Development and Characterization of a Portable Atmospheric-Pressure Argon Plasma Jet for Sterilization

In this study, we would like to develop a portable round argon atmospheric-pressure plasma jet (APPJ) which can be applied for general use of bacteria inactivation. The APPJ was characterized electrically and optically, which include measurements of absorption power, gas temperature and optical properties of plasma generated species. Measured OH* number density at 5 mm downstream was estimated to be 5.8 × 1015 cm−3 and the electron density and electron temperature were estimated to be 2.4 × 1015 cm−3 and 0.34 eV, respectively, in the discharge region. This APPJ was demonstrated to effectively inactivate E. coli within seconds of treatment, which shows its great potential in the future use of general bacteria inactivation and sterilization.

Design of an Electro-Mechanical Device for Knee Loading Applications

Mechanical loading of the knee is an innovative modality developed for rehabilitation of the knee joint as well as the femur and tibia that are subjected to bone fractures, osteoarthritis and osteoporosis. Loading essentially applies a lateral and periodic force to the knee joint [1]. In this paper, we propose the design of an electro-mechanical device that is capable of applying such dynamic loads. The key variable attributes of this device are the magnitude of the loading force, together with displacement and frequency. A DC motor with a controller actuates the device to produce the necessary force. The loading force is applied to the knee by a set of pads in a restricted linear motion. The operation of the device is approximated using the software package, SimMechanics of MATLAB. The simulations show that the device is capable of producing a suitable loading force with desired frequency. This simulation helps in constructing the device and performing experiments with appropriate frequencies. The device is expected to stimulate the fluids in porous skeletal matrix, resulting in strengthening the knee and bones. It can be employed for clinical trials for necessary evaluations and improvements.

Virtual Simulation of the Effects of Intracranial Fluid Cavitation in Blast-Induced Traumatic Brain Injury

A microscale model of the brain was developed in order to understand the details of intracranial fluid cavitation and the damage mechanisms associated with cavitation bubble collapse due to blast-induced traumatic brain injury (TBI). Our macroscale model predicted cavitation in regions of high concentration of cerebrospinal fluid (CSF) and blood. The results from this macroscale simulation directed the development of the microscale model of the superior sagittal sinus (SSS) region. The microscale model includes layers of scalp, skull, dura, superior sagittal sinus, falx, arachnoid, subarachnoid spacing, pia, and gray matter. We conducted numerical simulations to understand the effects of a blast load applied to the scalp with the pressure wave propagating through the layers and eventually causing the cavitation bubbles to collapse. Collapse of these bubbles creates spikes in pressure and von Mises stress downstream from the bubble locations. We investigate the influence of cavitation bubble size, compressive wave amplitude, and internal bubble pressure. The results indicate that these factors may contribute to a greater downstream pressure and von Mises stress which could lead to significant tissue damage.

Multi-Layer Construction Process for Fabricating Electrospun Fiber Embedded Microfluidic Devices

Microfluidic devices are widely used in biomedical applications owing to their inherent advantages. Microfabrication techniques are common methods for fabricating microfluidic devices, which require specialized equipment. This paper presents a multi-layer construction process for producing microfluidic devices via integrating two accessible fabrication techniques — hydrogel molding, a microfabrication-free method, and electrospinning (ES). The formed microchannels were examined via analyzing micrographs. Preliminary results demonstrate the feasibility of the method and potential for incorporating complex channels and device optimization.

Analysis of Passive Filling With Fibrotic Myocardial Infarction

Cardiovascular diseases account for one third of all deaths worldwide, more than 33% of which are related to ischemic heart disease, involving a myocardial infarction (MI). Following myocardial infarction, the injured region and ventricle undergo structural changes which are thought to be caused by elevated stresses and reduction of strains in the infarcted wall. The fibrotic phase is defined as the period when the amount of new collagen and number of fibroblasts rapidly increase in the infarcted tissue. We studied through finite element analysis the mechanics of the infarcted and remodeling rat heart during diastolic filling. Biventricular geometries of healthy and infarcted rat hearts reconstructed from magnetic resonance images were imported in Abaqus©. The passive myocardium was modelled as a nearly incompressible, hyperelastic, transversely isotropic material represented by the strain energy function W = ½C(eQ − 1) with Q = bfE112 + bt(E222 + E332 + E322) + bfs(E122 + E212 + E132 + E312). Material parameters were obtained from literature [1]. As boundary conditions, the circumferential and longitudinal displacements at the base were set to zero. The radial displacements at the base were left free. A linearly increasing pressure from 0 to 3.80 kPa and 0.86 kPa, respectively, was applied to the endocardial surfaces of left and right ventricle. Average radial, circumferential and longitudinal strains during passive filling were −0.331, 0.135, 0.042 and −0.250, −0.078 and 0.046 for the healthy heart and the infarcted heart, respectively. The average radial, circumferential and longitudinal stresses were −1.196 kPa, 3.87 kPa in the healthy heart and 0.424 kPa and −1.90 kPa, 8.74 kPa and 1.69 kPa in the infarcted heart. The strains were considerable lower in the infarcted heart compared to the health heart whereas stresses were higher in the presence of an infarct compared to the healthy case. The results of this study indicate the feasibility of the models developed for a more comprehensive assessment of mechanics of the infarcted ventricle including extension to account for cardiac contraction.

Fast CT-FFR Analysis Method for the Coronary Artery Based on 4D-CT Image Analysis and Structural and Fluid Analysis

Non invasive fractional flow reserve derived from CT coronary angiography (CT-FFR) has to date been typically performed using the principles of computational fluid analysis in which a lumped parameter coronary vascular bed model is assigned to represent the impedance of the downstream coronary vascular networks absent in the computational domain for each coronary outlet. This approach may have a number of limitations. It may not account for the impact of the myocardial contraction and relaxation during the cardiac cycle, patient-specific boundary conditions for coronary artery outlets and vessel stiffness. We have developed a novel approach based on 4D-CT image tracking (registration) and structural and fluid analysis based on one dimensional mechanical model, to address these issues. In our approach, we analyzed the deformation variation of vessels and the volume variation of vessels to better define boundary conditions and stiffness of vessels. We focused on the blood flow and vessel deformation of coronary arteries and aorta near coronary arteries in the diastolic cardiac phase from 70% to 100 %. The blood flow variation of coronary arteries relates to the deformation of vessels, such as expansion and contraction of the cross-sectional area, during this period where resistance is stable, pressure loss is approximately proportional to flow. We used a statistical estimation method based on a hierarchical Bayes model to integrate 4D-CT measurements and structural and fluid analysis data. Under these analysis conditions, we performed structural and fluid analysis to determine pressure, flow rate and CT-FFR. Furthermore, the reduced-order model based on fluid analysis was studied in order to shorten the computational time for 4D-CT-FFR analysis. The consistency of this method has been verified by a comparison of 4D-CT-FFR analysis results derived from five clinical 4D-CT datasets with invasive measurements of FFR. Additionally, phantom experiments of flexible tubes with and without stenosis using pulsating pumps, flow sensors and pressure sensors were performed. Our results show that the proposed 4D-CT-FFR analysis method has the potential to accurately estimate the effect of coronary artery stenosis on blood flow.

Shock Tube Design for High Fidelity Blast Wave Simulation

Traumatic brain injury (TBI) has been recognized as the signature wound of the current conflicts and it has been hypothesized that blast overpressure can contribute a significant pathway to TBI. As such, there are many ongoing research efforts to understand the mechanism to blast induced TBI, which all require blast testing using physical and biological surrogates either in the field or in the laboratory. The use of shock tubes to generate blast-like pressure waves in a laboratory can effectively produce the large amounts of data needed for research into blast induced TBI. A combined analytical, computational, and experimental approach was developed to design an advanced shock tube capable of generating high quality out-of-tube blast waves. The selected tube design was fabricated and laboratory tests at various blast wave levels were conducted. Comparisons of tube-generated laboratory data with explosive-generated field data indicated that the shock tube could accurately reproduce blast wave loading on test surrogates. High fidelity blast wave simulation in the laboratory presents an avenue to rapidly and inexpensively generate the large volumes of data necessary to validate and develop theories linking blast exposure to TBI.

Conceptual Design of an Active Transtibial Prosthesis Based on Expected Joint and Muscle Forces in a Unilateral Transtibial Amputee: A Modelling Study

Most modern active prostheses try to match the torque generated by the biological ankle in order to assist walking. However, due to the absence of a biarticular component like the gastrocnemius muscle, they are unable to provide complete rehabilitation. In this paper, a conceptual design of a prosthesis, having an active biarticular component is proposed; and it is studied if such a design can help in better rehabilitation of amputees. The muscle and joint forces during walking are predicted for three cases using musculoskeletal models: A healthy person, an Amputee wearing an active uniarticular prosthesis, and an Amputee wearing a prosthesis having active uniarticular as well as biarticular components (proposed design). Based on the required muscle forces and generated joint reaction loads, the proposed model performs better than the uniarticular prostheses.

A Computational Study of Fracture in the Calcaneus Under Variable Impact Conditions

This preliminary study aims to computationally model and study the fracture patterns in the human calcaneus during variable impact loading conditions. A finite element model of the foot and ankle is used to understand the effect of loading rates and orientation of the foot on fracture patterns. Simulations are carried out by applying varying impact velocities of steel plate to the foot & ankle model in accordance with data regarding underbody blasts. These impact velocities are applied to reach a peak in 1.5 ms. Fracture of bone is represented using the plastic kinematic constitutive model with element erosion method, where elements are removed from the simulation after an inelastic failure strain is exceeded. The simulations last for 5 ms to observe the extent of fracture in the calcaneus. Following simulations, the resulting fracture patterns are compared to available images from experimental impact tests to qualitatively assess the simufutions. A mesh convergence study is performed to determine the level of refinement of mesh necessary to represent this problem. The mesh appears to converge at the refinement level of the medium coarse mesh. The effect of impact velocities on fracture is studied on unjlexed and flexed foot models. At lower velocities, fracture is observed in the form of a single continuous crack, and a pronounced branched type of network is observed at higher velocities. Finally, variation in fracture networks due to variability in strength of the bone is studied. For lower values of failure strain, significantly larger and branched networks of fracture are observed.

Inter-Observer Variability of Vaginal Wall Segmentation From MRI: A Statistical Shape Analysis Approach

Pelvic floor disorders such as Pelvic Organ Prolapse (POP) negatively impact the health and quality of life of millions of women worldwide. POP is characterized by the descent of the pelvic organs into the vagina due to compromised connective tissue support, resulting in discomfort and urinary/fecal incontinence. Magnetic Resonance Imaging (MRI) has been used to aid in the quantification of these anatomical changes, however the inter- and intra-observer repeatability necessary to make reliable conclusions about changes in anatomical positioning is questioned using current methods. The aim of this study was to quantify the degree of variability produced from inter-observer manual tracings of the vagina from MRI scans using a statistical shape matching approach.