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This study involves the fabrication and characterization of original, hydrophobic, superhydrophilic, superhydrophobic and hybrid biphilic pattern coupled with the flat and pillar-structured surfaces. The boiling performance of the seven wettability structured surfaces is experimentally and numerically investigated, aiming at analyzing the boiling mechanism of wetting pattern coupled with structures. The findings indicate that coupling superhydrophobicity pillar structure surface (SHO-PS) result in an excellent boiling performance, the superhydrophilicity have difficulty in improving the heat transfer coefficient and critical heat flux. Analysis of the bubble dynamics behaviors reveals a strong positive correlation between the bubble nucleation sites and bubble departure diameter, except for hydrophobic flat structured surface (HO-FS) and superhydrophobicity pillar structured surface (SHO-PS), which exhibit the negative correlation. The bubble departure frequency shows a linear correlation with the contact angle of all the modified surfaces. In the simulation, it is observed that the similar bubble dynamic behaviors in experiment.

In this study, we conducted experimental research on the pool boiling performance of mini-pillar surfaces with different hydrophobic dot arrays. The experimental results show that the distribution and total area of hydrophobic dot arrays on pillar tops significantly influence the boiling performance of mini-pillar surfaces. In comparison with the mini-pillar surface without wettability modification, introducing hydrophobic dot arrays on the pillar tops can improve the bubble nucleation density and diminish the wall superheat at boiling onset. Therefore, the boiling performance of mini-pillar surfaces can be gradually improved by increasing the total area of hydrophobic dot arrays at low heat fluxes. However, a further increase in the total area of hydrophobic dot arrays may lead to the reduction of the bubble departure frequency at high heat fluxes, which is not conducive to the segregation of the liquid and vapor pathways. The experimental results indicated that when the total area of hydrophobic pillar tops accounts for 10.24 % of the projected area of the mini-pillar surfaces, an optimal enhancement is achieved, and the optimal enhancement of boiling performance on the mini-pillar surfaces with hydrophobic dot arrays results from a suitable balance between promoting the bubble nucleation and maintaining higher bubble departure frequency.

Ultrasonic plastic welding (UPW) is a highly efficient and environmental friendly method that has gained gradually increased attention in joining carbon fiber reinforced thermoplastic (CFRTP). A crucial aspect in UPW of CFRTP is the design of the energy director (ED). This paper employs ultrasonic embossing, a cost-effective way to manufacture ED on the surface of CFRTP sheets. The effect of ultrasonic embossing time and welding time on the joint performance is investigated in terms of microstructure, tensile-shear property, and fracture surface morphology. The results show that the structured surface made by ultrasonic embossing can be used as ED to concentrate welding energy. This process reduces the randomness and dispersion of weld distribution, improves the failure load of welded joints by 30 % compared with the joints made without using ED. The ultrasonic embossing time has a limited influence on the joint failure load. Sound welded joints can be obtained when welding with one structured surface and welding time of 1.5 s.

Ultrasonic plastic welding is an efficient and green welding method, which has been widely used in the joining of carbon fiber reinforced thermoplastic composites (CFRTP) in recent years. An important step in the ultrasonic welding of CFRTP is the design of the welding joint, which largely determines the weld quality. An ultrasonic CFRTP welding method based on structured surfaces was proposed, that is, the surface of the workpiece is structured by ultrasonic embossing before welding, and energy director are processed. Taking carbon fiber reinforced nylon 66 (CF/PA66) as the research object, the effect of structured surface and welding energy on the weld formation was studied. Microstructure, tensile-shear performance and fracture characteristics of welded joint were analyzed. The results show that compared with the unstructured surface, the structured surface acting as energy director that can effectively concentrate welding energy and greatly reduce the randomness and dispersion of weld distribution, thereby improve the weld quality. Moreover, fewer defects in the weld joint can be obtained by pre-structuring two contacting surfaces.

In vitro cellular models denote a crucial part of drug discovery programs as they aid in identifying successful drug candidates based on their initial efficacy and potency. While tremendous headway has been achieved in improving 2D and 3D culture techniques, there is still a need for physiologically relevant systems that can mimic or alter cellular responses without the addition of external biochemical stimuli. A way forward to alter cellular responses is using physical cues, like 3D topographical inorganic substrates, to differentiate macrophage-like cells. Herein, protein secretion and gene expression markers for various macrophage subsets cultivated on a 3D topographical substrate are investigated. The results show that macrophages differentiate into anti-inflammatory M2-type macrophages, secreting increased IL-10 levels compared to the controls. Remarkably, these macrophage cells are differentiated into the M2d subset, making up the main component of tumour-associated macrophages (TAMs), as measured by upregulated Il-10 and Vegf mRNA. M2d subset differentiation is attributed to the topographical substrates with 3D fractal-like geometries arrayed over the surface, else primarily achieved by tumour-associated factors in vivo. From a broad perspective, this work paves the way for implementing 3D topographical inorganic surfaces for drug discovery programs, harnessing the advantages of in vitro assays without external stimulation and allowing the rapid characterisation of therapeutic modalities in physiologically relevant environments.

Liquid film flow is the dominant flow regime in distillation and absorption processes within structured packings. Extensive research has been carried out to improve the understanding of the involved fluid dynamics. Up to now, these investigations mainly focused on gravity-stabilized film flow, i.e., the liquid phase flows over a packing in counter-current flow with a gas phase. In contrast, gravity-destabilized film flow is studied much less frequently although this type of flow applies to about half of the cases in a column with structured packings. Here, the liquid runs along the underside of the packing, also in counter-current flow with the gas phase. To close the gap in the experimental data, this contribution investigates the fundamental fluid dynamics of gravity-destabilized liquid film flows on a smooth plate, a 2D wave texture, and a 3D pyramidal texture. Results on critical convective inclination angle, drained liquid mass flow, and liquid film thickness without counter-current gas flow are reported and compared to numerical results from literature. In the experiments, the Reynolds number is varied from 28.4 to 113.5 using a surfactant-modified aqueous system. The 2D structure showed decreased liquid flow stability compared to the smooth surface. However, the 3D structure seems to have a stabilizing effect on the flow. • New experimental data for gravity-destabilized film flow over structured surfaces. • Overall higher Reynolds number leads to dripping onset at lower inclination angles. • 3D pyramidal structure stabilizes the film flow, 2D wave destabilize. • 3D structure reduces the dependence of the drainage flow from Reynolds number. • Highest film thickness on 2D, smaller on 3D and smallest on smooth surface. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Multi-droplet impingement is a fundamental aspect inherent to all kinds of technical spray processes which typically aim at enhancing the convective exchange of reagents or heat at the impinged surface. In this paper, the impingement of multiple droplets onto a structured surface is investigated by a comprehensive CFD model, which resolves the dynamics of the individual droplets and the film on a micro-scale level based on the Volume of Fluid (VOF) method. The considered surface topology includes cavities and is typical for protective masks used in the spray etching of Printed Circuit Boards (PCBs). The agitation of the liquid film in terms of the convective mass transfer rates across virtual horizontal evaluation planes is studied and the influence of film height and droplet impaction velocity is elaborated. Passive tracer tracking is employed to investigate the release and re-entrainment of fluid at the surface cavities. Two modes of mass exchange between the cavities and the main flow upon droplet impingement are identified, which are central inflow accompanied by lateral outflow (1) and lateral inflow with outflow at the opposing side (2). A statistical analysis of the allocation of tracer particles shows that high impaction velocities and low film heights correlate with an enhanced decay of tracer particles within the cavities. The susceptibility to re-entrainment is also reduced by high impaction velocities, whereas increased film heights are found to promote re-entrainment. [ABSTRACT FROM AUTHOR]

With the rapid and continuous development of nanomanufacturing technology, the demands for both large range and high precision metrology of structured surfaces are becoming increasingly urgent. This paper proposes a metrological measurement system based on a commercial atomic force microscope. By using the nano-positioning platform from SIOS, the measurement range of the system expands from 110 μm × 110 μm × 20 μm to 25 mm × 25 mm × 5 mm. A signal amplifier with low noise and a high common mode rejection ratio that decreases the noise level of the measurement system to 2 nm is designed. Integration of the metrological system, signal processing, and calibration of the whole system is introduced. Three experimental studies are carried out on an ultrahigh step, an atomic deposition grating, and a cutting tool. The experimental results demonstrate high measurement repeatability and reproducibility in both vertical and lateral directions. By repeating 10 times of measurement, the expended uncertainties of the step and the grating measurement are 36.24 nm and 0.60 nm, respectively. Additionally, measurement of a cutting tool tip is conducted to illustrate the performance of the system. The Ra and Rz values of the tool tip arc ripple are 29.8 nm and 189 nm, respectively. [ABSTRACT FROM AUTHOR]

Fused silica is widely used as a material for optical lenses owing to its excellent optical properties and low thermal expansion coefficient. However, as a hard and brittle material, there is very limited option of processing technologies to machining fused silica with surface structures. In this paper, a picosecond laser based single crystal diamond tool fabrication technology is proposed to generate micro milling tools with different geometrical designs, and the tool cutting performance is experimentally tested through micro-milling of fused silica under different cutting conditions. An optimal picosecond laser processing path is proposed to inhibit the graphitization of diamond tool and improve the concentricity of tool blades, and a multi-edge milling tool with a minimum rotary diameter of 0.4 mm can be obtained. The effects of rake angle on cutting force and the degree of brittle damage on the subsurface of fused silica are studied by micro milling tests of fused silica using the laser-shaped tools. The results show that the fused silica machined by diamond milling tool with a rake angle of −30° has the best surface finish (Ra = 41.2 nm). Using this laser-machined milling tool, a plurality of micro Fresnel lenses with aperture of 1.6 mm were successfully machined on a fused silica sheet.

The structured surface-enhanced pool boiling process and associated heat transfer enhancement characteristics are numerically investigated by using the pseudopotential multiphase flow lattice Boltzmann (LB) model coupled finite difference method (FDM). In the current study, the effects of different microstructure geometries(square structures, triangular serrated structures, triangular-raised structures) and varying spacing in triangular-raised structures (d = 0, 22, 44, 66, 88, 110 l.u. (lattice units)) on boiling heat transfer (BHT) characteristics and bubble dynamics behavior are studied in detail. The results showed that microstructure can accelerate bubble nucleation. Among the three microstructures, the heat transfer performance of triangular-raised structures was significantly better than that of square and triangular serrated structures in the nucleate boiling (Ja number is 0.124-0.145). The oscillation and deformation of bubbles led to the lateral migration of bubbles, the continuous nucleation of small bubbles. The phenomenon of re-wetting of heating surface occurred in the process of bubble migration, necking, deformation and detachment was found, which enhances heat transfer in nucleate boiling. At the same time, the growth, oscillation and detachment of bubbles also perturb the liquid and enhance the natural convection around the bubbles.Therefore the main BHT mechanism of nucleate boiling on the three kinds of structured surface is the combined action of transient heat conduction and micro-convection. The variation of the spacing between microstructures showed an important effect on the BHT performance of the heating surface and the generation of activated nucleation sites in the nucleate boiling. Triangular-raised structures can enhance transient heat conduction and micro-convection, with the strongest enhancement effect at d = 66 l.u when the Ja number is 0.124.

Given the current demand for surfaces with non-polished morphology like structured surface that enhance its tribological properties, providing a method with minimal production cost and high performance has attracted attention. The present study focuses on presenting a new method for producing structured surfaces with hydrophobic performance. In this method, using the grinding process with a special grinding wheel, an attempt has been made to produce these widely used surfaces. By modifying the topography of the wheel surface and changing the arrangement of abrasive particles from random to arranged distribution with the diamond particles in predefined locations, an attempt was made to design and manufacture a special grinding wheel for the production of structured surfaces. A segment with 1*1 cm² including diamond particles with mesh size of 40/50 were manufactured during the electroplating process in a nickel bath medium and by installing the segment on the wheel hub and performing the grinding process with this developed wheel, surfaces containing continuous and discontinuous scratches with the same geometry were produced. Static contact angle test for the unstructured surface was about 37 degrees that improved to 141 degrees with the structured surface, which is an impressive improvement. [ABSTRACT FROM AUTHOR]

Multi-droplet impingement is a fundamental aspect inherent to all kinds of technical spray processes which typically aim at enhancing the convective exchange of reagents or heat at the impinged surface. In this paper, the impingement of multiple droplets onto a structured surface is investigated by a comprehensive CFD model, which resolves the dynamics of the individual droplets and the film on a micro-scale level based on the Volume of Fluid (VOF) method. The considered surface topology includes cavities and is typical for protective masks used in the spray etching of Printed Circuit Boards (PCBs). The agitation of the liquid film in terms of the convective mass transfer rates across virtual horizontal evaluation planes is studied and the influence of film height and droplet impaction velocity is elaborated. Passive tracer tracking is employed to investigate the release and re-entrainment of fluid at the surface cavities. Two modes of mass exchange between the cavities and the main flow upon droplet impingement are identified, which are central inflow accompanied by lateral outflow (1) and lateral inflow with outflow at the opposing side (2). A statistical analysis of the allocation of tracer particles shows that high impaction velocities and low film heights correlate with an enhanced decay of tracer particles within the cavities. The susceptibility to re-entrainment is also reduced by high impaction velocities, whereas increased film heights are found to promote re-entrainment.

The batch mode electrical discharge machining (EDM) method has been developed to improve the throughput and accuracy in fabricating array structures, but the process suffers from insufficient debris removal caused by the complex electrode geometry. Tool vibration has been used to improve flushing conditions, but to date the underlying mechanism of the tool vibration on the micro EDM of array structures remains unclear. This study aimed to investigate the effect of tool vibration on the machining process by direct observation of the discharge phenomena in the discharge gap by using a high-speed camera. Micro EDM experiments using 9 and 25 array electrodes were performed, and the effect of tool vibration on the discharge uniformity and tool wear was evaluated. It was found that tool vibration improved the uniformity of the discharge distribution, increased the machining efficiency, and suppressed the tool wear. The discharges occurred in periodic intervals, and the intensity increased with the amplitude of tool vibration. The results of this study indicate that the vibration parameters determine the discharge period duration and intensity to achieve optimum stability and efficiency of the machining process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Over smoothing of filtering is identified as one of the major sources of on-machine compensation in fabrication of structured surface. • A novel on-machine profile error evaluation and compensation strategy based on anisotropic diffusion filter is proposed. • The proposed method controlled the form error of high aspect ratio structured surface at the scale of submicron. Structured surfaces with high aspect ratio are promising in optical components, healthcare devices, and microelectronics. A preferable method to create precise structured surfaces is using single point diamond turning with on-machine surface measurement (OMSM). However, fabricating these surfaces often pose challenges due to steep gradients and discontinuous slopes, leading to significant form errors in machining. We propose an innovative solution by employing partial differential equation (PDE) filtration in a closed loop compensation process to enhance form accuracy and surface roughness compared to traditional methods. We tackle the problem of over-smoothing induced profile error encountered with traditional Gaussian filters. The proposed compensation strategy adapts to surface curvature and reduces instrument noise during on-machine measurements. Experimental of fabricating a segment spherical artefact, demonstrate improved precision. After adopting the proposed method, the form error is reduced from 1.2 µm to 0.5 µm and vibration ripples are mitigated, and a better surface finish is achieved. [ABSTRACT FROM AUTHOR]

• A hydrophobic patterned micro-pillar surface and nanostructure is fabricated. • Boiling characteristics were analyzed on topography and heterogeneous wettability. • The critical heat flux relates to water supply capability, not hydrophobic patterns. • A hydrophobic pattern on micro-pillar increases nucleate site density. • The requirements for the optimal boiling surface were presented. The nucleate boiling phenomenon is significantly affected by the wettability of the surface because it is greatly influenced by the motion of the solid–liquid–gas triplet formed by the behavior of bubbles on the heated surface. Hydrophilic surfaces have a high critical heat flux, and hydrophobic surfaces have low onset of nucleate boiling points and high heat transfer coefficients. To design an optimal boiling surface with the advantages of both hydrophilic and hydrophobic surfaces, in this study, parametric experiments were performed according to the spacing of the micropillar, the presence or absence of nanostructures, and the presence or absence of hydrophobic treatment on the surface where the nanostructure was hierarchically modified to the micropillar array structure in which the upper surface of the pillar was hydrophobic. Using the micro-pillar fabrication process and the heterogeneous hydrophobic surface fabrication process, a micro-pillar structure with hydrophobic treatment on top of the pillar was fabricated. Pool boiling experiments were conducted on uniform hydrophilic surfaces, uniform hydrophobic surfaces, hydrophobic patterns on hydrophilic surfaces, micro-pillar surfaces, micro-pillar with nanostructure surfaces, micro-pillar surfaces with heterogeneous wettability, and micro-pillar with nanostructure surfaces with heterogeneous wettability. Based on the experimental data, we analyzed the change in boiling heat transfer coefficients and critical heat flux according to the surface characteristics. Based on experimental results, it was confirmed that the optimal boiling surface should be a surface with heterogeneous wettability, microstructure, and nanostructure. [ABSTRACT FROM AUTHOR]

• Pool Boiling on structured surface with different arrangement of hydrophobic and hydrophilic micro-pillars was investigated. • Boiling enhancement mechanism was revealed by a 3D hybrid cascaded lattice Boltzmann method. • Partially mixed structured surfaces prove effective in limiting the occurrence of film boiling. • There exists an optimal width and arrangement of micro-pillars for boiling heat transfer. This study explores pool boiling performance of three-dimensional structured surfaces featuring square micro-pillars. The investigation employs the hybrid cascaded lattice Boltzmann method (CLBM) in conjunction with finite difference method (FDM). Four types of structured surfaces are considered: homogeneous hydrophilic surface (HHS), fully mixed surface (FMS), linear mixed surface (LMS), and staggered mixed surface (SMS). FMS alters all hydrophilic top surfaces of the micro-pillars into hydrophobic top surfaces. LMS and SMS are partially mixed surfaces in which hydrophilic and hydrophobic micro-pillars are arranged in linear and staggered, respectively. The numerical results revealed that the transition boiling interval for the partially mixed surface is notably broader than that of the HHS and FMS configurations. Among varying micro-pillar widths, all mixed surfaces attain their peak critical heat flux (CHF) at a consistent optimal width, with the SMS configuration displaying the highest CHF. In the SMS configuration, the maximum CHF difference between micro-pillars with different widths reaches 35.3%, and the CHF value increase by 46.3% compared with the HHS configuration under the optimal width. Furthermore, the SMS configuration can reduce the retention of bubbles within the gaps between micro-pillars and preventing heat accumulation on the surface. Therefore, applying a structured surface featuring staggered hydrophilic and hydrophobic micro-pillars not only enhances heat transfer but also provides equipment protection. [ABSTRACT FROM AUTHOR]

With the rapid and continuous development of nanomanufacturing technology, the demands for both large range and high precision metrology of structured surfaces are becoming increasingly urgent. This paper proposes a metrological measurement system based on a commercial atomic force microscope. By using the nano-positioning platform from SIOS, the measurement range of the system expands from 110 μm × 110 μm × 20 μm to 25 mm × 25 mm × 5 mm. A signal amplifier with low noise and a high common mode rejection ratio that decreases the noise level of the measurement system to 2 nm is designed. Integration of the metrological system, signal processing, and calibration of the whole system is introduced. Three experimental studies are carried out on an ultrahigh step, an atomic deposition grating, and a cutting tool. The experimental results demonstrate high measurement repeatability and reproducibility in both vertical and lateral directions. By repeating 10 times of measurement, the expended uncertainties of the step and the grating measurement are 36.24 nm and 0.60 nm, respectively. Additionally, measurement of a cutting tool tip is conducted to illustrate the performance of the system. The Ra and Rz values of the tool tip arc ripple are 29.8 nm and 189 nm, respectively.

In this work, the ability to reshape the grinding wheels with patterns of special and modern geometries to produce the advanced structured surfaces is studied. Firstly, a mathematical model is built for the process relating the geometry of the grinding wheel, geometries of the wheel patterns, the produced structured surfaces, and the grinding operating parameters. Then, different regular and irregular geometries are designed to be patterned over the wheel surface. The regularly designed patterns include the circular, the elliptical, and the polygonal patterns, while the heart-like patterns are included as irregular ones. Afterward, a simulation method to express the patterned wheels and the corresponding structured surfaces at different working conditions is developed. The effects of the patterns' geometries on the obtained structured surfaces at the selected working conditions are investigated. The results of the grinding operations designed and carried out experimentally reflect the dependability of the presented method for machining the advanced structured surfaces using the grinding processes. [ABSTRACT FROM AUTHOR]

Fresnel micro-lens arrays with close-to-wavelength features have significant advantages in minimization of optical systems. However, in the fabrication of a Fresnel micro-lens array by conventional diamond turning, the discontinuous features of the surface profile cause interference between the tool flank face and the finished surface. In this manuscript, a novel off-spindle-axis diamond turning method is proposed to fabricate Fresnel micro-lens array mold insert and a toolpath generation algorithm is developed. The generation of each lenslet is treated as an independent turning operation, and the whole fabrication of a Fresnel micro-lens array is completed by a succession of repetitive turning operations. With this approach, the interference between the tool and the finished surface is avoided, and the form accuracy and surface integrity are improved for each lenslet. Then, the Fresnel micro-lens array mold insert is further utilized in precision glass molding to replicate the micro-lens structures onto transparent polymer substrates. The experimental results indicate that both the diamond-turned and molded Fresnel micro-lens arrays are achieved with homogeneous quality. As an application, a compact imaging system based on the molded Fresnel micro-lens array is demonstrated. The proposed machining method in this study can be employed in the fabrication of Fresnel micro-lens arrays and other micro-optics with discontinuous profiles with high accuracy and machining efficiency. • Off-spindle-axis diamond turning is used for Fresnel micro-lens array fabrication. • Toolpath is generated by synchronizing three linear motions and a rotatory motion. • The proposed machining strategy avoids the interference between tool and workpiece. • The method enables machining Fresnel micro-lens array molds with high form accuracy. • The molded polymer Fresnel micro-lens array has homogeneous imaging quality. [ABSTRACT FROM AUTHOR]

In this study, we numerically investigate the droplet impact onto a thin liquid film deposited on a structured surface with square pillars and cavities. The time evolution of crown geometry is strongly affected by the surface structure. When the thickness of the liquid film is larger than the structure height, the expanding speed of the crown base radius is independent of the structure width. However, if the liquid film thickness is equal to the structure height, the crown base expands slower as the structure width increases. Surface structures have strong effects on the crown height and radius, and can prevent ejected filament from breaking into satellite droplets for certain cases. For the liquid film with the thickness equal to the pillar height, both the crown height and the radius exhibit non-monotonic behaviors as the pillar width increases. There exists one pillar width which produces the smallest crown height and the largest crown radius. [ABSTRACT FROM AUTHOR]

The structured surface-enhanced pool boiling process and associated heat transfer enhancement characteristics are numerically investigated by using the pseudopotential multiphase flow lattice Boltzmann (LB) model coupled finite difference method (FDM). In the current study, the effects of different microstructure geometries(square structures, triangular serrated structures, triangular-raised structures) and varying spacing in triangular-raised structures (d = 0, 22, 44, 66, 88, 110 l.u. (lattice units)) on boiling heat transfer (BHT) characteristics and bubble dynamics behavior are studied in detail. The results showed that microstructure can accelerate bubble nucleation. Among the three microstructures, the heat transfer performance of triangular-raised structures was significantly better than that of square and triangular serrated structures in the nucleate boiling (Ja number is 0.124-0.145). The oscillation and deformation of bubbles led to the lateral migration of bubbles, the continuous nucleation of small bubbles. The phenomenon of re-wetting of heating surface occurred in the process of bubble migration, necking, deformation and detachment was found, which enhances heat transfer in nucleate boiling. At the same time, the growth, oscillation and detachment of bubbles also perturb the liquid and enhance the natural convection around the bubbles. Therefore the main BHT mechanism of nucleate boiling on the three kinds of structured surface is the combined action of transient heat conduction and micro-convection. The variation of the spacing between microstructures showed an important effect on the BHT performance of the heating surface and the generation of activated nucleation sites in the nucleate boiling. Triangular-raised structures can enhance transient heat conduction and micro-convection, with the strongest enhancement effect at d = 66 l.u when the Ja number is 0.124. [ABSTRACT FROM AUTHOR]

• The surface light management techniques were used on both the solar cell and module to improve light absorption for flexible modules. • The vacuum hot-embossing process is used to prepare anti-reflective units on the front surface of PV module, resulting in a substantial maximum increase of 1.1% in J sc and 1.09% in EQE. • The flexibility of PV module was substantially improved with lower elastic modulus and lower thickness encapsulants. • The electrical properties of the flexible modules were not deteriorated even after 1000 repeated bending tests. Flexible silicon heterojunction (SHJ) solar cells have attracted considerable attention for their suitability in lightweight and flexible module applications owing to their bendable properties. One of the most significant challenges in producing flexible SHJ solar cells and modules is enhancing their light absorption characteristics, particularly when using thinner wafers. In this study, we implemented surface light management techniques at both the solar cell and module levels to improve light absorption. A MgF 2 /TCO antireflection structure was optimized for flexible SHJ solar cells, improving its external quantum efficiency (EQE) and short-circuit current density (J sc) by 2.79% and 1.50%, respectively. Additionally, a vacuum hot-embossing process was incorporated into the front surface of flexible SHJ solar modules, incorporating various sizes of semi-elliptical anti-reflective units. This approach yielded a substantial maximum increase of 1.1% in J sc and 1.09% in EQE for flexible modules. Furthermore, the radiation characteristics of flexible SHJ solar modules placed at different incident light angles and conducted stress analyses under bending conditions were also investigated. The findings revealed that flexibility was substantially improved with lower elastic modulus and lower thickness encapsulants. The electrical properties of the flexible modules were not deteriorated even after 1000 cycles of repeated bending tests. This study successfully addressed the bottlenecks encountered during the development of flexible crystalline silicon (c-Si) photovoltaics (PV) while highlighting the immense potential of these PVs for integrated applications. [ABSTRACT FROM AUTHOR]

• Combined effect of biosurfactant and structured surface on pool boiling is reported. • Heat transfer performance of biosurfactant is compared with DI water. • Structured surface have shown better heat transfer in biosurfactant than DI water. • Low surface tension, more nucleation, better wettability improved heat transfer. An attempt has been made to explore the combined effect of structured surfaces (segmented finned surface and uniform cross-section surface) and Rhamnolipid biosurfactant to improve heat transfer rate in pool boiling. Experimental investigations were performed at normal atmospheric condition and till reaching critical heat flux. The results shows that the segmented finned surface has shown better heat transfer than plain surfaces, with a 200% increase in heat transfer coefficient. In contrast, a uniform cross-section surface showed an improvement in heat transfer coefficient of 107% over a plain surface. The reasons for better thermal performance in segmented finned configuration can be associated to the reduced surface tension of the working fluid increasing more nucleation sites. Additionally, better rewetting phenomena and bubble evolution from the segmented finned surface have also assisted in improving the heat transfer rate. Moreover, the pool boiling results of all the heating surfaces with surfactant solution is compared with pure water. It has been observed that all heating surfaces have performed better with surfactant solution compared to pure water. However, the CHF obtained on all heating surfaces with surfactant solution were lesser than pure water. Low CHF is due to the foamability of the surfactant solution. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, the hybrid thermal lattice Boltzmann model is adopted to investigate the nucleation boiling. The bubble dynamics behaviors including nucleation, growth, coalescence, and departure, are studied on structured surfaces. Three types of structured surfaces adopting the rectangular, triangular, and trapezoidal structured surfaces are designed with different surface wettability. The numerical results reveal that, firstly, for the single bubble, increasing the opening width of structured surfaces from inside to outside is beneficial for bubble evolution. Then, with the dimensionless separation distance less than 1 between the two nucleation sites for the double bubbles, it presents a more noticeable advantage in the bubble evolution with different surface characteristics. Finally, the dimensionless critical coalescence distance of double bubbles increases significantly with the increment of contact angle on the hydrophobic surface. Besides, the dimensionless bubble critical coalescence distances on the triangular and rectangular structured surfaces are larger than those on the trapezoidal structured surface for the hydrophobic surface. • Evolutions of single and double bubbles on three structured surfaces are studied. • Enlarging the opening width of structured surface enhances the evolution of bubble. • Dimensionless critical coalescence distance increases on the hydrophobic surface. [ABSTRACT FROM AUTHOR]

The batch mode electrical discharge machining (EDM) method has been developed to improve the throughput and accuracy in fabricating array structures, but the process suffers from insufficient debris removal caused by the complex electrode geometry. Tool vibration has been used to improve flushing conditions, but to date the underlying mechanism of the tool vibration on the micro EDM of array structures remains unclear. This study aimed to investigate the effect of tool vibration on the machining process by direct observation of the discharge phenomena in the discharge gap by using a high-speed camera. Micro EDM experiments using 9 and 25 array electrodes were performed, and the effect of tool vibration on the discharge uniformity and tool wear was evaluated. It was found that tool vibration improved the uniformity of the discharge distribution, increased the machining efficiency, and suppressed the tool wear. The discharges occurred in periodic intervals, and the intensity increased with the amplitude of tool vibration. The results of this study indicate that the vibration parameters determine the discharge period duration and intensity to achieve optimum stability and efficiency of the machining process.

This report quantifies the influence of inorganic fullerene-like tungsten disulfide (IF-WS2) nanoparticles on the pool-boiling performance of R134a/polyolester mixtures on a commercial (Turbo-ESP) boiling surface. Tungsten disulfide nanoparticles, of roughly 150 nm, were used at a 15% mass fraction in a base polyolester lubricant to produce the test nanolubricant. The nanolubricant was mixed with Rl 34a at a 1% mass fraction. The study showed that the nanolubricant caused an average 37% degradation in the boiling heat flux as compared to R 134a/neatlubricant boiling on a reentrant cavity surface at the same superheat. Similarly, boiling with Rl 34a/neat-lubricant caused, on average, a 27% degradation in the boiling heat flux as compared to pure R 134a boiling and the same superheat. An analysis was presented which showed that the nanoparticles were too large and too dense to promote a boiling enhancement. In addition, the fullerene-like structure and the large size encouraged nanoparticle settling. which presumably filled cavities of the boiling surface leading to additional boiling degradations. [ABSTRACT FROM AUTHOR]

The basement membrane (BM) is a thin specialized extracellular matrix that functions as a cellular anchorage site, a physical barrier and a signaling hub. While the literature on the biochemical composition and biological activity of the BM is extensive, the central importance of the physical properties of the BM, most notably its mechanical stiffness and topographical features, in regulating cellular function has only recently been recognized. In this Review, we focus on the biophysical attributes of the BM and their influence on cellular behavior. After a brief overview of the biochemical composition, assembly and function of the BM, we describe the mechanical properties and topographical structure of various BMs. We then focus specifically on the vascular BM as a nano- and microscale structured surface and review how its architecture can modulate endothelial cell structure and function. Finally, we discuss the pathological ramifications of the biophysical properties of the vascular BM and highlight the potential of mimicking BM topography to improve the design of implantable endovascular devices and advance the burgeoning field of vascular tissue engineering. [ABSTRACT FROM AUTHOR]

In comparison to tactile sensors, optical techniques can provide a fast, nondestructive profile/areal surface measurement solution. Nonetheless, high measurement noise, unmeasured points, and outliers are often observed in optical measurement, particularly for structured surfaces. To alleviate their detrimental impacts on the characterization of surface topography as well as the examination of micro/nanoscale geometries, a post processing filtering technique, i.e., the clustering filter, which is essentially an iterative process to find the aggregation center of a cluster of points, is implemented. The clustering filter is particularly useful for noises and outlier suppression for optical measurement of structured surfaces due to its edge-preserving capability. Five surface samples with structured features are measured by an in-house developed dispersive interferometer and a commercial white light interferometer, thereafter the measured surface data are filtered by the clustering filter. Both noise and outliers are suppressed, which not only facilitates the visualization and characterization of surface topography, but also enables the accurate evaluation of local functional geometries. [ABSTRACT FROM AUTHOR]

In vitro cell models play important roles as testbeds for toxicity studies, drug development, or as replacements in animal experiments. In particular, complex tumor models such as hepatocellular carcinoma (HCC) are needed to predict drug efficacy and facilitate translation into clinical practice. In this work, topographical features of amorphous silicon dioxide (SiO2) are fabricated and tested for cell culture of primary HCC cells and cell lines. The topographies vary from pyramids to octahedrons to structures named fractals, with increased hierarchy and organized in periodic arrays (square or Hexagonal). The pyramids were found to promote complex 2D/3D tissue formation from primary HCC cells. It was found that the 2D layer was mainly composed of cancer-associated fibroblasts (CAFs), while the 3D spheroids were composed of tumor cells enwrapped by a CAF layer. Compared with conventional protocols for 3D cultures, this novel approach mimics the 2D/3D complexity of the original tumor by invading CAFs and a microtumor. Topographies such as octahedrons and fractals exclude tumor cells and allow one-step isolation of CAFs even directly from tumor tissue of patients as the CAFs migrate into the structured substrate. Cell lines form spheroids within a short time. The presented inorganic topographical surfaces stimulate complex spheroid formation while avoiding additional biological scaffolds and allowing direct visualization on the substrate.

The demand for functional films with surface microstructures is increasing in industry. Functional films with multi-directional wavy components can be applied to fluid drag reduction in turbulent flow applications. In order to implement the high-efficiency manufacturing of functional films, it is necessary to machine wavy microgrooves onto the surfaces of roll molds first. The molds can then be used to imprint patterned films. However, the machining of complicated microgrooves with multi-directional wavy components has never been reported so far. In this study, the authors propose a two-directional wavy microgrooving process by introducing simultaneous reciprocating motions of a diamond cutting tool driven by a slow tool servo. First, microgrooving experiments were conducted by oscillating the tool in two single directions, namely tangential and normal directions of the surface, and the material removal mechanism in each experiment was investigated. In tangential direction tool oscillation, burrs formed on the edge of the groove, which were suppressed by appropriately setting the oscillation amplitude and the tool clearance angle. In normal direction oscillation, shear angle changed significantly with the groove depth, which in turn influenced the groove surface roughness. By synthesizing the results of single-direction oscillation cutting, wavy grooving was performed by reciprocating the tool in both directions simultaneously. As a result, two-directional wavy grooves were successfully machined with form accuracy of 1.2 μm P-V and surface roughness of 12.2 nm Ra. Then, the microgrooved roll molds were used in ultraviolet resin imprinting tests to fabricate films with wavy microstructures. The wavy microstructures were precisely transferred to the resin films with a transcription error of less than 0.7 μm P-V. The results of this study provide a new approach to rapid manufacturing of functional films with wavy microstructures.

In vitro cellular models denote a crucial part of drug discovery programs as they aid in identifying successful drug candidates based on their initial efficacy and potency. While tremendous headway has been achieved in improving 2D and 3D culture techniques, there is still a need for physiologically relevant systems that can mimic or alter cellular responses without the addition of external biochemical stimuli. A way forward to alter cellular responses is using physical cues, like 3D topographical inorganic substrates, to differentiate macrophage-like cells. Herein, protein secretion and gene expression markers for various macrophage subsets cultivated on a 3D topographical substrate are investigated. The results show that macrophages differentiate into anti-inflammatory M2-type macrophages, secreting increased IL-10 levels compared to the controls. Remarkably, these macrophage cells are differentiated into the M2d subset, making up the main component of tumour-associated macrophages (TAMs), as measured by upregulated Il-10 and Vegf mRNA. M2d subset differentiation is attributed to the topographical substrates with 3D fractal-like geometries arrayed over the surface, else primarily achieved by tumour-associated factors in vivo . From a broad perspective, this work paves the way for implementing 3D topographical inorganic surfaces for drug discovery programs, harnessing the advantages of in vitro assays without external stimulation and allowing the rapid characterisation of therapeutic modalities in physiologically relevant environments., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

This paper quantifies the pool boiling performance of R1336mzz(Z) on a flattened, horizontal Turbo-ESP surface for air-conditioning and industrial heat recovery applications for heat fluxes between roughly 10 kWm−2 and 120 kWm−2. The R1336mzz(Z) pool boiling curve was measured for three saturation temperatures and exhibited the best performance with respect to saturation temperature near the middle saturation temperature of 298.1 K. The study showed that the boiling performance of R1336mzz(Z) on the Turbo-ESP did not differ statistically from that of R123 for heat fluxes between 13 kWm−2 and 59 kWm−2. For heat fluxes larger than 59 kWm−2, the R123 boiling heat flux was up to 5% larger than the heat flux for R1336mzz(Z). A pool boiling model was modified to include a convective term and was used to predict boiling heat transfer for the test refrigerants on the Turbo-ESP surface, mostly, to within ±0.5 K. [ABSTRACT FROM AUTHOR]

The rapid development of additive manufacturing technology provides a more flexible and efficient manufacturing solution for the high value-added parts with a complex topology. However, the poor surface finish poses a major obstacle for the wide application of the additively manufactured components when their functionality and tolerance are benchmarked with those produced by the conventional process. In selective laser melting, visible pattern and texture of the printed layers and unmolten particles cannot be avoided although research works have been conducted to improve the surface finish by optimising the selective laser melting strategy and process parameters. Therefore, a dedicated post-processing technique is generally required to improve the surface finish of the additively manufactured products in terms of various levels of geometric complexity. In this study, a vibration-assisted conformal polishing tool is developed to finish a representative v-groove structure fabricated by selective laser melting. Experiments are conducted to investigate the effects of abrasive size and polishing time on the improvement in surface roughness. The developed technique in this paper can be applied to finish the additively manufactured internal structures such as honeycomb structure and irregular holes that have linear projection along a single axis. [ABSTRACT FROM AUTHOR]

Evaporation of water droplets on a structured surface is studied experimentally. With an increase in the wall temperature Tw from 28-70 °? the exponent n increases from 1-1.37 in the evaporation law (j = dm/dt ~ R0 n, where m is the droplet mass and R0 is the droplet radius). Usually, researchers simulating droplet evaporation consider a linear relationship between the evaporation rate, j, and the droplet radius, R0 (n = 1). This paper shows an increase of the exponent, n, with a growth of the wall temperature, Tw. The diffusion vapor layer on the droplet interface and the boundary air layer on the surface of the heated cylinder with a diameter exceeding the droplet's one are formed. A neglect of free convection more than five times underestimates calculation results compared with experimental data. At droplet evaporation it is necessary to take into account convection in a vapor-gas medium and wall roughness. [ABSTRACT FROM AUTHOR]

Evaporation and heat transfer of layers of aqueous salt solutions have been studied. The behavior of salt solutions is compared for a smooth and micro-structured wall with a rectangular profile. The evaporation rate of the salt solution on the structured wall is 20-30% higher than on the smooth one at high salt concentration. Previously, it was thought that the heat transfer for solutions can be calculated for thin layers and films without taking into account the natural convection in liquid. In this paper, the liquid free convection is shown to play a key role. A simple model linking the solutal and the thermal Marangoni numbers and the Peclet number with free convection of the liquid on a hot structured wall is considered. For correct simulation of the non-isothermal heat and mass transfer, it is necessary to take into account local characteristics of thermal and velocity fields inside a layer of the salt solution, as well as to determine the average characteristic scales of circulation into the liquid. To simplify the analysis it is possible to effectively consider four types of characteristic convective scales, the role of which depends on the thickness and diameter of the solution layer, as well as on the wall temperature. The strong influence of free convection in a thin layer of the solution is extremely important for accurate modeling of a wide range of modern technologies. Intensification of heat transfer and evaporation due to the use of a structured wall can be applied in heat exchangers, to improve efficiency in desalination of water, in energy technologies (e.g., in heat absorption pumps), as well as in chemical technologies. [ABSTRACT FROM AUTHOR]

Highlights • Pool boiling heat transfer enhancement by segmented finned structured surface. • Segmented finned structured surface provides better surface wettability. • Better heat transfer performance of the present surface compared to existing structured surfaces. • Better bubble dynamics and better rewetting phenomena improve the heat transfer performance. Abstract An experimental investigation has been carried out to investigate pool boiling heat transfer characteristics of segmented finned (SF) microchannels structured surface and compare its performance with that of uniform cross-section (UCS) microchannels structured surface and plane surface. All three surfaces have been fabricated on individual copper block with a foot print area of 10 × 10 mm2. Pool boiling experiments have been performed with these surfaces in atmospheric pressure condition using deionized water. Experiments have been performed for applied effective heat flux range of 0–200 W/cm2. Both the structured surfaces show better heat transfer performance compared to plane surface. It has been observed that SF structured surface shows a heat transfer improvement up to a factor of 3 times the heat transfer coefficient in plane surface whereas uniform UCS structured surface shows the improvement by a factor of 2 times the heat transfer coefficient in plane surface. Thus segmented finned microchannels structured configuration shows better heat transfer performance compared to other two surfaces. The reason behind the heat transfer improvement in SF configuration might be due to more number of active nucleation sites, better rewetting phenomenon and favorable bubble growth and release mechanism. [ABSTRACT FROM AUTHOR]

The present study is focused on investigation of heat transfer from a porous plate by cooling of air with transpiration cooling. Effects of Reynolds number of hot gas stream, inlet temperature of air and mass flow rate of water on local wall temperature and cooling effectiveness of porous flat plate and efficiency of the system inside a rectangular channel with air as a hot gas stream and water as a coolant were investigated numerically. Increasing Reynolds number causes an increase on surface temperature and a decrease on cooling effectiveness of porous plate and efficiency of the system. Increasing of air inlet temperature does not cause a significant increase on cooling efficiency of the system. An increase of water flow rate causes a decrease on surface temperature and an increase on effectiveness of porous plate and cooling efficiency of the system. Numerical results prepared by RNG k-ε turbulence model have a good approximation and show a similar flow characteristic with experimental results. [ABSTRACT FROM AUTHOR]

The apparent contact angle is typically used to quantify the wettability on rough or structured surfaces. In particular, the prediction of the apparent contact angle is essential to design and control the surface wettability on structured surfaces. Researchers have questioned the validity of Wenzel and Cassie–Baxter equations regarding utilizing solid material of interfacial contact area instead of that at the triple contact line to calculate the apparent contact angle. In this study, we devised a new method to predict the apparent contact angle on a structured surface by utilizing the properties of actual contact angle derived from the "transversality condition." The transversality condition shows that when a liquid is in equilibrium on a smooth curved solid surface, the actual contact angle equals the Young's contact angle (disregarding influence of line tension). By treating the structured surface as a curved surface, the equilibrium condition was applied to calculate the apparent contact angle on both smooth and non-smooth structured surfaces. Experiments were conducted on surfaces with both concentric and parallel V-shaped grooves, which served to verify our conclusion. The proposed model demonstrates that the apparent contact angle is only influenced by the material at the triple contact line and remains independent of the contact area, a principle that is, however, violated by the Wenzel and Cassie equations. Furthermore, the model facilitates exploration of the manner in which different shapes of micro–nano structures with the same roughness factor impact the apparent contact angle, a phenomenon that the Wenzel equation fails to explain. According to various authors and the experimental results in this study, the Wenzel equation was deemed inadequate for calculating the apparent contact angle on most structured surfaces. The proposed method for accurately predicting the apparent contact angle holds potential to offer scientific guidance in the development of structured surfaces with precisely controlled wettability. This has a broad range of applications in fields such as microfluidics, biography, engineering. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A new technique was introduced to manufacture a functional surface with water repellency feature through grinding process. • The effect of surface structure on solid–liquid interface properties was studied. • Based on the solid–liquid interface evaluations, the hydrophobicity of the manufactured surface was improved by about 263% compared to the untreated surface. • An analytical model for predicting the solid–liquid surface property was simultaneously developed. • A good correlation, with maximum error of 4%, was obtained between the experimental result and analytical model. Nowadays, multiple strategies have been suggested to improve product efficiency on the basis of risk free techniques. Owing to the vast applications of the structured surface in many industrial sectors, considerable attention has been paid by many scholars to improve the surface performance aspects by studying their solid–liquid interface characterizations. In the current study, a new technique is introduced to manufacture a functional surface with water repellency feature through grinding process. Based on the solid–liquid interface evaluations of the modified surface, by structuring the surface, the contact angle increases from 35° (untreated surface) to 127° for structured surface. Therefore, the reinforced surface showed hydrophobicity with a 263% improvement for a scratch area fraction more than 75%. Formation of air pads trapped in the vacant space of the scratches was the main cause to enhance contact angle for structured surface. Since air molecules have very low inclination to chemical bonding with water molecules, the water droplet did not penetrate the scratches space and contact angle enhanced. A new analytical model for predicting the solid–liquid surface property was simultaneously developed by interaction of the kinematics of the grinding technique with single diamond and the basic wettability theory of the Cassie-Baxter. Therefore, the effect of all input parameters on the output results was studied in terms of achieving the best solid–liquid interaction performance through expanded model. The optimal values were calculated and the proposed structured surface was manufactured during the grinding process. According to the value of the static contact angle measured during experimental tests (127°) and its analytical value (123°), less than 4% error was observed between the results, which showed the high accuracy of the equation expanded on the present work. [ABSTRACT FROM AUTHOR]

Evaporation and heat transfer of the layers of water and aqueous salt solutions (H 2 O/LiBr, H 2 O/CaCl 2 , H 2 O/LiCl) have been studied experimentally. Evaporation rate is greater for a structured wall than for a smooth one. When simulating droplet evaporation and heat transfer, it is necessary to take into account free convection of air and vapor. There is a change of the heat transfer coefficient for salt solutions layers on the structured surface with the presence of an extremum. The largest value of the heat transfer coefficient α on the structured surface corresponds to water for the final stage of evaporation. For salt solutions, α is lower than that of water. The maximum excess of heat transfer coefficient of micro-structured wall above the smooth wall (20–25%) corresponds to the maximum height of the liquid layer for the initial period of evaporation. With increasing time, the excess is reduced. [ABSTRACT FROM AUTHOR]

Irradiation of a single-crystal diamond tool was performed with a picosecond pulsed laser to produce a tool with a microgrooved edge. This tool was then used in a metal cutting process to transfer the edge grooves onto a workpiece. Suitable conditions for laser irradiation on the diamond tool were experimentally investigated in terms of groove shape and laser-induced damage to diamond. Two different kinds of cutting experiments were performed; a uniformly grooved surface and a hierarchically structured surface were obtained. The chip formation mechanisms in the metal grooving process were examined. A copper workpiece was rapidly machined the surface of which had microgrooves with a pitch of a few micrometers. An increase of the contact angle was observed on the grooved surface, indicating the improvement of water repellency. This study presents an efficient method to machine microgrooves on metal materials for functional surfaces. [ABSTRACT FROM AUTHOR]

Water evaporation in a wide range of initial droplet diameters and at different wall temperatures on structured surface was studied experimentally. With an increase in the wall temperature from 31 to 72 °С and an increase in the initial droplet diameter, exponent n in the evaporation law increases from 1 to 1.37. Under the transitional regime, exponent n = 1.6 reaches its maximum. Usually, while simulating droplet evaporation, a linear relationship of the evaporation rate of water vapor and droplet radius R is considered ( dm / dt ∼ R n , n = 1). In this paper, it is shown that exponent n increases with a growth of the wall temperature. In generalization of droplet evaporation rate, the exponent for the Rayleigh number ( Ra ) is 0.457 due to the predominant role of gas convection. For large water drops (for air–vapor mixture over the droplet surface) high Reynolds numbers are achieved ( Ra = 2 × 10 5 ). A diffusion vapor layer on the droplet surface and boundary layer of air on the surface of the heated cylinder, whose diameter exceeds the droplet diameter, are formed. A neglect of free convection understates simulation results in comparison with experimental data more than by the factor of 10. The sequence of key factors, taking into account their influence on the rate of droplet evaporation, is as follows: 1) convection in a vapor–gas medium; 2) effect of wall roughness, wettability, and convection in a liquid; 3) thermal inertia of the metal wall. The calculation methodology for a sessile drop enables a qualitative analysis for a high-temperature gas-droplet flow. [ABSTRACT FROM AUTHOR]

This paper discusses a fabrication process of high aspect ratio (AR) silicon micro-/nano-pore structures and modification of their surfaces to improve the function of liquid-infused-type self-cleaning surfaces. The structure and its hydrophobic surface play an important role to hold a special liquid (a lubricant) on the surface tight to produce an intermediate lubricant layer and any liquid drops, including low surface tension liquids such as oil, can slide easily on it. The nanopore structure with an AR as high as 30 was fabricated by etching in a solution of hydrofluoric acid and hydrogen peroxide. This process based on a catalyst reaction of an array of Au islands that was deposited on a silicon substrate through a particle mask. This original hydrophilic surface was changed to hydrophobic one by depositing self-assembled monolayer of octadecyltrichlorosilane to modify the energy balance at the interface of the solid structure, the lubricant, another liquid, and air. Then the lubricant could be well retained. The functional lifetime was evaluated by measuring the liquid residue on the surface after number of liquid dash. It was confirmed that longer lifetime was obtained with higher AR nanopore structure.

This work describes a method for the metrological characterization of structured surfaces using a confocal microscope. The proposed method is based on the calculation of texture parameters established in ISO 25178-2:2012. To ensure the traceability of these parameters, a procedure for the calibration of the Z-axis of the confocal microscope is proposed. The calculation of uncertainty associated with each parameter employs the Monte Carlo method, as well as the concept of a virtual instrument. The validity of the algorithms has been verified through the use of synthetic data provided by the National Institute of Standards and Technology (NIST) and physical standards, with minimum differences being obtained between the certified values and calculated or measured values. Finally, using the proposed method, the topography of a structured surface manufactured by laser machining is evaluated, obtaining the most used roughness parameters, as well as their measurement uncertainties and possible correlations. In general, it can be affirmed that it is possible to obtain metrologically reliable results with the proposed method.