Understanding the biomechanics of tendon entheses is fundamental for surgical repair and tissue engineering, but also relevant in biomimetics and palaeontology. 3D imaging is becoming increasingly important in the examination of soft tissue deformation. But entheses are particularly difficult objects for micro-computed tomography because they exhibit extreme differences in X-ray attenuation. In this article, the ex vivo examination of Achilles tendon entheses from mice using a combination of tensile tests and synchrotron radiation-based micro-computed tomography is reported. Two groups of specimens with different water content are compared with regard to strains and volume changes in the more proximal free tendon and the distal tendon that wraps around the Tuber calcanei. Tomograms of relaxed and deformed entheses are recorded with propagation-based phase contrast. The tissue structure is rendered in sufficient detail to enable manual tracking of patterns along the tendon, as well as 3D optical flow analysis in a suitable pair of tomograms. High water content is found to increase strain and to change the strain distribution among proximal and distal tendon. In both groups, the volume changes are higher in the distal than in the proximal tendon. These results support the existence of a compliant zone near the insertion. They also show that the humidity of the specimen environment has to be controlled. Necessary steps to extend the automatic tracking of tissue displacements to all force steps are discussed.

Climbing is a current challenge in robotics. Observation of vertebrate climbing proves, that in arboreal environment like on flat ground locomotion is carried out as well by the trunk as by the limbs. Thus to elucidate one extreme a trunk-driven concept was chosen as base for our design process. Often climbing robots are highly specialized machines. They only are able to move on one or two different substrates. And they often are expensive solutions, built for a special application. The climbing robot we report about is designed as a modular system. The modular idea influences all developmental areas of a mechatronic system -the mechanical, the electronic as well as the software part. By using different modules, the robot is capable to climb on different substrates made of a wide variety of materials. The mechanical demands of climbing are strong and rule the design. Substrate contact has to be established and broken actively. A sensor concept was developed, which allows for choosing relevant sensor ranges, depending on the desired type of control. The configuration described in this paper is composed of only two different module types. Due to the features of these modules, the robot is capable to climb on pipe-like structures. The speed of the robot depends on the gait chosen.