Novel Approach to Measuring the Droplet Detachment Force from Fibers

Abstract

Determining the force required to detach a droplet from a fiber or from an assembly of fibers is of great importance to many applications. A novel technique is developed in this work to measure this force experimentally by using ferrofluid droplets in a magnetic field. Unlike previous methods reported in the literature, our technique does not require air flow or a mechanical object to detach the droplet from the fiber(s); therefore, it simplifies the experiment and also allows one to study the capillarity of the droplet-fiber system in a more isolated environment. In this article, we investigated the effects of the relative angle between intersecting fibers on the force required to detach a droplet from the fibers in the in-plane or out-of-plane direction. The in-plane and through-plane detachment forces were also predicted via numerical simulation and compared with the experimental results. Good agreement was observed between the numerical and experimental results. It was found that the relative angle between intersecting fibers has no significant effect on the detachment force in the out-of-plane direction. However, the detachment force in the in-plane direction depends strongly on the relative angle between the fibers, and it increases as this angle increases.

Effects of roughness on droplet apparent contact angles on a fiber

“…is number that may vary between zero and one, and it characterizes the impact of the YLCA on detachment force--a parameter that can only be determined accurately in a future investigation. Using such relationships, one can see that the droplet detachment forces reported here for smooth fibers are in good agreement with those reposted previously in [28] for droplets with different diameters and fluid properties deposited on fibers with different diameters.…”

“…The surface energy minimization method implemented in the Surface Evolver (SE) finite element code is used to simulate the 3-D shape of a droplet deposited on a rough fiber. SE has shown to be accurate in predicting the airwater interface stability (see e.g., [25][26][27][28]). In this section, we first present the equations for producing a fiber having an arbitrary 3-D roughness, and then derive an equation for the energy of a droplet deposited on such a fiber.…”

Contribution of Interfacial Bonding towards Geopolymers Properties in Geopolymers Reinforced Fibers: A Review

“…To the best of our knowledge, there has been no research on using mathematical functions to simulate or quantify fiber roughness. Although the shape and arrangement of the actual roughness are arbitrary, for the sake of simplicity, the sine roughness (the sine function is also used to describe the roughness on the plane) is used [54][55][56][57]. In each cross-section of the fibers, the rose function (sine curve in polar coordinates) can cause sinusoidal roughness [58].…”

Wetting of ferrofluids: Phenomena and control

“…The same method was later used to measure energy dissipation on micropillared surfaces and its dependency on solid fraction and field strength (Fig 6 b) [63*]. Droplet adhesion forces on fibers have also been characterized with ferrofluids by placing droplets on the fibers and bringing a permanent magnet incrementally closer until the droplet detaches [76]. The fibers were attached to a balance, which was used to measure the maximum magnetic force acting on the droplet before detachment.…”