Temperature-dependent slip length for water and electrolyte solution

The temperature dependence of boundary slip at liquid-solid interface is critical both for the fundamental theory and applications of fluid mechanics on micro and nanoscale, such as sustainable cooling of electronic devices. However, there is a controversy on the temperature dependence of boundary slip which lacks experimental evidence, we aim to resolve it by hypothesizing that the temperature dependent slip length depends on the variation in the interfacial energy barrier.

Here, we measured l_s - T relation of water and NaCl solution on self-assembled FDTS (Perfluorodecyltrichlorosilane) surface using colloidal probe AFM. The transition of l_s - T monotonicity is found. For water and 0.1 M NaCl solution, l_s is negatively correlated with T, while for 1 M NaCl solution, l_s is positively correlated with T.

Together with molecular dynamics simulations, such observation is quantitatively explained with an analytical model based on rate theory, where the l_s - T monotonicity depends on the difference between liquid-solid interfacial energy barrier and liquid internal energy barrier. Our results provide not only solid experimental evidence for the boundary slip being a rate process, but also a basis for the thermal-hydrodynamic design of microfluidic and nanofluidic devices.