Dynamic Mechanical Analysis of Agarose Hydrogels and Its Relationship to Shear Oscillation

Hydrogels are materials, which offers a number of usage due to its unique properties such a biocompatibility or high water content. They might be utilized in wound dressing, tissue engineering or extracellular matrix modelling. For each application, materials with different characteristics are desired. Therefore, rheology characterization is essential in case of hydrogel studies. Besides more common shear rheology, dynamic mechanical analysis can provide a useful information about the material viscoelastic behaviour. In this case, an ability to resist to deformation is in form of tension/compression contrary to shear deformation in shear rheology. In this study, strain sweep testing both in shear as well as in DMA mode is studied on the agarose hydrogel. Besides comparison between these two approaches including Poisson's ratio, some other variables, which can influence results, are discussed. Particularly, axial force during measurement and/or different measuring geometries were studied. Regarding to results, even small changes in axial force can have a significant impact on the viscoelastic modulus values. Therefore, control axial force measurement are preferred over the gap control measurement. Moreover, using the same geometry systems during measurement is essential in order to obtain valid and comparable results.