  We explore the dependence of electrical transport in a graphene field effect
transistor (GraFET) on the flow of the liquid within the immediate vicinity of
that transistor. We find large and reproducible shifts in the charge neutrality
point of GraFETs that are dependent on the fluid velocity and the ionic
concentration. We show that these shifts are consistent with the variation of
the local electrochemical potential of the liquid next to graphene that are
caused by the fluid flow (streaming potential). Furthermore, we utilize the
sensitivity of electrical transport in GraFETs to the parameters of the fluid
flow to demonstrate graphene-based mass flow and ionic concentration sensing.
We successfully detect a flow as small as~70nL/min, and detect a change in the
ionic concentration as small as ~40nM.
