SHORT INTRODUCTION TO ELECTRO ACOUSTIC THEORY

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Electroacoustic effects are result of coupling between acoustic and electric fields. Debye realized 70 years ago [1] that in the presence of a longitudinal sound wave, any differences in the effective mass or friction coefficient between anions and cations would result in different displacement amplitudes. In turn, this difference in displacement would create an alternating electric potential between points within the solution. Indeed, this phenomenon is measurable and can yield useful information about the properties of ions. It is usually referred to as an “Ion Vibration Potential” (IVP). It was used for measuring sizes of ions in 60th. Sadly, this phenomenon has been largely forgotten, and virtually all of the interest in electroacoustic phenomena has shifted from pure electrolyte solutions to colloids

However, the first electroacoustic theory was developed for a third class of systems – porous bodies, in 1944 by Frenkel [2]. He created theory of electroseismic effect using Smoluchowski theory as a starting point. We use this effect now for studying porous bodies with DT-300 Zeta Potential probe.

First electroacoustic measurements in colloids were performed by Hermans [3] and Rutgers [4] in 1938. Enderby and Booth [5,6] developed the first theory for CVP in the early 1950’s.

Detail historical review of all developments on the field of electroacoustics can be found in our book [7].

Here we present just one very useful expression for Colloid Vibration Current derived by V. Shilov and oth. [8] using a well-known Onsager reciprocal relationship for Smoluchwski type electrokinetic theory:

ELECTRO

where ε is dielectric permittivity, η is viscosity, ρ is density, φ is volume fraction, ζ is zeta potential. Index p corresponds to particle, m to media, s to the system in whole.

This equation is very useful for estimating trend of electroacoustic change depending on various parameters. It is valid quantitatively for submicron particles with sizes under 300 nm with thin double layer and negligible surface conductivity. Double layers must be not overlapped, which somewhat restricts volume fraction for a given particle size.

  • Debye, P. “A method for the determination of the mass of electrolyte ions”, J. Chem. Phys., 1,13-16, (1933)

  • Frenkel J. “On the Theory of Seismic and Seismoelectric Phenomena in a Moist Soil”, re-published, J. Engineering Mechanics, 131, 9, pp. 879-887 (2005). http://cedb.asce.org/cgi/WWWdisplay.cgi?0527243
  • Hermans, J., Philos. Mag., 25, 426 (1938)

  • Rutgers, A.J. and Rigole, W. “Ultrasonic vibration potentials in colloid solutions, in solutions of electrolytes and pure liquids”, Trans. Faraday Soc., 54, 139-143 (1958)

  • Enderby, J.A. “On Electrical Effects Due to Sound Waves in Colloidal Suspensions”, Proc. Roy. Soc., London, A207, 329-342 (1951)

  • Booth, F. and Enderby, J. “On Electrical Effects due to Sound Waves in Colloidal Suspensions”, Proc. of Amer. Phys. Soc., 208A, 32 (1952)

  • Dukhin A.S. and Goetz, P.J. “Ultrasound for characterizing colloids”, Elsevier, 2002 http://books.google.com/books?q=+inauthor:%22Philip+J.+Goetz%2

  • Dukhin, A.S., Shilov, V.N, Ohshima, H., Goetz, P.J “Electroacoustics Phenomena in Concentrated Dispersions. New Theory and CVI Experiment”, Langmuir, 15, 20, 6692-6706, (1999) http://pubs.acs.org/doi/abs/10.1021/la991305y