Nanotextured Surfaces Research Articles

Nanoetched Stainless Steel Architecture Enhances Cell Uptake of Biomacromolecules and Alters Protein Corona Abundancy.

Nanotexture on biocompatible surfaces promotes cell adhesion and proliferation. High aspect ratio nanoachitecture serves as an ideal interface between implant materials and host cells that is well-suited for localized therapeutic delivery. Despite this potential, nanotextured surfaces have not been widely applied for biomacromolecule delivery. Here, we employed a low-cost, industrially relevant nanoetching process to modify the surface of biocompatible stainless steel 316 (SS316L), creating nanotextured SS316L (NT-SS316L) as a material for intracellular biomacromolecule delivery. As biomacromolecule cargoes are adsorbed to the steel and ultimately would be used in protein-rich environments, we performed serum protein corona analysis on unmodified SS316L and NT-SS316L using tandem mass spectrometry. We observed an increase in proteins associated with cell adhesion on the surface of NT-SS316L compared to that of SS316L, supporting literature reports of enhanced adhesion on nanotextured materials. For delivery to adherent cells, a "hard corona" of model biomacromolecule cargoes including superfolder green fluorescent protein (sfGFP) charge variants, cytochrome c, and siRNA was adsorbed on NT-SS316L to assess delivery. Nanotextured surfaces enhanced cellular biomacromolecule uptake and delivered cytosolic-functional proteins and nucleic acids through energy-dependent endocytosis. Collectively, these findings indicate that NT-SS316L holds potential as a surface modification for implants to achieve localized drug delivery for a variety of biomedical applications.

Capillary rise on rounded polygon corners of pillar and array structures

Capillary rise, where liquid climbs narrow spaces against gravity, plays an important role in both natural and technological processes. This study investigates capillary wetting in rounded polygon corners, a less-studied area in microfluid mechanics with significant implications for industries such as nanotextured surface cleaning, micro-soldering, food technology, and water harvesting. Through experimental analysis, we examine the relationship between capillary rise height and the geometric parameters of curvature radius and angle in rounded polygonal pillar and array structures. Our findings reveal a direct correlation where the capillary rise height increases as the radius of the corner increases, emphasizing the critical role of corner geometry in enhancing capillary action. This research not only deepens understanding of capillary behavior in complex geometries but also provides valuable insights for optimizing capillary-based applications across. By considering the influence of geometric complexity on capillarity, our study paves the way for innovative approaches in the design and development of efficient systems for fluid manipulation and control.

IR Hidden Patterns for Security Labels.

Authentication of a product's originality by anticounterfeiting labels represents a crucial point toward protection against forgery. Fast and scalable fabrication methods of original labels with a high degree of protection are in high demand for the protection of valuable goods. Here, we propose a simple strategy for fabrication of hidden security tags with IR luminescent readout by the direct femtosecond laser patterning of silicon-erbium-silicon sandwiched thin films. The choice of laser processing parameters makes possible the creation of random or quasi-regular self-organized surface nanotextures. The controlled laser-driven oxidation accompanying this process provides simultaneous regulation of the film's optical properties and spontaneous emission yield of the embedded Er atoms. The regimes are detected when optically similar patterned areas demonstrate different Er emission intensities, allowing us to create hidden security tags with facile readout at the C-band telecommunication wavelengths. The obtained results take another step toward the application of IR-luminescent erbium-based anticounterfeiting labels for covert and/or forensic security levels.

Anisotropic Stick-Slip Frictional Surfaces via Titania Nanorod Patterning.

Nanoscale or microscale surface texturing is an effective technique to tailor the tribological properties between two surfaces that are rubbed against each other. In order to achieve the desired frictional properties by a patterned surface, one needs an in-depth understanding of the underlying mechanisms. Here, we demonstrate anisotropic stick-slip friction achieved via a nanotextured surface of tilted titania nanorods (TiNRs). The surface was developed by using the glancing angle deposition (GLAD) technique, and exhibited load-dependent variations in stick-slip friction as well as frictional anisotropy in different sliding directions. For studying the frictional properties of the newly developed surface, lateral force microscopy (LFM) was performed in three different reciprocal orientations (0° rotated, 45° rotated, 90° rotated) using a custom-made colloidal alumina atomic force microscopy (AFM) probe. The frictional behavior was found to vary significantly with the orientation. At 0° rotated position) a prominent "stick-slip" was observed when scanning opposite to the tilt direction, whereas the phenomenon reduced significantly when the nanotextured surface was scanned along the tilt direction or rotated to different angles (45 and 90°) with respect to the sliding direction of the AFM cantilever supporting the probe. The experimental findings were interpreted based on the classical solution for large deflections of tilted elastic rods. Overall, the textured surface, LFM-based frictional measurement, and the quantitative analysis presented here provide a fundamental understanding of how friction can be significantly varied on a surface patterned with tilted TiNRs at a length scale of about 1 μm, which can be comprehensively applied to nanorod patterns of other materials on different substrates.

Experimental Studies of Bioinspired Shark Denticles for Drag Reduction.

Shark skin is composed of denticles, or complex scale-like features, which have been shown to reduce drag in turbulent and laminar flow. The denticle crown features undulating structures called riblets that interact with the turbulent boundary layer to reduce drag. Two mechanisms thought to contribute to the drag-reducing properties of riblets include the lifting of streamwise vortices and the hampering of spanwise vortex interactions to reduce crossflow, which could translate to similar flow mechanisms for denticles. Because of the varied morphologies of dermal denticles on different shark species, which also depend on body location, the impact of these denticle geometries on flow is of interest to the biology community, including related fields such as fluid mechanics and oceanography. This review highlights the past 15 years of manufacturing techniques and experimental measurements of drag over denticle-inspired surface structures, including real shark skin samples and engineered denticles and riblets. State-of-the-art additive manufacturing and other techniques are primarily limited to mm-length denticle scales, which have demonstrated drag reduction in lower flow speeds, under 1 m s-1. New manufacturing approaches can create sub-mm length denticles and nanotextured surface structures, which have achieved reported drag reductions of up to 31%. We synthesize results from the literature to illustrate the drag reduction properties of bioinspired denticles and riblets according to their geometry and flow conditions. Using these trends, we suggest design features and focus areas for future research, such as increasing studies of different denticle morphologies, hydrophobicity, antifouling properties, and acoustic noise reduction. Continued work on bioinspired denticles for drag reduction has wider implications in comparative biology and applications to design more energy-efficient, persistent vehicles for environmental monitoring.

Direct formation of copper nanoparticles from atoms at graphitic step edges lowers overpotential and improves selectivity of electrocatalytic CO2 reduction

A key strategy for minimizing our reliance on precious metals is to increase the fraction of surface atoms and improve the metal-support interface. In this work, we employ a solvent/ligand/counterion-free method to deposit copper in the atomic form directly onto a nanotextured surface of graphitized carbon nanofibers (GNFs). Our results demonstrate that under these conditions, copper atoms coalesce into nanoparticles securely anchored to the graphitic step edges, limiting their growth to 2–5 nm. The resultant hybrid Cu/GNF material displays high selectivity in the CO2 reduction reaction (CO2RR) for formate production with a faradaic efficiency of ~94% at -0.38 V vs RHE and a high turnover frequency of 2.78 × 106 h-1. The Cu nanoparticles adhered to the graphitic step edges significantly enhance electron transfer to CO2. Long-term CO2RR tests coupled with atomic-scale elucidation of changes in Cu/GNF reveal nanoparticles coarsening, and a simultaneous increase in the fraction of single Cu atoms. These changes in the catalyst structure make the onset of the CO2 reduction potential more negative, leading to less formate production at -0.38 V vs RHE, correlating with a less efficient competition of CO2 with H2O for adsorption on single Cu atoms on the graphitic surfaces, revealed by density functional theory calculations.

Optimizing alkaline hydrothermal treatment for biomimetic smart metallic orthopedic and dental implants

Orthopedic and dental implant failure continues to be a significant concern due to localized bacterial infections. Previous studies have attempted to improve implant surfaces by modifying their texture and roughness or coating them with antibiotics to enhance antibacterial properties for implant longevity. However, these approaches have demonstrated limited effectiveness. In this study, we attempted to engineer the titanium (Ti) alloy surface biomimetically at the nanometer scale, inspired by the cicada wing nanostructure using alkaline hydrothermal treatment (AHT) to simultaneously confer antibacterial properties and support the adhesion and proliferation of mammalian cells. The two modified Ti surfaces were developed using a 4 h and 8 h AHT process in 1 N NaOH at 230 °C, followed by a 2-hour post-calcination at 600 °C. We found that the control plates showed a relatively smooth surface, while the treatment groups (4 h & 8 h AHT) displayed nanoflower structures containing randomly distributed nano-spikes. The results demonstrated a statistically significant decrease in the contact angle of the treatment groups, which increased wettability characteristics. The 8 h AHT group exhibited the highest wettability and significant increase in roughness 0.72 ± 0.08 µm (P < 0.05), leading to more osteoblast cell attachment, reduced cytotoxicity effects, and enhanced relative survivability. The alkaline phosphatase activity measured in all different groups indicated that the 8 h AHT group exhibited the highest activity, suggesting that the surface roughness and wettability of the treatment groups may have facilitated cell adhesion and attachment and subsequently increased secretion of extracellular matrix. Overall, the findings indicate that biomimetic nanotextured surfaces created by the AHT process have the potential to be translated as implant coatings to enhance bone regeneration and implant integration.Graphical

Facile fabrication of hierarchical micro/nano aluminum alloy surfaces with enhanced hydrophobicity and surface quality by single point diamond cutting under a magnetic field influence

This study proposes an effective fabrication method for creating a hierarchical micro/nano structured aluminum alloy surface to enhance its hydrophobicity through single point diamond cutting using magnetophoresis. Magnetophoresis is a technique that manipulates metallic particles in metallic fluids using magnetic fields, and this study applies it to single-point diamond cutting by incorporating permanent magnets into the machining setup. The main grooves are cut to create a nano-grooved pattern on the first layer of the surface, while secondary grooves are cut on top of the first layer to form a micro pattern on the surface for two samples, one with and one without magnetophoresis. For magnetophoresis-fabricated samples, the first and second layers are cut in the presence of a magnetic field that is oriented perpendicular to the cutting direction of the first layer. Atomic force microscopy and an optical surface profiler reveal that the metallic marks appear on the surfaces that are parallel to the applied magnetic field for the magnetophoresis sample, which have been integrated with nano grooves to form a nano-textured surface on top of the microstructures. The sample fabricated under the influence of a magnetic field with magnetophoresis exhibits improved surface hydrophobicity, quality, and durability. This study highlights that magnetophoresis has the potential to fabricate metallic hydrophobic surfaces more efficiently than traditional methods for hierarchical micro/nano structured metallic surfaces, given that it does not necessitate the use of complex machining systems or advanced equipment.

FORMATION OF NANOCONES AND GENERATION OF NEGATIVE POTENTIAL ON STAINLESS STEEL SURFACES BY ELECTROCHEMICAL ETCHING SYNERGISTICALLY REDUCE PSEUDOMONAS AERUGINOSA'S BIOFILM

Hospital-acquired infections cause severe patient problems because of the augmented appearance of antibiotic-resistant bacteria, including Pseudomonas aeruginosa. Material surfaces modified with several biophysical parameters can decrease bacterial biofilm formation, which could be an advantageous alternative to treatment with antibiotics. Since stainless steel is an extensively used material for manufacturing medical implants and in healthcare settings, in this study, we used stainless steel (SS 316L and SS 304) to examine the result of the material surface topographies on bacterial biofilm establishment. This work used the electrochemical etching method to modify the stainless steel surface topography as an anode. The electrochemical etching method influenced the nanocones’ formation on stainless steel surfaces of both SS316L (Disk-6: 2682 peaks/[Formula: see text]m[Formula: see text] and SS304 (Disk-12: 1654 peaks/[Formula: see text]m[Formula: see text] estimated by atomic force microscopy and 3D Profilometer reduced the biofilm by 78% and 85%, respectively. Additionally, the higher negative potential on an average of 600[Formula: see text]mV measured by Kelvin probe atomic force microscopy reduced the biofilm formation on both SS316L and SS304 surface synergistically compared to the non-electrochemically etched surface. Biofilm growth and nanopotrusions on the stainless-steel surface examined by atomic force microscopy and scanning electron microscopy demonstrated significantly dead bacterial cells (20%) on the electrochemically etched surface than on the non-electrochemically etched surface after 2[Formula: see text]h contact time. Our observations exhibit that the nanotextured surface topographies and surface negative potential effectively inhibit bacterial adhesion and biofilm formation.

Liquid‐Assisted Laser Nanotexturing of Silicon: Onset of Hydrodynamic Processes Regulated by Laser‐Induced Periodic Surface Structures

AbstractUpon systematic studies of femtosecond‐laser processing of monocrystalline Si in oxidation‐preventing methanol, it is shown that the electromagnetic processes dominating at initial steps of the progressive morphology evolution define the onset of the hydrodynamic processes and morphology upon subsequent multi‐pulse exposure. Under promoted exposure quasi‐regular subwavelength laser‐induced periodic surface structures (LIPSSs) are justified to evolve through the template‐assisted development of the Rayleigh‐Plateau hydrodynamic instability in the molten ridges forming quasi‐regular patterns with a supra‐wavelength periodicity and preferential alignment along polarization direction of the incident light. Subsequent exposure promotes fusion‐assisted morphology rearrangement resulting in a spiky surface with random orientation, yet constant inter‐structure distance correlated with initial LIPSS periodicity. Along with the insight onto the physical picture driving the morphology evolution and supra‐wavelength nanostructure formation, this experiments also demonstrated that resulting quasi‐regular and random spiky morphology can be tailored by the intensity/polarization distribution of incident laser beam allowing on‐demand surface nanotexturing with diverse hierarchical surface morphologies exhibiting reduced reflectivity at visible and shortwave‐IR wavelengths. Finally, the practical attractiveness of the suggested approach for improving near‐IR photoresponse and expanding operation spectral range of vertical p‐n junction Si photodetector operating under room temperature and zero‐bias conditions via single‐step annealing‐free nanopatterning is highlighted.

Design of Abrasion-Resistant, Long-Lasting Antifog Coatings.

Fog formation is a common challenge for numerous applications, such as food packaging, mirrors, building windows, and freezer/refrigerator doors. Most notably, fog forms on the inner surfaces of prescription glasses and safety eyewear (particularly when used with a mask), face shields, and helmet lenses. Fogging is caused by the distortion of light from condensed water droplets present on a surface and can typically be prevented if the surface static water contact angle (θ) is less than ∼40°. Such a low contact angle can be readily achieved by either increasing the substrate surface energy or by engineering surface nanotexture. Unfortunately, such nanotexture can be readily damaged with use, while high surface energy substrates get covered with low surface energy foulants over time. Consequently, even with numerous ephemeral antifog coatings, currently there are no commercially available, durable, and permanent antifog coatings. Here we discuss the development of a new class of high-performance antifog coatings that are abrasion-resistant and long-lasting. These polyvinylpyrrolidone-based coatings, designed based on the classical Ratner-Lancaster wear model, dramatically outperform the base polymer, as well as all tested commercially available antifog coatings. Specifically, these coatings exhibit a > 400% increase in fogging time compared to base polymer, a > 50,000% increase in wear resistance, and excellent long-term antifog performance. The developed coatings also significantly outperformed all tested commercially available antifog coatings in terms of their antifog performance, wear resistance, and long-term cyclical performance. Additionally, the key design strategies employed here─incorporation of toughening agents and hydrophilic slip additives─offer a new approach to developing high-performance, durable antifog coatings based on other well-known antifog polymers.

Teflon AF–Coated Nanotextured Aluminum Surfaces for Jumping Droplet Thermal Rectification

AbstractJumping droplet thermal diodes (JDTDs) are promising candidates to achieve thermal rectification for next‐generation thermal control. However, most prior demonstrations of JDTDs have relied on monolayer‐coated copper‐based superhydrophobic (SHPB) surfaces, while lower‐cost aluminum JDTDs with more durable thin polymeric coatings have not been explored. In this work, a JDTD is constructed that employs SHPB aluminum surfaces coated with protective thin films of Teflon AF (amorphous fluoropolymer) 1601. Measurements for different heating orientations, gap heights (H), and fill ratios (ϕ) show that a maximum thermal rectification ratio of 7 can be achieved for H = 2.4 mm and ϕ = 10%. A thermal circuit is demonstrated that uses the JDTD to rectify time‐periodic temperature profiles, achieving thermal circuit effectiveness values up to 30% of the ideal‐diode limit. Coupon‐level durability tests and device‐level cycling show that dip coated Teflon AF enables stable operation of Al JDTDs over &gt;20 cycles, improving on the performance of a monolayer‐coated surface that fails after 5 cycles. The findings of this work signify that Teflon AF coated Al SHPB surfaces can be used for thermal rectification and motivate future research into Al JDTDs for advanced thermal management applications.

Bioinspired, Bioactive, and Bactericidal: Anodized Nanotextured Dental Implants

AbstractBioinspired titanium implant nanotexturing achieved via advanced techniques such as lithography, hydrothermal and laser patterning enables modulation of cell functions toward enhanced bioactivity and antibacterial efficacy. However, such costly, multi‐step methods limit clinical translation and benchtop implant modification. For the first time, single‐step, cost‐effective, and translatable electrochemical anodization is reported to fabricate bioinspired nanopillar‐like textures on micro‐rough titanium. In‐depth surface characterization confirms the formation of novel nanostructures, namely nanoscale Spinules, Daggers, Papillae, Spikes, and Flames, exhibiting varied roughness and wettability. Next, in separate experiments, primary human osteoblasts and polymicrobial salivary biofilm are cultured on the implant substrates. Nanotextured surfaces show high protein adhesion and maintain the proliferation, adhesion, and spreading of osteoblasts. Interestingly, all nanotextures exhibit superior antibiofilm abilities compared to control surfaces. Bioactive and antibacterial implant surface nano‐texturing achieved via single‐step anodization has the potential for clinical translation as the next generation of orthopedic and dental implant surface modification.

Two-dimensional periodic surface nanotexturing of 6H-SiC by ultrashort laser pulses

Circularly polarized femtosecond laser pulses have successfully promoted the formation of Two-Dimensional Laser Induced Periodic Surface Structures (2D-LIPSS) exhibiting a sub-wavelength periodicity of 150 ± 20 nm on semi-insulating 6H-SiC samples. The main objective of this study was to discern the formation of two-dimensional LIPSS depending on the single pulse energy and the number of pulses released per unit area. The experimental laser system used in this study generates pulses with a duration of 100 fs, a wavelength of 800 nm, and operates at a repetition rate of 1 kHz.Micro-Raman spectroscopy confirms the presence of the characteristic 6H-SiC peaks across all irradiated samples, indicating that the processing technique does not induce significant compositional variations. Nonetheless, the analysis reveals the induction of compressive stress within the lattice structure.Samples treated across the entire surface were characterized by using optical analysis in order to assess the induced variations in absorptance and emittance due to laser irradiation. The treated samples exhibit solar absorptance values of approximately 75 % and a high spectral selectivity up to 2.0 for temperatures higher than 1000 K. This highlights the potential of fs-laser surface textured 6H-SiC plates as viable selective solar absorbers for energy conversion devices operating at elevated temperatures.

Visualization and Experimental Characterization of Wrapping Layer Using Planar Laser-Induced Fluorescence.

Droplets on nanotextured oil-impregnated surfaces have high mobility due to record-low contact angle hysteresis (∼1-3°), attributed to the absence of solid-liquid contact. Past studies have utilized the ultralow droplet adhesion on these surfaces to improve condensation, reduce hydrodynamic drag, and inhibit biofouling. Despite their promising utility, oil-impregnated surfaces are not fully embraced by industry because of the concern for lubricant depletion, the source of which has not been adequately studied. Here, we use planar laser-induced fluorescence (PLIF) to not only visualize the oil layer encapsulating the droplet (aka wrapping layer) but also measure its thickness since the wrapping layer contributes to lubricant depletion. Our PLIF visualization and experiments show that (a) due to the imbalance of interfacial forces at the three-phase contact line, silicone oil forms a wrapping layer on the outer surface of water droplets, (b) the thickness of the wrapping layer is nonuniform both in space and time, and (c) the time-average thickness of the wrapping layer is ∼50 ± 10 nm, a result that compares favorably with our scaling analysis (∼50 nm), which balances the curvature-induced capillary force with the intermolecular van der Waals forces. Our experiments show that, unlike silicone oil, mineral oil does not form a wrapping layer, an observation that can be exploited to mitigate oil depletion of nanotextured oil-impregnated surfaces. Besides advancing our mechanistic understanding of the wrapping oil layer dynamics, the insights gained from this work can be used to quantify the lubricant depletion rate by pendant droplets in dropwise condensation and water harvesting.

Mechanical Abrasion of Laser‐Machined Highly Hydrophobic Stainless Steel Surface Depending on Surface Topography

Stainless steel (SST) is an important material for a variety of applications including construction, food, and medical. Highly hydrophobic wetting properties enhance the surface properties of SST to support processes such as self‐cleaning . However, applications also require long‐term stability of such properties against chemical and mechanical influences from the environment or technical processes. Therefore, the reduction of highly hydrophobicity of chemically modified, laser‐textured SST surfaces is investigated in relation to abrasive wear using hierarchical structures, micro‐/nanotextured surface, and support structures that shield the highly hydrophobic pattern. Surface textures comprising ridges, grooves (size: 50–500 μm; depth: up to 100 μm), and a nanostructured grooves bottom are machined by infrared ultrashort pulse laser ablation into SST and are subsequently chemically modified by a self‐assembled monolayer of a fluorinated, phosphonic acid‐modified alkane. Abrasive wear tests of these surfaces show decreasing water contact angles with increasing wear of the modified surface of the support structures. However, there is good stability of the highly hydrophobic properties due to the protection of modified areas at the groove bottom. The proposed wetting model for such designed functionalized laser textures shows possibilities for further optimization of such robust highly hydrophobic surfaces and adaptation to specific applications.

Creating a New Inframammary Fold, Raising the Breast Footprint and Elongating the Torso with Multiplane Concept.

Augmentation mastopexy focus on restoring the youthful appearance of the female breast. Despite those benefits, there is large scarring to be considered, and the reduction of this side effect is the main goal to enhance the aesthetic result. This article aims to describe a variation of the L-shaped mastopexy technique without complex marking and performed in planes, which brings long-term results for patients undergoing this approach. This is a retrospective, observational study, based on a series of cases conducted by the author. The preoperative appointment and the surgical technique are described, and divided into steps according to their components: cutaneous, glandular tissue, and muscular. Between January 2016 and July 2021, 632 women underwent surgery. The mean age was 38 years (18-71 years). The mean volume of implants was 285cc (175-550cc). All the implants used were round with a nanotextured surface. The mean tissue resected from each breast was 117g (5-550g). Follow-ups ranged from 12 to 84 months, and photographic documentation was performed from 30 days after surgery. Complications totaled 19.30% and were divided into minor - treated with expectant treatment, non-invasive or with the possibility of correction with local anesthesia, corresponding to 10.44%; and major - in which it was necessary to return to the operating room, corresponding to 8.86%. Multiplane L-Scar Mastopexy is a versatile and safe technique with predictable results, which allows the systematic treatment of the most diverse breast types, with complications similar to other already described and solidified techniques.

Fluid dynamics simulation on water lubricating performance of micro-/nano-textured surfaces considering roughness structures

With the development of surface precision machining technology and extensive studies on lubrication and friction reduction, the use of surface texture to reduce friction has attracted widespread attention, but few studies have considered the influence of surface roughness on lubrication characteristics. By employing the computational fluid dynamics (CFD) simulation method, the lubrication models with rectangular textures and the introduction of rough asperity structures at the same time are established. The effects of the corresponding structure parameters on the lubrication performance of textured and roughed surfaces are studied under water lubrication conditions. Our results suggest that the adjustment of geometric parameters on the micro-/nano-structured surfaces can influence the load-bearing capacity of the water lubrication film, thus affecting the hydrodynamic lubrication performance on the surface. In addition, the generation of vortex in the micro-textures can bring changes in vorticity, which causes energy dissipation and affects frictional forces. In the lubrication model with rectangular textures, optimal hydrodynamic lubrication performance is obtained under the appropriate depth ratio &lt;i&gt;H&lt;/i&gt; = 0.6. Meanwhile, the corresponding lubrication performance can be enhanced by increasing the width ratio (&lt;i&gt;W&lt;/i&gt;) of surface texture. After introducing random asperity structures on the micro-textured surface with a standard deviation &lt;i&gt;δ&lt;/i&gt; = 0.5, the bearing capacity is increased by 44%, and the friction coefficient is reduced by 30.9%. Moreover, the introduction of half-sine rough asperity structures can only result in relatively minor differences in the lubrication performance, i.e. the changes of bearing capacity and friction coefficient are less than 10%. However, the introduction of compound hierarchical structure consisting of random asperity structures and half-sine rough asperity structures can result in an increase in the corresponding bearing capacity by 42% and a reduction in the friction coefficient by 31.1%, which implies a significant enhancement in the hydrodynamic lubrication performance.

From scrap metal to highly efficient electrodes: harnessing the nanotextured surface of swarf for effective utilisation of Pt and Co for hydrogen production

Atomically deposited Pt and Co on nano-grooves result in active and stable electrocatalysts for hydrogen evolution and oxygen evolution reactions.

Metal Surface Engineering for Extreme Sustenance of Jumping Droplet Condensation.

Water vapor condensation on metallic surfaces is critical to a broad range of applications, ranging from power generation to the chemical and pharmaceutical industries. Enhancing simultaneously the heat transfer efficiency, scalability, and durability of a condenser surface remains a persistent challenge. Coalescence-induced condensing droplet jumping is a capillarity-driven mechanism of self-ejection of microscopic condensate droplets from a surface. This mechanism is highly desired due to the fact that it continuously frees up the surface for new condensate to form directly on the surface, enhancing heat transfer without requiring the presence of the gravitational field. However, this condensate ejection mechanism typically requires the fabrication of surface nanotextures coated by an ultrathin (<10 nm) conformal hydrophobic coating (hydrophobic self-assembled monolayers such as silanes), which results in poor durability. Here, we present a scalable approach for the fabrication of a hierarchically structured superhydrophobic surface on aluminum substrates, which is able to withstand adverse conditions characterized by condensation of superheated steam shear flow at pressure and temperature up to ≈1.42 bar and ≈111 °C, respectively, and velocities in the range ≈3-9 m/s. The synergetic function of micro- and nanotextures, combined with a chemically grafted, robust ultrathin (≈4.0 nm) poly-1H,1H,2H,2H-perfluorodecyl acrylate (pPFDA) coating, which is 1 order of magnitude thinner than the current state of the art, allows the sustenance of long-term coalescence-induced condensate jumping drop condensation for at least 72 h. This yields unprecedented, up to an order of magnitude higher heat transfer coefficients compared to filmwise condensation under the same conditions and significantly outperforms the current state of the art in terms of both durability and performance establishing a new milestone.