飞秒激光刻蚀沉积联合 PVDF 涂覆的超疏水表面制造 (特邀)

Objective To address the common issues of poor hydrophobic layer adhesion and low durability in traditional metal-based superhydrophobic surfaces, and to meet the urgent demand for high-performance surface protection in aerospace, marine engineering, and other extreme environments, this paper proposes a novel composite fabrication method that combines femtosecond laser etching with polyvinylidene fluoride (PVDF) coating. The goal is to create efficient and long-lasting superhydrophobic metal surfaces. Stable micro/nano hybrid structures are built on the surface and treated with low-surface-energy materials. This approach enhances performance in harsh environments. Method First, using commercial titanium sheets as substrates, multi-level micro/nano composite structures were fabricated via femtosecond laser processing (Fig.1). The optimal values of laser repetition rate and single-pulse energy were determined through a control variable approach. Meanwhile, two different processing strategies—coarse-hatch repetitive scanning and fine-hatch fill scanning—were designed and compared by varying processing parameters. Subsequently, a PVDF/DMF mixed solution was prepared and applied onto the laser-processed surfaces using a drop-coating method with multiple coating cycles. Field emission scanning electron microscopy (FE-SEM), laser confocal microscopy, contact angle measurements, and X-ray diffraction (XRD) were employed to comprehensively characterize the samples’ micro-morphology, specific surface area, wettability, and phase composition. Results and Discussion Experimental results revealed that the optimal femtosecond laser processing parameters are a repetition rate of 200 kHz and a single-pulse energy of 8 μJ (Fig.2). After four PVDF coatings, the sample processed via fine-hatch fill scanning (scanning speed: 50 mm/s, scanning pitch: 10 μm, single scan pass) achieved a contact angle of 160.2°, significantly higher than that of the coarse-hatch repetitive scanning sample (scanning speed: 30 mm/s, scanning pitch: 50 μm, four scan passes) after eight coatings, which reached only 153.0° (Fig.5). Moreover, the fine-hatch fill scanning sample achieved a superhydrophobic state (contact angle ≥ 150°) after just two coating cycles. X-ray diffraction (XRD) analysis indicated that higher scanning speeds reduced the formation of deposits such as TiO₂ and enhanced structural hierarchy (Fig.4). Surface morphology analysis demonstrated that, when measured over a smaller area, the fine-hatch fill scanning method yielded the highest specific surface area, indicating that this approach produces richer multi-scale hierarchical micro/nano structures. These features contribute to improved hydrophobic performance. Compared to coarse-hatch repetitive scanning, the small-spacing filling method eliminates the need for repeated scanning, significantly enhancing processing efficiency. Additionally, it provides stronger coating adhesion and superior stability. Conclusions This study successfully develops an efficient and robust method for fabricating superhydrophobic metal surfaces by synergistically combining femtosecond laser-induced micro/nano structuring with PVDF coating. The optimized process achieves an excellent contact angle of 160.2° with fewer coating cycles and faster scanning speeds, offering simplified processing, enhanced durability, and reduced resource consumption. By overcoming key limitations such as coating delamination and poor long-term performance, this method demonstrates strong scalability and great potential for industrial applications. It provides a practical and feasible technical pathway for surface functionalization of metals operating in extreme environments.