Doctor of Philosophy, The Ohio State University, 2024, Materials Science and Engineering

This dissertation presents biochemical sensing systems for wearable, implantable, and high-resolution chemical sensing applications. By integrating biorecognition elements, sensing interfaces, and wireless communication strategies, we aim to provide a low-cost, reliable, and highly accurate platform for real-time biochemical monitoring in clinical and experimental settings. We first demonstrate a wireless sensing system that is miniaturized, lightweight, and compatible with common biochemical sensing interfaces. Inspired by RF tuning circuits, our simple circuit design allows battery-free operation and accurate monitoring of multiple biomarkers. The modular design separates the inductive coupling unit and the electrochemical sensing interface, minimizing strain-induced changes and ensuring accurate recording. This system is compatible with common electrochemical sensing methods, including ion-sensitive membranes (ISM), aptamer-based sensors, and enzymatic interfaces. And allow for the detection of ions, neurotransmitters, and metabolites across different application scenarios. For instance, a "smart necklace" consists of glucose sensors, that are capable of wirelessly detecting sweat glucose during exercise. A wearable skin patch monitored cortisol levels in sweat showcases the functional adaptability for stress-related biomarker detection. Additionally, a miniaturized implant prototype illustrated the potential for continuous in vivo monitoring. Our work also introduces a portable vector network analyzer (pVNA) designed to overcome the size limitations of traditional VNAs. This research provides the design and working principle for a wearable reader, which allows for real-time monitoring of resonance frequency and Q factor of the inductive coupling wireless sensor. Furthermore, we introduce “NeuroThread”, a neurotransmitter-sensing platform that utilizes the cross-section of commercially available ultrathin microwires to serve as microelectrode. This cost (open full item for complete abstract)

Committee: Jinghua Li (Advisor); Heather Powell (Committee Member); Pelagia-Irene Gouma (Committee Member) Subjects: Engineering; Materials Science; Nanoscience; Neurosciences

PhD, University of Cincinnati, 2022, Engineering and Applied Science: Electrical Engineering

It is commonly acknowledged that the continuous glucose monitor for diabetes management is a historical achievement of modern diagnostics technology. However, it has been the only success despite acute needs for the real-time monitoring of many other molecules across the broader field of human disease management such as cardiac, drug dosing, fertility and other problems. The limitation is that the well-studied commercially available glucose sensors are enzymatic, which makes it very difficult to generalize its working mechanism to other analytes. Meanwhile, unlike enzymatic sensors, electrochemical aptamer-based sensors are broadly generalizable, demonstrated by several examples of real-time, in-vivo molecular monitoring at nanomolar to micromolar concentrations. So far, electrochemical aptamer-based (EAB) sensor demonstrations are highly prevalent for testing in buffer fluid or blood. This should not be surprising because the testing criteria for these fluids are highly applicable and because both fluids are well-buffered in their pH and salinity. Aptamers are known to be sensitive to both salinity and pH, thus affecting sensor output and analyte response. However, some emerging biofluids for biosensing such as human sweat or environmental fluids can have widely ranging pH and salinity. In this dissertation, a novel oil membrane sensor protection technique is reported against changes in pH and salinity for EAB sensors, where a thin, semi-permeable hydrophobic membrane will allow the target hydrophobic analyte diffuse to the sensor through while preventing diffusion of hydrophilic interferents (proteins, acids, bases, etc.). The encapsulated EAB cortisol sensor can perform in a pseudo real-time manner (5-minute concentration-on rise time and 10-minute concentration-off down time) and maintains measurement signal for at least 7 hours even in the extreme acidic solution of pH 3. EAB sensors conventionally bond the aptamer to a gold working electrode via thiol l (open full item for complete abstract)

Committee: Jason Heikenfeld Ph.D. (Committee Member); Michael Brothers Ph.D. (Committee Member); Ryan White Ph.D. (Committee Member); Andrew Steckl Ph.D. (Committee Member); Leyla Esfandiari Ph.D. (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy in Engineering, University of Toledo, 2021, Engineering

Reactive oxygen species (ROS) are constantly generated in human cells. The most found ROS are superoxide (O2•−), hydrogen peroxide (H2O2), and hydroxyl radicals (•OH). These ROS are considered either constructive or destructive species depending on their level in live cells. A proper level of ROS provides several benefits, such as control of blood pressure, elimination of bacteria, and interruption of virus activity. However, the overproduction of ROS as a result of a weak antioxidant mechanism in cells turns ROS into destructive species. Tissue damage and cell death are some of the major detrimental effects of ROS. Cancer, skin aging, diabetes, heart disease, tumors, and several neurodegenerative diseases are examples of fatal conditions related to tissue damage and cells death from uncontrolled concentrations of ROS. Among all ROS, hydroxyl radicals (•OH) are the most reactive and dangerous ones, with a short lifetime of nanoseconds. Thus, the ability to detect and measure the concentration of •OH in real time could provide a crucial piece of information to understand the role that ROS play on the development of those fatal diseases. As a result, this thesis focuses on the development of an electrochemical sensor for the detection of hydroxyl free radicals. To do so, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to analyze the interaction between the electrochemical sensor and •OH. In order to detect •OH, the electrochemical sensor required the use of a sensing element. Since cerium oxide (CeOx) is a well-known scavenger of hydroxyl free radicals, this was used as the sensing element of the device. In order to provide the sensor with both sensitivity and selectivity, our research focused on the development of nanocomposites containing both cerium oxide nanoparticles (CeNPs) and a highly conductive material, such as graphene oxide (GO) or highly conductive carbon. First, we developed a composite-based electrochemic (open full item for complete abstract)

Committee: Dong-Shik Kim (Advisor); Ana C. Alba-Rubio (Advisor); Steve Kim (Committee Member); Maria Coleman (Committee Member); Youngwoo Seo (Committee Member) Subjects: Chemical Engineering; Chemistry

Doctor of Philosophy, The Ohio State University, 2015, Chemistry

This dissertation focuses on three projects involving the development of harsh environment gas sensors. The first project discusses the development of a multipurpose oxygen sensor electrode for use in sealing with the common electrolyte yttria stabilized zirconia. The purpose of the sealing function is to produce an internal reference environment maintained by a metal/metal oxide mixture, a criteria for miniaturization of potentiometric oxygen sensing technology. This sensor measures a potential between the internal reference and a sensing environment. The second project discusses the miniaturization of an oxygen sensor and the fabrication of a more generalized electrochemical sensing platform. The third project discusses the discovery of a new mechanism in the electrochemical sensing of ammonia through molecular recognition and the utilization of a sensor taking advantage of the new mechanism. An initial study involving the development of a microwave synthesized La0.8Sr0.2Al0.9Mn0.1O3 sensor electrode material illustrates the ability of the material developed to meet ionic and electronic conducting requirements for effective and Nernstian oxygen sensing. In addition the material deforms plastically under hot isostatic pressing conditions in a similar temperature and pressure regime with yttria stabilized zirconia to produce a seal and survive temperatures up to 1350 oC. In the second project we show novel methods to seal an oxygen environment inside a device cavity to produce an electrochemical sensor body using room temperature plasma-activated bonding and low temperature and pressure assisted plasma-activated bonding with silicon bodies, both in a clean room environment. The evolution from isostatic hot pressing methods towards room temperature complementary metal oxide semiconductor (CMOS) compatible technologies using single crystal silicon substrates in the clean room allows the sealing of devices on a much larger scale. Through this evolution in bonding te (open full item for complete abstract)

Committee: Prabir Dutta (Advisor) Subjects: Chemistry; Materials Science

Doctor of Philosophy, The Ohio State University, 2012, Materials Science and Engineering

A new potentiometric CO2 gas sensor using lithium-lanthanum-titanate (Li0.35La0.55TiO3) electrolyte, Li2CO3 sensing electrode, and Li2TiO3+TiO2 reference electrode was investigated. The microstructure and electrical properties of the optimized solid electrolyte were examined and the measured conductivity values were found consistent with those reported in literature. The sensor was tested under dry condition in 21% O2/N2 at temperatures ranging from 250 to 550°C. As the temperature increased, the percentage of Nernstian behavior improved from 50% at 250°C to 95% at 450°C, but the performance degraded above 450°C. The proposed hypothesis for the degradation is as follows. Depending on CO2 partial pressure, Li2CO3 can decompose and react with Li0.35La0.55TiO3 around 475-500°C resulting in insertion of Li+ into Li0.35La0.55TiO3 that causes structural distortion. When the reaction between Li2CO3 and Li0.35La0.55TiO3 occurs at elevated temperatures such as at 700°C, the distorted structure transforms to disordered LaLi1/3Ti2/3O3 and the sensor performance degrades irreversibly. Thermodynamic calculations combined with solid-state reaction under controlled atmosphere followed by X-ray diffraction (XRD) are used to confirm the hypothesis. Finally, for device fabrication, it is demonstrated that introduction of high concentration of CO2 (~99.99%) can avoid the reaction between Li2CO3 and Li0.35La0.55TiO3 at high temperatures, which also facilitates good bonding between the electrode and the electrolyte. As for long-term device performance, it is shown that the sensor can measure changes in CO2 concentrations reproducibly as long as it is operated in conditions where there is a background of CO2, such as in ambient atmosphere or combustion systems.

Committee: Sheikh Akbar Prof/PhD (Advisor); Prabir Dutta Prof/PhD (Advisor); Gerald Frankel Prof/PhD (Committee Member); Patricia Morris Prof/PhD (Committee Member) Subjects: Materials Science

Doctor of Philosophy, Case Western Reserve University, 2008, Chemical Engineering

Solid state electrochemical sensors have demonstrated their usefulness for measuring the physical and the chemical properties of the electrolytes and in both liquid and gaseous phases. These electrochemical sensors provide rapid response to property/concentration changes with high sensitivity, excellent reproducibility, and good long-term stability. Using thin and thick film microfabrication techniques, these solid state electrochemical sensors can be further improved and miniaturized to incorporate additional advantages such as high resolution, small feature size (μm or even nm), small required sample volume, small ohmic potential drop, improved signal to noise ratio, and reduced fabrication cost.Advanced analytical and computational methods for the evolution of the environment on metal surfaces require data for the environmental properties of thin layers of moisture, moist particulates, and deposits that will affect the corrosion performance of metals. The advanced sensor technology development and application of the sensors reported in this study address these needs. The sensor development and findings reported here are important complements to a multi-investigator program that strives for increased scientific understanding, enhanced process models, and advanced technologies for long-term corrosion performance. In the first part of this study, microfabricated electrochemical sensors for environmental parameter measurements have been developed and characterized, including Pt based thin film electrolyte solution conductivity sensor, Pd/PdO based thick film pH sensor, and Au based thick film dissolved oxygen concentration sensor. These sensors utilized AC impedance, potentiometric open circuit potential decay, and amperometric i-t techniques for conductivity, pH, and dissolved oxygen concentration measurements, respectively. In the second part of this study, a multi-component, multi-layer structured thin film high-temperature gaseous oxygen sensor incorporating two (open full item for complete abstract)

Committee: Chung-Chiun LIU (Committee Chair); Uziel Landau (Committee Member); Heidi Martin (Committee Member); Kenneth Loparo (Committee Member) Subjects: Chemical Engineering

Master of Science (MS), Ohio University, 2020, Chemical Engineering (Engineering and Technology)

An electrochemical sensor for detecting the bacterium Escherichia coli (E. coli) in water has been developed. The sensor probe was electrochemically characterized by chronoamperometry to obtain the current responses from different concentrations of E. coli. The presence of E. coli hindered the formation of a locally formed catalyst leading to a drop in current. Current responses specific from standardized microbial concentrations were recorded and a calibration model was developed. Our electrochemical microbial sensor (EMS) can sense the presence/absence of E. coli in less 0.5 seconds, has a detection limit of 10^2 colony forming units per milliliter, and can quantify the microbial concentration within 10 minutes. This sensor was also tested successfully with real wastewater samples for E. coli detection. Thus, EMS shows potential for field applications.

Committee: Valerie Young (Advisor); Ronan Carroll (Committee Member); Howard Dewald (Committee Member); Sumit Sharma (Committee Member); Gerardine Botte (Advisor) Subjects: Biomedical Engineering; Chemical Engineering

PhD, University of Cincinnati, 2018, Engineering and Applied Science: Electrical Engineering

The future of disease diagnostics and health care wearables lies in the development of low-cost sensors and devices that can detect minute traces of pathogens or antigens from body fluids. These devices will allow patients to run point of care diagnostics tests, thereby saving time and cost of running clinical tests and ultimately can provide early stage disease diagnosis and enable physicians to provide better-personalized treatment. There have been developments that focus on integrating multiple different tests into a single device that measures analytes from biofluids. Detection of glucose together with some single ions in a single device and test is the current attractive research advancement. Electrochemistry Impedance Spectroscopy (EIS) is widely popular in the medical field where it is used to analyze biological materials as well as characterization of body fluids. It is a complex technique requiring expensive equipment that is also bulky making it difficult to integrate into small form-factor systems that are handheld, wearable and intended for use in point of care testing. This research work focused on developing a proof of concept prototype system with a flexible architecture that can be used for testing multiple sensors using EIS electroanalytical technique. The system is based on an embedded system design to be factored to achieve small valuation time for results along with being compact and portable enough to be used outside laboratory bench setting. The prototype successfully calculates the magnitude and phase of the impedance responses multiple electrochemical cells. The device transmits test data wirelessly to a personal computer or tablet which works together with an analysis and control display.

Committee: Fred Beyette Ph.D. (Committee Chair); Jason Heikenfeld Ph.D. (Committee Member); Carla Purdy Ph.D. (Committee Member); Ryan White Ph.D. (Committee Member); Philip Wilsey Ph.D. (Committee Member) Subjects: Electrical Engineering

Master of Science, The Ohio State University, 2017, Mechanical Engineering

Investment in nuclear technology is experiencing a revitalization as nuclear power becomes uniquely poised to take the burden left by phasing out fossil fuels to meet climate change goals. The United States Department of Energy is investing in research and development of the Fluoride salt-cooled High-temperature Reactor (FHR) with the ultimate goal of a 2030 deployment. One challenge presented by this reactor is corrosion of the reactor's structural materials by the molten salt due to foreign and generated impurities. These impurities will shift the reduction-oxidation (redox) potential of the salt beyond the equilibrium potential of candidate structural materials, causing accelerated corrosion. This issue demands control of the molten salt's redox condition in order to prevent unacceptable levels of corrosion. Research has been conducted on methods for redox control and electrochemical measurement techniques. The limited research that has been conducted related to measurement apparatus either lack certain characteristics specific to application for the FHR reactor or appropriate comparison to demonstrate first rate performance. The primary issue presented by an electrochemical sensor for this application is the selection of an appropriate reference electrode. This report investigates candidate reference electrodes with the purpose of identifying a leading candidate and proposing a holistic electrochemical sensor design which possesses high performance, durability, and ease of use. Candidate reference electrodes are the platinum quasi-reference electrode, dynamic reference electrode, gold/sodium alloy reference electrode, and nickel/nickel(II) reference utilizing a boron nitride sheath. Electrochemical tests show that cyclic voltammetry is a precise technique to measure the concentration of a redox agent. Experiments also show that a quasi-reference electrode is the best suited reference for this application when paired with dynamic operational techniques. This ch (open full item for complete abstract)

Committee: Jinsuo Zhang (Advisor); Marat Khafizov (Advisor) Subjects: Mechanical Engineering; Nuclear Engineering

PhD, University of Cincinnati, 2015, Arts and Sciences: Chemistry

Carbon plays a major role in electrochemistry as an electrode material. It exhibits slow kinetics of electrode oxidation, which leads to a wide potential window with low residual current and makes the electrode versatile for studying many redox reactions. Carbon nanotubes (CNTs) are allotropes of sp2 carbon with a cylindrical structure. They possess a remarkable variety of structural, mechanical, chemical and electronic properties. Chemical stability and high current densities give desirable properties to carbon nanotube materials for the field of electrochemistry. Spectroelectrochemistry is the combination of species-focused spectroscopy with reaction-oriented electrochemistry. It uniquely employs electrochemistry and spectroscopy in a single device. In contrast to the essentially physical spectroscopic techniques, which are well suited for species characterization, electrochemistry provides the capability of monitoring a chemical reaction occurring at an interface, typically between a solution (analyte of interest in electrolyte) and an electrode. The Heineman research group at the University of Cincinnati has been working on characterizing different materials using electrochemical and spectroscopic techniques and developing electrochemical, spectroelectrochemical sensors and biosensors based on those novel materials. This dissertation presents the results of six aspects of the projects in the Heineman group. The first study includes the characterization of novel catalyst free CNT disk electrodes. The electrochemical properties of CNT disk electrodes were compared with commercial glassy carbon electrode and showed a much faster heterogeneous electron transfer rate and larger microscopic surface area. The second study investigated the properties of catalyst free CNT loaded Nafion film and its application in making metal ion sensors. The third study focused on characterizing the CNT transparent film synthesized by a chemical vapor deposition process and (open full item for complete abstract)

Committee: William Heineman Ph.D. (Committee Chair); Michael Baldwin Ph.D. (Committee Member); Thomas Ridgway Ph.D. (Committee Member) Subjects: Analytical Chemistry

PhD, University of Cincinnati, 2012, Arts and Sciences: Chemistry

This dissertation describes development and characterization of the electrochemical sensors for studying the corrosion of biodegradable metallic implant for the overall RMB research project and electrochemical biosensors for the detection of bacteria. Specifically, three major projects were done. The first involved fabrication and characterization of electrochemical sensors for the cations Zn2+, Ca2+, Mg2+, and H+ using carbon nanotubes (CNTs). Detection of Zn2+ was based on an ASV sensor at a CNT tower electrode with a detection limit of 67 nM without any toxic additives. Sensors for the cations Ca2+, Mg2+, and H+ were solid contact-ion selective electrode (SC-ISE) based on CNT towers. SC-ISE can detect Ca2+ as low as 1.6 ¿¿¿¿M with a stable potential for up to three weeks. These electrodes can detect other cations by changing the sensing membrane. The second part was the development of three systems to study the corrosion of biodegradable metallic implants: corrosion characterization system (CCS), static in vitro CCS, and dynamic in vitro CCS. Multiple appropriate sensors were chosen and applied to these three systems to monitor the degradation of Mg alloy simultaneously and continuously. The third part was the development of label-free biosensor for bacteria based on faradaic EIS as a spin-off project of RMB. a-Mannoside was immobilized on a gold disk electrode using a SAM via a spacer terminated in a thiol functionality. A linear relationship between normalized Ret and the logarithmic value of E. coli concentrations was found in a range of bacterial concentration from 102 to 103 CFU/mL. The combination of robust carbohydrate ligands with EIS provides a label-free, sensitive, specific, user-friendly, robust, and portable biosensing system that could potentially be used in point-of-care or continuous environmental monitoring settings. The development of electrochemical sensors based on advanced carbon materials and the development of three testing systems (CCS, s (open full item for complete abstract)

Committee: William Heineman PhD (Committee Chair); Hairong Guan PhD (Committee Member); Thomas Ridgway PhD (Committee Member) Subjects: Chemistry

MS, University of Cincinnati, 2006, Engineering : Electrical Engineering

The main goal of this research is to amperometrically characterize a ring type nano interdigitated array (nIDA) electrode as an electrochemical sensor and to verify the enhancements in the sensitivity of such a sensor when compared to its micro counterparts. Each electrode was fabricated in gold with 275 fingers, each of width 100 nm and spacing 200 nm, using electron beam lithography and nano lift-off processes on a SiO2/Si wafer. The reference and counter electrodes were fabricated using electroplating. P – Aminophenol (PAP) was used as the redox species to be detected by the nano-IDA electrochemical sensor. Using Chronoamperometry, concentrations of PAP as low as 10 pM were successfully detected using the fabricated sensor. The current output by the sensor for such low concentrations was in the pico-ampere range and was measured using a very sensitive pico-ammeter. An instrumentation circuit was designed and fabricated to reliably convert the pico-ampere currents to corresponding voltage levels for further signal processing. The lowest concentration detected by the nano-IDA electrochemical sensor was three orders of magnitude less than that detected by the micro-IDA. This proves the enhanced sensitivity at lower dimensions for an electrochemical sensor which will find very wide application in a variety of fields, the main one being the rapidly emerging field of biosensors.

Committee: Dr. Chong Ahn (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2007, Chemistry

Solid-state electrochemical gas sensing devices composed of stabilized-zirconia electrolyte have used extensively in the automobile and chemical industry. Two types of electrochemical devices, potentiometric and amperometric, were developed in this thesis for total NOx (NO + NO2) detection in harsh environments. In potentiometric devices, Pt covered with Pt containing zeolite Y (PtY) and WO3 were examined as the two electrode materials. Significant reactivity differences toward NOx between PtY and WO3 led to the difference in non-electrochemical reactions and resulted in a electrode potential. With gases passing through a PtY filter, it was possible to remove interferences from 2000 ppm CO, 800 ppm propane, 10 ppm NH3, as well as to minimize effects of 1~13% O2, CO2, and H2O. Total NOx concentration was measured by maintaining a temperature difference between the filter and the sensor. The sensitivity was significantly improved by connecting sensors in series. Amperometic devices were also developed to detect NOx passing through the PtY filter. By applying a low anodic potential of 80 mV, NO in the NOx equilibrated mixture can be oxidized at a Pt working electrode on the YSZ electrolyte at 500°C. The PtY can be held separate from the YSZ or coated onto the YSZ as a film. This design was demonstrated to exhibit total-NOx detection capability, a low NOx detection limit (< 1 ppm), high NOx selectivity relative to CO and oxygen, and linear dependence on NOx concentration. The non-electrochemical reactions around the triple-phase boundary were studied to understand the origin of the superior performance of WO3 on potentiometric NOx sensing. From TPD, DRIFTS, XRD, Raman, and catalytic activity measurements, the interfacial reactions between WO3 and YSZ were found to dramatically reduce the NOx catalytic activity of YSZ. WO3 reacted with surface Y2O3 on YSZ and formed less catalytically active yttrium tungsten oxides and monoclinic ZrO2, which suppressed the non-electroche (open full item for complete abstract)

Committee: Prabir Dutta (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2004, Materials Science and Engineering

An electrochemical CO2 gas sensor with lithium ion conductor was developed and characterized in order to examine the potential for real-life applications and understand its sensing mechanism. Li2CO3 and Li2TiO3+TiO2 mixture were used as a sensing and a reference auxiliary phase, respectively. This electrochemical cell with a solid state Li3PO4 electrolyte has shown good selectivity, sensitivity and linear response in laboratory and automobile exhaust tests. However, the sensor response to CO2 gas showed a systematic deviation from the Nernst equation. Measured EMF did not agree with that calculated from the Nernst equation, even though it followed logarithmic behavior. Moreover, high sensitivity was observed for high CO2 concentrations (5~50%), compared to that for concentrations (500~5000 ppm). Two possible reasons for this deviation are: (1) reversibility of electrode reaction and (2) mixed ionic and electronic conduction of the electrolyte. Unless electrode reaction is fast enough, electrode polarization can easily induce overpotential. Pure ionic conduction of electrolyte is also necessary to avoid EMF loss during open circuit potential measurement. EIS (Electrochemical Impedance Spectroscopy) was used to study electrode kinetics. We found that Li2TiO3+TiO2 mixture reference electrode reaction is sluggish showing large electrode impedance. This impedance, however, was not affected by gas concentration change. On the other hand, that at the Li2CO3 sensing electrode is relatively small and it increased with decreased CO2 and O2 concentration. It was also observed that these electrode impedances induced the overpotential when the current flowed through the sensor. This electrode overpotential problem was minimized by mixing gold powder or porous sputtered gold electrode increasing effective reaction sites of the electrode. New electrode design improved the sensor EMF closer to the Nernstian values, however, the discrepancy still remained. Moreover, at higher sensor (open full item for complete abstract)

Committee: Sheikh Akbar (Advisor) Subjects: Engineering, Materials Science

Doctor of Philosophy, Case Western Reserve University, 2010, Chemical Engineering

A growing problem in the population is the increasing number of individuals suffering from forms of liver disease. In liver disease such as hepatitis and cirrhosis, early detection will dramatically increase the odds of survival or severity of disease management. Detection and diagnosis of liver disease would benefit greatly from the development of a rapid and easy detection method. Such a method would be especially vital in economically disadvantaged areas of the world where millions are suffering. In countries such as Egypt, Rwanda and Tanzania levels of hepatitis C infection are estimated to be present in more than 10% of the population with no effective means to monitor due to costs of diagnosis and limited access to medical facilities. In this research, the ability to detect the presence of liver disease using a quick, low-cost, thick-film, screen-printed biosensor is presented. The sensors utilize a platform sensor technology based on a three-electrode system with the working and counter electrode composed of 5% iridium deposited on Vulcan CX-72R carbon and a Ag/AgCl ink as the reference electrode. Using this sensor technology, two sensors were constructed for the detection of the key biomarkers adenosine deaminase and total bile acid. The sensor design is based on the immobilization of the enzymes 3α-hydroxysteriod dehydrogenase, for total bile acid, and xanthine oxidase and purine nucleoside phosphorylase, for adenosine deaminase. The enzymatically formed electro-active species H2O2 and NADH are measured using constant potential methods at a potential of +0.27V, versus the Ag/AgCl reference electrode. Construction of the sensors is described, and their testing in a variety of conditions including: temperature, enzyme level, substrate levels and combinations, and physiological testing fluids are reported. The testing results show that the sensors are suitable for detection of their corresponding biomarkers over the entire testing range with good linear beh (open full item for complete abstract)

Committee: Chung-Chiun Liu PhD (Advisor); Uziel Landau PhD (Committee Member); Harihara Baskaran PhD (Committee Member); Mitchell Drumm PhD (Committee Member) Subjects: Chemical Engineering