# A Review on Ultrafast Laser Enabled Excellent Superhydrophobic Anti-Icing Performances
## 5 Conclusions  
Ultrafast lasers, as powerful and promising manufacturing tools, have colossal value in accelerating the development and applications of superhydrophobic anti-icing surfaces. To eliminate the undesired ice, much attention has been paid to ultrafast laser-fabricated superhydrophobic anti-icing surfaces (ULSASs), and related research has been comprehensively conducted in recent years. Here, we summarized the recent development of ULSASs, mainly including three aspects: fabricating, mechanisms, and advances and challenges. With respect to fabricating, we introduced fundamental wettability. Combining exquisite micro-nanostructures and low-surface-energy matters, biomimetic superhydrophobicity can be endowed on various substrate materials. Next, the advantages and mechanisms of ultrafast laser micro-nano fabricating were explained. Compared to other micro-nano fabricating strategies, the ultrafast laser-fabricating method possesses the significant advantages of being highly programmable, having the nm-accuracy, being contact-free, and with non-limitation for materials. Based on the light-matter interaction, many unique micro-nanostructures have been widely developed, providing more opportunities and possibilities for exploring the superhydrophobic anti-icing mechanisms and applications. In mechanisms, we introduced some recent discoveries and thus extended understanding of anti-icing on the laser-fabricated micro-nanostructures, and further elucidated the relationship between superhydrophobicity and icephobicity that superhydrophobicity is one necessary but not insufficient condition of icephobicity. Meanwhile, three common failure mechanisms of ULSASs were analyzed, including Cassie-Baxter stability, surface durability, and environmental adaptivity. Essentially, structures and coatings were two crucial factors to avoid the failure of ULSASs. In advances and challenges, we summarized the recent progress and the respective challenges of ULSASs in passive anti-icing, passive/active combined anti-icing, and some practical outdoor applications. The passive anti-icing of ULSASs mainly lies in delaying icing time, decreasing ice adhesion strengths, and achieving durable anti-icing, while the passive/active combined anti-icing technologies were introduced with the electrothermal- or photothermal-assisted methods. However, in contrast to lab-scale freezing environments, the practical application environments were more complicated and volatile, which brings tremendous challenges for the performances of ULSASs (icephobicity, durability, stability, etc.) and their engineering feasibility (large-scale fabrication, surface installation, device matching, etc.). As for the future development of ULSASs, the following opportunities are envisioned:
* Further investigations and deepened understanding of icing-related phenomena on superhydrophobic surfaces need to be explored. * More design and optimization of structures and chemical coatings are demanded for developing more durable ULSASs. * More novel ultrafast laser-fabrication technologies and more advanced ultrafast laser instruments are expected to meet the strictly industrial application requirements. Writing--original draft preparation, L.W. ; writing--review and editing, H.Z. ([PERSON]), D.Z., L.Y. and H.Z. ([PERSON]); supervision, P.F. and M.Z. All authors have read and agreed to the published version of the manuscript. We acknowledge funding support from the National Key R&D Program of China (Grant No. 2017 YFB1104300 and 2022 YFE0203700, M.Z. ), the Tsinghua University Initiative Scientific Research Program (Grant No. 2018Z05 JZY009, M.Z. ), and the National Natural Science Foundation of China (Grant Nos. 51575309 and 51210009, M.Z.). Not applicable. Data Availability Statement: Data is contained within the article.