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Elastic Modulus Measurement of Hydrogels

  • Donghee Lee
  • Haipeng Zhang
  • Sangjin Ryu
Living reference work entry
Part of the Polymers and Polymeric Composites: A Reference Series book series (POPOC)

Abstract

Hydrogels have been employed for a wide variety of applications, and their mechanical properties need to be modulated based on the applications. In particular, the Young’s modulus, or elastic modulus, of hydrogels is a critical property for understanding their mechanical behaviors. In principle, the Young’s modulus of a hydrogel can be measured by finding a relationship between a force applied to the hydrogel and the resultant deformation of the hydrogel. On a macroscale, Young’s modulus is usually obtained by measuring the stress-strain curves of a hydrogel specimen through the compression method or the tensile method and then finding the slope of the curve. Also, the shear modulus of a hydrogel is measured using a rheometer with parallel plates and then converted into Young’s modulus considering Poisson’s ratio. On a mesoscale, the elastic modulus can be measured by the imaging-based indentation methods which measure the indentation depth of a hydrogel sample deformed by a static ball indenter on the gel. The measured indentation depth is converted to the Young’s modulus of the hydrogel via a contact mechanics model. The mesoscale indentation method and pipette aspiration method are also available. On a microscale, the elastic modulus is usually measured using the atomic force microscopy (AFM)-based indentation method. A hydrogel specimen is locally indented by a sharp or colloidal tip of an AFM probe, and the Young’s modulus of the hydrogel is obtained by fitting an appropriate indentation model against the recorded force-distance curves. An appropriate elastic modulus measurement method needs to be chosen depending on the application, length scale and expected elastic property of the hydrogels.

Keywords

Young’s modulus Shear modulus Atomic force microscopy Indentation Rheometer Compression test 

Notes

Acknowledgments

We acknowledge supports from the Nebraska Tobacco Settlement Biomedical Research Development Fund through (1) Bioengineering for Human Health Grant of the University of Nebraska-Lincoln (UNL) and the University of Nebraska Medical Center (UNMC) and (2) Biomedical Research Seed Grant of UNL. AFM measurements were performed at the NanoEngineering Research Core Facility of UNL, which is partially funded from Nebraska Research Initiative Funds.

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© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Mechanical and Materials EngineeringLincolnUSA
  2. 2.Nebraska Center for Materials and Nanoscience, University of Nebraska-LincolnLincolnUSA

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