Diffusion through colloidal shells under stress

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Entry by Emily Redston, AP 225, Fall 2011

Work in Progress

Entry by Emily Redston, AP 225, Fall 2011


Diffusion through colloidal shells under stress by J. Guery, J. Baudry, D. A. Weitz, P. M. Chaikin, and J. Bibette. Phys. Rev. E 79, 060402(R) (2009).


One area of great interest in soft matter is encapsulation. With applications in almost all types of industrial domains, from the oil industry to food packaging, efficient storage of gases and liquid in solid containers is of tremendous technological and economical importance. Furthermore, encapsulation of active ingredients such as drugs, proteins, nutrients, or vitamins is essential for a myriad of applications, such as drug delivery and agrichemicals.

The goal of encapsulation is to protect the delicate substances inside from a harsh environment, and to retain their activity until some required time. Long-term storage of liquids or gases often involve internal pressures, which increase the tensile stress of the container wall. At a colloidal scale, it is the osmotic pressure difference between the internal and external medium that is relevant, rather than the hydrostatic pressure. Eyring proposed that the permeability of solids is associated with a diffusive process involving an activation mechanism. Unfortunately, many of his ideas have not been tested quantitatively and thus many fundamental concepts are not fully understood.

In this paper, the authors propose a very cute little experiment for testing some of Eyring's ideas. By using core-shell (liquid core - solid shell) colloidal particles that are sensitive to osmotic pressure, they are able to follow the permeation of encapsulated probes at various stresses.

Experimental Set-Up