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Technical Briefs

Evaluation of the Effective Diffusivity of a Freeform Fabricated Scaffold Using Computational Simulation

[+] Author and Article Information
Jin Woo Jung, Woon-Jae Yong

Department of Mechanical Engineering,
POSTECH, San 31,
Hyoja-dong, Nam-gu, Pohang,
Gyeongbuk 790-784, Korea

Hee-Gyeong Yi, Won-Soo Yun

Department of Mechanical Engineering,
Korea Polytechnic University,
2121 Jeongwang-dong, Siheung-si,
Gyeonggi-do 429-793, Korea

Dong-Woo Cho

Department of Mechanical Engineering,
POSTECH, San 31,
Hyoja-dong, Nam-gu, Pohang,
Gyeongbuk 790-784, Korea;
Division of Integrative Biosciences and Biotechnology,
POSTECH, San 31,
Hyoja-dong, Nam-gu, Pohang,
Gyeongbuk 790-784, Korea
e-mail: dwcho@postech.ac.kr

1Jin Woo Jung and Hee-Gyeong Yi contributed equally to this research project.

2Corresponding authors.

Contributed by the Bioengineering Division of ASME for publication in the JOURNAL OF BIOMECHANICAL ENGINEERING. Manuscript received May 27, 2012; final manuscript received April 22, 2013; accepted manuscript posted May 15, 2013; published online June 12, 2013. Assoc. Editor: Stephen Klisch.

J Biomech Eng 135(8), 084501 (Jun 12, 2013) (7 pages) Paper No: BIO-12-1208; doi: 10.1115/1.4024570 History: Received May 27, 2012; Revised April 22, 2013; Accepted May 15, 2013

In scaffold-based tissue engineering, sufficient oxygen and nutrient supply into cells within a scaffold is essential to increase cell viability and the proliferation rate. Generally, oxygen and nutrients reach the cells through the media by diffusion in vitro or in vivo, assuming there is no convection flow through a scaffold with small-sized pores. The scaffold diffusion rate depends mainly on the scaffold pore architecture. Thus, understanding the effect of scaffold pore architecture on the diffusion mechanism is necessary to design an efficient scaffold model. This study proposes a computational method to estimate diffusivity using the finite element analysis (FEA). This method can be applied to evaluate and analyze the effective diffusivity of a freeform fabricated 3D scaffold. The diffusion application module of commercial FEA software was used to calculate the spatial oxygen concentration gradient in a scaffold model medium. The effective diffusivities of each scaffold could be calculated from the oxygen concentration data, which revealed that the scaffold pore architecture influences its effective diffusivity. The proposed method has been verified experimentally and can be applied to design pore architectures with efficient diffusion by increasing our understanding of how the diffusion rate within a scaffold is affected by its pore architecture.

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Figures

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Fig. 1

Scaffold design for FEA. (a) Lattice scaffold (type 1), L = 2 mm, Ct = Cw = 200 μm. (b) lattice scaffold (type 2), L = 2 mm, Ct = 100 μm, Cw = 200 μm. (c) staggered scaffold (type 3), L = 2 mm, Ct = 100 μm, Cw = 200 μm.

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Fig. 2

Schematic diagram of constraints and boundary conditions for FEA

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Fig. 3

The oxygen diffusion across the scaffold from z = 0 to z = L

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Fig. 4

Photograph of the fabricated scaffold (a). Scanning electron micrographs of (b) scaffold type 1, (c) type 2, and (d) type 3.

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Fig. 5

Schematics of the experimental diffusivity measurement system

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Fig. 6

Oxygen concentrations in the scaffolds at time ts

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Fig. 7

The average oxygen concentration at time ts and the fitted curve used to estimate numerically the effective diffusivities of the (a) scaffold type 1, (b) scaffold type 2, (c) scaffold type 3, and (d) the averaged oxygen concentration and its standard deviation of each cross-section at five positions along the z-axis of scaffold type 1

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Fig. 8

Estimated effective diffusivities of scaffold type 1 (2.868 × 10–9 m2/s), type 2 (2.238 × 10–9 m2/s), and type 3 (1.758 × 10–9 m2/s). *p < 0.01.

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Fig. 9

The diffusion flux in (a) scaffold type 1, (b) scaffold type 2, and (c) scaffold type 3 at time ts

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