Study on micro-nano structures’ wettability transformation mechanism of femtosecond laser on aluminium alloy

Abstract

In this work, superhydrophilic surfaces are obtained on LY12 aluminium alloy by irradiation of femtosecond (Fs). First, based on the theory of laser induced surface plasmon polariton, the formation mechanism of micro-nano structures is analyzed. Then the periodic change of the micro-nano structures with different wavelength and incident angle is calculated. According to the theoretical results, the structure period is 600 nm at the vertical incident and incident wavelength with 800 nm, and the experimental results agree with the theoretical results. Furthermore, two different kinds of postprocessing methods are employed to change the superhydrophilic surfaces to superhydrophobic surfaces. All the micro-nano structures are tested by scanning electron microscope (SEM), contact angle (CA) and Fourier transform infrared spectra (FTIR). By analyzing the function of the functional groups of C–H, C–F and C–O, the transition mechanism of the surface from superhydrophilicity to superhydrophobicity is also explored.