Search Results (6)

The antifogging coating based on super-hydrophilic polymer is regarded as the most promising strategy to avoid fogging but suffers from short-term effectiveness due to antifogging failure induced by water invasion. In this study, a black phosphorus nanosheets (BPs) hybrid polymer hetero-network coating (PUA/PAHS/BPs HN) was prepared by UV curing for the first time to achieve long-term antifogging performance. The polymer hetero-network (HN) structure was composed of two novel cross-linked acrylic resin and polyurethane acrylate. Different from physical blending, a covalent P-C bond between BPs and polymer is generated by UV initiated free radical reaction, resulting in BPs firmly embedded in the polymer HN structure. The BPs enriched on the coating surface by UV regulating migration prevent permeation of water towards the inside of the coating through its own good water-based lubricity and water absorption capacity. Compared with the nonhybrid polymer HN, PUA/PAHS/BPs HN not only has higher hardness and better friction resistance properties, but also exhibits superior water resistance and longer antifogging duration. Since water invasion was greatly reduced by BPs, the PUA/PAHS/BPs HN coating maintained antifogging duration for 60 min under a 60 °C water vapor test and still maintained long-term antifogging performance after being immersed in water for 5 days. Full article

The acquiring of superhydrophilic surfaces attracts the strong interest in self-cleaning, anti-fogging and anti-icing fields based on the unique features. However, the persistent time of superhydrophilic surfaces is still facing a big challenge because of easily adsorbing hydrophobic groups. Here, we propose a strategy to achieve a superhydrophilicity persisting for an unprecedently long time on sapphire surfaces, by compounding the femtosecond laser-induced hierarchical structures and the subsequent varnish of TiO₂. The superhydrophilic effect (with a contact angle of CA = 0°) created by our method can be well prolonged to at least 180 days, even for its storage in air without additional illumination of UV lights. Based on comprehensive investigations, we attribute the underlying mechanisms to the coordination of laser-induced metal ions on the material surface via TiO₂ doping, which not only prevents the adsorption of the nonpolar hydrocarbon groups, but also modulates the photo-response properties of TiO₂. In addition, further experiments demonstrate the excellent anti-fogging properties of our prepared samples. This investigation provides a new perspective for further enhancing the durability of superhydrophilicity surfaces. Full article

Seeds of wheat cultivar Bologna were treated with a low-pressure, inductively coupled, radio frequency oxygen plasma. E-mode and H-mode plasma at the real powers of 25 and 275 W, respectively, was used at treatment times of 0.1–300 s. Plasma affected seed surface chemistry, determined by XPS, and surface topography, visualized by SEM. The combined effects of functionalization and etching modified seed surface wettability. The water contact angle (WCA) exponentially decreased with treatment time and correlated with the product of discharge power and treatment time well. Super-hydrophilicity was seen at a few 1000 Ws, and the necessary condition was over 35 at.% of surface oxygen. Wettability also correlated well with O-atom dose, where super-hydrophilicity was seen at 10²⁴–10²⁵ m⁻². A relatively high germination percentage was seen, up to 1000 Ws (O-atom dose 10²³–10²⁴ m⁻²), while seed viability remained unaffected only up to about 100 Ws. Extensively long treatments decreased germination percentage and viability. Full article

We present the results of one year observation of wetting and corrosion properties of nanosecond fiber laser-textured stainless steel, uncoated and coated with epoxy or FAS (fluoroalkylsilane)-TiO₂/epoxy. A comparative study was performed on samples kept under ambient conditions and in reduced air pressure and humidity. The results show the ability to induce wettability conversion from initially superhydrophilic to final superhydrophobic state either indirectly by ageing the uncoated laser-textured surface or directly by application of FAS-TiO₂/epoxy coating. The storage conditions significantly influenced the wettability development of uncoated laser-textured steel, i.e., the process of ageing was slowed down in reduced air pressure and humidity. Detailed surface chemical analysis revealed that adsorption of the organic matters from the surrounding media influences the wettability conversion and ageing. However, the ageing of the coated surfaces was not affected by the storage conditions. Corrosion stability of uncoated laser-textured surfaces was enhanced over time due to the wettability transition, depending on their morphology. Coatings represent a superior barrier over the texture and wettability with the stable long-term surface protection against aggressive media. Full article

Polyethylene glycol (PEG)-phospholipids in long-circulating liposomes cause non-specific immune reactions; mainly attributable to negatively-charged phosphoryl s at the interface of PEG and phospholipid. We investigated a novel lipopolymer, by which a superhydrophilic polymer (SHP) is conjugated to a non-phospholipid N¹-(2-aminoethyl)-N⁴-hexadecyl-2-tetradecylsuccinamide (HDAS). The modification of preformed liposomes HDAS-SHP, HDAS-PEG₂₀₀₀, and DSPE-PEG₂₀₀₀ were performed by post-insertion techniques. The efficiency of post-insertion and desorption rates, from the liposome surface, were determined. HDAS-SHP micelles showed highly positive zeta potential (+28.4 mV); zeta potentials of DSPE-PEG₂₀₀₀ and HDAS-PEG₂₀₀₀ micelles were −34.4 mV, and −3.7 mV, respectively. Critical micelle concentration predicted amphiphilicity of HDAS-SHP (CMC 2.58 µM) as close to that of DSPE-PEG₂₀₀₀ (CMC 2.44 µM). Both HDAS-SHP and HDAS-PEG₂₀₀₀ post-inserted with comparable efficiency (79%, and 73%, respectively), but noticeably lower than DSPE-PEG₂₀₀₀ (90%). The desorption rate of HDAS-SHP was close to that of DSPE-PEG₂₀₀₀ (0.53%/h, and 0.45%/h, respectively); the desorption rate for HDAS-PEG₂₀₀₀ was slightly more at 0.67%/h. Compared to plain liposomes, both HDAS-SHP- and DSPE-PEG₂₀₀₀-liposomes showed significant leakage of encapsulated Na-fluorescein isothiocyanate (FITC) upon incubation with serum. At the same time, both modified liposomes were found to suppress serum levels of the complement proteins, Bb and C4d. We infer that HDAS-SHP is a viable alternative to commonly-used PEG-phospholipid derivatives for stealth purposes. Full article

Functional ZnO nanostructured surfaces are important in a wide range of applications. Here we report the simple fabrication of ZnO surface structures at near room temperature with morphology resembling that of sea urchins, with densely packed, $\mathsf{\mu }$ m-long, tapered nanoneedles radiating from the urchin center. The ZnO urchin structures were successfully formed on several different substrates with high surface density and coverage, including silicon (Si), glass, polydimethylsiloxane (PDMS), and copper (Cu) sheets, as well as Si seeded with ZnO nanocrystals. Time-resolved SEM revealed growth kinetics of the ZnO nanostructures on Si, capturing the emergence of “infant” urchins at the early growth stage and subsequent progressive increases in the urchin nanoneedle length and density, whilst the spiky nanoneedle morphology was retained throughout the growth. $\epsilon$ -Zn(OH)₂ orthorhombic crystals were also observed alongside the urchins. The crystal structures of the nanostructures at different growth times were confirmed by synchrotron X-ray diffraction measurements. On seeded Si substrates, a two-stage growth mechanism was identified, with a primary growth step of vertically aligned ZnO nanoneedle arrays preceding the secondary growth of the urchins atop the nanoneedle array. The antibacterial, anti-reflective, and wetting functionality of the ZnO urchins—with spiky nanoneedles and at high surface density—on Si substrates was demonstrated. First, bacteria colonization was found to be suppressed on the surface after 24 h incubation in gram-negative Escherichia coli (E. coli) culture, in contrast to control substrates (bare Si and Si sputtered with a 20 nm ZnO thin film). Secondly, the ZnO urchin surface, exhibiting superhydrophilic property with a water contact angle $~ 0°$ , could be rendered superhydrophobic with a simple silanization step, characterized by an apparent water contact angle $\theta$ of 159° ± 1.4° and contact angle hysteresis $\Delta \theta$ < 7°. The dynamic superhydrophobicity of the surface was demonstrated by the bouncing-off of a falling 10 $\mathsf{\mu }\mathrm{L}$ water droplet, with a contact time of 15.3 milliseconds (ms), captured using a high-speed camera. Thirdly, it was shown that the presence of dense spiky ZnO nanoneedles and urchins on the seeded Si substrate exhibited a reflectance R < 1% over the wavelength range λ = 200–800 nm. The ZnO urchins with a unique morphology fabricated via a simple route at room temperature, and readily implementable on different substrates, may be further exploited for multifunctional surfaces and product formulations. Full article