Biaxial and Triaxial Testing of Biomaterials

As a result, ZwickRoell has developed a biaxial testing machine that is specifically designed for the mechanical characterization of soft biological and artificial materials. Four linear drives, controlled independently of each other in terms of position, force, or strain, are integrated in the system. Force measurement is via (waterproof) load cells, two each in the X and Y directions. In addition there are four testControl measurement and control electronics units plus a bath for optimum temperature control of the medium. The maximum test load is 100 N per load cell, with resolution up to 0.6 mN. Travel range for tensile measurement is 50 mm (resolution 0.1 μm) and maximum speed is 2,000 mm/min. In addition to clamping fixtures, the specimens can also be connected to the load cells with a rotatable clamping fixture via hook and cord. This fixture creates homogeneous force application in the specimen and thus, a homogeneous force distribution in the specimen. An additional benefit offered by the new testing machine is the laser speckle extensometer, which enables non-contact two-dimensional strain and deformation measurement without specimen marking. The measuring principle is based on evaluation of speckle patterns formed on the specimen surface by illumination with a laser; these are reflected and recorded with a camera. The natural biomaterial specimen is first tested in the lab. The data is then represented in a mathematical model and finally transferred to a computer model. Based on the material characteristics, which can be determined with the biaxial testing machine, the virtual reconstruction of the heart wall can be traced and the predictability of the (pathological) behavior of the heart wall can be examined.