Irrotationality of uniform electroosmosis

Steady electroosmotic flow of uniform liquids in uniform media is irrotational provided the electric double layers adjacent to surfaces are negligibly thin, the surfaces are non-conducting and impermeable, and the total pressure imposed at inlets and outlets is uniform. Because many microfluidic devices employing electroosmosis approximately satisfy these requirements, this ideal electroosmosis is a limiting case with considerable practical significance. In ideal electroosmosis, fluid motion follows current lines. Flow-fields have no Reynolds number dependence and are everywhere proportional to the electric field. Both fields may be obtained by a single solution of the Laplace equation. In this paper, we discuss these features of ideal electroosmotic flows and present particle-image derived velocity fields that confirm ideal flow conditions in glass microchannel networks.