Transport in droplet-hydrogel composites: response to external stimuli

Mohammadi, A ; Sharif University of Technology | 2015

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  1. Type of Document: Article
  2. DOI: 10.1007/s00396-014-3473-8
  3. Publisher: Springer Verlag , 2015
  4. Abstract:
  5. Determination of effective transport properties of droplet-hydrogel composites is essential for various applications. The transport of ions through a droplet-hydrogel composite subjected to an electric field is theoretically studied as an initial step toward quantifying the effective transport properties of droplet-hydrogel composites. A three-phase electrokinetic model is used to derive the microscale characteristics of the polyelectrolyte hydrogel, and the droplet is considered an incompressible Newtonian fluid. The droplet-hydrogel interface is modeled as a surface, which encloses the interior fluid. The surface has the thickness of zero and the electrostatic potential ζ. Standard averaging procedures are used to derive the effective governing equation for the current density that captures the macroscopic behavior. The results show that the polymer boundary condition has a modulating impact on the electrical conductivity, and the influence of the boundary condition decreases as the interior fluid viscosity increases. At the limit of the polymer’s no-slip boundary condition, the interior and exterior fluids’ viscosities, Brinkman screening length, and ionic strength have a significant impact on the conductivity. Interestingly, it should be possible to determine the ζ-potential for a droplet-hydrogel composite from measurements of the electrical conductivity with the aid of the formula derived for the conductivity. Finally, the theoretical study for determining the response of droplet-hydrogel composites to an imposed pressure gradient is undertaken, and it is found that the polymer boundary condition has a modulating impact on the response
  6. Keywords:
  7. Composite ; Hydrogel ; Boundary conditions ; Composite materials ; Drops ; Electric conductivity ; Electric fields ; Incompressible flow ; Newtonian liquids ; Effective transport properties ; Electrical conductivity ; Electrostatic potentials ; Imposed pressure gradient ; Incompressible Newtonian fluid ; No-slip boundary conditions ; Polyelectrolyte hydrogels ; Streaming current ; Droplet hydrogel composite ; Ion ; Nanocomposite ; Polyelectrolyte ; Polymer ; Unclassified drug ; Current density ; Electric current ; Electric potential ; Ion current ; Ion transport ; Ionic strength ; pressure gradient ; Priority journal ; Static electricity ; Stimulus response ; Surface property ; Theoretical study ; Transport kinetics ; Viscosity ; Zeta potential
  8. Source: Colloid and Polymer Science ; Volume 293, Issue 3 , March , 2015 , Pages 941-962 ; 0303402X (ISSN)
  9. URL: http://link.springer.com/article/10.1007%2Fs00396-014-3473-8