The rheology of graphene oxide dispersions in confined geometries

Dispersions of high aspect ratio 2D nano-particles have seen a huge increase in research interest over the past decade, especially in the context of ink formulations for printed electronics. So far the rheology of these dispersions has only been measured in bulk. For inkjet applications, however, it is crucial to understand the flow properties in confined geometries with dimensions of ~10-100 particle diameters.  This work focuses on graphene-oxide particles (GO) with an aspect ratio (lateral size/thickness) of ~15000 dispersed in water. Optical coherence tomography is used to non-invasively measure the velocity profile of these suspensions in microchannels at different pressure drops. We study how confinement changes the flow properties and microstructure of these suspensions compared to the bulk rheology for a wide range of concentrations.