Long-Term Durability of Lubricant-Infused Surfaces under Ambient Condensation

Lubricant-infused surfaces (LISs) have emerged as promising solutions to enhance the efficiency of water condensation. However, LISs are confronted with substantial challenges, particularly the condensation-induced shift from a slippery hydrophobic surface to a pinning hydrophilic surface, which dramatically decreases the droplet mobility. In this study, we experimentally investigate the durability of LISs for various structured surface designs and lubricants under ambient condensation conditions. Our study focuses on two silicone oils and two perfluoropolyether (PFPE) oils applied to three types of substrates, all conformally coated with the same hydrophobic material. Our research reveals that the lifespan of LISs varies based on the substrate surface morphology, the viscosity of the infused lubricant, and the lubricant–substrate compatibility. The results show that LISs incorporating low-viscosity lubricants and substrates with nanoscale features are susceptible to rapid deterioration, leading to an unwanted shift to filmwise condensation. The use of a low-viscosity lubricant results in a higher oil removal rate during droplet shedding and cloaking, while the use of a surface structure having a low lubricant retention volume ensures a more rapid depletion and transition to the non-LIS wetting state. LISs infused with high-viscosity lubricants, notably Krytox-16256 with low drainage rates, and those fabricated to have hierarchically structured etched aluminum substrates with high volumes of porosity and lubricant holdup capability maintain dropwise condensation for over 500 days. This study not only sheds light on the durability and performance of LISs in scenarios involving atmospheric water condensation but also provides essential guidelines for designing robust and long-lasting LISs.