Non-Markovian Dynamics of Surface-Liquid Slip.

Surface-liquid slip is critical in nanofluidic and confined biological systems, where interfacial effects dominate. Slip is typically described by a Markovian Navier friction coefficient, which fails to capture nonstationary friction dynamics. Here, a recent generalization of the Navier friction coefficient for subnanometer length scales is extended to describe the time evolution of surface-liquid friction down to subpicosecond time scales by a Navier memory kernel. Such kernels are extracted from combined equilibrium and nonequilibrium molecular dynamics simulations of water adsorbed on chemically varied self-assembled monolayers (polar and nonpolar, fluorinated and nonfluorinated) and analyzed in the time and frequency domains. The Navier kernels exhibit spectral features associated with surface vibrational modes, revealing coupling between interfacial friction and substrate dynamics. A coupled damped harmonic oscillator model quantitatively reproduces key spectral features observed in the simulations. Our framework connects molecular-scale interfacial fluid dynamics with classical descriptions of slip, with broad implications for nanofluidics.