  The zeta ($\zeta$) potential is a pivotal metric for characterizing the
electric field topology within an electric double layer - an important
phenomenon on phase interface. It underpins critical processes in diverse
realms such as chemistry, biomedical engineering, and micro/nanofluidics. Yet,
local measurement of $\zeta$ potential at the interface has historically
presented challenges, leading researchers to simplify a chemically homogenized
surface with a uniform $\zeta$ potential. In the current investigation, we
present evidence that, within a microchannel, the spatial distribution of
$\zeta$ potential across a chemically homogeneous solid-liquid interface can
become two-dimensional (2D) under an imposed flow regime, as disclosed by a
state-of-art fluorescence photobleaching electrochemistry analyzer (FLEA)
technique. The $\zeta$ potential' s propensity to become increasingly negative
downstream, presents an approximately symmetric, V-shaped pattern in the
spanwise orientation. Intriguingly, and of notable significance to chemistry
and engineering, this 2D $\zeta$ potential framework was found to
electrokinetically induce swirling flows in tens of nanometers, aligning with
the streamwise axis, bearing a remarkable resemblance to the well-documented
hairpin vortices in turbulent boundary layers. Our findings gesture towards a
novel perspective on the genesis of vortex structures in nanoscale.
Additionally, the FLEA technique emerges as a potent tool for discerning
$\zeta$ potential at a local scale with high resolution, potentially
accelerating the evolution and applications of novel surface material.
