Department of Biomedical Engineering and Mechanics

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https://hdl.handle.net/10919/24216
A collaboration between School of Biomedical Engineering and Sciences and the Department of Engineering Science and Mechanics to form the Department of Biomedical Engineering and Mechanics.

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Browsing Department of Biomedical Engineering and Mechanics by Content Type "Article"

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    A biologically accurate model of directional hearing in the parasitoid fly Ormia ochracea
    Mikel-Stites, Max R.; Salcedo, Mary K.; Socha, John J.; Marek, Paul E.; Staples, Anne E. (Cold Spring Harbor Laboratory, 2021-09-17)
    Although most binaural organisms localize sound sources using neurological structures to amplify the sounds they hear, some animals use mechanically coupled hearing organs instead. One of these animals, the parasitoid fly Ormia ochracea, has astoundingly accurate sound localization abilities and can locate objects in the azimuthal plane with a precision of 2°, equal to that of humans. This is accomplished despite an intertympanal distance of only 0.5 mm, which is less than 1/100th of the wavelength of the sound emitted by the crickets that it parasitizes. In 1995, Miles et al. developed a model of hearing mechanics in O. ochracea, which works well for incoming sound angles of less than ±30°, but suffers from reduced accuracy (up to 60% error) at higher angles. Even with this limitation, it has served as the basis for multiple bio-inspired microphone designs for decades. Here, we present critical improvements to the classic O. ochracea hearing model based on information from 3D reconstructions of O. ochracea’s tympana. The 3D images reveal that the tympanal organ has curved lateral faces in addition to the flat front-facing prosternal membranes represented in the Miles model. To mimic these faces, we incorporated spatially-varying spring and damper coefficients that respond asymmetrically to incident sound waves, making a new quasi-two-dimensional (q2D) model. The q2D model has high accuracy (average errors of less than 10%) for the entire range of incoming sound angles. This improved biomechanical hearing model can inform the development of new technologies and may help to play a key role in developing improved hearing aids. Significance Statement: The ability to identify the location of sound sources is critical to organismal survival and for technologies that minimize unwanted background noise, such as directional microphones for hearing aids. Because of its exceptional auditory system, the parasitoid fly Ormia ochracea has served as an important model for binaural hearing and a source of bioinspiration for building tiny directional microphones with outsized sound localization abilities. Here, we performed 3D imaging of the fly’s tympanal organs and used the morphological information to improve the current model for hearing in O. ochracea. This model greatly expands the range of biological accuracy from ±30° to all incoming sound angles, providing a new avenue for studies of binaural hearing and further inspiration for fly-inspired technologies.
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    Biomechanics of hair cell kinocilia: experimental measurement of kinocilium shaft stiffness and base rotational stiffness with Euler-Bernoulli and Timoshenko beam analysis
    Spoon, Corrie E.; Grant, John Wallace (Company of Biologists, 2011-03-01)
    Vestibular hair cell bundles in the inner ear contain a single kinocilium composed of a 9+2 microtubule structure. Kinocilia play a crucial role in transmitting movement of the overlying mass, otoconial membrane or cupula to the mechanotransducing portion of the hair cell bundle. Little is known regarding the mechanical deformation properties of the kinocilium. Using a force-deflection technique, we measured two important mechanical properties of kinocilia in the utricle of a turtle, Trachemys (Pseudemys) scripta elegans. First, we measured the stiffness of kinocilia with different heights. These kinocilia were assumed to be homogenous cylindrical rods and were modeled as both isotropic Euler-Bernoulli beams and transversely isotropic Timoshenko beams. Two mechanical properties of the kinocilia were derived from the beam analysis: flexural rigidity (El) and shear rigidity (kGA). The Timoshenko model produced a better fit to the experimental data, predicting El=10,400 pN mu m(2) and kGA=247 pN. Assuming a homogenous rod, the shear modulus (G=1.9 kPa) was four orders of magnitude less than Young's modulus (E=14.1 MPa), indicating that significant shear deformation occurs within deflected kinocilia. When analyzed as an Euler-Bernoulli beam, which neglects translational shear, El increased linearly with kinocilium height, giving underestimates of El for shorter kinocilia. Second, we measured the rotational stiffness of the kinocilium insertion (kappa) into the hair cell's apical surface. Following BAPTA treatment to break the kinocilial links, the kinocilia remained upright, and kappa was measured as 177 +/- 47 pN mu m rad(-1). The mechanical parameters we quantified are important for understanding how forces arising from head movement are transduced and encoded by hair cells.
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    Blasted Flies and Nanoparticles for TBI
    Hockey, Kevin S.; Sholar, Christopher A.; Sajja, Venkata Siva Sai Sujith; Hubbard, W. Brad; Thorpe, Chevon; VandeVord, Pamela J.; Rzigalinski, Beverly A. (Brain Injuries and Biomechanics Symposium, 2013-09-19)
    This presentation briefly summaries two major areas of work in our lab, development of a Drosophila model of blast injury and treatment of traumatic brain injury (TBI) with cerium oxide nanoparticles. First, we discuss the design, methodology, and results for the Drosophila blast model, and its relevance to human head injury. Briefly, we found that the Drosophila model was able to reproduce the decreased lifespan and early death seen in military personnel exposed to repetitive mild blast and NFL players exposed to repeated mild head injury. Next we discuss our in vitro and in vivo work with cerium oxide nanoparticles as neuroprotective and regenerative agents for treatment of TBI. Using a tissue culture model for TBI, we found that cerium oxide nanoparticles, delivered up to 6 hrs. post-injury, improved neuronal survival and maintained near-normal glutamate signaling in neurons of mixed organotypic brain cell cultures. In vivo, we found that delivery of cerium oxide nanoparticles prior to lateral fluid percussion brain injury in the rat, improved motor performance, learning and memory.
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    Editorial: 'Engineering the Tumor Immune Microenvironment' Special Issue
    Ahmad, Raffae N.; Verbridge, Scott S. (MDPI, 2023-08-08)
    Cancer immunotherapies, while promising and occasionally even curative, encounter numerous hurdles within the tumor microenvironment that hinder their efficacy [...]
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    Editorial: Local Hydrodynamics of Benthic Marine Organisms
    Staples, Anne E.; Miller, Laura A.; Khatri, Shilpa; Hossain, Md Monir (Frontiers, 2023-03-28)
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    Evaluation of Eye Injury Risk from Consumer Fireworks
    Alphonse, Vanessa D.; Kemper, Andrew R. (Brain Injuries and Biomechanics Symposium, 2013-09-19)
    Eye injuries affect approximately two million people annually. Various experimental studies have been performed to evaluate potentially injurious conditions from blunt objects using animal and human cadaver eyes. Experimental data from these studies have been used to develop injury risk curves to predict eye injuries based on projectile parameters such as kinetic energy and normalized energy. Recently, intraocular pressure (IOP) has been correlated to injury risk, which allows eye injuries to be predicted if projectile characteristics are unknown. Additionally, the measurement of IOP and the association of IOP to injury risk in experimental tests has opened up the field to studying eye injury mechanisms from overpressure. The current manuscript presents recent experimental tests that evaluated the response of human cadaver eyes exposed to firework overpressure. Consumer fireworks serve as a model of low level blast, and provides a foundation to studying higher blast overpressures (i.e., that would be observed in military combat). Although some studies state that eye injury can result solely from primary blast (overpressure), there is no empirical evidence in the literature to support this. Future experimental studies should be conducted to assess this statement.
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    Implementing Head Impact Sensors in Collegiate Men’s and Women’s Rugby: Successes and Challenges in Characterizing Concussion
    Kieffer, Emily E.; Rowson, Steven (Virginia Tech, 2022-01-29)
    Head impact sensors allow researchers to learn more about human tolerance to head impact exposure and concussion. Previous on-field data collection has worked to quantify concussion biomechanics, based primarily on helmeted male athletes. Data from unhelmeted and female athletes still need to be collected and quantified to understand how concussion tolerance varies by sex and loading environment. The primary goal of this study was to instrument collegiate rugby players with head impact sensors embedded in mouthguards and to report head impact and concussion biomechanics. Over four seasons of data collection, four males and 15 females sustained concussions. To reduce underreporting, we collected weekly graded symptom surveys from all players. Kinematics were only collected for two male concussions and three female concussions due to different challenges with the instrumentation. The secondary goal of this study was to discuss head impact sensors that are used on-field and explore their practicality and limitations. We present our experience using two instrumented mouthguards, the Wake Forest Instrumented Retainer and the Prevent Biometrics Intelligent Instrumented Mouthguard, to measure head impacts in athletes. Not enough injury data were collected to quantify unhelmeted concussion tolerance. Still, the following reports may provide foundational and reference cases for future research, in addition to discussion of data quality, sex-specific athlete compliance, general usability, and provide recommendations for future head impact sensor use.
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    Infographic: ACL injury reconstruction and recovery
    Queen, Robin M. (British Editorial Society of Bone and Joint Surgery, 2017)
    Anterior cruciate ligament (ACL) injury is a considerable source of morbidity among athletes. Most ACL injuries (70%) are non-contact in nature, with women and patients aged between 15 and 30 years at particularly high risk.¹,₂ The vast majority of patients undergo surgical reconstruction, with annual costs associated with treatment and rehabilitation of ACL injuries estimated at $3 billion. While the risk of primary ACL injury has been studied extensively, there is limited understanding of the risk factors for secondary ACL injuries, and how these are related to return-to-play (RTP) assessments. RTP decisions often do not rely on objective measures of function, but are instead based on the time since surgical intervention.³,⁴ However, many athletes have residual muscle imbalances, muscle weakness, and altered lower extremity mechanics at the time of RTP that may persist for up to two years following ACL reconstruction.⁵,⁶ With the current return to sport decision metrics, up to 29% of all ACL reconstruction patients will suffer a secondary tear. The identified risk factors for secondary ACL injury have been focused on deficits in movement mechanics. Specifically, movement and loading asymmetry (knee extension moment asymmetry) between the surgical and non-surgical limbs, as well as an increase in frontal plane range of motion, have been identified as secondary ACL injury risk factors.⁷ Based on the increased risk for secondary ACL tears, and the knowledge that 45% of individuals will develop knee osteoarthritis within ten years of an ACL reconstruction, it is imperative that objective and measurable criteria are used when determining readiness to return to sports in order to decrease the risk of a secondary injury.⁸
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    Literature Review of Eye Injuries and Eye Injury Risk from Blunt Objects
    Alphonse, Vanessa D.; Kemper, Andrew R. (Brain Injuries and Biomechanics Symposium, 2013-09-19)
    Eye injuries affect approximately two million people annually. Various studies that have evaluated the injury tolerance of animal and human eyes from blunt impacts are summarized herein. These studies date from the late 60s to present and illustrate various methods for testing animal and human cadaver eyes exposed to various blunt projectiles including metal rods, BBs, baseballs, and foam pieces. Experimental data from these studies have been used to develop injury risk curves to predict eye injuries based on projectile parameters such as kinetic energy and normalized energy. Recently, intraocular pressure (IOP) has been correlated to injury risk which allows eye injuries to be predicted when projectile characteristics are unknown. These experimental data have also been used to validate numerous computational and physical models of the eye used to assess injury risk from blunt loading. One such physical model is the the Facial and Ocular CountermeasUre Safety (FOCUS) headform, which is an advanced anthropomorphic device designed specifically to study facial and ocular injury. The FOCUS headform eyes have a biofidelic response to blunt impact and eye load cell data can be used to assess injury risk for eye injuries.
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    Measuring Head Impact Exposure and Mild Traumatic Brain Injury in Humans
    Cobb, Bryan (Brain Injuries and Biomechanics Symposium, 2013-09-19)
    Helmeted sports such as football offer a unique opportunity to study head injury biomechanics in live human subjects. Impact reconstruction using game videos and real-time measurements of head kinematics in football provide a method of quantifying the head impact exposure athletes experience. A total of 58 impacts from NFL games have been reconstructed using Hybrid III crash test dummies, including 25 concussive impacts. Roughly 2 million impacts have been recorded using helmet-mounted accelerometer devices, with 105 concussive impacts. Similar values have been found for peak linear acceleration, one of the best predictors of concussion, using the two methods. From the NFL impact reconstructions, researchers found a peak linear acceleration value of 98 ± 28 g which is not substantially different from the value of 105 ± 27 g from the helmet-mounted sensor data. Both methods provide valuable head impact biomechanics data which are used to quantify impact exposure in football and assess injury risk due to head impact. Helmet mounted accelerometers have the added benefit of collecting every impact a player sustains while wearing the sensors, giving more detailed impact frequency data and many more data points. Future research will focus on expanding the head impact data set, especially at the youth level. The expanded data set will lead to improved injury risk curves which will guide future safety standards in sports as well as other areas, including the automotive industry and military, where head injury is a concern.
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    Nonlinear one-dimensional constitutive model for magnetostrictive materials
    Imhof, Alecsander N.; Domann, John P. (2022-02-08)
    This paper presents an analytic model of one dimensional magnetostriction. We show how specific assumptions regarding the symmetry of key micromagnetic energies (magnetocrystalline, magnetoelastic, and Zeeman) reduce a general three-dimensional statistical mechanics model to a one-dimensional form with an exact solution. We additionally provide a useful form of the analytic equations to help ensure numerical accuracy. Numerical results show that the model maintains accuracy over a large range of applied magnetic fields and stress conditions extending well outside those produced in standard laboratory conditions. A comparison to experimental data is performed for several magnetostrictive materials. The model is shown to accurately predict the behavior of Terfenol-D, while two compositions of Galfenol are modeled with varying accuracy. To conclude we discuss what conditions facilitate the description of materials with cubic crystalline anisotropy as transversely isotropic, to achieve peak model performance.
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    Predicting Mild Traumatic Brain Injury with Injury Risk Functions
    Young, Tyler James (Brain Injuries and Biomechanics Symposium, 2013-09-19)
    To assess the safety of various products, equipment, and vehicles during traumatic events injury risk curves have been developed correlate measurable parameters with risk of injury. The first risk curves to predict head injuries focused on severe head injuries such as skull fractures. These curves were generated by impacting cadaver heads. To understand the biomechanics of mild traumatic brain injuries, cadaver heads have also been used to monitor pressure and strain in the brain during impacts. Live animal models have been used to understand the physiological response of the brain to impact to create thresholds for mild traumatic brain injuries such as concussions. These results have been scaled to humans. To generate injury risk curves from live human models, impacts from games in the NFL have been reconstructed in the laboratory. Helmets of NCAA football players have also be instrumented with accelerometers to collect all impacts during a season resulting in the development of injury risk curves that predict concussion as a function of both linear and rotational acceleration. These risk curves provide researchers with a better understanding of the efficacy of various safety systems and give insight as to how safety systems can be improved.
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    Propagating fronts in fluids with solutal feedback
    Mukherjee, Saikat; Paul, Mark R. (American Physical Society, 2020-03-25)
    We numerically study the propagation of reacting fronts in a shallow and horizontal layer of fluid with solutal feedback and in the presence of a thermally driven flow field of counterrotating convection rolls. We solve the Boussinesq equations along with a reaction-convection-diffusion equation for the concentration field where the products of the nonlinear autocatalytic reaction are less dense than the reactants. For small values of the solutal Rayleigh number the characteristic fluid velocity scales linearly, and the front velocity and mixing length scale quadratically, with increasing solutal Rayleigh number. For small solutal Rayleigh numbers the front geometry is described by a curve that is nearly antisymmetric about the horizontal midplane. For large values of the solutal Rayleigh number the characteristic fluid velocity, the front velocity, and the mixing length exhibit square-root scaling and the front shape collapses onto an asymmetric self-similar curve. In the presence of counterrotating convection rolls, the mixing length decreases while the front velocity increases. The complexity of the front geometry increases when both the solutal and convective contributions are significant and the dynamics can exhibit chemical oscillations in time for certain parameter values. Last, we discuss the spatiotemporal features of the complex fronts that form over a range of solutal and thermal driving.
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    Response to 'Comment on Linear inviscid wave propagation in a waveguide having a single boundary discontinuity: Part II: Application [J. Acoust. Soc. Am. 75, 356-362 (1984)]'
    Thompson, Charles (Acoustical Society of America, 1986-10-01)
    This paper addresses the comments of Dr. Bruggeman and Dr. van de Wetering. The source of the error present in the paper entitled "Linear inviscid wave propagation in a waveguide having a single boundary discontinuity: Part II: Application is addressed. A rational fraction approximation for the transmission coefficient is presented.
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    Surrogate Head Forms for the Evaluation of Head Injury Risk
    MacAlister, Anna (Brain Injuries and Biomechanics Symposium, 2013-09-19)
    This paper summarizes the use of surrogate head forms in biomechanical research pertaining to head injury and, more specifically, mild traumatic brain injury. Because cadavers are limited and controlled studies of brain injury using live human subjects would be unethical, surrogate head forms are used to study the response of the human head to impact. Different head forms have been developed and optimized for different purposes. The Hybrid III 50th percentile male crash test dummy was developed for use in vehicle crash testing and instrumented in such a way as to provide HIC values in frontal crash tests. The NOCSAE head form is used by the National Operating Committee on Standards for Athletic Equipment to be used in the certification of commercially produced athletic helmets. The Facial and Ocular Countermeasure Safety (FOCUS) head form was developed jointly by the Virgina Tech-Wake Forest Center for Injury Biomechanics, Robert A. Denton, Inc., and the United States Army Aeromedical Research Laboratory as a tool to aid in the development and evaluation of safety devices designed to prevent face and eye injuries. The vast majority of biomechanical research of head injury conducted using surrogate anthropomorphic test devices (ATDs) utilized one of these three head forms.
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    Terrain classification using intelligent tire
    Khaleghian, Seyedmeysam; Taheri, Saied (Pergamon, 2017)
    A wheeled ground robot was designed and built for better understanding of the challenges involved in utilization of accelerometer-based intelligent tires for mobility improvements. Since robot traction forces depend on the surface type and the friction associated with the tire-road interaction, the measured acceleration signals were used for terrain classification and surface characterization. To accomplish this, the robot was instrumented with appropriate sensors (a tri-axial accelerometer attached to the tire innerliner, a single axis accelerometer attached to the robot chassis and wheel speed sensors) and a data acquisition system. Wheel slip was measured accurately using encoders attached to driven and non-driven wheels. A fuzzy logic algorithm was developed and used for terrain classification. This algorithm uses the power of the acceleration signal and wheel slip ratio as inputs and classifies all different surfaces into four main categories; asphalt, concrete, grass, and sand. The performance of the algorithm was evaluated using experimental data and good agreements were observed between the surface types and estimated ones.
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    Virginia Tech Hockey Helmet Ratings Memorandum
    Rowson, Steven; Begonia, Mark T.; Rowson, Bethany M.; Duma, Stefan M. (Virginia Tech, 2022-01-25)
    This memorandum serves to reiterate the goals of the Virginia Tech Helmet Ratings, discuss the hockey helmet ratings, and announce an update to the exposure weightings and star thresholds used to rate hockey helmets.