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 Capsule Migration and Deformation in a Converging Micro-Capillary(MDPI, 2021-03-03) Wang, Yiyang; Dimitrakopoulos, PanagiotisThe lateral migration of elastic capsules towards a microchannel centerline plays a major role in industrial and physiological processes. Via our computational investigation, we show that a constriction connecting two straight microchannels facilitates the lateral capsule migration considerably, which is relatively slow in straight channels. Our work reveals that the significant cross-streamline migration inside the constriction is dominated by the strong hydrodynamic forces due to the capsule size. However, in the downstream straight channel, the increased interfacial deformation at higher capillary numbers or a lower viscosity ratio and lower membrane hardness results in increased lateral cross-streamline migration. Thus, our work highlights the different migration mechanisms occurring over curved and straight streamlines.Item In Vitro Models of Blood and Lymphatic Vessels—Connecting Tissues and Immunity(Wiley, 2022-06-25) Bogseth, Amanda; Ramirez, Ann; Vaughan, Erik; Maisel, KatharinaBlood and lymphatic vessels are regulators of physiological processes, including oxygenation and fluid transport. Both vessels are ubiquitous throughout the body and are critical for sustaining tissue homeostasis. The complexity of each vessel’s processes has limited the understanding of exactly how the vessels maintain their functions. Both vessels have been shown to be involved in the pathogenesis of many diseases, including cancer metastasis, and it is crucial to probe further specific mechanisms involved. In vitro models are developed to better understand blood and lymphatic physiological functions and their mechanisms. In this review, blood and lymphatic in vitro model systems, including 2D and 3D designs made using Transwells, microfluidic devices, organoid cultures, and various other methods, are described. Models studying endothelial cell-extracellular matrix interactions, endothelial barrier properties, transendothelial transport and cell migration, lymph/angiogenesis, vascular inflammation, and endothelial-cancer cell interactions are particularly focused. While the field has made significant progress in modeling and understanding lymphatic and blood vasculature, more models that include coculture of multiple cell types, complex extracellular matrix, and 3D morphologies, particularly for models mimicking disease states, will help further the understanding of the role of blood and lymphatic vasculature in health and disease.Item Bioinspired One Cell Culture Isolates Highly Tumorigenic and Metastatic Cancer Stem Cells Capable of Multilineage Differentiation(Wiley, 2020-04-28) Wang, Hai; Agarwal, Pranay; Jiang, Bin; Stewart, Samantha; Liu, Xuanyou; Liang, Yutong; Hancioglu, Baris; Webb, Amy; Fisher, John P.; Liu, Zhenguo; Lu, Xiongbin; Tkaczuk, Katherine H. R.; He, XiaomingCancer stem cells (CSCs) are rare cancer cells that are postulated to be responsible for cancer relapse and metastasis. However, CSCs are difficult to isolate and poorly understood. Here, a bioinspired approach for label-free isolation and culture of CSCs, by microencapsulating one cancer cell in the nanoliter-scale hydrogel core of each prehatching embryo-like core–shell microcapsule, is reported. Only a small percentage of the individually microencapsulated cancer cells can proliferate into a cell colony. Gene and protein expression analyses indicate high stemness of the cells in the colonies. Importantly, the colony cells are capable of cross-tissue multilineage (e.g., endothelial, cardiac, neural, and osteogenic) differentiation, which is not observed for “CSCs” isolated using other contemporary approaches. Further studies demonstrate the colony cells are highly tumorigenic, metastatic, and drug resistant. These data show the colony cells obtained with the bioinspired one-cell-culture approach are truly CSCs. Significantly, multiple pathways are identified to upregulate in the CSCs and enrichment of genes related to the pathways is correlated with significantly decreased survival of breast cancer patients. Collectively, this study may provide a valuable method for isolating and culturing CSCs, to facilitate the understanding of cancer biology and etiology and the development of effective CSC-targeted cancer therapies.Item Lab-on-a-Chip Integration of Size-based Separation Techniques for Isolation of Bacteria from Blood(2018) Han, Jung Yeon; DeVoe, Don L; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Clinical sample preparation is an essential process in modern diagnostics for maximizing sensitivity and specificity of detection and for ensuring reliability of assay readout. In general, sample preparation typically involves isolating and concentrating a population of target molecules, cells, or particles together with the removal of undesired components from specimen that could otherwise interfere with target detection. The identification of bacteria from complex clinical matrices such as blood presents a particular sample preparation challenge. Conventional culture-based methods typically require at least 24 h of incubation time, making this approach unsuitable for use in rapid diagnostics. Therefore, the development of sample preparation methods for bacteria with rapid processing time, high purification efficiency, and large volumetric throughput to enable analysis of low bacteria concentrations in blood remains a key challenge. This dissertation is focused on realizing a universal platform for preparing microbial sample from blood that is free lysis buffer, electric field, or affinity-based capture methods. First, we developed the porous silica monolith elements integrated into thermoplastic devices for isolation of intact bacteria from blood, enabling the application of emerging detection methods that supports bacterial identification from purified cell populations. Second, to support high throughput analysis of blood samples procured in resource-limited environments, microfluidics elements integrated directly into a syringe are demonstrated by utilizing the deterministic lateral displacement technique and the Dean flow focusing methods. Through these approaches blood cell reduction prior to bacteria isolation can be achieved, thereby increasing the overall sample volume that may be processed by the system. Additionally, a miniaturized hydrocylone capable of operating at tens of milliliters per minute feed rate is presented. Complex microstructures successfully realized at a hundred-micron scale by 3D printing technique presented a promising route to the unconventional microfluidic systems. Lastly, we demonstrated ancillary microfluidic components required to enable full operation of the system in a low-cost lab-on-a-chip format suitable for implementation in resource-limited environments and optimize overall operation of the platform to achieve throughput, sensitivity, and selectivity suitable for clinical application when coupling the platform with downstream detection methods designed for assay readout from intact bacteria.Item DYNAMICS OF CAPSULES IN COMPLEX MICROFLUIDIC DEVICES(2018) Koolivand, Abdollah; Dimitrakopoulos, Panagiotis; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The dynamics of micro-capsules has attracted a lot of attention in the last decade due to their vast applications in different industrial sectors such as cosmetic products, food industry, chemical processes, reaction systems, cell modeling, drug delivery, and medical processes. Additionally, biological cells such as red blood cells can be modeled as capsules. Understanding the rheological behavior of these cells provides great physical insight for early diagnosis of relevant diseases. The main objective of this research is to investigate the effects of physical and geometrical parameters on the hydrodynamics of simple and multiple capsules in complex mi- crofluidic devices. For this purpose, we have developed the mathematical formulation needed for modeling multiple capsules with or without complex internal structures. The developed framework provides an enormous flexibility in problem definition, and facilitates the investigation of the hydrodynamics of a wide class of capsules in microfluidic channels and vascular capillaries. We first study the deformation of a spherical capsule in a T-junction channel. It is shown that an initially spherical capsule develops a bean shape at low flow rates and an inverse kayak shape at high flow rates. Based on the non-trivial deformation of the capsule, a new methodology for the determination of membrane moduli is proposed. For an accurate determination of the membrane moduli, it is paramount to measure the capsule dimensions precisely, which is easier in the proposed device owning to the stagnation-point flow of the T-junction. To determine the membrane moduli, one needs to do a single experiment for different flow rates, and compare the experimental measurements of the capsule steady-state dimensions with the provided computational data. We then consider the flow dynamics of non-spherical capsules and investi- gate the effects spheroidity and initial orientation on the steady-state shape. It is found that a non-spherical capsule, placed with a non-zero initial orientation angle along the centerline of a microchannel, does not practically rotate during deforma- tion. Thus, precise instrumentation is required for proper alignment of the capsule which influences the deformation and steady-state shape. This behavior may explain possible inconsistencies between measured (experimental) and calculated (compu- tational) shapes. We then study the lateral migration of capsules with different size in a mi- crofluidic channel with a trapezoidal cross-section. Owing to the emergence of 3D printing technology, fabrication of a channel with trapezoidal cross-section is fea- sible. Based on our computational data, we proposed an optimized geometry that could be utilized for separation of capsules or cells with different size. The main advantage of the proposed geometry is its inexpensive fabrication cost without the need for incorporating complicated inner structures, which automatically eliminates the risk of channel clogging. Moreover, the simple structure of the trapezoidal mi- crochannel allows an easy scale out through parallelization and reduction of the cell sorting time. In addition, we investigate the complex behavior of two (equal or unequal sized) capsules flowing in a square microfluidic channel. Capsules merging process controls the on-demand drug release and reaction. Thus, we identified the hydro- dynamic conditions that facilitates or hinders the merging of the capsules. The merging process is commonly accompanied by the drainage of existing liquid film between two particles. We observed that the capsules merging in most cases is ac- companied by the formation of dimple surfaces, and thus a simplified flat lubrication surface assumption which is widely-used in the theoretical studies might not be an ideal choice for modeling the film drainage time in merging process.Item THERMOPLASTIC MICROFLUIDIC PCR TECHNOLOGIES FOR NEAR-PATIENT DIAGNOSTICS(2017) Sposito, Alex J.; DeVoe, Don L; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Microfluidic technologies have great potential to help create portable, scalable, and cost-effective devices for rapid polymerase chain reaction (PCR) diagnostics in near patient settings. Unfortunately, current PCR diagnostics have not reached ubiquitous use in such settings because of instrumentation requirements, operational complexity, and high cost. This dissertation demonstrates a novel platform that can provide reduced assay time, simple workflow, scalability, and integration in order to better meet these challenges. First, a disposable microfluidic chip with integrated Au thin film heating and sensing elements is described herein. The system employs capillary pumping for automated loading of sample into the reaction chamber, combined with an integrated hydrophilic valve for precise self-metering of sample volumes into the device. With extensive multiphysics modeling and empirical testing we were able to optimize the system and achieve cycle times of 14 seconds and completed 35 PCR cycles plus HRMA in a total of 15 minutes, for successful identification of a mutation in the G6PC gene indicative of von Gierke’s disease. Next, a scalable sample digitization method that exploits the controlled pinning of fluid at geometric discontinuities within an array of staggered microfluidic traps is described. A simple geometric model is developed to predict the impact of device geometry on sample filling and discretization, and validated experimentally using fabricated cyclic olefin polymer devices. Finally, a 768-element staggered trap array is demonstrated, with highly reliable passive loading and discretization achieved within 5 min. Finally, a technique for reagent integration by pin spotting affords simplified workflow, and the ability to perform multiplexed PCR. Reagent printing formulations were optimized for stability and volume consistency during spotting. Paraffin wax was demonstrated as a protective layer to prevent rehydration and reagent cross contamination during sample loading. Deposition was accomplished by a custom pin spotting tool. A staggered trap array device with integrated reagents successfully amplified and validated a 2-plex assay, showing the potential of the platform for a multiplexed antibiotic resistance screening panel.Item Lipid tethering of breast tumor cells enables real-time imaging of free-floating cell dynamics and drug response(Impact Journals, 2016-02-08) Chakrabarti, Kristi R.; Andorko, James I.; Whipple, Rebecca A.; Zhang, Peipei; Sooklal, Elisabeth L.; Martin, Stuart S.; Jewell, Christopher M.Free-floating tumor cells located in the blood of cancer patients, known as circulating tumor cells (CTCs), have become key targets for studying metastasis. However, effective strategies to study the free-floating behavior of tumor cells in vitro have been a major barrier limiting the understanding of the functional properties of CTCs. Upon extracellular-matrix (ECM) detachment, breast tumor cells form tubulin-based protrusions known as microtentacles (McTNs) that play a role in the aggregation and re-attachment of tumor cells to increase their metastatic efficiency. In this study, we have designed a strategy to spatially immobilize ECM-detached tumor cells while maintaining their free-floating character. We use polyelectrolyte multilayers deposited on microfluidic substrates to prevent tumor cell adhesion and the addition of lipid moieties to tether tumor cells to these surfaces through interactions with the cell membranes. This coating remains optically clear, allowing capture of high-resolution images and videos of McTNs on viable free-floating cells. In addition, we show that tethering allows for the real-time analysis of McTN dynamics on individual tumor cells and in response to tubulin-targeting drugs. The ability to image detached tumor cells can vastly enhance our understanding of CTCs under conditions that better recapitulate the microenvironments they encounter during metastasis.Item Integration of virus-like particle macromolecular bioreceptors in electrochemical biosensors(2016) Zang, Faheng; Ghodssi, Reza; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Rapid, sensitive and selective detection of chemical hazards and biological pathogens has shown growing importance in the fields of homeland security, public safety and personal health. In the past two decades, efforts have been focusing on performing point-of-care chemical and biological detections using miniaturized biosensors. These sensors convert target molecule binding events into measurable electrical signals for quantifying target molecule concentration. However, the low receptor density and the use of complex surface chemistry in receptors immobilization on transducers are common bottlenecks in the current biosensor development, adding to the cost, complexity and time. This dissertation presents the development of selective macromolecular Tobacco mosaic virus-like particle (TMV VLP) biosensing receptor, and the microsystem integration of VLPs in microfabricated electrochemical biosensors for rapid and performance-enhanced chemical and biological sensing. Two constructs of VLPs carrying different receptor peptides targeting at 2,4,6-trinitrotoluene (TNT) explosive or anti-FLAG antibody are successfully bioengineered. The VLP-based TNT electrochemical sensor utilizes unique diffusion modulation method enabled by biological binding between target TNT and receptor VLP. The method avoids the influence from any interfering species and environmental background signals, making it extremely suitable for directly quantifying the TNT level in a sample. It is also a rapid method that does not need any sensor surface functionalization process. For antibody sensing, the VLPs carrying both antibody binding peptides and cysteine residues are assembled onto the gold electrodes of an impedance microsensor. With two-phase immunoassays, the VLP-based impedance sensor is able to quantify antibody concentrations down to 9.1 ng/mL. A capillary microfluidics and impedance sensor integrated microsystem is developed to further accelerate the process of VLP assembly on sensors and improve the sensitivity. Open channel capillary micropumps and stop-valves facilitate localized and evaporation-assisted VLP assembly on sensor electrodes within 6 minutes. The VLP-functionalized impedance sensor is capable of label-free sensing of antibodies with the detection limit of 8.8 ng/mL within 5 minutes after sensor functionalization, demonstrating great potential of VLP-based sensors for rapid and on-demand chemical and biological sensing.Item Image-Guided Precision Manipulation of Cells and Nanoparticles in Microfluidics(2016) Cummins, Zachary; Shapiro, Benjamin; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Manipulation of single cells and particles is important to biology and nanotechnology. Our electrokinetic (EK) tweezers manipulate objects in simple microfluidic devices using gentle fluid and electric forces under vision-based feedback control. In this dissertation, I detail a user-friendly implementation of EK tweezers that allows users to select, position, and assemble cells and nanoparticles. This EK system was used to measure attachment forces between living breast cancer cells, trap single quantum dots with 45 nm accuracy, build nanophotonic circuits, and scan optical properties of nanowires. With a novel multi-layer microfluidic device, EK was also used to guide single microspheres along complex 3D trajectories. The schemes, software, and methods developed here can be used in many settings to precisely manipulate most visible objects, assemble objects into useful structures, and improve the function of lab-on-a-chip microfluidic systems.Item INTERFACIAL CONSIDERATIONS FOR DROPLET PCR LAB-ON-CHIP DEVICES(2015) Pandit, Kunal; White, Ian M; Raghavan, Srinivasa R; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Lab-on-chip devices have the potential to decentralize the current model of diagnostics to point-of-care diagnostics. Easy to use, low cost, rapid infectious disease diagnostic tools could especially impact and improve healthcare in low resource areas. Micro-total-analytical-systems could also enable smarter medical decisions, quicker patient recoveries, and cheaper healthcare costs in fully developed settings. Significant innovations to standard technologies used today will help realize the promise of lab-on-chip devices. In this work, innovative technologies compatible with current lab-on-chip devices were investigated to simplify their operation, decrease their complexity, and reduce their cost. The interfacial aspects that dominate microfluidic systems, and in particular droplet polymerase chain reaction (PCR) devices, are emphasized. Droplet PCR utilizing microfluidic technology has largely been automated, but sample preparation methods prior to amplification remains a laborious process. We have developed particles that condense the many steps of sample preparation into a single buffer protocol. The particles were made by crosslinking chitosan, a pH responsive biopolymer. DNA was electrostatically and sterically adsorbed to the beads at pH 8.5. Furthermore, amplification of DNA directly off the beads was demonstrated eliminating the need to desorb DNA into solution. Implementation of these particles will drastically simplify droplet PCR lab-on-chip devices. We also characterized the adsorption of polymerase at the oil-water interfaces of droplets and identified a surfactant to prevent the loss of polymerase in solution. The pendant drop technique was used to observe the change in interfacial tension due to adsorption of Taq Pol and/or surfactants to the interface. PCR performance of two surfactants, Brij L4 and ABIL EM90, were predicted from equilibrium interfacial tension measurements. Brij L4, a surfactant that had never been used with PCR, prevented polymerase adsorption and enabled more efficient PCR than ABIL EM90, a popular PCR surfactant. Lastly, we ambitiously designed a system to conduct droplet PCR without oil or surfactants. Droplets were generated on-chip by adapting a co-flow droplet generating device previously developed in our group. Then droplets were immobilized on-chip in hydrodynamic traps. Two different modes of trapping were demonstrated, indirect and direct. Also, all aspects of an air continuous phase droplet PCR device were considered such as protein adsorption to channel walls and droplet evaporation during thermal cycling.