ABSTRACT
In this paper, the limb of a goat is chosen as the research object, and according to mammalian anatomy, a bionic model called the quasi inverted pendulum with "J" curve spring (QIPJCS) model with nonlinear stiffness is built, and the equations of motion are derived. Based on these equations, the advantages of the QIPJCS model are illustrated from the aspect of the stable motion region by the SFA (step-to-fall analysis) numerical simulation method. These results are compared with the traditional SLIP model. Furthermore, the ARM (Apex-Return-Map) of this model is built, and the fixed points are analyzed. Finally, according to the locomotion law of goats running with gallop gaits and the analysis of the dead-point support effect, the dynamic motion mechanism of goat limbs is elucidated, and the equivalent mechanism model is built. Based on the mechanism, the dynamic mechanical analysis indicates that the joint driving torque can be minimized to conserve energy by optimizing the landing angle. The running mechanism research of quadruped mammals, which is based on the novel bionic stiffness model, provides theoretical support for the design of high-performance mechanical legs and the motion control of bionic robots.
ABSTRACT
Silk fibroin coatings on biomedical magnesium alloys have garnered significant attention due to their enhanced corrosion resistance and biocompatibility. However, the utilization of wild A. pernyi silk fibroin, known for its RGD sequence that facilitates tissue regeneration, presents a challenge for corrosion-resistant coatings on magnesium alloys due to its weak adhesion and high dissolution rate. In this study, we employed hexafluoroisopropanol as a solvent to blend A. pernyi silk fibroin with B. mori silk fibroin. The resulting blended fibroin coating at a 3:7 mass ratio exhibited a heterogeneous nucleation effect, enhancing ß-sheet content (32.3 %) and crystallinity (28.6 %). This improved ß-sheet promoted the "labyrinth effect" with an Icorr of 2.15 × 10-6 A cm-2, resulting in significantly improved corrosion resistance, which is two orders of magnitude lower than that of pure magnesium alloy. Meanwhile, the increased content of exposed serine in zigzag ß-sheet contributes to a higher adhesion strength. Cell cytotoxicity evaluation confirmed the enhanced cell adhesion and bioactivity. This work provides a facile approach for wild A. pernyi silk fibroin coatings on magnesium alloys with enhanced corrosion resistance, adhesion and biocompatibility.
