Mohamad Orabi
Research
My research focuses on designing, modeling, and fabricating Tesla Turbines and microfluidic devices (medical devices) following the Fused Deposition Modeling (FDM) and Soft-Lithography (SL) 3D printing techniques. These devices are used for studying the biomechanics-mechanobiology interface on stem cell differentiation under diabetic and hypoxic conditions in embedded systems.
An optimization algorithm using MATLAB to predict and optimize microfluidics' material properties and geometric parameters of microfluidics is conducted, employing a model-free episodic controller (MFEC) algorithm to study the underlying physical phenomena within the devices. This involved incorporating mass and energy balance equations to characterize fluid flow and considering material properties such as viscosity and surface tension. We are working on a Multiphysics COMSOL model to optimize different parameters of microfluidic devices such as shear stress, slip length, and boundary layers of microchannels, and study their impact on the behavior of microencapsulated cells. We are employing COMSOL as well to optimize the design of serpentine channels for generating GelMA droplets, considering fluid dynamics, interfacial tension, and channel geometry. We are generating and characterizing hydrogel droplets using Alginate, Gelatin, and GelMA and adjusting their physical, mechanical, and chemical properties to regulate cells' function and differentiation processes in microfluidics. Different microscopy imaging methodologies are applied including image segmentation and image acquisition and processing, across various microscopy modalities such as light microscopy, electron microscopy, confocal microscopy, and fluorescence microscopy.
Unraveling the Biomechanics-Mechanobiology Interface: Stem Cell Differentiation in Microfluidics for Diabetic and Hypoxic Applications
Ph.D. Dissertation
Tradeoffs in ATP metabolisms via hypoxic gradient migration assays
Oxygen gradient simulaion with spatiotemporal detection
Migration and scratch assays are helpful tools to investigate wound healing and tissue regeneration processes, especially under disease conditions such as diabetes. However, traditional migration (injury-free) assays and scratch (with injury) assays are limited in their control over cellular environments and provide only simplified read-outs of their results. On the other hand, microfluidic-based cell assays offer a distinct advantage in their integration and scalability for multiple modalities and concentrations in a single device. Additionally, in situ stimulation and detection helps to avoid variabilities between individual bioassays. To realize an enhanced, smarter migration assay, we leveraged our multilayered oxygen gradient (1-16%) to study HaCaT migrations in diabetic conditions with spatial and metabolic read-outs. An analysis of the spatial migration over time observed a new dynamic between hypoxia (at 4.16-9.14% O2) and hyperglycemia. Furthermore, in situ adenosine triphosphate (ATP) and reactive oxygen species (ROS) responses suggest that this dynamic represents a switch between stationary versus motile modes of metabolism. Thus, elevated glucose and hypoxia are synergistic triggers of this switch under disease conditions. These findings illustrate the benefits of spatial microfluidics for modeling complex diseases such as hypoxia and diabetes, where multimodal measurements provide a more deterministic view of the underlying processes.
Highlights:
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Scratch assays (with injury) had faster migration than stamping (without injury), but it was less consistent across the entire wound area
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Glucose levels significantly impaired cell migration and ATP balance, suggesting a shift from migration to metabolic activities
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A range of hypoxic concentrations between 4.16-9.14% promoted the migration of HaCaT cells, suggesting that hypoxia is required for proper wound healing
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With an actual injury, sodium pyruvate and oligomycin elevated the cytoplasmic ATP levels and rescued the migration of HaCaT cells, especially with gradient oxygen conditions
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The manuscript is still under review, Biofabrication Journal
Oxygen gradient stimulaion with ATP fluoresccence detection for scratch assay
Reducing shear stress in islet beta cells via textured microtesla pump
Islet beta cells play a critical role in glucose homeostasis, and their dysfunction is a hallmark of diabetes mellitus. One inherent factor affecting the viability and functionality of beta cells in cell culture is the shear stress induced by media flow. In this study, we modified a boundary layer based microTesla pump to deliver precise and controlled fluid flow around beta cells to enable in vitro studies of shear stimulations. We varied the surface texture, rotational speed, and fluid viscosities in order to study how the surface slip length is changed and the resultant pump output. Using this new pump, we demonstrated how optimized flow reduces the transient artifacts in beta cells glucose stimulation compared to traditional syringe pumps. These outcomes not only contribute to a deeper understanding of the mechanics of boundary layer pumps and their surface optimizations but also underscore their significance in preventing misleading results in flow-dependent microphysiological experiments.
COMSOL simulation for the maximum valocity and shear stress on the surface of our µTesla pump
Highlights:
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Islet beta cells crucial for glucose homeostasis; dysfunction is hallmark of diabetes mellitus
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Shear stress induced by media flow impacts viability and functionality of beta cells in culture
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MicroTesla pump modified for precise fluid flow around beta cells for shear stimulation studies
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Surface texture, rotational speed, and fluid viscosities varied to understand changes in surface slip length and pump output
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New pump reduces transient artifacts in beta cell glucose stimulation compared to traditional syringe pumps
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Findings contribute to understanding boundary layer pump mechanics and surface optimizations
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Significance in preventing misleading results in flow-dependent microphysiological experiments
The manuscript is still under review, Small Journal
Testing the surface texturization of µTesla-II pump
Adipocyte-Ins1 Crosstalk: Harnessing microtesla 2 pump for glucose and insulin modulation in diabetes
The fabrication process followed for making the microfluidic device with 2 µTesla pumps
Hyperglycemia and hyperinsulinemia are pivotal features of diabetes, significantly influencing its pathophysiology. Effectively managing these conditions is critical for diabetes control and reducing the risk of complications. However, traditional cell cultures in well plates have limitations in controlling cellular environments and provide simplified read-outs of monoculture results. On the other hand, microfluidic-based cell assays present distinct advantages with integrated, scalable capabilities across multiple modalities, enabling bi-directional study modulations in a single device. Additionally, in situ stimulation and detection help minimize variabilities and achieve higher accuracy. To enhance co-culture assays intelligently, we utilized our microfluidic device equipped with two microtesla pumps for facilitating flow over 2D cultured cells bi-directionally. The study investigated the influence of adipocyte inflammatory cytokines on INS1 cells and the effects of INS1 cells’ insulin and adiponectin secretion on adipocytes. Analysis of insulin and glucose modulations over time revealed a dynamic interplay between adipocytes and INS1 cells. Furthermore, in situ studies uncovered the direct impact of adipocyte-secreted TNF-α on adiponectin secretion from monocultured adipocytes. However, in co-culture with INS1 cells, IL-6 secreted from adipocytes leveraged insulin secretion from INS1 cells, counteracting the role of TNF-α from adipocytes and enhancing adiponectin secretion. These findings highlight the advantages of embedded systems in microfluidics for modeling diseases like diabetes, where multimodal measurements offer a more deterministic view of underlying processes.
Highlights:
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Hyperglycemia and hyperinsulinemia are key features of diabetes, influencing its pathophysiology
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Effective management critical for diabetes control and reducing complications
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Traditional cell cultures in well plates have limitations in controlling cellular environments and provide simplified read-outs
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Microfluidic-based cell assays offer advantages with integrated, scalable capabilities across multiple modalities
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Bi-directional study modulations possible in a single device, minimizing variabilities and achieving higher accuracy
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Utilization of microfluidic device with two microtesla pumps for bi-directional flow over 2D cultured cells
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Study investigates influence of adipocyte inflammatory cytokines on INS1 cells and effects of INS1 cells’ insulin and adiponectin secretion on adipocytes
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Dynamic interplay observed between adipocytes and INS1 cells in insulin and glucose modulations over time
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In situ studies reveal direct impact of adipocyte-secreted TNF-α on adiponectin secretion from monocultured adipocytes
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In co-culture with INS1 cells, IL-6 secreted from adipocytes leverages insulin secretion from INS1 cells, counteracting TNF-α and enhancing adiponectin secretion
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Highlights advantages of embedded systems in microfluidics for modeling diseases like diabetes, offering deterministic view of underlying processes
The manuscript is still under review, Lab on Chip
Morphological and metabolic enhancements of co-cultures under shear conditions
Biosystems Engineering:
Direct evaporative cooler apparatus (DEC)
Dew point Indirect evaporative cooler apparatus (DPIEC)
Illustration of the poultry house design conditioned by the DEC/DPIEC units
Highlights:
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Developed thermal model to compare the performance of three passive cooling systems in meeting thermal and indoor air quality requirements
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Adopted a modular analysis where the mathematical models were developed for the evaporative coolers and the tunnel-ventilated
poultry house module -
Developed a computational fluid dynamics model for simulations of the compartment conditioned by the localized system using ANSYS-Fluent
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Fabricated experimental setup to validate the model
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Journal Publication: ​A sustainable localized air distribution system for enhancing thermal environment and indoor air quality of poultry house for semiarid region.
Maintaining bird health is of critical importance for a sustainable production quality. Their welfare greatly depends on the thermal environment and indoor air quality (IAQ). Typical recommended temperatures and relative humidity (RH) fall in the range of 20-24 °C and 50-70% respectively. IAQ is mainly dependent on diluting carbon dioxide from the hens' breathing and ammonia emitted from their litter to limit concentrations to safety standards of 2500 ppm and 25 ppm respectively. Hot and high humidity conditions in poultry houses, as well as high concentrations of gaseous contaminants, can be detrimental to birds' and workers’ wellbeing and to production quality. Consequently, sustainable ventilation designs that are able to meet both cooling and IAQ requirements in poultry houses are needed. The aim of this work is to compare the water and energy consumption of DEC and DPIEC under conventional air distribution system in a poultry house located in the semi-arid Beqaa region of East Lebanon. The performance of the DPIEC with the conventional system are also compared to that with the localised air distribution. The effectiveness of the combined systems is assessed in terms of their ability to meet cooling and IAQ requirements.
Illustration of the velocity and temperature contours at x = 0.6 m, 1.5 m, 2.7 m planes for the highest flow rates.
Energy Systems:
Meeting hygrothermal and air quality requirements in livestock dwellings is crucial for upholding production quality standards. However, ventilation and air-conditioning in such enclosures is very energy-intensive, especially amidst climate change and intensifying summer conditions. This is due to large surface areas, livestock densities, and contaminants' generation rates. Hence, striving for more efficient passive cooling techniques is always a desired goal to reduce the anthropogenic emissions of the agricultural sector without compromising production quality. In this study, the energy savings' potential of two passive systems in a poultry house located in the semiarid climate of Beqaa Valley, Lebanon, was compared. The first system is the conventional stand-alone direct evaporative cooler (DEC), which evaporatively cools the outdoor clean air to temperatures close to its wet bulb. The second system combines with the DEC, an earth-to-air heat exchanger (EAHE) that sensibly precools the ambient air and reduces its wet-bulb temperature. This can increase the cooling capacity of the DEC, which can save substantial amounts of energy while achieving similar, if not better, indoor conditions.
The load variation (kW) on an hourly basis for May, June, July, and August.
Schematic of the DEC and EAHE units integrated with a tunnel air distribution system.
Highlights:
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Developed simplified mathematical models for the DEC, EAHE, and the poultry house space, assuming a well-mixed air volume
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After sizing the systems, simulation results showed that the stand-alone DEC system was not able to meet relative humidity requirements at all times unlike the proposed hybrid EAHE/DEC system
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The hybrid EAHE/DEC system resulted in 40% reduction in air and water consumption rates compared with the DEC system during the summer season
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Journal Publication: Modeling and optimization of poultry house passive cooling strategies in semiarid climates.
An Investigation of Bioenergy Sources: Classifications and Applications
Master's Research
Most countries are searching for renewable energy resources due to the depletion of fossil fuels and their environmental issues. In our project, we made an investigation into bioenergy sources, classifications, and applications. Fossil fuels are less environmentally- friendly than algal biomass which are sustainable, renewable, and effective for biofuel production. This work aimed to provide a state-of-the-art review of the pyrolysis of microalgae for the generation of biofuels. Initially, some general aspects of biomass such as microalgae characteristics, different thermochemical processes, and advantages of microalgae pyrolysis to produce bio-fuels are discussed. Then, different pyrolysis methods were explained and parameters affecting the process are addressed. Bio-fuels including gaseous, solid, and liquid products have been characterized and the technical challenges associated with microalgal pyrolysis commercialization are discussed.
The diagram of slow pyrolysis system.
Highlights:
​This project reviewed the whole processes followed for the production of biofuel from microalgal biomass using pyrolysis method by discussing:
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Microalgae characterization​
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Thermochemical conversion of microalgal biomass (gasification, liquification, direct combustion, and pyrolysis)
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Advantages of bio-fuel production through pyrolysis of microalgae
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Pyrolysis of microalgae (slow, fast, catalytic, Microwave assisted pyrolysis (MAP), and hydropyrolysis
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Parameters affecting the pyrolysis of microalgae
Comparison of typical properties of fossil oil and bio-oil from fast pyrolysis of wood and microalgae
Projects
(Left) The microfluidic devices fabricated in the cleanroom at the University of Michigan, Dearborn campus. (Right) My happy face after the successful fabrication of the device with clean microchannels.
Poly-lysine coated microfluidic devices enhance the migration of HACAT Cells
Migration of cells or the relocation of cells happens usually during vital cellular processes such as tissue renewal and repair, wherein cells migrate in response to external signals like chemical or mechanical signals. Cell migration is relevant to wound healing, immunology, embryonic development, and irregular cellular events such as cancer metastasis. In this project, a microfluidic device is modeled and fabricated to testify the migration of cells under different conditions. The microfluidic device surface is coated first with poly-lysine to enhance cell attachment and later, it is incubated with HACAT cells at 37°C and 5% CO2 for 5 hrs. Stamp and tip scratch with and without gradient oxygen is applied and ATP data was collected.
Experimental Insight into the Hemodynamics and Perfusion of Radiological Contrast in Patent Dissection Model (Course Project)
Aortic disease is a disease that is considered fatal and in the same time challenging to treat. In this project, we tried to relate the velocities in the true and the false lumens to the progression of the disease. Monitoring the velocity fields of the blood in the true and false lumens can help us in finding a proper treatment for this disease. This experiment investigated the effect of aortic disease on blood flow velocity using centrifugal and peristaltic pump and studied the effect of vortices and shear layers on the flow rate of the blood.
(Left) Schematic of the AD flow loop and optical imaging measurement setup used in both PIV and LIF. (Right) A picture of one optically clear AD model installed in the test setup and illuminated by the laser sheet.
Biomass District Heating System (Final Year Project - LIU)
This work aimed to use renewable sources such as "Biomass" for district heating. Nowadays, heat networks are considered of high interest due to the fact of less fees paid by people and more friendly to the environment. In this system, a boiler was used to burn the biomass that increases the temperature of circulating water. Then using heat exchangers, hot water was divided into domestic and space heating. The system was able to achieve a comparable efficiency compared to others that use gas. Moreover, the cost of biomass used are null as they were wastes of the environment and factories.
Illustration of the district heating network.