Summary: Indentation: A simple, nondestructive method for characterizing the
mechanical and transport properties of pH-sensitive hydrogels
Yuhang Hu, Jin-Oh You, Debra T. Auguste, Zhigang Suo, and Joost J. Vlassaka)
School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
(Received 13 May 2011; accepted 30 August 2011)
We use instrumented indentation to characterize the mechanical and transport behavior of
a pH-sensitive hydrogel in various aqueous buffer solutions. In the measurement, an indenter is
pressed to a fixed depth into a hydrogel disk and the load on the indenter is recorded as a function
of time. By analyzing the load­relaxation curve using the theory of poroelasticity, the elastic
constants of the hydrogel and the diffusivity of water in the gel can be evaluated. We investigate
how the pH and ionic strength of the buffer solution, the hydrogel cross-link density, and the
density of functional groups on the polymer backbone affect the properties of the hydrogel. This
work demonstrates the utility of indentation techniques in the characterization of pH-sensitive
hydrogels.
I. INTRODUCTION
Hydrogels are cross-linked polymer networks swollen
in an aqueous solution. A number of hydrogels are stimuli-
responsive; they swell in response to external stimuli, such
as temperature,1
electrical field,2

Source: Auguste, Debra T. - School of Engineering and Applied Sciences, Harvard University

Collections: Materials Science; Biology and Medicine