Electrophoresis

Electrophoresis, phenomenon of the movement of electrically charged particles through a gas or liquid as a result of an electric field formed between electrodes immersed in the medium. In an emulsion of rubber latex in an aqueous medium, for example, the rubber droplets tend to acquire an electrical charge by adsorption of ions. If a voltage is applied between a pair of electrodes in the emulsion, the rubber particles migrate toward the electrode that has a charge opposite to their own. If this electrode has a particular shape, the rubber particles deposited on it will coalesce to form an article of this shape; this is the process by which surgical rubber gloves and other electroformed articles are manufactured. Similarly, many automotive parts are coated with paint by an electrophoretic deposition process. The Cottrell precipitator deposits smoke particles by electrophoresis on an electrode mounted in a smokestack, thus reducing their emission into the atmosphere. If the suspended particles migrate toward the cathode, the negative electrode, the process is termed cataphoresis; if they migrate toward the anode, the positive electrode, it is called anaphoresis. Electroosmosis is a related phenomenon in which the solid phase is held immobile, and the liquid migrates because of the imposed electric field.

See also Chemical Reaction; Electroplating.