AFM nanoscale indentation in air of polymeric and hybrid materials with highly different stiffness

Year: 2014

Authors: Suriano R., Credi C., Levi M., Turri S.

Autors Affiliation: Politecn Milan, Dept Chem Mat & Chem Engn Giulio Natta, I-20133 Milan, Italy.

Abstract: In this study, nanomechanical properties of a variety of polymeric materials was investigated by means of AFM. In particular, selecting different AFM probes, poly(methyl methacrylate) (PMMA), polydimethylsiloxane (PDMS) bulk samples, sol-gel hybrid thin films and hydrated hyaluronic acid hydrogels were indented in air to determine the elastic modulus. The force-distance curves and the indentation data were found to be greatly affected by the cantilever stiffness and by tip geometry. AFM indentation tests show that the choice of the cantilever spring constant and of tip shape is crucially influenced by elastic properties of samples. When adhesion-dominated interactions occur between the tip and the surface of samples, force-displacement curves reveal that a suitable functionalization of AFM probes allows the control of such interactions and the extraction of Young’ modulus from AFM curves that would be otherwise unfeasible. By applying different mathematical models depending on AFM probes and materials under investigation, the values of Young’s modulus were obtained and compared to those measured by rheological and dynamic mechanical analysis or to literature data. Our results show that a wide range of elastic moduli (10 kPa-10 GPa) can be determined by AFM in good agreement with those measured by conventional macroscopic measurements.

Journal/Review: APPLIED SURFACE SCIENCE

Volume: 311      Pages from: 558  to: 566

More Information: The research was funded by Cariplo Foundation, Milano, Italy, grant number 2010/0365, project 3D Micro structuring and Functionalization of Polymeric Materials for Scaffolds in Regenerative Medicine. Special thank to Gigliola Clerici for rheological measurements and technical support and to Dario Picenoni for SEM analyses.
KeyWords: AFM; Nanoindentation; Polymer; Sol-gel hybrid; Hydrogel; Indentation models
DOI: 10.1016/j.apsusc.2014.05.108

Citations: 32
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