Nanoporous Layer Research Articles

Synergistic effects of calcium and zinc on bio-functionalized 3D Ti cancellous bone scaffold with enhanced osseointegration capacity in rabbit model

The present research aims to develop a Ca-Zn ion-incorporated surface functionalized 3D Ti cancellous bone scaffold for bone defect repair. The scaffold is designed to mimic human cancellous bone architecture through selective laser melting-based additive manufacturing. The chemical-based surface modification approach employed here created a Ca and Zn ions incorporated nano-porous surface layer with enhanced surface roughness and hydrophilicity. The modified biomimetic scaffold improved corrosion resistance behaviour with ICORR and ECORR values of 0.174 and 0.0097 respectively. It is learned that incorporating Zn as ZnO over the scaffold has antibacterial activity against Staphylococcus aureus and Escherichia coli. The cellular response of MG-63 to the modified scaffold was evaluated through in-vitro studies which focus on the cytocompatible properties. The intra-osseous biomimetic Ti-Na-Ca:Zn 3D scaffold revealed significant improvement in the osseointegration capabilities in terms of bone mineral density (BMD) and bone volume/total volume (BV/TV) in the rabbit model. The osseointegration potential at the Ti-Na-Ca:Zn interface was evidenced by histological analysis and micro-CT imaging. In addition to this, the remarkable upregulation of osteogenic genes such as OCN, COL1A1, OPN, ALP, RUNX2, and OSX evidences the dynamics of the osseointegration process at each surgical period. This Ca and Zn surface functionalised porous architecture of the 3D Ti cancellous bone scaffold similar to bone with enhanced biological response and bone integration can potentially allow implant customisation by utilizing additive manufacturing technology with improved clinical outcomes.

Research on corrosion behavior and biocompatibility of NiTi alloy processed with combined dealloying and annealing treatment

This paper presents a novel method to prepare hydrophilic nanoporous functional surface with combined dealloying and annealing treatment to improve the corrosion resistance and biocompatibility of NiTi components. Surface modification mechanism is discussed with microscopic characterization of NiTi nanoporous structures. Hydrophilic and biocompatible performance is achieved through specifically tailoring the dimensions and chemical compositions of nanoporous layer. The corrosion resistance of NiTi samples is investigated in 0.9 wt% NaCl solution and evaluated with potentiodynamic polarization and electrochemical impedance spectroscopy tests. The results indicate that material corrosion resistance is significantly enhanced with TiO2 formation during dealloying treatment, while annealing promotes the oxidation and densification of dealloyed layer raising the energy barrier for ion transportation during corrosion. Furthermore, as the dealloying temperature increases, the surface defects of the sample decrease resulting in better corrosion resistance. The research can provide guidance for NiTi surface modification to enhance its biomedical applications.

Mechanism of Anodic Dissolution of Tungsten in Sulfate–Fluoride Solutions

Thin passive films on tungsten play an important role during the surface levelling of the metal for various applications and during the initial stages of electrochemical synthesis of thick, nanoporous layers that perform well as photo-absorbers and photo-catalysts for light-assisted water splitting. In the present work, the passivation of tungsten featuring metal dissolution and thin oxide film formation is studied by a combination of in situ electrochemical (voltammetry and impedance spectroscopy) and spectro-electrochemical methods coupled with ex situ surface oxide characterization by XPS. Voltametric and impedance data are successfully reproduced by a kinetic model featuring oxide growth and dissolution coupled with the recombination of point defects, as well as a multistep tungsten dissolution reaction at the oxide/electrolyte interface. The model is in good agreement with the spectro-electrochemical data on soluble oxidation products and the surface chemical composition of the passive oxide.

The design of nano-porous photocatalytic intermediate layer to fabricate the copper layer on AlN ceramic with high bonding strength through the interlocking microstructure

AlN ceramic is the potential substrate for high-performance printed circuit board with the rapid development of electronic industry due to the superior thermal and electrical property, while its metallization still faces the issues of thermal stress and weak interface bonding with existing technology. Herein, a convenient design is proposed to achieve the Cu deposition on the surface of AlN substrate, the TiO2 containing photocatalytic intermediate layer is prefabricated on AlN substrate with silica and titania mixed sol, and induces the autocatalytic deposition of electroless copper plating under ultraviolet irradiation. Compared with Cu deposition with Pd activation treatment, the bonding strength between Cu layer and AlN substrate is significantly enhanced with the intermediate layer, this is ascribed to the formed nano-porous microstructure of the sintered intermediate layer facilitating the penetration of plating bath, and the mechanical anchoring effect derived from the interlocking microstructure between Cu layer and intermediate layer contributes to the improved bonding strength. This new method realizes the metallization of AlN ceramic with high interfacial bonding strength and low cost compared with the traditional joining technology, and provides a potential reference for the surface metallization of inert material.

Surface Engineering of Anodic WO3 Layers by In Situ Doping for Light-Assisted Water Splitting.

This study presents a novel approach to fabricating anodic Co-F-WO3 layers via a single-step electrochemical synthesis, utilizing cobalt fluoride as a dopant source in the electrolyte. The proposed in situ doping technique capitalizes on the high electronegativity of fluorine, ensuring the stability of CoF2 throughout the synthesis process. The nanoporous layer formation, resulting from anodic oxide dissolution in the presence of fluoride ions, is expected to facilitate the effective incorporation of cobalt compounds into the film. The research explores the impact of dopant concentration in the electrolyte, conducting a comprehensive characterization of the resulting materials, including morphology, composition, optical, electrochemical, and photoelectrochemical properties. The successful doping of WO3 was confirmed by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, photoluminescence measurements, X-ray photoelectron spectroscopy (XPS), and Mott-Schottky analysis. Optical studies reveal lower absorption in Co-doped materials, with a slight shift in band gap energies. Photoelectrochemical (PEC) analysis demonstrates improved PEC activity for Co-doped layers, with the observed shift in photocurrent onset potential attributed to both cobalt and fluoride ions catalytic effects. The study includes an in-depth discussion of the observed phenomena and their implications for applications in solar water splitting, emphasizing the potential of the anodic Co-F-WO3 layers as efficient photoelectrodes. In addition, the research presents a comprehensive exploration of the electrochemical synthesis and characterization of anodic Co-F-WO3, emphasizing their photocatalytic properties for the oxygen evolution reaction (OER). It was found that Co-doped WO3 materials exhibited higher PEC activity, with a maximum 5-fold enhancement compared to pristine materials. Furthermore, the studies demonstrated that these photoanodes can be effectively reused for PEC water-splitting experiments.

SYNTHESIS AND CHARACTERISTICS OF ZnS NANOWIRES

The creation of a nanoporous silicon dioxide layer in the a-SiO2/Si-n structure was accomplished by irradiation with xenon ions at a cyclotron and then chemical etching with an aqueous solution of hydrogen fluoride with the addition of palladium. The truncated cone-shaped nanopores had diameters ranging from 486 to 509 nm. Then ZnS nanowires synthesized by electrochemical deposition (ECD) method, depending on the voltage at the electrodes of the electrolytic cell and as a result zinc sulfide nanowires with cubic structure and spatial symmetry group F-43m (216) were obtained. The sample is characterized by (111), (200), (220), (331) (311) planes, respectively, which is in good agreement with the cubic phase of ZnS. The charge-voltage characteristics (CVC) of ZnS showed that an n-type conductivity semiconductor was formed. Measurements of the photoluminescence (PL) spectra of ZnS were recorded on a CM 2203 spectrofluorimeter. The PL spectra were recorded in the range of 250 nm to 450 nm at room temperature. The PL spectra of the precipitated precipitates reveals emission in a wide UV-visible spectral range. It can be seen that the luminescence spectra have quite complex components and can be divided into five Gaussian curves. As can be seen the FL spectrum of the deposited ZnS consists of bands at 3.15 eV, 3.3 eV, 3.4 eV, 3.55 eV and 3.73 eV. Also analyzing the spectra energy dispersive analysis showed that the ZnS nanoproofs consist of Zn – 42.5% and S – 57.5%.

Interfacial design of support substrate for a continuous mesophase-templated active layer with adjustable pore size

Nano-porous active layers templated by hexagonal lyotropic liquid crystal (HLLC) offer a continuous water pathway, rendering them promising for membrane separation applications of high performance. The surface properties, such as surface roughness, hydrophilicity and pore size, of commercially available ultrafiltration membranes usually need to be optimized to better support the active layer. Here, we apply a facile yet potent thermal treatment process to a polyacrylonitrile ultrafiltration (UPAN) substrate and form a continuous HLLC separation layer. The enhancement in water filtration performance is largely influenced by the surface roughness of the substrates. As the temperature increases, the UPAN substrates become rougher due to approaching the glass transition temperature of polyacrylonitrile. This leads to a denser HLLC active layer with smaller pores. For the membranes treated at a temperature of 100 °C, their water flux reaches 17 L/m2h, which is 10 times higher than that of the membranes treated at 85 °C, and the PEG4000 rejection increases by almost 50 % from 42 % to 59 %. This heat treatment process offers a novel approach to fabricate mesophase-templated active layers with adjustable pore sizes, thus advancing membrane separation techniques.

Nanosecond laser-induced crystallization of SiOx/Au bilayers in air and vacuum

High-quality polycrystalline silicon films on low-cost and low-temperature substrates have attracted much attention as promising materials for high-speed thin-film transistors and thin-film solar cells fabrication. To obtain poly-Si films on low temperature substrates, several concepts have been proposed. Usually the amorphous material undergoes crystallization which can be achieved by various methods including solid-phase crystallization, metal-induced crystallization or liquid-phase crystallization. In this work, we tried to combine the advantages of metal-induced crystallization and liquid-phase crystallization. To achieve this we explored the nanosecond laser crystallization of a bilayer structure consisting of Au and SiO0.1 layers with thicknesses of 30 nm and 130 nm, respectively. The study reveals that when exposed to 532 nm wavelength radiation leads to its destruction due to rupture. On the other hand, when subjected to 1064 nm wavelength radiation, no similar material behavior is observed, and the measured modification threshold is 0.15 J/cm2, representing a 40 % reduction compared to SiO0.1 film without gold. It is demonstrated that at laser fluences of 0.35 J/cm2 and higher, the treatedsurfaceinair becomes enriched with silicon dioxidenanoporous coating, attributed to the return of evaporation products to the target surface. Theoretical modeling, assuming thermal evaporation of the coating, suggests that the undesirable nanoporous layer formation can be avoided.

Corrosion inhibition of stainless steel through the formation of hydrophobic nanoporous oxide layer

This study investigates anti-corrosion properties of anodized and hydrophobically modified anodized SUS 304 stainless steel (SS 304). Utilizing electrochemical anodization and subsequent annealing, a well-ordered hexagonally closed-packed nanoporous oxide layer on the SS 304 surface, designated as AAS, was successfully developed. Then, a self-assembled monolayer of silane molecules, namely, octadecyltrimethoxysilane (ODTS) and 1 H,1 H,2 H,2 H-perfluorooctyltriethoxysilane (PFTS), was formed on the nanoporous oxide layer of annealed-anodized SS 304. The FTIR study confirmed the formation of the self-assembly of silane molecules on nanoporous oxide surface. The self-assembled monolayers exhibited hydrophobic surface where hydrophobicity increases with increase of silane molecule concentration and gives a water contact angles measure of 127.60° and ∼ 128.83° for 0.50 wt% ODTS and 0.50 wt% PFTS, respectively. The potentiodynamic polarization study revealed a corrosion rate of 1.485 × 10−3 mm year−1 for AAS, 0.614 × 10−3 mm year−1 for 0.50 wt% ODTS-AAS, and 0.348 × 10−3 mm year−1 for 0.50 wt% PFTS-AAS. This represents a significant reduction in corrosion rate compared to bare stainless steel (4.385 × 10−3 mm year−1) when exposed to a simulated sea water environment. The AAS, 0.50 wt% ODTS-AAS and 0.50 wt% PFTS-AAS exhibited corrosion inhibition efficiency of 66.13 %, 85.97 % and 92.06 %, respectively. Electrochemical impedance analysis revealed that PFTS exhibits roughly double the effective charge transfer resistance of ODTS and 7.4 times higher than that of annealed anodized stainless steel, confirming superior corrosion inhibition capability. Overall, this research illuminates the mechanism behind self-assembled monolayer formation, resulting in the development of hydrophobic surfaces and the inhibition of corrosion on nanoporous oxide layers on stainless steel surfaces.

Multifunctional tri-layer aramid nanofiber composite separators for high-energy-density lithium-sulfur batteries

Lithium-sulfur (Li-S) battery has attracted much attention due to their high theoretical energy density. However, severe shuttling effect, sluggish reaction kinetics and uncontrolled dendrite formation of Li anode greatly deter their practical applications. Different to conventional separator engineering strategies that are always focused on surface coating of functional interlayer on commercial polyolefin separators, herein, we proposed a structural engineering tactic by rationally tuning the porous structure and composition of the p-aramid nanofiber (ANF) composite separator to address simultaneously the above problems. A two-step film-casting process combined with a phase inversion approach was developed to fabricate a multifunctional tri-layer ANF composite separator. This innovative separator was especially engineered to comprise a conductive and catalytic NiFe2O4 modified multi-walled carbon nanotubes/ANF layer for rapid and efficient conversion of lithium polysulfides, a microporous ANF layer for fast ion transport, and a dense nanoporous ANF layer for lithium dendrite inhibition. This tri-layer ANF-based separator possessed high porosity, excellent thermal stability, and superb electrolyte wettability. Batteries with the tri-layer ANF- based separator exhibited outstanding cyclic stability with high capacity of >3 mAh cm−2 at high sulfur loading (4 mg cm−2) and high current density (4 mA cm−2). This work opens up new opportunities for design of functional separators based on high performance polymers using the structural engineering strategy.

Influence of electrolytic plasma spatial distribution on nanoporous structure etching on 4H-SiC surface

Single-crystal SiC nanoporous structure has important applications in the field of micro electromechanical systems, chemical sensors and biomedical devices. However, SiC exhibits a strong chemical inertness due to the short interatomic distance and high binding energy, making it significantly challenging to fabricate nanoporous structure. Electrolytic plasma-assisted chemical etching (EPACE) based on electrochemical anodic oxidation and high-activity electrolytic plasma etching is an ideal method for SiC nanoporous structure etching. In which, the spatial distribution of electrolytic plasma has an important impact on EPACE performance, such as etching efficiency and stability. In order to analyze the impact mechanism, this paper studies EPACE in tool electrode mounting posture of vertical and horizontal types by visual observation, real-time recording of voltage-current waveforms during processing, and the morphology analysis of SiC nanoporous structure after etching. It can be found that in the vertical etching type, EPACE can proceed stably because the workpiece immersion depth is greater than the bubble accumulation thickness. However, in the horizontal etching type, bubbles accumulate seriously between the workpiece and the liquid surface, which may cause bubble cavitation and abnormal discharge, leading to damage to the etching surface. The etching current in the vertical etching type is about 1.3 times that of the horizontal etching type, indicating that the bubble mass transfer in the vertical etching type is faster and the etching impedance is smaller, which is beneficial to improve the etching efficiency and obtain a uniform nanoporous structure. Finally, a SiC nanoporous layer with a thickness of 10.6 μm was prepared at etching time t = 50 min in vertical etching type, and the etching efficiency was 212 nm/min. In addition, the prepared nanoporous structure (nanofiber) was connected to the SiC substrate, indicating that it has a good bonding strength.

Effects of dealloying surface modification on machinability improvement of NiTi alloy during micro-machining process

In this work, a novel dealloying assisted machining (DAM) method is proposed to modify the machinability of a typical high toughness NiTi alloy. The DAM method can produce nanoporous layer on workpiece surface through dealloying process. Under different cutting depths, micro-milling experiments are performed on workpieces with and without dealloying surface modification. The results indicate that the embrittlement effect of nanoporous layer induce ductile to brittle transition during material removal process leading to the fragmented chip formation. Consequently, the cutting force and temperature decrease by over 14% and 12%, respectively. Meanwhile, the tool wear is alleviated and the machined surface quality is improved. The proposed method can also provide guidance for micro machining of other difficult-to-machine materials.

Fabrication of reusable bioprotective nanofabric with passive nano-Ag/Joule thermal disinfection properties for real-time wireless fine biomotion and gesture sensing

The frequent outbreaks of new infectious diseases, with increased difficulty in prevention and control, have raised higher requirements for bio-protective smart textiles. However, current wearable sensing materials face challenges with thermal and humidity comfort, bioprotection, reusability, self-disinfection, and wireless real-time sensing ability. Herein, an ultralight and breathable sandwich-structured interlayer nanofiber composite consisting of two outer microporous layers of polyimide nanofibers embedded with AgNPs (Ag@PINFs) and one nanoporous conductive layer (＜100 nm) of carbon nanotubes (CNTs) have been demonstrated by in-situ reduction, electrospinning, and suction filtration to improve the triboelectric output performance and impart passive/active self-disinfection abilities to triboelectric nanogenerators (TENGs). The TENG was designed with a triple bio-protection function. This included a passive physical barrier effect, nano-Ag active disinfection, and active Joule-heat disinfection function, which ensures the reusability of TENG. As-prepared TENG possessed the following advantages: (i) good moisture-penetrability; (ii) good water and blood penetration resistance (≥17.2 kPa; ≥7kpa); (iii) improved triboelectric output performances (∼1.6 W/m2 at Ag content of 500 mg/kg); (iv) ultrahigh UV resistance (UPF＞6480); (v) high particle and wet/dry microbial filtration performance (PFE = 99.95%; wet microbial penetration time＞75 min; penetrated dry microbial: lg(cfu)=0); (vi) active bactericidal abilities with killing rates of ∼100% against E. Coli and S. aureus at Ag content of ≥ 70 mg/kg; (vii) high Joule heat self-disinfection efficiency with killing rates of 100% at applied voltage of ≥ 5 V; (viii) a wireless real-time sensing ability to distinguish fine biomotion such as swallowing, coughing, and normal speech and shouting, as well as recognizing hand gesture by developed two/four-channel wearable wireless monitoring system (∼18 g). The TENG has trinity performances including bio-protection, self-disinfection, and wireless fine biomotion and gesture sensing, which has potential applications in medical field.

Anodic Oxidation of 3D Printed Ti6Al4V Scaffold Surfaces: In Vitro Studies

This study focuses on the surface modification of Ti6Al4V scaffolds produced through additive manufacturing using the Powder-Bed Fusion Electron-Beam Melting (PBF-EB) technique. From our perspective, this technique has the potential to enhance implant osseointegration, involving the growth of a layer of titanium dioxide nanotubes (TiO2) on surfaces through anodic oxidation. Scaffolds with anodized surfaces were characterized, and the formation of a nanoporous and crystalline TiO2 layer was confirmed. The analysis of cell morphology revealed that cells adhered to the anodized surfaces through their filopodia, which led to proliferation during the initial hours. However, it was observed that the adhesion of Saos-2 cells was lower on anodized scaffolds compared to both built and chemically polished scaffolds throughout the cell culture period. The results obtained here suggest that while anodic oxidation is effective in achieving a nanoporous surface, cell adhesion and interaction were affected by the weak adhesion of cell filopodia to the surface. Thus, combining surface treatment techniques to create micro- and nanopores may be an effective alternative for achieving a favorable cellular response when the objective is to enhance the performance of porous titanium scaffolds in the short term.

Acid Treatments of Ti-Based Metallic Glasses for Improving Corrosion Resistance in Implant Applications

Ti-based bulk metallic glasses are promising materials for metallic bone implants, mainly due to their mechanical biofunctionality. A major drawback is their limited corrosion resistance, with high sensitivity to pitting. Thus, effective surface treatments for these alloys must be developed. This work investigates the electrochemical treatment feasibility of nitric acid (HNO3) solution for two bulk glass-forming alloys. The surface states obtained at different anodic potentials are characterized with electron microscopy and Auger electron spectroscopy. The corrosion behavior of the treated glassy alloys is analyzed via comparison to non-treated states in phosphate-buffered saline solution (PBS) at 37 °C. For the glassy Ti47Zr7.5Cu38Fe2.5Sn2Si1Ag2 alloy, the pre-treatment causes pseudo-dealloying, with a transformation from naturally passivated surfaces to Ti- and Zr-oxide nanoporous layers and Cu-species removal from the near-surface regions. This results in effective suppression of chloride-induced pitting in PBS. The glassy Ti40Zr10Cu34Pd14Sn2 alloy shows lower free corrosion activity in HNO3 and PBS due to Pd stabilizing its strong passivity. However, this alloy undergoes pitting under anodic conditions. Surface pre-treatment results in Cu depletion but causes enrichment of Pd species and non-homogeneous surface oxidation. Therefore, for this glassy alloy, pitting cannot be completely inhibited in PBS. Concluding, anodic treatments in HNO3 are more suitable for Pd-free glassy Ti-based alloys.

Low-threshold AlGaN-based deep ultraviolet laser enabled by a nanoporous cladding layer.

We demonstrated an AlGaN-based multiple-quantum-well (MQW) deep ultraviolet (DUV) laser at 278 nm using a nanoporous (NP) n-AlGaN as the bottom cladding layer grown on the sapphire substrate. The laser has a very-low-threshold optically pumped power density of 79 kW/cm2 at room temperature and a transverse electric (TE)-polarization-dominant emission. The high optical confinement factor of 9.12% benefiting from the low refractive index of the nanoporous n-AlGaN is the key to enable a low-threshold lasing. The I-V electrical measurement demonstrates that an ohmic contact can be still achieved in the NP n-AlGaN with a larger but acceptable resistance, which indicates it is compatible with electrically driven laser devices. Our work provides insights into the design and fabrication of low-threshold lasers emitting in the DUV regime.

High-Temperature Melt Stamping of Polymers Using Polymer/Nanoporous Gold Composite Stamps.

Parallel lithographic deposition of polymers onto counterpart substrates is a widely applied surface manufacturing operation. However, polymers may only be soluble in organic solvents or are insoluble at all. Solvent evaporation during stamping may trigger hardly controllable capillarity-driven flow processes or phase separation, and polymer solutions may spread on the counterpart substrates. Solvent-free stamping of melts prevents these drawbacks. Here, a stamp design for the deposition of melts is devised, which intrinsically circumvents ink depletion. The stamps' topographically patterned contact surfaces with protruding contact elements contacting the counterpart substrates consist of a nanoporous gold layer with a thickness of a few micrometers. The nanoporous gold layer is attached to a molten polymer layer, which is support for the nanoporous gold layer and ink reservoir at the same time. The nanoporous gold layer in turn stabilizes the topography of the stamps' contact surfaces. As examples, arrays of submicron microdots of polystyrene and poly(vinylidenefluoride-trifluoroethylene) (PVDF-TrFE) are manufactured. The P(VDF-TrFE) microdots are partially crystalline, ferroelectric, and can be locally poled. It is envisioned that the methodology reported here can be automatized and may be extended to functional low-molecular-mass compounds, such as active pharmaceutical ingredients.

Photonic engineering of InP towards homoepitaxial short-wavelength infrared VCSELs

Many emerging opportunities, such as three-dimensional (3D) sensing, biophotonics, and optical data links, call for vertical cavity surface-emitting lasers (VCSELs) that operate in the short-wavelength infrared (SWIR) range. In this paper, we report the use of InP distributed Bragg reflector (DBR) mirrors to overcome an impasse in wafer-level mass production of SWIR VCSELs. The DBRs were based on homoepitaxial InP structures and selectively converted through electrochemistry into quarter-wavelength stack structures of alternating nanoporous (NP) and nonporous InP layers with a record index contrast (Δn∼1.0) and near-unity reflectivity. We demonstrated VCSEL operation at both 1380 and 1550 nm from two separate structures prepared on InP substrates using NP–InP DBRs as the bottom mirror and dielectric DBRs as the top mirror. Room temperature continuous-wave (CW) operation of SWIR VCSELs was successfully achieved at both wavelengths with a threshold current density below 2kA/cm2, greater than milliwatt optical output, and a peak power conversion efficiency of 17%. Our work provides strong evidence that the decades-old challenge, in preparing an InP-compatible, high-performance DBR to support the SWIR-emitting vertical cavity, has been addressed and is poised to enable new applications.

Why do metals become superhydrophilic during nanosecond laser processing? Design of superhydrophilic, anisotropic and biphilic surfaces

This research investigates the impact of the surrounding environment on the characteristics of copper, nickel and tin during nanosecond laser processing. By comparing the results of processes conducted in vacuum and air, we conclude that changes in wetting properties cannot be solely attributed to development of surface microstructure. To elucidate this phenomenon, we conducted model experiments using a tin target. Laser processing parameters for the tin target were established, involving deep cavity melting without ablation, resulting in highly evolved material morphology. Under these conditions, laser processing in air did not lead to metal hydrophilization. Therefore, our study demonstrates that the primary cause of changes in material wetting properties during nanosecond laser processing is the re-deposition of ablation products onto the material surface. These products form a nanoporous layer that enhances wicking capabilities and subsequently serves as a sorbent for various impurities, gradually leading to the hydrophobization of most commonly used materials. The proposed mechanism opens the possibility for the development of new methods to create materials with biphilic and anisotropic wetting properties. The key insight lies in the control of the thickness of the nanoporous layer, as it emerges as a pivotal factor dictating wettability properties and wicking capability.

Nanoscale investigations of femtosecond laser induced nanogratings in optical glasses.

Femtosecond (fs) laser irradiation inside transparent materials has drawn considerable interest over the past two decades. More specifically, self-assembled nanogratings, induced by fs laser direct writing (FLDW) inside glass, enable a broad range of potential applications in optics, photonics, or microfluidics. In this work, a comprehensive study of nanogratings formed inside fused silica by FLDW is presented based on high-resolution electron microscopy imaging techniques. These nanoscale investigations reveal that the intrinsic structure of nanogratings is composed of oblate nanopores, shaped into nanoplanes, regularly spaced and oriented perpendicularly to the laser polarization. These nanoporous layers are forced-organized by light, resulting in a pseudo-organized spacing at the sub-wavelength scale, and observed in a wide range of optical glasses. In light of the current state of the art, we discuss the imprinting of nanoporous layers under thermomechanical effects induced by a plasma-mediated nanocavitation process.