue

Abstract

This paper reports on an experimental study devised to better our understanding of the role of Young–Laplace contact angle (YLCA), fiber diameter, fluid viscosity, or droplet size on the volume of droplet residue left on a fiber after droplet detachment. This was made possible using an aqueous ferrofluid droplet deposited on a horizontal filament in a controllable magnetic field. Droplet detachment process was imaged using a high-speed camera and the images were used to obtain residue volume and droplet detachment time. It was found that residue volume decreases with increasing filament’s YLCA or droplet viscosity (in a viscosity range of 1–5.5 mPa s), but it increases with increasing fiber diameter or remains unchanged when increasing droplet volume. Droplet detachment time was found to increase with droplet volume or fiber diameter but remained unaffected by increasing droplet viscosity from 1 to 5.5 mPa s. In addition, droplet detachment time was found to decrease with increasing YLCA of the fiber.