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Han X, et al.

to the restrictions imposed by the traditional method used shown in Figure 1.
to manufacture the artificial vascular vessels. Firstly, In Figure 1(A), branch levels and branching point
the branches were created using straight tubes, and the are illustrated while Figure 1(B) demonstrates parent
vascular branching design was missing. The second diameter R p , daughter diameters R and R , total
d1
d2
issue is that nutrient diffusion through the vessel wall to branching angle α, blood velocity , viscosity , density
the surrounding cells was not considered in their design. and WSS and the recirculation areas. In the following
Unlike previous attempts, the application of 3D printing sub-sections, developing the design methodology at both
enables arbitrary vascular system design. In this work, scales is the main objective.
we addressed these issues by developing comprehensive 2.1 The macro-scale design (vascular system
design rules for 3D printing artificial vascular networks
to be embedded in tissue-engineered skin models. configuration design)
The main parameters considered in our design First of all, in this design, we focused on bifurcations
can be described in two categories: 1) the macro- because, in normal vasculature, around 98% of blood
scale parameters and 2) the micro-scale parameters. vessels bifurcate at each junction, while only 2%
The macro-scale parameters include branch levels and trifurcate [22,37] . We also limit our design to a 2D plane.
branching point locations. The micro-scale parameters 3D structures can be formed by stacking some 2D
include branch angles, vessel diameters, the daughter vascular systems. The locations of the branching points
vessel asymmetry ratio, the wall shear stress and the are evenly distributed on the skin patch, which can be
recirculation areas. Their definition and illustration are illustrated in Figure 2.

(A) The macro-scale parameters in the design of an artificial vascular network

(B)The micro-scale parameters in the design of one single branching area
Figure 1. The macro-scale (A) and the micro-scale (B) parameter definitions.

International Journal of Bioprinting (2018)–Volume 4, Issue 2 3