  We experimentally investigate the dynamics of capillary-driven flows at the
nanoscale, using an original platform that combines nanoscale pores and
microfluidic features. Our results show a coherent picture across multiple
experiments including imbibition, poroelastic transient flows, and a
drying-based method that we introduce. In particular, we exploit extreme drying
stresses - up to 100 MPa of tension - to drive nanoflows and provide
quantitative tests of continuum theories of fluid mechanics and thermodynamics
(e.g. Kelvin-Laplace equation) across an unprecedented range. We isolate the
breakdown of continuum as a negative slip length of molecular dimension.
