On the Uniaxial Ring Test of Tissue Engineered Constructs

Uniaxial tensile experiments are commonly used to evaluate the mechanical properties of engineered vascular tissues. We consider a typical uniaxial tensile experiment on a ring-shaped specimen and the corresponding theoretical framework within which the experimental data are processed when the sample undergoes a finite deformation. In some cases when the material is considered to be elastic, isotropic and incompressible, data obtained from a ring test can be processed to identify constitutive stress–strain relations via a strain energy function (SEF). Accurate identification of the SEF requires that the experimentally recorded deformations are acquired from a region sufficiently far away from the material-grip interface to minimize the confounding effects of friction and bending. Image-based tracking of surface markers provides a method by which the deformation of the ring sample can be locally recorded when subjected to uniaxial extension. We present an illustrative example of a uniaxial ring experiment on an engineered vascular tissue construct, and process the obtained data to identify the SEF. The SEF is used to perform a finite-element based computational simulation of the ring experiment, which is used to better understand the inherent errors and artifacts which may confound accurate data acquisition and correspondingly SEF identification. The obtained computational results provide guidance on the location of surface markers that facilitate accurate measure of local sample deformation for a range of materials.