Biomimetic Artificial Joints Based on Multi-Material Pneumatic Actuators Developed for Soft Robotic Finger Application

To precisely achieve a series of daily finger bending motions, a soft robotic finger corresponding to the anatomical range of each joint was designed in this study with multi-material pneumatic actuators. The actuator as a biomimetic artificial joint was developed on the basis of two composite materials of different shear modules, and the pneumatic bellows as expansion parts was restricted by frame that made from polydimethylsiloxane (PDMS). A simplified mathematical model was used for the bending mechanism description and provides guidance for the multi-material pneumatic actuator fabrication (e.g., stiffness and thickness) and structural design (e.g., cross length and chamber radius), as well as the control parameter optimization (e.g., the air pressure supply). An actuation pressure of over 70 kPa is required by the developed soft robotic finger to provide a full motion range (MCP = 36°, PIP = 114°, and DIP = 75°) for finger action mimicking. In conclusion, a multi-material pneumatic actuator was designed and developed for soft robotic finger application and theoretically and experimentally demonstrated its feasibility in finger action mimicking. This study explored the mechanical properties of the actuator and could provide evidence-based technical parameters for pneumatic robotic finger design and precise control of its dynamic air pressure dosages in mimicking actions. Thereby, the conclusion was supported by the results theoretically and experimentally, which also aligns with our aim to design and develop a multi-material pneumatic actuator as a biomimetic artificial joint for soft robotic finger application.

Effects of different concentrations of artificial joint prosthesis nanoparticles on cytotoxicity and osteogenic differentiation of bone marrow stromal cell (BMSCs) in vivo

To explore the effects of artificial joint prosthesis nanoparticles on cytotoxicity and osteogenic differentiation of Bone Marrow Stromal Cell (BMSCs). SD rats were used to isolate cells and titanium metal obtained from artificial joint revision surgery was prepared into nanoparticles by the direct current arc plasma method. The SD rats were then divided into control group, blank group (group A: D-MEM medium+10% FBS), low concentration group (group B: 0.01 mg/mL titanium alloy particles), medium concentration group (group C: 0.05 mg/mL titanium alloy particles), high concentration group (group D: 0.1 mg/mL titanium alloy particles plus D-MEM complete medium+10% FBS), followed by analysis of cytotoxicity and osteogenic differentiation of BMSCs. Among the three test groups, group B showed highest percentage of viable cells and group D had lowest. The percentages of viable cells in three test groups were significantly lower and cell death rate were higher than those in the control group (P < 0.05). Titanium alloy metal particles inhibited osteogenic differentiation of BMSCs in a dose dependent manner. The cells in control group were stained and dark brown nuclei were visible. The stained cells were almost invisible in group A, and less red-stained areas in group B, and with a small amount of cell nuclei. Artificial joint prosthesis particles had certain effects on cytotoxicity and osteogenic differentiation of BMSCs in vivo. Among them, the high concentration of titanium alloy nanoparticles test group had the highest percentage of viable cells.