Injection moulded micro- and nanoscale textures enhance hydrophobicity without compromising microbial safety for reusable plastic packaging

• All textured surfaces increased hydrophobicity, potentially through a Cassie-Baxter wetting state. However, hydrophobicity decreased after repeated washing, particularly for samples washed with detergent. • Repeated washing altered both surface chemistry and roughness, with changes in wettability primarily driven by the combined effect of these two parameters. • Microbiological testing showed no significant reduction in E. coli or S. aureus adhesion or cell viability on textured surfaces compared with flat controls. • Importantly, repeated washing did not compromise microbial safety or increase bioburden accumulation, encouraging further investigation of textured polymer surfaces for reusable packaging under reuse-relevant conditions. Reusable packaging offers a promising route to reduce the environmental impact of single-use plastic, but its safety depends on effective sanitisation and control of bioburden across multiple use cycles. Micro- and nanoscale surface textures provide a non-chemical strategy to enhance liquid repellency and potentially reduce bioburden and microbial accumulation by tailoring surface topography and wettability. In this study, we injection moulded three surface textures ranging from the micro- to nanoscale on polypropylene (PP) and polybutylene terephthalate (PBT) using laser-modified steel tooling inserts. We evaluated their mouldability, wetting behaviour, antimicrobial performance, and durability under repeated washing. The patterns were successfully replicated on PP and partially on PBT, highlighting material-dependent challenges when moulding features at this scale. All textures increased surface hydrophobicity, with water contact angles values of > 120° and > 110° recorded for PP and PBT, respectively. However, surface textures did not reduce bacterial attachment or viability. Importantly, repeated washing altered surface roughness, chemistry and wettability but did not compromise microbial safety or increase bioburden. These findings advance our understanding of how engineered surface textures influence hydrophobicity and bioburden/microbial accumulation in reuse-relevant conditions, informing the design of textured polymer surfaces for applications where hygiene and material longevity are critical.