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Colloid vibration current is an electroacoustic phenomenon that arises when ultrasound propagates through a ISO International Standard 13099, Parts 1,2 and 3, “Colloidal systems – Methods for Zeta potential determination", (2012)
/ref> Dukhin, A.S. and Goetz, P.J
"Characterization of liquids, nano- and micro- particulates and porous bodies using Ultrasound"
Elsevier, 2017 The pressure gradient in an ultrasonic wave moves particles relative to the fluid. This motion disturbs the double layer that exists at the particle-fluid interface. The picture illustrates the mechanism of this distortion. Practically all particles in fluids carry a
Colloid vibration current is an electroacoustic phenomenon that arises when ultrasound propagates through a fluid
In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...
that contains ions and either solid particles or emulsion droplets./ref> Dukhin, A.S. and Goetz, P.J
"Characterization of liquids, nano- and micro- particulates and porous bodies using Ultrasound"
Elsevier, 2017 The pressure gradient in an ultrasonic wave moves particles relative to the fluid. This motion disturbs the double layer that exists at the particle-fluid interface. The picture illustrates the mechanism of this distortion. Practically all particles in fluids carry a
surface charge
Surface charge is a two-dimensional surface with non-zero electric charge. These electric charges are constrained on this 2-D surface, and surface charge density, measured in coulombs per square meter (C•m−2), is used to describe the charge di ...
. This surface charge is screened with an equally charged diffuse layer; this structure is called the double layer. Ions of the diffuse layer are located in the fluid and can move with the fluid. Fluid motion relative to the particle drags these diffuse ions in the direction of one or the other of the particle's poles. The picture shows ions dragged towards the left hand pole. As a result of this drag, there is an excess of negative ions in the vicinity of the left hand pole and an excess of positive surface charge
Surface charge is a two-dimensional surface with non-zero electric charge. These electric charges are constrained on this 2-D surface, and surface charge density, measured in coulombs per square meter (C•m−2), is used to describe the charge di ...
at the right hand pole. As a result of this charge excess, particles gain a dipole moment. These dipole moments generate an electric field that in turn generates measurable electric current. This phenomenon is widely used for measuring zeta potential in concentrated colloids.
See also
* Electric sonic amplitude * Electroacoustic phenomena * Interface and colloid science * Zeta potentialReferences
Chemical mixtures Colloidal chemistry Soft matter {{CMP-stub