# A Review on Ultrafast Laser Enabled Excellent Superhydrophobic Anti-Icing Performances
## 4 Advances and Challenges of ULSASs
### Passive Superhydrophobic Anti-Icing Surfaces
#### 4.1.3. Durable Icephobicity  
Icephobic durability directly determines the lifespan of ULSASs in practical applications. Based on the discussion in Section 3.2.2, to enhance the icephobic durability, both the micro-nanostructure durability and the coating durability need to be enhanced. On SHSs, microstructures work as the robust skeleton while nanostructures endow surfaces with better superhydrophobicity [155]. Although the closed microstructures could  
Figure 14: Low ice adhesion on the ULSASs. (**a**) Images of the ice easy-removal of ULSAS with vibration. Ice was formed and accumulated in the icing wind tunnel condition (reproduced with permission from [154]. Copyright (2021) MDPI). (**b**) Low ice adhesion of ULSASs for different liquids (reproduced with permission from [78]. Copyright (2022) Springer). greatly enhance the room-temperature superhydrophobic durability, the open microstructures exhibit higher icephobic durability at low temperatures [118]. Hence, maintaining the open structures and further introducing more durable nanostructures become a good strategy for improving the micro-nanostructure durability. [PERSON] et al. utilized ultrafast laser ablation and chemical oxidation to fabricate the micro-nano-nanowire triple-scale structures, where the Cu(OH)\({}_{2}\) nanowires with an average length of 6-8 um and a width of 50 nm in situ grew on the microcones (Figure 15a). After continuous deicing tests, it was found that the surface icephobicity was progressively enhanced with an increase in deicing cycles, showing a unique property that the surfaces could become more and more icephobic after wear. The phenomenon was mainly ascribed to the side nanowires and the flat microcones constructing the moderate top roughness after the top nanowires were damaged, which decreased the ice-solid contact area and further led to the lower ice adhesion strengths. The lowest ice adhesion strength on the prepared surfaces reached 12.2 kPa and could maintain 17.3 kPa even after 60 deicing cycles. To date, it is the lowest ice adhesion strength after so many deicing cycles among all reported ULSASs [156]. Figure 15: Enhanced icephobic durability. (**a**) Enhanced micro-nanostructure durability by fabricating the micro-nano-nanowire triple-scale structures (reproduced with permission from [156]. Copyright (2022) American Chemical Society). (**b**) Enhanced low-surface-energy coating durability by using the method of PDMS spin coating (reproduced with permission from [82]. Copyright (2022) Elsevier). To provide more durable low-surface-energy coatings, many durable coating materials have been developed and tested [157; 158; 159]. Among these, PDMS materials show great application potential owing to strong bonding strength and an easy preparation process. Many durable superhydrophobic surfaces have been fabricated by the PDMS spin coating method instead of the vapor deposition of fluorosilanes [157; 160; 161]. Based on these properties, [PERSON] et al. fabricated a cauliflower-like micro-nanostructure combined with PDMS coatings by taking advantage of ultrafast laser ablation and wet chemical reactions [82]. As shown in Figure 15b, the prepared surfaces exhibited excellent superhydrophobicity and highly effective photothermal properties. Adopting FIB and EDS techniques to analyze the cross-sectional elements, it was found that the PDMS solutions could cover and bond the cauliflower-like structures well, forming an integrated structure. The infiltrated depth of PDMS in micro-nanostructures could reach the \(\upmu\)m-scale, which meant that the low-surface-energy coating could still be preserved to maintain the qualified superhydrophobicity after structure damage. With the robust coatings and abundant micro-nanostructures, surface icephobicity could be well maintained after 25 abrasion cycles or 1.5-hour water impact or 500 tape peeling cycles. Overall, the improvement of micro-nanostructures and low-surface-energy coatings contributes well to the enhancement of icephobic durability.