Slippery to Sticky Transition of Hydrophobic Nanochannels.

Contrary to common intuition that hydrophobic surfaces trivially cause water to slip, we discover a slippery-to-sticky transition in tunable hydrophobic nanochannels. We demonstrate this remarkable phenomenon by bringing out hitherto unveiled interplay between ion inclusions in the water and the interfacial lattice configuration over molecular scales. The consequent alterations in frictional characteristics illustrate that so-called hydrophobic nanochannels can be switchable to manifest features that are otherwise typically associated with hydrophilicity, causing water to stick. Our proposition may bear immense consequences toward fluidically functionalizing a hydrophobic interface without necessitating elaborate surface treatment techniques, bringing in far-ranging implications in diverse applications ranging from nature to energy.