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Indentation of polydimethylsiloxane submerged in organic solvents

Published online by Cambridge University Press:  11 January 2011

Yuhang Hu
School of Engineering and Applied Sciences, Kavli Institute, Harvard University, Cambridge, Massachusetts 02138
Xin Chen
Department of Chemistry and Chemical Biology, Kavli Institute, Harvard University, Cambridge, Massachusetts 02138
George M. Whitesides
Department of Chemistry and Chemical Biology, Kavli Institute, Harvard University, Cambridge, Massachusetts 02138
Joost J. Vlassak
School of Engineering and Applied Sciences, Kavli Institute, Harvard University, Cambridge, Massachusetts 02138
Zhigang Suo*
School of Engineering and Applied Sciences, Kavli Institute, Harvard University, Cambridge, Massachusetts 02138
a)Address all correspondence to this author. e-mail:
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This work uses a method based on indentation to characterize a polydimethylsiloxane (PDMS) elastomer submerged in an organic solvent (decane, heptane, pentane, or cyclohexane). An indenter is pressed into a disk of a swollen elastomer to a fixed depth, and the force on the indenter is recorded as a function of time. By examining how the relaxation time scales with the radius of contact, one can differentiate the poroelastic behavior from the viscoelastic behavior. By matching the relaxation curve measured experimentally to that derived from the theory of poroelasticity, one can identify elastic constants and permeability. The measured elastic constants are interpreted within the Flory–Huggins theory. The measured permeability indicates that the solvent migrates in PDMS by diffusion, rather than by convection. This work confirms that indentation is a reliable and convenient method to characterize swollen elastomers.

Copyright © Materials Research Society 2011

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