Laser-ablated PDMS/Copper Powder Superhydrophobic Copper Surfaces for Enhanced Condensation Heat Transfer
Conventional polydimethylsiloxane (PDMS) coatings for condensation heat transfer suffer from insufficient mechanical durability and high interfacial thermal resistance, limiting their industrial deployment. This study introduces a one-step, fluorine-free infrared nanosecond laser ablation strategy to fabricate superhydrophobic copper surfaces with integrated thermal conductivity. An H62 brass substrate was pre-coated with a PDMS/copper powder mixture and directly ablated in air. Orthogonal optimization identified scan spacing 200 μm, 20 passes, scan speed 150 mm/s, and PDMS:Cu mass ratio 2:1 as optimal. The resulting surface (SHS-Cu) exhibited a hierarchical micro/nanostructure with coral-reef-like micro-skeletons and nano-flocculent features, achieving a water contact angle (WCA) of 158.4° and sliding angle (WSA) of 6°. Mechanical stability tests showed WCA of 149° after 45 sandpaper abrasion cycles and 147.7° after 240 g sand impact. Thermal stability at 300 °C for 12 h maintained WCA >151.8° and WSA <9°. Continuous steam exposure for over 9 h preserved superhydrophobicity (WCA >151.4°), with full recovery after 100 °C heat treatment for 2 h. Condensation heat transfer coefficient (HTC) at ΔT = 1 K reached 2.12 times that of smooth copper for pure PDMS, and 5.85 times for the composite coating (2.76 times that of pure PDMS). The copper powder network reduces interfacial thermal resistance, synergizing with dropwise condensation. This method offers a scalable, environmentally benign route for high-performance condensation surfaces.