Effect of Fiber Form and Volume Fraction on Fiber-Reinforced Biomimicked Composites

Biomimicked composites have shown to be superior to monolithic structural materials. However, they need reinforcement to replace conventional load-bearing structural composites. Carbon Fibers in long and short forms were used as reinforcement in biomimicked composites. Mechanical tests including four point bending were conducted to determine the effects of form and volume fraction of fibers on the fracture toughness of the biomimicked composites.

Neck Pain Participant’s Perception of Traction Forces During Chiropractic Manual Cervical Distraction

In this exploratory study, we measured applied traction forces during a chiropractic manual cervical distraction procedure for each of three “treatment” perceptions; (i) beginning to feel a stretch, (ii) stretch feels like it could be a treatment, and (iii) stretch definitely feels like a treatment. A single trained clinician performed manual cervical distraction procedures on 10 neck pain participants using a commercially available table that was embedded with force and motion sensors. Participants were prone on the table while manual distraction was applied with gradually increasing force. When the specified perception was experienced, the study participant depressed a hand switch. Data was summarized with descriptive statistics and plotted for graphical analysis. Point estimates and 95% confidence intervals were calculated for the distractive force associated with each of the 3 treatment perceptions. Mean traction forces with 95% confidence intervals, corresponding to each of the 3 perception levels were: i) beginning to feel a stretch 18.6 N (11.9–25.2 N), ii) stretch feels like it could be a treatment 25.5 N (18.3–32.6 N), and iii) stretch definitely feels like a treatment 36.2 N (26.2–46.1 N).

Nonlinear FEA Simulation of Thorax Considering Transient CPR Forces and Sternotomy

The median sternotomy has become the desired incision in the modern era of cardiac surgery. The objective of this study is to investigate the sternum loading due to daily forces after sternotomy and during healing. Two models of thorax were built. The first is to simulate the healthy thorax and the second is to simulate the thorax after sternotomy and got closure using stainless steel stitches. In this paper, ANSYS was used to build the throax model. The results that have been collected after solving the model were analyzed. The analysis was promising and proved that the model was working properly and its ability to simulation what happens in the real life.

Force Controlled Manipulation of Biological Cells Using a Monolithic MEMS Based Nano-Micro Gripper

Nano-micro grippers are able to pick-transport-place the micro or nanometer–sized materials, such as manipulation of biological cells or DNA molecules in a liquid medium. This paper proposes a novel monolithic nano-micro gripper structure with two axis piezoresistive force sensor which its resolution is under nanoNewton. The results of the study have been obtained by the simulation of the proposed gripper structure in Matlab software. Motion of the gripper arm is produced by a voice coil actuator. The behavior of the cell has been derived using the assumptions in the literatures. Moreover, two simple PID controllers, one for control of the gripper motion and another for control of the force during manipulation of a biologic cell, have been implemented. Although the proposed gripper has not been fabricated, since the geometrical dimensions of the proposed gripper is the same as previously developed electrothermally actuated micro-nano gripper, the results of force control have been also compared with it. The simulated results with the very simple PID force controller which has a more rapid response than previously developed electrothermally actuated micro-nano gripper show that the designed gripper has the potential to be considered and fabricated for manipulation of biological cells in the future.

Ultrasound Hyperthermia: Dose Estimation and Device Design

As a cancer treatment modality, thermal ablation offers the advantages of being less invasive and posing fewer post-procedural complications compared to traditional cancer therapies. It involves destroying cancerous cells by subjecting them to the appropriate amount of heat dose. In the present study, high frequency ultrasound (US) ablation is theoretically examined for effectiveness as a treatment modality for intraluminal and extracorporeal cancer treatment. Objectives of this study are to 1) develop thermal-damage correlations for a variety of cancer cells and 2) design US treatment devices, based on thermal damage correlations developed, and treatment planning protocols. To achieve these goals, thermal damage information for different cell types is first determined from earlier studies or pilot experiments. Required US doses for specific tissues are determined next through numerical experiments. Device design and estimation of thermal coagulation contours is then performed by comparing temperature-history data against the thermal-damage data for a range of device parameters. Treatment protocols are finally developed based on the analysis of the results for a range of applicable device parameters. Results are presented in terms of correlations for the volume and location of ablated tissue corresponding to a range of operating parameter values.

A Comparative Study of the Human Body Finite Element Model Under Blast Loadings

Until today the modeling of human body biomechanics poses many great challenges because of the complex geometry and the substantial heterogeneity of human body. We developed a detailed human body finite element model in which the human body is represented realistically in both the geometry and the material properties. The model includes the detailed head (face, skull, brain, and spinal cord), the skeleton, and air cavities (including the lung). Hence it can be used to accurately acquire the stress wave propagation in the human body under various loading conditions. The blast loading on the human surface was generated from the simulated C4 blast explosions, via a novel combination of 1-D and 3-D numerical formulations. We used the explicit finite element solver in the multi-physics code CoBi for the human body biomechanics. This is capable of solving the resulting large system containing millions of unknowns in an extremely scalable fashion. The meshes generated for these simulations are of good quality. This enables us to employ relatively large time step sizes, without resorting to the artificial time scaling treatment. In order to study the human body dynamic response under the blast loading, we also developed an interface to apply the blast pressure loading on the external human body surface. These newly developed models were used to conduct parametric simulations to find out the brain biomechanical response when the blasts impact the human body. Under the same blast loading we also show the differences of brain response when having different material properties for the skeleton, the existence of other body parts such as torso.

Role of Plaque Morphology in Altering the Flow Characteristics in Diseased Coronary Artery

Patient specific simulations of a single patient based on an accurate representation of the plaque in a diseased coronary artery with 35% stenosis are performed to understand the effect of inlet forcing frequency and amplitude on the wall shear stress (WSS). Numerical simulations are performed with unsteady flow conditions in a laminar regime. The results have revealed that at low amplitudes, WSS is insensitive to forcing frequency and is it in phase with Q. The maximum WSS is observed at the proximal region of the stenosis, and WSS has highest negative values at the peak location of the stenosis. For higher pulsatile amplitude (a > 1.0), WSS exhibits a strong sensitivity with forcing frequencies. At higher forcing frequency the WSS exhibits nonlinear response to the inlet forcing frequency. Furthermore, significant differences in the mean velocity profile are observed during maximum and minimum volumetric flow rates.

KrioBlastTM: A Hyper-Fast Cooling and Thawing Scalable Device for Vitrification of Stem and Other Cells in Large Volumes

Kinetic (very rapid) vitrification (KVF) is a very promising approach in cryopreservation (CP) of biological materials as it is simple, avoids lethal intracellular ice formation (IIF) and minimizes damaging dehydration effects of extracellular crystallization. Moreover, achieving the ultra-high rates, which would prevent IIF during cooling and devitrification during resuscitation, and achieve KVF for practically any type of cells with one protocol of cooling and re-warming would be the “Holy Grail” of cell cryobiology [3]. However such hyperrapid rates currently require very small sample size which, however, is insufficient for many applications such as stem cells, blood or sperm. As the result, even smallest droplets of 0.25 microliters cannot be vitrified sufficiently fast to avoid the use of potentially toxic external vitrification agents such as DMSO or EG due to the Leidenfrost effect (LFE). In this presentation, we describe an entirely new system for hyperfast cooling of one-two order of magnitude larger samples that we call “KrioBlastTM”, which completely eliminates LFE. We have successfully vitrified up to 4,000 microliters of 15% glycerol solutions, which theoretically corresponds to the critical cooling rate of hundreds of thousands °C/min. We believe that such a system can revolutionize the future cryobiological paradigm.

Combustion Synthesis and Characterization of Porous NiTi Intermetallic for Structural Application

This paper describes experimental investigation of thermal and combustion phenomena as well as structure for self-propagating combustion synthesis of porous Ni–Ti intermetallic aimed for structural biomedical application. The objective is to correlate processing conditions with structure for the porous material. Ni–Ti mixture is prepared from elemental powders of Ni and Ti. The mixture is pressed into solid cylindrical samples of 1.1 cm diameter and 2–3 cm length, with initial porosity ranging from 30% to 42%. The samples are preheated to various initial temperatures and ignited from the top surface such that the flame propagates axially downwards. The flame images are recorded with a motion camera as well as the temperature profile. The samples were then cut using a diamond saw in both longitudinal and latitudinal directions. Image analysis software was then used to analyze the porosity distribution in each sample. The porosity distribution was then systematically correlated with the input processing conditions.

Experimental and Numerical Study of Soft Tissue Surrogate Behavior Under Ballistic Loading

Studying the high strain rate behavior of soft tissues and soft tissue surrogates is of interest to improve the understanding of injury mechanisms during blast and impact events. Tests such as the split Hopkinson pressure bar have been successfully used to characterize material behavior at high strain rates under simple loading conditions. However, experiments involving more complex stress states are needed for the validation of constitutive models and numerical simulation techniques for fast transient events. In particular, for the case of ballistic injuries, controlled tests that can better reflect the effects induced by a penetrating projectile are of interest. This paper presents an experiment that tries to achieve that goal. The experimental setup involves a cylindrical test sample made of a translucent soft tissue surrogate that has a small pre-made cylindrical channel along its axis. A small caliber projectile is fired through the pre-made channel at representative speeds using an air rifle. High speed video is used in conjunction with specialized software to generate data for model validation. A Lagrangian Finite Element Method (FEM) model was prepared in ABAQUS/Explicit to simulate the experiments. Different hyperelastic constitutive models were explored to represent the behavior of the soft tissue surrogate and the required material properties were obtained from high strain rate test data reported in the open literature. The simulation results corresponding to each constitutive model considered were qualitatively compared against the experimental data for a single projectile speed. The constitutive model that provided the closest match was then used to perform an additional simulation at a different projectile velocity and quantitative comparisons between numerical and experimental results were made. The comparisons showed that the Marlow hyperelastic model available in ABAQUS/Explicit was able to produce a good representation of the soft tissue surrogate behavior observed experimentally at the two projectile speeds considered.