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Research Papers

Designing Controllable Porosity for Multifunctional Deformable Tissue Scaffolds

[+] Author and Article Information
AKM Bashirul Khoda

Department of Industrial Engineering,  University at Buffalo, Buffalo, NY, 14260akm32@buffalo.edu

Bahattin Koc1

Faculty of Engineering and Natural Sciences,  Sabanci University, Istanbul, 34956, Turkeybahattinkoc@sabanciuniv.edu

1

Corresponding author.

J. Med. Devices 6(3), 031003 (Jul 30, 2012) (12 pages) doi:10.1115/1.4007009 History: Received November 28, 2011; Revised April 14, 2012; Published July 30, 2012; Online July 30, 2012

Reconstructing or repairing a damaged tissue with porous scaffolds to restore the mechanical, biological, and chemical functions is one of the major tissue engineering and wound healing strategies. Recent developments in three-dimensional bioprinting techniques and improvements in the biomaterial properties have made fabrication of controlled and interconnected porous scaffold structures possible. Especially, for wound healing or soft tissue engineering, membranes/scaffolds made out of visco-elastic hydrogels, or other soft biomaterials with regular porous structures are commonly used. When the visco-elastic structures are applied onto a wound or damaged area, various forces might act upon these structures. The applied forces caused by bandage or occlusive dressings, contraction, and/or the self-weight could deform the fabricated scaffolds. As a result, the geometry and the designed porosity changes which eventually alters the desired choreographed functionality. To remedy this problem, a denser scaffold providing higher material concentration could be developed. However, denser scaffolds might have a negative impact on cell proliferation and also could block pathways for nutrient and waste transportation. In this work, a novel multifunctional visco-elastic scaffold modeling has been proposed to control the effective porosity of scaffolds. The designed scaffolds are optimized to provide spatial functionality and controlled material concentration under deformed conditions. The proposed methodology has been implemented and illustrative examples are provided in this paper. Effective porosity between the traditional and the proposed scaffold design have been compared by applying both models on the same free-form surface mimicking a wound.

Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Shape conforming deformation of a uniform porous membrane; (b)–(c) schematic diagram showing the load applied on the membrane from dressing

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Figure 2

Roadmap of the proposed methodology

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Figure 3

Equidistant cylindrical filaments with designed porosity

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Figure 4

Change in filament (a) length and (b) corresponding diameter due to the deformation

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Figure 5

(a) Height base contour, (b) strips generation

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Figure 6

Measuring the surface normal along the projected contour and the wound profile

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Figure 7

Pore-cell and deformed porosity calculation

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Figure 8

(a)–(c) Generation of a simple symmetric virtual wound from a sphere with radius of 10 mm; (d) CAD model of two layer hydrogel membrane with 0 deg–90 deg lay-down pattern and 75% porosity applied on the virtual wound

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Figure 9

Membrane with 75% porosity and 100 μm filament diameter (a) conventional fixed filament distance design, (b) proposed method with variational distance; 65% porosity and 150 μm filament diameter (c) conventional fixed filament distance design, (d) proposed method with variational distance

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Figure 10

(a) The undeformed mesh model of both virtual surface and bilayer membrane for FEA; (b) deformed bilayer membrane generated by FEA

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Figure 11

Deformed porosity analysis on two layer membrane designed with (a)–(b) conventional fixed filament distance, (c)–(d) proposed variational filament distance for 75% porosity and 50 μm filament radius; (e)–(f) conventional fixed filament distance, (g)–(h) proposed variational filament distance for 65% porosity and 75 μm filament radius (color legend represent the % deviation from the designed porosity, upper row perspective view and lower row top view)

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Figure 12

Main effect and interaction plot from ANOVA

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Figure 13

(a)–(b) A free form shape and its contour along the depth shows nonsymmetry along every direction

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Figure 14

(a) Undeformed mesh model of both virtual surface and bilayer membrane for FEA, (b) deformed bilayer membrane with stress profile generated by FEA

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Figure 15

Porosity comparison on two layer membrane with 55% porosity and 50 μm filament radius (a) and (c) designed filament; and deformed porosity (b) and (d) perspective view (c) and (f) top view for conventional fixed filament distance and proposed variational filament distance respectively (color legend represent the % deviation from the designed porosity)

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Figure 16

(a)–(b) A multibasin free form shape and its contour along the depth shows nonsymmetry along every direction

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Figure 17

Porosity comparison on two layer membrane with 60% porosity and 60 μm filament radius (a)–(b) top view and perspective view for conventional fixed filament distance; (c)–(d) top view and perspective view for proposed variational filament distance respectively (color legend represent the % deviation from the designed porosity)

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