Liquid-solid friction on crystalline surfaces: a perspective

Liquids flowing on solid surfaces experience a friction force. Whereas solid friction is familiar to anyone gifted with the sense of touch, liquid friction is much more exotic. Although it was long believed to be infinite, meaning that interfacial liquid molecules stick to solid surfaces, we have known for a few decades that this is not the case and that some materials show extreme liquid slippage, which implies a dramatic enhancement of nanoscale pipes' permeability to liquid flows. Harnessing liquid friction bears the promise of high-efficiency membrane separation processes, heat recovery systems, or blue energy harvesting, turning it into a highly strategic field to reduce carbon emissions and meet the climate emergency.