This study numerically investigates the spreading and retracting dynamics of Janus drops on the inner surfaces of cylinders using the Volume of Fluid method. The results indicate that increasing surface curvature enhances spreading in the axial direction and promotes the detachment of the low-viscosity water component, particularly under conditions of high viscosity ratio and Weber number. A regime map is constructed to identify the critical conditions for separation, revealing that surfaces with intermediate curvature exhibit higher separation efficiency compared to those with high curvature. The temporal evolution of axial momenta in the x and z directions highlights the role of viscosity contrast in inducing asymmetric deformation. A scaling law for residence time is proposed as a function of Weber number, which aligns well with simulation results in the high Weber number regime. These findings provide fundamental insights for optimizing surface curvature and fluid composition to enhance drop separation and may benefit applications such as selective liquid extraction, surface cleaning, and microfluidic manipulation.

Condensation is an important research topic that ensures increased energy efficiency. Our researchers aimed to optimize heat transfer in industrial heat exchanger tubes through surface modification. We first succeeded in fabricating superhydrophilic and superhydrophobic tubes using surface modification. We observed the condensation phenomenon on the outside of the tube and evaluated the heat transfer performance through a condensation experimental facility. As a result, we found that the condensation heat transfer efficiency of superhydrophobic tubes is superior to that of conventional tubes. However, the heat transfer efficiency of the superhydrophobic tube reduced with an increase in saturation. To improve performance degradation, superhydrophilic and superhydrophobic hybrid tubes were fabricated and evaluated for their potential to improve heat transfer efficiency. As a result, we found that the liquid film generated by filmwise condensation on the superhydrophilic surface swept past the residual droplets generated by dropwise condensation on the superhydrophobic surface, resulting in the best heat transfer performance. Our results break the stereotypes of previous studies and provide a new paradigm for achieving optimal heat transfer performance on large-area curved surfaces. This research is expected to be widely applied in a variety of industries where energy efficiency is critical.

In a pilot natural super-hydrophobic surfaces study, a super-hydrophobic surface was made by coating, etching, laser ablation, chemical vapor deposition and lithography. In this study, cone-shaped periodic micro and nano-structures were constructed on a silica surface with femtosecond and picosecond laser, and the period of micro-structures between cone shape patterns was increased with 10 μm intervals. The contact angle and image of the super-hydrophobic surface were analysed and the cone (Aspect-ratio 1.27) shape model with micro-protrusion structure similar to the surface of the lotus leaf was made to measure the contact angle. To analyse the differences in the contact angles between the cone shapes and heights of the micro-protrusion, different samples with cone (Aspect-ratio 1.27), sphere (Aspect-ratio 1.00) shapes were made through laser micro-machining technology. To mimick the natural lotus leaves, the optimum condition was a cone shape. Samples of PDMS with different shapes and mixed micro/nano-structures were fabricated with a PDMS mold insert. The largest contact angle was measured at 170.42° which is similar to the contact angle of the lotus leaf. This mold insert could be used repeatedly. The molding process is advantageous for large areas and mass production.

In this paper, we present a simple and robust fabrication method for mushroom-shaped microstructures using diverse polymers with various modulus of elasticity. Through the repeated replica molding process, we fabricated the same PDMS mushroom structure negative mold as the prepared silicon master mold. To evaluate the fabricating stability of the fabricated PDMS negative mold, the mushroom-shaped structures were replicated from the mold using six types of polymer resins with different elastic modulus and we measured superhydrophobic properties on the samples. All the fabricated samples exhibited superhydrophobicity, and we proved the structural stability of the proposed replication method through the measured SEM images, contact angles on the samples, and theoretical analysis based on the structural shape.

A simple and rapid method of fabricating Mg(OH)2 layer by chemical immersion was developed to improve the corrosion resistance of the magnesium alloy AZ31. The fabricated surface was superhydrophobic with a self-assembled monolayer coating of silane. The surface characteristics were evaluated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS). The average water contact angle and sliding angle were determined to be 160° and 7° respectively as a result of wettability test. Potentiodynamic polarization indicated that both Mg(OH)2 layer and the thin layer of air were effective in improving anti-corrosion. This method which is efficient with regard to time and cost would be useful for magnesium industries and its application

Various techniques for separating mixed oil and water have been developed for the purpose of controlling marine oil pollution and for the purification of wastewater containing oil from industrial processes. In this work, we fabricate porous polydimethylsiloxane (PDMS) capsules to develop a high-performance, selective oil absorber. A template method using a sugar cube is used to fabricate the porous PDMS structure by dissolving the sugar template after infiltrating it with the PDMS solution. A hollow capsule structure was prepared by controlling the infiltration time of the PDMS into the sugar template. Contact angle measurements revealed the highly porous surface of the PDMS capsule maximized the differences between hydrophobicity and oleophilicity, which improved the absorption selectivity of oil from water. The fabricated PDMS capsules exhibited superhydrophobic and superoleophilic wetting properties; the oil droplets were absorbed into the PDMS capsule upon contact, while the water droplets were not absorbed with a contact angle above 170˚. Since the absorbed oil can be stored in the capsule pores, the oil absorption capability per unit weight of the absorber is highly increased. The adsorption performance and recyclability of the PDMS capsules were also evaluated using various waste oils.

Super-wettability surface has various applications and actively studied in many fields. However water droplet transmissivity on super-wettability mesh was not be studied. This work is about water droplet transmissivity of an aluminum mesh with super-wettability on its surface. The mesh which fabricated surface structures with semi-permanent and non-etching process has super-wettability without strength drop of mesh structure. With this process, water droplet transmissivity was measured along various mesh pore per inch and dropping angle. Also water droplet transmissivity along dropping height was measure with super-hydrophobic mesh. As a result, super-hydrophilic mesh shows similar transmissivity behavior with bare mesh which has hydrophilic surface at high pore per inch and high dropping angle, super-hydrophobic 120 mesh shows lowest water droplet transmissivity in various situation.

A study of super-hydrophobic surface originated from the analysis of lotus leaf in the nature and fabrication method of super-hydrophobic surface on copper substrate has been researched for, showed functional surfaces with anti-corrosion. However, since copper nanowires decomposed during thiol coating, it is necessary to reseach on the relation with morphology of copper nanowires and thiol coating time. In this study, the research is all about the effect of thiol coating time on wettability of copper nanowires surface. Copper hydroxide nanowires were made up by oxidation using dipping method and a polymer layer was formed on nanowires using thiol coating. Surface characteristics were assessed using scanning electron microscopy and liquid contact angles. The conclusion showed relation for wettability of thiol coated copper hydroxide nanowires with thiol coating time and proposed method would be favorable for anti-corrosion functional surface.

A study about superhydrophobic surface started from the analysis of lotus leaf, and superhydrophobic surface fabrication methods have been researched. These methods cannot be used on various metals because the fabrication methods have complex and material-selective processes. In this work, we report a simple fabrication method using abrasive blasting and a self-assembled monolayer coating to produce a superhydrophobic surface. Abrasive blasting was used to create microstructures on metal surfaces. Random peak and valley microstructures were created after abrasive blasting, and a surface profile was measured to analyze the relationship between blasting pressure and a roughness parameter. A hydrophobic material coating was performed by a self-assembled monolayer method. Six kinds of metal surfaces displayed superhydrophobic properties. This utilitarian method could be applied to diverse applications.