Development and characterization of a multiplexer for impedance measurements of sensing units of an electronic tongue.

• Grant number: 22/16814-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2023
• End date: March 31, 2024
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal Investigator: Varlei Rodrigues
• Grantee: Pedro Victor Abreu
• Host Institution: Instituto de Física Gleb Wataghin (IFGW). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Many challenges facing society today are related to our ability to detect molecular and biological species. Examples are diagnosing viruses such as SARS-CoV-2 and detecting pollutants, pesticides, or fertilizers in water or soil. In this context, a promising approach is using an impedimetric electronic tongue that uses thin layers of polymers as transducer elements. This approach allows obtaining different functionalities and capabilities to meet a wide range of applications. Usually, electrical impedance measurements are performed as a function of frequency in the set of sensing units that make up the device using an impedance analyzer. Typically, the electronic tongue we use is composed of four sensing units, and the impedance measurements for each analyte are performed in triplicate. General problems in this type of sensing are control and reproducibility if there is a need to change a sensor unit, even considering that some of these systems operate with relatively low values of the capacitive impedance component (on the order of a few pF). Therefore, any change in the geometry of the electrodes or electrical connections ends up contributing to the final measured value, which does not necessarily originate from the analytes being measured. In this sense, an impedimetric device was developed in our research group for fast measurements in a microfluidic electronic tongue, with analog multiplexing of the sensing units, avoiding external interferences as much as possible during data acquisition. In this device, the switching between sensing units is performed by relays because they have lower parasitic capacitance values. In our tests, we have not observed any effect that would compromise the impedance measurements or the discrimination of the analytes. However, relays are devices that require extra power for their correct operation. When activated, they generate a transient during which measurements cannot be performed, which can damage the impedance analyzer. With due care and characterization, these problems could be avoided using solid-state switches to avoid parasitic capacitances arising from the semiconductor junctions in the architecture of solid-state switches. Our objective is to study the automated measurement system we currently use in the electronic tongue, developed in our group, replacing the relays with solid-state switches integrated into the commercial component CD4066. The CD4066B is a quadruple bilateral switcher (4 bilateral independent keys) based on CMOS keys intended to transmit or multiplex analog or digital signals. The project aims to verify the influence of solid-state switches on the multiplexing of signals from the impedimetric electronic tongue that we are working on, testing the new system in measurements with analytes that confer the basic tastes of sweet, salty, sour, and bitter. The project will contribute to the training of the candidate for the scientific initiation scholarship due to its character of scientific instrumentation, in particular by the assembly and characterization of the sensorial units, the electronics in the multiplexing of signals during the acquisition of data, and the treatment of the data for measurements comparative. Finally, we highlight the multidisciplinarity of the project, enriching the student's education in engineering and chemistry.