Modeling of multifunctional deformable porous scaffolds for soft tissue engineering

Porous membranes/scaffolds such as guided tissue regeneration (GTR) membranes, cell sheets, tissue matrices or polymeric meshes are being widely used in soft tissue engineering to regenerate damaged, diseased tissue or wound. These membranes are mostly regular porous structures with repeating internal architecture. When they are applied onto wound area, various forces caused by bandage, contraction and self weight might cause deformation. As a result, the geometry and the designed porosity changes which eventually alters the desired choreographed functionality. To avoid the negative effect cause by such deformation and its associated consequences, a novel design methodology has been proposed to determine and include the resultant deformation. The proposed design will minimize the variation in effective porosity while ensuring its surface conformity. Thus the proposed design will provide a better functionality by providing both structural integrity and proper biological properties. The proposed methodology has been implemented and results will be shown with illustrative examples. Also a comparison study showing effective porosity for both the proposed method and conventional regular porosity will be presented for a free-form surface mimicking a wound

Solution of the Bosonic and Algebraic Hamiltonians by using AIM

We apply the notion of asymptotic iteration method (AIM) to determine eigenvalues of the bosonic Hamiltonians that include a wide class of quantum optical models. We consider solutions of the Hamiltonians, which are even polynomials of the fourth order with the respect to Boson operators. We also demonstrate applicability of the method for obtaining eigenvalues of the simple Lie algebraic structures. Eigenvalues of the multi-boson Hamiltonians have been obtained by transforming in the form of the single boson Hamiltonian in the framework of AIM

Design and analysis of a reconfigurable discrete pin tooling system for molding of three-dimensional free-form objects

This paper presents the design and analysis of a new reconfigurable tooling for the fabrication of three-dimensional (3D) free-form objects. The proposed reconfigurable tooling system comprises a set of matrices of a closely stacked discrete elements (i.e., pins) arranged to form a cavity in which a free-form object can be molded. By reconfiguring the pins, a single tool can be used in the place of multiple tools to produce different parts with the involvement of much lesser time and cost. The structural behavior of a reconfigurable mold tool under process conditions of thermoplastic molding is studied using a finite element method (FEM) based methodology. Various factors that would affect the tool behavior are identified and their effects are analyzed to optimally design a reconfigurable mold tool for a given set of process conditions. A prototype, open reconfigurable mold tool is developed to present the feasibility of the proposed tooling system. Several case studies and sample parts are also presented in this paper

Designing bio-mimetic variational porosity for tissue scaffolds

Reconstructing or repairing the damaged or diseased tissues with porous scaffolds to restore the mechanical, biological and chemical functions is one of the major tissue engineering strategies. Development of Solid Free Form (SFF) techniques and improvement in biomaterial properties by synergy have provided the leverage to fabricate controlled and interconnected porous scaffold structures. But homogeneous scaffolds with regular porosity do not provide all the biological and mechanical requirements of an ideal tissue scaffold. Thus achieving controllable, continuous, interconnected gradient porosity with reproducible and fabricatable design is critical for successful regeneration of the replaced tissue. In this research, a novel scaffold modeling approach has been proposed to achieve bio-mimetic tissue scaffolds. Firstly, the optimum filament deposition angle has been determined based on the internal heterogeneous regions and their locations. Then an area-weight based approach has been applied to generate the spatial porosity function to determine the filament deposition location for the desired bio-mimetic porosity. The proposed methodology has been implemented using computer simulation. A micro-nozzle biomaterial deposition system driven by NC motion control has been used to fabricate a sample designed structure

An information theory based behavioral model for agent-based crowd simulations

Crowds must be simulated believable in terms of their appearance and behavior to improve a virtual environment’s realism. Due to the complex nature of human behavior, realistic behavior of agents in crowd simulations is still a challenging problem. In this paper, we propose a novel behavioral model which builds analytical maps to control agents’ behavior adaptively with agent-crowd interaction formulations. We introduce information theoretical concepts to construct analytical maps automatically. Our model can be integrated into crowd simulators and enhance their behavioral complexity. We made comparative analyses of the presented behavior model with measured crowd data and two agent-based crowd simulators

Functionally heterogeneous porous scaffold design for tissue engineering

Most of the current tissue scaffolds are mainly designed with homogeneous porosity which does not represent the spatial heterogeneity found in actual tissues. Therefore engineering a realistic tissue scaffolds with properly graded properties to facilitate the mimicry of the complex elegance of native tissues are critical for the successful tissue regeneration. In this work, novel bio-mimetic heterogeneous porous scaffolds have been modeled. First, the geometry of the scaffold is extracted along with its internal regional heterogeneity. Then the model has been discretized with planner slices suitable for layer based fabrication. An optimum filament deposition angle has been determined for each slice based on the contour geometry and the internal heterogeneity. The internal region has been discritized considering the homogeneity factor along the deposition direction. Finally, an area weight based approach has been used to generate the spatial porosity function that determines the filament deposition location for desired biomimetic porosity. The proposed methodology has been implemented and illustrative examples are provided. The effective porosity has been compared between the proposed design and the conventional homogeneous scaffolds. The result shows a significant error reduction towards achieving the biomimetic porosity in the scaffold design and provides better control over the desired porosity level. Moreover, sample designed structures have also been fabricated with a NC motion controlled micro-nozzle biomaterial deposition system