Hydrodynamic Slip in Nanoconfined Flows: A Review of Experimental, Computational, and Theoretical Progress

Nanofluidics has made significant impacts and advancements in various fields, including ultrafiltration, water desalination, biomedical applications, and energy conversion. These advancements are driven by the distinct behavior of fluids at the nanoscale, where fluid behaviors are affected or altered due to interactions with solid surfaces. A key challenge in nanofluidics is understanding hydrodynamic slip, a phenomenon where liquid flows past solid boundaries with a non-zero velocity, deviating from the classical no-slip boundary condition. This review consolidates experimental, computational, and theoretical efforts to elucidate the mechanisms behind hydrodynamic slip in nanoconfined flows. We evaluate essential experimental methodologies, including surface force apparatus, atomic force microscopy, and micro-particle image velocimetry, which have been instrumental in characterizing slip at the nanoscale. The review also discusses the contributions of molecular dynamics simulations, including both non-equilibrium (NEMD) and equilibrium (EMD) approaches, in modeling interfacial phenomena and slip behavior. Additionally, it explores the influence of factors such as surface wettability, shear rate, and confinement on slip, emphasizing the interaction between liquid structuring and solid-liquid interactions. Advancements made so far have uncovered more complexities in nanoconfined flows which have not been considered in the past, inviting more investigation to fully understand and control fluid behavior at the molecular level.