Biomechanical Engineering Commons^™

Innovative Biomechanical And Engineering-Based Assessments Of Hip Mechanics In Individuals With Hip-Related Pain, Holly M. Stanze

Theses and Dissertations--Kinesiology and Health Promotion

Individuals with hip-related pain exhibit altered movement patterns, and worse fear of movement (kinesiophobia), compared to asymptomatic controls. Exacerbation of hip pain during movement and the role of hip symptom duration may help further our understanding of specific movement patterns that are associated with hip-related pain. A better understanding of the potential connections between hip-related symptom duration, kinesiophobia, hip pain during movement, and lower limb mechanics in those with hip-related pain may allow for more efficient referrals to clinicians and lead to more effective rehabilitation. In addition, the impact of hip-related pain on intra-articular hip loading patterns is not well …

Simplified Molecular Diagnostics Methods For Environmental Testing Of Pathogens And Other Applications, Mohammad Dehghan Banadaki

Theses and Dissertations--Mechanical and Aerospace Engineering

Environmental Surveillance (ES) has emerged as a powerful tool to monitor the emergence and persistence of a pathogen within a facility or community using wastewater/water analysis. Over the past four years, implementation of ES has experienced an explosive acceleration, driven by efforts to monitor the spread of SARS-CoV-2, which has made ES a routinely used public health tool in many locations. We can now use ES to measure the emergence/presence/abundance of different viruses (e.g., SARS-CoV-2, influenza, mpox), bacteria (e.g., E. coli, V. cholerae, antibiotic-resistant strains), fungi (e.g., C. auris), and other biological markers indicative of infectious diseases. However, its broad …

Direct Numerical Simulation Of Pulsating Flow In Curved Pipes: Insights Into Aortic Dissection In Humans, Gokul Anugrah Gopakumar

Theses and Dissertations--Mechanical and Aerospace Engineering

This dissertation investigates the hemodynamics of pulsating blood flow in curved vessels through direct numerical simulations (DNS), with the overarching aim of uncovering fluid dynamic mechanisms linked to the onset and progression of aortic dissection in humans. The work is structured in two parts: (i) fundamental studies in idealized geometries and (ii) preliminary investigations in patient-specific anatomies. In the first part, curved pipe models representing the aortic arch are used to isolate the effects of pulsation frequency, amplitude ratio, and curvature ratio on transitional and turbulent flow dynamics. The simulations reveal that curvature-driven centrifugal forces shift the peak velocity toward …

Multiscale Fiber Remodeling In The Heart Using A Finite Element Framework, Mohammad Mehri

Theses and Dissertations--Mechanical and Aerospace Engineering

The organization of myofibers and extra cellular matrix within the myocardium plays a significant role in defining cardiac function. When pathological events occur, such as myocardial infarction (MI) or hypertrophic cardiomyopathy (HCM), this organization can become disrupted, leading to alteration in pumping performance. The current study proposes a multiscale finite element (FE) framework to determine realistic fiber distributions in the left ventricle (LV). This is achieved by implementing a stress-based fiber reorientation law, which seeks to align the fibers with local traction vectors, such that contractile force and load bearing capabilities are maximized. By utilizing the total stress (passive and …

Multiscale Modeling Of Cardiac Growth And Baroreflex Control, Hossein Sharifi

Theses and Dissertations--Mechanical and Aerospace Engineering

The heart functions within a complex system that adapts its function to any alteration in loading via several mechanisms. For example, the baroreflex is a short-term feedback loop that modulates the heart's function on a beat-to-beat basis to control arterial pressure. On the other hand, cardiac growth is a long-term adaptive response that occurs over weeks or months in response to changes in left ventricular loading. Understanding the mechanisms that drive ventricular growth and biological remodeling is critical to improving patient care. Multiscale models of the cardiovascular system have emerged as effective tools for investigating G&R, offering the ability to …

Modeling Human Control Behavior In Command-Following Tasks, Sajad Koushkbaghi

Theses and Dissertations--Mechanical and Aerospace Engineering

Humans interact with a variety of complex dynamic systems on a daily basis. However, they are often the lesser understood component of human-in-the-loop (HITL) systems. In this dissertation, we present the results of two HITL experiments to investigate the control strategies that humans use when performing command-following tasks. The first experiment is designed to investigate the control strategies that humans use to interact with nonlinear dynamic systems. Two groups of human subjects interact with a dynamic system and perform a command-following task. One group interacts with a linear time-invariant (LTI) dynamic system and the other group interacts with a Wiener …

Multiscale Finite Element Modeling Of Active Contraction In Striated Muscle, Charles Kurtis Mann

Theses and Dissertations--Mechanical and Aerospace Engineering

Greater than one in three American adults have at least one type of cardiovascular disease, a major cause of morbidity. Computational cardiac mechanics has become an important part of the research effort to understand the heart’s response to mechanical stimuli and as an extension, disease progression and potential therapies. To this end, the present work aims to extend these efforts by implementing a cell level contractile model in which active stress generation in muscle tissue is driven by half-sarcomere mechanics. This is accomplished by enhancing the MyoSim model of actin and myosin in order to produce a multiscale model. This …

Study Of Stress-Based Fiber Reorientation Law In A Finite Element Model Of Cardiac Tissue, Alexus Lori Rockward

Theses and Dissertations--Mechanical and Aerospace Engineering

Myofiber organization in the heart plays an important role in achieving and maintaining physiological cardiac function. In many cardiac disease states, myofibers and particularly cardiomyocytes are disorganized in chaotic patterns, a phenotype known broadly as myocardial disarray. In familial hypertrophic cardiomyopathy (HCM), this disorganization in the form of myocyte disarray is thought to contribute to impaired cardiac function and the development of arrhythmia during disease progression. However, the mechanisms regarding fiber reorientation in the heart are yet still unclear, and few adaptative laws have been created to explore these mechanisms. A stretch-based law was developed with the aim of achieving …

Cell And Biofilm Adhesion Strength Quantified By The Laser Spallation Technique Yields A Novel Biocompatibility Metric, The Adhesion Index, James Boyd

Theses and Dissertations--Mechanical and Aerospace Engineering

Implant associated infections are one of the leading causes of hospital acquired infections in the United States. Medical orthopedic implant devices are designed to improve adhesion of relevant cells within our body. In the case of orthopedic implants, osteoblast cells will adhere and allow for proper integration with the body’s bones. However, virulent bacteria will also adhere onto medical implants and proliferate into biofilms. Bacterial biofilms become extremely difficult to eradicate clinically as antibiotics are not as effective, resulting in severe infections or loss of implant. The aim of this research is to quantify the adhesion strength differential between relevant …

Atv Dynamics And Pediatric Rider Safety, James T. Auxier Ii

Theses and Dissertations--Biomedical Engineering

It has been observed through numerous academic and governmental agency studies that pediatric all-terrain vehicle ridership carries significant risk of injury and death. While no doubt valuable to safety, the post-hoc approach employed in these studies does little to explain the why and how behind the risk factors. Furthermore, there has been no prolonged, widespread, organized, and concerted effort to reconstruct and catalog the details and causes of the large (20,000+) number of ATV-related injuries that occur each year as has been done for road-based motor vehicle accidents. This dissertation takes the opposite approach from a meta-analysis and instead examines …

Effects Of A Hip Orthosis On Lumbopelvic Coordination In Individuals With And Without Low Back Pain, Colin Drury

Theses and Dissertations--Biomedical Engineering

Individuals with low back pain (LBP) demonstrate an abnormal lumbopelvic coordination compared to back-healthy individuals. This abnormal coordination presents itself as a reduction in lumbar contribution and an increase in pelvic contribution to trunk motion. This study investigated the ability of a hip orthosis to correct such an abnormal lumbo-pelvic coordination by restricting pelvic rotation and, as a result, increasing lumbar contributions. The effects of the hip orthosis on the magnitude and timing characteristics of lumbopelvic coordination were investigated in 20 patients with LBP and 20 asymptomatic controls. The orthosis significantly increased lumbar contributions by 11%, 5.42%, 4.84%, and 4.89% …

Electrophoresis In Heterogeneous Hydrogels And Applications In Surface Patterning, Ning Ge

Theses and Dissertations--Mechanical and Aerospace Engineering

The creation of chemical micropatterns on surfaces makes it possible to add unique chemical functionality to surfaces, modifying properties such as wettability, or even adding the ability to selectively bind other molecules. The creation of biochemical surface patterning in particular is useful in a variety of fields including tissue engineering and highthroughput drug screening. There are many existing surface patterning techniques which focus on precise control over the patterned geometry, even down to submicron scale features, but they do not allow local control over chemical concentration. So the results are high resolution patterns with binary concentration. There are also existing …

Bacterial Cell Wall Characterization Via Atomic Force And Confocal Microscopy, Joree Sandin

Theses and Dissertations--Mechanical and Aerospace Engineering

Poor oral hygiene is a severe global health issue, with about 44% of the Earth’s population suffering from untreated tooth decay, accounting for over $100 billion dollars spent on dental services per year in the United States, alone. Manual treatments, such as brushing, flossing, or swishing with antiseptic rinse are the main ways to alleviate harmful bacteria that cause these oral health problems. Streptococcus mutans (S. mutans) is a group of highly antibiotic, Gram-positive bacteria that heavily contribute to oral cavities, plaque build-up, and potential loosening or loss of dental implants if a biofilm develops. Currently, the mechanism …

Quantification Of Myocardial Mechanics In Left Ventricles Under Inotropic Stimulation And In Healthy Right Ventricles Using 3d Dense Cmr, Zhan-Qiu Liu

Theses and Dissertations--Mechanical and Aerospace Engineering

Statistical data from clinical studies indicate that the death rate caused by heart disease has decreased due to an increased use of evidence-based medical therapies. This includes the use of magnetic resonance imaging (MRI), which is one of the most common non-invasive approaches in evidence-based health care research. In the current work, I present 3D Lagrangian strains and torsion in the left ventricle of healthy and isoproterenol-stimulated rats, which were investigated using Displacement ENcoding with Stimulated Echoes (DENSE) cardiac magnetic resonance (CMR) imaging. With the implementation of the 12-segment model, a detailed profile of regional cardiac mechanics was reconstructed for …

Quantification Of Papillary Muscle Motion And Mitral Regurgitation After Myocardial Infarction, Connor R. Ferguson

Theses and Dissertations--Mechanical and Aerospace Engineering

Change in papillary muscle motion as a result of left ventricular (LV) remodeling after posterolateral myocardial infarction is thought to contribute to ischemic mitral regurgitation. A finite element (FE) model of the LV was created from magnetic resonance images acquired immediately before myocardial infarction and 8 weeks later in a cohort of 12 sheep. Severity of mitral regurgitation was rated by two-dimensional echocardiography and regurgitant volume was estimated using MRI. Of the cohort, 6 animals (DC) received hydrogel injection therapy shown to limit ventricular remodeling after myocardial infarction while the control group (MI) received a similar pattern of saline injections. …

A Computational Study Of Patch Implantation And Mitral Valve Mechanics, Dara Singh

Theses and Dissertations--Mechanical and Aerospace Engineering

Myocardial infarction (i.e., a heart attack) is the most common heart disease in the United States. Mitral valve regurgitation, or the backflow of blood into the atrium from the left ventricle, is one of the complications associated with myocardial infarction. In this dissertation, a validated model of a sheep heart that has suffered myocardial infarction has been employed to study mitral valve regurgitation. The model was rebuilt with the knowledge of geometrical changes captured with MRI technique and is assigned with anisotropic, inhomogeneous, nearly incompressible and highly non-linear material properties. Patch augmentation was performed on its anterior leaflet, using a …

Lower Back Biomechanics At Non-Chronic Stage Of Low Back Pain, Iman Shojaei

Theses and Dissertations--Biomedical Engineering

Prior studies have reported differences in lower back biomechanics during activities of daily living between individuals with and without chronic low back pain (LBP). Nevertheless, the literature on lower back biomechanics of patients with non-chronic LBP is scant. Therefore, the objective of this study, as the first step towards future prospective studies, was to investigate the lower back biomechanics in patients with non-chronic LBP. Case-control studies were conducted wherein measures of lumbo-pelvic coordination during bending and return tasks as well as measures of mechanical demand on the lower back during lifting tasks in the sagittal plane were investigated between patients …

Design And Analysis Of A 3d-Printed, Thermoplastic Elastomer (Tpe) Spring Element For Use In Corrective Hand Orthotics, Kevin Thomas Richardson

Theses and Dissertations--Mechanical and Aerospace Engineering

This thesis proposes an algorithm that determine the geometry of 3D-printed, custom-designed spring element bands made of thermoplastic elastomer (TPE) for use in a wearable orthotic device to aid in the physical therapy of a human hand exhibiting spasticity after stroke. Each finger of the hand is modeled as a mechanical system consisting of a triple-rod pendulum with nonlinear stiffness at each joint and forces applied at the attachment point of each flexor muscle. The system is assumed quasi-static, which leads to a torque balance between the flexor tendons in the hand, joint stiffness and the design force applied to …

Age-Related Differences In The Lumbopelvic Kinematics During The Trunk Motions In The Anatomical Planes, Milad Vazirian

Theses and Dissertations--Biomedical Engineering

Management and control of the low back pain as an important health problem in the industrial societies necessitates to investigate how the risk of this disease is affected by aging. Since the abnormalities of the lumbopelvic kinematics are related to the existence or risk of low back injuries, the objective of this dissertation was set to find the age-related differences in lumbopelvic kinematics when performing basic trunk motions reaching to range of motion in different anatomical planes.

A cross-sectional study was designed where sixty asymptomatic individuals between 20–70 years old with no confounding health condition, no current or previous highly …

Computational Investigation Of Transmural Differences In Left Ventricular Contractility And Hydrogel Injection Treatment For Myocardial Infarction, Hua Wang

Theses and Dissertations--Mechanical and Aerospace Engineering

Heart failure (HF) is one of the leading causes of death and impacts millions of people throughout the world. Recently, injectable hydrogels have been developed as a potential new therapy to treat myocardium infarction (MI). This dissertation is focused on two main topics: 1) to gain a better understanding the transmural contractility in the healthy left ventricle (LV) wall and 2) investigate the efficacy of the hydrogel injection treatment on LV wall stress and function. The results indicate that a non-uniform distribution of myocardial contractility in the LV wall provide a better representation of normal LV function. The other important …

Biventricular Finite Element Modeling And Quantification Of 3d Langragian Strains And Torsion Using Dense Mri, Zhanqiu Liu

Theses and Dissertations--Mechanical and Aerospace Engineering

Statistical data suggests that increased use of evidence-based medical therapies has largely contributed to the decrease in American death rate caused by heart disease. And my studies are about two applications of magnetic resonance imaging (MRI) as a non-invasive approach in evidence-based health care research. In my first study, the achievement of a pulmonary valve replacement surgery was assessed on a patient with tetralogy of Fallot (TOF). In order to evaluate the remodeling of right ventricle, two biventricular finite element models were built up for pre-surgical images and post-surgical images. In my second study, 3D Lagrangian strains and torsion in …

Computational Modeling Of Cardiac Biomechanics, Amir Nikou

Theses and Dissertations--Mechanical and Aerospace Engineering

The goal of this dissertation was to develop a realistic and patient-specific computational model of the heart that ultimately would help medical scientists to better diagnose and treat heart diseases. In order to achieve this goal, a three dimensional finite element model of the heart was created using magnetic resonance images of the beating pig heart. This model was loaded by the pressure of blood inside the left ventricle which was measured by synchronous catheterization. A recently developed structurally based constitutive model of the myocardium was incorporated in the finite element solver to model passive left ventricular myocardium. Additionally, an …

Computational Investigation Of Injectable Treatment Strategies For Myocardial Infarction, Hua Wang

Theses and Dissertations--Mechanical and Aerospace Engineering

Heart failure is an important medical disease and impacts millions of people throughout the world. In order to treat this problem, biomaterial injectable treatment injected into the myocardium of the failing LV are currently being developed. Through this treatment, the biomaterial material injections can reduce wall stresses during the cardiac remodeling process. By using computational techniques to analyze the effects of a treatment involving the injection of biomaterial material into the LV after MI, the material parameters of the hydrogel injections can be optimized. The results shows that the hydrogel injections could reduce the global average fiber stress and the …

Estimating Passive Material Properties And Fiber Orientation In A Myocardial Infarction Through An Optimization Scheme Using Mri And Fe Simulation, Dimitri Mojsejenko

Theses and Dissertations--Mechanical and Aerospace Engineering

Myocardial infarctions induce a maladaptive ventricular remodeling process that independently contributes to heart failure. In order to develop effective treatments, it is necessary to understand the way and extent to which the heart undergoes remodeling over the course of healing. There have been few studies to produce any data on the in-vivo material properties of infarcts, and much less on the properties over the time course of healing. In this paper, the in-vivo passive material properties of an infarcted porcine model were estimated through a combined use of magnetic resonance imaging, catheterization, finite element modeling, and a genetic algorithm optimization …

Fabrication Of Magnetic Two-Dimensional And Three-Dimensional Microstructures For Microfluidics And Microrobotics Applications, Hui Li

Theses and Dissertations--Mechanical and Aerospace Engineering

Micro-electro-mechanical systems (MEMS) technology has had an increasing impact on industry and our society. A wide range of MEMS devices are used in every aspects of our life, from microaccelerators and microgyroscopes to microscale drug-delivery systems. The increasing complexity of microsystems demands diverse microfabrication methods and actuation strategies to realize. Currently, it is challenging for existing microfabrication methods—particularly 3D microfabrication methods—to integrate multiple materials into the same component. This is a particular challenge for some applications, such as microrobotics and microfluidics, where integration of magnetically-responsive materials would be beneficial, because it enables contact-free actuation. In addition, most existing microfabrication methods …

Entrainment Of Electrical Activation By Spatio-Temporal Distributed Pacing During Ventricular Fibrillation, Yiping Gu

University of Kentucky Master's Theses

Spatio-temporal variation in action intervals during ventricular fibrillation (VF) suggestthat the excitable gap may also be distributed spatio-temporally. The observation leadus to hypothesize that distributed pacing can be used to modify and entrain electricalactivation during VF. We tested this hypothesis using simulated VF and animal studies.

We simulated VF in a 400 by 400 cell matrix. Simulation results showed that activationpattern could be entrained using spatially distributed stimulation. Up to a certain limit,increasing stimulus strength and density led to improved entrainment. Best entrainmentwas obtained by pacing at a cycle length similar to the intrinsic cycle length.

In order to verify …