Interfacial Energy Analysis of Lubricant Stability and Anti-Biofouling Performance of Slippery Liquid-Infused ZnO Nanostructured Surfaces

This paper investigated the lubricant stability and anti-biofouling performance on slippery liquid-infused nanostructured surfaces (SLIPSs) using thermodynamic and interfacial energy analyses. ZnO nanorods were synthesized on indium tin oxide substrates with and without a ZnO seed layer by electrochemical deposition and subsequently infused with PDMS-based silicone oil. The seed-layer-assisted growth produced densely packed and vertically aligned ZnO nanorods. Interfacial energy analysis showed that the resulting SLIPSs satisfied the criterion for resistance to water-induced lubricant displacement (ΔE₂ = 64.14 mJ·m⁻²), indicating effective lubricant retention, whereas non-seeded surfaces exhibited reduced lubricant stability. Consistent with this prediction, the seed-layer-assisted SLIPSs retained droplet mobility following spin testing at 2500 rpm, although the reduced sliding velocity indicated a decline in slippery performance. Anti-biofouling evaluation using Escherichia coli (XL1-Blue) revealed that the SLIPSs effectively suppressed bacterial attachment, reducing surface coverage to below 0.3% after 24 h of incubation. In comparison, the pristine ITO and ZnO nanorods exhibited values of 50.8% and 54.6%, respectively. Subsequent surface free energy analysis demonstrated that lubricant infusion reduced the work of adhesion to 77.92 mJ·m⁻². These findings provide insight into the interfacial interactions governing lubricant retention and bacterial attachment on SLIPSs.