Computational Modeling of Tissue Engineering Scaffolds as Delivery Devices for Mechanical and Mechanically Modulated Signals - Computational Modeling in Tissue Engineering - page 134

Table 1 Effect of tissue engineering scaffold geometry (porosity and pore size) on fluid flow by
CFD analysis
Reference Scaffold type Flow Average shear surface rate

(l/s) and stress (dyn/cm 2 )

Anderson
et al. [ 2 ]

Idealized design for critical
sized critical defects
Pore diameter: 800 lm
Post diameter: 600 lm

Pressure gradient
(Pa)

Longitudinal channels:
30-40 dyn/cm 2

100 Transverseflow:

0-10 dyn/crn 2

Lesman
et al. [ 30 ]

PLLA/PLGA scaffold
Porosity: 90 %
Average pore diameter:
500 lm

Inflow velocity
(cm/s)

Four different cell layer
thicknesses (0, 50, 75,
125 lm)

2-18 dyn/cm 2 0.5

1
1.5
2

Voronov
et al. [ 44 ]

Poly(L-Iacticacid)
Porosity: 80-95%
Average pore size:
215-402.5 lm

Pressure gradient
(Pa)

*0.1 dyn/crn 2 10

*0.01 dyn/cm 2 1

*0.001 dyn/crn 2

0.1

*0.0001 dyn/cm 2 0.01

Melchels
et al. [ 36 ]

Photo-polymerisable
poly(D/Llactide)
(PDLLA) macromers
Porosity: 62 ± 1%
Isotropic pore size:
412 ± 13 lm

Average fluid Flow
velocity:
0.86 mm/s

15-24/s

Porosity: 35-85 %
Gradient in pore size:
250-500 lm

12-38/s

0.03 dyn/cm 2 Y Yao et al.

[ 45 ]

Idealized design with unit
spherical cells porosity:
70 %

Flow rate:
0.l ml/min

0.15 dyn/cm 2 Flow rate:

0.5 ml/min

0.3 dyn/cm 2

Flow rate: 1 ml/min

deviatoric stresses and seeding density and protocol induced dilatational stresses
[ 2 , 12 , 34 , 35 , 38 , 46 ].
CFD has also been used to optimize geometries of tissue engineered scaffolds
that are manufactured using rapid prototyping or other methods. Furthermore,
material choice will have a large effect on target and actual scaffold geometries
and signal delivery [ 38 ]. Comparing two types of scaffolds, which are made by
Collagen-Glycosaminoglycan (CG) and Calcium Phosphate, CFD predicts that
shear stress is 2.8 times higher in the CG as in the calcium-phosphate scaffold.
This is mainly caused by pore size differences (CG pore size *96 mm, calcium
phosphate pore size *350 mm). A scaffold with bigger pore sizes (215-402.5 lm
average pore size), made of Poly(L-lactic acid), has been also analysed using CFD