Multiaxis printing method for bent tubular structured gels in support bath for achieving high dimension and shape accuracy

Abstract

Gels are soft materials that have high potential for use as alternative artificial blood vessels. 3D gel printing has attracted attention because it can be used to create gels with arbitrary and complicated shapes. The conventional 3D gel printing process (triaxial printing) is as follows: ⅰ) a sol material is patterned to form a layer on the XY plane, ⅱ) a crosslinker is added to it, ⅲ) the Z stage is lowered by the stacking pitch, and ⅳ) a new sol material is patterned on the previous layer. However, irregular protrusions and stepped structures appear at the overhang parts as the height and scale increase. In addition, there are non-adhesion sections between adjacent layers. To solve these problems, we propose a “multiaxis printing method,” in which layers are seamlessly stacked by changing the extruding direction by following the neutral line of a structure. We evaluate the dimension and shape accuracy of the proposed method by printing bent hollow tubular structured gels. The proposed method significantly suppresses irregular protrusions on outer walls. Moreover, each layer is seamlessly joined. The structures printed using the proposed method show good dimension and shape accuracy. The minimum lumen area ratio is 75%, which is comparable to native common carotid arteries. In addition, the maximum errors in the bending angle and curvature radius are 1.7% and 5.1%, respectively. However, the average outer and inner diameters are smaller than the patterning diameter, suggesting that the crosslinked gels attract each other in the circumferential direction. This indicates that a model should be designed considering gel shrinkage to further improve the accuracy of printing.