Effect of Pore Size, Lubricant Viscosity, and Distribution on the Slippery Properties of Infused Cement Surfaces

The fabrication of slippery liquid-infused porous surfaces (SLIPS) usually requires the use of structured substrates, with specifically designed micro- and nanoroughness and complementary surface chemistry, ideally suited to trap lubricants. It is not yet established whether a random roughness, with a range of pores with a variable size reaching deep into the bulk of the material, is suitable for successful infusion. In this study, a highly porous material with random and complex roughness, obtained by using portland cement (the most common type of cementitious material), was tested for its potential to act as a SLIP surface. Atomic force microscopy meniscus measurements were used to investigate the distribution of lubricants on the surface upon subsequent stages of depletion because of the capillary absorption of the lubricant within the porous structure. Factors such as curing time of the cement paste, time since infusion, and lubricant viscosity were varied to identify the conditions under which infusion could be considered successful. A sensitive method to evaluate the penetration of liquid (low-temperature differential scanning calorimetry) was used, which could be applicable to many porous materials. The optimized infusion of cement surfaces ultimately resulted in the desired hallmarks of SLIPS, that is, high water repellence and slipperiness, effective for several weeks, reduced water permeability, and icephobicity.