  Liquid infused surfaces (LIS) exhibit unique properties that make them ideal
candidates for a wide range of applications, from anti-fouling and anti-icing
coatings to self-healing surfaces and controlled wetting. However, when exposed
to realistic environmental conditions, LIS 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 model
LIS composed of glass surfaces functionalized with hydrophobic nanoparticles
and infused with silicone oil. The LIS 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' wetting properties. We also
track changes to the LIS' nanoscale structure. We find that the LIS rapidly
lose their slippery properties due to 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 LIS.
