Liquid food mobility on anti-biofouling liquid infused surfaces

Abstract

Adhesion of liquid foods to packaging containers remains a persistent challenge causing significant wastage of food. Modifying packaging surfaces inspired from the pitcher plant, such as Liquid-Infused Surfaces (LIS), offer a promising solution due to their liquid-repellency property. This work analyses velocity of liquid food drops on LIS as the lubricant viscosity is varied. It further assesses the surfaces for their durability for drop and bulk flow. 2D pillars with Laser Induced Periodic Surface Structures (LIPSS) were fabricated using a femtosecond laser setup. Three lubricant viscosities (5, 20, 100 cSt) were considered to evaluate LIS for each of the five liquid foods: honey (Newtonian) and cold coffee, mango juice, ketchup and Yogurt, which exhibit shear-thinning behaviour. The critical sliding angle responsible for the onset of the motion was less than 32°for all the liquids. The drop velocity of the shear-thinning liquids was reduced by almost ten times as the lubricant viscosity was increased twenty times. In contrast, honey (Newtonian) exhibited a marginal increase in velocity as the lubricant viscosity was increased. Furthermore, the durability tests reveal an increase in the number of liquid drops shed as the lubricant viscosity is increased. Immersion tests after 25 cycles showed little to no residue for the most viscous lubricant, while the two lower-viscosity lubricants, honey, ketchup, and Yogurt, had moderate residues. The results indicate a strong affinity towards the application of a more viscous lubricant in terms of LIS performance and durability. Finally, the LIS exhibited successful repellency to E coli bacteria. This study hopes to support the robust design of LIS in liquid food packaging applications that potentially can be extended to cosmetic and pharmaceutical industries that often use liquids in packaging applications. © 2025 Elsevier B.V., All rights reserved.