More Like this

1. Synthesis of ZnO/TiO2-Based Hydrophobic Antimicrobial Coatings for Steel and Their Roughness, Wetting, and Tribological Characterization

   https://doi.org/10.1115/1.4053777  

   Hasan, Md Syam; Zemajtis, Filip; Nosonovsky, Michael; Sobolev, Konstantin (August 2022, Journal of Tribology)

   Abstract We synthesized novel TiO2/ZnO-phosphate (TP/ZP) and polymethyl hydrogen siloxane (PMHS)-based two-layer hydrophobic coatings with potential antimicrobial properties tuned for application on steel substrates. The mathematical method of topological data analysis was applied to surface roughness data. Wetting characterizations showed stable hydrophobic behavior of the two-layer coated samples. Through tribological characterization, we compared the friction behavior of uncoated steel samples and steel samples coated with different coating materials. The coefficient of friction of uncoated base materials (ranging from 0.221 to 0.269) and the two-layer hydrophobic coatings (ranging from 0.234 to 0.273) indicated that the coatings confer hydrophobic properties to the substrates without a notable change in the friction behavior. We observed the correlations between the wetting and friction behaviors and the average roughness of the coated samples. Analysis of the micrographs of the scratched surfaces revealed preliminary information about the durability and abrasion resistance of the coatings. 

   more » « less
2. Enhanced self-cleaning performance on hydrophobic glass surfaces using hydrophilic dagger features coated with silica nanoparticles

   https://doi.org/10.1016/j.solmat.2024.113366  

   Abeywardena, Madupa; Zimmermann, Thomas; Xu, QianFeng; Löbmann, Peer; Mandel, Karl; Stauch, Claudia; Lyons, Alan (April 2025, Solar Energy Materials and Solar Cells)

   Accumulated dust on solar cover glass reduces transmittance, leading to decreased energy efficiency of photovoltaic (PV) modules. Hydrophobic coatings on solar cover glass have been shown to provide anti-soiling properties when exposed to a condensing environment (e.g. dew). The addition of hydrophilic features along the top edge of the hydrophobic coated glass enhances condensation rates and can be used to achieve self-cleaning of the surfaces. However, to date, relatively long times have been required to clean the surfaces. In this study, we developed a new design for hydrophilic features that reduce the time required to clean the surface in laboratory tests as measured by laser scanning microscopy, optical photographs and UV–vis spectroscopy. The dagger-shaped features improve self-cleaning performance by a combination of three factors: a silica nanoparticle (NP) hydrophilic coating which enhances condensation rate due to a low water contact angle (WCA) and nano-scale porosity; the stepwise transition from the low WCA silica NP region to the high WCA silanized hydrophobic region via a bare glass transition zone; and the pointed shape of the hydrophobic dagger features which further minimizes the barrier for transport of droplets from the condensing region to the high-mobility, hydrophobic, region of the surface. The hydrophilic silica nanoparticle-coated dagger features not only improve the self-cleaning efficiency of the hydrophobic surfaces but also increase the overall amount of water harvested. Such coating designs provide an effective approach to reducing maintenance costs as well as increasing the overall energy output of PV panels. 

   more » « less
3. The competing influence of surface roughness, hydrophobicity, and electrostatics on protein dynamics on a self-assembled monolayer

   https://doi.org/10.1063/5.0078797  

   Misiura, Anastasiia; Dutta, Chayan; Leung, Wesley; Zepeda O, Jorge; Terlier, Tanguy; Landes, Christy F. (March 2022, The Journal of Chemical Physics)

   Surface morphology, in addition to hydrophobic and electrostatic effects, can alter how proteins interact with solid surfaces. Understanding the heterogeneous dynamics of protein adsorption on surfaces with varying roughness is experimentally challenging. In this work, we use single-molecule fluorescence microscopy to study the adsorption of α-lactalbumin protein on the glass substrate covered with a self-assembled monolayer (SAM) with varying surface concentrations. Two distinct interaction mechanisms are observed: localized adsorption/desorption and continuous-time random walk (CTRW). We investigate the origin of these two populations by simultaneous single-molecule imaging of substrates with both bare glass and SAM-covered regions. SAM-covered areas of substrates are found to promote CTRW, whereas glass surfaces promote localized motion. Contact angle measurements and atomic force microscopy imaging show that increasing SAM concentration results in both increasing hydrophobicity and surface roughness. These properties lead to two opposing effects: increasing hydrophobicity promotes longer protein flights, but increasing surface roughness suppresses protein dynamics resulting in shorter residence times. Our studies suggest that controlling hydrophobicity and roughness, in addition to electrostatics, as independent parameters could provide a means to tune desirable or undesirable protein interactions with surfaces. 

   more » « less
4. Synthesis and Characterization of Hydrophobic and Low Surface Tension Polyurethane

   https://doi.org/10.3390/coatings13071133  

   Rudlong, Autumn M; Goddard, Julie M (July 2023, Coatings)

   Polyurethane is a common polymeric coating, providing abrasion resistance, chemical durability, and flexibility to surfaces in the biomedical, marine, and food processing industries with great promise for future materials due to its tunable chemistry. There exists a large body of research focused on modifying polyurethane with additional functionalities, such as antimicrobial, non-fouling, anticorrosive action, or high heat resistance. However, there remains a need for the characterization and surface analysis of fluoro-modified polyurethanes synthesized with commercially available fluorinated polyol. In this work, we have synthesized traditional solvent-borne polyurethane, conventionally found in food processing facilities, boat hulls, and floor coatings, with polyurethane containing 1%, 2%, and 3% perfluoropolyether (PFPE). Polyurethane formation was confirmed by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, with the urethane band forming at 1730 cm−1 and the absence of free isocyanate stretching from 2275–2250 cm−1. X-ray photoelectron spectroscopy (XPS) was used to confirm perfluoropolyether polymerization with an increase in the atomic percentage of fluorine. Wettability and hydrophobicity were determined using a dynamic water contact angle with significant differences in advancing the water contact angle with the inclusion of perfluoropolyether blocks (PU–co–1PFPE 131.5° ± 8.0, PU–co–2PFPE 130.9° ± 5.8, and PU–co–3PFPE 128.8° ± 5.2) compared to the control polyurethane (93.6° ± 3.6). The surface orientation of fluorine supported the reduced critical surface tensions of polyurethane modified with PFPE (12.54 mN m−1 for PU–co–3PFPE compared to 17.19 mN m−1 for unmodified polyurethane). This work has demonstrated the tunable chemical qualities of polyurethane by presenting its ability to incorporate fluoropolymer surface characteristics, including low critical surface tension and high hydrophobicity. 

   more » « less
5. Modification of Nafion's nanostructure for the water management of PEM fuel cells

   https://doi.org/10.1002/pol.20220774  

   Li, Yuanchao; Linnell Schwab, Natalie; Briber, Robert M.; Dura, Joseph A.; Nguyen, Trung Van (March 2023, Journal of Polymer Science)

   Abstract A PEM fuel cell with the Nafion ionomer phase of the cathode catalyst layer (CL) that was exposed to hot dry gas during the hot‐pressing process showed improved performance over the whole current density range and ~ 220% peak power increase with humidified air at 80°C. This enhanced performance is attributed to the modified structure of the perfluorosulfonic acid (PFSA) ionomer layer in the CL during the MEA's hot‐pressing process. The dry gas exposure above the glass transition temperature (T_g) results in the aggregation of the ionic groups to retain the residue water molecules. This process separates the ionomer into ionic‐group‐rich domains and ionic‐group‐sparse domains. The ionic‐group‐sparse domains create hydrophobic interface and reactant transport channels with lower water content and thus higher oxygen solubility in the ionomer. Accordingly, the water‐unsaturated ionomer and its surface hydrophobicity enhance the kinetic‐controlled and concentration‐polarized regions of the fuel cell polarization curve, respectively. The surface hydrophobicity of the ionomer layer is analyzed by the contact angle measurement and XPS. The durability of the hydrophobic effect belowT_gis demonstrated by boiling the treated material. Re‐treating the hydrophobic sample with humidified gas exposure aboveT_geventually exhibits hydrophilic features, further proving the manipulability of the ionic group distribution. 

   more » « less