Two modes of contact‐time reduction in the impact of particle‐coated droplets on superhydrophobic surfaces

Abstract

Reducing the contact time during droplet impact is essential for many scientific and industrial applications, such as self‐cleaning, anti‐icing, heat transfer, and condensation. This paper reports contact‐time reduction by coating droplets with micro–nano hydrophobic particles. Such particle‐coated droplets are known as liquid marbles (LM). LM impact on superhydrophobic surfaces reveals two different modes of contact‐time reduction. For lower impact energies, the reduced adhesion of LM with the surface is responsible for a reduction of up to 21%. Contact‐time reduction in this regime is found to be independent of particle size but dependent on the solid fraction of LM. However, a fragmentation‐based contact‐time reduction is observed for larger particle sizes and higher impact energies. Here, the reduction is as high as 65%. Such fragmentation occurs because the spreading LM lamella breaks when its thickness becomes similar to particle dimensions. Our findings reveal the potential of LM as a novel approach to reduce contact time during droplet impact, with implications for various scientific and industrial applications.

Melting Process of Frozen Sessile Droplets on Superhydrophobic Surfaces

“…Then, when the frozen droplet melts, the stored surface energy is released and converted to kinetic energy, which is used for the recovery of the droplet morphology. This phenomenon is helpful for gradually detaching the part of the droplet pinned in the micro/nanoscale structures of the substrate . , In addition, the gas dissolved in the droplet may form bubbles, which are bound in the ice cap during the freezing process. , According to a study done by Wang et al, these bubbles could continuously impact the substrate surface, thus providing a source for airbags that promote the detachment of the bottom of the droplet during melting. Therefore, the whole process restores the superhydrophobicity of the substrate.…”

“…This phenomenon is helpful for gradually detaching the part of the droplet pinned in the micro/nanoscale structures of the substrate . 27,28 In addition, the gas dissolved in the droplet may form bubbles, which are bound in the ice cap during the freezing process. 29,30 According to a study done by Wang et al, 31 these bubbles could continuously impact the substrate surface, thus providing a source for airbags that promote the detachment of the bottom of the droplet during melting.…”

Heat transfer during droplet impact on a cold superhydrophobic surface via interfacial thermal mapping

“…In general, it is believed that reduced contact area and contact time lead to limited heat transfer. For the purpose of possibly reducing the heat transfer, a variety of hydrophobic and structured surfaces have been developed 3,7–16 focusing on reducing the contact time and contact area. Shiri and Bird 2 reported a reduction in contact time using surface structures that redistribute the liquid mass asymmetrically and hence alter the drop hydrodynamics.…”