4.5.1. Structural model and process parameters
In an ideal state, shear stress and velocity distribution through the nozzle are shown in Figure (7a). The shear stress is proportional to the radius, and the cut is linear[40]. The flow velocity is parabolic, the centre is the largest, and the wall is zero. In this way, the applied nozzle shear stress gradient distribution affects the printing-related cell damage[41]. Moreover, it can have a different impact on the polymer chain of the gel, thereby affecting the internal structure of the printed fibre.
Considering the shear stress gradient through the nozzle, we established a model diagram of the pore distribution of the printed gel fibre section. The outermost layer of the gel filament had the smallest pore size, followed by the inner layer, with the central layer having the largest pore size. The ideal model diagram of the pore distribution of the printed filament for vessel scaffold is depicted in Figure 7(b).