Laser-driven, precision manufacturing of hierarchical structure surfaces enables tunable superhydrophobic/hydrophilic properties

This study demonstrates a laser-driven precision manufacturing approach for tunable wettability surfaces by direct conversion of polyimide films into laser-induced graphene (LIG) with hierarchical microstructures. By precisely controlling Ytterbium fiber laser parameters, the reversible transition between superhydrophilic (contact angle ≈ 15°) and superhydrophobic (contact angle ≈ 155°, hysteresis < 5°) states is achieved. Comprehensive characterizations reveal that the non-monotonic wettability transition results from the synergistic evolution of carbonization degree, surface chemistry, and hierarchical roughness. The grid-like LIG structures fabricated at 70 W power exhibited optimal superhydrophobicity due to their unique combination of high sp² carbon content, minimal oxygen content, moderate surface roughness (Sa = 15.27 μm), high fractal dimension (Df = 2.35), and optimal feature aspect ratio (1:4.2). The process exhibited excellent reproducibility (contact angle standard deviation <±2° across 10 samples) and environmental stability (contact angle remained >150° after 30 days of ambient exposure). This approach enables rapid, mask-free fabrication of functional surfaces with tunable wettability for applications in anti-icing, liquid transport, and microfluidic devices.