Equilibrium swelling and kinetics of pH （pH值平衡肿胀和动力学）.pdfVIP

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 Thermodynamic models have been used extensively to ex- in a number of applications like control of microfluidic flow, plain the equilibrium swelling of hydrogels. These models are development of muscle-like actuators, filtration/separation and simple to use, but they do not provide good quantitative results drug delivery makes it important to properly understand these [9], [10]. Many of the input parameters in the thermodynamic materials. Understanding hydrogel properties is also important from the standpoint of their similarity to many biological tissues. model are difficult to determine and are often adjusted to “fit” Typically, gel size is sensitive to outer solution pH and salt the model to the gel’s equilibrium behavior. Theoretical models concentration. In this paper, we develop models to predict the have been developed to predict the swelling and deswelling ki- swelling/deswelling of hydrogels in buffered pH solutions. An netics of hydrogels [11], [12]. However, the models and experi- equilibrium model has been developed to predict the degree of ments were done under nonbuffered solution conditions, where swelling of the hydrogel at a given pH and salt concentration in the the swelling rate is very slow. Prior studies have also dealt wi