Solid/liquid Interfaces (Prof. Szlufarska)

The nature of the solid/liquid interface has been a subject of a vigorous scientific debate for over a century. Prof. Szlufarska’s group combines computer simulation and theory to investigate the behavior of interfacial liquids and related phenomena, such as the surface wettability, liquid/solid friction, and hydrophobic interactions.  We use molecular simulations to validate our theories and as a means for discovery of new phenomena. For instance, we have developed a Green-Kubo relation to predict the liquid/solid friction in the limit of low shear rates from equilibrium molecular dynamics simulatons. This theory enables highly efficient calculations of friction and slip and it addresses an important challenge of molecular simulations, which is accessing experimentally relevant time scales. Our Green-Kubo relation has been validated in simulations for a wide range of liquids and interfaces. Other areas of Prof. Szlufarska’s research include development of theories of and friction as determined from quartz crystal microbalance experiments, exploration of the Brownian motion of particles near interfaces, and asymptotic behavior of such particles in the hydrodynamic limit. We also use atomistic and coarse-grained simulations to determine the molecular origins of hydrophobic interactions between molecules and surfaces as well as the effects of proximal charges on the hydrophobic interactions.

[13] K. Huang and I. Szlufarska, Friction and slip at solid/liquid interfaces in vibrational system, Langmuir 28, 17302-17312 (2012)
[14] K. Huang and I. Szlufarska, Green-Kubo relation for friction at liquid/solid interface,Phys. Rev. E, 89, 032119 (2014)


Fig.5: (Left) A new theory based on the linear response theory (Green-Kubo relation) has been developed to predict slip (or alternatively friction) at the liquid/solid interface directly from molecular simulations. Results of equilibrium molecular dynamics (EMD) simulations based on the new theory (open symbols) show an excellent agreement with values extrapolated from a series of non-equilibrium simulations (NEMD) (filled symbols). Different colors correspond to different types of liquids and bond strength on the horizontal axis corresponds to the strength of binding between the liquid molecules and the solid surface.(Right) DNA tethered to a surfaces of a model quartz crystal microbalance.