Fast Femtosecond Laser Processing of Stainless Steel for Slippery Liquid-Infused Surfaces

Abstract

Over last years, Slippery Liquid Infused Surfaces (SLIS) have demonstrated their great potential in numerous applications, notably to ease dairy fouling removal onto stainless steel substrates. However, the major drawback remains the lubricant retention in real application conditions (outside the laboratory), in particular under high shear stress, decreasing the fouling-release properties of SLIS. To improve the lubricant retention, an optimization of the stainless physical texturation was performed thanks to fast femtosecond laser process. Different structures (grid-like or maze-like) more or less deep (Rv ≈ 9 – 15 µm) were obtained by varying the laser fluence, scanning speed and overlapping rate. These structured were then chemically modified and impregnated with a fluorinated oil to obtain SLIS. To assess the lubricant retention under high shear stress, SLIS samples were placed in a pilot dairy processing line and submitted to a 60 min-pasteurization run followed by a 20 min-rinsing, where the foulant solution and the hot water were circulated over SLIS at a flow rate of 300 L/h. Our results show that surfaces structured by fast femtosecond laser process at 75 mm/s with an overlapping rate higher than 20% revealed a good retention rate (higher than 75%).

Keywords: SLIS, Femtosecond laser, Process optimization, Fouling-release, Food application