Toward Wearable VOC Sensors—Electrochemical and Thin-Film Copper Phthalocyanine Based Sensors

Owing to the recent advancements in artificial intelligence and machine learning (AI/ML), the application of electronic noses (e-Noses) is expanding into the food industry, medicine, and many more. However, designing more reliable and sensitive e-Nose devices depends on the sensing technologies. Currently, most of the gas and volatile organic compound (VOC) sensors use a thin film of metal oxide (MOX). Although MOX sensors are relatively stable, they are extremely power-hungry and are not suitable for many applications such as wearable sensors. As a low-power alternative to MOX, in this work, we have focused on the application of organometallic compounds, particularly Copper Phthalocyanine (CuPc). Two different types of VOC sensors have been studied using CuPc. In an electrochemical design, CuPc was tested against various VOCs showing a high selectivity to formic acid. The process is explained through the protonation mechanism. However, due to the contamination of the electrolyte, the electrochemical design has a shorter lifetime. In the second design, a thin film of CuPc was tested in the form of a chemiresistor using an extremely low-power source (20 nA). The results show different degrees of responses to various VOCs with higher stability than the electrochemical devices. Using low-power sensors such as CuPc is promising toward further development of wearable e-Nose devices in the future.