Bio-Inspired Icephobic Coatings for Aircraft Icing Mitigation: A Critical Review

A critical review is provided to summarize our recent efforts to utilize the state-of-the-art bio-inspired icephobic coatings/surfaces, i.e., 1). Lotus-leaf-inspired superhydrophobic surfaces (SHS) and 2). Pitcher-plant-inspired slippery liquid-infused porous surfaces (SLIPS) for aircraft icing mitigation. By leveraging the unique Icing Research Tunnel of Iowa State University (i.e., ISU-IRT), an experimental campaign was performed to evaluate the effectiveness of using SHS and SLIPS coatings to suppress impact ice accretion over the surfaces of typical airfoil/wing models. While both SHS and SLIPS were found to be able to suppress ice accretion over the airframe surfaces where strong aerodynamic forces are exerted, ice was still found to accrete in the vicinity of the airfoil stagnation line where the aerodynamic forces are at their minimum. A novel hybrid anti-/de-icing strategy concept to combine icephobic coatings with minimized surface heating near airfoil leading edge was demonstrated to effectively remove impact ice accretion over entire airfoil/wing surfaces. An experimental investigation was also conducted to examine the durability of the icephobic coatings/surfaces to resist "rain erosion" effects (i.e., the damage to the surface coatings due to continuous impingement of water droplets at high speeds) in considering the practical usage for aircraft icing mitigation. The rain erosion effects were characterized based on the variations of the ice adhesion strengths and surface morphology of the eroded test surfaces coated with SHS and SLIPS. The research findings are very helpful to elucidate the underlying physics for the development of novel and robust anti-/de-icing strategies for aircraft icing mitigation.