  Graphene flow sensors hold great prospects for applications, but also
encounter many difficulties, such as unwanted electrochemical phenomena, low
measurable signal and limited dependence on the flow direction. This study
proposes a novel approach allowing for the detection of a flow
direction-dependent electric signal in aqueous solutions of salts, acids and
bases. The key element in the proposed solution is the use of a reference
electrode which allows external gating of the graphene structure. Using
external gating enables to enhance substantially the amplitude of the
flow-generated signal. Simultaneous measurement of the reference electrode
current allows us to recover a flow-direction-sensitive component of the
flow-induced voltage in graphene. The obtained results are discussed in terms
of the Coulomb interaction and other phenomena which can be present at the
interface of graphene with the aqueous solution.
