Functional aqueous-based polyaniline inkjet inks for fully printed high-performance pH-sensitive electrodes

pH sensors are extremely useful in various applications such as health, food and environmental monitoring. Due to this fact the development of planar, low-cost and high-performance pH sensors that can be fabricated in large scale are highly appreciated. In this work we fabricated a polyaniline-based potentiometric pH sensor using two printing techniques. The working electrode was fabricated by printing a carbon ink layer onto Valox® by screen printing and subsequently modifying its active area by printing with a polyaniline ink by inkjet printing. Different water-based formulations of the polyaniline ink using acrylic dispersions as binders were tested in order to optimize printability, adhesion, rub resistance and functionality of the printed electrodes. These electrodes showed an outstanding sensitivity (up to 69.1 mV/pH), slightly higher than polyaniline electrodes fabricated by electropolymerization onto carbon paste electrodes and also comparable to glass electrodes. Moreover, their response to synthetic sweat was analyzed, demonstrating that there are suitable for application in wearable technology.