Temperature-dependent wetting characteristics of micro–nano-structured metal surface formed by femtosecond laser

Abstract

The hydrophilicity induced by micro–nano-structured surface has aroused great attention for promising applications. In this work, the temperature-dependent surface wettability with different micro–nano-structures prepared by femtosecond lasers is studied systematically. It is found that the contact angle of both the micro- and nano-structural hydrophilic surfaces reduces as the ambient temperature decreases from 60 to 20 °C, but the contact angles of the typical microscale surfaces increase when the surface temperature reduces from 20 to 5 °C when the surface temperature is lower than ambient temperature. Furthermore, it is found that some microscale structural samples show a much weaker temperature dependence than others, which is experimentally proved to be due to the strong capillary effects in those specific microscale structures. By contrast, hydrophobic micro–nano-structural samples with the same structure obtained by silanization process always show that the hydrophobicity of both nano- and micro-structured surfaces decreases when temperature decreases from 20 to 5 °C. To the best of our knowledge, we are the first to report the temperature-dependent wettability of hydrophilic micro–nano-structured surfaces with surface temperature below ambient temperature. The findings in this work can be applied to the micro- and nanoscale structural surface formed by other methods, and it will be beneficial to the engineering design and manufacture of micro–nano-structured surfaces to achieve the desired performance of the wetting function, which is of great significance to the application of hydrophilic micro–nano-structured surfaces in varied temperature surroundings.