Influence of boundary layer conditions and surface properties on bacterial interaction with indoor built surfaces.

Indoor surface contamination is a significant concern in high-activity spaces such as childcare facilities, where microbial particles can be easily transmitted through direct surface touch or resuspension into indoor air. This study investigated Corynebacterium sp. attachment and detachment behaviors on four representative indoor surface materials (carpet, wood, metal and glass) and characterized near-surface airflow fields using batch attachment experiment, centrifugal detachment experiment, and particle image velocimetry (PIV). Surface characteristics: roughness, contact angle, and porosity were measured. The attachment fraction increased with exposure time for all tested surfaces, with metal (∼0.59), followed by wood (∼0.48) and glass (∼0.36). Carpet generated two microenvironments: an outer-fiber with higher-velocity region and an inter-fiber with lower-velocity shelter region. Glass showed the most uniform near-surface flows while wood generated the most spatially heterogeneous velocity fields due to its topography and pore structure. Overall, these results indicate that microbial attachment and detachment on indoor surface materials are governed by complex interplay of surface physicochemical properties, contact time, and geometry-dependent conditions, with no single factor acting alone. Smooth, non-porous surfaces could reduce initial adhesion and provide more predictable resuspension behavior in high-touch and high-activity indoor spaces.