Investigation of Thick-Film Polyaniline-Based Conductimetric pH Sensors for Medical Applications

This paper reports on the development and testing of a polyaniline-based conductimetric pH sensor. The sensor functions successfully in both the pH range for stomach acid (pH1.0-pH2.0) and for human blood (pH7.0-pH8.0). Experiments were performed by exposing the sensors to buffer solutions with pH values in the ranges identified. The sensors demonstrated reproducible and repeatable results with little hysteresis being recorded between experiments, along with a response time of approximately 1 min in acidic solutions and 2 min in buffers with pH values in the blood pH range. In the case of measurements made in the blood pH range, a novel memory effect was observed, which corresponds to a permanent ldquorecordingrdquo of the pH measurement into the electrical characteristics of the film. This memory effect only applies to measurements made in alkaline pH ranges and is due to the deprotonation of the polyaniline material in the sensing layer. The sensor reported in this paper has the potential to be a more economically viable option when compared to other approaches being used for commercial applications.