(546h) Correlations between Bacterial Adhesion and Surface Roughness and Topography

Bacterial adhesion is a critical biophysical process responsible for numerous human and animal infections, as well as bacterial diseases of plants. Furthermore, bacterial fouling is responsible for the deterioration of functional surface coatings applied to industrial equipment, the failure and breakdown equipment, and energy waste due to inefficiencies during various types of transport processes. The combination represents a huge economic burden globally. In this work, we test the hypothesis that the direct correlations between surface roughness parameters and bacterial adhesion. For this purpose, we systematically investigated the effect of surface roughness on bacterial adhesion at differing length scales spanning from ~2 nm to ~390 nm using methylated quartz substrates. Furthermore, the surface energy integration (SEI) method was implemented to model the DLVO interactions between bacteria and substrates with systematically varying roughness to gain insights into the energetics of bacterial adhesion. Experimentally, it was found that for a given bacteria type, culture condition, and surface chemistry; the number of adhering bacteria demonstrated up to a 75-fold variation dependent on surface roughness, indicating the significance of the surface topography to bacterial adhesion. For the cases the combination of surface roughness and methylation lead to hydrophobic wetting behavior, both increased effective surface area with increasing roughness and decreased activation energy with increased surface roughness was concluded to enhance the extent of bacterial adhesion. For the cases of superhydrophobic surfaces, the combination of factors including (i) the surpassing of Laplace pressure force of interstitial air over bacterial adhesive force, (ii) the reduced effective substrate area for bacteria wall due to air gaps to have direct/solid contact, and (iii) the reduction of attractive van der Waals force that holds adhering bacteria on the substrate (the energy barrier of bacterial desorption/removal). Overall, new insights into the effect of surface roughness and nanostructure on bacterial adhesion is significant in the context of designing new antifouling coatings and systems and explaining variations in bacterial contamination and biofilm formation processes on real/engineering surfaces with nonzero roughness.