Imaging microflows and nanopore structures using hydrodynamic force microscopy

We report the three-dimensional profilometry of gas microflows and the two-dimensional mapping of fluid permeability through nanoporous substrates using hydrodynamic force microscopy (HFM). Using fluid drag from external flows as a contrast mechanism, HFM has mapped Poiseuille flow through ∼100 nm pores and has identified subsurface fouling unresolvable by conventional force microscopy. HFM demonstrates nanoscale spatial resolution and flow velocity resolution on the order of 1 cms, making it an attractive investigative tool for applications in separation science, microfluidics, and nanoporous materials.