[en] In our previous study, an instrument for characterizing mechanical properties under multi-mechanical load and multi-physical field coupling conditions was designed and constructed. Given the structural interference, the linear and shear strains in tension–torsion coupling testing were measured indirectly using linear and circular grating encoders rather than the extensometers in a conventional material testing machine. Accordingly, to correct the experimental curves measured using grating encoders, a correction method was proposed using equations based on the analysis of specimen geometry and instrument structure by elasticity theory. The feasibility of the correction method under single load and tension–torsion coupling loads were verified by the contrast tests among curves of grating encoders’, curves of extensometers, and results of a digital image correlation (DIC) measuring system. Test results illustrate that the correction method can convert the displacement measured using grating encoders to the deformation of the specimen in the elastic range, and the measuring error of elastic moduli can be reduced to approximately 1/5–1/50 of the original measurement results. The defect on accuracy of this instrument, which is incompatible with extensometers, can be compensated. Overall, the main sources of error in these devices are the deformation of the load cell and that on the non-gage section of specimen. This conclusion can provide guidance on the design of other similar devices. (paper)

[en] Calcium alginate hydrogels are widely used as biocompatible materials in a substantial number of biomedical applications. This paper reports on a hybrid 3D printing and electrodeposition approach for forming 3D calcium alginate hydrogels in a controllable manner. Firstly, a specific 3D hydrogel printing system is developed by integrating a customized ejection syringe with a conventional 3D printer. Then, a mixed solution of sodium alginate and CaCO₃ nanoparticles is filled into the syringe and can be continuously ejected out of the syringe nozzle onto a conductive substrate. When applying a DC voltage (∼5 V) between the substrate (anode) and the nozzle (cathode), the Ca²⁺ released from the CaCO₃ particles can crosslink the alginate to form calcium alginate hydrogel on the substrate. To elucidate the gel formation mechanism and better control the gel growth, we can further establish and verify a gel growth model by considering several key parameters, i.e., applied voltage and deposition time. The experimental results indicate that the alginate hydrogel of various 3D structures can be formed by controlling the movement of the 3D printer. A cell viability test is conducted and shows that the encapsulated cells in the gel can maintain a high survival rate (∼99% right after gel formation). This research establishes a reliable method for the controllable formation of 3D calcium alginate hydrogel, exhibiting great potential for use in basic biology and applied biomedical engineering. (paper)