Transparent Photothermal Metasurfaces Amplifying Superhydrophobicity by Absorbing Sunlight

Abstract

Imparting and maintaining surface superhydrophobicity is receiving significant research attention over the last several years, driven by a broad range of important applications and enabled by advancements in materials and surface nanoengineering. Researchers have investigated the effect of temperature on droplet-surface interactions, which poses additional challenges when liquid nucleation manifests itself, due to ensuing condensation into the surface texture that compromises its anti-wetting behavior. Maintaining surface transparency at the same time poses an additional and significant challenge. Often, the solutions proposed are limited by working temperatures or are detrimental to visibility through the surface. Here we introduce a scalable method employing plasmonic photothermal metasurface composites, able to harvest sunlight and naturally heat the surface, sustaining water repellency and transparency under challenging environmental conditions where condensation and fogging would otherwise be strongly promoted. We demonstrate that these surfaces, when illuminated by sunlight, can prevent impalement of impacting water droplets, even when the droplet to surface temperature difference is 50°C, by suppressing condensate formation within the texture, maintaining transparency. We also show how the same transparent metasurface coating could be combined and work collaboratively with hierarchical micro-and nanorough textures, resulting in simultaneous superior pressure-driven impalement resistance and avoidance of water nucleation and related possible frosting in supercooled conditions. Our work can find a host of applications as a sustainable solution against impacting water on surfaces such as windows, eyewear, and optical components.

Electro‐/Photo‐Thermal Promoted Anti‐Icing Materials: A New Strategy Combined with Passive Anti‐Icing and Active De‐Icing

“…When SHSs are introduced to combine with active photo‐thermal techniques, ice can be rapidly melted to water under sunlight irradiation and then easily move away because of excellent water repellency. [ 65 ] For example, Zheng et al. designed magnetic responsive and flexible photo‐thermal promoted AIM, which can maintain both superhydrophobic and anti‐icing performances after 320 cycles sandpaper abrasion, 3 h water flow impact, and cyclic anti‐icing/de‐icing, respectively.…”

“…[9] Recently, many researchers have paid attention back to active de-icing techniques (i.e., electro-thermal and photo-thermal stimulus). [12,32,65,66] By the combination of passive AIM and active de-icing, new rationally designed AIM show efficient (i.e., <5 min), reliable (i.e., for safety) and energy saving (i.e., for cost) properties. Although there are many review papers on passive AIM, [9,14,36,37,67] reviews particularly focusing on electro-/photo-thermal promoted AIM (i.e., a new strategy combined with passive anti-icing and active de-icing) is still lacking.…”

“…When SHSs are introduced to combine with active photothermal techniques, ice can be rapidly melted to water under sunlight irradiation and then easily move away because of excellent water repellency. [65] For example, Zheng et al designed magnetic responsive and flexible photo-thermal promoted AIM, which can maintain both superhydrophobic and anti-icing performances after 320 cycles sandpaper abrasion, 3 h water flow impact, and cyclic anti-icing/de-icing, respectively. [106] They found that the photo-thermal de-icing time on three different surfaces (i.e., Fe powder (PFe), PDMS/candle soot (PCS) and PFe-PCS) is 200, 138, and 74 s, respectively (Figure 8a1-a3), and the superhydrophobic surface of PFe-PCS with double-layer structures slows down the heat transfer and thus reduce the heat loss downward.…”

Robust, Multiresponsive, Superhydrophobic, and Oleophobic Nanocomposites via a Highly Efficient Multifluorination Strategy

“…Artificial superhydrophobic surfaces, inspired by several evolutionarily adaptive surfaces in nature such as lotus leaves, water-strider legs, and so on, generally show extreme water repellency with a water contact angle (CA) exceeding 150° and are achieved by a low-surface-energy chemical matrix and micro/nanohierarchical surface texture. , Superhydrophobic materials have attracted extensive attention in addressing real-world issues including waterproofing, anti-icing, self-cleaning, drag reduction, and energy harvesting. , Nevertheless, the inferior oil repellency, poor mechanochemical properties, and lack of multifunctionality still greatly restrict the development of such materials …”

“…3,4 Superhydrophobic materials have attracted extensive attention in addressing realworld issues including waterproofing, 5 anti-icing, 6 self-cleaning, 7 drag reduction, 8 and energy harvesting. 9,10 Nevertheless, the inferior oil repellency, poor mechanochemical properties, and lack of multifunctionality still greatly restrict the development of such materials. 11 In general, long alkyl compounds (such as various wax 12,13 and polyolefin dispersions 14,15 ), organosilicon, 16,17 and longchain perfluorinated compounds (PFCs) 18 are widely used to obtain matrixes with sufficient hydrophobicity.…”