Fig. 1. Process schematic of the highly efficient laser-based micro/nanostructuring superhydrophobic surface. (a) Laser surface treatment; (b) scanning trajectory; (c) chemical immersion treatment

Fig. 2. 3D surface profiles. (a) Untreated surface; (b) laser micro/nanostructured surface

Fig. 3. SEM micrographs of surface structures fabricated by the existing ultra-fast laser-based surface texturing methods. (a) LIPSS structure fabricated by Cunha et al.^[39]; (b) hierarchical structures fabricated by Martínez-Calderon et al.^[40]; (c)(d) untreated surface; (e)(f) laser micro/nanostructured surface fabricated by the proposed method using the power intensity of 0.6 GW/cm²; (g)(h) laser micro/nanostructured surface fabricated by the proposed method using the power intensity of 8.4 GW/cm²

Fig. 4. XPS survey spectra analysis. (a) Untreated surface; (b) laser micro/nanostructured surface, the inset shows the core elemental spectrum of C element on laser micro/nanostructured surface

Fig. 5. Contact angle and roll-off angle measurement results for laser micro/nanostructured material with different laser power intensities. (a) AISI4130 low alloy steel; (b) AA6061 aluminium alloy

Fig. 6. Microhardness measurement results of laser micro/nanostructured AISI4130 low alloy steel and AA6061 aluminium alloy treated by different laser power intensities

Fig. 7. Corrosion resistance of the laser micro/nanostructured surface. (a) Comparison of the polarization curves for the untreated surface and laser micro/nanostructured surface; (b) surface structures and contact angles for the laser micro/nanostructured surface before and after the electrochemical test

Fig. 8. Deliquescence of NaCl on horizontal untreated surface and laser micro/nanostructured surface with relative humidity of 90%. (a)--(c) Untreated surface; (d)--(f) laser micro/nanostructured surface

Fig. 9. Deliquescence of NaCl on laser micro/nanostructured surface inclined at an angle of ~20° with relative humidity of 90%

Fig. 10. Comparison of the processing efficiency between proposed method and traditional laser processing methods

Table 1. Main chemical compositions of AISI4130 low alloy steel and AA6061 aluminum alloy

Table 2. E_corr, I_corr and corrosion rate of the untreated surface and laser micro/nanostructured surface