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.
Key words
femtosecond laser direct writing /
two-photon polymerization /
biomimetic structure /
structural topology /
wettability /
adhesion
{{custom_sec.title}}
{{custom_sec.title}}
{{custom_sec.content}}
References
[1] 程静, 李政浩, 李欣怡, 等. 超疏水表面在血液接触类医疗器械中的应用进展[J]. 表面技术, 2025, 54(10): 47-60.
CHENG J, LI Z H, LI X Y, et al.Advance in Application of Superhydrophobic Blood-Repellent Surfaces for Medical Devices[J]. Surface Technology, 2025, 54(10): 47-60.
[2] WANG H, ZHANG Y L, HAN D D, et al.Laser Fabrication of Modular Superhydrophobic Chips for Reconfigurable Assembly and Self-Propelled Droplet Manipulation[J]. PhotoniX, 2021, 2(1): 17.
[3] YUE J H, ZHENG H Y, CHENG X Q, et al.A Review on the Research Progress of Turbulent Drag Reduction and Gas Layer Stability on Superhydrophobic Surfaces[J]. Journal of Hydrodynamics, 2025, 37(1): 100-114.
[4] 秦立果, 刘建波, 李航, 等. 水下湍流减阻技术研究进展[J]. 表面技术, 2024, 53(16): 1-18.
QIN L G, LIU J B, LI H, et al.Research Advances in Drag Reduction Technologies for Submarine Turbulence[J]. Surface Technology, 2024, 53(16): 1-18.
[5] FILLION R M, RIAHI A R, EDRISY A.A Review of Icing Prevention in Photovoltaic Devices by Surface Engineering[J]. Renewable and Sustainable Energy Reviews, 2014, 32: 797-809.
[6] YUAN B H, ZHAO H D, YANG F Z, et al.The Design of a Metal—Organic Framework with Flame-Retardant Performance and Bionic Hydrophobic Surface Inspired by the Lotus Leaf[J]. New Journal of Chemistry, 2022, 46(37): 17874-17879.
[7] YANG J F, LONG F, WANG R Y, et al.Design of Mechanical Robust Superhydrophobic Cu Coatings with Excellent Corrosion Resistance and Self-Cleaning Performance Inspired by Lotus Leaf[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2021, 627: 127154.
[8] JU J, BAI H, ZHENG Y M, et al.A Multi-Structural and Multi-Functional Integrated Fog Collection System in Cactus[J]. Nature Communications, 2012, 3: 1247.
[9] LIU C C, XUE Y, CHEN Y, et al.Effective Directional Self-Gathering of Drops on Spine of Cactus with Splayed Capillary Arrays[J]. Scientific Reports, 2015, 5: 17757.
[10] QU C, ROZSA J L, JUNG H J, et al.Bio-Inspired Antimicrobial Surfaces Fabricated by Glancing Angle Deposition[J]. Scientific Reports, 2023, 13: 207.
[11] OH J, DANA C E, HONG S, et al.Exploring the Role of Habitat on the Wettability of Cicada Wings[J]. ACS Applied Materials & Interfaces, 2017, 9(32): 27173-27184.
[12] LIU X J, GU H C, DING H B, et al.3D Bioinspired Microstructures for Switchable Repellency in both Air and Liquid[J]. Advanced Science, 2020, 7(20): 2000878.
[13] LIU C C, JU J, ZHENG Y M, et al.Asymmetric Ratchet Effect for Directional Transport of Fog Drops on Static and Dynamic Butterfly Wings[J]. ACS Nano, 2014, 8(2): 1321-1329.
[14] ZHENG Y M, GAO X F, JIANG L.Directional Adhesion of Superhydrophobic Butterfly Wings[J]. Soft Matter, 2007, 3(2): 178-182.
[15] BIXLER G D, BHUSHAN B.Bioinspired Rice Leaf and Butterfly Wing Surface Structures Combining Shark Skin and Lotus Effects[J]. Soft Matter, 2012, 8(44): 11271.
[16] DAI H Y, GAO C, SUN J H, et al.Controllable High-Speed Electrostatic Manipulation of Water Droplets on a Superhydrophobic Surface[J]. Advanced Materials, 2019, 31(43): 1905449.
[17] XIN Q P, XIE K Q, LIANG Q Q, et al.Electrospinning in Membrane Contactor: Manufacturing Elec-PVDF/SiO2 Superhydrophobic Surface for Efficient Flue Gas Desulphurization Applications[J]. Green Chemical Engineering, 2021, 2(1): 111-121.
[18] BAKHTIYARI A N, YADAV A, WU Y L, et al.Enhancing Wettability of Sapphire (Al2O3) Substrate through Laser Surface Texturing[J]. Materials Letters, 2024, 355: 135506.
[19] WANG L Y, LIU M M, YADAV A, et al.A Method for Preparing and Investigating Anti-/de-Icing Surface by Integration of Laser-Induced Graphene (LIG) with a Silica Sol Adhesive (SMP@M-SiO2)[J]. Surface and Coatings Technology, 2023, 474: 130111.
[20] GHODRATI M, MOUSAVI-KAMAZANI M, BAHRAMI Z.Synthesis of Superhydrophobic Coatings Based on Silica Nanostructure Modified with Organosilane Compounds by Sol-Gel Method for Glass Surfaces[J]. Scientific Reports, 2023, 13: 548.
[21] LI X J, GAO L K, WANG M, et al.Recent Development and Emerging Applications of Robust Biomimetic Superhydrophobic Wood[J]. Journal of Materials Chemistry A, 2023, 11(13): 6772-6795.
[22] ZHANG M Q, ZHOU T, LI H, et al.UV-Durable Superhydrophobic ZnO/SiO2 Nanorod Arrays on an Aluminum Substrate Using Catalyst-Free Chemical Vapor Deposition and Their Corrosion Performance[J]. Applied Surface Science, 2023, 623: 157085.
[23] YAO X, CHEN Q W, XU L, et al.Bioinspired Ribbed Nanoneedles with Robust Superhydrophobicity[J]. Advanced Functional Materials, 2010, 20(4): 656-662.
[24] 赵圆圆, 金峰, 董贤子, 等. 飞秒激光双光子聚合三维微纳结构加工技术[J]. 光电工程, 2023, 50(3): 220048.
ZHAO Y Y, JIN F, DONG X Z, et al.Femtosecond Laser Two-Photon Polymerization Three-Dimensional Micro- Nanofabrication Technology[J]. Opto-Electronic Engineeing, 2023, 50(3): 220048.
[25] BHUSHAN B, HER E K.Fabrication of Superhydrophobic Surfaces with High and Low Adhesion Inspired from Rose Petal[J]. Langmuir, 2010, 26(11): 8207-8217.
[26] DONG S L, ZHANG X L, LI Q, et al.Springtail-Inspired Superamphiphobic Ordered Nanohoodoo Arrays with Quasi-Doubly Reentrant Structures[J]. Small, 2020, 16(19): e2000779.
[27] LIU T L, KIM C C.Turning a Surface Superrepellent even to Completely Wetting Liquids[J]. Science, 2014, 346(6213): 1096-1100.
[28] TUTEJA A, CHOI W, MABRY J M, et al.Robust Omniphobic Surfaces[J]. Proceedings of the National Academy of Sciences of the United States of America, 2008, 105(47): 18200-18205.
[29] VU H H, NGUYEN N T, KASHANINEJAD N.Re-Entrant Microstructures for Robust Liquid Repellent Surfaces[J]. Advanced Materials Technologies, 2023, 8(5): 2201836.
[30] LIN Y, ZHOU R, XU J.Superhydrophobic Surfaces Based on Fractal and Hierarchical Microstructures Using Two-Photon Polymerization: Toward Flexible Superhydrophobic Films[J]. Advanced Materials Interfaces, 2018, 5(21): 1801126.
Funding
National Key Research and Development Program of China (2022YFB4600402); National Natural Science Foundation of China (U24A20109); Shandong Provincial Natural Science Foundation (ZR2026MS0719, ZR2024ME068)
PDF(2822 KB)
