Macrocompression and nanoindentation of soft viscoelastic biological materials.

The study of the mechanical behavior of soft biological materials presents many challenges due to the materials' time-dependent mechanical response as well as inherent size and shape limitations. In this study, by using agar as a surrogate material for soft tissues, the effects of these limitations upon standardized macroscale dynamic compression protocols are compared to dynamic nanoindentation procedures. Both techniques are then applied to dynamically test porcine sclera tissue, showing a significant difference in recorded loss and storage modulus values between the two methodologies. Additionally, the tissues of the porcine eye wall are characterized with macrocompression in their layered in vivo arrangement. The overall constraints of standardized macroscale tests for dynamic mechanical characterization of thin and soft biological tissues are discussed.