Strömingsström

Strömingsström, commonly translated as streaming current, is an electrokinetic phenomenon in which a pressure-driven flow of an electrolyte through a confined, charged channel carries ions from the electrical double layer along the channel, generating an electric current within the liquid. It occurs in systems such as capillaries, porous media, and microfluidic channels with surface charge.

Mechanism and dependencies: A solid surface in contact with an electrolyte forms an electrical double layer consisting of a compact layer and a diffuse layer. When the fluid is driven by pressure, ions in the diffuse layer are convected with the flow, producing a net current. The magnitude of the streaming current depends on the surface charge (zeta potential), the ionic strength and composition of the solution, the channel geometry, the fluid viscosity, and the applied pressure difference.

Relation to streaming potential: The streaming current is the current generated inside the fluid due to convective ion transport. If the channel ends are electrically connected, the current flows through the external circuit; if the circuit is open, an electric potential difference, the streaming potential, develops between the ends as charges redistribute to balance currents.

Applications and theory: Strömingsström is used in microfluidics and analytical chemistry to characterize surface charge and zeta potential, and to study fluid–electrokinetic interactions in confined geometries. The phenomenon is described by electrokinetic theory, combining the Navier–Stokes equations with Poisson–Boltzmann electrostatics; related concepts include electro-osmosis and the Helmholtz–Smoluchowski framework, as well as Onsager reciprocal relations linking streaming current and electro-osmotic flow.

See also: Streaming potential, zeta potential, electrokinetics, microfluidics.