Biomimetic Superhydrophobic Surfaces Research Articles

Biomimetic Superhydrophobic Triboelectric Surface Prepared by Interfacial Self‐Assembly for Water Harvesting

AbstractExtracting water from air offers a promising route to address the global challenge of water scarcity. However, bionic engineering surfaces for water harvesting often struggle with efficiently coordinating droplet nucleation and desorption. The recently emerging triboelectric effect at the liquid–solid interface offers a novel approach for developing bionic fog harvesting surfaces. In this study, inspired by Namib Desert beetles and lotus leaves, a biomimetic superhydrophobic surface with nanoscale hydrophilic domains is prepared via interfacial self‐assembly, exhibiting heterogeneous wettability for effective water harvesting. The essence of interfacial self‐assembly lies in the synergy of non‐covalent interaction forces, driving the self‐assembly of nanoparticles into surface micro‐nano hierarchical structures, thereby regulating wettability and increasing potential nucleation sites. Additionally, the triboelectric effect can directly utilize the triboelectric charges to facilitate droplet migration. The triboelectric effect can be generated by flexible mechanical input induced by walking, which enhances interfacial mass transfer, thereby rapidly improving droplet removal and achieving a 39.02% increase in water harvesting efficiency. This study has opened up a new breakthrough for the design of portable and efficient water harvesting systems.

Corrosion and Protection of Chinese Bronze Relics: A Review

The corrosion problem affecting ancient Chinese bronze relics and the protective measures required post-excavation are crucial for the study of historical cultural heritage and for ensuring heritage revitalization and sustainable development. This work includes a statistical analysis, clusters information, and thoroughly examines international research on bronze relic corrosion and protection. It delves into the timeline and trends of research, the main countries leading the research efforts, the research content, and the relationships between these factors. A comprehensive review is provided on the corrosion principles, materials, detection methods, and protection techniques for bronze. The study explores the corrosion principles and processes of bronze from a materials science perspective both before and after excavation. It summarizes non-destructive detection methods and examines specific factors that influence corrosion. Furthermore, the article reviews current corrosion protection methods for bronze and related protection materials, including commonly used strategies such as surface corrosion inhibitors and organic resin coatings for protection. It also discusses the potential application of advanced corrosion protection methods in the realm of metal materials in recent years to safeguard bronze. Proposing innovative solutions, the study suggests the possibility of constructing biomimetic superhydrophobic surfaces to create a barrier isolating humid air from contacting bronze materials, thereby reducing the adhesion of corrosive media to the substrate and significantly diminishing the likelihood of corrosion. In conclusion, the article looks towards the future, considering the challenges and potential development directions for the corrosion protection of bronze and related protection materials.

Recent advances in biomimetic superhydrophobic surfaces: focusing on abrasion resistance, self-healing and anti-icing.

Superhydrophobic materials have been widely used in the fields of materials engineering and the coating industry due to their excellent abrasion resistance, corrosion resistance, anti-icing and antibacterial properties and have also attracted the attention of many researchers. However, in the process of application, their superhydrophobic surface is susceptible to external factors such as physical or chemical effects, resulting in the loss of low surface energy materials or the destruction of micro- and nano-rough structures, thus losing their superhydrophobic properties. This review describes the research progress in three aspects of superhydrophobic surfaces: abrasion resistance, self-healing, and anti-icing. Firstly, the definition and application of superhydrophobic surfaces, as well as the basic principle and mechanism of superhydrophobic surfaces are introduced. Then, the research status and improvement methods of superhydrophobic surfaces are presented in detail from three aspects, such as abrasion resistance, self-healing, and anti-icing. Finally, the research process of superhydrophobic surfaces is evaluated and prospected in order to provide a new perspective for the preparation of superhydrophobic surfaces with a wide range of applications and better performance.

Lotus leaf and shark skin-inspired micro-, nano-, hierarchical superhydrophobic surfaces for anti-fouling applications

Fouling, the accumulation and adhesion of unwanted contaminants, is a serious issue around the world in many aspects including industrial transport, marine ecological environment, maintenance of infrastructures, etc. which costs hundreds of millions of dollars and lots of manpower and material resources. Multiscale hierarchical surface structures of superhydrophobic surfaces possess various intriguing properties which provides new platforms for fabricating artificial anti-fouling surfaces. In particular, lotus leaf and shark skin with their unique micro-, nano-, hierarchical surfaces structures are highlighted as emerging tools for anti-bacterial, anti-dust, anti-corrosion, anti-icing, drag reduction applications and so on. In this review, we first provide basic information on two famous superhydrophobic states. After that we outlined the biological models and applications of lotus leaf and shark skin respectively. The self-cleaning effect of superhydrophobic lotus leaf due to their multiscale hierarchical surface structures is discussed after which anti-bacterial applications with three kinds of mechanisms and self-cleaning properties are outlined. Biological models of superhydrophobic shark skin are presented followed by their real-life applications in aircrafts and turbine blades. In addition, we discuss the potential drawbacks of recent biomimetic anti-fouling superhydrophobic surfaces like the loss of anti-fouling hydrophobic materials, adaptability to extreme environments, production and use costs and other problems as well as the possibilities of combine superhydrophobic structures and materials with high temperature resistance, oxidation resistance and other characteristics in order to be applied in more industries fields.

A robust and multifunctional superhydrophobic coating based on natural palygorskite for corrosion protection of aluminum alloys

Biomimetic superhydrophobic surfaces have become an increasingly hot topic in the area of aluminum alloy protection. However, it remains a significant challenge to construct superhydrophobic coatings with reliable durability and multifunction through simple and economical strategies. In this study, we designed a novel superhydrophobic coating with a water contact angle of ∼165.0° and a sliding angle of ∼2.4° on Al alloys by spraying hydrophobically modified natural palygorskite (SH-PAL) on the pre-cured epoxy resin (EP). The resulting superhydrophobic coating (EP@SH-PAL) exhibits good mechanical resistance, UV resistance, hot water repellency, chemical stability, thermal stability, and self-healing capabilities against plasma etching. Corrosion tests reveal that the protection efficiency of the EP@SH-PAL sample is up to 99.98 %, which remains at a high value of 90.30 % even after 20 days of immersion in 3.5 wt% NaCl. This improved corrosion resistance is attributed to the synergistic physical shielding from the SH-PAL topcoat and the EP primer. Meanwhile, molecular dynamics simulations of the mechanical durability and corrosion resistance of the EP@SH-PAL coating were performed to support the experimental results at the microscopic level. In addition, the above-prepared superhydrophobic coating also demonstrates excellent self-cleaning and antifouling characteristics. This research will provide a new method for fabricating low-cost, multifunctional, superhydrophobic anticorrosion coatings on aluminum alloys and other metal substrates.

Study on biomimetic superhydrophobic mechanisms and existing issues

The realm of biomimetic superhydrophobic surfaces encompasses a diverse range of applications, yet the specific biomimetic mechanisms, theories, models, and preparation methods remain shrouded in ambiguity. To address this gap, a meticulous examination of the current theories and preparation methods is imperative for guiding further biomimetic superhydrophobic research. This study, adopting a dual perspective from superhydrophobic theory and the intricate interplay between droplets and surfaces, intricately synthesizes the relevant theories and models pertaining to biomimetic superhydrophobic microstructures. Delving into the existing challenges in theoretical research and preparation methods within the field of biomimetic superhydrophobics, the research not only identifies current limitations but also lays the groundwork for future explorations. This systematic inquiry contributes not only to a nuanced understanding of existing biomimetic superhydrophobic surfaces but also provides a robust foundation for future studies and technological innovations. As the research unfolds, it propels the scientific community towards a more comprehensive grasp of biomimetic superhydrophobic phenomena, promising advancements, and applications across various scientific and technological domains.

When mussel meets lotus leaf and pitcher plant: A combinational biomimetic strategy for Mg-Li corrosion inhibition

Magnesium-lithium alloys hold immense promise as lightweight structural materials due to combination of unique properties. However, their widespread application is hindered by the inherent poor corrosion resistance. This research presents a novel and cost-effective approach to address this obstacle by utilizing metal-phenol networks inspired by mussel as surface modifiers. These networks facilitate the deposition of nanoparticle on magnesium-lithium (Mg-Li) alloys through chemical reactions between phenolic groups and metal ions. The resulting surface is further enhanced by spray-coating a sheet-like biomimetic superhydrophobic surface (SHS) of alkyl-ketone dimer (AKD), subsequently followed by lubricant infusion with dimethylsilicone oil to create a slippery liquid-infused porous surface (SLIPS). Characterization using multiple techniques confirms the chemical composition and morphology of the modified surface, which significantly improves the corrosion resistance of the magnesium-lithium alloy. Importantly, scanning Kelvin probe measurements reveal that SHS and SLIPS enhance the atmospheric corrosion resistance of the material. Further validation in 3.5 wt% NaCl solution demonstrates remarkable effectiveness of SLIPS. During the initial stages of immersion, the impedance magnitude |Z|0.01 Hz for SLIPS reaches a remarkable 3.78 × 107 Ω·cm2, exceeding those of the SHS, TA-LA141, and bare LA141 by 3, 3, and 6 orders of magnitude, respectively. This performance persists even after long-term immersion, with the SLIPS coating still exhibiting an impedance value one order of magnitude higher than the SHS after extended exposure. These results establish the effectiveness of SLIPS as a promising candidate for significantly upgrading the corrosion resistance of Mg-Li alloy, paving the way for their broader utilization in demanding fields.

Fundamental characteristics of biomimetic superhydrophobic surface of nitinol alloy fabricated via laser cauterization and FAS modification

Biomimetic superhydrophobic surfaces draw inspiration from the biological realm, seeking to replicate and refine their superhydrophobic properties. Fabricating super-hydrophobic surface on nitinol has significant application value in medicine, biomedical science, industry, and micro electric system due to the special performance of this material with super-hydrophobicity. In this study, we achieved a super-hydrophobic surface on a laser-processed rough nitinol surface through FAS modification, and its corrosion resistance in salt electrolytes was evaluated using potentiodyjnamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements. The resulting indicated that the fabricated super-hydrophobic surface exhibited superior corrosion resistance performance. Besides, the mechanical properties of the material were also evaluated, revealing a reduction in contact angle by 2.04 and 2.82 times as well as enhanced wear its resistance. Furthermore, the promoting mechanism of chemical and abrasion stability were systematically elucidated based on scanning electron spectroscopy (SEM-EDS), 3D optical profiling, and X-ray photoelectron spectroscopy (XPS). These findings are anticipated to provide a deeper understanding of the fabrication of super-hydrophobic surfaces on nitinol alloys, thereby strengthening their potential for practical industrial and biomedical applications.

A hyperbranched-topology-mediated self-roughness approach toward robust all-organic superhydrophobic surfaces

Biomimetic superhydrophobic surfaces (SHSs) have shown promising applications in versatile scenarios. However, due to limitations of complicated templates, expensive instruments, and insufficient adhesion between adhesives and inorganic/organic nanoparticles, simultaneous implementation of facile fabrication and highly robustness of SHSs remains difficult. Here, we demonstrate a hyperbranched-topology-mediated self-roughness approach to construct an all-organic SHS. Because of the stable covalent linkages, the SHS can be applied for versatile surfaces, exhibiting high resistance to mechanical abrasions and chemical corrosions. Additionally, once wetted with alcohol, the surface turns from superhydrophobic to hydrophilic, enabling the manipulation of liquid and gas motion as well as applications as micro-reactors. This topology-mediated self-roughness strategy paves a foundation for future development of liquid-repellent coatings.

Investigation on the Corrosion Resistance Properties of Cobalt-Chromium-Molybdenum Alloy Artificial Human Body Components with Robust Biomimetic Superhydrophobic and Slippery Surfaces Based on Laser Texturing.

Cobalt-chromium-molybdenum alloy is used as a material for artificial human body components such as artificial hip joint and artificial denture and is often affected by electrochemical corrosion in human body fluids and saliva, which leads to inflammatory reactions and damage to the surrounding tissues as well as loosening and failure of the body components themselves. Few studies have been conducted to prepare corrosion-resistant coatings on the surface of Co28Cr6Mo. In this study, we used laser texturing to process a bionic 3D micronanocomposite structure on the surface of Co28Cr6Mo and quickly prepared a superhydrophobic and slippery surface coating with excellent corrosion resistance using polydimethylsiloxane solution and silicone oil modification. This surface had ultralow surface adhesion and good robustness of durability and abrasion resistance, reducing bacterial colonization or tissue adhesion and solving the problem of the lack of stability of the superhydrophobic surface. Microgrid grooves and layered nanoparticles were structurally responsible for the variation in wettability. The formation mechanism and composition of the prepared coatings were further analyzed. Electrochemical corrosion experiments were conducted on the surface in simulating body fluid and saliva environments, which showed the enhanced corrosion resistance of the prepared surface in the human body. These findings can further develop the surface functional modification of Co28Cr6Mo, accelerating basic and applied research studies on artificial human components.

Natural and biomimetic superhydrophobic surface: Review of the manufacturing techniques

Nature has produced many materials, things, and processes at all scales, from the large to the tiny. The newly growing area of biomimicry enables the development of materials, tools, and techniques with desired features by mimicking biology or nature. Consequently, the traits of animals, plants, and insects in nature have drawn much attention. Because of its surface roughness and epicuticular waxes, the lotus leaf, for instance, has a superhydrophobic surface. These surfaces feature a water-repellent effect and high and low-contact angle hysteresis. This essay briefly introduces the theoretical wetting process before describing some of the traits of several naturally occurring species. Next, a thorough analysis of artificial superhydrophobic surfaces made in the last five years utilizing the most popular fabrication methods is provided.

Biomimetic high water adhesion superhydrophobic surface via UV nanoimprint lithography

Imitating nature and comprehending its workings is a means for human beings to advance the development of functional materials. In this study, UV nanoimprint lithography technology was utilized to successfully replicate the micro-nano hierarchical structure (micro-papillae and nano-wax tube crystals) present on the surface of the natural fresh lotus leaf. A series of UV-curable waterborne polyurethane acrylate (UV-WPUA) surfaces with special wetting and superhydrophobic properties were obtained. The polydimethylsiloxane negative stamp with lotus leaf’s structure was obtained through a stamp replica molding method, and then the UV-WPUA resin covered with the negative stamp was exposed to 172 nm Xe2* excimer and medium-pressure mercury lamps to mimic the micro-nano hierarchical structure of the lotus leaf. The UV-WPUA surfaces displayed high water adhesion superhydrophobic properties, with a water contact angle reaching 160.8° and water adhesive force of 140.0 μN, and exhibiting excellent self-cleaning performance. The results indicate that higher the UV intensity, the more accurately the surface replicates the micro-nano hierarchical structure of the lotus leaf, resulting in larger water contact angle and higher adhesive force. This study paves the way for the advancement of functional surfaces through the simulation of natural materials.

Biomimetic Superhydrophobic Materials Construct from Binary Structure: A Review on Design, Properties, and Applications

AbstractIn recent decades, the development of biomimetic superhydrophobic surface structures has allowed several properties of superhydrophobic materials to be increasingly developed. This review addresses mainly three aspects. First, two kinds of structures with superhydrophobic properties: binary structures and unitary structures, are analyzed and compared. The binary structure, which includes micro‐ and nanostructures, is responsible for the development of superhydrophobicity in most natural creatures and artificial materials. And hierarchical binary structures, which combine micro‐ and nanoscale structures, actually perform better at superhydrophobic. Second, various properties of superhydrophobic materials achieved through binary structures, including self‐cleaning, antireflection, drag‐reduction, and mechanically robust and durable superhydrophobic surfaces are summarized. Each structure possesses both superiority and vulnerability. The combination of various structures can help develop adaptable and practical materials. Finally, the combinations of different properties in superhydrophobic via using a binary structure are enumerated. Materials with various properties can adapt to different working environments.

Facile fabrication of superhydrophobic porous materials using the water-based aza-Michael reaction for high-efficiency oil-water separation

Superhydrophobic porous materials are widely used in oil-water separation due to their water-blocking and oil-passing properties. However, the preparation of most superhydrophobic porous materials is generally energy-intensive and must be performed using organic solvents. In this study, we describe a straightforward and cost-effective strategy for fabricating superhydrophobic coatings on nanosized soil particle-modified stainless steel mesh (SSM). The coating is prepared via the aza-Michael reaction of stearyl acrylate and melamine-urea–formaldehyde (MUF) resin catalysed by methyl cyclodextrin in water. Superhydrophobic meshes with water contact angles (WCAs) exceeding 150° are obtained, exhibiting extraordinary water repellency. The superhydrophobic mesh also effectively prevents surface contamination, creating a self-cleaning surface that is both waterproof and dustproof. Most importantly, the superhydrophobic mesh presents excellent oil separation performance for oil-water mixtures of various compositions, maintaining extremely high separation efficiency (>98%) even after 80 cycles. Additionally, we successfully apply this strategy to the preparation of superhydrophobic melamine sponges with excellent oil adsorption capacity (17.6–44.2 g/g). This innovative study provides an effective strategy for designing biomimetic superhydrophobic surfaces and is a promising development in the field of environmentally friendly oil-water separators.

PDMS/PVDF Electrospinning Membranes for Water-in-Oil Emulsion Separation and UV Protection.

With industry development, the separation of oily wastewater is becoming more critical. Inspired by organisms such as lotus leaves, biomimetic superhydrophobic surfaces with micro-nano structures have shown great potential in this regard. In this work, PDMS/PVDF oil-water separation membranes with designed microstructures were prepared by electrospinning technology. The membrane-forming effect of electrospinning with different ratios of PDMS and PVDF was studied. The study found that membranes with high PDMS content were more likely to form microspheres, and PDMS tended to concentrate on the microspheres. The results also showed that the microspheres would bring better hydrophobicity to the membrane. When the ratio of PDMS to PVDF is 1:2, the membrane has a water contact angle of up to 150° and an oil contact angle of 0°. At this ratio, the separation efficiency of the membrane for the water-in-oil emulsion is 98.7%, and it can still maintain more than 98% after ten separation cycles, which is a good candidate for oil-water separation. Furthermore, microspheres enable the membrane to achieve macroscopic uniformity and microscopic phase separation so that the membranes have both good elongation and fracture strength. In addition, the PDMS/PVDF membranes also exhibit excellent UV resistance, and their UV protection factor is greater than 185, making them a potential UV protective material.

Efficient fabrication of ternary coupling biomimetic superhydrophobic surfaces with superior performance of anti-wetting and self-cleaning by a simple two-step method

Efficiently obtaining ideal superhydrophobic metallic surfaces through traditional laser ablation is still a challenge. Meanwhile, revealing the mechanism of the transition from superhydrophilic to superhydrophobic of laser-ablated metallic surfaces is required. Inspired by the lotus leaf, we fabricated the arrays of micro-protrusions on aluminum substrates by nanosecond laser ablation. A layer of hydrophobic species was formed on the micro-protrusions after organic adsorption process, which promoted the surface to obtain superior superhydrophobic, anti-wetting and self-cleaning properties. The principle of the transition from superhydrophilic to superhydrophobic during heat treatment process was revealed, and how organic adsorption temperature and time affect water contact angle and slide angle was clarified. We found that nano-particles can drastically reduce the solid–liquid fraction of the surface after analysis. The parameters including laser scanning space, organic adsorption time and heat treatment temperature were optimized to realize high-efficient and energy-saving production. Furthermore, superior wetting resistance to various solutions and the self-cleaning property for solid powders were experimentally indicated. Superhydrophobic aluminum surfaces could be efficiently fabricated in several hours without any expensive equipment, complicated process, strict environment and environmentally harmful chemical reagent by the proposed two-step method.

Effect of Texturing Environment on Wetting of Biomimetic Superhydrophobic Surfaces Designed by Femtosecond Laser Texturing.

Inspired by Euphorbia leaves, micrometric pillars are designed on 316L stainless steel surfaces using a femtosecond laser to achieve superhydrophobicity. In this study, we focus on wetting behavior evolution as a function of time and chemical environment. Two types of texturing designs are performed: the laser texturing of micrometric square pillars, and the laser texturing of micrometric square pillars whose tops were irradiated using various fluences to obtain a different topography on the nanometric scale. Two laser texturing environments are considered in both cases: a CO2 flow and ambient air. The main result is that 250 days after laser texturing, steady-state contact angles (SSCA) were above 130° no matter what the environment was. We also study the effect of regular wetting over time. Comparing the results of surfaces for which wetting over time was conducted and that of the undisturbed surfaces for 250 days demonstrates that performing wetting measurements when the surface is not stable led to major changes in droplet behavior. Our surfaces have a unique wettability in which droplets are in an intermediate state. Finally, using a CO2 flow did not help reach higher SSCA, but it limited the effect of regular wetting measurements.

3D-printed bionic superhydrophobic surface with petal-like microstructures for droplet manipulation, oil-water separation, and drag reduction

Recently, bioinspired mushroom or reentrant mushroom microstructures have attracted intersts of researchers for their amazing water superrepellence property. However, basic principles of exquisite microstructures design for improving water repellence are still lacking. This paper reports a novel 3D-printed biomimetic superhydrophobic surface with petal-like microstructures inspired by the droplet pinning effect of nepenthes peristome. Then, parameters such as petal number, petal proportion and spacing distance are studied and optimized to improve water repellence, which is evaluated according to droplet bearing capacity. The results show that when the petal number is 4, the spacing distance is 100 μm, and the petal proportion is 50%, the petal-like structured surface achieves its maximum droplet bearing capacity. Comparing with the common mushroom microstructures, the maximum increase rate in bearing capacity is 58.3% for the optimized petal-like microstructures. Corresponding mechanism analysis attributes such superrepellence property to the sharp edge effect and the arch curve effect. Furthermore, the excellent water repellence enables the petal-like microstructured surface to be used for water droplets manipulation, oil-water separation, and captured-air drag reduction.

Evolution of and Disparity among Biomimetic Superhydrophobic Surfaces with Gecko, Petal, and Lotus Effect (Small 18/2022)

Biomimetic Superhydrophobic Surfaces In article number 2200349, Masanobu Naito and co-workers unveil the mystery of superhydrophobic surfaces with gecko, petal and lotus effects. The study discloses a facile topography evolution path to achieve these surfaces by controlling roughness factor and length scale of roughness. It presents a manifest correlation between surface topography and water droplet dynamics. The paper provides insight into superhydrophobic science and application guidelines.

Superhydrophobic SLA 3D printed materials modified with nanoparticles biomimicking the hierarchical structure of a rice leaf

ABSTRACT The rice leaf, combining the surface properties of lotus leaves and shark skin, presents outstanding superhydrophobic properties motivating its biomimesis. We created a novel biomimetic rice-leaf superhydrophobic surface by a three-level hierarchical structure, using for a first time stereolithographic (SLA) 3D printed channels (100µm width) with an intrinsic roughness from the printing filaments (10µm), and coated with TiO2 nanoparticles (22 and 100nm). This structure presents a maximum advancing contact angle of 165° characterized by lower both anisotropy and hysteresis contact angles than other 3D printed surfaces, due to the presence of air pockets at the surface/water interface (Cassie-Baxter state). Dynamic water-drop tests show that the biomimetic surface presents self-cleaning, which is reduced under UV-A irradiation. The biomimetic surface further renders an increased floatability to 3D printed objects meaning a drag-reduction due to reduced water/solid contact area. Numerical simulations of a channel with a biomimetic wall confirm that the presence of air is essential to understand our results since it increases the average velocity and decreases the friction factor due to the presence of a wall-slip velocity. Our findings show that SLA 3D printing is an appropriate approach to develop biomimetic superhydrophobic surfaces for future applications in anti-fouling and drag-reduction devices.