Graphene oxide (GO) is being explored as a potential nanofiltration NF) membrane. Current hypotheses on ion permeation pathways in GO membranes ignore its hierarchical microstructure. In this study, both nanochannels and voids are thermally tuned and their relative contributions to ion permeation are studied using electro-impedance spectroscopy. It was observed that permeation resistance increases despite the increase in number of voids and therefore confirm the dominant role of nanochannels in permeation. Commercially available NF membranes are typically operated under a pressure differential and hence it is important to examine the behaviour of GO under a pressure differential and thus under strain. In order to do this, a device was developed, which could both apply a strain and measure the permeation properties in-situ. This device was validated with Nafion membrane. GO membranes were then studied in the developed instrument, and it was found that a small strain was sufficient to impact the ion permeation resistance of the membrane.