Biofilm liquid-repellence

Bacterial biofilm is one of the most resilient life forms; as multicellular communities encased in a slime-like matrix, biofilms coat the surfaces of everything from teeth to pipes and are impervious to nearly every type of biocide. How they resist antimicrobial compounds differing vastly in chemistry and mechanism has remained a troubling mystery despite decades of research. By looking at biofilms from a materials perspective rather than a biochemical or cellular one, we have discovered that their outer casing is remarkably liquid-repellent: liquids bead up on the surface and never spread on or enter the matrix to reach the bacteria in the first place. In addition to providing much-needed insight into how to combat harmful biofilms, this discovery represents the first time such broad liquid repellence has been seen anywhere in nature. Lotus leaves and several other organisms are highly water-repellent, but biofilm also repels a wide range of organic liquids such as ethanol and acetone that spread easily on other natural as well as synthetic surfaces. The key may be the unique composition and structure of the biofilm’s surface: the biofilm coating is a meshwork of protein and polysaccharide fibers that creates a complex multiscale topography. We are looking further into the chemical and mechanical features that give this surface its remarkable properties, and are using it as a model system to design bioinspired broadly repellent surfaces.