A. James Clark School of Engineering
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Additive Manufacturing for Recapitulating Biology in vitro and Establishing Cellular & Molecular Communication(2023) Chen, Chen-Yu; Bentley, William E.; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recapitulating biological systems within laboratory devices, particularly those with analytical instrumentation, has enhanced our ability to understand biology. Especially useful are systems that provide data at the length and time scales characteristic of the assembled biological systems. In this dissertation, we have employed two advanced technologies — additive manufacturing and electrobiofabrication to create systems that both recapitulate biology and provide ready access to molecular data. First, we utilized two-photon direct laser writing (DLW) and digital light processing (DLP) 3D printing to reconstruct morphologies of human gut villi. Our constructs enable small molecule diffusion through pores and enable epithelial cell growth and differentiation, as in the gastrointestinal (GI) tract. We also developed a cell/particle alignment methodology that applies a vacuum on the underside of a device to rapidly facilitate attachment to 3D printed scaffolds. These simple demonstrations of additive manufacturing show how one can better tailor geometric features of organ-on-a-chip and other in vitro models. We then added electrobiofabrication as a means create functionalized surfaces that rapidly assemble biological components, noted for their labile nature, onto devices with just an applied voltage. In one example, we show how a thiolated polyethylene glycol (PEG) can be electroassembled as a sensor interface that includes antibody binding proteins for both titer and glycan analysis. Rapid assessment of titer and glycan structure is important for biopharmaceuticals development and manufacture. While the interface and sensing methodology was performed using standard laboratory instrumentation, we show that the methodology can be streamlined and operated in parallel by incorporating into a microfluidic sensor platform. Additionally, we show how the combination of optical and electrochemical (redox) based measurements can be combined in a simplified insert that “fits” nearly any microplate reader or other fairly standardized laboratory spectrophotometric unit. We believe that by adapting transformative electrochemical analytical methods so they can augment more traditional optical techniques, we might ultimately generate devices that provide a far more comprehensive picture of the target, promoting better investigation. Specifically, we show how three important biological and chemical systems can be interrogated using both optical measurements and electrochemistry: the oxidation state of proteins including monoclonal antibodies, redox status of hydrogel materials, and electrobiofabrication and electrogenetic induction. Lastly, we demonstrate how electrobiofabrication can be used to create designer communities of bacteria — artificial biofilms — the study of which is important for understanding phenomena from infectious disease to food contamination. That is, we discovered that by varying the applied voltage, surface area, and composition of the to-be-assembled hydrogel solution, we can precisely control the intercellular environment among bacterial populations. In sum, this dissertation integrates advances in assembly, through additive manufacturing, electrobiofabrication, with advances in electrochemical analysis to bring to the fore an electronic understanding of complex biological phenomena. We believe that the capability of translating biological information into a processible digital language opens tremendous opportunities for advancing our understanding of nature’s amazing systems, potentially enabling electronic means to control her subsystems.Item Mesenchymal Stem Cell Culture within Perfusion Bioreactors Incorporating 3D-Printed Scaffolds Enables Improved Extracellular Vesicle Yield with Preserved Bioactivity(Wiley, 2023-03-17) Kronstadt, Stephanie M.; Patel, Divya B.; Born, Louis J.; Levy, Daniel; Lerman, Max J.; Mahadik, Bhushan; McLoughlin, Shannon T.; Fasuyi, Arafat; Fowlkes, Lauren; Van Heyningen, Lauren Hoorens; Aranda, Amaya; Abadchi, Sanaz Nourmohammadi; Chang, Kai-Hua; Hsu, Angela Ting Wei; Bengali, Sameer; Harmon, John W.; Fisher, John P.; Jay, Steven M.Extracellular vesicles (EVs) are implicated as promising therapeutics and drug delivery vehicles in various diseases. However, successful clinical translation will depend on the development of scalable biomanufacturing approaches, especially due to the documented low levels of intrinsic EV-associated cargo that may necessitate repeated doses to achieve clinical benefit in certain applications. Thus, here the effects of a 3D-printed scaffold-perfusion bioreactor system are assessed on the production and bioactivity of EVs secreted from bone marrow-derived mesenchymal stem cells (MSCs), a cell type widely implicated in generating EVs with therapeutic potential. The results indicate that perfusion bioreactor culture induces an ≈40-80-fold increase (depending on measurement method) in MSC EV production compared to conventional cell culture. Additionally, MSC EVs generated using the perfusion bioreactor system significantly improve wound healing in a diabetic mouse model, with increased CD31+ staining in wound bed tissue compared to animals treated with flask cell culture-generated MSC EVs. Overall, this study establishes a promising solution to a major EV translational bottleneck, with the capacity for tunability for specific applications and general improvement alongside advancements in 3D-printing technologies.Item Pyrolysis of 3D Printed Photopolymers: Characterization and Process Development(2023) Tyler, Joshua Bixler; Cumings, John; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)3D printing has shown to be instrumental in the development of complex structures that have been previously unobtainable through traditional manufacturing processes. Photopolymers have been used in lithography-based 3D printing techniques for decades and have shown to be easily printed from the micro to macro scales. The thermal decomposition, or pyrolysis, of patterned photopolymers of microscale and mesoscale has been shown to create carbon devices such as carbon micro electromechanical systems (MEMS) and electrodes. In this dissertation, I present the characterization of pyrolyzed photopolymers 3D printed via stereolithography (SLA) and two-photon polymerization (2PP). Furthermore, processes in which to bolster the material properties of the pyrolyzed materials was examined.First, I study the effects of increasing the pyrolysis temperature on 2PP photopolymers and how this changes the electrical conductivity and microstructure of the material. From this it was shown the ability to vary the conductivity of 3D printed and pyrolyzed glassy carbon parts by up to 500X through only the temperature of pyrolysis, including reaching conductivities an order of magnitude higher than previously reported work. By extending the characterization of pyrolyzed photopolymers to SLA photopolymers I am able to further develop a generalized understanding of the electrical and microstructural properties of pyrolyzed 3D printed photopolymers. Further, demonstrate a metric in which to understand the deformation of the material during pyrolysis and perform an electrical and microstructural study of the material. Secondly, I investigate increasing the electrical and mechanical properties of pyrolyzed photopolymers through metals deposition via electroplating. In doing so I introduce a novel technique on which to electrodeposit on the surface of pyrolyzed SLA and 2PP 3D printed parts. Metallizing these pyrolyzed samples showed to increase both the electrical conductivity and ultimate strength of both pyrolyzed photopolymers. Lastly, I looked at increasing the stiffness of the pyrolyzed photopolymers through the addition of hBN filler into the precursor photopolymer. In doing so I examine the manufacturing of the composite hBN containing photopolymers for 3D printing with SLA and 2PP systems. Following 3D printing and pyrolysis of the hBN/photopolymer composite compositional and microstructural analysis is performed. Mechanical testing of the pyrolyzed composites shows that a slight increase in the stiffness of the material is observed. I have shown the ability to control the electrical conductivity and microstructure of pyrolyzed 3D printed photopolymers through pyrolysis temperature. Through the addition of metals via electroplating I demonstrate a process by which to increase the electrical conductivity and ultimate strength of pyrolyzed photopolymers and through the addition of hBN into the precursor photopolymer I have shown a way to increase the stiffness of the pyrolyzed materials. These processes have already demonstrated the ability to 3D printed electrical devices and have laid out a groundwork for future development of 3D printed electronics, energy-storage devices, and shielding.Item Additive Manufacturing of Microfluidic Technologies via In Situ Direct Laser Writing(2021) Alsharhan, Abdullah; Sochol, Ryan; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Innovations in microfluidic technologies hold great promise for a wide range of chemical, biomedical, and soft robotic applications. Unfortunately, key drawbacks associated with soft lithography-based microfabrication processes hinder such progress. To address these challenges, we advance a novel submicron-scale additive manufacturing (AM) strategy, termed “in situ direct laser writing (isDLW)”. IsDLW is an approach that benefits from the architectural versatility and length scales inherent to two-photon polymerization (2PP), while simultaneously supporting the micro-to-macro interfaces required for its effective utilization in microfluidic applications. In this dissertation, we explore isDLW strategies that enable passive and active 3D microfluidic technologies capable of enhancing “on-chip” autonomy and sophistication. Initially, we use poly(dimethylsiloxane) (PDMS)-based isDLW to fabricate microfluidic diodes that enable unidirectional rectification of fluid flow. We introduce a novel cyclic olefin polymer (COP)-based isDLW strategy to address several limitations related to structural adhesion and compatibility of PDMS microchannels. We use this COP-based approach to print microfluidic transistors comprising flexible and free-floating components that enable both “normally open” (NO) and “normally closed” (NC) functionalities—i.e., source-to-drain fluid flow (QSD) through the transistor is either permitted (NC) or obstructed (NO) when a gate input (PG) is applied. As an exemplar, we employ COP-based isDLW to print an integrated microfluidic circuit (IMC) comprised of soft microgrippers downstream of NC microfluidic transistors with distinct PG thresholds. All of these microfluidic circuit elements are printed within microchannels ≤ 40 μm in height, representing the smallest such components (to our knowledge). Theoretical and experimental results illustrate on the operational efficacy of these components as well as characterize their performance at different input conditions, while IMC experimental results demonstrate sequential actuation of the microrobotic components to realize target gripper operations with a single PG input. Furthermore, to investigate the utility of this strategy for static microfluidic technologies, we fabricate: (i) interwoven bioinspired microvessels (inner diameters < 10 μm) capable of effective isolation of distinct microfluidic flow streams, and (ii) deterministic lateral displacement (DLD) microstructures that enable continuous sorting of submicron particles (860 nm). In combination, these results suggest that the developed AM strategies offer a promising pathway for advancing state-of-the-art microfluidic technologies for various biological and soft robotic applications.Item DEVELOPMENT OF A HYBRID 3D PRINTING STRATEGY FOR NIPPLE RECONSTRUCTION(2020) Van Belleghem, Sarah Miho; Fisher, John P; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Breast cancer and its most radical treatment, the mastectomy, significantly impose both physical transformations and emotional pain in thousands of women across the globe. Although reconstructive surgery is viewed as a possible recovery route for a lost symmetry and gender identity, it provides these patients with a breast mound whose most notable feature is scarring from the initial invasive procedure. Restoring the appearance of a nipple-areola complex directly on the breast represents an important psychological healing experience for these women and remains an unresolved clinical challenge, as current restorative techniques using Skin Flap Suturing (SFS) renders a flattened disfigured skin tab within a single year and requires subsequent surgeries. A tissue-engineered scaffold designed to integrate with the breast skin can not only aid in the development of a more robust and aesthetically pleasing nipple but can also aid in minimizing the patients’ prominent mastectomy scars. As 3D printing has become a popular and advantageous way to produce scaffolds with complex, patient-specific structures, this technology holds great promise for the fabrication of custom shaped nipple-areola grafts per any breast size. The work presented here is aimed at the development of a hybrid scaffold, composed of complementary biodegradable and synthetic hydrogels, that fosters the regeneration of a viable dermal layer in the form of a nipple-areola complex. The first aim of this research defined a dynamic dual bioink 3D printing strategy to produce soft tissue grafts that allow for enhanced host integration and volume retention. A new shape analysis technique utilizing CloudCompare software was also demonstrated to expand our available toolbox for assessing scaffold aesthetic properties. We then extended both modular printing and shape assessment techniques to the fabrication of a nipple-areola scaffold in the second aim, where both structural and bioactive components of the design were further adjusted. Lastly, the third aim explored the immune and vascular responses to these hybrid materials in a rigorous evaluation of an in vivo rat subcutaneous implantation study. Envisioned as subdermal implants, these nipple-areola bioprinted scaffolds have the potential to reduce subsequent surgical intervention by creating a lasting nipple-areola structure that harmoniously coexists with the patient’s breast skin. The proposed system can be applied to current breast reconstruction practices post patient healing of silicone implantation.Item TOWARD PHANTOM DEVELOPMENT FOR MEDICAL IMAGING USING DIRECT LASER WRITING(2020) Lamont, Andrew Carl; Sochol, Ryan D.; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An important tool for the performance analysis and standardization of medical imaging technologies is the phantom, which offers specifically defined properties that mimic the structural and optical characteristics of a tissue of interest. The development of phantoms for high-resolution (i.e., micro-scale) three-dimensional (3D) imaging modalities can be challenging, however, as few manufacturing techniques can capture the architectural complexity of biological tissues at such scales. Direct Laser Writing (DLW) is an evolving additive manufacturing technique with nano-scale precision that can fabricate micro and nanostructures with unparalleled geometric complexity. This dissertation outlines the unique microfluidic-based DLW strategies that have been developed for novel micro-scale phantom production. First, I will outline the development and characterization of an in situ DLW strategy used to adhere printed components to the surfaces of a microchannel. I will then explain how we have leveraged this strategy for a proof-of-concept retinal cone outer segment phantom that is laden with light-scattering Titanium (IV) Dioxide nanoparticles. This phantom has valuable implications for the performance analysis of the emerging ophthalmological modality, adaptive optics-optical coherence tomography (AO-OCT). Next, I will describe the development and characterization of a microfluidic-based multi-material DLW strategy to fabricate single components from multiple materials with minimal registration error between the materials. Ultimately, we intend to use this method to develop multi-material platforms and phantoms, including high-aspect-ratio multi-material retinal cone phantoms for AO-OCT. Finally, to demonstrate the applicability of this method for applications beyond AO-OCT, I present a preliminary phantom production strategy for the light microscopy-based modality, whole slide imaging (WSI). Specifically, we assess the DLW and light microscopy performance of dyed photoresists and offer a preliminary multi-material demonstration, which are pivotal first steps toward the creation of a first-generation multi-material WSI phantom. This work provides valuable insights and strategies that leverage microfluidic-based DLW techniques to fabricate novel micro-scale phantoms. It is anticipated that these strategies will have a lasting impact, not only on the production of phantoms for medical imaging modalities, but also for the fabrication of advanced microfluidic and multi-material microstructures for fields such as meta-materials, micro-optics, lab-on-a-chip, and organ-on-a-chip.Item Dual-Chambered Membrane Bioreactor for the Dynamic Co-Culture of Dermal Stratified Tissues(2019) Navarro Rueda, Javier; Fisher, John P; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Every year over 11 million patients suffer severe burns worldwide. Facial burn statistics include victims of violence (warfare, acid attacks, scalding) and trauma (flame, electrical, chemical). Skin is the first barrier against external mechanical and biochemical factors, such as burning agents, and is composed of the epidermis, dermis, and hypodermis layers. When burned, skin cannot regulate temperature or fluid transport, or stop bacterial infection. Due to the importance of the skin barrier, natural healing and grafting treatments aim to quickly close the wounds with fast proliferation of fibroblasts and collagen deposition, a process that results in scarring, loss of function, and disfigurement. Tissue engineering has produced epidermis-dermis skin scaffolds for clinical use and in vitro dermal models. Throughout this work we studied 3D printing and bioreactor strategies for the simultaneous physiologic and topographic reconstruction of burnt facial skin tissues. First, we formulated a keratin-based bioink that can be used for 3D printing on a lithography-based 3D printer. Second, we implemented the keratin bioink in the production of Halofuginone-laden face masks for the improvement of contracture, scarring, and aesthetics in severe skin wound healing in an animal model. Due to lack of collagen organization and microstructural development, we introduced a novel dual-chambered (DCB) bioreactor system to study stratified tissues. For this, crosslinking density of the keratin-based hydrogels was used to fine tune the transport properties of membranes for potential use in guided tissue regeneration applications. Then, we assessed the viability of our novel DCB for co-culturing adjacent cell populations with the inclusion of a regulatory keratin membrane. Last, having studied the DCB with flat interfaces, we assessed its viability for perfusing curved interfaces. The integration of both curvature and cell populations allowed to assess the synergistic development of adjacent dermis fibroblasts and hypodermis stem-cell-derived adipocytes and evaluate whether including topography parameters would alter cell viability in the DCB. The strategies developed here elucidate on tissue stratification and aesthetic reconstruction. Furthermore, the keratin-based bioink, the engineered membranes, and the DCBs can be extended to study other stratified or gradient tissues and to fine-tune communication between cell populations in complex 3D constructs.Item DEVELOPMENT OF AN ENDOTHELIAL CELL/MESENCHYMAL STEM CELL COCULTURE STRATEGY FOR THE VASCULARIZATION OF ENGINEERED BONE TISSUE.(2019) Piard, Charlotte Marianne; Fisher, John P; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the past two decades, remarkable progress has been made in the development of surgical techniques for bone reconstruction, significantly improving clinical outcomes. However, major reconstruction after trauma or cancer is still limited by the paucity of autologous material and donor site morbidity. Recent advances in the field of tissue engineering have generated new approaches for restoring bone defects. In spite of this progress, the necessity of suitable blood supply to ensure cell function is a major challenge in the development of more complex and functional grafts. Many investigators have successfully demonstrated the use of different strategies including growth factor delivery and in vitro coculture of ECs and MSCs to develop vascular structures. MSCs have the ability to secrete a wide range of bioactive cytokines and growth factors that can influence nearby cells via paracrine signaling. This crosstalk between ECs and MSCs is mutually beneficial, as ECs enhance osteogenic differentiation of hMSCs through direct cell-cell contact and paracrine signaling. In the native environment of cortical bone, both cell populations, osteogenic and vasculogenic, follow a unique well-defined pattern, called osteons. The goal of this proposed study was to develop a novel bio-inspired and vascularized bone construct, harvesting the synergistic effects of pro-angiogenic growth factor delivery and coculture of ECs and MSCs. To address this goal, we first developed mesoporous calcium deficient hydroxyapatite apatite microparticles, with biological properties closer to bone than commercially available hydroxyapatite, and capable of efficiently loading and sustainably releasing pro-angiogenic growth factors. We then demonstrated the successful fabrication of a novel bio-inspired 3DP fibrin-PCL composite scaffold, with mechanical strength comparable to bone. The utilization of these scaffolds in constructing osteons for bone regeneration demonstrated the promising capacity of the construct to improve neovascularization. In light of these results, we hypothesized that cell placement or patterning could play a critical role in neovascularization. Which lead us to investigate the role of distance between cell populations, introduced via 3D printing, in ECs/MSCs crosstalk. Our results suggested that controlling the distance between ECs and MSCs in coculture, using 3D printing, could influence angiogenesis.Item DESIGN AND PERFORMANCE CHARACTERIZATION OF AN ADDITIVELY-MANUFACTURED HEAT EXCHANGER FOR HIGH TEMPERATURE APPLICATIONS(2018) Zhang, Xiang; Ohadi, Michael; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In its early stages of development, additive manufacturing was used chiefly for prototyping, but over the last decade, its use has evolved to include mass production of certain products for numerous industries in general, and speciality industries such as biomedical and aerospace industries in particular. Additive manufacturing can be used to fabricate unconventional/complex designs that are difficult and time-consuming through conventional fabrication methods, but offer significant performance advantage over state of the art. One such example is high temperature heat exchangers with complex novel geometries that can help improve the heat transfer density and provide better flow distribution, resulting in more compact and efficient designs and thereby also reducing materials costs considering fabrication of these heat exchangers from the suitable super alloys with the conventional manufacturing techniques is very difficult and laborious. This dissertation presents the results of the first high-temperature gas-to-gas manifold-microchannel heat exchanger successfully fabricated using additive manufacturing. Although the application selected for this dissertation focuses on an aerospace pre-cooling heat exchanger application, the results of this study can still directly and indirectly benefit other industrial sectors as heat exchangers are key components of most power conversion systems. In this work, optimization and numerical modelling were performed to obtain the optimal design, which show 30% weight reduction compared to the design baseline. Thereafter, the heat exchanger was scaled down to 66 × 74 × 27 mm3 and fabricated as a single piece using direct metal laser sintering (DMLS). A minimum microchannel fin thickness of 165 μm was achieved. Next, the additively manufactured headers were welded to the heat exchanger core and the conventionally manufactured flanges. A high-temperature experimental loop was next built, and the additively manufactured heat exchanger was successfully tested at 600°C with ~ 450 kPa inlet pressure. A maximum heat duty of 2.78 kW and a heat transfer density close to 10 kW/kg were achieved with cold-side inlet temperature of 38°C during the experiments. A good agreement between the experimental and numerical results demonstrates the validity of the numerical models used for heat transfer and pressure drop predictions of the additively manufactured heat exchanger. Compared to conventional plate-fin heat exchangers, up to 25% improvement in heat transfer density was achieved. This work shows that additive manufacturing can be used to fabricate compact and lightweight high temperature heat exchangers, which benefit applications where space and weight are constrained.Item RECENT DEVELOPMENTS IN HIGH TEMPERATURE HEAT EXCHANGERS: A REVIEW(Global Digital Central, 2018) Zhang, Xiang; Keramati, Hadi; Arie, Martinus; Singer, Farah; Tiwari, Ratnesh; Shooshtari, Amir; Ohadi, MichaelHeat exchangers are key components of most power conversion systems, a few industrial sectors can particularly benefit from high temperature heat exchangers. Examples include conventional aerospace applications, advanced nuclear power generation systems, and high efficiency stationary and mobile modular fossil fuel to shaft power/electricity conversion systems. This paper provides a review of high temperature heat exchangers in terms of build materials, general design, manufacturing techniques, and operating parameters for the selected applications. Challenges associated with conventional and advanced fabrication technologies of high temperature heat exchangers are discussed. Finally, the paper outlines future research needs of high temperature heat exchangers.