Researchers at the University of Texas Austin recently published a paper comparing stiffness measurements the shear moduli from 18 PVA hydrogel formulations based on 5 mechanical test methods: tension, compression, shear rheology, macroindentation, and nanoindentation. In general, the paper shows that the methods yielded similar results and that there were pros and cons for each. Some of the conclusions are:

  • Physically larger samples resulted in more reliable data.
  • Variation of length by more that 2 orders of magnitude did not significantly affect the resulting modulus (macro vs nano-indentation).
  • The use of non-contact strain sensing improved the test results.
  • The Hertz contact mechanics model for spherical indentation testing was appropriate for these type of materials.

A further goal of the research was to use these results to work towards a structure-based method for estimating a hydrogel stiffness.

Read more here.