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The mechanical properties of a surface-modified layer on polydimethylsiloxane

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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.

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Acknowledgments

We thank Dr. J.R. Barber and Donghee Lee for valuable discussion, and the National Institutes of Health (Grant EB003793-01) for funding. K.L. Mills acknowledges a Graduate Research Fellowship from the National Science Foundation.

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Authors and Affiliations

  1. Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, 48109, USA

    K.L. Mills

  2. Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, 48109, USA

    Xiaoyue Zhu & Shuichi Takayama

  3. Macromolecular Science and Engineering Program, University of Michigan, Ann Arbor, Michigan, 48109, USA

    Shuichi Takayama

  4. Departments of Mechanical Engineering and Materials Science & Engineering, University of Michigan, Ann Arbor, Michigan, 48109, USA

    M.D. Thouless

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  1. K.L. Mills
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  2. Xiaoyue Zhu
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  4. M.D. Thouless
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Correspondence to M.D. Thouless.

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Mills, K., Zhu, X., Takayama, S. et al. The mechanical properties of a surface-modified layer on polydimethylsiloxane. Journal of Materials Research 23, 37–48 (2008). https://doi.org/10.1557/JMR.2008.0029

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