Cancer is a major health issue that has been associated with over 80 million deaths worldwide in the last decade. Recently, significant improvements have been made in terms of treatment and diagnosis. However, despite these advancements there is still a demand for low-cost, high-accuracy, and easy-to-use technologies capable of classifying cells. Analysis of cell behavior in microfluidic deformability assays provides a label-free method of observing cell response to physical and chemical stimuli. This body of work shows advancements made toward reaching our goal of a robust and cost-effective biosensing device that allows for the identification of normal and cancer cells. These devices can also monitor cell responses to physical and chemical stimuli in the form of mechanical deformation and chemotherapeutic drugs, respectively. Our initial design was a microfluidic device that consisted of three channels with varying deformation and relaxation regions. Cell velocities from the deformations regions allowed us to distinguish between normal and cancer cells at the single-cell level. The next design used a singular deformation channel that was embedded with an array of electrodes in order to measure entry time, transit time and velocities as a single cell passes through the channel. These factors were found to reveal information about the biomechanical properties of single cells. Embedded electrodes were implemented in order to reduce post processing times of the data analysis and provide more insight into the bioelectrical information of cells. Finally, we report a microfluidic device with parallel deformation channels and a single electrode pair to improve throughput and automate data collection of deformability assays. This thesis demonstrates how microfluidic deformability assays, with and without embedded electrodes, show promising capabilities to classify different cells based on their biophysical traits which can be utilized as a valuable tool for testing responses to physical and chemical stimuli. / MS / Cancer is a worldwide health issue with approximately 1.7 million new cases each year in the United State alone. Although a great amount of research has been conducted in this field, the numerous uncertainties and heterogeneity among tumors, which is amplified by the large diversity between patients, has limit progress in both diagnostics and therapy. Traditionally, cancer studies have primarily focused on biological and chemical techniques. However, more recently, researchers have begun to leverage engineering techniques to acquire a new perspective on cancer to better understand the underlying biophysical attributes. Thus far, various engineering methodologies have produced meaningful results, but these techniques are costly and tend to be laborious. As a result, there is a need for low-cost, high-accuracy, and easy-to-use technologies to aid with cancer research, diagnostics, and treatment. An emerging field to alleviate these concerns is microfluidics, which is a science involving the flow of fluids in micro-scale channels. The field of microfluidics shows a great deal of promise for the development of clinically ready devices for analyzing cancer cells at both the population and single cell levels. Investigating the behavior of cancer cells at a single cell level can provide valuable information to help better understand the responsiveness of tumors to physical or chemical stimuli, such as chemotherapeutic drugs. This thesis reports multiple robust and cost-effective biomedical micro-devices that are used to analyze normal and cancerous cells. These devices consist of a microfluidic channel with sensors and are created using micro-fabrication techniques. The unique designs have enabled the evaluation of cells based on their mechanical and electrical properties. Specifically, the mechanical properties can be measured by forcing a cell into a microfluidic channel that is smaller than the diameter of the cell and recording its response to this physical stimulus. Electrical properties are measured simultaneously as the cells are probed for their mechanical properties. In general, the mechanical and electrical properties of cells can be altered when they undergo internal change (i.e. diseased cells) or experience external stimuli. Thus, these properties can be utilized as indicators of cancer progression and can be used to distinguish tumorigenic from non-tumorigenic cells. Data collection from these devices is automated, allowing for the rapid acquisition of mechanical and electrical properties of cells with minimal post-processing. Results from these devices have been promising in their ability to indicate significant differences among various normal and cancer populations based on their mechanical and electrical attributes.

Recent attempts to investigate living systems from a biophysical point of view has opened new windows for development of new diagnostic methods and therapies. Pulsed electric fields (PEFs) are a new class of therapies that take advantage of biophysical properties and have proven to be effective in drug delivery and treating several disorders including tumors. While animal models are commonly being used for development of new therapies, the high cost and complexity of these models along with the difficulties to control the electric field in the animal tissue are some of the obstacles toward the development of PEFs-based therapies. Microengineered models of organs or Organs-on-Chip have been recently introduced to overcome the hurdles of animal models and provide a flexible and cost-effective platform for early investigation of a variety of new therapies. In this study microfluidic platforms with integrated micro-sensors were designed, fabricated and employed to study the consequences of PEFs at the cellular level. These platforms were specifically used to study the effects of PEFs on the permeabilization of the blood-brain barrier for enhanced drug delivery to the brain. Different techniques such as fluorescent microscopy and electrical impedance spectroscopy were used to monitor the response of the cell monolayers under investigation. Irreversible electroporation is a new focal ablation therapy based on PEFs that has enabled ablation of tumors in a non-thermal, minimally invasive procedure. Despite promising achievements and treatment of more than 5500 human patients by this technique, real-time monitoring of the treatment progress in terms of the size of the ablated region is still needed. To address that necessity we have developed micro-sensor arrays that can be implemented on the ablation probe and give real-time feedback about the size of the ablated region by measuring the electrical impedance spectrum of the tissue. / Ph. D.

The purpose of this investigation was to determine the effect of premenstrual edema (water retention) on measurements of percent body fat (%BF) in ovulating women during the menstrual cycle utilizing bioelectrical impedance. Specifically, this study was designed to investigate the difference between bioelectrical impedance measurements of %BF recorded during day 1 of menses, day 7, day -1 midcycle, midcycle, day 21, and days -3, -2, and -1 premenses. Determinations of impedance were made in 26 regularly menstruating women aged 20.23±0.74 yr using an electrical impedance analyzer with a four-electrode arrangement that induces a painless signal ( 800 !microamps at 50 kHz) into the body. Internal consistency reliability estimates made approximately 5 min apart during each test day ranged from R = .96-.99 for the impedance measurements of %BF, and the stability reliability correlation coefficients ever the eight observation days ranged from r = .92-.97 for the impedance measurements of %BF. The reliability analyses indicated that %BF esitimated from bioelectrical impedance was measured reliably. Specific days of the menstrual cycle did not significantly affect impedance measurements of %BF. Analysis of variance with repeated measures also indicated that day during the menstrual cycle did not significantly affect weight (Wt), %BF, resistance (Re), or total body water (TBW) measurements. However, urine osmolality (Osm) and basal body temperature (BBT) were significantly affected across days of the menstrual cycle (p < .01). A dramatic decline in Osm was noted at midcycle followed by a rise which peaked at day -3 premenses. After day -3 premenses, Osm rapidly declined at menses. The dramatic decline in Osm at midcycle may reflect changes in urine concentration due to actions of elevated estrogen associated with ovulation. BBT dropped prior to midcycle and then began to rise until day -3 of the next menses and then it dropped slightly. The drop prior -co midcycle may be also reflected by changes in the hormonal concentration of estrogen. The biphasic BBT response was considered to be presumptive evidence that ovulation had occurred. A 2 x 2 factorial analysis of variance with repeated measures demonstrated that there was a significant interaction between cycle length and activity level on measurements of Wt, %BF, and BBT (p < .05). As light activity subjects with average cycle lengths became moderately active, their %BF decreased from 26.51±0.63% to 21.11±0.50% followed by a dramatic increase to 29.40±0.62% as they became highly active. On the otherhand, as light activity subjects with above average cycle lengths became more and more active, their %BF dropped drastically from 35.11±1.44% to 18.72±0. 75%. The data support the hypothesis that bioelectrical impedance measurements of %BF recorded during the normal menstrual cycle are not significantly different. However, a larger population is required to validate the applicability of these results. / M.S.

In this thesis a mathematical analysis is made of the input impedance to a cylinder antenna with an axial slot. It is excited by a parallel-wire line connected across the center of the slot. This causes standing waves along the slot. The analysis is then based on an analogy between the slot and a transmission line. Following this analogy equations for the transmission-line parameters are developed for the slotted cylinder. The slot distributed inductance and capacitance are determined by assuming an infinite slot length, while the conductance is obtained for a finite slot. The phase constant, which is contained in the expressions for the line parameters, is a function of the line parameters. Thus, a final answer requires the solution of simultaneous equations. This is done on a digital computer. This analysis applies to the case where the wavelength of excitation is of the same order of magnitude as the diameter of the cylinder. Possible frequencies for which this antenna might be used are in the microwave range. / Master of Science

Real-time structural integrity monitoring is a concept that is becoming a reality in the engineering community. It will soon be possible for a structure to warn the user when its own structural integrity has been altered. A qualitative impedance-based health monitoring technique, which can be implemented for real-time damage evaluation of complex structures, is investigated. The basic principle of the technique is to monitor the structure's mechanical impedance which will be changed with the presence of damage. The mechanical impedance variations are monitored by measuring the electrical impedance of a bonded piezoelectric actuator/sensor (PZT). This mechanical-electrical impedance relation is due to the electro-mechanical coupling property of piezoelectric materials. This health monitoring technique can be easily adapted to existing structures, since only a small non-intrusive PZT patch is needed. This impedance-based method operates at high frequencies (generally above 100kHz), which enables it to detect incipient type damage in a localized region. The localized sensing region offers the advantage of not being affected by nonnal operating conditions or by changing boundary conditions. In this thesis, a complete theoretical background on the impedance-based technique is derived. Then, the technique is applied successfully to a variety of case studies; such as composite patch repair, aircraft structures, precision parts, and civil infrastructure. By simplifying the impedance measurement interpretation through a simple scalar damage metric, the real-time implementation of the impedance-based technique has been proven feasible. / Master of Science

The work presented in this thesis was motivated by the need for an accurate modeling approach for the acoustic response in a non-rigid-wall enclosure. The acoustic response in any enclosure is determined by the boundary conditions at the interior surface of the enclosure walls, and the types of sources present. The analyses presented in this thesis assumed that the sources were either at the surface of the enclosure, or interior to the enclosure walls. Three different analytical modeling approaches were investigated and presented in this thesis for the acoustic response in a rectangular enclosure. A reference model assumed that the walls of the enclosure were rigid, corresponding to an infinite acoustic impedance boundary condition. The acoustic pressure response was expressed in terms of the characteristic rigid wall acoustic modes of the enclosure. The second modeling approach used a finite acoustic impedance boundary condition to model the influence of non-rigid walls on the acoustic response. The third modeling approach treated the vibration of the enclosure walls as additional sources which were constructed from the in vacuo structural modes of the enclosure. The acoustic pressure was expressed in terms of the rigid-wall acoustic modes. High-dimensional state variable and transfer function models are presented, along with discussions of their validity and performance as model parameters vary. The frequency response functions generated using these three models were compared to the actual acoustic frequency response function obtained experimentally for a non-rigid-wall, plexiglass enclosure. It was found that the finite impedance model generated an acoustic response which best matched that of the actual acoustic response in magnitude and frequency; however, further development of this model is needed to account for structural resonances of the enclosure. / Master of Science

In electric power systems, the existence of constant power loads such as output-regulated power converters may bring instability problem to AC or DC distributed systems. Impedance based stability criteria has been proven a good tool for small-signal stability analysis. This works focuses on the developing of a comprehensive software tool which can extract DC or three phase AC impedances, and apply stability analysis. An algorithm is designed to select FFT window and adjust perturbation frequencies. This feature enables the software to accurately measure impedances even in existence of system line harmonics. Furthermore, multi-tone approach is developed to improve simulation time. The complete software tool is tested with simulation models and experiment results, to show the effectiveness. When multi-tone approach is applied on nonlinear loads, it gives incorrect results. The reason is that perturbation frequency will have overlapping with side-band harmonics. An algorithm is designed to avoid this problem. The algorithm is tested with 12-pulse diode rectifier simulation model, and 6-pulse diode rectifier simulation model and experimental test bed. Both simulation and experiment results verifies the concept. / Master of Science

Opening a door is still a hard problem in robotics. Many robotic manipulators use open-loop position control to open doors, which reduces reusability and reliability in the face of slight differences or sensor errors. Many others use force feedback or impedance control but skip past the problem of grabbing the handle, which could lead to failures due to sensor errors. This research assumes that perception is faulty, and uses joint-level force feedback to probe the location of the door and its handle before attempting to open it. The resulting control strategy is at least 33% faster than the open-loop control system it replaces, and had an 83% success rate during testing in place of the previous method's 60% success rate. / Master of Science

Multiple STATCOM units in proximity have been adopted in power transmission systems in order to obtain better voltage regulation and share burdens. Throughout stability assessment in this dissertation, it is shown, for the first time, that STATCOMs could interact with each other in a negative way in the small-signal sense due to their control, causing voltage instability, while loads and transmission lines showed small effects. Since this voltage stability problem is induced by STATCOMs, d-q frame impedance-based stability analysis was used, for the first time, to explore the inherent power system instability problem with presence of STATCOMs as it provides an accurate understanding of the root cause of instability within the STATCOM control system. This dissertation first proposes the impedance model in d-q frame for STATCOMs, including dynamics from synchronization, current and voltage loops and reveals the significant features compared to other types of grid-tied converters that 1) impedance matrix strongly coupled in d and q channel due to nearly zero power factor, 2) different behaviors of impedances at low frequency due to inversed direction of reactive power and 3) coupled small-signal propagation paths on the voltage at point of common coupling from synchronization and ac voltage regulation. Using the proposed impedance model, this dissertation identifies the frequency range of interactions in a viewpoint of d-q frame impedances and pinpointed that the ac voltage regulation was the main reason of instability, masking the effects of PLL in power transmission systems. Due to the high impedance of STATCOMs compared to that of transmission lines around the frequency range of interactions, STATCOMs were seen to interact with each other through the transmission lines. A scaled-down 2-STATCOM power grid was built to verify the conclusions experimentally. / Ph. D. / STATCOMs have been proven a type of effective power electronics device for reactive power compensations and people are trying to install multiple STATCOMs in proximity in power systems in order to have better performances. This dissertation, for the first time, evaluates the operation of multiple STATCOMs in proximity and finds out that they could interact with each other in a negative way in the small-signal sense due to their control, causing voltage instability, while loads and transmission lines showed small effects. Since this voltage stability problem is induced by STATCOMs, d-q frame impedance-based stability analysis was used, for the first time, to explore the inherent power system instability problem with presence of STATCOMs as it provides an accurate understanding of the root cause of instability within the STATCOM control system. To this end, an impedance model of STATCOMs is proposed, which accurately explains the terminal behaviors of STATCOMs. Using the model, this dissertation identifies the frequency range of interactions in a viewpoint of d-q frame impedances and pinpointed that the ac voltage regulation was the main reason of instability, masking the effects of PLL in power transmission systems. All the above is validated experimentally in a scaled-down 2-STATCOM power system.

The proposed energy harvesting system intends to harvest vibrational energy via an electromagnetic generator (EMG). The proposed circuit intends to extract maximum power from the EMG by utilizing the maximum power transfer theorem which states that maximum power is transferred to the load when the source resistance equals the load resistance. The proposed circuit is a synchronous split-capacitor boost converter operating in boundary conduction mode (BCM) to achieve impedance matching and therefore maximum power transferred to the load. The circuit topology combines the rectifier and power stage to reduce power loss of the power management integrated circuit (PMIC). The proposed circuit is designed and fabricated in 130 nm BiCMOS technology. The circuit is validated through schematic level simulations and post-layout simulations. The results conclude the proposed circuit and control operates in a manner to achieve BCM. / Master of Science / Tracking and monitoring systems and products has become more prevalent in our society. Consumers want to know when a package they ordered will arrive. Grocery stores would like to track a produce from harvest to the shelves, ensuring their produce is safe to eat. Produce should be kept around 0 °C and if it exceeds that anywhere during the supply chain, the store should be alerted. Wireless sensor nodes (WSNs) are such devices that would be able to monitor the temperature of produce or the location of a package. These devices must be small, reliable, long-life and cost efficient. Using a battery to power WSNs is an inconvenience as the battery must be replaced often. The proposed circuit enables a self-sufficient WSN that is compact, dependable, long-lasting and economical when deployed at large scale. The proposed circuit has been designed, fabricated and proven through simulations.