Hydrophilic Slippery Surface Promotes Efficient Defrosting

Abstract

Frost accretion occurs ubiquitously in various industrial applications and causes tremendous energy and economic loss, as manifested by the Texas power crisis that impacted millions of people over a vast area in 2021. To date, extensive efforts have been made on frost removal by microengineering surfaces with superhydrophobicity or lubricity. On such surfaces, air or oil cushions are introduced to suspend the frost layer and promote the rapid frost sliding off, which, although promising, faces the instability of the cushions under extreme frosting conditions. Most existing hydrophilic surfaces, characterized by large interfacial adhesion, have long been deemed unfavorable for frost shedding. Here, we demonstrated that a hydrophilic and slippery surface can achieve efficient defrosting. On such a surface, the hydrophilicity gave rise to a highly interconnected basal frost layer that boosted the substrate-to-frost heat transfer; then, the resulting melted frost readily slid off the surface due to the superb slipperiness. Notably, on our surface, the retained meltwater coverage after frost sliding off was only 2%. In comparison to two control surfaces, for example, surfaces lacking either hydrophilicity or slipperiness, the defrosting efficiency was 13 and 19 times higher and the energy consumption was 2.3 and 6.2 times lower, respectively. Our study highlights the use of a hydrophilic surface for the pronounced defrosting in a broad range of industrial applications.

Photothermal superhydrophobic copper nanowire assemblies: fabrication and deicing/defrosting applications

“…(c) Delay of frost melting and (d) durations required to complete the defrosting process after the surfaces have been frozen for 0.5, 1, and 1.5 h under one-sun illumination. (e) Comparison of defrosting efficiency among our work and previous works[28,32,[54][55][56][57][58][59][60], SHS is short for the superhydrophobic surface.…”

“…Such advantage was also evident under different sun illuminations (figure S8). Moreover, we also considered the defrosting efficiency, defined as the ratio of frost removal, and compared it with previous studies that employed different strategies such as hydrophilic, hydrophobic, superhydrophobic, slippery surfaces, and surfaces exhibited both photothermal and superhydrophobic properties [28,32,[54][55][56][57][58][59][60]. As shown in figure 6(e), while some of the surfaces used in previous studies exhibited a defrosting efficiency over 90%, nanowire surface demonstrated an impressively high defrosting efficiency approaching 100%, demonstrating the best defrosting efficiency among all the reported surfaces.…”

“…As shown in figure 6(e), while some of the surfaces used in previous studies exhibited a defrosting efficiency over 90%, nanowire surface demonstrated an impressively high defrosting efficiency approaching 100%, demonstrating the best defrosting efficiency among all the reported surfaces. [28,32,[54][55][56][57][58][59][60], SHS is short for the superhydrophobic surface.…”

“…hydrophilic surface) regarding de-icing and defrosting, due to the water-repellency property [24][25][26][27]. Despite promising and effective, the previous attempts are normally unable to spontaneously remove the attached ice or frost under cold environments unless there is sufficient heat input to enable the melting of ice/frost [28,29]. Recently, photothermal surfaces capable to be heated by sunlight, a green energy source abundant on the earth, have attracted significant attention [30][31][32].…”

Icephobic materials and strategies: From bio‐inspirations to smart systems

“…Once the liquid droplet is pinned to the exposed surface, the surface defects present a high hysteresis and immobilize the water droplet, which leads to an instant ice formation. 163 For SHSs, the tiny water droplets are prone to condensate at the surface defects. Slippery surface presents a better frost-/ice-free performance, where the hemispherical droplets that are formed by the coalescence of satellite droplets can sweep away the pinned droplets.…”