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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.
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Date Issued: 2006
Identifier: CFE0001341, ucf:46979
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001341

Title: USER-DEFINED PATTERNING OF NEURAL PROGENITOR CELLS ON 3D MICROPILLAR ARRAYS USING ROUND CROSS-SECTIONAL GEOMETRY, SPECIFIC DIMENSIONS AND THIOL-BASED CHEMICAL ADHESION.
Creator: Wesser, Andrea, Cho, Hyoung Jin, University of Central Florida
Abstract / Description: The ability to control stem cell functions, particularly neuronal progenitors, has long since been believed to be the key to successful treatment of neurodegenerative disorders such as Alzheimer's, Parkinson's and accidents involving head trauma. The neurology field calls for many new solutions to address the controlled neural stem cell seeding and placement of cells for neural tissue regeneration. Self-assembled monolayers (SAM) from the alkanethiol group provide a straightforward...
Show moreThe ability to control stem cell functions, particularly neuronal progenitors, has long since been believed to be the key to successful treatment of neurodegenerative disorders such as Alzheimer's, Parkinson's and accidents involving head trauma. The neurology field calls for many new solutions to address the controlled neural stem cell seeding and placement of cells for neural tissue regeneration. Self-assembled monolayers (SAM) from the alkanethiol group provide a straightforward applicable, reliable treatment for cell adhesion. An ODT/gold treatment was used to adhere the cells to patterned areas, due mainly to a high confluence of cells attracted to it, as well as the viable environment it produced for the cells. Arrays of micropillars, made of SU-8 photoresist, then covered with a thin film of gold and treated with the ODT, created scaffolding allowing manipulation of neural stem cells. Based on multiple trials of observing varying cross-sectional geometric parameters, metal layer thicknesses and the ODT/Gold treatment, this study explores seeding density control, base and circumferential cell population dependence on those parameters.
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Date Issued: 2008
Identifier: CFE0002054, ucf:47563
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002054

Title: DESIGN AND FABRICATION OF CHEMIRESISTOR TYPEMICRO/NANO HYDROGEN GAS SENSORS USINGINTERDIGITATED ELECTRODES.
Creator: Zhang, Peng, Cho, Hyoung Jin, University of Central Florida
Abstract / Description: Hydrogen sensors have obtained increased interest with the widened application of hydrogen energy in recent years. Among them, various chemiresistor based hydrogen sensors have been studied due to their relatively simple structure and well-established detection mechanism. The recent progress in micro/nanotechnology has accelerated the development of small-scale chemical sensors. In this work, MEMS (Micro-Electro-Mechanical Systems) sensor platforms with interdigitated electrodes have been...
Show moreHydrogen sensors have obtained increased interest with the widened application of hydrogen energy in recent years. Among them, various chemiresistor based hydrogen sensors have been studied due to their relatively simple structure and well-established detection mechanism. The recent progress in micro/nanotechnology has accelerated the development of small-scale chemical sensors. In this work, MEMS (Micro-Electro-Mechanical Systems) sensor platforms with interdigitated electrodes have been designed and fabricated. Integrating indium doped tin dioxide nanoparticles, these hydrogen sensors showed improved sensor characteristics such as sensitivity, response and selectivity at room temperature. Design parameters of interdigitated electrodes have been studied in association with sensor characteristics. It was observed that these parameters (gap between the electrodes, width and length of the fingers, and the number of the fingers) imposed different impacts on the sensor performance. In order to achieve small, robust, low cost and fast hydrogen micro/nano sensors with high sensitivity and selectivity, the modeling and process optimization was performed. The effect of humidity and the influence of the applied voltage were also studied. The sensor could be tuned to have high sensitivity (105), fast response time (10 seconds) and low energy consumption (19 nW). Finally, a portable hydrogen instrument integrated with a micro sensor, display, sound warning system, and measurement circuitry was fabricated based on the calibration data of the sensor.
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Date Issued: 2008
Identifier: CFE0002478, ucf:47725
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002478

Title: MICROMACHINED ELECTROCHEMICAL SENSORS FOR HYDROGEN PEROXIDE AND CHLORINE DETECTION.
Creator: Mehta, Anjum, Cho, Hyoung (Joe), University of Central Florida
Abstract / Description: Hydrogen peroxide and chlorine detection is critical for many biological and environmental applications. Hydrogen peroxide plays important roles in a variety of fields including plant physiology, medical, environmental and biochemical applications. Its role in plant defense and signal transduction, diseases such as Parkinson's and Alzhemier's, industrial processes such as disinfection and wastewater treatment and biochemical enzymatic reactions is critical. Given the gamut of areas that...
Show moreHydrogen peroxide and chlorine detection is critical for many biological and environmental applications. Hydrogen peroxide plays important roles in a variety of fields including plant physiology, medical, environmental and biochemical applications. Its role in plant defense and signal transduction, diseases such as Parkinson's and Alzhemier's, industrial processes such as disinfection and wastewater treatment and biochemical enzymatic reactions is critical. Given the gamut of areas that hydrogen peroxide is a key component of; its detection assumes great importance. Similarly chlorine has long been used as a disinfectant for making drinking water safe, but excessive chlorination is an environmental and health hazard in itself. In this work, micromachining techniques have been used to design, fabricate and test electrochemical sensors and microneedle structure that can be integrated for detection of hydrogen peroxide and free chlorine. A novel nanomaterial has been integrated with the hydrogen peroxide microsensor, which greatly increases the sensor lifetime and robustness. Miniaturization, low detection limits, high sensitivity and selectivity, as well as ease of fabrication are some of the other advantages of this work.
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Date Issued: 2005
Identifier: CFE0000895, ucf:46627
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000895

Title: MAGNETICALLY DEFLECTABLE MEMS ACTUATORS FOR OPTICAL SENSING APPLICATIONS.
Creator: Montgomery, Matthew, Cho, Hyoung-Jin, University of Central Florida
Abstract / Description: In this work, new small deflection magnetic actuators have been proposed, designed, and tested for applications in Surface Enhanced Raman Scattering optical sensors. Despite the fact that SERS sensors have been shown to increase Raman over ten orders of magnitude for molecular detection, several technological challenges have prevented the design of practical sensors, such as making SERS sensors that can efficiently detect a wide variety of molecules. Since the optimum signal-to-noise in SERS...
Show moreIn this work, new small deflection magnetic actuators have been proposed, designed, and tested for applications in Surface Enhanced Raman Scattering optical sensors. Despite the fact that SERS sensors have been shown to increase Raman over ten orders of magnitude for molecular detection, several technological challenges have prevented the design of practical sensors, such as making SERS sensors that can efficiently detect a wide variety of molecules. Since the optimum signal-to-noise in SERS occurs at different excitation wavelengths for different molecules, individual metal nanostructures need to be designed and fabricated for each independent chemical species. One possible solution to this problem is to tune the plasmon resonance frequency of the metal nanoparticles to eliminate the need for individually optimized particles. In order to achieve a tunable local dielectric environment, and thus allow for control over the resonance frequency of metal nanoparticles, a new SERS sensor geometry is proposed and a large deflection magnetic actuator is fabricated and tested as a starting point for the design of a small deflection magnetic actuator. Using the newly developed SERS geometry and the optimized fabrication processing techniques, two small deflection magnetic actuator beam structures were designed, fabricated, and tested. These devices utilizes an off-chip electromagnet source able to produce a magnetic force of approximately 14 uN on the on-chip nickel film generating deflections up to 139 nm for the straight beam device and 164 nm for the curved beam device. In the process of characterizing the newly developed small deflection magnetic actuator, an integrated magnetic actuator with electrostatic restoration geometry was conceived. This device was designed to meet the specifications of the small deflection magnetic actuator as well as eliminate the need of an off-chip magnetic source and fully integrate the process atop the metal nanoparticle arrays. Using adhesive iron based magnetic strips as the magnetic drive source, circular NiFe beams with 1, 2, 3, and 4 mm diameters were designed and simulated. Calculations predicted maximum achievable actuation of up to 2.5 um. Processing steps were laid out for a set of integrated devices as a possible predecessor to the newly designed small deflection magnetic actuator.
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Date Issued: 2009
Identifier: CFE0002823, ucf:48057
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002823

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.
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Date Issued: 2008
Identifier: CFE0002368, ucf:47786
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002368

Title: APPLICATION OF POLYELECTROLYTE MULTILAYERS FOR PHOTOLITHOGRAPHIC PATTERNING OF DIVERSE MAMMALIAN CELL TYPES IN SERUM FREE MEDIUM.
Creator: Dhir, Vipra, Cho, Hyoung Jin, University of Central Florida
Abstract / Description: Integration of living cells with novel microdevices requires the development of innovative technologies for manipulating cells. Chemical surface patterning has been proven as an effective method to control the attachment and growth of diverse cell populations. Patterning polyelectrolyte multilayers through the combination of layer-by-layer self-assembly technique and photolithography offers a simple, versatile and silicon compatible approach that overcomes chemical surface patterning...
Show moreIntegration of living cells with novel microdevices requires the development of innovative technologies for manipulating cells. Chemical surface patterning has been proven as an effective method to control the attachment and growth of diverse cell populations. Patterning polyelectrolyte multilayers through the combination of layer-by-layer self-assembly technique and photolithography offers a simple, versatile and silicon compatible approach that overcomes chemical surface patterning limitations, such as short-term stability and low protein adsorption resistance. In this study, direct photolithographic patterning of PAA/PAAm and PAA/PAH polyelectrolyte multilayers was developed to pattern mammalian neuronal, skeletal and cardiac muscle cells. For all studied cell types, PAA/PAAm multilayers behaved as a negative surface, completely preventing cell attachment. In contrast, PAA/PAH multilayers have shown a cell-selective behavior, promoting the attachment and growth of neuronal cells (embryonic rat hippocampal and NG108-15 cells) to a greater extent, while providing a little attachment for neonatal rat cardiac and skeletal muscle cells (C2C12 cell line). PAA/PAAm multilayer cellular patterns have also shown a remarkable protein adsorption resistance. Protein adsorption protocols commonly used for surface treatment in cell culture did not compromise the cell attachment inhibiting feature of the PAA/PAAm multilayer patterns. The combination of polyelectrolyte multilayer patterns with different adsorbed proteins could expand the applicability of this technology to cell types that require specific proteins either on the surface or in the medium for attachment or differentiation, and could not be patterned using the traditional methods.
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Date Issued: 2008
Identifier: CFE0002357, ucf:47783
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002357

Title: Electrode Integration of Nanostructured Metal and Metal Oxide Materials Based on in-situ Growth Methods for Environmental Sensors.
Creator: Wang, Xiaochen, Cho, Hyoung Jin, Fang, Jiyu, Chen, Quanfang, Lee, Woo Hyoung, University of Central Florida
Abstract / Description: In the past decades, increased human population and activities have introduced a large amount of pollutants into the environment. Various types of conventional analytical instruments were used for monitoring the emitted chemicals with low detection limit, high accuracy, and discrimination power. However, many of these methods are laboratory-based owing to sample collection, transportation, extraction, and purification steps. To make real-time on-site monitoring possible, miniaturized sensors...
Show moreIn the past decades, increased human population and activities have introduced a large amount of pollutants into the environment. Various types of conventional analytical instruments were used for monitoring the emitted chemicals with low detection limit, high accuracy, and discrimination power. However, many of these methods are laboratory-based owing to sample collection, transportation, extraction, and purification steps. To make real-time on-site monitoring possible, miniaturized sensors with various integrated elements were developed. One of the most well-known strategies is to utilize nanostructured materials with enhanced sensing properties for those devices. For a majority of the current state of art devices, the synthesis of nanostructured materials and device integration are done separately, that is, (")synthesis first and then integration(") approach which involves two separate process steps. However, this approach comes with some disadvantages such as misalignment, contamination, as well as disconnection between nanomaterials and electrodes.To overcome the aforementioned technical challenge, several synthesis methods were developed and validated for in-situ integration of nanostructured metal and metal oxide materials for environmental sensors in this work. The electroplating technique combined with photolithography was used to make the predefined metal electrodes. Then, with subsequent post-treatments, nanostructured metals and metal oxides could be produced in-situ and directly integrated in the electrodes without any extra transfer process steps.In the process of developing a phosphate sensor, nanofibrous Co electrodes were fabricated by pulsed electroplating of Co-Cu alloy and dealloying the Cu component. A linear potentiometric response to phosphate in the 10-5 to 10-2 M concentration range was obtained which validated the sensor's function. A mechanism based on mixed potential response was proposed to elucidate the Co electrode behavior in aqueous solutions with varying pH conditions and optimum pH ranges for working devices were proposed.In addition to the alloying and dealloying method, the template assisted electroplating method was also investigated. A nanoporous Co-Cu electrode fabricated by electroplating through a sacrificial glass fiber template was obtained. A linear amperometric response to phosphate with suppressed oxygen interference was achieved in a 10-5 to 10-2 M concentration range of phosphate. An analysis of the cyclic voltammetry characterization results provided a direction for further exploring an optimized electrode polarization potential range for suppressing oxygen interference while maintaining a good sensitivity to phosphate. Based on this result, we improved the fabrication process with another template: in-situ hydrothermally grown ZnO nanoflakes on the electrode surface, as a template for uniform nanostructured Co electroplating. The cyclic voltammetry characterization of the fabricated electrode showed an amperometric response in the range of 10-6 to 10-2 M of phosphate where the limit of detection (LOD) was enhanced compared with the previous work.For the flammable gas sensor development, the in-situ oxidation of Cu was utilized to form nanowires for sensing electrode fabrication. Multiple CuO nanowires were synthesized in-situ on the electroplated interdigitated Cu electrodes on a hotplate at 500 ? in air. The nanowires were successfully integrated as a sensing element into the device, forming bridges between two electrodes. The sensor's behavior was characterized by a current-voltage measurement. Simple processing parameters could be utilized for controlling the electrode morphologies and determining the characteristics of contacts - Schottky or Ohmic - at the electrode interface. A hypothesis was proposed to explain the transition phenomenon between Schottky and Ohmic contact modes, providing an important baseline for future device design and fabrication. Finally, the fabricated sensor was tested for a flammable gas detection using saturated ethanol vapor at room temperature, which implicates a low power consumption gas sensor without elevating the sensor temperature unlike traditional gas sensors.
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Date Issued: 2017
Identifier: CFE0007139, ucf:52312
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007139

Title: Electroplated micro- and nanoscale structures for emitters and sensors.
Creator: Wang, Xiaochen, Cho, Hyoung, Fang, Jiyu, Chen, Quanfang, Lee, Woo Hyoung, University of Central Florida
Abstract / Description: In the electroplating process, dissolved metal cations are reduced by electrical current to a form a coherent metal coating on an electrode. Therefore, electroplating is primarily applied to modify the surface properties of an object (e.g. abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities, etc.), but also be applied to build up high aspect ratio structures on undersized parts or to form devices by electroforming.Compared with other common MEMS ...
Show moreIn the electroplating process, dissolved metal cations are reduced by electrical current to a form a coherent metal coating on an electrode. Therefore, electroplating is primarily applied to modify the surface properties of an object (e.g. abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities, etc.), but also be applied to build up high aspect ratio structures on undersized parts or to form devices by electroforming.Compared with other common MEMS (microelectromechanical systems) metal device fabrication techniques, such as vapor depositions, electroplating has several outstanding advantages. First, the fabrication process is cost-efficient because electroplating process can be set up easily without complex and expensive facilities. Second, the fabrication condition of electroplating is less demanding and does not require high temperature or low pressure. Furthermore, the process is applicable to making various features consisting of nanometer to millimeter scale particles, wires, and films. Thus, in this thesis, based on the design requirements of electrospray emitters and environmental sensors, the electroplating method was chosen to fabricate micro- and nanoscale structures for such applications.Electrospray is an atomization technique by which an electrically conductive liquid through a small capillary is charged with high voltage (kV) and ejected to a ground electrode. To minimize the electric field edge effect of the emitter nozzles to get even electro-hydrodynamic pulling force on the liquid among the nozzles and minimize variation from one emitter to another, the device needs to have the viscous pressure drop across each nozzle dominant over the electro-hydrodynamic pulling force. Therefore, embedded structures that can create high flow impedance are desirable to achieve uniform feeding of low flow rate of liquid to each emitter.We designed and fabricated in-plane metallic electrospray devices with an embedded array of micropillars within a microchannel by photolithography and electroplating. The novelty of the proposed research lies in its embedded flow restriction structure, scalability, and ease of fabrication. The formation of jets as well as the flexing capability of the emitter was achieved. The other application of electroplating was demonstrated in the fabrication of environmental sensors. Utilizing a pulsed electroplating method, Co-Cu metal alloy films were prepared and Cu was selectively etched to fabricate nanoporous electrodes which could be used to measure both absolute levels and changes of phosphate concentration in aqueous environments. The formation of cobalt phosphate compound could be used for the detection. The increased surface area and relatively simple fabrication protocols make the proposed method attractive and promising for many environmental sensing applications.
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Date Issued: 2014
Identifier: CFE0005274, ucf:50548
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005274

Title: Vision-Based Testbeds for Control System Applicaitons.
Creator: Sivilli, Robert, Xu, Yunjun, Gou, Jihua, Cho, Hyoung, Pham, Khanh, University of Central Florida
Abstract / Description: In the field of control systems, testbeds are a pivotal step in the validation and improvement of new algorithms for different applications. They provide a safe, controlled environment typically having a significantly lower cost of failure than the final application. Vision systems provide nonintrusive methods of measurement that can be easily implemented for various setups and applications. This work presents methods for modeling, removing distortion, calibrating, and rectifying single and...
Show moreIn the field of control systems, testbeds are a pivotal step in the validation and improvement of new algorithms for different applications. They provide a safe, controlled environment typically having a significantly lower cost of failure than the final application. Vision systems provide nonintrusive methods of measurement that can be easily implemented for various setups and applications. This work presents methods for modeling, removing distortion, calibrating, and rectifying single and two camera systems, as well as, two very different applications of vision-based control system testbeds: deflection control of shape memory polymers and trajectory planning for mobile robots. First, a testbed for the modeling and control of shape memory polymers (SMP) is designed. Red-green-blue (RGB) thresholding is used to assist in the webcam-based, 3D reconstruction of points of interest. A PID based controller is designed and shown to work with SMP samples, while state space models were identified from step input responses. Models were used to develop a linear quadratic regulator that is shown to work in simulation. Also, a simple to use graphical interface is designed for fast and simple testing of a series of samples. Second, a robot testbed is designed to test new trajectory planning algorithms. A template-based predictive search algorithm is investigated to process the images obtained through a low-cost webcam vision system, which is used to monitor the testbed environment. Also a user-friendly graphical interface is developed such that the functionalities of the webcam, robots, and optimizations are automated. The testbeds are used to demonstrate a wavefront-enhanced, B-spline augmented virtual motion camouflage algorithm for single or multiple robots to navigate through an obstacle dense and changing environment, while considering inter-vehicle conflicts, obstacle avoidance, nonlinear dynamics, and different constraints. In addition, it is expected that this testbed can be used to test different vehicle motion planning and control algorithms.
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Date Issued: 2012
Identifier: CFE0004601, ucf:49187
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004601

Title: Study of High Efficiency Micro Thermoelectric Energy Harvesters.
Creator: Pedrosa, Steven, Chen, Quanfang, Cho, Hyoung, Xu, Yunjun, University of Central Florida
Abstract / Description: Thermal energy sources, including waste heat and thermal radiation from the sun, are important renewable energy resources. Thermal energy can be converted into electricity by thermoelectric phenomena; the thermoelectric phenomena can also be operated in reverse when provided an electric current, producing a temperature gradient across the device. Thermoelectric devices are scalable, renewable, and cost effective products that offer capabilities to harness waste heat or environmental heat...
Show moreThermal energy sources, including waste heat and thermal radiation from the sun, are important renewable energy resources. Thermal energy can be converted into electricity by thermoelectric phenomena; the thermoelectric phenomena can also be operated in reverse when provided an electric current, producing a temperature gradient across the device. Thermoelectric devices are scalable, renewable, and cost effective products that offer capabilities to harness waste heat or environmental heat sources, and convert the captured heat into usable electricity. The operating principle of a thermoelectric device requires that a temperature gradient be present across the device, which induces the flow of electrons from the hot side of the device to the cold side. Thermoelectric devices are currently hampered by the low conversion efficiencies and strict operating temperatures for certain materials. This study investigates the main factors affecting efficiencies of thermoelectric devices as energy harvesters and aims to optimize the devices for maximum efficiency and lower costs by using microfabrication processes and self-assembled materials for complete thermoelectric modules (TEMs). By first establishing operating conditions and a desired mode of operation, optimization equations have been established to determine device dimensions and performance parameters. Compact integration realized by microfabrication technologies that allow for multiple output voltages from a single chip was also investigated. Additionally, cost savings were found by reducing the number of fabrication processing steps and eliminating the need for precious metals during fabrication. The optimized design proposed in this study utilizes copper electrodes and requires fewer applications of photoresist than previous proposed designs. In fabrication of thin film based micro devices, the film quality and the composition of the film are essential elements for producing TEMs with desired efficiencies. Although Bi2Te3 has been investigated as thermoelectric material, this study determined that there was a possibility that both N-type and P-Type Bi2Te3 could be created from a single electrolyte solution by controlling the amount of Te present in the film. Films were produced with both AC and DC signals and varied composition of Te at.% of Bi2Te3 was achieved by controlling the average current density during electrochemical deposition. A linear relationship was established between the average current density and the resultant Te content. SEM and EDS were used to characterize the morphology and the composition of the thin films created. With the fabricated thermoelectric materials, analytical models could be developed using known material properties of thermoelectric films with a given Te content. The analytical results obtained by the developed optimization equations were comparable with the FEA models produced by using COMSOL, a multiphysics program with powerful solving algorithms that was used to evaluate designs. Further improvements to device performance can be achieved by designing a segmented thermoelectric device with multiple layers of thermoelectric material to allow the device to operate across a larger temperature gradient.
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Date Issued: 2011
Identifier: CFE0004486, ucf:49318
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004486

Title: Generation and printing of strictly monodisperse droplets.
Creator: Duan, Hongxu, Deng, Weiwei, An, Linan, Cho, Hyoung, University of Central Florida
Abstract / Description: Highly monodisperse droplets are attracting great attention both in many research areas, such as aerosol science, combustion, and Nano-manufacturing. This thesis invents a novel aerosol generator: (")Periodic Electro Hydro-dynamic Chopper(") termed as (")PEHD chopper("), and develops a new method to directly print micro-patterns with monodisperse droplets. The principle of the PEHD chopper is to use the fringe electric field of a capacitor to introduce controlled perturbation on a liquid jet...
Show moreHighly monodisperse droplets are attracting great attention both in many research areas, such as aerosol science, combustion, and Nano-manufacturing. This thesis invents a novel aerosol generator: (")Periodic Electro Hydro-dynamic Chopper(") termed as (")PEHD chopper("), and develops a new method to directly print micro-patterns with monodisperse droplets. The principle of the PEHD chopper is to use the fringe electric field of a capacitor to introduce controlled perturbation on a liquid jet.We first derived the governing equations for a circular inviscid liquid jet under transverse electric fields. The electric fields were obtained through numerical simulation. Then we used a high speed camera (up to one million frames per second) to visualize the jet break-up as well as the droplets' size and shape.The experiments show that the PEHD chopper can effectively (")chop(") a neutral micro-jet and generate highly monodisperse micro-droplets, which diameter range from 100 (&)#181;m to 500 (&)#181;m. To reduce the droplet size, PEHD chopper with a butterfly design is applied on a typical single electrospray. In this configuration, the jet swings at long wavelengths (?(>)?R), where ?R is the Rayleigh wave length, but breaks up into highly monodisperse droplets near 2?R and ?R without satellite droplets. The butterfly configuration combined with electrified jet expands the diameter range into 20 (&)#181;m to 100 (&)#181;m.Finally, we demonstrate the electrospray printing of Polymer Derived Ceramics (PDC) for sensor applications in harsh environment. A modified single ES with an additional driving electric field is used to directly print PDC precursor without mask, we achieved 1D feature as narrow as 35 (&)#181;m and a micro pentagram pattern. Moreover, after pyrolysis of PDC at 1100 (&)deg;C in nitrogen, amorphous alloys of silicon, carbon and nitrogen (SiCN) are obtained. The samples exhibit excellent good integrity and adhesion to the substrate.
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Date Issued: 2013
Identifier: CFE0005094, ucf:50720
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005094

Title: Fabrication and Investigation of an enzyme-free, Nanoparticle-based Biosensor for Hydrogen Peroxide determination.
Creator: Neal, Craig, Seal, Sudipta, Cho, Hyoung Jin, Florczyk, Stephen, University of Central Florida
Abstract / Description: Electrochemical biosensors often employ enzymes as detection elements. These sensors are highly selective towards target analytes, however the scope of their application is limited by the poor stability of the enzyme. In this study, multi-valent inorganic cerium oxide nanoparticles were used as detection elements for the analysis of hydrogen peroxide. The electrochemical response of the cerium oxide towards hydrogen peroxide analyte is defined through cyclic voltammetry and chronoamperometry....
Show moreElectrochemical biosensors often employ enzymes as detection elements. These sensors are highly selective towards target analytes, however the scope of their application is limited by the poor stability of the enzyme. In this study, multi-valent inorganic cerium oxide nanoparticles were used as detection elements for the analysis of hydrogen peroxide. The electrochemical response of the cerium oxide towards hydrogen peroxide analyte is defined through cyclic voltammetry and chronoamperometry. This response was found to be dependent on nanoparticle Ce3+:Ce4+ redox state ratio and this property is exploited to fabricate a biosensor. As produced, the biosensor demonstrated sensitivity at picomolar analyte concentrations. Further, the sensitivity of the electrode is stable across a range of temperatures and pH's which inhibit the function of standard enzyme-based sensors. Additionally, the produced sensor retained function in sheep serum demonstrating the high selectivity and robustness of the sensor.
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Date Issued: 2016
Identifier: CFE0006362, ucf:51540
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006362

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.
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Date Issued: 2011
Identifier: CFE0004474, ucf:49313
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004474

Title: Virtual Motion Camouflage Based Nonlinear Constrained Optimal Trajectory Design Method.
Creator: Basset, Gareth, Xu, Yunjun, Kassab, Alain, Lin, Kuo-Chi, Cho, Hyoung, Qu, Zhihua, University of Central Florida
Abstract / Description: Nonlinear constrained optimal trajectory control is an important and fundamental area of research that continues to advance in numerous fields. Many attempts have been made to present new methods that can solve for optimal trajectories more efficiently or to improve the overall performance of existing techniques. This research presents a recently developed bio-inspired method called the Virtual Motion Camouflage (VMC) method that offers a means of quickly finding, within a defined but varying...
Show moreNonlinear constrained optimal trajectory control is an important and fundamental area of research that continues to advance in numerous fields. Many attempts have been made to present new methods that can solve for optimal trajectories more efficiently or to improve the overall performance of existing techniques. This research presents a recently developed bio-inspired method called the Virtual Motion Camouflage (VMC) method that offers a means of quickly finding, within a defined but varying search space, the optimal trajectory that is equal or close to the optimal solution.The research starts with the polynomial-based VMC method, which works within a search space that is defined by a selected and fixed polynomial type virtual prey motion. Next will be presented a means of improving the solution's optimality by using a sequential based form of VMC, where the search space is adjusted by adjusting the polynomial prey trajectory after a solution is obtained. After the search space is adjusted, an optimization is performed in the new search space to find a solution closer to the global space optimal solution, and further adjustments are made as desired. Finally, a B-spline augmented VMC method is presented, in which a B-spline curve represents the prey motion and will allow the search space to be optimized together with the solution trajectory.It is shown that (1) the polynomial based VMC method will significantly reduce the overall problem dimension, which in practice will significantly reduce the computational cost associated with solving nonlinear constrained optimal trajectory problems; (2) the sequential VMC method will improve the solution optimality by sequentially refining certain parameters, such as the prey motion; and (3) the B-spline augmented VMC method will improve the solution optimality without sacrificing the CPU time much as compared with the polynomial based approach. Several simulation scenarios, including the Breakwell problem, the phantom track problem, the minimum-time mobile robot obstacle avoidance problem, and the Snell's river problem are simulated to demonstrate the capabilities of the various forms of the VMC algorithm. The capabilities of the B-spline augmented VMC method are also shown in a hardware demonstration using a mobile robot obstacle avoidance testbed.
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Date Issued: 2012
Identifier: CFE0004298, ucf:49493
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004298

Title: Understanding the Role of Defects in the Radiation Response of Nanoceria.
Creator: Kumar, Amit, Seal, Sudipta, Heinrich, Helge, Cho, Hyoung, Leuenberger, Michael, Zhai, Lei, Devanathan, Ram, University of Central Florida
Abstract / Description: Nanoscale cerium oxide (nanoceria) have shown to possess redox active property , and has been widely studied for potential use in catalysis, chemical-mechanical planarization, bio-medical and solid oxide fuel cell (SOFC), etc. The redox state of nanoceria can be tuned by controlling the defects within the lattice and thus its physical and chemical properties. Perfect ceria lattice has fluorite structure and the research in last decade has shown that oxide and mixed oxide systems with...
Show moreNanoscale cerium oxide (nanoceria) have shown to possess redox active property , and has been widely studied for potential use in catalysis, chemical-mechanical planarization, bio-medical and solid oxide fuel cell (SOFC), etc. The redox state of nanoceria can be tuned by controlling the defects within the lattice and thus its physical and chemical properties. Perfect ceria lattice has fluorite structure and the research in last decade has shown that oxide and mixed oxide systems with pyrochlore and fluorite have better structural stability under high energy radiation. However, the current literature shows a limited number of studies on the effect of high energy radiation on nanoceria. This dissertation aims at understanding the phenomena occurring on irradiation of nanoceria lattice through experiments and atomistic simulation.At first, research was conducted to show the ability to control the defects in nanoceria lattice and understand the effect in tailoring its properties. The defect state of nanoceria was controlled by lower valence state rare earth dopant europium. Extensive materials characterization was done using high resolution transmission electron microscopy (HRTEM), UV-Visible spectroscopy (UV-Vis), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy to understand the effect of dopant chemistry in modifying the chemical state of nanoceria. The defects originating in the lattice and redox state was quantified with increasing dopant concentration. The photoluminescence property of the control and doped nanoceria were evaluated with respect to its defect state. It was observed that defect plays an important role in modifying the photoluminescence property and that it can be tailored in a wide range to control the optical properties of nanoceria.Having seen the importance of defects in controlling the properties of nanoceria, further experiments were conducted to understand the effect of radiation in cerium oxide thin films of different crystallinity. The cerium oxide thin films were synthesized using oxygen plasma assisted molecular beam epitaxy (OPA-MBE) growth. The thin films were exposed to high energy radiation over a wide range of fluence (1013 to 1017 He+ ions/cm3). The current literature does not report the radiation effect in nanoceria in this wide range and upto this high fluence. The chemical state of the thin film was studied using in-situ XPS for each dose of radiation. It was found that radiation induced defects within both the ceria thin films and the valence state deviated further towards non-stoichiometry with radiation. The experimental results from cerium oxide thin film irradiation were studied in the light of simulation. Classical molecular dynamics and Monte Carlo simulation were used for designing the model ceria nanoparticle and studying the interaction of the lattice model with radiation. Electronic and nuclear stopping at the end of the range were modeled in ceria lattice using classical molecular dynamics to simulate the effect of radiation. It was seen that displacement damage was the controlling factor in defect production in ceria lattice. The simulation results suggested that nanosized cerium oxide has structural stability under radiation and encounters radiation damage due to the mixed valence states. A portion of the study will focus on observing the lattice stability of cerium with increasing concentration of the lower valence (Ce3+) within the lattice. With this current theoretical understanding of the role of redox state and defects during irradiation, the surfaces and bulk of nanoceria can be tailored for radiation stable structural applications.
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Date Issued: 2012
Identifier: CFE0004396, ucf:49375
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004396

Title: BEAM-STEERABLE AND RECONFIGURABLE REFLECTARRAY ANTENNAS FOR HIGH GAIN SPACE APPLICATIONS.
Creator: Karnati, Kalyan, Gong, Xun, Wahid, Parveen, Jones, W Linwood, Wu, Thomas, Cho, Hyoung Jin, University of Central Florida
Abstract / Description: Reflectarray antennas uniquely combine the advantages of parabolic reflectors and phased array antennas. Comprised of planar structures similar to phased arrays and utilizing quasi-optical excitation similar to parabolic reflectors, reflectarray antennas provide beam steering without the need of complex and lossy feed networks. Chapter 1 discusses the basic theory of reflectarray and its design. A brief summary of previous work and current research status is also presented. The inherent...
Show moreReflectarray antennas uniquely combine the advantages of parabolic reflectors and phased array antennas. Comprised of planar structures similar to phased arrays and utilizing quasi-optical excitation similar to parabolic reflectors, reflectarray antennas provide beam steering without the need of complex and lossy feed networks. Chapter 1 discusses the basic theory of reflectarray and its design. A brief summary of previous work and current research status is also presented. The inherent advantages and drawbacks of the reflectarray are discussed.In chapter 2, a novel theoretical approach to extract the reflection coefficient of reflectarray unit cells is developed. The approach is applied to single-resonance unit cell elements under normal and waveguide incidences. The developed theory is also utilized to understand the difference between the TEM and TE10 mode of excitation. Using this theory, effects of different physical parameters on reflection properties of unit cells are studied without the need of full-wave simulations. Detailed analysis is performed for Ka-band reflectarray unit cells and verified by full-wave simulations. In addition, an approach to extract the Q factors using full-wave simulations is also presented. Lastly, a detailed study on the effects of inter-element spacing is discussed.Q factor theory discussed in chapter 2 is extended to account for the varying incidence angles and polarizations in chapter 3 utilizing Floquet modes. Emphasis is laid on elements located on planes where extremities in performance tend to occur. The antenna element properties are assessed in terms of maximum reflection loss and slope of the reflection phase. A thorough analysis is performed at Ka band and the results obtained are verified using full-wave simulations. Reflection coefficients over a 749-element reflectarray aperture for a broadside radiation pattern are presented for a couple of cases and the effects of coupling conditions in conjunction with incidence angles are demonstrated. The presented theory provides explicit physical intuition and guidelines for efficient and accurate reflectarray design.In chapter 4, tunable reflectarray elements capacitively loaded with Barium Strontium Titanate (BST) thin film are shown. The effects of substrate thickness, operating frequency and deposition pressure are shown utilizing coupling conditions and the performance is optimized. To ensure minimum affects from biasing, optimized biasing schemes are discussed. The proposed unit cells are fabricated and measured, demonstrating the reconfigurability by varying the applied E-field. To demonstrate the concept, a 45 element array is also designed and fabricated. Using anechoic chamber measurements, far-field patterns are obtained and a beam scan up to 25o is shown on the E-plane.Overall, novel theoretical approaches to analyze the reflection properties of the reflectarray elements using Q factors are developed. The proposed theoretical models provide valuable physical insight utilizing coupling conditions and aid in efficient reflectarray design. In addition, for the first time a continuously tunable reflectarray operating at Ka-band is presented using BST technology. Due to monolithic integration, the technique can be extended to higher frequencies such as V-band and above.
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Date Issued: 2015
Identifier: CFE0006040, ucf:50963
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006040

Title: Performance optimization of lateral-mode thin-film piezoelectric-on-substrate resonant systems.
Creator: Fatemi, Hedy, Abdolvand, Reza, Sundaram, Kalpathy, Malocha, Donald, Gong, Xun, Cho, Hyoung Jin, University of Central Florida
Abstract / Description: The main focus of this dissertation is to characterize and improve the performance of thin-film piezoelectric-on-substrate (TPoS) lateral-mode resonators and filters. TPoS is a class of piezoelectric MEMS devices which benefits from the high coupling coefficient of the piezoelectric transduction mechanism while taking advantage of superior acoustic properties of a substrate. The use of lateral-mode TPoS designs allows for fabrication of dispersed-frequency filters on a single substrate, thus...
Show moreThe main focus of this dissertation is to characterize and improve the performance of thin-film piezoelectric-on-substrate (TPoS) lateral-mode resonators and filters. TPoS is a class of piezoelectric MEMS devices which benefits from the high coupling coefficient of the piezoelectric transduction mechanism while taking advantage of superior acoustic properties of a substrate. The use of lateral-mode TPoS designs allows for fabrication of dispersed-frequency filters on a single substrate, thus significantly reducing the size and manufacturing cost of devices. TPoS filters also offer a lower temperature coefficient of frequency, and better power handling capability compared to rival technologies all in a very small footprint.Design and fabrication process of the TPoS devices is discussed. Both silicon and diamond substrates are utilized for fabrication of TPoS devices and results are compared. Specifically, the superior acoustic properties of nanocrystalline diamond in scaling the frequency and energy density of the resonators is highlighted in comparison with silicon. The performance of TPoS devices in a variety of applications is reported. These applications include lateral-mode TPoS filters with record low IL values (as low as 2dB) and fractional bandwidth up to 1%, impedance transformers, very low phase noise oscillators, and passive wireless temperature sensors.
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Date Issued: 2015
Identifier: CFE0005945, ucf:50805
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005945

Title: Development of enzyme-free hydrogen peroxide biosensor using cerium oxide and mechanistic study using in-situ spectro-electrochemistry.
Creator: Saraf, Shashank, Seal, Sudipta, Cho, Hyoung Jin, Zhai, Lei, Heinrich, Helge, Harper, James, University of Central Florida
Abstract / Description: During recent development, it has been demonstrated that cerium oxide nanoparticles (CNPs) have exhibited catalytic activity which mimics naturally existing enzymes such as superoxide dismutase (SOD) and catalase. The underlying mechanism is attributed to the modulation of oxygen vacancies on CNPs lattice by dynamic switching of the oxidation states between Ce3+ and Ce4+ due to the electron transfer resulting from the redox reaction between CNPs and reactive oxygen species such as hydrogen...
Show moreDuring recent development, it has been demonstrated that cerium oxide nanoparticles (CNPs) have exhibited catalytic activity which mimics naturally existing enzymes such as superoxide dismutase (SOD) and catalase. The underlying mechanism is attributed to the modulation of oxygen vacancies on CNPs lattice by dynamic switching of the oxidation states between Ce3+ and Ce4+ due to the electron transfer resulting from the redox reaction between CNPs and reactive oxygen species such as hydrogen peroxide (H2O2). Thereby the redox potential of CNPs is dependent on the surface chemistry i.e. the surface concentration of Ce3+ and Ce4+ Currently, the ratio of Ce3+/ Ce4+ in CNPs is characterized ex-situ using XPS or TEM which involves sample drying and exposure to high energy X-rays and electron beam, respectively. Sample drying and high energy beam exposure could lead to sample deterioration. The goal of the study is to explore a technique to characterize CNPs in-situ and identify the surface chemistry of CNPs. The in-situ investigation of CNPs was carried using spectroelectrochemistry wherein the electrochemical and optical measurements are carried out simultaneously. Detailed optical characterization of two different CNPs having different catalytic activity were carried under oxidation and reduction environments. Analysis of spectra revealed widely different redox potential for CNPs which was a function of pH and composition of buffer solution. In second part of dissertation a suitable surface chemistry of CNPs is investigated to replace the enzyme in biosensor assembly to allow amperometric detection of H2O2 in physiological conditions. Upon electrochemical investigation of the physio-chemical properties of CNPs, it was found that CNPs having higher surface concentration of Ce4+ as compared to Ce3+ oxidation states, demonstrated increased catalytic activity towards H2O2. The addition of CNPs resulted in 5 orders of increment in amperometric current with a response time of 400 msec towards detection of H2O2 and exhibited excellent selectivity in presence of interfering species. Additionally, cerium oxide was successfully integrated into the biosensor assembly through the anodic electrodeposition, which allowed the transfer of electron generated from the CNPs in the redox reaction to the electrode and demonstrated successful sensing of H2O2. Furthermore, to achieve detection of H2O2 in physiological conditions, CNPs were integrated with nanoporous gold (NPG) which exhibited anti-biofouling properties. The anti-biofouling property of NPG was investigated using electrochemical techniques and showed excellent signal retention in physiological concentration of albumin proteins. The novel study targets at developing robust enzyme free biosensor by integrating the detection ability of CNPs with the anti-biofouling activity of NPG based electrode.
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Date Issued: 2016
Identifier: CFE0006498, ucf:51404
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006498

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.
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Date Issued: 2017
Identifier: CFE0006939, ucf:51664
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006939

Cerium oxide nanoparticles (2)	+ -
MEMS (2)	+ -
gas sensor (2)	+ -
microfluidics (2)	+ -
phosphate sensor (2)	+ -

2D materials (1)	+ -
Advancing and receding wetting-lines (1)	+ -
Amperometric (1)	+ -
Antennas (1)	+ -
Arrays (1)	+ -
Atomic layer deposition (1)	+ -
BST (1)	+ -
Bile acids (1)	+ -
Biofluids (1)	+ -
Biosensor (1)	+ -
COMSOL (1)	+ -
Cell encapsulation (1)	+ -
Ceria (1)	+ -
Cerium Oxide (1)	+ -
Cerium oxide (1)	+ -
Characterization (1)	+ -
Coupling conditions (1)	+ -
DRIE (1)	+ -
Defects (1)	+ -
Diamond (1)	+ -
Droplet (1)	+ -
Droplet manipulation (1)	+ -
Dynamic contact angle (1)	+ -
Electrochemical (1)	+ -
Electrochemical sensor (1)	+ -

University of Central Florida (26)	+ -
Cho, Hyoung Jin (14)	+ -
Cho, Hyoung (10)	+ -
Seal, Sudipta (5)	+ -
Zhai, Lei (5)	+ -

Chen, Quanfang (4)	+ -
Fang, Jiyu (3)	+ -
Heinrich, Helge (3)	+ -
Sundaram, Kalpathy (3)	+ -
Xu, Yunjun (3)	+ -
Abdolvand, Reza (2)	+ -
An, Linan (2)	+ -
Deng, Weiwei (2)	+ -
Gong, Xun (2)	+ -
Harper, James (2)	+ -
Kumar, Ranganathan (2)	+ -
Lee, Woo Hyoung (2)	+ -
Lin, Kuo-Chi (2)	+ -
Malocha, Donald (2)	+ -
Saraf, Shashank (2)	+ -
Wang, Xiaochen (2)	+ -
Yuan, Jiann-Shiun (2)	+ -
Basset, Gareth (1)	+ -
Behal, Aman (1)	+ -
Cho, Hyoung (Joe) (1)	+ -
Cho, Hyoung-Jin (1)	+ -
Chow, Louis (1)	+ -
Davanlou, Ashkan (1)	+ -
Deng, Jinan (1)	+ -
Devanathan, Ram (1)	+ -

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