Effect of Ageing on the Structure and Properties of Model Liquid-Infused Surfaces

Abstract

Liquid-infused surfaces (LISs) exhibit unique properties that make them ideal candidates for a wide range of applications, from antifouling and anti-icing coatings to self-healing surfaces and controlled wetting. However, when exposed to realistic environmental conditions, LISs tend to age and progressively lose their desirable properties, potentially compromising their application. The associated ageing mechanisms are still poorly understood, and results reflecting real-life applications are scarce. Here, we track the ageing of a model LIS composed of glass surfaces functionalized with hydrophobic nanoparticles and infused with silicone oil. The LISs are fully submerged in aqueous solutions and exposed to acoustic pressure waves for set time intervals. The ageing is monitored by periodic measurements of the LIS's wetting properties. We also track the changes to the LIS's nanoscale structure. We find that the LISs rapidly lose their slippery properties because of a combination of oil loss, smoothing of the nanoporous functional layer, and substrate degradation when directly exposed to the solution. The oil loss is consistent with water microdroplets entering the oil layer and displacing oil away from the surface. These mechanisms are general and could play a role in the ageing of most LISs.

Life and death of liquid-infused surfaces: a review on the choice, analysis and fate of the infused liquid layer

“…25 μm to 5 μm. 145 On a thick film (e.g. thicker than about 1 µm), the dynamic and static regimes of wetting are not affected by the exact lubricant film thickness.…”

Potential biofilm control strategies for extended spaceflight missions

“… Promising initial trials, long term use is not apparent. Slippage coatings (Lubricant-Impregnated Surfaces) [ [95] , [96] , [97] ] Strategy is to reduce strength of adhesion of microorganisms to surface to promote detachment Promising in initial trials with marine systems (ships) and long-term seawater immersion Mechanical durability concerns as materials can be prone to shear forces. Alterations of surface topography [ 98 , 99 ] Several microscale alterations of surface topography (including shark skin similarities).…”

“…In this technology a surface is roughened so that it can promote adhesion to a lubricating fluid. The lubricating fluid typically is immiscible with the liquid containing the microorganisms [ 97 ] so that it remains associated with the surface. LIS have shown promise in biofilm prevention in P. aeruginosa during lab culture [ 96 , 109 ] and the prevention of biofilm-associated mineral deposition [ 110 ].…”

“…Recent investigations by Goodband et al. [ 97 ] showed that smoothing of the textured surface and loss of the oil lubricant diminished the effectiveness of LIS during prolonged use. There is an ongoing study currently underway on the ISS to investigate biofilm formation on different materials including LIS under microgravity conditions [ 22 ].…”

“…[ 115 ]). However, the chemical and physical stability of prospective coatings may change over a prolonged period of time and diminish effectiveness [ 97 ]. Marine fouling is a global concern for shipping, and antifouling longevity and control mechanisms historically employed a variety of toxic, biocide-based antibiofouling compounds including tributyl tin and more recently copper- and zinc-based coatings [ 87 ].…”