Icephobic micro-nano engineering surfaces in extreme environments

Abstract

Engineering icephobic surfaces has been a long-standing effort to address the challenges of ice prevention and removal in our daily life and industrial applications. To prevent or delay icing, there have been extensive anti-icing strategies via surface modifications, including superhydrophobic surfaces, slippery surfaces, antifreeze materials, and polyelectrolyte brush coatings. Even though these passive anti-icing methods are highly innovative and desirable, they are unable to inhibit ice formation and propagation under humid conditions or during repeated operations. Superhydrophobic surfaces and photothermal effect have shown their distinct merits in antiicing and deicing. It is highly desirable to exploit their mutual benefits to realize passive, durable, and sustainable icephobicity even at extremely low temperatures. We presented a superhydrophobic selective surface constructed with a hierarchical architecture to enable stable superhydrophobicity and high-efficiency solar-thermal conversion. The surface spectral selectivity is deliberately designed to maximize solar harvesting while minimizing thermal reradiation loss. The boosted solar-thermal conversion empowers remarkable anti-icing of a sessile droplet at a record-low temperature of -60 °C under 1-sun illumination. The synergy of solar-thermal conversion and superhydrophobicity endows the surface with superior and durable icephobicity. Further, for the versatility and compatibility of superhydrophobic solar-thermal coating, we developed a large-area solar-thermal icephobic nanocoating that is compatible with both flat and complex curved surfaces. The basic ingredients of the nanocoating are titanium nitride nanoparticles and dual-sized silica nanoparticles, serving as a low-emissivity photo-thermal medium and a water-repellent layer, respectively. Enabled by the seamless cooperation between a record-high solar-thermal performance (1-sun temperature rise, 72 °C) and a large contact angle of 173°, the nanocoating realizes complete and rapid deicing/defrosting on power lines at a frigid temperature of −15 °C. This design of the superhydrophobic solar-thermal coating brings passive solar-driven deicing technologies closer to practical applications. Finally, achieving robust all-day anti-frosting solely through interfacial modification and solar-thermal effects is complex and challenging in practical applications due to insufficient sunlight after dark and the high reflectance of frost. We present a V-groove superhydrophobic solar-thermal surface that can harvest 98% of sunlight and convert it into heat while still maintaining superior water repellency for all-day passive anti-frosting and defrosting. Remarkably, the surface shows exceptional anti-frosting capability in practical scenarios for 25 hours and defrosting at frigid temperatures. This passive all-day anti-frosting and defrosting surface with scalability and durability is promising for long-term practical applications in extreme environments.

Date of Award	2024
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Shuhuai YAO (Supervisor)