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The mechanical properties of a surface-modified layer on polydimethylsiloxane

Published online by Cambridge University Press:  31 January 2011

K.L. Mills ,
Xiaoyue Zhu ,
Shuichi Takayama  and
M.D. Thouless
K.L. Mills
Affiliation:
Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109
Xiaoyue Zhu
Affiliation:
Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109
Shuichi Takayama
Affiliation:
Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109; and Macromolecular Science and Engineering Program, University of Michigan, Ann Arbor, Michigan 48109
M.D. Thouless*
Affiliation:
Departments of Mechanical Engineering and Materials Science & Engineering, University of Michigan, Ann Arbor, Michigan 48109
*
a)Address all correspondence to this author. e-mail: thouless@umich.edu
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Abstract

Surface modification of the elastomer polydimethylsiloxane (PDMS) by exposure to oxygen plasma for four minutes creates a thin, stiff film. In this study, the thickness and mechanical properties of this surface-modified layer were determined. Using the phase image capabilities of a tapping-mode atomic force microscope (AFM), the surface-modified region was distinguished from the bulk PDMS; specifically, it suggested a graded surface layer to a depth of about 200 nm. Load-displacement data for elastic indentation using a compliant AFM cantilever was analyzed as a plate bending on an elastic foundation to determine the elastic modulus of the surface (37 MPa). An applied uniaxial strain generated a series of parallel nanocracks with spacing on the order of a few microns. Numerical analyses of this cracking phenomenon showed that the depth of these cracks was in the range of 300–600 nm and that the surface layer was extremely brittle, with toughness in the range of 0.1– 0.3 J/m2.

Keywords

Elastic propertiesNanoscaleThin film
Type
Articles
Information
Journal of Materials Research , Volume 23 , Issue 1 , January 2008 , pp. 37 - 48
Copyright
Copyright © Materials Research Society 2008

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