A. James Clark School of Engineering

Permanent URI for this communityhttp://hdl.handle.net/1903/1654

The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

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ENHANCING BIOPRINTING STRATEGIES TOWARDS THE DEVELOPMENT OF BIOMIMETIC OSTEOCHONDRAL TISSUE ENGINEERING SCAFFOLDS
(2023) Choe, Robert; Fisher, John P; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Osteoarthritis is a highly prevalent rheumatic musculoskeletal disorder that affects approximately 900,000 Americans annually and is characterized by the progressive breakdown of the articular cartilage and remodeling of the subchondral bone in the synovial joint. During early-stage osteoarthritis, the articular cartilage begins to degrade, the synovial joint space narrows, and the subchondral bone undergoes rapid bone turnover, leading to insufficient bone mineralization and compromised matrix integrity. While decades of research have revealed that an intricate balance between the bone and cartilage layers influences biochemical and biomechanical changes experienced within the osteochondral unit, most osteochondral tissue engineering scaffolds have not achieved clinical viability. Tissue engineering (TE) strategies, such as 3D bioprinting (3DP), offer a new avenue to help develop novel osteochondral tissue engineering scaffolds to regenerate healthy and diseased osteochondral joints. In this project, our immediate goal is to expand the repertoire of osteochondral bioprinting strategies toward developing a biomimetic, 3D-printed osteochondral scaffold that can be implanted into acute focal cartilage defects during early-stage OA. We will explore the designs and fabrication strategies of various 3D-printed biomimetic osteochondral interface scaffolds with enhanced mechanics guided by computational simulations. Additionally, we will examine the potential of utilizing osteoblast- and osteoclast-lineage cell co-cultures to improve regenerative outcomes at the bone scaffold layer of osteochondral tissue engineering scaffolds. The long-term goal of this work is to aid in developing a biomimetic 3D printed osteochondral scaffold that has enhanced load-bearing properties and elevated regeneration potential to recreate the unique osteochondral architecture at each distinct tissue layer.
INSTRUMENTATION AND AUTOMATION FOR STIMULATED BRILLOUIN SPECTROSCOPY
(2023) Frank, Eric; Scarcelli, Giuliano; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The use of Brillouin spectroscopy for noninvasive probing of the mechanical properties of biologically relevant materials shows great promise. Stimulated Brillouin scattering (SBS) spectroscopy has the potential to significantly improve measurement speed and resolution by amplifying the scattered signal resonantly. However, current SBS spectrometers have been limited by fundamental and practical constraints in detection parameters. Here, we develop and demonstrate a novel LabVIEW-automated SBS instrumentation scheme in which a number of instruments that otherwise operate independently are automatized and synchronized from a singular LabVIEW program with emphasis on the user interface. Additionally, localization theory, originating from fluorescence-based super resolution microscopy techniques, is applied to the acquisition of SBS spectra, and experimentally demonstrated using this instrumentation scheme, resulting in spectra being acquired an order of magnitude faster while maintaining performances in terms of signal to noise ratio (SNR) and measurement precision.
Dynamics of Elastic Capsules in Cross-Junction and T-Junction Microfluidic Channels
(2017) Mputu udipabu, Pompon; Dimitrakopoulos, Panagiotis; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
In this dissertation, we investigate via numerical computations the dynamicsof elastic capsules (made from a thin strain-hardening elastic membrane) in two microfluidic channels of cross-junction and T-junction geometries. For the cross-junction microfluidic channel, we consider an initially spherical capsule with a size smaller than the cross-section of the square channels comprising the cross-junction, and investigate the effects of the capsule size, flow rate, and lateral flow rates on the transient dynamics and deformation of low-viscosity and equiviscous capsules. In addition, we also study the effects of viscosity ratio on the transient capsule dynamics and deformation. Our investigation shows that the intersecting lateral flows at the cross-junction act like a constriction. Larger capsules, higher flow rates and higher intersecting lateral flows result in stronger hydrodynamic forces that cause a significant capsule deformation, i.e., the capsule’s length increases while its height decreases significantly. The capsule obtains different dynamic shape transitions due to the asymmetric shape of the cross-junction. Larger capsules take more time to pass through the cross-junction owning to the higher flow blocking. As the viscosity ratio decreases, the capsule’s transient deformation increases and tail formation develops transiently, especially for low-viscosity capsules owing to the normal-stress effects of the surrounding fluid on the capsule’s interface. However, the viscosity ratio does not affect much the capsule velocity due to a weak inner circulation. Our findings suggest that the tail formation of low-viscosity capsule may promote membrane breaking and thus drug release of pharmaceutical capsules in the microcirculation. Furthermore, we investigate via numerical computations the motion of an elastic capsule (made from an elastic membrane obeying the strain-hardening Skalak law) flowing inside a microfluidic T-junction device. In particular, we consider the effects of the capsule size, flow rate, lateral flow rate, and fluid viscosity ratio on the motion of the capsule in the T-junction micro-channel. As the capsule’s initial lateral position increases, the capsule moves faster and reaches different final lateral positions. As the capsule size increases, the gap between the capsule’s surface and the channel wall decreases. This results in the development of stronger hydrodynamic forces and a decrease in the capsule velocity due to flow blocking. As the capsule size increases, there is a small lateral migration towards the micro-channel centerline, which is the low-shear region of the T-junction micro-channel. This migration is in agreement with experimental and numerical studies on non-inertial lateral migration of vesicles in bounded Poiseuille flow by Coupier et al. [13] who showed that the combined effects of the walls and of the curvature of the velocity profile induce a lateral migration toward the centerline of the channel. As the capillary number Ca increases, the stronger hydrodynamic forces cause the capsule to extend along the flow direction (i.e., the capsule’s length Lx increases as the capsule enters the T-junctions and decreases as the capsule exits the T-junction). There is a small lateral migration away from the micro-channel centerline as the flow rate Ca increases. The capsule lateral position zc, main-flow velocity Ux and migration velocity Uz are practically not affected by the fluids viscosity ratio λ. As the channel’s lateral flow rate increases, the capsule migrates downwards towards the bottom of the device. Our findings on the lateral migration in the T-junction micro-channel suggest that there is a great potential for designing a T-junction microfluidic device that can be used to manipulate artificial and biological capsules.
Quantitative Motion Analysis of the Upper Limb: Establishment of Normative Kinematic Datasets and Systematic Comparison of Motion Analysis Systems
(2022) Wang, Sophie Linyi; Kontson, Kimberly L; White, Ian; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Upper limb prosthetic devices with advanced capabilities are currently in development. With these advancements brings to light the importance of objectively and quantitatively measuring effectiveness and benefit of these devices. Recently, the application of motion capture (i.e., digital tracking of upper body movements in space) to performance-based outcome measures has gained traction as a possible tool for human movement assessment that could facilitate optimal device selection, track rehabilitative progress, and inform device regulation and review. While motion capture shows promise, the clinical, regulatory, and industry communities would benefit from access to large clinical and normative datasets from different motion capture systems and a better understanding of advantages and limitations of different motion capture approaches. The first objective of this dissertation is to establish kinematic datasets of normative and upper-limb prosthesis user motion. The normative kinematic distributions of many performance-based outcome measures are not established, and it is difficult to determine departures from normative patterns without relevant clinical expertise. In Specific Aim 1, normative and clinically relevant datasets were created using a gold standard motion capture system to record participants performing standardized tasks from outcome measures. Without kinematic data, it is also difficult to identify informative kinematic features and tasks that exhibit characteristic differences from normative motion. The second objective is to identify salient kinematic characteristics associated with departures from normative motion. In Specific Aim 2, an unsupervised K-means machine learning algorithm was applied to the previously collected data to determine motions and tasks that distinguish between normative and prosthesis user movement. The third objective is to compare three commonly used motion capture systems that vary in motion tracking mechanisms. The most informative tasks and kinematic characteristics previously identified will be used to evaluate the detection of these differences for several motion capture systems with varying tracking methods in Specific Aim 3.
Rupture Mechanisms Of Porcine And Human Ascending Aortic Tissue Under Dynamic Translational Shear Deformation
(2021) Harwerth, Jason W.; Haslach, Henry W; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Tissue Engineered Vascular Grafts (TEVGs) may be grown in living pigs to further their development towards use in humans to repair damaged aorta. To explore whether porcine grown TEVGs are good models for human grown TEVGs, normal human and porcine aortic tissues are loaded in shear deformation to compare the differences in the dissection response of these viscoelastic tissues. Shear is strongly related to aortic dissection. Translational constant rate and sinusoidal shear deformation tests characterize dynamic mechanical properties of aortic tissue. Knowledge of the tissue microstructure helps determine the effect of interstitial fluid-solid interaction on the shear response of the specimens. Transient and quasi-periodic response characteristics provide baseline material properties of normal porcine aortic tissue to compare its dissection resistance with TEVG porcine aortic tissue. The results show that normal porcine aortic tissue is sufficiently similar to human aortic tissue to justify the continued development of porcine grown TEVG models.
Brillouin confocal microscopy in off-axis configuration
(2021) Fiore, Antonio; Scarcelli, Giuliano; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Three-dimensional Brillouin confocal microscopy is an imaging modality that correlates with mechanical properties in biological media from subcellular to tissue level. Over the years we developed new approaches to this technique that improve the spectral performance and can measure directly the local refractive index as well as the complex modulus of the sample; to achieve this goal, we probed two co-localized Brillouin scattering geometries. The confocal microscopy setting ensures three-dimensional mapping with high resolution, while the back scattering configuration allows access to the sample from the same side. For these reasons, such an instrument constitutes a new approach in investigating biological phenomena providing both local index of refraction and mechanical information with a single measurement. This technique has been improved in speed and spatial resolution in order to be applied to some specific challenging material characterization such as liquid-liquid phase separation.
Biomechanical and functional variation in rat sciatic nerve following cuff electrode implantation
(Springer Nature, 2014-04-23) Restaino, Stephen M; Abliz, Erkinay; Wachrathit, Kelliann; Krauthamer, Victor; Shah, Sameer B
Nerve cuff electrodes are commonly and successfully used for stimulating peripheral nerves. On the other hand, they occasionally induce functional and morphological changes following chronic implantation, for reasons not always clear. We hypothesize that restriction of nerve mobility due to cuff implantation may alter nerve conduction. We quantified acute changes in nerve-muscle electrophysiology, using electromyography, and nerve kinematics in anesthetized Sprague Dawley rat sciatic nerves during controlled hindlimb joint movement. We compared electrophysiological and biomechanical response in uncuffed nerves and those secured within a cuff electrode using analysis of variance (ANOVA) and regression analysis. Tethering resulting from cuff implantation resulted in altered nerve strain and a complex biomechanical environment during joint movement. Coincident with biomechanical changes, electromyography revealed significantly increased variability in the response of conduction latency and amplitude in cuffed, but not free, nerves following joint movement. Our findings emphasize the importance of the mechanical interface between peripheral nerves and their devices on neurophysiological performance. This work has implications for nerve device design, implantation, and prediction of long-term efficacy.
Three-Dimensional Characterization and Modulation of Corneal Biomechanics via Brillouin Microscopy
(2021) Webb, Joshua Norman; Scarcelli, Giuiano; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Corneal mechanical properties are needed for diagnosing and monitoring the progression of ocular disorders such as keratoconus, screening for refractive surgeries, and evaluating treatment procedures including corneal cross-linking. Alterations of these mechanical properties are often localized to a specific area within the cornea. However, there exists a clinical gap of measuring local mechanical properties as current methods are contact-based and provide global measurements. The goal of this dissertation is to close this gap by establishing a three-dimensional, noninvasive characterization method of corneal biomechanics. Previously, our laboratory developed Brillouin microscopy as an imaging modality which can noninvasively extract mechanical measurements of a material. Here, using Brillouin microscopy, we characterized the stiffening effects of accelerated and localized cross-linking procedures with three-dimensional resolution. However, existing procedures to extract elastic modulus information from Brillouin measurements rely on empirical calibrations because a fundamental understanding between the two had not yet been established. In practice, this limits Brillouin measurements to relative softening / stiffening information, which, while useful to compare protocol efficacies, are not optimal for modeling long-term shape behavior of the cornea in clinical settings. Here, we address this shortcoming of Brillouin microscopy. First, we identified that both Brillouin-derived mechanical modulus and traditional elastic modulus are dependent on two major biophysical factors: hydration and the mechanical properties of the solid matrix. We derived and experimentally verified a quantitative relationship to describe the distinct moduli dependencies of such factors. Based on these relationships, we derived a procedure to extract the elastic modulus of the cornea from experimental measurements of Brillouin frequency shift and hydration, two clinically available parameters. Thus, the work presented here establishes a spatially resolved, noninvasive method for measuring corneal elastic modulus.
https://aero.umd.edu/graduate/graduate-student-forms
(2018) Kumar, Rubbel; Oran, Elaine S; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The increased use of explosives in military conflicts has been linked to an increase in the number of traumatic brain injuries (TBIs). Assessing the effectiveness of personal protective equipment to mitigate TBIs requires both the ability to replicate the pressure signatures caused by blast waves and an understanding of the interaction between blast waves and human bodies. Computational Fluid Dynamics (CFD) was used to understand the effect of varying different shock tube design parameters and to propose guidelines for selecting shock tube designs to accurately replicate blast wave pressure signatures representative of free-field explosive events. Additionally, a CFD model was developed to represent a shock tube built to mimic the primary overpressure magnitude and impulse loading on the human head surface as a result of free-field explosive events. This model was used to aid in the understanding of flow within the shock tube, characterize the applied pressure loading to a bare head form, augment experimental findings to fully understand the influence of headborne systems on pressure applied to the human head, and support the design of optimized laboratory test methodologies to represent a broad range of free-field blast events.
Shear Stress Response and Bond-Breaking Under Moderate Frequency Sinusoidal Translational Shear Deformation of Heterogeneous Rat Cerebrum
(2018) Gipple, Jenna; Haslach Jr., Henry W; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Blast waves, which include sinusoidal shear waves, may cause mild traumatic brain injury (mTBI) in brain tissue. The experiments model repeated insults separated by a period of rest via application of translational sinusoidal shear waves to hydrated, heterogeneous rat cerebrum at six deformation frequencies between 25 Hz and 125 Hz and displacement amplitudes of 10% or 25%. Each deformation frequency produces transient and apparent steady shear stress states that frequency analysis describes by harmonic wavelet and Fourier frequency components. Sinusoidal shear deformation waves induce bond and synapse breaking at as little as 10% displacement amplitude. Even in vitro, some bonds reform during rest. An increase in deformation frequency increases drag force between the ECF and solid matter, probably due to increased fluid acceleration and inertia. Imaging and histology do not clearly detect mild damage due to bond breaking that underlies mTBI, which the analysis of the shear stress response captures.

A. James Clark School of Engineering

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