We discuss in this paper the nature of the friction generated as a drop glides on a textured material infused by another liquid. Different regimes are found, depending on the viscosities of both liquids. While a viscous drop simply obeys a Stokes-type friction, the force opposing a drop moving on a viscous substrate becomes non-linear in velocity. A liquid on an infused material is surrounded by a meniscus, and this specific feature is proposed to be responsible for the special frictions observed on both adhesive and non-adhesive substrates.
Armelle Keiser and Philipp Baumli equally contributed to this work.Lubricant-infused surfaces (LIS) make drops remarkably mobile. However, the dynamics of those drops proved to be subtle, due to the numerous phases at stake (lubricant, drop, solid texture, air). In this article, we highlight the role played by a feature specific to LIS, namely the "foot" of oil surrounding the drops and drawn by their surface tension. Consequently, viscous dissipation can be localized in four distinct regions, which we tune independently through various experimental set-ups. Despite this complexity, we evidence a universal scaling for the friction law and reconciliate recent results produced on this topic.
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