Microbial interaction with micrometer-scale wrinkled surfaces subjected to fluid shear

Surface properties influence bacterial adhesion, which is the first step towards colonization and biofilm formation. For implantable devices, biofilm-associated infections are the most common clinical complications, given their resistance against mechanical stress and antibiotics; therefore, it becomes of paramount importance to designing surfaces able to prevent or reduce bacterial colonization.

In this work, we aim to characterize the near-surface microfluidic environment on patterned surfaces and its correlation with the initial settlement of microorganisms in a newly developed methodology referred as "microfluidic wrinling". Specifically, we investigate the effect of micrometer-scale wrinkled topographies, subjected to fluid shear in microfluidic devices, on the initial attachment of motile and non-motile P. aeruginosa bacterial strains on sinusoidal (1D) patterns fabricated by wrinkling of plasma-oxidized polydimethylsiloxane (PDMS) bilayers contrasted with flat (F), unpatterned PDMS surfaces. To characterize the combined effect of topography and fluid shear, 1D patterned surfaces were oriented according and in opposition to the direction of the fluid flow. Significantly, the presence of a periodic, non linear topography, is affecting the local near-interface shear stress field generating stress concentration points able to impede the spatial arrangement of bacteria, unless an optimal contact surface area is developed. This effect delays bacterial initial attachment and proliferation, especially on non-motile species. Moreover, increasing the shear rate enables a "shear-detachment" mechanism opposed to flat surfaces, where proliferation increases with shear rate.

Our findings suggest an effective framework to rationalize the impact of prescribed surface topography and fluid shear to delay and frustrate the early stages of bacterial proliferation.