Surface characteristics influencing bacterial adhesion to polymeric substrates

Superhydrophobic surfaces have been reported to reduce bacterial adhesion, but interactions between bacterial media and solid surfaces at the interface have rarely been associated with the solid area fraction (f) from the Cassie-Baxter wetting state. This study aimed to investigate the effective surface area for bacterial adhesion by analyzing the solid area fraction of surfaces where the bacterial medium is in contact with a solid surface. Also, the self-cleaning ability of the superhydrophobic surface against adhered bacteria was examined. The influences of roughness, surface energy, entrapped air, and surface charge of substrate materials on bacterial adhesion were examined, and the critical surface characteristics that are conducive to reducing Escherichia coli adherence to polymeric surfaces were determined. Moderate hydrophobicity with water contact angle of about 90° produced the highest level of bacterial adhesion. Entrapped air at the interface of superhydrophobic surfaces interfered with the direct contact of bacteria to solid surfaces, leading to less bacterial adhesion. The superhydrophobic surface with a reduced solid area fraction displayed self-cleaning ability, where initially-adhered bacteria were removed by washing. The superhydrophilic substrate with negative zeta potential exhibited limited bacterial binding, due to the reduced hydrophobic interaction and possible repulsive interaction between bacteria and surface. The findings of this study can be utilized for an effective surface design to circumvent bacterial adhesion as an alternative solution to using antibiotics.