Engineering Commons^™

A Rapid And Ultra-Sensitive Biosensing Platform Based On Tunable Dielectrophoresis For Robust Poc Applications, Yu Jiang

Doctoral Dissertations

With the ongoing pandemic, there have been increasing concerns recently regarding major public health issues such as abuse of organophosphorus compounds, pathogenic bacterial infections, and biosecurity in agricultural production. Biosensors have long been considered a kernel technology for next-generation diagnostic solutions to improve food safety and public health. Significant amounts of effort have been devoted to inventing novel sensing mechanisms, modifying their designs, improving their performance, and extending their application scopes. However, the reliability and selectivity of most biosensors still have much to be desired, which holds back the development and commercialization of biosensors, especially for on-site and point-of-care (POC) …

Dynamic Behavior And Interactions Of Ferrofluid Droplets Under Magnetic Fields In Low Reynolds Number Flows, Md Rifat Hassan

Doctoral Dissertations

Digital microfluidics in combination with emulsion microfluidics are crucial building blocks of droplet-based microfluidics, which are prevalent in a wide variety of industrial and biomedical applications, including polymer processing, food production, drug delivery, inkjet printing, and cell-based assays. Therefore, understanding the dynamics and interactions of droplets as well as the interactions between the droplets and solid surfaces are of great importance in order to improve the performance or product in these applications.

Recently, several studies in the literature have demonstrated the potential of magnetic fields in controlling the behavior of droplets in microscale; however, the fundamental mechanism behind the interesting …

Engineering Platforms For Advancing Plant Synthetic Biology, Tayler Marie Schimel Mcneillie

Doctoral Dissertations

This work describes research aimed at adapting advanced engineering systems for plant biotechnology. The droplet interface bilayer (DIB) is a robust and versatile platform for replicating model cell membranes, providing a bottom-up approach for synthetic cell- and tissue-like structures. In this work, a microfluidic device featuring five inlets, one for the continuous oil phase and four discrete aqueous channels for droplet generation was designed. Droplet production rates were controlled by adjusting the applied pressure of each inlet; and thus, altering the droplet sequence for capturing linear DIB networks in a downstream hydrodynamic trapping array. This microfluidic system provides a high-throughput …

Magnetic Control Of Transport Of Particles And Droplets In Low Reynolds Number Shear Flows, Jie Zhang

Doctoral Dissertations

“Magnetic particles and droplets have been used in a wide range applications including biomedicine, biological analysis and chemical reaction. The manipulation of magnetic microparticles or microdroplets in microscale fluid environments is one of the most critical processes in the systems and platforms based on microfluidic technology. The conventional methods are based on magnetic forces to manipulate magnetic particles or droplets in a viscous fluid.

In contrast to conventional magnetic separation method, several recent experimental and theoretical studies have demonstrated a different way to manipulate magnetic non-spherical particles by using a uniform magnetic field in the microchannel. However, the fundamental mechanism …

High-Throughput Functional System For Encapsulated Networks Of Model Cell Membranes, Mary-Anne Kim Anh Nguyen

Doctoral Dissertations

Synthetic lipid bilayers provide models of cell membranes to study biomolecular interactions and signal transduction. The droplet interface bilayer (DIB) is a highly versatile technique for assembling planar lipid membranes between water droplets in oil. The DIB method thus provides a unique capability for developing digital, droplet-based membrane platforms for rapid membrane characterization, drug screening and ion channel recordings. In this work, a new microfluidic system is presented that automates droplet generation, sorting, and sequential trapping in designated locations to enable rapid assembly of arrays of DIBs along with in situ electrical measurements. This platform provides repeatable processes for forming …

Improvement Of Fluorescence-Based Microfluidic Dna Analyzers, Collin Tranter

Doctoral Dissertations

A tremendous effort continues in the development of micro-total-analysis-systems; in support of this, many chemical passivation methods have been developed to enhance the biocompatibility of such microfluidic systems. However, the suitability of these passivation techniques to many fluorescence-based assays still remains inconsistent. This part of this work is focused on the performance of a third generation intercalating DNA dye when used within microfluidic devices treated with a select variety of passivating coatings. The results of these tests indicate that passivation coatings which are intended to shed DNA based on electrostatic repulsion will in fact imbibe the fluorescent DNA intercalating dye …

Fundamental Studies Of Electrochemical Reactions And Microfluidics In Proton Exchange Membrane Electrolyzer Cells, Jingke Mo

Doctoral Dissertations

In electrochemical energy devices, including fuel cells, electrolyzers and batteries, the electrochemical reactions occur only on triple phase boundaries (TPBs). The boundaries provide the conductors for electros and protons, the catalysts for electrochemical reactions and the effective pathways for transport of reactants and products. The interfaces have a critical impact on the overall performance and cost of the devices in which they are incorporated, and therefore could be a key feature to optimize in order to turn a prototype into a commercially viable product. For electrolysis of water, proton exchange membrane electrolyzer cells (PEMECs) have several advantages compared to other …

Transient Cfd Simulations Of Pumping And Mixing Using Electromagnetic, Fangping Yuan

Doctoral Dissertations

"In this dissertation, two dimensional and three dimensional, transient CFD simulations are conducted to investigate the active pumping and mixing in microfluidics driven by Electromagnetic/Lorentz force. Shallow disk/ring cylindrical microfluidic cell and shallow cuboid microfluidic cell with electrodes deposited on the bottom surface are modelled for mixing and pumping purposes respectively. By applying voltage across specific pair of electrodes, an ionic current is established in the weak conductive liquid present in the cell. The current interacts with an externally applied magnetic field generating a Lorentz force that causes fluid motion in the cell. Velocity vectors, electric potential distributions and ionic …

Unlocking The Secrets Of Multi-Flagellated Propulsion, Stefan Oma Nwandu-Vincent

Doctoral Dissertations

In this work, unique high-speed imaging platforms and an array of theoretical analysis methods are used to thoroughly investigate eukaryotic multi-flagellated propulsion using Tritrichomonas foetus as a test case. Through experimental observations through our imaging system with superior resolution and capture rate exceeding that of previous studies, it was discovered for the first time that the T. foetus employs a strategy similar to that of the “run and tumble” strategies found in bacteria and Chlamydomonas; it has two distinct flagellar beating patterns that result in two different body swimming motions, linear and turning swimming.

These two flagella patterns were …

Thermoelectric Elisa For Quantification Of 8ohdg In A Microfluidic Device, Gergana Nestorova

Doctoral Dissertations

This research demonstrates the feasibility of a novel method for performing thermoelectric enzyme-linked immunosorbent assay (ELISA) in a microfluidic device. The feasibility of the thermoelectric ELISA is demonstrated by measuring the concentration of 8-hydroxy 2-deoxyguanosine (8OHdG) in urine samples from amyloid precursor protein (APP) transgenic mice. The detection method is based on formation of a complex between 8OHdG and anti-8OHdG capture antibody conjugated to biotin. The complex is immobilized over the measuring junctions of a thermopile via biotin streptavidin interaction. The concentration of the analyte is determined by using enzyme linked secondary IgG antibody specific to the primary one. The …

Microfluidic Devices Applied On Enriching Post –Translational Modified Proteins For Proteomics, Hui Xia

Doctoral Dissertations

In this work, microfluidic devices were developed for enriching post-translational modified proteins. Post-translational modifications (PTM) of proteins play essential roles in cellular physiology and disease. The identification of protein substrates and detection of modification site helps understand PTM-mediated regulation in essential biological pathways and functions in various diseases. However, PTM proteins are typically present only at trace levels, making them difficult to identify in mass spectrometry based proteomics. This work study is about the design, fabrication and testing of the microfluidic device for the enrichment of abundant amount of PTMs. Carbonylated protein is used as a representative PTM to illustrate …

Real-Time Analysis Of Brain Tumor Cell Dynamics: Novel Thermoelectric Detection Of L-Glutamate And Cell Metabolism Using Microfluidics, Siva Mahesh Tangutooru

Doctoral Dissertations

This study describes the design, fabrication and applications of a novel thermoelectric microfluidic bio-sensor. The bio-sensor is used for real time detection of the L-glutamate (L-glu) dynamics and metabolism for brain tumor cells immobilized in a microfluidic device. The microfluidic device is fabricated using a polymer/glass laminating technique (Xurography). An antimony-bismuth thin-film thermopile (primary sensing element) is integrated to the microfluidic device. The brain tumor cells are immobilized over the thermopile covering measuring and reference junctions of the thermopile using a poly-l-lysine coating layer. L-glutamate oxidase (L-GLOD) is immobilized over the measuring junctions of the thermopile prior to the immobilization …

Exploitation And Exploration Of Pcr In Microfluidic Systems With Gradient Temperature Environments, Ilija Pjescic

Doctoral Dissertations

The main goal of the work was to establish a wholesome picture off all relevant processes for a sample-in, answer out genetic system and to integrate the whole process on a one step device from sample collection to final result. The genetic analysis process consists of ideally three steps: sample preparation, chemical reaction, and analysis. Each of the steps is different and requires a specific environment, where sample preparation might use additives, they might later interfere with the reaction itself or lead to misleading results in the analysis phase. It was found to be quite a challenging process to synchronize …

In Situ Preconcentration By Ac Electrokinetics For Rapid And Sensitive Nanoparticle Detection, Kai Yang

Doctoral Dissertations

Reducing cost and time is a major concern in clinical diagnostics. Current molecular diagnostics are multi-step processes that usually take at least several hours or even days to complete multiple reagents delivery, incubations and several washing processes. This highly labor-intensive work and lack of automation could result in reduced reliability and low efficiency. The Laboratory-on-a-chip (LOC), taking advantage of the merger and development of microfluidics and biosensor technology, has shown promise towards a solution for performing analytical tests in a self-contained and compact unit, enabling earlier and decentralized testing. However, challenges are to integrate the fluid regulatory elements on a …

Microfluidic Manipulation By Ac Electrothermal Effect, Meng Lian

Doctoral Dissertations

AC Electrokinetics (ACEK) has attracted much research interest for microfluidic manipulation for the last few years. It shows great potential for functions such as micropumping, mixing and concentrating particles. Most of current ACEK research focuses on AC electroosmosis (ACEO), which is limited to solutions with conductivity less than 0.02 S/m, excluding most biofluidic applications. To solve for this problem, this dissertation seeks to apply AC electrothermal (ACET) effect to manipulate conductive fluids and particles within, and it is among the first demonstration of ACET devices, a particle trap and an ACET micropump. The experiments used fluids at a conductivity of …

Experimental Investigation Of Flow And Heat Transfer Characteristics Of R -134a In Microchannels, Abdullahel Bari

Doctoral Dissertations

The purpose of this study was to investigate the flow and heat transfer characteristics of liquid refrigerant R-134a in rectangular microchannels. The research concentrated mostly upon single-phase experiments with limited investigation of boiling phenomenon in microchannels. Tests were performed using rectangular microchannels with hydraulic diameters ranging from 112 μm to 210 μm and aspect ratios varying approximately from 1.0 to 1.5. The Reynolds number in the experiments ranged from 1,200 to 13,000 although most data were collected in the transition and turbulent flow regimes.

The experimental data for friction factor measurement had a similar trend as predicted by macroscale theory …

Investigation Of Ethanol Dehydration In A Microscale Pervaporation Process, Sudhir Ramprasad

Doctoral Dissertations

Challenges due to surface tension effects for vaporization in microchannels have restricted the implementation of conventional separation processes that involve liquid boiling in a micro-chemical system. However, membrane separations offer a feasible alternative for exploring the advantages of liquid phase separation in micro-chemical systems. The main objective of this research was to evaluate the process intensification effects in a microscale pervaporation process with experiments involving the separation of ethanol/water using a commercially available polymer dehydration membrane.

The microchannels in the microseparator were fabricated by the dry etch process at Louisiana Tech University. Microchannel depths of 20 to 120 μm, with …