  We develop an exact method for computing Casimir forces and the power of
radiative heat transfer between two arbitrary nanostructured surfaces out of
thermal equilibrium. The method is based on a generalization of the scattering
approach recently used in investigations on the Casimir effect. Analogously to
the equilibrium case, we find that also out of thermal equilibrium the shape
and composition of the surfaces enter only through their scattering matrices.
The expressions derived provide exact results in terms of the scattering
matrices of the intervening surfaces.
