On the mechanism of droplet rolling and spinning in inclined hydrophobic plates in wedge with different wetting states

Abstract

A water droplet rolling and spinning in an inclined hydrophobic wedge with different wetting states of wedge plates is examined pertinent to self-cleaning applications. The droplet motion in the hydrophobic wedge is simulated in 3D space incorporating the experimental data. A high-speed recording system is used to store the motion of droplets in 3D space and a tracker program is utilized to quantify the recorded data in terms of droplet translational, rotational, spinning, and slipping velocities. The predictions of flow velocity in the droplet fluid are compared with those of experimental results. The findings revealed that velocity predictions agree with those of the experimental results. Tangential momentum generated, via droplet adhesion along the three-phase contact line on the hydrophobic plate surfaces, creates the spinning motion on the rolling droplet in the wedge. The flow field generated in the droplet fluid is considerably influenced by the shear rate created at the interface between the droplet fluid and hydrophobic plate surfaces. Besides, droplet wobbling under the influence of gravity contributes to the flow inside the rolling and spinning droplet. The parallel-sided droplet path is resulted for droplet emerging from the wedge over the dusty surface.

Asphaltene-Derived Graphene Quantum Dots for Controllable Coatings on Glass, Fabrics, and Aerogels

“…Thus, these asphaltene-derived nanoparticles can be concentrated by using a straightforward solvent extraction method to obtain nanomaterials with the desired interfacial properties. Surprisingly, the sliding angle was not significantly improved (i.e., lowered) with any of the GQD coatings, suggesting that other factors such as the interfacial resistance may play a more dominant role on the inclined glass surfaces …”

“…Surprisingly, the sliding angle was not significantly improved (i.e., lowered) with any of the GQD coatings, suggesting that other factors such as the interfacial resistance may play a more dominant role on the inclined glass surfaces. 36 Figure 1 shows how type-AC GQDs can be converted to type-OM GQDs by oxidation (see the Experimental Section), at which point they become hydrophilic, similar to type-AM. Finally, type-OM materials were exposed to a strong reducing agent and then extracted into chloroform.…”