Indium Tin Oxide Films Based pH Concentration Sensor Fabrication and Verification Using Pulsed UV Laser Patterning Technology

A novel pH value detection method was developed in this paper. A 10 μL droplet prepared by buffer solution (pH = 1.2 to pH = 10) was injected to the sensing area (i.e. designed interdigitated ITO electrode), and the resistance variation of the electrode was recorded to build up the model of pH concentration detection. The result indicated that the interdigitated electrode pattern with a line width of 500 µm and a line pitch of 100 µm was the most sensitive under various pH conditions. In addition, for the acid solution and alkali solution, when the interdigitated electrode pattern with a line width of 100 µm and a line pitch of 500 µm was more sensitive in the acid environment, whereas the interdigitated electrode pattern with a line width of 500 µm and a line pitch of 100 µm can be applied in the alkaline environment due to its great sensitivity. During the pH value monitoring, the response time of resistance changing was below 3 seconds to reach the steady-state resistance in all various pH conditions, and the correlation coefficient was over 0.9 validated by a quadratic regression in both acid and alkaline sensing verification.