Magnetohydrodynamic aggregation of cholesterol and polystyrene latex suspensions

Kenneth W. Busch, Sethuraman Gopalakrishnan, Marianna A. Busch, Etelka Tombácz

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27 Citations (Scopus)


The aggregation state of flowing (0.49 m s-1 linear velocity) colloidal dispersions of polystyrene latex microspheres (certified particle diameter of 156 ± 6 nm; measured diameter, 156 ± 3 nm at pH 5.3 in 50 mM NaCl) in NaCl solution and cholesterol (measured diameter, 533 ± 9 nm at pH 5.3), stabilized in NaCl solution by sodium taurodeoxycholate, was studied using photon correlation spectroscopy. For cholesterol suspensions having electrolyte concentrations close to the critical coagulation concentration (50 mM NaCl), pronounced aggregation was observed after 15 to 30 min of recirculation in the presence of an orthogonally appled magnetic field (2.0, 1.0 and 0.15 T). In all experiments with cholesterol, aggregation was followed by a period of deaggregation, after which aggregation again occurred. Comparable effects were not observed when cholesterol suspensions were recirculated in the absence of the magnetic field or when the suspensions were exposed to an equivalent magnetic fleld in the absence of flow. For cholesterol suspensions, the increase in particle size was most pronounced at 0.15 and 1.0 T rather than at 2.0 T. Aggregation effects were also observed when suspensions of polystyrene latex in 200 mM NaCl were made to flow through a 1.0-T field. In both systems, the magnetic aggregation does not appear to involve direct interaction between the field and the solid phase, but is interpreted in terms of orthokinetic effects involving magnetohydrodynamic changes in the flow profile resulting from the presence of the transverse field.

Original languageEnglish
Pages (from-to)528-538
Number of pages11
JournalJournal of colloid and interface science
Issue number2
Publication statusPublished - Nov 10 1996


  • aggregation state
  • colloidal cholesterol
  • colloidal latex
  • magnetohydrodynamics
  • orthokinetic effects
  • photon correlation spectroscopy

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry

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