**4. Conclusions**

We reported the fabrication of SLIPS based on a nanostructured, porous alumina coating infused with low surface tension lubricants with different chemical composition (PFPE, n-hexadecane) and viscosity (from 2.8 to 450 mm2/s). Wetting characterization of as-produced SLIPS showed that contact angle hysteresis with water and hexadecane drops increased with the viscosity of the infused liquid. However, higher viscosity led to enhanced resistance to almost all of the tested severe environmental conditions: nhexadecane and the least viscous PFPE (Krytox 100) proved unstable in acidic, alkaline, and saline environments, leading to complete loss of repellence in few days. On the other hand, SLIPS infused with the most viscous PFPE oil (Krytox 107) retained their amphiphobic behavior for up to 60 days, especially in acidic and highly saline solutions. These results lead to consider these surfaces as potential candidates for application in the naval and maritime industries. The same trend was observed in abrasion tests: the high mobility of short polymer chains in the low-viscosity Krytox 100 made them susceptible to tribochemical degradation, which in turn did not affect the repellence of highly viscous Krytox 107. Even the chemical composition of the infused liquid affected SLIPS durability under abrasion: despite its very low viscosity, hexadecane proved stable in such conditions

due to the non-cleavable C-C bonds forming its chain. These considerations are extremely relevant for the application of SLIPS in devices like hard drives or lubricated joints for mechanics. On the other hand, hexadecane-infused SLIPS proved the least stable in UV irradiation tests due to the high volatility of the infused lubricant, which makes these coatings unsuitable for applications in which the surface is expected to be exposed to air (i.e., not being wetted by another liquid or in an open ambient). These results once again highlight the need for careful consideration of the application conditions when designing a liquid-infused coating.

**Author Contributions:** Conceptualization, F.V. and M.R.; methodology, F.V. and M.R.; software, F.V.; validation, F.V. and A.C.; formal analysis, F.V.; investigation, G.G.; resources, F.V. and M.R.; data curation, F.V. and G.G.; writing—original draft preparation, F.V.; writing—review and editing, F.V., A.C., and M.R.; visualization, F.V. and A.C.; supervision, F.V. and M.R.; project administration, F.V. and M.R.; funding acquisition, M.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data available in a publicly accessible repository. The data presented in this study are openly available in https://doi.org/10.6084/m9.figshare.16566960.v1, accessed on 6 September 2021.

**Acknowledgments:** The authors want to acknowledge the entire Smart Surfaces Group at CNR-ISTEC for their precious work.

**Conflicts of Interest:** The authors declare no conflict of interest.

### **References**

