Identification of the testing parameters in high frequency dynamic shear measurement on agarose gels.

Dynamic mechanical analysis (DMA) on agarose gels can be used to validate magnetic resonance elastography (MRE) measurements as well as to provide better understanding for the biological responses of cells to the dynamic loadings in cell culture studies. Various parameters potentially affecting the repeatability and accuracy of the DMA shear modulus measurements were investigated systematically in the present study, including sample thickness, shear strain, testing frequency, and compressive clamping strain. The study showed that the thickness of the agarose gel sample must be sufficiently small (1 mm) to prevent the erroneous fluctuation in the measured modulus. The appropriate levels of shear strain (< or = 0.5%) and compressive clamping strain (5-10%) must be applied to overcome the slippage at the gel-clamp interface without causing significant boundary and stress non-uniformity or micro-cracks in the agarose gel sample.