Investigating the interrelationship of superhydrophobicity with surface morphology, topography and chemical composition in spray-coated polyurethane/silica nanocomposites

Development of PDMS/TiO2/Ag3PO4 antibacterial coating on 316L/PDMS implants: Evaluation of superhydrophobicity, bio-corrosion, mechanical behaviour, surface nanostructure and chemistry

Nanocomposite coatings based on polydimethylsiloxane were developed by adding silver phosphate and titania nanoparticles with a PDMS pre-layer for 316L stainless steel. FTIR spectra and XRD patterns confirmed the synthesis of TiO2 and Ag3PO4 nanoparticles and nanocomposite coating. FESM and AFM images show that with the increase of Ag3PO4 nanoparticles, the roughness of coatings increased (Ra and Rq for adding 7 wt% of Ag3PO4 coating was 29 and 293 nm). The wettability results demonstrated that the presence of 7 wt% Ag3PO4 nanoparticles in the coating has the highest water contact angle (152 °). Nano-scratch results proved that creating a pre-layer of PDMS can increase the scratch resistance of PDMS + TiO2+Ag3PO4 nanocomposite coating (displacement and scratch coefficient were 408 nm and 0.07μΝ-1/2 with the pre-layer). Corrosion current density of 316lSS with PDMS + TiO2+Ag3PO4 coating was 0.00045 μA/cm2, while for 316LSS with pure PDMS coating was 0.00114 μA/cm2 at 37 °C in PBS solution. The Nyquist curves showed the diameter of the semicircle for the nanocomposite coating was larger than pure PDMS coating, which indicates the higher corrosion resistance of the nanocomposite coating (5.98 × 107 Ω). By increasing Ag3PO4 nanoparticles from 1 to 7 wt%, the number of E. coli bacteria in contact with the nanocomposite decreased significantly from 580000 to 31000 CFU/cm2. In the disk diffusion test, the largest inhibition zone was related to the nanocomposite coating with the addition of 7 wt% Ag3PO4 (23 mm). Therefore, the PDMS + TiO2+Ag3PO4 nanocomposite coating has improved properties such as superhydrophobicity, advanced mechanical behavior, bio-corrosion resistance, and antibacterial activity.

Effect of Solvent on Superhydrophobicity Behavior of Tiles Coated with Epoxy/PDMS/SS

Superhydrophobic coatings are widely applied in various applications due to their water-repelling characteristics. However, producing a durable superhydrophobic coating with less harmful low surface materials and solvents remains a challenge. Therefore, the aim of this work is to study the effects of three different solvents in preparing a durable and less toxic superhydrophobic coating containing polydimethylsiloxane (PDMS), silica solution (SS), and epoxy resin (DGEBA). A simple sol-gel method was used to prepare a superhydrophobic coating, and a spray-coating technique was employed to apply the superhydrophobic coating on tile substrates. The coated tile substrates were characterized for water contact angle (WCA) and tilting angle (TA) measurements, Field-Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), and Fourier Transform Infrared Spectroscopy (FTIR). Among 3 types of solvent (acetone, hexane, and isopropanol), a tile sample coated with isopropanol-added solution acquires the highest water contact angle of 152 ± 2° with a tilting angle of 7 ± 2° and a surface roughness of 21.80 nm after UV curing for 24 h. The peel off test showed very good adherence of the isopropanol-added solution coating on tiles. A mechanism for reactions that occur in the best optimized solvent is proposed.

Superhydrophobic cotton fabrics coated by chitosan and titanium dioxide nanoparticles with enhanced antibacterial and UV-protecting properties

Superhydrophobic cotton fabrics were fabricated using chitosan/titanium dioxide (TiO₂) nanocomposites. Morphology results revealed that the fabric's surface was utterly coated by the nanoparticles leading to the formation of a highly packed nano-scale structure in the case of superhydrophobic coating. X-ray photoelectron spectroscopy results also proved that TiO₂ nanoparticles were highly adsorbed onto the fabric's top layer. Durability of the superhydrophobic coating was investigated by immersing the fabric into harsh solutions and also by subjecting the fabric to sonication. The results showed the high resistance of the superhydrophobic fabric against harsh conditions. The nanocomposite-coated fabrics were found to exhibit promising UV-protecting properties especially for the superhydrophobic fabric which showed around 80% enhancement in the UV protecting properties as compared with the uncoated fabric. The bacterial adhesion results revealed that the combination of chitosan and TiO₂ results in high antibacterial properties against E. coli and S. aureus bacteria. The bacterial reduction percentages were further increased to 99.8 and 97.3% against E. coli and S. aureus, respectively, once the superhydrophobic character was also induced to the fabrics. The developed nanocomposite coated fabrics exhibited promising potential to be used as antibacterial and self-cleaning garments in hospital-related applications.

Emphasizing the role of surface chemistry on hydrophobicity and cell adhesion behavior of polydimethylsiloxane/TiO2 nanocomposite films

Improving the bioinertness of materials is of great importance for developing biomedical devices that contact human tissues. The main goal of this study was to establish correlations among surface morphology, roughness and chemistry with hydrophobicity and cell adhesion in polydimethylsiloxane (PDMS) nanocomposites loaded with titanium dioxide (TiO₂) nanoparticles. Firstly, wettability results showed that the nanocomposite loaded with 30 wt.% of TiO₂ exhibited a superhydrophobic behavior; however, the morphology and roughness analysis proved that there was no discernible difference between the surface structures of samples loaded with 20 and 30 wt.% of nanoparticles. Both cell culture and MTT assay experiments showed that, despite the similarity between the surface structures, the sample loaded with 30 wt.% nanoparticles exhibits the greatest reduction in the cell viability (80%) as compared with the pure PDMS film. According to the X-ray photoelectron spectroscopy results, the remarkable reduction in cell viability of the superhydrophobic sample could be majorly attributed to the role of surface chemistry. The obtained results emphasize the importance of adjusting the surface properties especially surface chemistry to gain the optimum cell adhesion behavior.