Colloid vibration current

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Colloid vibration current is an electroacoustic phenomenon that arises when ultrasound propagates through a fluid that contain ions and either solid particles or emulsion droplets .^[1].

The pressure gradient in ultrasound wave moves particles relative to the fluid. This motion disturbes double layer that exist on the particle-fluid interface. This picture illustrates mechanism of this distortion. Practically all particles in fluids cary surface charge. This surface charge is screened with equally charged duffuse layer. This structure is called double layer. Ions of the diffuse layer are located in the fluid. They can move with the fluid. Fluid motion relative to the particles drag this ions to one of the particles poles. On the picture it is the left hand side pole. As a result, there is an excees of negative ions in the vicinity of the left pole and excessive positive surface charge at the right pole. Particle gain dipole moment. These dipole moments generate electric field that in turn generates electric current. This current is measurable, as described in ref. 1. This phenomenon is widely used for measuring zeta potential in concentrated colloids.