Identification of the viscoelastic properties of a hydrogel in sol–gel transition by vibration experiments

Characterization of drying-induced changes in moduli and internal stresses in a constrained gel using laser vibrometry

“…Damping ratios reported for poloxomer hydrogels are also close to our measurements; 1–2% in the fully-cured state. 33 In any case, those damping ratios deliver a minimum of 10-fold dynamic magnification around resonances and thus promise clear identification of modal frequencies even under small excitation. For the first mode, the damping ratio reaches a peak when the water loss is around 30 wt% and decreases with further drying.…”

“…The range of moduli estimated from the measured modal frequencies is consistent with the reported values for gelatin and various hydrogels. 10,11,18,19,33,51 Besides, de Gennes proposed that elastic modulus for swollen gels should scale with a power of 2.25 of concentration. 50 Moduli obtained from uniaxial compression of gelatin suggest concentration-dependent increase but with lesser scaling powers than de Gennes’ argument; e.g.…”

“…Recent applications of vibration-based techniques on hydrogels are promising for accurate, non-destructive and quick mechanical characterization. 8,10,11,32,33 In particular, Schwarz et al measured the axisymmetric vibration modes of circular gelatine plates. The work identifies the elastic moduli from modal frequencies and compares them with the values obtained via atomic force microscopy and uniaxial compression.…”

“…Another recent study by Guisquet and Amabili successfully extracts viscoelastic properties of hydrogel samples from vibrations during highly transient sol–gel transition. 33…”

“…Dynamic mechanical analysis and rheometry deliver the storage and loss moduli of materials over a range of loading frequencies. Gels with low stiffness (high water content) and high adhesion can result in sample sticking during DMA techniques as described inref. 33.…”