Effects of frost formation on the ice adhesion of micro-nano structure metal surface by femtosecond laser.

In this work, we study the effect and evolution of frost condensation on the ice adhered micro-nano structured Ni metal surface. By measuring the ice adhesion strength to the porous-structured surface under different frosting coverage, it is found that the ice adhesion on the surface changes not only with the morphology but also with the different evolution stages of the frosting coverage. Combining the changes in surface morphology and low-temperature wettability, the reasons for the changes in the ice adhesion strength are attributed to the change of wettability of the porous-structured surface under different frosting coverage, which affects the infiltration state of the surface and results in different mechanical interlocking, air-pockets and cracks states at the ice-solid interface. Moreover, it is found that the ice adhesion strength of the hydrophobic and hydrophilic porous-structured surface tends to be the same when the surface is heavily frosted. In addition, we demonstrate that both the hydrophobic and hydrophilic columnar-structured surfaces have smaller ice adhesion strength than the original surface without any micro-nano structures regardless of whether the surface is frosted or not, and the measured lowest ice adhesion strength of the hydrophobic columnar-structured surface can be down to 30 kPa in all frosted evolution stages, which is less than one tenth of the original surface. The findings in this work suggest that the influence of frosting should be fully considered when designing the icephobic micro-nano structured metal structure, and it can further serve as an important guidance for the design of passive icephobic surfaces expected to be free from the frosting effect.