Researchers at the University of Texas Austin recently published a paper comparing 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.