Evaporative Crystallization in Drops on Superhydrophobic and Liquid-Impregnated Surfaces

Abstract

Mineral-fouling induced corrosion and deterioration of marine vessels, aircraft, and coastal structures is due in part from structural intrusion of crystals grown from ocean-generated saline drops. As such, much work has explored surface treatments that induce hydrophobicity or introduce barriers for antifouling and corrosion prevention; however, the efficacy of these strategies will be altered by the underlying substrate texture. Here, we study the behavior of evaporating saline drops on superhydrophobic and liquid-impregnated surfaces as a function of surface texture. On superhydrophobic surfaces, four disparate regimes (which are not observed for particle-laden drops) emerge as a function of the substrate solid fraction: Cassie-pinning, Cassie-gliding, Cassie-Wenzel transition, and Wenzel. These regimes control the morphology of the resultant crystal deposits. In contrast to the superhydrophobic surfaces, spreading liquid-impregnated surfaces demonstrate minimal influence of solid fraction on evaporative crystallization. The area, area localization, timescale of evaporation, and deposit morphology are all normalized by the presence of the lubricating layer, thus introducing an efficient method of eliminating crystal "coffee rings" as well as reducing the potential for fouling and corrosion.

Crystal critters: Self-ejection of crystals from heated, superhydrophobic surfaces

“…The texture was then hydrophobized by vapor deposition of a fluorosilane chemistry [trichloro (1 H ,1 H ,2 H ,2 H -perfluorooctyl)] over a period of 6 hours. Preparation of other textures has been described previously ( 36 ).…”

Interfacial Crystallization within Liquid Marbles

“…When naked saline droplets are evaporated on superhydrophobic surfaces, very different scenarios of evaporation are possible, namely the evaporation may take place under the pinned triple line, and under the sliding triple line as discussed in Ref. 36. The evaporation may be accompanied by the Cassie-Wenzel wetting transition and may take place within the Cassie wetting regime [36][37].…”

“…36. The evaporation may be accompanied by the Cassie-Wenzel wetting transition and may take place within the Cassie wetting regime [36][37]. We studied evaporation of the naked saline droplets under ambient conditions (t=25°C) and also under the constant temperature of the substrate of t=70°C.…”

Coupled thermal transport and mass diffusion during vapor absorption into hygroscopic liquid desiccant droplets

“…Results demonstrate the dependence of contact line dynamics and crystalline morphology on salt concentration and surface wettability. Other influencing factors on the evaporation behavior and on the crystal patterns formed from the dry-out of saline droplets have been presented by McBride [24], Shahidzadeh-Bonn [25], Kaya [26], Harrington et al [27]. The reader is also referred to the review papers of Sefiane and Parsa et al [28,29].…”