R. Chrostowski, F. Mangolini
The University of Texas at Austin,
United States
Keywords: liquid-infused surfaces, surface roughness
Summary:
Liquid-infused surfaces (LIS) have attracted considerable scientific and industrial interest as a promising class of surface materials capable of shedding impinging droplets, including both polar and non-polar solvents. While previously published studies evaluated the liquid-infusion of textured solid substrates with precisely ordered arrays of micro-pillars, the application of micro-textured surfaces in several sectors has been constrained by their limited scalability and lack of knowledge concerning how to optimize the surface geometry to better retain the infused liquid. Furthermore, the design guidelines for LIS systems that have been developed so far can only be applied to textured surfaces and cannot be extended to common, randomly rough surfaces with scale-dependent properties. Here, we establish links between scale-dependent surface roughness and liquid retention. To achieve this, we characterized the roughness of boehmite across different length scales on the basis of spectral analysis of atomic force microscope (AFM) images and then identified the length scale of surface roughness that determines the retention of two chemically similar perfluoropolyether lubricants with different radii of gyration. Finally, we predict and demonstrate, for the first time, divergent contaminant-repelling behavior for the two perfluoropolyether lubricants on the same boehmite substrate purely due to variations in surface roughness with scale. The outcomes of this work pave the way towards the development of scalable LIS systems to be used as anti-corrosion, anti-fouling, anti-icing, and self-healing coatings for a range of applications, from medical devices to heat exchangers.