Page 130 - IJB-10-6

International Journal of Bioprinting Fluid mechanics of extrusion bioprinting

Table 2. Values of various cell damage models’ parameters
Model contributors Bioink Cell damage model parameters Value
a 3.9 × 10 -4
1
b 0.48
1
Alginate/RSC96 c 0.71
1
a -9.43 × 10 -4
2
Alginate/RSC96; Alginate/ b 2 0.61
Ning et al. 63
L8 a 1 -3.2 × 10 -4
b 0.61
1
Alginate/L8 c 0.52
1
a -1.43 × 10 -3
2
b 2 0.55
D 0 0.0693
Alginate 2%/ CCD-986sk D 0.4262
∞
ε 0.0419
d
D 0 0.0828
Alginate/human- dermal
Han et al. 73 Alginate 3%/ CCD-986sk D 0.3614
fibroblasts CCD-986sk ∞
ε d 0.0283
D 0.0861
0
Alginate 4%/ CCD-986sk D 0.3063
∞
ε 0.0257
d
A 0.50
0
A eq,∞ 0.70
k 1 0
k 2 4
DCR data from Han et al.
73
Chirianni et al. 74 - a 0.0281
and Li et al. 75 p
a 0.4977
e
e 0.1428
D e,max 0.2795
D 0.4358
max
Abbreviation: DCR, damaged cell ratio
damage model based on the cell damage results of Han 3. Bioink rheology and its effect on
et al. and Li et al. (Figure 4B and C). bioprinting outcomes
73
75
Considering the role of the nozzle in subjecting the During the extrusion process, bioink flows through
cells to shear and extensional stresses, its design is among the syringe and the dispensing nozzle before being
the most significant factors directly impacting cell viability. deposited on the printing stage. The rheology of bioink
Enhancing nozzle design and minimizing the forces is the main factor that governs the behavior of bioink
exerted on the bioink, in conjunction with controlling the during the extrusion, thus affecting printability and
concentration of the bioink, can greatly reduce stresses and cell viability to a great extent. In rheology, the flow
cell injuries. It should be noted that when bioprinting behavior of a fluid represents the relationship between
76
with cells, it is crucial to reduce or minimize the process- the fluid flow (or strain rate) and the stress within the
induced forces or stresses on the cells. 73,74 To achieve this, fluid and can generally divided into Newtonian and
a straightforward method is to employ lower extrusion non-Newtonian fluids. Figure 5 illustrates the stresses
pressures, as elevated pressure increases shear stress within applied on an imaginary 3D element of fluid in flow,
=
=
the nozzle flow, thus possibly damaging the cell membrane representing the stress (τ ) and strain rate (γ )
and reducing cell viability. tensors for that element. Rheological models are

Volume 10 Issue 6 (2024) 122 doi: 10.36922/ijb.3973