Graduation Semester and Year
Fall 2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Electrical Engineering
Department
Electrical Engineering
First Advisor
Yijing Xie
Abstract
Electrochemical sensing systems have become essential tools in numerous fields due to their exceptional sensitivity, selectivity, and versatility. They play a critical role in modern research, industry, environmental monitoring, and healthcare applications. In environmental monitoring, these systems are utilized to detect pollutants, heavy metals, and toxic gases, enabling real-time monitoring and ensuring environmental protection. In the biomedical sector, electrochemical sensing systems are vital for diagnosing diseases, monitoring biomarkers, and transforming healthcare practices.
Affordable wearable electrochemical sensing devices are crucial for making healthcare more accessible and improving public health outcomes. These devices allow for continuous monitoring of physiological parameters, supporting early disease detection, personalized treatment, and remote patient care. By offering cost-effective solutions for health tracking and data collection, they empower individuals to take control of their health and well-being.
Among the various electrochemical sensing techniques, amperometry is the most widely used, as it measures current generated by the sensor's reaction, which is directly proportional to the analyte concentration. An emerging application of amperometry electrochemical biosensors is the detection of dopamine that serves as a critical biomarker for determining alcohol consumption levels in individuals.
In this research, a portable readout board accommodating variety of amperometric sensing applications was developed at the printed circuit board (PCB) level. The readout circuit functionalities were incorporated into the microcontroller unit, enabling the simultaneous connection of up to eight screen-printed electrodes. Firmware and a graphical user interface (GUI) were developed for data processing and analysis. Calibration of the system was achieved through amperometry experiments using a resistor array, resulting in an error rate of less than 0.5%. Subsequently, chemical experiments with varying concentrations of dopamine were conducted to validate the effectiveness of the readout board.
Furthermore, to reduce power consumption and minimize area, the readout circuit is implemented at the integrated circuit level using a 0.18μM CMOS process. The designed circuit incorporates a TIA, SHBUF, ADC, bias circuitry, and an on-chip clock generator. Since the sensor's output current ranges from 10 nA to 30 μA, a programmable gain feature is added to the TIA to accommodate this range. A two-step measurement method combined with a novel autozero scheme is developed to improve noise performance, offset, linearity, and accuracy. The design achieves an input-referred noise of 0.4 pArms, an input-referred offset of 137 nV, good linearity, and 2% accuracy over the specified input signal range. The chip is then connected to an SPE sensor, and chemical tests with varying dopamine concentrations are conducted to verify the circuit's capabilities. With a current consumption of 79 μA and a layout area of 1.64 mm², the design is well-suited for integration onto a flexible PCB, making it ideal for compact, wearable health monitoring devices that provide fast and accurate analyte concentration measurements.
Disciplines
VLSI and Circuits, Embedded and Hardware Systems
License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Recommended Citation
Chilukuri, Manu, "A LOW-NOISE, LOW-POWER CMOS READOUT IC FOR AMPEROMETRIC ELECTROCHEMICAL SENSING SYSTEM" (2024). Electrical Engineering Dissertations. 402.
https://mavmatrix.uta.edu/electricaleng_dissertations/402