Gradient droplet distribution promotes spontaneous formation of frost-free zone

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

The inhibition of condensation frosting at harsh environments is critical in various anti-icing applications. However, frosting on the entire surface is the final fate for most passive anti-icing strategies as a result of inevitable ice nucleation of subcooled droplets from the surface edges or defects and the following inter-droplet freezing wave propagation. Here, we report the frost-free zone formation on a macro-ridged surface. We design a macroscale ridge on the surface and show that this surface configuration changes the spatial distribution of water vapor diffusion flux during the condensation stage, resulting in a gradient arrangement of condensate droplets according to their size. This allows numerous failures of local inter-droplet ice bridging in the area with a critical droplet coverage rate, which triggers the interruption of the global freezing wave propagation and the evaporation of the rest droplets to form a frost-free zone around the ridge corner. These findings extend our understanding of frost formation on the surface and provide a rationale for the surface design with impressive durable anti-frosting performance.

Related collections

Most cited references 39

Record: found
Abstract: found
Article: not found

Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity.

Ka-tak T Wong, Alison Grinthal, Sing Wong … (2011)

Creating a robust synthetic surface that repels various liquids would have broad technological implications for areas ranging from biomedical devices and fuel transport to architecture but has proved extremely challenging. Inspirations from natural nonwetting structures, particularly the leaves of the lotus, have led to the development of liquid-repellent microtextured surfaces that rely on the formation of a stable air-liquid interface. Despite over a decade of intense research, these surfaces are, however, still plagued with problems that restrict their practical applications: limited oleophobicity with high contact angle hysteresis, failure under pressure and upon physical damage, inability to self-heal and high production cost. To address these challenges, here we report a strategy to create self-healing, slippery liquid-infused porous surface(s) (SLIPS) with exceptional liquid- and ice-repellency, pressure stability and enhanced optical transparency. Our approach-inspired by Nepenthes pitcher plants-is conceptually different from the lotus effect, because we use nano/microstructured substrates to lock in place the infused lubricating fluid. We define the requirements for which the lubricant forms a stable, defect-free and inert 'slippery' interface. This surface outperforms its natural counterparts and state-of-the-art synthetic liquid-repellent surfaces in its capability to repel various simple and complex liquids (water, hydrocarbons, crude oil and blood), maintain low contact angle hysteresis (<2.5°), quickly restore liquid-repellency after physical damage (within 0.1-1 s), resist ice adhesion, and function at high pressures (up to about 680 atm). We show that these properties are insensitive to the precise geometry of the underlying substrate, making our approach applicable to various inexpensive, low-surface-energy structured materials (such as porous Teflon membrane). We envision that these slippery surfaces will be useful in fluid handling and transportation, optical sensing, medicine, and as self-cleaning and anti-fouling materials operating in extreme environments. © 2011 Macmillan Publishers Limited. All rights reserved

0 comments Cited 544 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

Liquid-infused nanostructured surfaces with extreme anti-ice and anti-frost performance.

Philseok Kim, Tak-Sing Wong, Jack Alvarenga … (2012)

Ice-repellent coatings can have significant impact on global energy savings and improving safety in many infrastructures, transportation, and cooling systems. Recent efforts for developing ice-phobic surfaces have been mostly devoted to utilizing lotus-leaf-inspired superhydrophobic surfaces, yet these surfaces fail in high-humidity conditions due to water condensation and frost formation and even lead to increased ice adhesion due to a large surface area. We report a radically different type of ice-repellent material based on slippery, liquid-infused porous surfaces (SLIPS), where a stable, ultrasmooth, low-hysteresis lubricant overlayer is maintained by infusing a water-immiscible liquid into a nanostructured surface chemically functionalized to have a high affinity to the infiltrated liquid and lock it in place. We develop a direct fabrication method of SLIPS on industrially relevant metals, particularly aluminum, one of the most widely used lightweight structural materials. We demonstrate that SLIPS-coated Al surfaces not only suppress ice/frost accretion by effectively removing condensed moisture but also exhibit at least an order of magnitude lower ice adhesion than state-of-the-art materials. On the basis of a theoretical analysis followed by extensive icing/deicing experiments, we discuss special advantages of SLIPS as ice-repellent surfaces: highly reduced sliding droplet sizes resulting from the extremely low contact angle hysteresis. We show that our surfaces remain essentially frost-free in which any conventional materials accumulate ice. These results indicate that SLIPS is a promising candidate for developing robust anti-icing materials for broad applications, such as refrigeration, aviation, roofs, wires, outdoor signs, railings, and wind turbines.