The effect of the microheater’s topology on the performance of carbyne-based ethanol sensors

In the realm of healthcare, gas sensors are utilized in medical devices and monitoring systems to measure physiological gases, such as oxygen and carbon dioxide, in patients’ breath and blood. They also find applications in diagnostic equipment for detecting volatile organic compounds associated with various medical conditions, thereby aiding in disease diagnosis and management. As a gas-sensitive layer, carbyne offers unique properties that can significantly enhance sensor performance when volatile organic vapors like ethanol are detected. To ensure the reversibility of the response characteristics, the carbyne gas sensors must be equipped with a microheater. Surface acoustic wave (SAW) gas sensors have emerged as a promising technology for detecting and analyzing trace amounts of various gases. Lithium niobate (LiNbO₃) substrates were used to make the SAW structures. Platinum film with a thickness of 280 nm was vacuum-sputtered, and three topologies were fabricated with photolithography. The geometry of the interdigitated electrodes (IDTs) was as follows: width (in the range 300 - 450 µm for the different topologies), length (1.2 mm for all samples), and number of wires (1, 3 and 5), in order to provide the maximal heating temperature of 80 ºC, taking into account that the adsorbed organic analytes are volatile. The meander microheater likely provides a more uniform temperature distribution across the sensing area, contributing to higher accuracy. The meander microheater exhibits more controlled and predictable heat transfer dynamics, leading to a more consistent and accurate response to changes in gas concentration. Meanwhile, the spot high-density rectangular filled micro-heater probably introduces unpredictable or non-linear heat transfer behavior, impacting accuracy to a greater extent. The small meander-shaped microheater exhibits slower response times and reduced sensitivity to changes in temperature. Its thermal design delays the heating and cooling process, impacting the sensor's ability to detect rapid changes in gas concentration, which can be the reason for its lower sensitivity.