Characterization of Flexible Arrayed pH Sensor Based on Nickel Oxide Films

In this paper, nickel oxide (NiO) was used as a sensing film of flexible arrayed NiO pH sensor, and its average sensitivity could be improved by introducing oxygen gas in sputtering deposition process for NiO sensing film. It had the advantage, such as portability, disposability, low cost, high flexibility, miniaturization, long-term stability for basic solution, and high sensitivity (63 mV/pH) exhibited in the pH range from pH 1 to pH 13. Moreover, the characteristics of optimal NiO sensing film were investigated by using field emission scanning electron microscope. The non-ideal effects of flexible arrayed NiO pH sensor were investigated, such as drift and hysteresis effects. The drift rates for pH 1, pH 7, and pH 13 were -4 mV/hr, 3 mV/hr, and 1 mV/hr, respectively. Moreover, the hysteresis voltages were within 4 mV.