Miniaturization, integration and intelligence are the developing trends for sensor,especially for biosensors. The development of microelectronics technology is a powerful engine to full this objective. It is well known that the microelectronic fabrication process in proven technology for fabrication of integrated circuits. Advances in the field of micro-electronics and micro-mechanical devices combined with medical science have led to the development of numerous analytical devices in monitoring of a wide range of analytes. The unique properties of nanoscale materials offer excellent prospects for interfacing biological recognition events with electronic signal transduction and for designing a new generation of bio-electronic devices exhibiting novel functions. Biosensor development has the potential to meet the need for rapid, sensitive, and specic detection of pathogenic bacteria from natural sources. This work focuses on development of one such electrochemical biosensor platform and discusses dierent aspects related to the design of biosensor and biodetection systems. A new transducer for bio sensor applications based on 3-dimensional, comb structured interdigitated electrode arrays was chosen mainly for two reasons. Firstly, this geometry allows the monitoring of both resistivity and dielectric constant of solution, thus making interdigitated electrodes more versatile tools than other kind of transducers. Second, they present short electric eld penetration depths, which make them more sensitive to changes occurring close to their surface (20 - 100 nm above the surface). This fact enables the monitoring of local changes in the vicinity of interest. Binding of analyte molecules to the chemically modied transducer surface induces important changes in the conductivity between the electrodes. Interdigitated electrodes have been employed to detect the presence of Anti-Transglutaminase (TG) antibodies, that are established biomarkers for Celiac disease which is due to gluten allergy. The biosensor was optimized for specific and sensitive detection of this biomarker. The sensor showed a sensitivity down to picomolar(pM) concentration of the biomarker. Gold nanoparticles were further used for signal enhancement so as to bring the sensor performance closer to Enzyme linked immunosorbant assay (ELISA).

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On-site sensing systems provide fast and timely information about a myriad of applications ranging from chemical and biological to physical phenomena in the environment or the human body. Such systems are embedded in our daily life for detecting pollutants, monitoring health, and diagnosing diseases. Especially in the field of health care, the development of portable and affordable diagnosing systems, also known as point-of-care (PoC) devices, is a major challenge. Moreover, to this day, systems for therapeutic drug monitoring (TDM) have remained bulky and highly expensive, mostly due to the need for exceptionally precise, rapid, and highly accurate real-time on-site measurements. This dissertation focuses on the design, development, and implementation of miniaturized PoC devices for achieving high sensitivity, selectivity, and reliability through a combination of hardware and software strategies at the edge. The first part of the dissertation introduces the design of single and multi-channel electrochemical readout platforms with a high voltage range, fast scan rates, and with nano-ampere resolution, covering a broad range of electrochemical excitation techniques. These platforms were paired with electrochemical-based sensors to detect SARS‑CoV‑2, bisphenol A, and ascorbic acid. The low power feature of the proposed platforms is demonstrated by powering the complete detection system with energy harvested from natural and artificial ambient light. The second part of the dissertation introduces the design and development of a miniaturized wearable device with a pico-ampere resolution, high-speed electrochemical frequency interface, and highly stable sensing circuitry. A complete in-vivo system is demonstrated for long-term (>4 hours) measurement, wherein molecules are detected and monitored directly from a probe inserted in the subcutaneous abdomen region of a Sprague-Dawley rat. A solution for sensor drift due to biofouling and interference is demonstrated thought to the integration with real-time processing software. Furthermore, integrating the aforementioned platforms with highly reduced dense neural network models is demonstrated to increase the robustness of the sensors, allowing the detection of contaminants in complex samples, improving the sensor selectivity, and providing timely diagnoses in-situ.

Chlorine is used as a powerful disinfectant in water-related industries and in the food industry to remove bacteria and other harmful contaminants. We present a solution-based fabrication process for a biodegradable electrochemical free chlorine sensor using asparagine that is functionalized onto graphene oxide (GO). An ink solution of the GO functionalized with asparagine was fabricated then deposited onto a screen-printed carbon electrode (SPCE) using a spin-coater. The sensor showed high a sensitivity of 0.30 μA ppm−1 over a linear range of 0 to 8 ppm with a hysteresis-limited resolution of 0.2 ppm, very high selectivity in the presence of commonly interfering ions, and an operating voltage well below the reduction potential of dissolved oxygen. The sensor response time to achieve a steady state was 50 s, and it showed little change in its drift response over 16 h and over a temperature range of 10 to 45 °C. From the development of the free chlorine sensor, over 9000 datapoints were collected and used for training a neural network model to quantify and characterize factors affecting the free chlorine sensor performance. A readout system was designed with a printed circuit board and an android app to simplify free chlorine sensing for an end user. / Thesis / Master of Applied Science (MASc) / Free chlorine is used to disinfectant sources of water, and eliminate pathogens. The World Health Organization (WHO) maintains strict amounts of free chlorine in water due to its widespread usage owed to its low cost and persistence in water systems. Too little, and it will not be an effective disinfectant, and too much and the high consumption of free chlorine increases the risk cancer or the formation of hazardous chemicals. Recently, free chlorine sensors that measure an electrical response proportional to the amount of free chlorine are gaining interest for fast, accurate, and repeatable measurements. This thesis focuses on the design, fabrication, and evaluation of these sensors made using biodegradable materials in a solution-based fabrication processes with the aim of working towards large-scale fabrication of a printable ink. First, we review the results achieved by the sensors within recent literature. Second, we present the design of a sensor that aims to achieve environmentally friendly goals and maintain competitive performance characteristics. The, the sensor is tested under various conditions with its performance quantified under different conditions. Third, the sensor is characterized using a neural network to measure its performance and identify sources of improvement for future designs. Finally, we incorporate the sensor with an android app to measure free chlorine in remote water systems.

Ouyang, Mengxing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 83-88). / Abstracts in English and Chinese. / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Background and Motivation --- p.1 / Chapter 1.2 --- Objectives --- p.2 / Chapter 1.3 --- Contributions --- p.3 / Chapter 1.4 --- Organization of the Dissertation --- p.3 / Chapter 2. --- CNTs and Their Application as Sensors --- p.5 / Chapter 2.1 --- Introduction to CNTs --- p.5 / Chapter 2.2 --- CNTs Based Sensors --- p.8 / Chapter 3. --- F-CNTs Based Ethanol Sensors --- p.10 / Chapter 3.1 --- Introduction --- p.10 / Chapter 3.1.1 --- Carbon Nanotube Alcohol Sensors --- p.11 / Chapter 3.1.2 --- CNTs Sensor Configuration --- p.12 / Chapter 3.1.3 --- Activation of CNTs Sensor --- p.13 / Chapter 3.1.4 --- Functionalization of CNTs --- p.14 / Chapter 3.2 --- Fabrication of F-CNTs Based Ethanol Sensors --- p.16 / Chapter 3.2.1. --- Fabrication of f-CNTs --- p.16 / Chapter 3.2.2. --- Fabrication of Sensing Elements by DEP Manipulation --- p.17 / Chapter 3.2.3. --- Experimental Setup --- p.19 / Chapter 3.2.4. --- Mechanism of Ethanol Sensor --- p.20 / Chapter 3.3 --- Characterization of F-CNTs Based Ethanol Sensors --- p.21 / Chapter 3.3.1. --- I-V Characteristics --- p.21 / Chapter 3.3.2. --- Thermal Sensitivity --- p.22 / Chapter 3.3.3. --- Stability --- p.23 / Chapter 3.3.4. --- FFT and Spectral Analysis --- p.23 / Chapter 3.4 --- Performance of F-CNTs Based Ethanol Sensors --- p.26 / Chapter 3.4.1. --- Typical Response --- p.26 / Chapter 3.4.2. --- Selectivity --- p.27 / Chapter 3.4.3. --- Towards Low Concentration --- p.28 / Chapter 3.4.4. --- Towards Realistic application --- p.29 / Chapter 3.5 --- Constant Power Configuration --- p.32 / Chapter 3.5.1. --- Constant Power Circuit for Ethanol Detection --- p.32 / Chapter 3.5.2. --- Sensor Response versus Power --- p.35 / Chapter 3.5.3. --- Responsivity --- p.37 / Chapter 3.5.4. --- Noise --- p.38 / Chapter 3.5.5. --- Sensitivity --- p.39 / Chapter 3.5.6. --- Dynamic Response --- p.41 / Chapter 3.6 --- Comparison between F-MWNTs and MWNTs --- p.43 / Chapter 3.6.1. --- I-V Characteristics --- p.43 / Chapter 3.6.2. --- Cycling Response --- p.44 / Chapter 3.6.3. --- Dynamic Response --- p.46 / Chapter 3.6.4. --- Sensor Performance under Different Power --- p.48 / Chapter 3.7 --- Summary --- p.53 / Chapter 4. --- EG-CNTs Based Flow Sensors --- p.55 / Chapter 4.1 --- Introduction to CNTs Flow Sensors --- p.55 / Chapter 4.2 --- EG-CNTs and Their Applications --- p.56 / Chapter 4.2.1 --- Intro to EG-CNTs Sensor --- p.56 / Chapter 4.2.2 --- Fabrication of EG-CNTs Sensor --- p.57 / Chapter 4.2.3 --- Experimental Characterization --- p.59 / Chapter 4.2.3.1. --- I-V Characteristics --- p.59 / Chapter 4.2.3.2. --- Thermal Sensitivity --- p.61 / Chapter 4.2.3.3. --- Humidity responsivity --- p.63 / Chapter 4.2.3.4. --- Stability --- p.65 / Chapter 4.2.3.5. --- Hysteresis --- p.66 / Chapter 4.2.4 --- Summary --- p.68 / Chapter 4.3 --- Fabrication of EG-CNTs Flow Sensor --- p.70 / Chapter 4.3.1. --- Fabrication Procedure --- p.70 / Chapter 4.3.2 --- Experimental Setup --- p.73 / Chapter 4.4 --- Characterization of EG-CNTs Flow Sensor --- p.74 / Chapter 4.4.1. --- Typical Response --- p.74 / Chapter 4.4.2. --- Power Consumption --- p.75 / Chapter 4.4.3. --- Repeatability --- p.77 / Chapter 4.4.4. --- Flow Sensitivity --- p.78 / Chapter 4.5 --- Summary --- p.79 / Chapter 5. --- Conclusion --- p.80 / Chapter 6. --- Bibliography --- p.83

Submitted in fulfillment of the requirements for the Degree of Master of Applied Science in Chemistry, Durban University of Technology, Durban, South Africa, 2016. / This study involves the development of a sensitive electrochemical biosensor for the determination of capsaicin extracted from chilli pepper fruit, based on a novel signal amplification strategy. The study therefore, seeks to provide a sensitive electro-analytical technique to be used for the determination of capsaicin in food and spicy products. Electrochemical measurements using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) modes were utilized in order to understand the redox mechanism of capsaicin and to test the performance of the developed biosensor supported with computational techniques. In this work two different enzymes, Phenylalanine ammonia lyase (PAL) and Glucose oxidase (GOx) were used for electrode modifications respectively. For this purpose three different types of working electrodes namely: glassy carbon electrode (GCE), platinum electrode (Pt-E) and gold electrode (Au-E) were used and their performances were compared. For the first time, the three electrodes were modified with PAL and GOx enzymes on multiwalled carbon nanotubes used in this study and characterized by attenuated total reflectance infrared spectroscopy, transmittance electron microscopy and thermo-gravimetric analysis supported by computational methods. The comparison of the results obtained from the bare and modified platinum electrodes revealed the sensitivity of the developed biosensor with modified electrode having high sensitivity of 0.1863 µg.L-1 and electron transfer rate constant (ks) of 3.02 s-1. To understand the redox mechanism completely, adsorption and ligand-enzyme docking simulations were carried out. Docking studies revealed that capsaicin formed hydrogen bonds with Glutamates (GLU355, GLU541, GLU586), Arginine (ARG) and other amino acids of the hydrophobic channel of the binding sites which facilitated the redox reaction for detection of capsaicin. These results confirm that the PAL enzyme facilitated the electron transfer from the capsaicin ligand, hence improving the biosensing response. Our results suggest potential applications of this methodology for the determination of capsaicin in the food industry. / M

M.Tech. (Chemistry) / Please read abstract in the full-text document

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Ceramic and Materials Science and Engineering." Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 149-157). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 149-157). Also available on the Internet.