  In the field of nanoconfined fluids, there are striking examples of
deformation/transport coupling in which mechanical solicitation of the
confining host and dynamics of the confined fluid impact each other. While this
intriguing behavior can be potentially used for practical applications (e.g.
energy storage, phase separation, catalysis), the underlying mechanisms remain
to be understood as they challenge existing frameworks. Here, using molecular
simulations analyzed through concepts inherent to interfacial fluids, we
investigate fluid flow in compliant nanoporous materials subjected to external
mechanical stresses. We show that the pore mechanical properties significantly
affect fluid flow as they lead to significant pore deformations and different
density layering at the interface accounted for by invoking interfacial viscous
effects. Despite such poromechanical effects, we show that the thermodynamic
properties (i.e. adsorption) can be linked consistently to Darcy's law for the
permeability by invoking a pore size definition based on the concept of Gibbs'
dividing surface. In particular, regardless of the pore stiffness and applied
external stress, all data can be rationalized by accounting for the fluid
viscosity and slippage at the interface independent of a specific pore size
definition. Using such a formalism, we establish that the intimate relation -
derived using the linear response theory - between collective diffusivity and
hydraulic permeability remains valid. This allows for linking consistently
microscopic dynamics experiments and permeability experiments on fluid flow in
compliant nanoporous materials.
