Matching Items (32)
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- All Subjects: Biomedical Engineering
- All Subjects: Neurosciences
- Genre: Masters Thesis
- Creators: Wang, Xiao
- Creators: Abbas, James
- Creators: Honeycutt, Claire
- Member of: Theses and Dissertations
Description
Single cell phenotypic heterogeneity studies reveal more information about the pathogenesis process than conventional bulk methods. Furthermore, investigation of the individual cellular response mechanism during rapid environmental changes can only be achieved at single cell level. By enabling the study of cellular morphology, a single cell three-dimensional (3D) imaging system can be used to diagnose fatal diseases, such as cancer, at an early stage. One proven method, CellCT, accomplishes 3D imaging by rotating a single cell around a fixed axis. However, some existing cell rotating mechanisms require either intricate microfabrication, and some fail to provide a suitable environment for living cells. This thesis develops a microvorterx chamber that allows living cells to be rotated by hydrodynamic alone while facilitating imaging access. In this thesis work, 1) the new chamber design was developed through numerical simulation. Simulations revealed that in order to form a microvortex in the side chamber, the ratio of the chamber opening to the channel width must be smaller than one. After comparing different chamber designs, the trapezoidal side chamber was selected because it demonstrated controllable circulation and met the imaging requirements. Microvortex properties were not sensitive to the chambers with interface angles ranging from 0.32 to 0.64. A similar trend was observed when chamber heights were larger than chamber opening. 2) Micro-particle image velocimetry was used to characterize microvortices and validate simulation results. Agreement between experimentation and simulation confirmed that numerical simulation was an effective method for chamber design. 3) Finally, cell rotation experiments were performed in the trapezoidal side chamber. The experimental results demonstrated cell rotational rates ranging from 12 to 29 rpm for regular cells. With a volumetric flow rate of 0.5 µL/s, an irregular cell rotated at a mean rate of 97 ± 3 rpm. Rotational rates can be changed by altering inlet flow rates.
ContributorsZhang, Wenjie (Author) / Frakes, David (Thesis advisor) / Meldrum, Deirdre (Thesis advisor) / Chao, Shih-hui (Committee member) / Wang, Xiao (Committee member) / Arizona State University (Publisher)
Created2011
Description
The past two decades have been monumental in the advancement of microchips designed for a diverse range of medical applications and bio-analysis. Owing to the remarkable progress in micro-fabrication technology, complex chemical and electro-mechanical features can now be integrated into chip-scale devices for use in biosensing and physiological measurements. Some of these devices have made enormous contributions in the study of complex biochemical processes occurring at the molecular and cellular levels while others overcame the challenges of replicating various functions of human organs as implant systems. This thesis presents test data and analysis of two such systems. First, an ISFET based pH sensor is characterized for its performance in a continuous pH monitoring application. Many of the basic properties of ISFETs including I-V characteristics, pH sensitivity and more importantly, its long term drift behavior have been investigated. A new theory based on frequent switching of electric field across the gate oxide to decrease the rate of current drift has been successfully implemented with the help of an automated data acquisition and switching system. The system was further tested for a range of duty cycles in order to accurately determine the minimum length of time required to fully reset the drift. Second, a microfluidic based vestibular implant system was tested for its underlying characteristics as a light sensor. A computer controlled tilt platform was then implemented to further test its sensitivity to inclinations and thus it‟s more important role as a tilt sensor. The sensor operates through means of optoelectronics and relies on the signals generated from photodiode arrays as a result of light being incident on them. ISFET results show a significant drop in the overall drift and good linear characteristics. The drift was seen to reset at less than an hour. The photodiodes show ideal I-V comparison between photoconductive and photovoltaic modes of operation with maximum responsivity at 400nm and a shunt resistance of 394 MΩ. Additionally, post-processing of the tilt sensor to incorporate the sensing fluids is outlined. Based on several test and fabrication results, a possible method of sealing the open cavity of the chip using a UV curable epoxy has been discussed.
ContributorsMamun, Samiha (Author) / Christen, Jennifer Blain (Thesis advisor) / Goryll, Michael (Committee member) / Yu, Hongyu (Committee member) / Arizona State University (Publisher)
Created2011
Description
Flow measurement has always been one of the most critical processes in many industrial and clinical applications. The dynamic behavior of flow helps to define the state of a process. An industrial example would be that in an aircraft, where the rate of airflow passing the aircraft is used to determine the speed of the plane. A clinical example would be that the flow of a patient's breath which could help determine the state of the patient's lungs. This project is focused on the flow-meter that are used for airflow measurement in human lungs. In order to do these measurements, resistive-type flow-meters are commonly used in respiratory measurement systems. This method consists of passing the respiratory flow through a fluid resistive component, while measuring the resulting pressure drop, which is linearly related to volumetric flow rate. These types of flow-meters typically have a low frequency response but are adequate for most applications, including spirometry and respiration monitoring. In the case of lung parameter estimation methods, such as the Quick Obstruction Method, it becomes important to have a higher frequency response in the flow-meter so that the high frequency components in the flow are measurable. The following three types of flow-meters were: a. Capillary type b. Screen Pneumotach type c. Square Edge orifice type To measure the frequency response, a sinusoidal flow is generated with a small speaker and passed through the flow-meter that is connected to a large, rigid container. True flow is proportional to the derivative of the pressure inside the container. True flow is then compared with the measured flow, which is proportional to the pressure drop across the flow-meter. In order to do the characterization, two LabVIEW data acquisition programs have been developed, one for transducer calibration, and another one that records flow and pressure data for frequency response testing of the flow-meter. In addition, a model that explains the behavior exhibited by the flow-meter has been proposed and simulated. This model contains a fluid resistor and inductor in series. The final step in this project was to approximate the frequency response data to the developed model expressed as a transfer function.
ContributorsHu, Jianchen (Author) / Macia, Narciso (Thesis advisor) / Pollat, Scott (Committee member) / Rogers, Bradley (Committee member) / Arizona State University (Publisher)
Created2013
Description
The object of this study is to charac terize the effect of focused ultrasound stimulation (FUS) on the rat ce rvix which has been observed to speed its ripening during pregnancy. Ce rvical ripening is required for successful fetal delivery. Timed-pregnant Sprague-Dawley rats (n=36) were used. On day 14 of gestation, the FUS system was placed on the body surface of the rat over the cervix and ultrasound energy was applied to cervix for variable times up to 1 hour in the control group, the FUS system was placed on rats but no energy was applied. Daily measurement of cervix light-induced florescence (LIF, photon counts of collagen x-bridge fluorescence) were made on days 16 of gestation and daily until spont-aneous delivery (day22) to estimate changes in cervical ripening. We found that pulses of 680 KHz ultrasound at 25 Hertz, 1 millisecond pulse duration at 1W/cm^2 applied for as little as 30 minutes would immediately afterwards show the cervix to hav e ripened to the degree seen just before delivery on day 22. Delivery times, fetal weights and viability were unaffected in the FUS-treated animals.
ContributorsLuo, Daishen (Author) / Towe, Bruce C (Thesis advisor) / Wang, Xiao (Committee member) / Caplan, Michael (Committee member) / Arizona State University (Publisher)
Created2012
Description
Electronic devices are gaining an increasing market share in the medical field. Medical devices are becoming more sophisticated, and encompassing more applications. Unlike consumer electronics, medical devices have far more limitations when it comes to area, power and most importantly reliability. The medical devices industry has recently seen the advantages of using Flash memory instead of Read Only Memory (ROM) for firmware storage, and in some cases to replace Electrically Programmable Read Only Memories (EEPROMs) in medical devices for frequent data storage. There are direct advantages to using Flash memory instead of Read Only Memory, most importantly the fact that firmware can be rewritten along the development cycle and in the field. However, Flash technology requires high voltage circuitry that makes it harder to integrate into low power devices. There have been a lot of advances in Non-Volatile Memory (NVM) technologies, and many Flash rivals are starting to gain attention. The purpose of this thesis is to evaluate these new technologies against Flash to determine the feasibility as well as the advantages of each technology. The focus is on embedded memory in a medical device micro-controller and application specific integrated circuits (ASIC). A behavioral model of a Programmable Metallization Cell (PMC) was used to simulate the behavior and determine the advantages of using PMC technology versus flash. When compared to flash test data, PMC based embedded memory showed a reduction in power consumption by many orders of magnitude. Analysis showed that an approximated 20% device longevity increase can be achieved by using embedded PMC technology.
ContributorsHag, Eslam E (Author) / Kozicki, Michael N (Thesis advisor) / Schroder, Dieter K. (Committee member) / Goryll, Michael (Committee member) / Arizona State University (Publisher)
Created2010
Description
Portable health diagnostic systems seek to perform medical grade diagnostics in non-ideal environments. This work details a robust fault tolerant portable health diagnostic design implemented in hardware, firmware and software for the detectionof HPV in low-income countries. The device under device under test (DUT) is a fluorescence based lateral flow assay (LFA) point-of-care (POC) device. This work’s contributions are: firmware and software development, calibration routine implementation, device performance characterization and a proposed method of in-software fault detection. Firmware was refactored from the original implementation of the POC fluorescence reader to expose an application programming interface (API) via USB. Companion software available for desktop environments (Windows, Mac and Linux) was created to interface with this firmware API and conduct macro level routines to request and receive fluorescence data while presenting a user-friendly interface to clinical technicians. Lastly, an environmental chamber was constructed to conduct sequential diagnostic reads in order to observe sensor drift and other deviations that might present themselves in real-world usage. The results from these evaluations show a standard deviation of less than 1% in fluorescence readings in nominal temperature environments (approx. 25C) suggesting that this system will have a favorable signal-to-noise (SNR) ratio in such a setting. In non-ideal over heated environments (≥38C), the evaluation results showed performance degradation with standard deviations as large as 15%.
ContributorsLue Sang, Christopher David (Author) / Blain Christen, Jennifer M (Thesis advisor) / Ozev, Sule (Committee member) / Goryll, Michael (Committee member) / Raupp, Gregory (Committee member) / Arizona State University (Publisher)
Created2022
Description
The blood-brain-barrier (BBB) is a significant obstacle for treating many neurological disorders. Bubble-assisted focused ultrasound (BAFUS) medicated BBB disruption is a promising technology that enables the delivery of large drug doses at targeted locations across the BBB. However, the current lack of an in vitro model of this process hinders the full understanding of BAFUS BBB disruption for better translation into clinics. In this work, a US-transparent organ-on-chip device has been fabricated that can be critical for the in vitro modeling of the BAFUS BBB disruption. The transparency of the device window to focused ultrasound (FUS) was calculated theoretically and demonstrated by experiments. Nanobubbles were fabricated, characterized by cryogenic transmission electron microscopy (cryo-TEM), and showed bubble cavitation under FUS. Human colorectal adenocarcinoma (Caco-2) cells were used to form a good cellular barrier for BAFUS barrier disruption, as suggested by the measured permeability and transepithelial electrical resistance (TEER). Finally, barrier disruption and recovery were observed in BAFUS disrupted US-transparent organ-on-chips with Caco-2 barriers, showing great promise of the platform for future modeling BAFUS BBB disruption in vitro.
ContributorsAkkad, Adam Rifat (Author) / Gu, Jian (Thesis advisor) / Nikkhah, Mehdi (Thesis advisor) / Belohlavek, Marek (Committee member) / Wang, Xiao (Committee member) / Arizona State University (Publisher)
Created2022
Description
Studies using transcranial direct current stimulation (tDCS) to enhance motor training areoften irreproducible. This may be partly due to differences in stimulation parameters across
studies, but it is also plausible that uncontrolled placebo effects may interact with the true
‘treatment’ effect of tDCS. Thus, the purpose of this study was to test whether there was a
placebo effect of tDCS on motor training and to identify possible mechanisms of such an effect.
Fifty-one participants (age: 22.2 ± 4.16; 26 F) were randomly assigned to one of three groups:
active anodal tDCS (n=18), sham tDCS (n=18), or no stimulation control (n=15). Participant
expectations about how much tDCS could enhance motor function and their general suggestibility
were assessed. Participants then completed 30 trials of functional upper extremity motor training
with or without online tDCS. Stimulation (20-min, 2mA) was applied to the right primary motor
cortex (C4) in a double-blind, sham-controlled fashion, while the control group was unblinded and
not exposed to any stimulation. Following motor training, expectations about how much tDCS
could enhance motor function were assessed again for participants in the sham and active tDCS
groups only. Results showed no effect of active tDCS on motor training (p=.67). However, there
was a significant placebo effect, such that the collapsed sham and active tDCS groups improved
more during motor training than the control group (p=.02). This placebo effect was significantly
influenced by post-training expectations about tDCS (p=.0004). Thus, this exploratory study
showed that there is a measurable placebo effect of tDCS on motor training, likely driven by
participants’ perceptions of whether they received stimulation. Future studies should consider
placebo effects of tDCS and identify their underlying mechanisms in order to leverage them in
clinical care.
ContributorsHAIKALIS, NICOLE (Author) / Schaefer, Sydney Y (Thesis advisor) / Honeycutt, Claire (Committee member) / Daliri, Ayoub (Committee member) / Arizona State University (Publisher)
Created2022
Description
This work focuses on qualifying the performance of an optoelectrical measurement system designed to analyze ribonucleic acid (RNA) within a micro sample. The system is capable of measuring light intensity converted to voltage versus time and is a fast, inexpensive, and portable method for rapid detection of biologics such as SARS-CoV-2 virus, or Covid-19 disease. The measurement system consists of a microfluidic chip and a point of care fluorescent reader.The intent of this research is to measure consistency and robustness of the fluorescent reader combined with the microfluidic chip. The consistency and the robustness of the fluorescent reader within the duty cycle of the system power and the measurement system were analyzed with Six Sigma methods. Control charts, analysis of variance (ANOVAs), and variance components calculations were implemented to characterize the reader system. Through the process of this analysis, baseline characteristics were measured and documented providing valuable data for the improved instrument design.
The existing microfluidic chip is a prototype that works in combination with the reader based on fluorescent detection. Baseline studies were required to define any issues related to microfluidic autofluorescence. Multiple designs were tested to measure reduction in autofluorescence in the microfluidics. It was found that certain designs performed better than others. One approach for improvement in the microfluidic chip may be achieved by characterizing and source controlling materials, optimizing layers, mask apertures, and mask orientations to determine reliability in the measurable output through the fluorescent reader. Since the reader and the microfluidic are designed to work together, any future studies should explore testing where the two components are considered a coupled system.
ContributorsShabtai, Bat-El (Author) / Blain Christen, Jennifer (Thesis advisor) / Abbas, James (Thesis advisor) / Maass, Eric (Committee member) / Beeman, Scott (Committee member) / Arizona State University (Publisher)
Created2021
Description
Adapting to one novel condition of a motor task has been shown to generalize to other naïve conditions (i.e., motor generalization). In contrast, learning one task affects the proficiency of another task that is altogether different (i.e. motor transfer). Much more is known about motor generalization than about motor transfer, despite of decades of behavioral evidence. Moreover, motor generalization is studied as a probe to understanding how movements in any novel situations are affected by previous experiences. Thus, one could assume that mechanisms underlying transfer from trained to untrained tasks may be same as the ones known to be underlying motor generalization. However, the direct relationship between transfer and generalization has not yet been shown, thereby limiting the assumption that transfer and generalization rely on the same mechanisms. The purpose of this study was to test whether there is a relationship between motor generalization and motor transfer. To date, ten healthy young adult subjects were scored on their motor generalization ability and motor transfer ability on various upper extremity tasks. Although our current sample size is too small to clearly identify whether there is a relationship between generalization and transfer, Pearson product-moment correlation results and a priori power analysis suggest that a significant relationship will be observed with an increased sample size by 30%. If so, this would suggest that the mechanisms of transfer may be similar to those of motor generalization.
ContributorsSohani, Priyanka (Author) / Schaefer, Sydney (Thesis advisor) / Daliri, Ayoub (Committee member) / Honeycutt, Claire (Committee member) / Arizona State University (Publisher)
Created2018