Temperature Sensors Manufactured from Edible Materials Intended for Oral Cavity Operation

Abstract

Following the circular economy concept, all areas of science, including electronics, require individual approach. The green electronics approach implies processing natural based materials for development of electronic components even for single use, so that waste does not exist. This paper describes the production of thermistors from 3 different types of edible materials, their testing in laboratory conditions, as well as the application for measuring the temperature in the human oral cavity. To make the thermistor, three types of natural materials were used (carrageenan, polyvinyl alcohol and apple pomace-based). After fabrication, materials were poured into molds. Aluminium foil contacts were placed so that the electrical characterization of the materials could be performed. Several parameters were measured: resistance (R), impedance (Z) and the phase angle (θ) as a function of frequency. In order to determine whether the thermistors have a positive or negative temperature coefficient and to determine their sensitivity, measurements were conducted at three different temperatures: 25 ℃ (room temperature), 37 ℃ (human body temperature), and 50 ℃. The thermistors demonstrated negative temperature coefficient behaviour. Additionally, it was demonstrated that the apple pomace-based thermistor can successfully measure healthy volunteer's temperature.