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Summary: 544 JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, VOL. 11, NO. 5, OCTOBER 2002
Equilibrium Swelling and Kinetics of pH-Responsive
Hydrogels: Models, Experiments, and Simulations
Sudipto K. De, N. R. Aluru, Member, IEEE, B. Johnson, W. C. Crone, David J. Beebe, Member, IEEE, and J. Moore
Abstract--The widespread application of ionic hydrogels
in a number of applications like control of microfluidic flow,
development of muscle-like actuators, filtration/separation and
drug delivery makes it important to properly understand these
materials. Understanding hydrogel properties is also important
from the standpoint of their similarity to many biological tissues.
Typically, gel size is sensitive to outer solution pH and salt
concentration. In this paper, we develop models to predict the
swelling/deswelling of hydrogels in buffered pH solutions. An
equilibrium model has been developed to predict the degree of
swelling of the hydrogel at a given pH and salt concentration in the
solution. A kinetic model has been developed to predict the rate of
swelling of the hydrogel when the solution pH is changed. Experi-
ments are performed to characterize the mechanical properties of
the hydrogel in different pH solutions. The degree of swelling as
well as the rate of swelling of the hydrogel are also studied through
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