Regional differences in biomechanical properties of the ascending aorta in aneurysmal and normal aortas

Aortic specimens were mechanically characterized using a CellScale BioTester for displacement-controlled biaxial tensile testing and delamination (peel) testing. Prior to testing, tissue thickness was measured with a 12× high-magnification zoom lens. For biaxial tests, 14 mm × 14 mm square samples from the inner and outer curvature were mounted on tungsten rakes, assigned a 50 mN preload (reference configuration), immersed in 37°C Ringer’s lactate, and subjected to 10 preconditioning cycles followed by three equibiaxial test cycles to 25% strain at 0.0088 mm/s. Strain was primarily derived from rake-to-rake displacement (with a subset assessed using optical strain tracking). Stress–strain data were used to calculate energy loss (hysteresis), low-strain tangent modulus, transition-zone stress/strain, and elastic energy in both loading directions. For delamination testing, adjacent 6 mm × 30 mm longitudinal strips were incised in the media and manually started, then mounted on tungsten rakes, immersed in 37°C Ringer’s lactate, and peeled uniaxially at 0.01 mm/s; delamination strength was computed as the mean peel force normalized by sample width.