Tunable hydrophobicity on fractal and micro-nanoscale hierarchical fracture surface of metallic glasses

Highlights: • Hierarchical fracture surfaces with tunable hydrophobicity were designed by bending. • Metallic glass fracture surfaces display wetting transition from near-superhydrophobic to near-superhydrophilic. • As-cast metallic glass fracture surface with double-fractal hierarchical dimple structures exhibits near-superhydrophobic property. • Contact angle shows a correlation with fractal dimension of fracture surfaces. A series of fractal, hierarchical fracture surfaces with a tunable hydrophobicity were designed and fabricated by simply three-point bending of metallic glasses (MGs) with different annealing treatments. We microscopically analyzed the structures of the fracture morphology on various fracture surfaces by scanning electron microscope and atomic force microscope, and find that the tunable hydrophobicity originates from the intrinsic micro-nanoscale hierarchical, two-level fractal fracture micro-structures in MGs. Our results may provide a strategy to fabricate the tunable wetting surface with combination of the excellent mechanical properties in MGs.