Rheological properties of cell-hydrogel composites extruding through small-diameter tips

To form 3D structures with composites of living cells and hydrogel is now becoming an attractive technology in both bioengineering and manufacturing areas. Variant processes have been presented, most of which are based on the cell composite extrusion and deposition technique. So, the design of cell extrusion nozzle turns into an important phase, and the rheological properties of cell-hydrogel composites act as a key parameter and must be well investigated. In this paper an entrance pressure detection device and adaptor for small-diameter tips were developed. With the hypothesis of power law fluid type, the power law constant and coefficient were calculated. As derived from the experimental results, the cell-hydrogel composites (with the maximum cell concentration of 10(7)/Ml) show no difference from hydrogel materials in rheological properties. Based on these, the manufacturability of cell-hydrogel composites was discussed. Also, the cell viability, which is another important issue in cell assembly technology, was discussed. The peak percentage (97%) was achieved at the flow rate of 0.5 mm(3)/s. The extruding duration and the maximum shear stress loaded on cells were considered as two influence mechanisms.