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1. Computational Design of Additively Manufactured Curvilinear Scaffolds for Bone Repair

   https://doi.org/10.1115/DETC2022-90582  

   Cohen, David O.; Aboutaleb, Sohaila M.; Wagoner Johnson, Amy; Norato, Julian A. (November 2022, International Design Engineering Technical Conferences and Computers and Information in Engineering Conference)

   This work introduces a computational method for designing ceramic scaffolds fabricated via direct ink writing (DIW) for maximum bone growth, whereby the deposited rods are curvilinear. A mechanobiological model of bone adaptation is used to compute bone growth into the scaffold, taking into account the shape of the defect, the applied loading, and the density distribution of bone in which the scaffold is implanted. The method ensures smooth, continuously varying rod contours are produced which are ideal for the DIW process. The method uses level sets of radial basis functions to fully define the scaffold geometry with a small number of design variables, minimizing the optimization’s computational cost. Effective elastic and diffusive properties of the scaffold as a function of the scaffold design and the bone density are obtained from previously constructed surrogates. These property surrogates are in turn used to perform bone adaptation simulations of the scaffold-bone system. Design sensitivities of the bone ingrowth within the scaffold are efficiently obtained using a finite difference scheme implemented in parallel. A demonstration of the methodology on a scaffold implanted in a pig mandible is presented. The scaffold is optimized to maximize bone ingrowth with geometric constraints to conform to the manufacturing process. 

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2. Parametric design and characterization of novel TPMS porous scaffolds for bone tissue engineering

   https://doi.org/10.1016/j.mfglet.2025.06.106  

   Smith, Haley; Hanlon, Hannah; Salary, Roozbeh “Ross” (August 2025, Manufacturing Letters)

   Mears, Laine (Ed.)

   Bone scaffolds are essential in regenerative medicine treatments for bone defects, fractures, and disease. Despite the popularity in bone scaffold research, many challenges still remain including mechanical strength. This study focuses on compression analysis of 10 novel bone scaffold designs with each design created using Rhino 7 with the Grasshopper extension. This coding software took existing scaffold design equations and converted them into 3D models utilizing code based on previous studies. The equations were created by combining and manipulating popular equations used for bone scaffold fabrication. The scaffold models were 3D printed using SimuBone, a PLA biomaterial known for its bone-like properties and printability. The results concluded that Design 6 had the highest compression modulus and mass/density, while Design 9 had a moderate compression modulus and mass/density. Design 8 had the lowest compression modulus and Design 2 had the lowest mass/density. Additionally, Design 6 exhibits the highest stiffness but increased weight, and Design 8 performs the worst in these categories. Therefore, Design 2 was the most optimal for balancing stiffness, mass, and density. The evolution of failure between all 10 designs was also analyzed. This concluded that Design 9 and Design 6 had the highest strength with minimal collapse. Design 8 had the lowest strength with little to no collapse, while Design 2 had medium compression strength with significant collapse. Although Design 2 was found to have significant collapse, it is still considered the most optimal scaffold within this study due to having the best overall mass/density ratio and stiffness modulus with a moderate compression strength. 

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3. Investigation of Material Transport Through Triply Periodic Minimal Surface (TPMS) Bone Scaffolds Using Computational Fluid Dynamics (CFD)

   https://doi.org/10.1115/MSEC2024-123878  

   Coburn, Brandon; Salary, Roozbeh “Ross” (June 2024, American Society of Mechanical Engineers (ASME))

   Abstract Cell-laden, scaffold-based tissue engineering methods have been successfully utilized for the treatment of bone fractures and diseases, caused by factors such as trauma, tumors, congenital anomalies, and aging. In such methods, the rate of scaffold biodegradation, transport of nutrients and growth factors, as well as removal of cell metabolic wastes at the site of injury are critical fluid-dynamics factors, affecting cell proliferation and ultimately tissue regeneration. Therefore, there is a critical need to identify the underlying material transport mechanisms and factors associated with cell-seeded, scaffold-based bone tissue engineering. The overarching goal of this study is to contribute to patient-specific, clinical treatment of bone pathology. The overall objective of the work is to establish computational fluid dynamics (CFD) models to identify: (i) the consequential mechanisms behind internal and external material transport through/over porous bone scaffolds and (ii) optimal triply periodic minimal surface (TPMS) scaffold designs toward cell-laden bone fracture treatment. In this study, 10 internal-flow and 10 external-flow CFD models were established using ANSYS, correspondingly based on 10 single-unit TPMS bone scaffold designs, where the geometry of each design was parametrically created using Rhinoceros 3D software. The influence of several design parameters, such as surface representation iteration, merged toggle iso value, and wall thickness, on geometry accuracy as well as computational time, was investigated in order to obtain computationally efficient and accurate CFD models. The fluid properties (such as density and dynamic viscosity) as well as the boundary conditions (such as no-slip condition, inlet flow velocity, and pressure outlet) of the CFD models were set based on clinical/research values reported in the literature as well as according to the fundamentals of internal/external Newtonian flow modeling. Several fluid characteristics, including flow velocity, flow pressure, and wall shear stress, were analyzed to observe material transport internally through and externally over the TPMS scaffold designs. Regarding the internal flow CFD modeling, it was observed that “P.W. Hybrid” (i.e., Design #7) had the highest-pressure output, with “Neovius” (i.e., Design #1) following second to it. These two designs have a relatively flatter surface area. In addition, “Schwarz P” (i.e., Design #2) was the lowest pressure output of all 10 TPMS designs. “Neovius” and “Schwarz P” had the highest and lowest values of wall shear stress. Besides, the velocity streamlines analysis showed an increase in velocity along the curved sections of the scaffolds’ geometry. Regarding the external flow CFD modeling, it was observed that “Neovius” yielded the highest-pressure output within the inlet section, which contains the area of the highest-pressure location. Furthermore, “Diamond” (i.e., Design #8) displayed having the highest values of wall shear stress due to the results of fluid interaction that accrues with complex curved structures. Also, when we look at designs like “Schwarz G”, the depiction of turbulent motion can be seen along the internal curved sections of the structure. As the external velocity streamlines decrease within the inner channels of the designs, this will lead to an increased pressure buildup due to the intrinsic interactions between the fluid with the walls. Overall, the outcomes of this study pave the way for optimal design and fabrication of complex, bone-like tissues with desired material transport properties for cell-laden, scaffold-based treatment of bone fractures. 

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4. Computational Fluid Dynamics Modeling of Material Transport Through Triply Periodic Minimal Surface Scaffolds for Bone Tissue Engineering

   https://doi.org/10.1115/1.4067575  

   Coburn, Brandon; Salary, Roozbeh “Ross” (March 2025, Journal of Biomechanical Engineering)

   Nguyen, Thao Vicky; Ethier, C Ross (Ed.)

   Abstract Cell-laden, scaffold-based tissue engineering methods have been successfully utilized for the treatment of bone fractures and diseases, caused by factors such as trauma, tumors, congenital anomalies, and aging. In such methods, the rate of scaffold biodegradation, transport of nutrients and growth factors, as well as removal of cell metabolic wastes at the site of injury are critical fluid-dynamics factors, affecting cell proliferation and ultimately tissue regeneration. Therefore, there is a critical need to identify the underlying material transport mechanisms and factors associated with cell-seeded, scaffold-based bone tissue engineering. The overarching goal of this study is to contribute to patient-specific, clinical treatment of bone pathology. The overall objective of the work is to establish computational fluid dynamics (CFD) models: (i) to identify the consequential mechanisms behind internal and external material transport through/over porous bone scaffolds designed based on the principles of triply periodic minimal surfaces (TPMS) and (ii) to identify TPMS designs with optimal geometry and flow characteristics for the treatment of bone fractures in clinical practice. In this study, advanced CFD models were established based on ten TPMS scaffold designs for (i) single-unit internal flow analysis, (ii) single-unit external flow analysis, and (iii) cubic, full-scaffold external flow analysis, where the geometry of each design was parametrically created. The influence of several design parameters, such as surface representation iteration, wall thickness, and pore size on geometry accuracy as well as computation time, was investigated in order to obtain computationally efficient and accurate CFD models. The fluid properties (such as density and dynamic viscosity) as well as the boundary conditions (such as no-slip condition, inlet flow velocity, and pressure outlet) of the CFD models were set based on clinical/research values reported in the literature, according to the fundamentals of internal and external Newtonian flow modeling. The main fluid characteristics influential in bone regeneration, including flow velocity, flow pressure, and wall shear stress (WSS), were analyzed to observe material transport internally through and externally over the TPMS scaffold designs. Regarding the single-unit internal flow analysis, it was observed that P.W. Hybrid and Neovius designs had the highest level of not only flow pressure but also WSS. This can be attributed to their relatively flat surfaces when compared to the rest of the TPMS designs. Schwarz primitive (P) appeared to have the lowest level of flow pressure and WSS (desirable for development of bone tissues) due to its relatively open channels allowing for more effortless fluid transport. An analysis of streamline velocity exhibited an increase in velocity togther with a depiction of potential turbulent motion along the curved sections of the TPMS designs. Regarding the single-unit external flow analysis, it was observed that Neovius and Diamond yielded the highest level of flow pressure and WSS, respectively, while Schwarz primitive (P) similarly had a relatively low level of flow pressure and WSS suitable for bone regeneration. Besides, pressure buildup was observed within the inner channels of almost all the TPMS designs due to flow resistance and the intrinsic interaction between the fluid flow and the scaffold walls. Regarding the cubic (full-scaffold) external flow analysis, the Diamond and Schwarz gyroid (G) designs appeared to have a relatively high level of both flow pressure and WSS, while Schwarz primitive (P) similarly yielded a low level of flow pressure and WSS. Overall, the outcomes of this study pave the way for optimal design and fabrication of complex, bone-like tissues with desired material transport properties for cell-laden, scaffold-based treatment of bone fractures. 

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5. A Simulation Approach to Determine Internal Architecture of 3D Bio-Printed Scaffold Suitable for A Perfusion Bioreactor

   Clark, S.; Quigley, C.; Mankowsky, J.; & Habib, M. A. (May 2023, Proceedings of the IISE Annual Conference & Expo 2023)

   Babski-Reeves, K; Eksioglu, B; Hampton, D. (Ed.)

   Traditional static cell culture methods don't guarantee access to medium inside areas or through the scaffolds because of the complex three-dimensional nature of the 3D bio-printed scaffolds. The bioreactor provides the necessary growth medium encapsulated and seeded cells in 3D bioprinted scaffolds. The constant flow of new growing medium could promote more viable and multiplying cells. Therefore, we created a specialized perfusion bioreactor that dynamically supplies the growth medium to the cells implanted or encapsulated in the scaffolds. A redesigned configuration of our developed bioreactor may enhance the in vivo stimuli and circumstances, ultimately improving the effectiveness of tissue regeneration. This study investigated how different scaffold pore shapes and porosities affect the flow. We employed a simulation technique to calculate fluid flow turbulence across several pore geometries, including uniform triangular, square, circular, and honeycomb. We constructed a scaffold with changing pore diameters to examine the fluid movement while maintaining constant porosity. The impact of fluid flow was then determined by simulating and mimicking the architecture of bone tissue. The best scaffold designs were chosen based on the findings. 

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