scholarly journals Macro-scale topology optimization for controlling internal shear stress in a porous scaffold bioreactor

2012 ◽  
Vol 109 (7) ◽  
pp. 1844-1854 ◽  
Author(s):  
K. Youssef ◽  
J.J. Mack ◽  
M.L. Iruela-Arispe ◽  
L.-S. Bouchard
Keyword(s):  
Shear Stress ◽  
Topology Optimization ◽  
Porous Scaffold ◽  
Macro Scale

scholarly journals The Influence of Bioreactor Geometry and the Mechanical Environment on Engineered Tissues

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
J. M. Osborne ◽  
R. D. O’Dea ◽  
J. P. Whiteley ◽  
H. M. Byrne ◽  
S. L. Waters
Keyword(s):  
Shear Stress ◽  
Culture Medium ◽  
Porous Scaffold ◽  
Two Dimensional ◽  
Governing Equations ◽  
Long Wavelength ◽  
Wavelength Limit ◽  
Aspect Ratios ◽  
Three Phase ◽  
Tissue Construct

A three phase model for the growth of a tissue construct within a perfusion bioreactor is examined. The cell population (and attendant extracellular matrix), culture medium, and porous scaffold are treated as distinct phases. The bioreactor system is represented by a two-dimensional channel containing a cell-seeded rigid porous scaffold (tissue construct), which is perfused with a culture medium. Through the prescription of appropriate functional forms for cell proliferation and extracellular matrix deposition rates, the model is used to compare the influence of cell density-, pressure-, and culture medium shear stress-regulated growth on the composition of the engineered tissue. The governing equations are derived in O’Dea et al. “A Three Phase Model for Tissue Construct Growth in a Perfusion Bioreactor,” Math. Med. Biol., in which the long-wavelength limit was exploited to aid analysis; here, finite element methods are used to construct two-dimensional solutions to the governing equations and to investigate thoroughly their behavior. Comparison of the total tissue yield and averaged pressures, velocities, and shear stress demonstrates that quantitative agreement between the two-dimensional and long-wavelength approximation solutions is obtained for channel aspect ratios of order 10−2 and that much of the qualitative behavior of the model is captured in the long-wavelength limit, even for relatively large channel aspect ratios. However, we demonstrate that in order to capture accurately the effect of mechanotransduction mechanisms on tissue construct growth, spatial effects in at least two dimensions must be included due to the inherent spatial variation of mechanical stimuli relevant to perfusion bioreactors, most notably, fluid shear stress, a feature not captured in the long-wavelength limit.

Multiscale Topology Optimization for Additively Manufactured Objects

2018 ◽  
Vol 18 (3) ◽  
Author(s):  
John C. Steuben ◽  
Athanasios P. Iliopoulos ◽  
John G. Michopoulos
Keyword(s):  
Topology Optimization ◽  
Energy Deposition ◽  
Multiple Scales ◽  
Precise Control ◽  
Hand Tool ◽  
Macro Scale ◽  
Performance Specifications ◽  
Future Work ◽  
Am Processes ◽  
Meso Scale

The precise control of mass and energy deposition associated with additive manufacturing (AM) processes enables the topological specification and realization of how space can be filled by material in multiple scales. Consequently, AM can be pursued in a manner that is optimized such that fabricated objects can best realize performance specifications. In the present work, we propose a computational multiscale method that utilizes the unique meso-scale structuring capabilities of implicit slicers for AM, in conjunction with existing topology optimization (TO) tools for the macro-scale, in order to generate structurally optimized components. The use of this method is demonstrated on two example objects including a load bearing bracket and a hand tool. This paper also includes discussion concerning the applications of this methodology, its current limitations, a recasting of the AM digital thread, and the future work required to enable its widespread use.

NEW TRENDS IN TISSUE ENGINEERED CARTILAGE: MICROFLUID DYNAMICS IN 3-D ENGINEERED CELL SYSTEMS

2005 ◽  
Vol 05 (03) ◽  
pp. 455-464
Author(s):  
FEDERICA BOSCHETTI ◽  
MARGHERITA CIOFFI ◽  
MANUELA TERESA RAIMONDI ◽  
FRANCESCO MIGLIAVACCA ◽  
GABRIELE DUBINI
Keyword(s):  
Shear Stress ◽  
Flow Rate ◽  
Culture Medium ◽  
Porous Scaffold ◽  
Fluid Dynamic ◽  
Tissue Growth ◽  
Shear Stresses ◽  
Mechanical Stimuli ◽  
Micro Computed Tomography ◽  
Medium Flow

Bioreactors allowing culture medium direct-perfusion overcome diffusion limitations associated with static culturing and provide flow-mediated mechanical stimuli. The hydrodynamic stress imposed on chondrocytes will depend not only on the culture medium flow rate, but also on the scaffold three-dimensional (3D) micro-architecture. We performed computational fluid-dynamic (CFD) simulations of the flow of culture medium through a 3D porous scaffold, with the aim of predicting the shear stress acting on the cells as a function of parameters that can be set in a tissue-engineering experiment, such as the medium flow rate and the diameter of the perfused scaffold section. We developed two CFD models: the first model (Model 1) was built from micro-computed tomography reconstruction of the actual scaffold geometry, while the second model (Model 2) was based on a simplification of the actual scaffold microstructure. The two models showed comparable results in terms of the distribution of the shear stresses acting on the inner surfaces of the scaffold walls. Models 1 and 2 gave a median shear stress of 3 mPa at a flow rate of 0.5 cm3 min-1 through a 15 mm diameter scaffold. Our results provide a basis for the completion of more exhaustive quantitative studies to further assess the relationship between perfusion at known micro-fluid dynamic conditions and tissue growth in vitro.

Concurrent Topology Optimization of Lightweight Cellular Materials and Structures

2017 ◽  
Vol 868 ◽  
pp. 291-296
Author(s):  
He Ting Qiao ◽  
Shi Jie Wang ◽  
Xiao Ren Lv
Keyword(s):  
Topology Optimization ◽  
Material Design ◽  
Cellular Materials ◽  
Cellular Material ◽  
Design Stage ◽  
Concurrent Design ◽  
Design Variables ◽  
Macro Scale ◽  
Optimum Topology ◽  
Two Stages

In this paper, a two-stage optimization algorithm is proposed to simultaneously achieve the optimum structure and microstructure of lightweight cellular materials. Microstructure is assumed being uniform in macro-scale to meet manufacturing requirements. Furthermore, to reduce the computation cost, the design process is divided into two stages, which are concurrent design and material design. In the first stage, macro density and modulus matrix of cellular material are used both as design variables. Then, the optimum topology of macro-structure and modulus matrix of cellular materials will be obtained under this configuration. In the second stage, topology optimization technology is used to achieve a micro-structure of cellular material which is corresponded with the optimum modulus matrix in the earlier concurrent design stage. Moreover, the effectiveness of the present design methodology and optimization scheme is then demonstrated through numerical example.

Topology Optimization of a MEMS Resonator Using Hybrid Fuzzy Techniques

2008 ◽  
Author(s):  
Mohamed S. Senousy ◽  
Hesham A. Hegazi ◽  
Sayed M. Metwalli
Keyword(s):  
Topology Optimization ◽  
Random Search ◽  
Minimum Weight ◽  
Geometry Optimization ◽  
Gradient Projection ◽  
Stress Constraint ◽  
Complex Method ◽  
Search Technique ◽  
Mems Resonator ◽  
Macro Scale

This paper introduces a new methodology for the design of structures by geometry and topology optimization accounting for loading and boundary conditions as well as material properties. The Fuzzy Heuristic Gradient Projection (FHGP) method is used as a direct search technique for the geometry optimization, while the Complex Method (CM) is used as a random search technique for the topology optimization. In the proposed method, elements are designed such that they all have the same amount of stresses using the Fuzzy Heuristic Gradient Projection method. On the other hand, the complex method is used for the topology optimization step satisfying any constraint other than the stress constraint. The developed hybrid fuzzy technique is applied for different applications ranging from micro-scale to macro-scale applications. The method is applied to a micro-mechanical resonator as a microelectro-mechanical system (MEMS). The resonator is solved for minimum weight and is subjected to an equality frequency constraint and an inequality stress constraint. The proposed method is compared with the Multi-objective Genetic Algorithms (MOGAs) on solving the MEMS resonator. Results showed that the proposed hybrid fuzzy technique converges to optimum solutions faster than (MOGAs). The time consumed is improved by a 77%.

Design of Mesostructured Materials Under Uncertainty

2008 ◽  
Author(s):  
Jiten Patel ◽  
Seung-Kyum Choi
Keyword(s):  
Topology Optimization ◽  
Bulk Material ◽  
Synthesis Method ◽  
Latin Hypercube Sampling ◽  
Optimization Approach ◽  
Local Regression ◽  
Ground Structure ◽  
Structure Topology ◽  
Mesostructured Materials ◽  
Macro Scale

Uncertainties in material properties, geometry, manufacturing processes, and operational environments are clearly critical at all scales (nano-, micro-, meso-, and macro-scale). Specifically, reliabilty analysis in mesostructured materials can be driven by these uncertainties. The concept of mesostructured materials is motivated by the desire to put material only where it is needed for a specific application. This research develops a reliability-based synthesis method to design mesostructures under uncertainty, which have superior structural compliant performance per weight than parts with bulk material or foams. The efficiency of the proposed framework is achieved with the combination of topology optimization and stochastic approximation which utilizes stochastic local regression and Latin Hypercube Sampling. The effectiveness of the proposed framework was demonstrated using a ground structure topology optimization approach.

Modelling of Hysteresis Behavior of Ceramic Matrix Composites

2019 ◽  
Vol 795 ◽  
pp. 180-187
Author(s):  
Xue Feng Teng ◽  
Duo Qi Shi ◽  
Xiao Guang Yang
Keyword(s):  
Shear Stress ◽  
Sliding Friction ◽  
Hysteresis Loops ◽  
Ceramic Matrix Composites ◽  
Friction Stress ◽  
Ceramic Matrix ◽  
Static Friction ◽  
Matrix Composites ◽  
Hysteresis Behavior ◽  
Macro Scale

Under cyclic loading, the fiber-reinforced ceramic matrix composites exhibits hysteresis behavior due to the friction stress. When the matrix/fiber debonding occurs, the shear stress is transferred by friction stress on the debond surface. The friction stress is derived from the equilibrium equation of debond fiber in the unit cell. The result indicates that friction shear stress of a single debond fiber can be described by bilinear law due to the static friction and sliding friction. The nonlinear characteristic of friction stress at macro scale attributes to the distribution of the fiber pullout length. The hysteresis loops arise due to the friction stress and the shape is dominated by the evolution of friction during loading/unloading process. The model decoupled the shear stress into two independent terms: the first term represents the shear stress on well bond interface and the second term represents friction shear stress on debond interface. The method developed in this paper is employed to study the hysteresis behavior of C/SiC composite subjected to arbitrary cyclic load. The hysteresis behavior of C/SiC composite is predicted and compared with experimental data.

Towards Multiscale Topology Optimization for Additively Manufactured Components Using Implicit Slicing

2017 ◽  
Author(s):  
John C. Steuben ◽  
Athanasios P. Iliopoulos ◽  
John G. Michopoulos
Keyword(s):  
Topology Optimization ◽  
Complex Geometries ◽  
Generate Functional ◽  
Hand Tool ◽  
Macro Scale ◽  
Functional Features ◽  
Future Work ◽  
Functional Components ◽  
Am Processes ◽  
Meso Scale

Additive Manufacturing (AM) encompasses a set of fabrication technologies that are being used with increasing frequency in a wide variety of scientific and industrial pursuits. These technologies, which operate by successive additions of material to a domain, enable the manufacture of highly complex geometries that would otherwise be unrealizable. However, the material micro and meso-structures generated by AM processes differ remarkably from those that arise from conventional techniques and occasionally introduce unwanted functional features; this has been an obstacle to the use of AM in some applications. In the present work, we propose a multiscale method that utilizes the unique meso-scale structuring capabilities of implicit slicers for AM, in conjunction with existing topology optimization tools for the macro-scale, in order to generate functional components. The use of this method is demonstrated on the example of a hand tool. We discuss the applications of this methodology, its current limitations, and the future work required to enable its widespread use.

Multiscale Topology Optimization of Structures and Periodic Cellular Materials

2013 ◽  
Author(s):  
Kai Liu ◽  
Andrés Tovar
Keyword(s):  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Cellular Materials ◽  
Homogenization Theory ◽  
Design Algorithm ◽  
Macro Scale ◽  
Structural Applications ◽  
Potential Benefits ◽  
Penalization Methods ◽  
Scale Design

The introduction of cellular materials models in topology optimization allows designers to achieving significant weight reductions in structural applications. However, higher material savings and increased performance can be achieved if the material and the structure topologies are concurrently designed. The objective of this paper is to incorporate and establish a design methodology to obtaining optimal macro-scale structures and the corresponding optimal meso-scale periodic material designs in continuum design domains. The proposed approach makes use of homogenization theory to establish communication bridges between both material and structural scales. The periodicity constraint makes such cellular materials manufacturable. Penalization methods are used to obtaining binary solutions in both scales. This proposed methodology is demonstrated in the design of compliant mechanisms and structures of minimum compliance. The results demonstrate potential benefits when this multi-scale design algorithm when applied to the design of ultra-lightweight structures.

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