Fabrication of a superhydrophobic cotton fabric with efficient antibacterial properties and asymmetric wettability via synergistic effect of quaternized chitosan/TiO2/Ag

A superhydrophobic cotton fabric with unidirectional moisture transfer ability, antibacterial, and oil-water separation capabilities was fabricated by combining a simple coating method and oxygen plasma etching. Polydimethylsiloxane (PDMS) was employed to impart low surface energy to the cotton fabric, thereby endowing it with hydrophobic characteristics. The synthesized quaternized chitosan/TiO2/Ag (CTA) compound was subsequently applied onto the cotton fabric surface to introduce a desirable level of surface roughness, thus enhancing its hydrophobic properties and conferring excellent antibacterial efficacy. The cotton was subsequently treated by oxygen plasma to trigger asymmetrical wetting on both sides. The experimental findings reveal that the optimally treated cotton fabric exhibits hydrophobic properties on the bottom surface, with a water contact angle (WCA) reaching 162.8°, while the upper surface displays hydrophilic behavior, establishing a wetting gradient along the thickness direction. Notably, even under the influence of reverse gravity, water droplets are capable of transferring from the back to the top surface within 2 s, while preventing reverse penetration of liquid. Moreover, the synthesized compound CTA endows the cotton fabric with efficient and long-lasting antibacterial properties through two modes (contact and release sterilization modes) and three sterilization mechanisms (electrostatic interaction, plasma surface resonance effect, and reactive oxygen species). Remarkably, within a time frame of only 1 h, the modified cotton fabric is able to achieve a kill rate exceeding 99% against Escherichia coli and Staphylococcus aureus. Moreover, the aforementioned properties demonstrate outstanding durability against repeated washing, continuous abrasion, exposure to strong acid/base, and ultraviolet radiation. Additionally, this modified cotton fabric exhibits remarkable efficiency in terms of oil-water separation, effectively separating both light and heavy oil from water. It is worth noting that the preparation process is cost-effective, environmentally friendly, and free from fluorine.