State-dependent friction for a moving liquid contact line over rough solid surfaces

Caishan Yan; Penger Tong; Qin Xu

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arXiv · 2503.03118

State-dependent friction for a moving liquid contact line over rough solid surfaces

Caishan Yan·Penger Tong·Qin Xu

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Abstract

Solid friction between two rough surfaces is often observed to increase logarithmically over time due to contact creeping. An intriguing question is whether a similar aging effect occurs in contact line (CL) friction over rough substrates. Here, we report a systematic experimental study of CL friction using a hanging-fiber atomic force microscope (AFM) to measure the frictional force as a liquid CL moves across a fiber surface with different coatings under a well-controlled time protocol. State- (or time-)dependent CL friction is observed for the fiber surface with different textures in both the advancing and receding directions. The experimental findings are explained by a phenomenological model that links mesoscale CL friction to the microscopic relaxation of metastable air bubbles or liquid droplets trapped in the interstices of a rough surface. This model offers a general aging mechanism relevant to a wide range of liquid-solid interfaces.

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Caishan Yan, Penger Tong, Qin Xu. 2025-03-05. State-dependent friction for a moving liquid contact line over rough solid surfaces. https://arxiv.org/abs/2503.03118

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