Surface Wettability Measurements Research Articles

Improving the bonding technology of aluminium sheet used in the construction industry by gas flame surface treatment

Abstract According to current building trends, aluminium sheets can be used as building cladding elements. The advantage is that aluminium has a low density but high strength and resistance to atmospheric corrosion. For a nice appearance, these sheets are coloured with a polyester-based powder coating and are fixed by adhesive bonding on the reverse side. For adhesion, a flexible adhesive is required, and it should be noted that the surface is painted. From a safety point of view, it is important that the strength of the bonded joint does not deteriorate over many years. In our research, we investigate the applicability of gas flame surface treatment technologies to improve the bonding technology of aluminium sheets coated with polyester-based paints. The effectiveness of the surface treatment is tested by surface wettability measurements and, based on the results obtained, test joints are made to test their tensile and shear strength.

Nanostructured multilayer Cr/CrN coatings on 316L stainless steel for proton exchange membrane fuel cell bipolar plates

Nowadays, hybrid surface modification approaches offer tailored solutions for improving the corrosion resistance and electrical conductivity of the bipolar plates (BPPs) in proton exchange membrane fuel cells (PEMFCs). In the present study, a combination of plasma nitriding and physical vapor deposition (PVD) processes was used to apply a nanometric Cr/CrN multilayer coating onto 316L stainless steel (SS316L) bipolar plates. The performance of the resulting plasma nitrided, PVD-coated, and combined plasma nitriding/PVD-coated SS316L BPPs was examined by phase and morphological characterizations, surface wettability measurements, interfacial contact resistance (ICR), and electrochemical investigations. Potentiodynamic and potentiostatic polarization evaluations, electrochemical impedance spectroscopy (EIS) and Mott-Schottky asessments were conducted on the coated samples in a simulated PEMFC cathode environment at temperatures of 25 °C and 75 °C. Results indicated that the Cr/CrN multilayer coating deposited on the plasma-nitrided 316L BPP exhibited a remarkable 100-fold improvement in corrosion resistance compared to the uncoated substrate. Also, the combination of nitriding and PVD resulted in a significant reduction of the ICR from 186 mΩ cm2 for the uncoated SS316L to 10.2 mΩ cm2 for the coated sample. Multilayer coatings based on the combination of plasma nitriding and PVD treatment can identified as promise candidates for BPP applications.

Cutting-Based Manufacturing and Surface Wettability of Microtextures on Pure Titanium.

Pure titanium is a preferred material for medical applications due to its outstanding properties, and the fabrication of its surface microtexture proves to be an effective method for further improving its surface-related functional properties, albeit imposing high demands on the processing accuracy of surface microtexture. Currently, we investigate the fabrication of precise microtextures on pure titanium surfaces with different grid depths using precision-cutting methods, as well as assess its impact on surface wettability through a combination of experiments and finite element simulations. Specifically, a finite element model is established for pure titanium precision cutting, which can predict the surface formation behavior during the cutting process and further reveal its dependence on cutting parameters. Based on this, precision-cutting experiments were performed to explore the effect of cutting parameters on the morphology of microtextured pure titanium with which optimized cutting parameters for high-precision microtextures and uniform feature size were obtained. Subsequent surface wettability measurement experiments demonstrated from a macroscopic perspective that the increase in the grid depth of the microtexture increases the surface roughness, thereby enhancing the hydrophilicity. Corresponding fluid-solid coupling finite-element simulation is carried out to demonstrate from a microscopic perspective that the increase in the grid depth of the microtexture decreases the cohesive force inside the droplet, thereby enhancing the hydrophilicity.

Influence of boron incorporated biphasic calcium phosphate on mechanical, thermal, and biological properties of poly(vinylidene fluoride) membrane scaffold

AbstractIn this paper, boron (B)‐doped biphasic calcium phosphate (BCP)/poly(vinylidene fluoride) (PVDF) membrane scaffolds were developed by the combination of non‐solvent induced phase separation and lyophilization processes. In addition, the effects of the synthesized B‐incorporated BCP powders on the properties of the fabricated scaffolds were investigated. The physicochemical and morphological properties of the scaffolds were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy. The physical properties were evaluated by surface wettability and swelling measurements, whereas the mechanical properties were investigated by tensile strength measurements. The thermal behavior was determined by differential scanning calorimetry, the β‐crystallization ratio was calculated by FTIR, and the β‐phase structure was characterized by X‐ray diffraction. The bioactivity was evaluated in the simulated body fluid, and the cytotoxicity of the scaffolds was also investigated by performing in vitro cell culture experiments. The results showed that the incorporation of B into the PVDF matrix improved the hydrophilicity while reducing the degree of swelling of the scaffolds. Tensile strength was slightly reduced by the powder content, but yet the strength of all scaffolds was mechanically compatible with native bone. Increasing the B content up to 0.5 and 1 wt.% was improved the thermal properties, the β‐crystalline phase fraction, and thus the piezoelectricity. Furthermore, B‐doped BCP/PVDF‐based scaffolds significantly promoted bioactivity, cell viability, and proliferation without cytotoxicity, compared to the PVDF scaffold, depending on the B content. In conclusion, our results indicate that the PVDF‐based composites in the form of membrane scaffolds that support bone growth have the potential to be highly sought‐after candidates in the field of biomedical applications.

Metallization of polypropylene substrates through surface functionalization and physical vapor deposition of chromium coatings

Physical vapor deposition (PVD) of chromium coatings represents an interesting alternative to electroplating to obtain metallized plastic parts for a variety of manufacturing sectors. This process is however hampered by the limited adhesion of the metallic layer on the underlying polymeric substrates. Within this context, PVD metallization of polypropylene substrates has so far been particularly challenging given the low surface energy and poor wettability of this commodity plastics. To address this issue, a comprehensive approach is proposed here to enable the production of PVD-metallized PP substrates with excellent and stable interlayer adhesion. The adhesive properties of the PP substrate are modified by a selective UV-induced photografting process in which vinyl-, glycidyl- or 2-hydroxyethyl methacrylate species are covalently attached to the PP surface, as confirmed by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and surface wettability measurements. Based on the chemistry of the photografted functionality, different resin systems are selected and investigated for use as primers to enable subsequent chromium deposition, including acrylic, epoxy and polyurethane systems. The effect of the photografting process on the adhesion between PP and the primers is systematically assessed by means of pull-off tests, highlighting a significant improvement of the adhesion force after surface functionalization with appropriate grafting agents. Finally, functionalized PP substrates are chromated through PVD, obtaining homogeneous and crack-free chromium surfaces upon judicious selection of suitable primer-grafting agent combinations. This also led to outstanding interlayer adhesion and micromechanical performance. This work provides the first demonstration of chromium-metallization of PP substrates via PVD for metallized plastic components with excellent surface characteristics, and paves the path for the design of mechanically durable and aesthetically-compliant PVD-metallized PP components.

Flotation separation of magnesite from dolomite with gellan gum as depressant and its depression mechanism

Flotation technology is an effective way to separate magnesite from dolomite. However, the efficient separation of magnesite from dolomite in sodium oleate (NaOL) system is rather challenging without depressants due to their highly similar physicochemical surface properties. Herein, gellan gum (GG) was employed as a new flotation inhibitor in separating magnesite from dolomite. The depression performance and inhibitory mechanism were systematically studied by flotation experiments, and a number of surface testing technologies. Flotation experiments indicated that GG greatly affected the floatability of dolomite, whereas it had little impact on the magnesite flotation. The artificial mixed mineral experiments confirmed that effective separation of magnesite and dolomite was fulfilled with GG as flotation inhibitor. Zeta potential analyses, surface wettability measurements, and Fourier transform infrared (FTIR) spectroscopy tests indicated that GG strongly prevented the NaOL adhesion on the dolomite, while it scarcely impeded the NaOL adhesion onto magnesite. X-ray photoelectron spectroscopy (XPS) detections demonstrated that GG adhered stronger towards dolomite than magnesite, which was mainly due to its higher affinity towards Ca2+. AFM images intuitively identified that much stronger interaction and thicker adsorption layer occurred on the dolomite than magnesite. Additionally, higher adsorption concentration, closer adsorption distance and hither adsorption strength of GG on the dolomite was further confirmed by molecular dynamics (MD) simulations. Therefore, GG was a promising flotation depressant to separate magnesite from dolomite and achieve the efficient exploitation of magnesite resources.

Graphene oxidation and reduction in medium vacuum by an UV lamp at 365 nm wavelength

ABSTRACT The time-dependent graphene oxide (GO) reduction in medium vacuum under ultraviolet (UV) irradiation at 365 nm has been investigated. We found that GO exposed to UV at room temperature and at a vacuum of about 10−1 mbar shows a notable oxidation for irradiation times up to about 60 min followed by a successive reduction up to 210 min. Characterization measurements have been performed mainly using the Attenuated Total Reflectance (ATR) Fourier Transform Infrared (FTIR) and Raman spectroscopies. ATR-FTIR spectra, acquired in the (400–4000) cm−1 wavenumber range, have indicated an initial decrement of the IR transmission (oxidation process) with the exposure time up to about 60 min and a successive increase of the IR transmission (reduction process) for greater irradiation times up to 210 min. The IR transmission bands are attributed to the oxygen functional groups contained in GO which increase for low UV exposure times and gradually disappear during the UV-induced reduction process. Raman spectra confirm this interpretation showing a decrease of the AD/AG ratio value, with respect to the GO virgin value, for low UV exposure times and an increase for greater times. The GO oxidation and reduction processes, due to the UV GO treatment in medium vacuum conditions, have been also verified by energy dispersive X-ray fluorescence and surface wettability measurements.

Synthesis and physical investigation of Al doped La2O3 thin films for wettability applications

AbstractIn this work, aluminum doped La2O3 thin films deposited by the spray pyrolysis technique, are investigated by many characterization techniques. First, XRD spectra reveal the presence of two phases. A dominant cubic phase is obtained for pure La2O3 with (220) preferential orientation. The second hexagonal phase with (004) orientation is present in all doped samples. It is found that Al doping induces a perovskite crystalline structure identified as lanthanum aluminate (LaAlO3). Second, FTIR spectra include the main peaks of La‐O bonds related to La2O3 structure. Photoluminescence (PL) shows a good enhancement by Al doping related to LaAlO3 nanoparticles. Finally, the surface wettability measurements corroborate the hydrophobic character of all doped samples.

Tuning in optoelectronic properties of In/Te bilayer heterostructure upon annealing at different temperatures: surface wettability and photo response study for photonic and solar cell applications.

The current study depicted the influence of annealing temperature on In/Te bilayer thin film of 350 nm synthesized by thermal evaporation method. The interfacial diffusion of In into Te sites at different annealing temperatures (100 °C, 150 °C, 200 °C, 250 °C) modified the structural as well as the electro-optical response of the films. The structural study showed the appearance of an orthorhombic In4Te3 peak with annealing. The surface texture showed the particle nature with homogeneous distribution with annealing temperatures. The cross-sectional view of the bilayer and annealed film confirmed the formation of In/Te film with a total thickness of 350 nm. Surface mapping images confirm the homogeneous and uniform elemental distribution. The transmission was enhanced with annealing and showed broad transparency over the NIR region, making them suitable for IR device applications. The enhanced optical bandgap with annealing due to induced local structural changes reduced the optical parameters, such as refractive index, dielectric constant, and nonlinear susceptibility. The surface wettability measurements showed an enhanced hydrophobic nature with annealing. The variation of photocurrent with respect to voltage showed an ohmic nature, with enhancement from nA to ∼mA with annealing. Such alteration opened new ways to be used in solar cells, photodetectors, and photonic device applications.

A Novel Electrodialysis Membrane, Modified by Polydopamine and Carbon Nanofibers, Removes Toxic Heavy Metal Ions From Wastewaters

Background: In light of severe and growing shortages of clean water and the rising environmental pollution in many countries, seawater desalination has been an effective method to produce freshwater. Cationic membranes have enabled environmental scientists to effectively remove toxic heavy metals from wastewater and to regenerate freshwater. Methods: We used a novel method, involving electro- and physico-chemical membranes to successfully remove toxic heavy metal ions (copper & chromium) from wastewater samples. Specifically, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, surface wettability, flux, selectivity and electrical resistance measurements were applied to conduct this study. Results: The obtained results illustrated relatively uniform foaming of the modified membranes. Also, electron microscopic images indicated almost even distribution of the particles. The dada indicated that applying polydopamine layer and incorporating nanofibers in monomer solution caused surface hydrophilic enhancement. Also, increased carbon nanofibers loading ratio to 0.07% raised the ionic flux. The data also showed a higher capacity in the modified membranes for the removal of copper and chromium ions from the wastewater samples. Although the surface modified membranes displayed a higher flux and lower permselectivity to some extents, utilizing nanoparticles led to a steady trend of ion elimination. Generally, carbon nanofibers incorporation to the membrane surface modified samples up to 0.1% weight, resulting in nearly a constant areal electrical resistance. Conclusion: The novel method developed by this study is an excellent candidate with high potential for the removal of toxic heavy metal ions from wastewater samples.

Synthesis of a novel dithiocarbamate collector and its selective adsorption mechanism in galena flotation

The high consumption of depressants in the flotation separation of sulfide lead-zinc ores would cause serious environmental problems, and conventional dithiocarbamate collectors suffered from the drawbacks of low flotation activity and poor selectivity. Hence, it’s urgent to develop efficient collectors for the separation of galena and sphalerite. In this study, a novel morpholine dithiocarbamate propylene ester (MDPE) was designed and synthesized by the introduction of morpholine structure containing the C-O-C group, aiming to improve the surface activity and selectivity of the molecule. Surface tension tests indicated that MDPE exhibited a higher surface activity and stronger hydrophobicity than conventional collector N,N-diethyl dithiocarbamate propiononitrile ester (Ester-105) due to the introduction of morpholine structure. Microflotation experiments revealed that compared with Ester-105, higher flotation recovery of galena (90.75%) with significantly improved flotation selectivity against sphalerite by using MDPE of 2 × 10−4 mol/L at low alkalinity (pH=8.5) was obtained. Surface wettability measurements displayed that MDPE enhanced the hydrophobicity of galena surfaces more obviously than sphalerite. UV–vis spectra showed that MDPE preferred to interact with Pb2+ rather than with Zn2+. Adsorption experiments elucidated that the adsorption capacity of MDPE for galena was stronger than that for sphalerite. FTIR spectra and XPS proved that MDPE might chemically adsorb on the surface of galena through the formation of C-S-Pb structure. DFT calculations were conducted to demonstrate that the introduction of morpholine structure improved the chemical activity of the molecule.

Janus-type hypergolic fuels for hybrid systems using hydrogen peroxide and hydroxylammonium nitrate-based oxidizers

Development of fully green hybrid propulsion systems, in which both the oxidizer and the fuel are environmentally benign, while having a desirable performance under in-space conditions, is a formidable challenge. Herein, we present new air-stable solid propellants capable of exhibiting hypergolic ignitions with commercially available H2O2 (70 %) and its low-freezing formulation containing hydroxylammonium nitrate (HAN). A top performing Janus-type fuel 15 showed remarkable ignition delay time of 4 ms with HAN-H2O2 formulation, even at −40 ℃. The Janus-type design approach allowed modulation of the ignition delay times by varying the carbon chain-length, the type of the used transition metals and the molecular structure of the resulted solid fuels. Studies of HAN and related salts formulations with H2O2 allowed us to get an insight into the reasons of the stability of HAN-H2O2 formulations. UV–vis and EPR monitoring of selected fuels reactions with oxidizers, as well as surface wettability measurements, provided a valuable information related to the better understanding of the hypergolic reaction mechanisms, which should contribute to the design of the next generation of green hypergolic propulsion systems. We also successfully tested fuel 15 in a custom-made small-scale static hybrid motor system, injecting H2O2 in a sequence of pulse or in continuous flow modes.

Enhancement of the corrosion resistance of mild steel with femtosecond laser- nanostructuring and CrCoNi medium entropy alloy coating

In this work, the corrosion resistance of mild steel surface nanostructured with a femtosecond laser and coated with high corrosion resistant CrCoNi (CCN) medium entropy alloy through magnetron sputtering is studied. Substantial improvement in corrosion protection was achieved by applying a combination of high-power femtosecond laser surface nano-structuring at ambient conditions and thin-film coating with (CCN) medium entropy alloy. XRD analysis revealed that femtosecond laser structuring increases the susceptibility of the surfaces to Fe2O3 nucleation through oxidation. The surface wettability measurements and electrochemical polarization tests revealed that the combined approach of femtosecond laser structuring and magnetron sputter coating is the best for desired high corrosion resistance. Through this novel method, the resulting corrosion resistance of mild steel was improved by more than one-fold. The results are explained considering the detailed microstructural analysis. The presented findings open new possibilities for corrosion prevention using a combination of new powerful technologies that yield to unprecedented corrosion-inhibition efficacy.

Mechanism of Oil-in-Liquid Metal Emulsion Formation.

Gallium-based liquid metals (LMs) combine metallic properties with the deformability of a liquid, which makes them promising candidates for a variety of applications. To broaden the range of physical and chemical properties, a variety of solid additives have been incorporated into the LMs in the literature. In contrast, only a handful of secondary fluids have been incorporated into LMs to create foams (gas-in-LM) or emulsions (liquid-in-LM). LM foams readily form through mixing of LM in air, facilitated by the formation of a native oxide on the LM. In contrast, LM breaks up into microdroplets when mixed with a secondary liquid such as silicone oil. Stable silicone oil-in-LM emulsions form only during mixing of the oil with LM foam. In this work, we investigate the fundamental mechanism underlying this process. We describe two possible microscale mechanisms for emulsion formation: (1) oil replacing air in the foam or (2) oil creating additional features in the foam. The associated foam-to-emulsion density difference demonstrates that emulsions predominantly form through the addition of oxide-covered silicone oil capsules to the LM foam. We demonstrate this through density and surface wettability measurements and multiscale imaging of LM foam mixed with varied silicone oil contents in air or nitrogen environments. We also demonstrate the presence of a continuous silicone oil film on the emulsion surface and that this oil film prevents the embrittlement of contacting aluminum.

Antimicrobial surface processing of polymethyl methacrylate denture base resin using a novel silica-based coating technology.

This study investigated the surface characteristics of denture base resin coatings prepared using a novel silica-based film containing hinokitiol and assessed the effect of this coating on Candida albicans adhesion and growth. Silica-based coating solutions (control solution; CS) and CS containing hinokitiol (CS-H) were prepared. C. albicans biofilm formed on denture base specimens coated with each solution and these uncoated specimens (control) were analyzed using colony-forming unit (CFU) assay, fluorescence microscopy, and scanning electron microscopy (SEM). Specimen surfaces were analyzed by measuring the surface roughness and wettability and with Fourier-transform infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR). Stability of coated specimens was assessed via immersion in water for 1week for each group (control-1w, CS-1w, and CS-H-1w) followed by CFU assay, measurement of surface roughness and wettability, and FT-IR. CS-H and CS-H-1w contained significantly lower CFUs than those present in the control and control-1w, which was also confirmed via SEM. Fluorescence microscopy from the CS-H group identified several dead cells. The values of surface roughness from coating groups were significantly less than those from the control and control-1w. The surface wettability from all coating groups exhibited high hydrophobicity. FT-IR analyses demonstrated that specimens were successfully coated, and 1H NMR analyses showed that hinokitiol was incorporated inside CS-H. A silica-based denture coating that incorporates hinokitiol inhibits C. albicans growth on denture. We provide a novel antifungal denture coating which can be helpful for the treatment of denture stomatitis.

Electrochemical and computational estimations of cephalosporin drugs as eco-friendly and efficient corrosion inhibitors for aluminum in alkaline solution

In this study, the anionic state of Ceftriaxone sodium (Cefx) and Ceftazidime (Cefz) medication corrosion inhibition capabilities for Al in 0.1 M NaOH solution are explored using various electrochemical analyses. Furthermore, the morphological structure and surface chemical composition of the impact of these drugs on the Al substrate in NaOH are investigated. For the prediction and analysis of interactions between molecule structure and inhibition efficiency, quantum chemical calculations (QC), Monte Carlo simulations (MC), and molecular dynamics (MD) simulations (MD) are performed. The electrochemical findings reveal that the inhibitory effectiveness increases with increasing drug concentrations and declines with rising temperature, reaching a maximum value of 78.4% for 300 ppm Cefx while 59.5% for 300 ppm Cefz at 293 K, implying that Cefx outperforms for Cefz. In addition, the studied drugs act as cathodic inhibitors, and their adsorption is spontaneous and mixed type adsorption in its nature that obeys Freundlich isotherm for Cefz while Temkin isotherm is the best-fitted one for Cefx. Surface analysis and wettability measurements imply that Cefx and Cefz shield the Al against corrosion by surface adsorption and generating a protective hydrophobic film. Thermodynamic activation parameters in the absence and presence of 300 ppm of the studied drugs are calculated and discussed. The energies of the border molecular orbitals and computed molecular parameters for the investigated drugs revealed that anionic Cefx is more readily adsorbed on the Al surface than Cefz. This finding is validated further using MC and MD simulations. Overall, the proposed cephalosporin drugs delivered a cost-effective and facile approach for boosting the efficiency of corrosion inhibitors for Al under aggressive conditions.

Metal Ion Augmented Mussel Inspired Polydopamine Immobilized 3D Printed Osteoconductive Scaffolds for Accelerated Bone Tissue Regeneration

Critical bone defects with a sluggish rate of auto-osteoconduction and imperfect reconstruction are motivators for the development of an alternate innovative approach for the regeneration of bone. Tissue engineering for bone regeneration signifies an advanced way to overcome this problem by creating an additional bone tissue substitute. Among different fabrication techniques, the 3D printing technique is obviously the most efficient and advanced way to fabricate an osteoconductive scaffold with a controlled porous structure. In the current article, the polycarbonate and polyester diol based polyurethane-urea (P12) was synthesized and 3D porous nanohybrid scaffolds (P12/TP-nHA) were fabricated using the 3D printing technique by incorporating the osteoconductive nanomaterial titanium phosphate adorned nanohydroxyapatite (TP-nHA). To improve the bioactivity, the surface of the fabricated scaffolds was modified with the immobilized biomolecule polydopamine (PDA) at room temperature. XPS study as well as the measurement of surface wettability confirmed the higher amount of PDA immobilization on TP-nHA incorporated nanohybrid scaffolds through the dative bone formation between the vacant d orbital of the incorporated titanium ion and the lone pair electron of the catechol group of dopamine. The incorporated titanium phosphate (TP) increased the tensile strength (53.1%) and elongation at break (96.8%) of the nanohybrid composite as compared to pristine P12. Moreover, the TP incorporated nanohybrid scaffold with calcium and phosphate moieties and a higher amount of immobilized active biomolecule improved the in vitro bioactivity, including the cell viability, cell proliferation, and osteogenic gene expression using hMSCs, of the fabricated nanohybrid scaffolds. A rat tibia defect model depicted that the TP incorporated nanohybrid scaffold with immobilized PDA enhanced the in vivo bone regeneration ability compared to the control sample without revealing any organ toxicity signifying the superior osteogenic bioactivity. Thus, a TP augmented polydopamine immobilized polyurethane-urea based nanohybrid 3D printed scaffold with improved physicochemical properties and osteogenic bioactivity could be utilized as an excellent advanced material for bone regeneration substitute.

In Vivo Evaluation of Gamma-Irradiated and Heparin-Immobilized Small-Diameter Polycaprolactone Vascular Grafts with VEGF in Aged Rats.

The effectiveness of small-diameter vascular grafts depends on their antithrombogenic properties and ability to undergo accelerated endothelialization. The extreme hydrophobic nature of poly(ε-caprolactone) (PCL) hinders vascular tissue integration, limiting its use in medical implants. To enhance the antithrombogenicity of PCL as a biomaterial, we grafted 2-aminoethyl methacrylate (AEMA) hydrochloride onto the PCL surface using gamma irradiation; developed a biodegradable heparin-immobilized PCL nanofibrous scaffold using gamma irradiation and N-(3-dimethylaminopropyl)-N′-ethyl carbodiimide hydrochloride/N-hydroxysuccinimide reaction chemistry; and incorporated vascular endothelial growth factor (VEGF) into the scaffold to promote vascular endothelial cell proliferation and prevent thrombosis on the vascular grafts. We assessed the physicochemical properties of PCL, heparin-AEMA-PCL (H-PCL), and VEGF-loaded heparin-AEMA-PCL (VH-PCL) vascular grafts using scanning electron microscopy, attenuated total reflection–Fourier transform infrared spectroscopy, toluidine blue O staining, and fibrinogen adsorption and surface wettability measurement. In addition, we implanted the vascular grafts into 24-month-old Sprague Dawley rats and evaluated them for 3 months. The H-PCL and VH-PCL vascular grafts improved the recovery of blood vessel function by promoting the proliferation of endothelial cells and preventing thrombosis in clinical and histological evaluation, indicating their potential to serve as functional vascular grafts in vascular tissue engineering.

Foliar water uptake in the needles of Pinus torreyana

The natural habitat of Pinus torreyana, the Torrey pine, is restricted to two locales in coastal Southern California that experience substantial fog and low clouds during the dry months of a Mediterranean climate. In similar semi-arid climate systems that encounter fog or low clouds, many plants can capture atmospheric moisture and are capable of direct foliar water uptake to reduce water stress. In this study, we investigated if the needles of P. torreyana are also capable of direct water uptake. In addition to water immersion, we measured the surface properties along a needle using microdroplets. The droplet contact angle is a measure of surface wettability, and the droplet absorption is a measure of localized foliar water uptake. The results showed that the entire length of the P. torreyana needle, including under the base sheath, is hydrophilic and capable of direct water uptake. The spatial gradients of the wettability and the water uptake along the needle are relatively small. Moreover, the wettability and water uptake increase from young shoots to one-year and two-year old needles. Our results also showed that the decrease in water uptake at higher contact angles can be described by a linear regression. Compared with the leaves of four shrubs in the same habitat, Heteromeles arbutifolia, Malosma laurina, Rhus integrifolia, and Eriodictyon crassifolium, the P. torreyana needles have lower contact angles and higher water uptake rates.

Surface effects and wettability measurement considerations in fluorinated carbon nanotubes

Surface effects and wettability measurement considerations in fluorinated carbon nanotubes