Tailoring microbial response to stainless steel surfaces via electrolyte jet machining and electrodeposition

Electrolyte jet machining (EJM) and electrodeposition present unexploited opportunities for the manufacturing of multiscale structured surfaces. The present work assesses the morphology and antibacterial properties of textured and multiscale stainless steel surfaces produced by EJM with a new 50 mmx0.3 mm slit nozzle, as well as multiscale surfaces subject to electrodeposition with copper. Characterisation of the surface morphology obtained via EJM with various combinations of current density, machining time and groove spacing is performed to facilitate the selection of representative surfaces for bacterial retention tests. Higher current density with constant applied charge leads to lower surface roughness at constant scanning speed and greater groove depth and width under static conditions. Groove depth is proportional to machining time at constant current density, while a groove pitch of 1.05 mm is found to provide the optimum compromise between maximum groove depth and complete surface coverage. Microscale surface features are found to reduce Escherichia coli and Pseudomonas aeruginosa retention by up to 97% compared to untextured control surfaces, while larger grooves play a role in inhibiting bacterial attachment by inducing turbulence. The presence of copper agglomerates completely eliminates bacterial retention under the tested conditions. The developed process provides a flexible approach to tailoring surface properties for specific applications requiring antimicrobial properties.