Potentiometric MgO Film pH Sensor Measurement Analysis and Integrated Flexible Printed Circuit Board

In recent years, research in the field of sensors has been rapidly advancing. As a result, this study proposes a pH sensor based on a magnesium oxide (MgO) thin film. The MgO sensing layer of the pH sensor was deposited onto the electroless nickel immersion gold (ENIG) electrode using a radio frequency (RF) sputtering system, where the ENIG electrode is integrated as the working electrode and reference electrode on a Flexible Printed Circuit Board (FPCB). FPCB offers advantages such as flexibility, acid resistance, heat resistance, and low cost. Furthermore, the performance of the pH sensor is enhanced by modifying the sensing layer with Nafion and (3-Aminopropyl)triethoxysilane (APTES). This study utilized the potentiometric method to measure and analyze the performance of the pH sensor, and the measurement range of the pH sensor is from pH 3 to pH 11 with an average sensitivity of 46.48 mV/pH and linearity can reach 0.996. In terms of material analysis, this research utilizes atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX) to analyze the surface morphology and elemental composition of the sensing layer to verify MgO film.