Micro-fabricated aluminium surfaces for reduced ice adhesion

Hypothesis: Topographic micro-structures can potentially encourage ice removal from a surface, by weakening the ice at the ice-surface interface. Random and periodic structures have both been investigated, however gradient-pitch structures, where the spacing between structures changes, have not been reported. Gradient pitch structures are anisotropic, creating a force imbalance which is expected to aid ice removal compared with flat surfaces and surfaces with isotropic structures. Applying force to the ice from different directions is also expected to affect the adhesion strength. Experiments: Topographic aluminium microlines, with gradient-pitch spacing, are tested for the first time for anti-icing properties, with fixed-pitch structures and smooth aluminium tested as a comparison. Both types of structures, fabricated by micro-milling, are characterised for their geometric and surface wetting properties (static contact angle, contact angle hysteresis and microwetting state) and tested for ice adhesion strength using the force probe technique. Findings: The gradient-pitch surfaces reduce the ice adhesion strength by about 50% compared with baseline control surfaces. The direction from which the force was applied was found to have an effect on the adhesion strength of the ice to the surface, with the lowest ice adhesion strength recorded when force was applied in the direction of the microlines.