Flexible pH sensors based on OECTs with a BTB dye-embedded ion-gel gate dielectric

With the advantages of miniaturization, simple device structure, and fast response, organic electrochemical transistors (OECTs) have become an emerging platform for developing wearable pH sensors for real-time human health monitoring. However, the application of devices is limited because they use water electrolytes. This paper proposed a feasible pH-sensitive OECT with a flexible BTB dye-embedded ion-gel dielectric layer. The real-time H+ detection performances of the devices, the effects of the BTB content in the ion-gel layer and gate voltages on the pH sensing capability, as well as the property–microstructure relationship of the ion-gel were investigated. The experimental results showed that the pH-sensitive OECT integrated with a 15 wt% BTB ion-gel layer exhibited outstanding H+ ion sensitivity and linear response properties at a gate voltage of −0.4 V. The pH-sensitive ion-gel modified OECT presented here provides a novel strategy for developing wearable pH sensors with high real-time monitoring characteristics.