Passive Mechanical Analysis of Engineered Myotube Fibers

The loss of functional muscle as a product of genetic disease, traumatic injury, or surgical excisions results in a physiological deficiency that still remains without an effective clinical treatment [1]. Engineering of functional tissue in vitro for replacement in vivo might pose as a potential remedy for this clinical demand. By approaching tissue engineering from the bottom-up, geometrically directing myoblast growth provides a means for constructing tissue replacements cell-by-cell versus the traditional decellularized construct that remains limited by its size and ability to deliver cellular nutrients. Furthermore, geometrically controlling the growth of myoblasts allows for direct manipulation of the structural and mechanical properties inherent to muscular tissue.

Visualization of CFD Results in a Virtual Reality Environment

Imaging modalities such as computed tomography, 3D ultrasound and magnetic resonance imaging (MRI) facilitate detailed viewing of vascular geometries [1], but lack the ability to directly measure important hemodynamic parameters associated with the onset and progression of cardiovascular disease (i.e. pressure, wall shear stress) [2]. Computational fluid dynamics (CFD) is a noninvasive tool to quantify these indices in vessels reconstructed from imaging data. Although image-based CFD can be used to relate altered hemodynamics to vascular disease, a disjunction exists between information gathered from 4-D CFD (3 spatial dimensions and time) and the 2-D screens where results are typically displayed. In contrast, 3D virtual reality environments can be used to visualize CFD results in a comprehensive manner.

CFD Comparison of Steady and Unsteady Flow Through a Human Nasal Passage

Understanding of the transnasal pressure and flow behavior during normal breathing conditions has been a subject of much discussion and research. In particular we are interested in testing the hypothesis of quasi-steady flow as well as the role of turbulence on nasal flow dynamics.

Gait Prediction Using Concurrent Musculoskeletal Control and FE Simulations

Current computational methods of simulating activities of daily living (ADL) have primarily consisted of musculoskeletal simulations [1]. Due to computational expense, simulations generally include assumptions which simplify joint or soft-tissue behavior. Joints are modeled as hinge or spherical and soft-tissue effects are included as spring-dashpot systems. Incorporating detailed deformable soft-tissue models would help overcome simplifying assumptions by coupling the behavior of a muscle loaded model with the underlying structures. Important clinical applications for a multi-domain simulation framework include, but are hardly limited to, predicting modifications to ADL to compensate for osteoarthritic pain or minimizing peak plantar pressures, which are believed to be significant for diabetic foot ulceration.

Intracranial Aneurysm Morphology and Flow Dynamics to Assess Rupture Risk

The effectiveness of Intracranial Aneurysm (IA) size as a predictor for rupture has been debated. The confusing trends observed *unicefwhile stratifying IA rupture risk according to IA size may have arisen from overlooking its morphology and size relative to its parent vessel.

Effects of Reduced Compliance on Endothelial Functionality With Regards to Inflammation

The aging process is associated with a stiffening of the arteries. In this study we focused on how reduced wall compliance induces pulse pressure-mediated changes in endothelial function with regards to inflammation and adhesion.

A Two-Dimensional Model of Particle Motion in Ureteral Peristaltic Flow

Physiological fluids in human or animals are, in general, propelled by the continuous periodic muscular contraction or expansion (or both) of the ducts through which the fluids pass, a phenomenon known as peristalsis. Peristaltic mechanisms may be involved in the swallowing of food through the esophagus, vasomotion of small blood vessels, spermatic flows in the ductus efferentes, embryo transport in the uterus, and transport of urine through the ureters, among others [1]. Peristaltic fluid flow can be accompanied by solid particles. In this work the Basset-Boussinesq-Oseen (BBO) equation will be employed to analyze particle motion in peristaltic fluid flow, this model considers motion of a small spherical particle suspended in a nonuniform fluid flow and diverse forces are considered. In ureteral peristaltic flow, fluid being transported is essentially Newtonian and incompressible. Ureteral peristaltic flow is sometimes accompanied by particles such as stones or bacteria. In the present study, the geometrical form of the peristaltic wave will be taken to be sinusoidal. The governing equations are Navier-Stokes for the fluid and momentum for the particle (BBO equation). A regular perturbation series in which the variables are expanded in a power series of the wavenumber (ε = πRw/λ) is used to solve the fluid problem. One-way coupling between the fluid and particles is assumed.

Validation of a New Finite Element Model for Human Knee Ligaments for Use in High Speed Automotive Collisions

A finite element model of knee human ligaments was developed and validated to predict the injury potential of occupants in high speed frontal automotive collisions. Dynamic failure properties of ligaments were modeled to facilitate the development of more realistic dynamic representation of the human lower extremities when subjected to a high strain rate. Uniaxial impulsive impact loads were applied to porcine medial collateral ligament-bone complex with strain rates up to145 s−1. From test results, the failure load was found to depend on ligament geometric parameters and on the strain rate applied. The information obtained was then integrated into a finite element model of the knee ligaments with the potential to be used also for representation of ligaments in other regions of the human body. The model was then validated against knee ligament dynamic tolerance tests found in literature. Results obtained from finite element simulations during the validation process agreed with the outcomes reported by literature findings encouraging the use of this ligament model as a powerful and innovative tool to estimate ligament human response in high speed frontal automotive collisions.

An Alternative Technique for Dielectrophoretic (DEP) Cell Manipulation: Contact-Less DEP

Dielectrophoresis (DEP), the motion of a particle due to its polarization in the presence of a non-uniform electric field, can be used as an alternative to current sample enrichment techniques [1]. While the technique has been proven effective, most DEP devices must be manufactured using complicated processes. Insulator-based dielectrophoresis (iDEP) is a practical method to obtain the selectivity of dielectrophoresis while overcoming the robustness issues associated with traditional dielectrophoresis platforms [2]. While both of these methods allow for the differentiation of cells based upon their intrinsic electrical properties, they require direct contact between electrodes and a sample fluid, which can induce fouling, bubble formation and unwanted electrochemical effects [3]. We have developed an alternative method to provide the spatially non-uniform electric field required for DEP in which electrodes are not in direct contact with the biological sample. In this method, an electric field is created in the sample microchannel using electrodes inserted into two other microchannels (filled with conductive solution), which are separated from the sample microchannel by thin insulating barriers. These insulating barriers exhibit a capacitive behavior and therefore an electric field can be produced in the main channel by applying an AC field across them. The absence of contact between electrodes and the sample fluid inside the channel prevents bubble formation and avoids any contaminating effects the electrodes may have on the sample.

Mechanical Anisotropy of Individual Osteons in Bone Tissue at High Spatial Resolutions

Secondary osteons, the fundamental units of cortical bone, consist of cylindrical lamellar composites composed of mineralized collagen fibrils. Due to its lamellar structure, a multiscale knowledge of the mechanical properties of cortical bone is required to understand the biomechanical function of the tissue. In this light, nanoindentation tests were performed along the axial and transverse directions following a radial path from the Haversian canal to the osteonal edges. Different length scales are explored by means of indentations at different maximum penetration depths. Indentation moduli and hardness data were then interpreted in the context of the known microstructure. Results suggest that secondary osteons hierarchical structure is responsible for an observed length scale effect, homogenization phenomena and anisotropy of mechanical properties.