Current Search:  Microfluidics (x)

View All Items

  • CSV Spreadsheet
(1 - 13 of 13)
A CUSTOMER PROGRAMMABLE MICROFLUIDIC SYSTEM
Title
A CUSTOMER PROGRAMMABLE MICROFLUIDIC SYSTEM.
Creator
Liu, Miao, Chen, Quanfang, University of Central Florida
Abstract / Description
Microfluidics is both a science and a technology offering great and perhaps even revolutionary capabilities to impact the society in the future. However, due to the scaling effects there are unknown phenomena and technology barriers about fluidics in microchannel, material properties in microscale and interactions with fluids are still missing. A systematic investigation has been performed aiming to develop "A Customer Programmable Microfluidic System". This innovative Polydimethylsiloxane ...
Show moreMicrofluidics is both a science and a technology offering great and perhaps even revolutionary capabilities to impact the society in the future. However, due to the scaling effects there are unknown phenomena and technology barriers about fluidics in microchannel, material properties in microscale and interactions with fluids are still missing. A systematic investigation has been performed aiming to develop "A Customer Programmable Microfluidic System". This innovative Polydimethylsiloxane (PDMS)-based microfluidic system provides a bio-compatible platform for bio-analysis systems such as Lab-on-a-chip, micro-total-analysis system and biosensors as well as the applications such as micromirrors. The system consists of an array of microfluidic devices and each device containing a multilayer microvalve. The microvalve uses a thermal pneumatic actuation method to switch and/or control the fluid flow in the integrated microchannels. It provides a means to isolate samples of interest and channel them from one location of the system to another based on needs of realizing the customers' desired functions. Along with the fluid flow control properties, the system was developed and tested as an array of micromirrors. An aluminum layer is embedded into the PDMS membrane. The metal was patterned as a network to increase the reflectivity of the membrane, which inherits the deformation of the membrane as a mirror. The deformable mirror is a key element in the adaptive optics. The proposed system utilizes the extraordinary flexibility of PDMS and the addressable control to manipulate the phase of a propagating optical wave front, which in turn can increase the performance of the adaptive optics. Polydimethylsiloxane (PDMS) has been widely used in microfabrication for microfluidic systems. However, few attentions were paid in the past to mechanical properties of PDMS. Importantly there is no report on influences of microfabrication processes which normally involve chemical reactors and biologically reaction processes. A comprehensive study was made in this work to study fundamental issues such as scaling law effects on PDMS properties, chemical emersion and temperature effects on mechanical properties of PDMS, PDMS compositions and resultant properties, as well as bonding strength, etc. Results achieved from this work will provide foundation of future developments of microfluidics utilizing PDMS.
Show less
Date Issued
2008
Identifier
CFE0002372, ucf:47798
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002372
RAPID PROTOTYPING OF MICROFLUIDIC PACKAGES
Title
RAPID PROTOTYPING OF MICROFLUIDIC PACKAGES.
Creator
Pepper, Michael, Cho, Hyoung, University of Central Florida
Abstract / Description
In the area of MEMS there exists a tremendous need for communication between the micro-device and the macro world. A standard protocol or at least multiple standards would be of great use. Electrical connections have been standardized for many uses and configurations by the integrated circuit industry. Standardization in the IC industry has created a marketplace for digital devices unprecedented. In addition to the number of "off the shelf" products available, there exists the possibility for...
Show moreIn the area of MEMS there exists a tremendous need for communication between the micro-device and the macro world. A standard protocol or at least multiple standards would be of great use. Electrical connections have been standardized for many uses and configurations by the integrated circuit industry. Standardization in the IC industry has created a marketplace for digital devices unprecedented. In addition to the number of "off the shelf" products available, there exists the possibility for consumers to mix and match many devices from many different manufacturers. This research proposes some similar solutions as those for integrated circuits for fluid connections and mechanical configurations that could be used on many different devices. In conjunction with offering the capability to facilitate communication between the micro and macro worlds, the packaging solutions should be easy to fabricate. Many devices are by nature non-standard, unique, designs that make a general solution difficult. At the same time, the micro-devices themselves will inevitably need to evolve some standardization. In BioMEMS devices the packaging issue is concerned with delivering a sample to the device, conducting the sample to the sensor or sensors, and removing the sample. Conducting the sample to the sensor or sensors is usually done with microchannels created by standard MEMS fabrication techniques. Many current designs then utilize conventional machining techniques to create the inlet and outlet for the sample. This work proposes a rapid prototyping method for creating the microchannel and inlet / outlet in simplified steps. The packages developed from this process proved to be an effective solution for many applications.
Show less
Date Issued
2006
Identifier
CFE0001341, ucf:46979
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001341
DROPLET FLOWS IN MICROCHANNELS USING LATTICE BOLTZMANN METHOD
Title
DROPLET FLOWS IN MICROCHANNELS USING LATTICE BOLTZMANN METHOD.
Creator
Gupta, Amit, Kumar, Ranganathan, University of Central Florida
Abstract / Description
Microelectromechanical systems (MEMS) have widespread applications in medical, electronical and mechanical devices. These devices are characterized by the smallest dimension which is atleast one micrometer and utmost one millimeter. Rapid progress in the manufacture and utilization of these microdevices has been achieved in the last decade. Current manufacturing techniques of such devices and channels include surface silicon micromachining; bulk silicon micromachining; lithography;...
Show moreMicroelectromechanical systems (MEMS) have widespread applications in medical, electronical and mechanical devices. These devices are characterized by the smallest dimension which is atleast one micrometer and utmost one millimeter. Rapid progress in the manufacture and utilization of these microdevices has been achieved in the last decade. Current manufacturing techniques of such devices and channels include surface silicon micromachining; bulk silicon micromachining; lithography; electrodeposition and plastic molding; and electrodischarge machining (EDM). In recent years, electrostatic, magnetic, electromagnetic and thermal actuators, valves, gears and diaphragms of dimensions of hundred microns or less have been fabricated successfully. Sensors have been manufactured that can detect pressure, temperature, flow rate and chemical composition in such channels. Physical effects such as electrokinetics, pressure gradient and capillarity become prominent for channels where the length scales are of the order of hundreds of micrometers. Also, at such length scales, the application of conventional numerical techniques that use macroscale equations to describe the phenomenon is questionable as the validity of the no-slip boundary condition depends on the ratio of the mean free path of the fluid molecules to the characteristic dimension of the problem (called the Knudsen number). Macroscale equations can only be applied if Knudsen number is of the order of 10¬¬-3 or less. In recent years, the lattice Boltzmann method (LBM) has emerged as a powerful tool that has replaced conventional macroscopic techniques like Computational Fluid Dynamics (CFD) in many applications involving complex fluid flow. The LBM starts from meso- and microscopic Boltzmann's kinetic equation and can be used to determine macroscopic fluid dynamics. The origins of LBM can be drawn back to lattice gas cellular automata (LGCA) which lacked Galilean invariance and created statistical noise in the system. LBM on the other hand possesses none of these drawbacks of LGCA, and is easy to implement in complex geometries and can be used to study detailed microscopic flow behavior in complex fluids/fluid mixtures. Nor does it have any of the drawbacks of the Navier-Stokes solvers of implementing the slip boundary condition on the surface of a solid. It has also been found to be computationally fast and an alternative to Navier-Stokes equations. In this study, LBM is used to simulate two-fluid flows such as bubbles rising in a liquid, droplet impingement on a dry surface and creation of emulsions in microchannels. Simulation of disperse flows in a continuous medium using simple boundary condition methods lays the foundation of conducting complex simulations for the formation of droplets past a T-junction microchannel in the framework of this statistical method. Simulations in a T-junction illustrate the effect of the channel geometry, the viscosity of the liquids and the flow rates on the mechanism, volume and frequency of formation of these micron-sized droplets. Based on the interplay of viscous and surface tension forces, different shapes and sizes of droplets were found to form. The range of Capillary numbers simulated lies between 0.001Show less
Date Issued
2009
Identifier
CFE0002618, ucf:48279
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002618
MAPPING OF PRESSURE LOSSES THROUGH MICROCHANNELS WITH SWEEPING-BENDS OF VARIOUS ANGLE AND RADII
Title
MAPPING OF PRESSURE LOSSES THROUGH MICROCHANNELS WITH SWEEPING-BENDS OF VARIOUS ANGLE AND RADII.
Creator
hansel, chase, Chew, Larry, University of Central Florida
Abstract / Description
MEMS (Micro Electro Mechanical Systems) have received a great deal of attention in both the research and industrial sectors in recent decades. The broad MEMS category, microfluidics, the study of fluid flow through channels measured on the micrometer scale, plays an important role in devices such as compact heat exchangers, chemical and biological sensors, and lab-on-a-chip devices. Most of the research has been focused on how entire systems operate, both experimentally and through simulation...
Show moreMEMS (Micro Electro Mechanical Systems) have received a great deal of attention in both the research and industrial sectors in recent decades. The broad MEMS category, microfluidics, the study of fluid flow through channels measured on the micrometer scale, plays an important role in devices such as compact heat exchangers, chemical and biological sensors, and lab-on-a-chip devices. Most of the research has been focused on how entire systems operate, both experimentally and through simulation. This paper strives, systematically, to map them through experimentation of the previous to untested realm of pressure loss through laminar square-profile sweeping-bend microchannels. Channels were fabricated in silicone and designed so a transducer could detect static pressure across a very specific length of channel with a desired bend. A wide variety of Reynolds numbers, bend radii, and bend angles were repeatedly tested over long periods in order to acquire a complete picture of pressure loss with in the domain of experimentation. Nearly all situations tested were adequately captured with the exception of some very low loss points that were too small to detect accurately. The bends were found to match laminar straight-duct theory at Reynolds numbers below 30. As Reynolds numbers increased, however, minor losses began to build and the total pressure loss across the bend rose above straight-duct predictions. A new loss coefficient equation was produced that properly predicted pressure losses for sweeping-bends at higher Reynolds numbers; while lower flow ranges are left to laminar flow loss for prediction.
Show less
Date Issued
2008
Identifier
CFE0002091, ucf:47537
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002091
PRODUCTION, CONTROL AND ACTUATION OF MICRON-SIZED PARTICLES IN AMICROFLUIDIC T-JUNCTION
Title
PRODUCTION, CONTROL AND ACTUATION OF MICRON-SIZED PARTICLES IN AMICROFLUIDIC T-JUNCTION.
Creator
Wilson, James, Kumar, Ranganathan, University of Central Florida
Abstract / Description
This research is directed towards understanding the mechanisms associated with the manufacture of solid microspheres less than 100 [micro]m, from liquid droplets with nanosuspensions in a microfluidic T-junction, which are heated downstream of the channel. Preliminary material characterization tests on colloidal suspensions of alumina and copper oxide demonstrate promising temperature dependent viscosity results indicating solidification in the temperature range of 40degC-50degC. The...
Show moreThis research is directed towards understanding the mechanisms associated with the manufacture of solid microspheres less than 100 [micro]m, from liquid droplets with nanosuspensions in a microfluidic T-junction, which are heated downstream of the channel. Preliminary material characterization tests on colloidal suspensions of alumina and copper oxide demonstrate promising temperature dependent viscosity results indicating solidification in the temperature range of 40degC-50degC. The solidification mechanism is referred to as Temperature Induced Forming and is described by polymeric bridges formed between nanoparticles in suspension at elevated temperatures, resulting in a solid structure. The polymer network results from the ionization of alumina at elevated temperatures whereby polymeric binders adhere to newly formed charged sites on the alumina particle. This study aims to investigate the aspects of manufacturing microstructures in microfluidic Tjunctions, droplet morphology, size and frequency of production. Preliminary low solid concentration experiments (1%-10% volume concentration of alumina in H2O) have indicated solidification and a regression in droplet diameter when heated near the saturation temperature of the water used to disperse the particles. The microstructures from this solidification process are uniform and are estimated to be 30 [micro]m in size.
Show less
Date Issued
2013
Identifier
CFH0004387, ucf:44996
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH0004387
LOW REYNOLDS NUMBER WATER FLOW CHARACTERISTICS THROUGH RECTANGULAR MICRO DIFFUSERS/NOZZLES WITH A PRIMARY FOCUS ON MAJOR/MINOR PRESSURE LOSS, STATIC PRESSURE RECOVERY, AND FLOW SEPARATION
Title
LOW REYNOLDS NUMBER WATER FLOW CHARACTERISTICS THROUGH RECTANGULAR MICRO DIFFUSERS/NOZZLES WITH A PRIMARY FOCUS ON MAJOR/MINOR PRESSURE LOSS, STATIC PRESSURE RECOVERY, AND FLOW SEPARATION.
Creator
Hallenbeck, Kyle, Chew, Larry, University of Central Florida
Abstract / Description
The field of microfluidics has recently been gathering a lot of attention due to the enormous demand for devices that work in the micro scale. The problem facing many researchers and designers is the uncertainty in using macro scaled theory, as it seems in some situations they are incorrect. The general idea of this work was to decide whether or not the flow through micro diffusers and nozzles follow the same trends seen in macro scale theory. Four testing wafers were fabricated using PDMS...
Show moreThe field of microfluidics has recently been gathering a lot of attention due to the enormous demand for devices that work in the micro scale. The problem facing many researchers and designers is the uncertainty in using macro scaled theory, as it seems in some situations they are incorrect. The general idea of this work was to decide whether or not the flow through micro diffusers and nozzles follow the same trends seen in macro scale theory. Four testing wafers were fabricated using PDMS soft lithography including 38 diffuser/nozzle channels a piece. Each nozzle and diffuser consisted of a throat dimension of 100μm x 50μm, leg lengths of 142μm, and half angles varying from 0o – 90o in increments of 5o. The flow speeds tested included throat Reynolds numbers of 8.9 – 89 in increments of 8.9 using distilled water as the fluid. The static pressure difference was measured from the entrance to the exit of both the diffusers and the nozzles and the collected data was plotted against a fully attached macro theory as well as Idelchik's approximations. Data for diffusers and nozzles up to HA = 50o hints at the idea that the flow is neither separating nor creating a vena contracta. In this region, static pressure recovery within diffuser flow is observed as less than macro theory would predict and the losses that occur within a nozzle are also less than macro theory would predict. Approaching a 50o HA and beyond shows evidence of unstable separation and vena contracta formation. In general, it appears that there is a micro scaled phenomenon happening in which flow gains available energy when the flow area is increased and looses available energy when the flow area decreases. These new micro scaled phenomenon observations seem to lead to a larger and smaller magnitude of pressure loss respectively.
Show less
Date Issued
2008
Identifier
CFE0002391, ucf:47772
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002391
Modeling Transport and Protein Adsorption in Microfluidic Systems
Title
Modeling Transport and Protein Adsorption in Microfluidic Systems.
Creator
Finch, Craig, Hickman, James, Kincaid, John, Lin, Kuo-Chi, Behal, Aman, Cho, Hyoung, University of Central Florida
Abstract / Description
This work describes theoretical advances in the modeling and simulation of microfluidic systems and demonstrates the practical application of those techniques. A new multi-scale model of the adsorption of hard spheres was formulated to bridge the gap between simulations of discrete particles and continuum fluid dynamics. A whispering gallery mode (WGM) biosensor was constructed and used to measure the kinetics of adsorption for two types of proteins on four different surfaces. Computational...
Show moreThis work describes theoretical advances in the modeling and simulation of microfluidic systems and demonstrates the practical application of those techniques. A new multi-scale model of the adsorption of hard spheres was formulated to bridge the gap between simulations of discrete particles and continuum fluid dynamics. A whispering gallery mode (WGM) biosensor was constructed and used to measure the kinetics of adsorption for two types of proteins on four different surfaces. Computational fluid dynamics was used to analyze the transport of proteins in the flow cell of the biosensor. Kinetic models of protein adsorption that take transport limitations into account were fitted to the experimental data and used to draw conclusions about the mechanisms of adsorption. Transport simulations were then applied to the practical problem of optimizing the design of a microfluidic bioreactor to enable (")plugs(") of fluid to flow from one chamber to the next with minimal dispersion. Experiments were used to validate the transport simulations. The combination of quantitative modeling and simulation and experiments led to results that could not have been achieved using either approach by itself. Simulation tools that accurately predict transport and protein adsorption will enable the rational design of microfluidic devices for biomedical applications.
Show less
Date Issued
2011
Identifier
CFE0004474, ucf:49313
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004474
Polyelectrolyte and hydrogel stabilized liquid crystal droplets for the detection of bile acids
Title
Polyelectrolyte and hydrogel stabilized liquid crystal droplets for the detection of bile acids.
Creator
Deng, Jinan, Fang, Jiyu, An, Linan, Chen, Quanfang, Cho, Hyoung Jin, Wu, Shintson, University of Central Florida
Abstract / Description
Liquid crystal (LC) droplets show great potential as an optical probe for sensor applications due to their large surface areas and stimuli-response director configurations. Bile acids with amphipathic properties, which are formed in liver and secreted into the small intestine, play an important role in the digestion of fats and fat-soluble vitamins. After the digestion process, most of bile acids are recycled back to the liver and ready for the next digestion. Only a few of them are excreted...
Show moreLiquid crystal (LC) droplets show great potential as an optical probe for sensor applications due to their large surface areas and stimuli-response director configurations. Bile acids with amphipathic properties, which are formed in liver and secreted into the small intestine, play an important role in the digestion of fats and fat-soluble vitamins. After the digestion process, most of bile acids are recycled back to the liver and ready for the next digestion. Only a few of them are excreted into body fluids. However, there is significant increases in the concentration level of bile acids in body fluids for patients with liver and intestinal diseases, which makes bile acids a biomarker for the early diagnosis of liver and intestinal diseases. Chromatography-mass spectrometry and electrochemical sensors are common methods for the detection of bile acids. However, these detection methods are time consuming, require relatively large sample volumes, and expensive instruments. To date, there is still a demand in the development of simple, low-cost and user-friendly sensing platforms for the rapid detection of bile acids in clinical settings.In this dissertation, two simple and low-cost LC droplet-based sensing platforms were developed for the rapid and real-time detection of bile acids with a small sample volume. First, a miniaturized LC droplet-based sensor platform was designed and fabricated by the integration of polyelectrolytes/surfactant/sulfate ?-cyclodextrin (?-CD) complex-stabilized LC droplets into a microfluidic channel for the selective detection of bile acids in a small amount of solution, in which the ?-CD immobilized at the surface of the LC droplets acts as a selective barricade and the director configuration of the LC droplets serves as an optical probe. Second, a flexible LC droplet-based sensor platform was formed by the integration of surfactant-stabilized LC droplets in biopolymer hydrogel films. The LC droplet-based hydrogel film was cut into small sheets for the real-time detection of bile acids in a small amount of solution, in which the configuration transition of LC droplets induced by the interaction of bile acids with the surfactants absorbing on the surface of LC droplets serves as an optical probe.Cholic acid (CA) and deoxycholic acid (DCA), which are the most related to the liver and intestinal diseases, were detected in phosphate buffered saline (PBS) solution in the presence of the interference species of uric acid (UA) and ascorbic acid (AA) in this dissertation. These miniaturized LC droplet-based sensor platforms can be used to selectively detect CA and DCA in the presence of UA and AA. The detection limit of these sensor platforms for CA and DCA can be tuned by the number of LC droplets and the nature of surfactants. Furthermore, we find that these sensor platforms are more sensitive for DCA with the shorter response time and lower detection limit over CA due to their difference in hydrophobicity. These miniaturized 5CB droplet-based sensor platforms are easily handled, allowing the rapid and real-time detection of bile acids in a small sample volume in the presence of interference species, which are highly desirable for the "point-of-care" analysis of bile acids.
Show less
Date Issued
2017
Identifier
CFE0006939, ucf:51664
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006939
INTERCONNECTION, INTERFACE AND INSTRUMENTATION FOR MICROMACHINED CHEMICAL SENSORS
Title
INTERCONNECTION, INTERFACE AND INSTRUMENTATION FOR MICROMACHINED CHEMICAL SENSORS.
Creator
Palsandram, Naveenkumar, Sundaram, Kalpathy, University of Central Florida
Abstract / Description
In realizing a portable chemical analysis system, adequate partitioning of a reusable component and a disposable is required. For successful implementation of micromachined sensors in an instrument, reliable methods for interconnection and interface are in great demand between these two major parts. This thesis work investigates interconnection methods of micromachined chip devices, a hybrid fluidic interface system, and measurement circuitry for completing instrumentation. The...
Show moreIn realizing a portable chemical analysis system, adequate partitioning of a reusable component and a disposable is required. For successful implementation of micromachined sensors in an instrument, reliable methods for interconnection and interface are in great demand between these two major parts. This thesis work investigates interconnection methods of micromachined chip devices, a hybrid fluidic interface system, and measurement circuitry for completing instrumentation. The interconnection method based on micromachining and injection molding techniques was developed and an interconnecting microfluidic package was designed, fabricated and tested. Alternatively, a plug-in type design for a large amount of sample flow was designed and demonstrated. For the hybrid interface, sequencing of the chemical analysis was examined and accordingly, syringe containers, a peristaltic pump and pinch valves were assembled to compose a reliable meso-scale fluidic control unit. A potentiostat circuit was modeled using a simulation tool. The simulated output showed its usability toward three-electrode electrochemical microsensors. Using separately fabricated microsensors, the final instrument with two different designs--flow-through and plug-in type was tested for chlorine detection in water samples. The chemical concentration of chlorine ions could be determined from linearly dependent current signals from the instrument.
Show less
Date Issued
2005
Identifier
CFE0000673, ucf:46516
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000673
INTEGRATION OF A NANOSTRUCTURE EMBEDDED THERMORESPONSIVE POLYMER FOR MICROFLUIDIC APPLICATIONS
Title
INTEGRATION OF A NANOSTRUCTURE EMBEDDED THERMORESPONSIVE POLYMER FOR MICROFLUIDIC APPLICATIONS.
Creator
Londe, Ghanashyam, Cho, Hyoung Jin, University of Central Florida
Abstract / Description
This work describes the modeling, synthesis, integration and characterization of a novel nanostructure embedded thermoresponsive material for microfluidic applications. The innumerable applications of thermoresponsive surfaces in the recent years have necessitated the development of a rigorous mathematical treatment for these surfaces to understand and improve their behavior. An analytical model is proposed to describe the transfer characteristic (variation of contact angle versus temperature...
Show moreThis work describes the modeling, synthesis, integration and characterization of a novel nanostructure embedded thermoresponsive material for microfluidic applications. The innumerable applications of thermoresponsive surfaces in the recent years have necessitated the development of a rigorous mathematical treatment for these surfaces to understand and improve their behavior. An analytical model is proposed to describe the transfer characteristic (variation of contact angle versus temperature) of a unique switchable, nanostructured, thermoresponsive surface consisting of silica nanoparticles and the thermoresponsive polymer, Poly(N-isopropylacrylamide ) (PNIPAAm) which changes its wetting angle upon heating. Important metrics such as the absolute lower critical solution temperature, threshold & saturation temperatures and gain are modeled and quantified by mathematical expressions. Based on the modeling, a heat source for the thermoresponsive surface was integrated on the glass substrate itself to create a fully functional smart surface. The design and fabrication of a smart platform consisting of the switchable, nanostructured, thermoresponsive surface with an integrated gold microheater for wettability control and its time response analysis was conducted. The insight gained into the behavior of the thermoresponsive surface by using the analytical model, aided the effort in the effective integration of the surface into a microfluidic channel for flow regulation applications. The implementations of novel microfluidic flow regulator concepts were tested. The aim is to integrate a regulator function to a channel surface utilizing the layer-by-layer (LBL) deposition technique. The characterization and pressure differential study of the microfluidic regulators was carried out on simple straight microchannels which were selectively coated with the thermoresponsive surface. Theoretical and experimental studies were performed to determine the important characteristic parameters including capillary, Weber and Reynolds numbers. The pressure differential data was used to develop critical operating specifications. This work lays out a new microfluidic device concept consisting of a channel with a built-in regulatory function.
Show less
Date Issued
2008
Identifier
CFE0002368, ucf:47786
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002368
Development of in vitro point of care diagnostics (IVPCD) based on Aptamers integrated Biosensors.(&)nbsp;
Title
Development of in vitro point of care diagnostics (IVPCD) based on Aptamers integrated Biosensors.(&)nbsp;.
Creator
Saraf, Nileshi, Seal, Sudipta, Fang, Jiyu, Florczyk, Stephen, Dong, Yajie, Self, William, University of Central Florida
Abstract / Description
The global market for the medical diagnostic industry is worth 25 billion dollars in the United States and is expected to grow exponentially each year. Presently available methods for biodetection, such as immunoassays, chemiluminescence and fluorescent based assays are expensive, time consuming and require skilled labor with high-end instruments. Therefore, development of novel, passive colorimetric sensors and diagnostic technologies for detection and surveillance is of utmost importance...
Show moreThe global market for the medical diagnostic industry is worth 25 billion dollars in the United States and is expected to grow exponentially each year. Presently available methods for biodetection, such as immunoassays, chemiluminescence and fluorescent based assays are expensive, time consuming and require skilled labor with high-end instruments. Therefore, development of novel, passive colorimetric sensors and diagnostic technologies for detection and surveillance is of utmost importance especially in resource constrained communities. The present work focusses on developing novel and advanced in vitro biodiagnostic tools based on aptamer integrated biosensors for an early detection of specific viral proteins or small biomolecules used as potential markers for deadly diseases. Aptamers are short single stranded deoxyribonucleic acid (DNA) which are designed to bind to a specific target biomolecule. These are readily synthesized in laboratory and offers several advantages over antibodies/enzymes such as stable in harsh environment, easily functionalized for immobilization, reproducibility etc. These undergo conformational changes upon target binding and produces physical or chemical changes in the system which are measured as colorimetric or electrochemical signals. Here, we have explored the aptamer-analyte interaction on different platforms such as microfluidic channel, paper based substrate as well as organic electrochemical transistor to develop multiple compact, robust and self-contained diagnostic tools. These testing tools exhibit high sensitivity (detection limit in picomolar) and selectivity against the target molecule, require no sophisticated instruments or skilled labor to implement and execute, leading a way to cheaper and more consumer driver health care. These innovative platforms provide flexibility to incorporate additional or alternative targets by simply designing aptamers to bind to the specific biomolecule.
Show less
Date Issued
2018
Identifier
CFE0007766, ucf:52388
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007766
Electrohydrodynamic Manipulation of Liquid Droplet Emulsions in a Microfluidic Channel
Title
Electrohydrodynamic Manipulation of Liquid Droplet Emulsions in a Microfluidic Channel.
Creator
Wehking, Jonathan, Chew, Phyekeng, Chen, Quanfang, Chen, Ruey-Hung, University of Central Florida
Abstract / Description
This work specifically aims to provide a fundamental framework, with some experimental validation, for understanding droplet emulsion dynamics in a microfluidic channel with an applied electric field. Electrification of fluids can result in several different modes of electrohydrodynamics (EHD). Several studies to date have provided theoretical, experimental, and numerical results for stationary droplet deformations and some flowing droplet configurations, but none have reported a method by...
Show moreThis work specifically aims to provide a fundamental framework, with some experimental validation, for understanding droplet emulsion dynamics in a microfluidic channel with an applied electric field. Electrification of fluids can result in several different modes of electrohydrodynamics (EHD). Several studies to date have provided theoretical, experimental, and numerical results for stationary droplet deformations and some flowing droplet configurations, but none have reported a method by which droplets of different diameters can be separated, binned and routed through the use of electric fields. It is therefore the goal of this work to fill that void and report a comprehensive understanding of how the electric field can affect flowing droplet dynamics.This work deals with two primary models used in electrohydrodynamics: the leaky dielectric model and the perfect dielectric model. The perfect dielectric model assumes that fluids with low conductivities do not react to any effects from the small amount of free charge they contain, and can be assumed as dielectrics, or electrical insulators. The leaky dielectric model suggests that even though the free charge is minimal in fluids with low conductivities, it is still is enough to affect droplet deformations. Finite element numerical results of stationary droplet deformations, implemented using the level set method, compare well both qualitatively (prolate/oblate and vortex directions), and quantitatively with results published by other researchers. Errors of less than 7.5% are found when comparing three-dimensional (3D) numerical results of this study to results predicted by the 3D leaky dielectric model, for a stationary high conductivity drop suspended in a slightly lower conductivity suspending medium. Droplet formations in a T-junction with no applied electric field are adequately predicted numerically using the level set finite element technique, as demonstrated by other researchers and verified in this study. For 3D models, droplet size is within 6%, and droplet production frequency is within 2.4% of experimental values found in the microfluidic T-junction device. In order to reduce computational complexity, a larger scale model was solved first to obtain electrical potential distributions localized at the channel walls for the electrode placement configurations.Droplet deceleration and pinning is demonstrated, both experimentally and numerically, by applying steep gradients of electrical potential to the microchannel walls. As droplets flow over these electrical potential ``steps," they are pinned to the channel walls if the resulting electric forces are large enough to overcome the hydrodynamic forces. A balance between four dimensionless force ratios, the electric Euler number (Eu_e - ratio of inertial to electric forces), Mason number (Ma - ratio of viscous to electric forces), electric pressure (Ps - ratio of upstream pressure forces to electric forces), and the electric capillary number (Ca_e - ratio of electric to capillary forces) are used to quantify the magnitudes of each of these forces required to pin a droplet, and is consistent with a cubic dependency on the drop diameter. For larger drop diameters, effects of hydrodynamic forces become more prominent, and for smaller droplets, a greater electric forces is required due to the proximity of the droplet boundary with reference to the electrified channel wall. Droplet deceleration and pinning can be exploited to route droplets into different branches of a microfluidic T-junction. In addition, using steep electrical potential gradients placed strategically along a microchannel, droplets can even be passively binned by size into separate branches of the microfluidic device. These characteristics have been identified and demonstrated in this work.
Show less
Date Issued
2013
Identifier
CFE0005071, ucf:49950
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005071
Thermally induced motion, collision and mixing of levitated droplets
Title
Thermally induced motion, collision and mixing of levitated droplets.
Creator
Davanlou, Ashkan, Kumar, Ranganathan, Cho, Hyoung Jin, Deng, Weiwei, Mansy, Hansen, Shivamoggi, Bhimsen, University of Central Florida
Abstract / Description
This dissertation investigates the motion of a levitated droplet experimentally and analytically against the Marangoni flow in an immiscible outer fluid at higher speeds than is possible currently. Based on our earlier experiments, when a droplet is released from a height of 1.5 (-) 4 times its diameter from the liquid surface, it can overcome the impact and stay levitated at the liquid-air interface due to the existence of an air gap between the droplet and the liquid film. In order to...
Show moreThis dissertation investigates the motion of a levitated droplet experimentally and analytically against the Marangoni flow in an immiscible outer fluid at higher speeds than is possible currently. Based on our earlier experiments, when a droplet is released from a height of 1.5 (-) 4 times its diameter from the liquid surface, it can overcome the impact and stay levitated at the liquid-air interface due to the existence of an air gap between the droplet and the liquid film. In order to explain this behavior of droplet traveling against the counter-current motion, we propose a simple approach: first, the Marangoni convection inside the thin film is considered without the droplet floating on the surface. By using a level-set method and solving the Navier-Stokes equation, the free surface velocity and deformation are calculated. Then, these quantities are used to solve for droplet velocity and drag coefficient simultaneously using a force balance. In order to compare the simulation results, experiments with levitated water droplets on an immiscible carrier liquid, FC-43, were conducted for various temperature gradients, and droplet velocities were measured at different locations using high-speed imaging. The experimental results are in good agreement with the developed theoretical model. For a Reynolds number range of 2-32, it is shown that the drag coefficients are up to 66% higher than those for the fully immersed sphere at the same Reynolds numbers. A correlation is proposed to calculate the drag coefficient of levitated droplets for various temperature drops across the channel.For the first time, it is shown that it is possible to realize the natural coalescence of droplets through Marangoni effect without any external stimulation, and deliver the coalesced droplet to a certain destination through the use of surface tension gradients. The effects of the various shapes and sizes upon collision are studied. Regions of coalescence and stretching separation of colliding droplets are delineated based on Weber number and impact number. The existence of the transition line between coalescence and stretching separation in this passive mode of transport is similar to what was observed in the literature for forced coalescence at significantly higher Weber numbers. It is also found that a thermocapillary environment improves the mixing process. In order to illustrate and quantify the mixing phenomenon, the dispensed droplets were made of potassium hydroxide and phenolphthalein which is used as a pH indicator. The experiments show the possibility to reach mixing rates as high as 74% within 120 ms. This study offers new insight to thermo-coalescence and demonstrates how natural coalescence could be used to transport, mix and collect biochemical assays more efficiently. The results of this research can be engineered to enhance the performance of self-cleaning surfaces and micro-total analysis systems ((&)#181;TAS), where sample transport, filtration, chemical reactions, separation and detection are of great interest.
Show less
Date Issued
2015
Identifier
CFE0006213, ucf:51106
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006213