目的 针对现有仿生疏水表面研究缺乏跨物种系统性对比且过度依赖含氟化学修饰的问题,本研究通过几何结构设计探索润湿性的纯物理调控途径,揭示固液接触面积分数（Φ）与侧壁倾角（ψ）对润湿态稳定性及黏附性的协同作用机制。方法 选取仙人掌、月季花瓣、蝉翼和弹尾虫表皮4种典型生物原型,将其表面特征抽象为圆锥、圆台、圆柱和倒圆台4种标准微结构,采用双光子聚合激光直写技术,精确制备了上述仿生微结构阵列（Φ由0增至0.442,ψ由0°增至99.5°）。通过静态接触角测量、扫描电镜、拉曼光谱和EDS元素分析,结合数值模拟,系统考察不同结构形貌对表面润湿性、润湿动态行为及黏附性能的影响。结果 随着Φ和ψ递增,表观接触角由82.5°逐渐提升至149.5°,倒圆台结构在不借助任何低表面能修饰下接近超疏水阈值。仿真与理论模型揭示,倒圆台结构的重入式侧壁提供最高突破压力（2 759 Pa）,可形成稳定气垫,有效维持Cassie-Baxter润湿态,但其回缩边缘同时导致三相接触线钉扎,使黏附性显著高于圆柱结构。结论 本研究通过跨物种、系统性的几何对比,揭示了Φ与ψ对润湿态稳定性与黏附性的协同调控机制,为非化学修饰的功能润湿表面设计提供了实验与理论依据。
Abstract
Biomimetic hydrophobic surfaces have long relied on fluorinated chemical modifications, yet such coatings raise environmental concerns and suffer from poor durability. Moreover, existing studies predominantly focus on replicating single biological structures, leaving cross-species, systematic comparisons of topological effects on wettability and adhesion largely unexplored. This study explores a purely physical pathway to regulate wettability through geometric structure design. To achieve systematic comparison, four representative biological prototypes, namely cactus spines, rose petals, cicada wings, and springtail cuticles, are selected and their surface features are abstracted into four standardized microstructures: cones, truncated cones, cylinders, and inverted truncated cones. Two geometric parameters are introduced to characterize the structural topology, the solid-liquid contact area fraction (Φ), defined as the ratio of the solid-liquid contact area at the structure top to the total projected unit-cell area; and the sidewall inclination angle (ψ), defined as the angle between the sidewall tangent and the horizontal substrate plane. Across the four structures, Φ increases from 0 (cones) to 0.442 (inverted truncated cones), while ψ increases from 0° to 99.5°. These biomimetic arrays are precisely fabricated via two-photon polymerization (TPP), and their surface wettability, dynamic wetting behavior, and adhesion are systematically investigated through static contact angle measurements, SEM, Raman spectroscopy, EDS, and numerical simulations.
With increasing Φ and ψ, static contact angle measurements reveal a monotonic increase with Φ: from 82.5° for cones to 95.2° for truncated cones, 109.5° for cylinders, and reaching 149.5° for inverted truncated cones, approaching the superhydrophobic threshold without any low-surface-energy modification. Volume of fluid simulations tracks liquid infiltration into inter-structural gaps, revealing distinct wetting regimes across the four geometries. Cones permit extensive liquid penetration with complete gas displacement, corresponding to the Wenzel state. Truncated cones and cylinders exhibit transitional behaviors with partial gas entrapment, characteristics of the Wenzel-Cassie transition state. Inverted truncated cones maintain the Cassie-Baxter state, with gas effectively locked within re-entrant cavities and the three-phase contact line pinned at the sharp top edges. A theoretical breakthrough pressure model quantitatively rationalizes these observations, showing that the re-entrant geometry provides the highest resistance (2 759 Pa) to liquid infiltration. Adhesion tests reveal a counterintuitive trade-off: inverted truncated cones, despite achieving the highest contact angle, and exhibit significantly stronger adhesion than cylinders, with evident droplet residue after detachment. Cylindrical structures, in contrast, enable clean droplet release. This dichotomy arises from the re-entrant sidewalls, which, while elevating breakthrough pressure and stabilizing the air layer, simultaneously induce pinning of the three-phase contact line during droplet retraction. Cylindrical vertical walls, lacking such overhanging features, minimize geometric interference and facilitate droplet detachment.
Across the four prototypes, a clear evolutionary logic emerges. Cactus/rose-like topologies (cones and truncated cones) prioritize droplet capture with low infiltration resistance. Cicada-inspired cylinders balance stable air-layer retention with ultra-low adhesion for self-cleaning. Springtail-mimetic inverted truncated cones maximize air-layer stability at the expense of detachment performance, ensuring respiratory function in humid environments. This systematic comparative analysis demonstrates that precise tuning of topological parameters, specifically Φ and ψ, enables independent control over wetting state and adhesion within a single hydrophilic material system, providing a theoretical foundation for the design and optimization of functional interfaces toward specific application requirements in droplet manipulation, self-cleaning, and microfluidics.
关键词
飞秒激光直写 /
双光子聚合 /
仿生结构 /
结构拓扑 /
润湿性 /
黏附性
Key words
femtosecond laser direct writing /
two-photon polymerization /
biomimetic structure /
structural topology /
wettability /
adhesion
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基金
国家重点研发计划（2022YFB4600402）; 国家基金区创重点（U24A20109）; 山东省自然科学基金资助项目（ZR2026MS0719, ZR2024ME068）
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