Elektroosmose

Elektroosmose is a phenomenon that occurs when a liquid moves through a porous material, a capillary tube, or a membrane under the influence of an applied electric field. This movement is driven by the interaction between the electric field and the charged surface of the material and the counter-ions in the liquid. When a voltage is applied across a charged surface immersed in a liquid, the mobile ions in the liquid that have the opposite charge to the surface are attracted towards it, forming an electric double layer. The electric field then exerts a force on these mobile ions, causing them to move. As these ions move, they drag the surrounding liquid with them, resulting in a bulk flow of the liquid.

The direction of the electroosmotic flow depends on the charge of the surface and the polarity of the applied electric field. If the surface is negatively charged, positive ions in the liquid will be attracted, and the flow will be in the direction of the negative electrode. Conversely, if the surface is positively charged, negative ions will be attracted, and the flow will be towards the positive electrode. The magnitude of the electroosmotic flow is influenced by factors such as the applied voltage, the properties of the liquid (viscosity, dielectric constant), the surface charge density of the material, and the pore size or geometry.

Elektroosmose finds applications in various fields. It is utilized in microfluidic devices for pumping and mixing fluids, in electrophoresis for separating charged molecules, and in water treatment processes for dewatering sludge and removing contaminants. It also plays a role in certain geological processes and biological systems. Understanding and controlling electroosmosis is crucial for optimizing the performance of these technologies.