Anomalous friction of supercooled glycerol on mica
The fundamental understanding of friction of liquids on solid surfaces remains one of the key knowledge gaps in the transport of fluids. While the standard perspective emphasizes the role of wettability and commensurability, recent works have unveiled the crucial role of the solid's internal excitations, whether electronic or phononic, on liquid-solid dissipation. In this work, we take advantage of the considerable variation of the molecular timescales of supercooled glycerol under mild change of temperature, in order to explore how friction depends on the liquid's molecular dynamics. Using a dedicated tuning-fork-based AFM to measure the hydrodynamic slippage of glycerol on mica, we report a 2-order of magnitude increase of the slip length with decreasing temperature by only 30°C. However the solid-liquid friction coefficient is found to be a non monotonous function of the fluid molecular relaxation rate, fα, at odd with an expected Arrhenius behavior. In particular, the linear increase of friction with the liquid molecular rate measured at high temperature cannot be accounted for by existing modelling. We show that this unconventional and non-arrhenian friction is consistent with a contribution of the solid's phonons to the liquid-solid friction. This dynamical friction opens new perspectives to control hydrodynamic flows by properly engineering phononic and electronic excitation spectra in channel walls.