Coating “nano-armor” for robust superwetting micro/nanostructure

Recently, enhancing the stability of surface microstructure becomes a research focus due to its significant effect on various interfacial properties, such as the wettability. A new strategy that can improve the stability of existing microstructure without changing its morphology is desirable since it can keep original surface functions that are dependent on the microstructure, but it is still a challenge. Herein, we report such a strategy through dip coating and heat treatment of a layer of rigid aluminum dihydrogen phosphate (ADP) on the existing fragile copper micro/nanostructure. SEM results and the mechanical wear tests including sand abrasion and tape peeling test results demonstrate that the ADP coating can act as a layer of “nano-armor” to protect the inner microstructure without changing its morphology, as a result, the stability of both surface microstructure and corresponding underwater superoleophobicity are improved remarkably. Specifically, the hardness of microstructure is improved by a factor about 10. Theoretical simulations analysis reveals that the enhanced effect results from the nanocoating, which decreases the maximum transverse deformation and stress on the microstructure. Finally, the method was also applied on some other surfaces with particular functions including anisotropic wettings and oil/water separating properties, further confirming the universality for strengthening the microstructure-dependent surface functions. This work advances a strategy through strengthening existing surface microstructure to obtain stable superwetting performance, which starts fresh ideas for the design of robust functional interfacial materials.