Graphene-oxide (GO) membranes are excellent candidates for next generation nanofiltration and desalination membranes because of ultrahigh water flux, high ionic rejection rate, chemical and thermal robustness, scalability and low-production costs. Those membranes are made of a random percolation network of graphene nanocapillaries whose dimensions are determined by the size of GO flakes and by the functional groups attached both at their edges and in-plane. In this project, we will fabricate nanochannels and nanopores made of graphene oxide flakes functionalized with different chemical groups and well-defined geometry. The nanofluidic characterization of those well-defined nanocavities will provide us with insights to better understand the physics of ionic transport in GO membranes and help us improve in their design for industrial applications.