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Research Papers

Modeling the Flow Behavior and Flow Rate of Medium Viscosity Alginate for Scaffold Fabrication With a Three-Dimensional Bioplotter

[+] Author and Article Information
Md. Sarker

Division of Biomedical Engineering,
University of Saskatchewan,
57 Campus Drive,
Saskatoon, SK S7N 5A9, Canada
e-mail: mas921@mail.usask.ca

X. B. Chen

Department of Mechanical Engineering,
University of Saskatchewan,
57 Campus Drive,
Saskatoon, SK S7N 5A9, Canada;
Division of Biomedical Engineering,
University of Saskatchewan,
57 Campus Drive,
Saskatoon, SK S7N 5A9, Canada
e-mail: xbc719@mail.usask.ca

Manuscript received October 7, 2016; final manuscript received March 3, 2017; published online April 20, 2017. Assoc. Editor: Zhijian J. Pei.

J. Manuf. Sci. Eng 139(8), 081002 (Apr 20, 2017) (14 pages) Paper No: MANU-16-1535; doi: 10.1115/1.4036226 History: Received October 07, 2016; Revised March 03, 2017

Tissue regeneration with scaffolds has proven promising for the repair of damaged tissues or organs. Dispensing-based printing techniques for scaffold fabrication have drawn considerable attention due to their ability to create complex structures layer-by-layer. When employing such printing techniques, the flow rate of the biomaterial dispensed from the needle tip is critical for creating the intended scaffold structure. The flow rate can be affected by a number of variables including the material flow behavior, temperature, needle geometry, and dispensing pressure. As such, model equations can play a vital role in the prediction and control of the flow rate of the material dispensed, thus facilitating optimal scaffold fabrication. This paper presents the development of a model to represent the flow rate of medium viscosity alginate dispensed for the purpose of scaffold fabrication, by taking into account the shear and slip flow from a tapered needle. Because the fluid flow behavior affects the flow rate, model equations were also developed from regression of experimental data to represent the flow behavior of alginate. The predictions from both the flow behavior equation and flow rate model show close agreement with experimental results. For varying needle diameters and temperatures, the slip effect occurring at the needle wall has a significant effect on the flow rate of alginate during scaffold fabrication.

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Figures

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Fig. 1

(a) Brookfield DV-III ultra rheometer and (b) its spindle and loading cup

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Fig. 2

Dispensing-based rapid prototyping machine for 3D scaffold fabrication: (a) 3D bioplotter, (b) bioplotter dispensing head, (c) tapered needle for dispensing head, (d) tapered needle with scale for length, (e) entrance diameter, and (f) 2% (w/v) alginate solution

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Fig. 3

(a) Schematic of 3D scaffold fabrication by bioplotter, (b) multiple layered alginate scaffold (scale bar = 0.2 mm), (c) printed alginate scaffold suspended in CaCl2 crosslinking solution, and (d) side view and (e) top view of the printed alginate scaffold

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Fig. 4

(a) Schematic of spindle cone and loading cup of Brookfield DV-III ultra rheometer; velocity profiles of alginate in the needle for boundary conditions (b) without slip and (c) and (d) with slip

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Fig. 5

Schematic of a tapered needle for a bioplotter head

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Fig. 6

Flow behavior curve for medium viscosity alginate: (a) 1%, (b) 2%, (c) 3%, and (d) 4%

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Fig. 7

Flow behavior parameters of medium viscosity alginate (1–4%) at various temperatures (25–55 °C): (a) consistency index, (b) yield stress, and (c) flow index

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Fig. 8

Experimental versus model-predicted flow behavior of 2.5% (w/v) alginate at different temperatures (25, 35, 45, and 55 °C): (a) consistency index, (b) yield stress, and (c) flow index; comparison plots (with diagonal line of equality) of measured and predicted data for (d) consistency index, (e) yield stress, and (f) flow index; experimental data are statistically significant (n = 3, p < 0.05)

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Fig. 9

Experimental versus model-predicted mass flow rate through a tapered needle (0.2 mm exit diameter) at 25 °C and various dispensing pressures (20, 25, 30, and 40 kPa) for (a) 2%, (b) 3%, and (c) 4% (w/v) alginate; comparison plot (with diagonal line of equality) of measured and predicted mass flow rate data for models (d) without slip and (e) with slip; and (f) distribution of residual prediction errors of mass flow rate data for model with slip (f); experimental data are statistically significant (n = 3, p < 0.05)

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Fig. 10

Bioplotter printed versus model-predicted strand width (with slip) for a tapered dispensing needle (0.2 mm exit diameter) at different dispensing pressures (20, 30, 40, and 50 kPa), needle speeds (6, 8, 10, 12, and 14 mm/s), and alginate concentrations of (a) 4% and (d) 3% (w/v); comparison plot (with diagonal line of equality) of measured and predicted strand width data for alginate concentrations of (b) 4% and (e) 3% (w/v); and distribution of residual prediction errors of strand width data for alginate concentrations of (c) 4% and (f) 3% (w/v). Experimental data are statistically significant for same needle speed and different dispensing pressures (n = 3; p < 0.05).

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Fig. 11

Model-predicted versus experimental mass flow rate of alginate (2% w/v) through a tapered needle with varying exit diameters (0.2, 0.25, 0.41, and 0.61 mm) at different temperatures (25, 35, 45, and 55 °C) and dispensing pressures of (a) 20 and (d) 30 kPa; comparison (with diagonal line of equality) of measured and predicted flow rates at dispensing pressures of (b) 20 and (e) 30 kPa; and distribution of residual prediction errors of flow rates at dispensing pressures of (c) 20 and (f) 30 kPa

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