Jump to main content
Jump to site search

Issue 4, 2010
Previous Article Next Article

A theory of constrained swelling of a pH-sensitive hydrogel

Author affiliations

Abstract

Many engineering devices and natural phenomena involve gels that swell under the constraint of hard materials. The constraint causes a field of stress in a gel, and often makes the swelling inhomogeneous even when the gel reaches a state of equilibrium. This paper develops a theory of constrained swelling of a pH-sensitive hydrogel, a network of polymers bearing acidic groups, in equilibrium with an aqueous solution and mechanical forces. The condition of equilibrium is expressed as a variational statement of the inhomogeneous field. A free-energy function accounts for the stretching of the network, mixing of the network with the solution, and dissociation of the acidic groups. Within a Legendre transformation, the condition of equilibrium for the pH-sensitive hydrogel is equivalent to that for a hyperelastic solid. The theory is first used to compare several cases of homogenous swelling: a free gel, a gel attached to a rigid substrate, and a gel confined in three directions. To analyze inhomogeneous swelling, we implement a finite element method in the commercial software ABAQUS, and illustrate the method with a layer of the gel coated on a spherical rigid particle, and a pH-sensitive valve in microfluidics.

Graphical abstract: A theory of constrained swelling of a pH-sensitive hydrogel

Back to tab navigation

Supplementary files

Publication details

The article was received on 20 Aug 2009, accepted on 23 Nov 2009 and first published on 26 Jan 2010


Article type: Paper
DOI: 10.1039/B917211D
Citation: Soft Matter, 2010,6, 784-793
  •   Request permissions

    A theory of constrained swelling of a pH-sensitive hydrogel

    R. Marcombe, S. Cai, W. Hong, X. Zhao, Y. Lapusta and Z. Suo, Soft Matter, 2010, 6, 784
    DOI: 10.1039/B917211D

Search articles by author

Spotlight

Advertisements