Superhydrophobic, antibacterial, and EMI shielding properties of Ag/PDMS-coated cotton fabrics

In this study, three functionalities of superhydrophobicity, antibacterial activity and electromagnetic interference (EMI) shielding of cotton fabrics coated with Ag/PDMS were studied, and the role of coating composition was discussed. Special attention was paid to understanding the relationships between the surface roughness of coated fibres with the developed superhydrophobicity and antibacterial activity. The superhydrophobicity of fabrics was analysed based on water contact angle (WCA) and contact angle hysteresis (CAH) values while the antibacterial activity was tested against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. It was found that the surface roughness on fibres, which changed by altering the concentrations of Ag NPs (0.2-4 g/L) and PDMS (20 and 40 g/L), affected the obtained superhydrophobicity. The most superhydrophobic fabric (WCA 171(degrees)) was coated with a formulation containing Ag NPs (2 g/L), and PDMS (20 g/L), and had the highest surface roughness. Increasing the ingredients' concentrations, however, deteriorated the optimum roughness as measured using a 3D Surface Laser Scanning Microscopy method. The coated fabrics showed efficacy against both types of bacteria, and it was confirmed that the Ag NPs content was the key factor in determining the antibacterial performance. Moreover, testing the EMI shielding performance of fabrics demonstrated that increasing the concentrations of Ag NPs and PDMS both enhanced the reflection coefficient (R) of fabrics against incident X-band electromagnetic (EM) wave by around >500%, which was due to the deposition of a higher amount of Ag NPs on fabrics. The superhydrophobicity of fabrics was durable after 1000 abrasion cycles, and the fabrics retained their antibacterial activity even after numerous washings.