The design of sensor interface circuits for electrochemical impedance spectroscopy

Wang, Zhongzheng

The design of sensor interface circuits for electrochemical impedance spectroscopy

dc.contributor.advisor	O'Hare, Daniel
dc.contributor.advisor	O'Connell, Ivan
dc.contributor.advisor	O'Riordan, Alan
dc.contributor.author	Wang, Zhongzheng	en
dc.contributor.funder	Science Foundation Ireland	en
dc.contributor.funder	Enterprise Ireland	en
dc.date.accessioned	2026-01-20T10:33:44Z
dc.date.available	2026-01-20T10:33:44Z
dc.date.issued	2025
dc.date.submitted	2025
dc.description.abstract	Electrochemical Impedance Spectroscopy (EIS) has gained attention in biomedical applications—such as DNA, antigen–antibody, and virus detection—due to its label-free nature and high sensitivity. The development of EIS circuits with low power consumption, reduced complexity, and faster measurement times has been a particularly active area of research. However, the lengthy measurement times and the complexity of traditional EIS systems limit their adoption in real-time, portable, and low-cost point-of-care (PoC) applications. In addition, conventional RC-based equivalent AC impedance electrochemical sensor models, namely, models consisting of a resistor and a capacitor in parallel structure, cannot accurately reflect realistic sensor behavior; therefore, they do not support essential simulation analyses (e.g., transient, DC sweep, or DC operating point) and fail to facilitate accurate EIS sensor interface design. To address these challenges, this research introduces a dynamic model of an Ultra-Microband (UMB) sensor, implemented in Verilog-A, and proposes a fast, high-accuracy methodology for conducting EIS based on the Fast Fourier Transform (FFT). This approach aims to fulfill the requirements of portable, real-time, label-free EIS biomedical detection. The work begins by reviewing fundamental electrochemical principles and examining the electrode–electrolyte interface, represented by the Randles model. A static three-electrode small-signal impedance model of the UMB sensor is then analyzed to illustrate its application in small-signal scenarios such as EIS, thereby bridging the gap between electrochemists and electronic engineers. Subsequently, a dynamic model of the UMB sensor is developed and implemented in Verilog-A, enabling comprehensive simulations—such as AC stability, AC sweep, transient, and DC sweep—within Electronic Design Automation (EDA) tools like Cadence Spectre. This model thus captures more realistic sensor behavior and enhances design accuracy and robustness. Finally, a square-wave-based EIS approach is proposed by identifying the conditions under which the UMB sensor behaves as a Linear Time-Invariant (LTI) system. A circuit comprising a control amplifier and a Trans-Impedance Amplifier (TIA) is designed and fabricated in a 65 nm CMOS process to validate its feasibility for on-chip integration. The proposed square-wave EIS shortens the measurement time by 91.7% across frequencies ranging from 0.5 Hz to 500 Hz, with only a 2.73% average Mean Absolute Percentage Error (MAPE) compared to a commercial instrument (AutoLab). Tests using five premodified electrodes with four different concentrations of Ferrocene Carboxylic Acid (FcCOOH) demonstrate that this method is suitable for portable, real-time EIS biomedical detection and related applications.	en
dc.description.status	Not peer reviewed	en
dc.description.version	Accepted Version	en
dc.format.mimetype	application/pdf	en
dc.identifier.citation	Wang, Z. 2025. The design of sensor interface circuits for electrochemical impedance spectroscopy. PhD Thesis, University College Cork.
dc.identifier.endpage	141
dc.identifier.uri	https://hdl.handle.net/10468/18412
dc.language.iso	en	en
dc.publisher	University College Cork	en
dc.relation.project	info:eu-repo/grantAgreement/SFI/Research Centres Programme/16/RC/3835/IE/VistaMilk Centre/	en
dc.rights	© 2025, Zhongzheng Wang.
dc.rights.uri	https://creativecommons.org/licenses/by-nc/4.0/
dc.subject	UMB
dc.subject	CV
dc.subject	EIS
dc.subject	FFT
dc.subject	Verilog-A
dc.subject	Sensor modelling
dc.title	The design of sensor interface circuits for electrochemical impedance spectroscopy
dc.type	Doctoral thesis	en
dc.type.qualificationlevel	Doctoral	en
dc.type.qualificationname	PhD - Doctor of Philosophy	en