Development of a Portable Impedance Spectrometer

Author(s)

Lorenzo Antonio Buscaglia

• Document type: Master's Dissertation
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT)
• Defense date: 2022-02-21

Examining board members

Osvaldo Novais de Oliveira Junior; Carlos Frederico de Oliveira Graeff; Lucas Fugikawa Santos

• Advisor: Osvaldo Novais de Oliveira Junior

Abstract

Electrical impedance spectroscopy has been used extensively for sensing and biosensing due to the multiple electrical properties that can be interrogated through varying the frequency of the electrical excitation. An impedance spectroscopy system comprises three main units: signal processing, sensing and data analysis. This Masters Dissertation starts with a detailed revision of these units. We elaborate upon the methods to fabricate sensing units, including the choice of nanomaterials and biomolecules in controlled molecular architectures. Using arrays of sensing units, as electronic tongues, generates large amounts of data that require the use of data analysis methods, which we also revise and include examples of information visualization and machine learning techniques. The main focus of the revision, however, is on the signal processing unit, responsible for generating the excitation signal and performing the impedance readout. This focus is due to the high cost of the impedance spectrometers available in the market, which hampers integration of biosensing systems to be used in the field. A detailed description is given of the methods to develop a portable, fully integrated low-cost impedance analyzer that offers wide impedance magnitude, signal amplitude and frequency ranges. The device referred to as Simple-Z includes the integrated circuit AD5933 and peripheral circuits that allow for fine output amplitude regulation, flexible response amplification, sampling rate control, automatic calibration and external communication. We were able to fabricate a few units of Simple-Z with reproducible results, develop a graphical user interface and apply it successfully in sensing and biosensing, including for SARS-CoV-2 detection. The validity of Simple-Z was confirmed by comparing its results in some of the applications with those obtained with benchtop commercial impedance analyzers. Simple-Z can now be deployed in point-of-care diagnosis systems. Furthermore, owing to its low cost it can be fabricated with mass production to also be used in teaching labs for training students in electrical impedance spectroscopy. (AU)

• FAPESP's process: 19/00101-8 - Development of a portable impedance analyzer
• Grantee: Lorenzo Antonio Buscaglia
• Support Opportunities: Scholarships in Brazil - Master