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Metals are indispensable engineered materials for day-to-day life. Researches focused on metallic surfaces with superlyophobicity (superhydrophobicity, superoleophobicity, underwater superoleophobicity and slippery characteristic) have attracted much attention recently. Nature is a magician that gives each organic life a unique advantage. Researchers have created a large number of biomimetic superlyophobic metallic surfaces through various approaches. These biomimetic superlyophobic metallic surfaces exhibit advantages in many applications, such as self-cleaning, corrosion resistance, anti-icing, and drag reduction. In this review, the specific fabrication and applications of biomimetic superlyophobic metallic surfaces were reported. The remaining challenges and future outlook of biomimetic superlyophobic metallic surfaces were preliminarily analyzed. It is hoped that the review will be essential for broadening the scope of potential applications of metals and providing a powerful reference for future research on metal-based advanced functional materials.

As two typical aspects of the wettability based on bio-inspired functional surfaces, superhydrophobic and anisotropic wetting properties have attracted much interest in practical applications. However, how to use a simple approach to realize those properties is still a huge challenge; simultaneously, the corrosion resistance is also important when the surfaces are introduced into more complex environments. In this paper, a simple and highly effective two-step approach for the fabrication of bio-inspired superhydrophobic and anisotropic wetting surfaces is reported. Aluminum alloy (Al) plates were first structured using nanosecond laser, and then were placed in an oven for low-temperature annealing (100 °C). The results show that the nanosecond laser ablation not only builds dual- and three-level structures inspired by lotus leaf and rice leaf but also oxidizes the Al materials, resulting in an oxide film covering on the surface. After the low-temperature annealing, the as-fabricated surfaces display the superhydrophobic and anisotropic wetting properties by adjusting the scan spacing of adjacent microgrooves. The potentiodynamic polarization and electrochemical impedance spectroscopy tests show that the as-fabricated surfaces have excellent corrosion resistance that can provide an effective protection for the Al materials. In addition, this approach can be applied to a broad range of metals (stainless steel, copper and titanium). This research will be instructive for the applications of functional materials with the properties of superhydrophobicity and anisotropic wetting.

In this work, the localized electrochemical micro additive manufacturing technology based on the FluidFM (fluidic force microscope) has been introduced to fabricate micro three-dimensional overhang metal structures at sub-micron resolution. It breaks through the localized deposition previously achieved by micro-anode precision movement, and the micro-injection of the electrolyte is achieved in a stable electric field distribution. The structure of electrochemical facilities has been designed and optimized. More importantly, the local electrochemical deposition process has been analyzed with positive source diffusion, and the mathematical modeling has been revealed in the particle conversion process. A mathematical model is proposed for the species flux under the action of pulsed pressure in an innovatively localized liquid feeding process. Besides, the linear structure, bulk structure, complex structure, and large-area structure of the additive manufacturing are analyzed separately. The experimental diameter of the deposited cylinder structure is linearly fitted. The aspect ratio of the structure is greater than 20, the surface roughness value is between 0.1&ndash, 0.2 &mu, m at the surface of bulk structures, and the abilities are verified for deposition of overhang, hollow complex structures. Moreover, this work verifies the feasibility of 3D overhang array submicron structure additive manufacturing, with the application of pulsed pressure. Furthermore, this technology opens new avenues for the direct fabrication of nano circuit interconnection, tiny sensors, and micro antennas.

Reducing the contact time of a water droplet on non-wetting surfaces has great potential in the areas of self-cleaning and anti-icing, and gradually develops into a hot issue in the field of wettability surfaces. However, the existing literature on dynamic behavior of water drops impacting on superhydrophobic surfaces with various structural shapes is insufficient. Inspired by the microstructure of lotus leaf and rice leaf, dual-level and three-level structures on plane and convex surfaces were successfully fabricated by wire electrical discharge machining on aluminum alloy. After spraying hydrophobic nanoparticles on the surfaces, the plane and convex surfaces with dual-level and three-level structures showed good superhydrophobic property. Bouncing dynamics of impact droplets on the superhydrophobic surfaces wereinvestigated, and the results indicated that the contact time of plane superhydrophobic surface with a three-level structure was minimal, which is 60.4% less than the plane superhydrophobic surface with dual-level structure. The effect of the interval S, width D, and height H of the structure on the plane superhydrophobic surface with three-level structure on contact time was evaluated to obtain the best structural parameters for reducing contact time. This research is believed to guide the direction of the structural design of the droplet impinging on solid surfaces.

Despite the success of previous methods for fabricating underwater superoleophobic surfaces, most of the surfaces based on soft materials are prone to collapse and deformation due to their mechanically fragile nature, and they fail to perform their designed functions after the surface materials are damaged in water. In this work, the nanosecond laser-induced oxide coatings on hydrophilic bulk metals are reported which overcomes the limitation and shows the robust underwater superoleophobicity to a mechanical challenge encountered by surfaces deployed in water environment. The results show that the surface materials have the advantage that the underwater superoleophobicity is still preserved after the surfaces are scratched by knife or sandpaper and even completely destroyed because of the hydrophilic property of damaged materials in water. It is important that the results provide a guide for the design of durable underwater superoleophobic surfaces, and the development of superoleophobic materials in many potential applications such as the oil-repellent and the oil/water separation. Additionally, the nanosecond laser technology is simple, cost-effective and suitable for the large-area and mass fabrication of mechanically durable underwater superoleophobic metal materials.

Ti6Al4V is often used in the manufacture of biomedical equipment due to its excellent properties such as light weight, high strength and good corrosion resistance in the physiological environment. Therefore, it is very important to form a non-toxic antibacterial surface on Ti6Al4V material. In this paper, a micro-nano manufacturing method of Ti6Al4V antibacterial surface was studied. In this process, the surface was firstly cut by low speed wire electrical discharge machine, and then the cut surface was hydrothermal treated. The antibacterial surface prepared by this process had the characteristics of non-toxic, stable structure, and would not cause bacteria to develop drug resistance. The preparation process is simple, friendly to the environment, and can realize mass production. The influence of different cutting times on the antibacterial surface morphology in the low speed wire electrical discharge machining was studied. The micron-grade surface obtained after three cutting times was of good quality, less molten material and high wear resistance. The influence of two etching agents mixed with different molar ratios on the micro-nano structure of antibacterial surface during hydrothermal treatment was analyzed. When the molar ratio of A and B solution was 14:1, the surface structure of the best size was obtained, and the wear resistance of the micro-nano structure surface was improved compared with the polished surface. The antimicrobial test results show that the surface of the prepared workpiece had obvious antimicrobial properties compared with the surface of the polished part after cultured for 24 h. The bacteriostatic rate of Escherichia coli was 49.55%. Based on the above, the research results of this paper have positive significance for the development of micro-nano antibacterial surface.

In this work, the reaction films were generated on the Ti–6Al–4V alloy by means of high-speed wire electrical discharge machining (WEDM-HS) technology in order to improve its microhardness and corrosion resistance. The microhardness was evaluated by using a nanoindentation tester. The corrosion behaviour was studied using measurements of potentiodynamic polarisation and electrochemical impedance spectroscopy. The experimental results showed that the processed alloys presented a higher microhardness than the matrix, and the thicker film on the surface had a greater microhardness. Additionally, the corrosion resistances of the processed alloys were superior, which could have been due to the lower corrosion current densities and the higher impedance values. Furthermore, the corrosion current densities of the processed alloys would decrease with thicker reaction films. This research provides important insights into the surface modification of titanium alloys.

Herein, we report for the first time the use of ethanol for the switchable underwater wettability on a rough titanium dioxide (TiO2) surface. The rough TiO2 thin films on the titanium surfaces are fabricated by the high speed wire electrical discharge machining (HS-WEDM) processes, and the resultant surfaces show the switch between underwater superhydrophobicity and oleophobicity via ethanol immersion and dark storage. The underlying mechanism of the switch is depicted, and the result shows that during the ethanol immersion and dark storage, the change of hydroxyl groups leads to the switch. Considering that the use of ethanol is time-saving and low-cost, we anticipate that the use of ethanol will open up a new way of surface wettability change.

The surface of the titanium alloy was blackened by a nanosecond pulsed laser, and two-dimensional and three-dimensional morphology observations and microstructure reflection measurements were performed by scanning electron microscopy (SEM), laser confocal scanning microscopy (LCSM) and microscopic angular resolution spectrometry (ARM). The effect of laser processing depth on reflectivity was studied by one-way filling scanning method. The results show that under different laser processing times, different microstructures are formed, and as the number of laser processing increases, the reflectivity of light decreases. In the 400–1000 nm band, the reflectance of the sample can be reduced to a minimum of about 1%.

The hard and brittle nature of Zirconium-based metallic glass (Zr41.2Ti13.8Cu12.5Ni10Be22.5) makes it difficult to meet industrial requirements in mechanical processing. Therefore, the processing performance of WEDM of MG was studied by using the advantages of WEDM to process hard and brittle conductive materials in this paper. The effects of peak current, pulse width and voltage on material removal rate (MRR) and surface roughness (Ra) were investigated by orthogonal experiment. Analysis of variance was employed to analyze the experimental results and obtain the optimal combination of parameters. In addition, machined surface topography was analyzed. The results show that the degree of influence of each process parameter on MRR from high to low is peak current, pulse width and voltage; and the degree of influence on Ra from high to low is pulse width, peak current and voltage. MRR and Ra are proportional to peak current and pulse width. Interestingly, the MRR and Ra do not increase with increasing voltage, but tend to increase first and then decrease. There are craters, microspheres, hard convex edges, droplets and surface microcracks on the surface of the machined workpiece. This study provides a theoretical reference for promoting the research on WEDM of MG.

Nature gives us a large number of inspirations in designing functional materials. Many plant leaves with self-cleaning properties are ubiquitous in nature. These plants have hierarchical structures, which have extreme repellency to liquids and have considerable technical potential in various applications. Herein, we present a method for fabricating bionic taro leaf surfaces by direct laser interference lithography (DLIL) and hydrothermal treatment. The micro-pillar array structure (MPA) was fabricated by DLIL, and a layer of nano-grass structure (NG) was grown on it by hydrothermal treatment. Experiments indicate that the hierarchical composite structures not only have a satisfactory superhydrophobic function with the apparent contact angle (CA) of 172° and sliding angle (SA) of 4°, but also have a strong anti-icing ability with the delay time (DT) of 3723 s. The method is simple and high-efficient for fabricating bionic self-cleaning and anti-icing surfaces.

In this work, a method for the fabrication of two- and three-dimensional curved surfaces with robust underwater superoleophobicity is reported for the first time on light alloys (including 5083 Al and TC4 Ti alloys) through the high speed wire electrical discharge machining (HS-WEDM). The surface morphology and compositions were characterized by scanning electron microscope and energy-dispersive X-ray spectrometer. The results showed that rough structures and a layer of oxidization were created on the light alloys by HS-WEDM cutting. The two- and three-dimensional structured curved surfaces after an ethanol immersion exhibited the extreme underwater superoleophobic property with the high oil contact angle and low oil sliding angle. More importantly, the underwater superoleophobic surfaces with the three-dimensional curved features could have many new applications. In order to use the potential functions, the durability of the fabricated samples was tested and the results showed that the samples still exhibited the underwater superoleophobic property after the underwater storage and physical mechanism tests. Additionally, this method is versatile, simple, environment-friendly, and cost-effective.

Titanium alloy has been widely used in the aerospace field due to its advantages of low density, high specific strength and high-temperature resistance. Its scope of application, however, has been narrowed down because of its high reflectivity to light. In order to maximize the potential, it becomes necessary to construct a surface light trapping structure of titanium alloy. Therefore, a simple and tunable method was introduced in this paper to fabricate antireflection microstructures on titanium alloy surface with the superhydrophobicity based on nanosecond laser. By optimizing the laser processing speed parameters, microstructured surfaces with low reflectance over the entire visible wavelength range and near-infrared region (400–1000 nm) can be obtained. Results indicate that when the scanning speed is 100 mm/s, the minimum reflectance in the 900–1000 nm wavelength range is less than 1%, and the total reflectance in the 500–1000 nm wavelength range stabilizes below 6%. In contrast, the surface of conventional titanium alloy absorbs only about 50% of the incident light, and the remaining 50% is reflected. Furthermore, treated surfaces demonstrate effective performance concerning hydrophobicity, with a maximum contact angle of 153.03°. The results show that the nanosecond laser can induce the anti-reflection and super-hydrophobic properties, and improve the absorption capacity of the surface.

In this paper, SiCp/2024Al composites was drilled by electrical discharge machining (EDM) to investigate the effect of different electrode cross-section shapes on material removal rate (MRR). The material removal mechanism (MRM) at different discharge energy were also analyzed by changing the electrical parameters. It is found that the MRR of EDM with tube electrode is 5 times greater than that of with cylinder electrode. Electro-erosion debris filled in the discharge gap makes the tool electrode retreat frequently, greatly reducing the MRR. The MRM includes thermal spalling, melting/vaporization and oxidation. The MRM varies with different discharge energy. Thermal spalling is the main MRM at low discharge energy, while melting/evaporation occupies a dominant position in MRM at high discharge energy. Either low or high discharge energy, oxidation always occurs.

Vibration-assisted cutting as one of specially typical precision non-conventional machining methods, recently, has aroused lots of scholars and science researchers interests, especially in hard and brittle material cutting with a significant challenge. The objective of present study develops a novel apparatus which combines mechanical and control design, a series of cutting experiments conducted on Al 7075 alloy that defined as one of high strength alloy materials appliance in lots of industries field to investigate the feasibility and reliability of the appliance. In present paper, a mechanical model of vibration- assisted cutting apparatus was designed and than evaluated by off-line test analysis. The novel apparatus can work at below 124 Hz with maximum stroke 27.285µm. Fuzzy PID was preliminary introduced into vibration-assisted cutting apparatus control strategy. Programs were established based on LabVIEW software and then downloaded into NI Compact 9033 controller in order to control vibration-assisted cutting apparatus. By compared with three strategies each other, the tracking error of fuzzy strategy increased 11.2 times that of fuzzy PID, at the same time, PID strategy oscillation amplitude increased 5.3 times that of fuzzy PID. A series of cutting experiments were conducted on the plane and freeform surface deforming. The validity and availability of vibration-assisted cutting apparatus were conducted in experiments.

Materials with special wettability have drawn considerable attention especially in the practical application for the separation and recovery of the oily wastewater, whereas there still remain challenges of the high-cost materials, significant time, and complicated production equipment. Here, a simple method to fabricate the underwater superoleophobic and underoil superhydrophobic brass mesh via the nanosecond laser ablation is reported for the first time, which provided the micro-/nanoscale hierarchical structures. This mesh is superhydrophilic and superoleophilic in air but superoleophobic under water and superhydrophobic under oil. On the basis of the special wettability of the as-fabricated mesh, we demonstrate a proof of the light or heavy oil/water separation, and the excellent separation efficiencies (96%) and the superior water/oil breakthrough pressure coupled with the high water/oil flux are achieved. Moreover, the nanosecond laser technique is simple and economical, and it is advisable for the large-area and mass fabrication of the underwater superoleophobic and underoil superhydrophobic mesh in the large-scale oil/water separation.

A simple and inexpensive one-step laser cladding method is reported to make the stainless steel mesh underwater superoleophobic. The micro/nanoscale morphologies were created via cladding a copper foil onto the stainless steel mesh using the nanosecond laser marking system. The fabricated stainless steel mesh has the underwater superoleophobic property with oil contact angles greater than 150°. Based on the special wettability, the fabricated stainless steel mesh is used to separate the light oil–water mixtures, and the separation efficiencies are >98.3%.

In order to investigate the influence of the recast layer obtained by wire electrical discharge machining (WEDM) for 7075 aluminum alloy on the mechanical physical properties of the workpiece, we carried out research on the geometry parameters, microstructure, adhesion, wear resistance and corrosion resistance of the recast layer. The results show that the unit thermal power density decreases, the surface roughness Ra value increases, and the amount of the electric erosion craters and the micro/nano pits decrease with the increase of current and voltage. In the meantime, the thickness and hardness of the recast layer are increased, so the wear resistance and corrosion resistance are significantly improved. In addition, the surface hardness plays a major role in increasing wear resistance.