When Lubricant Retention Increases Ice Adhesion: Ionic Liquids in SLIPS

Slippery liquid-infused porous surfaces (SLIPS) can reduce ice adhesion, but their durability depends on coupled wetting, rheological, and phase-transition effects. Here, seven imidazolium ionic liquids (ILs) with varied alkyl and disiloxane substituents were evaluated as lubricants for laser-textured superhydrophobic aluminum. Surface tension, viscosity, thermal behavior, lubricant retention, wetting, and ice adhesion at -10 °C were correlated over 30 icing-deicing cycles. All freshly prepared coatings were water-wettable but exhibited weak droplet pinning, with sliding angles of 1.4-7.5°, despite apparent water contact angles below 90°. This combination reflects the lubricant-mediated interface, for which droplet mobility is not determined by the static contact angle alone. The behavior of SLIPS with different lubricants diverged under centrifugal loading: low-viscosity ILs were depleted, whereas ILs that solidified under the applied cooling protocol were retained more effectively within the texture. Counterintuitively, greater lubricant retention produced higher ice adhesion because solidified ILs stabilized ice bridges within the surface relief. The lowest adhesion after cycling was obtained for the coating infused with [C₉C₃Si₂Oim][NTf₂], which after lubricant depletion restored a superhydrophobic state with a water static contact angle of 171.6 ± 1.6°. These results identify lubricant phase state and interfacial redistribution as key design parameters for durable anti-icing SLIPS.