To explore the pH response of the sensors, they were fabricated using an optimal L/W ratio of 4. Samples with pH values of 3, 5, 7, 9, and 10 were prepared and individually incubated with the sensors. The initial resistances were recorded after the wet channel was incubated with pH7 as a neutral point before incubating with other samples. The sensor was then dried for 6 hours in ambient to recover its dry R before incubating with acidic or basic pH samples. The response was calculated as the wet resistance change.